iris android-app: header-duplicate investigation, ime-inset fix for keyboard confirmation

Two follow-ups after the keyboard/dp/header pass, both requested against
the P0 box:

(a) The header row rendering a second time inside the transcript area
after a keyboard-triggered resize: reproduced reliably (tap the composer,
screenshot after the keyboard opens). Ruled out one concrete hypothesis --
on_insets_changed rebuilding top_bar on every ime_bottom change, unrelated
to the header's own status-bar padding -- with a guard (last_top_pad) that
reproduced the identical duplicate afterward, so repeated rebuilding is
not the cause. Kept the guard as a real (if insufficient) fix for needless
rebuilds. Not root-caused: Span's two-phase provisional/real draw and the
redraw_all-vs-redraw_updates split are the two live suspects, but pinning
which one (or something else) produces the duplicate needs instrumenting
draw_inner directly or the phone. Full writeup in RUST.md's P0 box.

(b) Why on_insets_changed's ime_bottom never confirmed the keyboard being
shown, on either the auto-diagnostics or the new bench keyboard phase:
MainActivity.java uses windowSoftInputMode="adjustResize", under which
WindowInsets.Type.ime()'s own inset amount is defined to read zero (the
window already resized to avoid the overlap that inset would describe) --
the same trap AGENTS.md already names for the Compose side. Fixed to read
insets.isVisible(ime()) instead, a boolean unaffected by resize-vs-pan.
This alone did not make the callback re-fire on this emulator, which
still shows no insets callback after the initial one at attach -- named
but unconfirmed hypothesis: a non-edge-to-edge Activity may not get insets
redelivered for a pure IME toggle handled via resize, needing an edge-to-
edge opt-in this pass did not attempt given the risk to adjustResize's
own behavior.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

.claude/skills/ai-app-rigs/SKILL.md

@@ -0,0 +1,244 @@
+---
+name: ai-app-rigs
+description: ai-app's test rigs, harness scripts and reference measurements - ui-sandbox.sh, debug-transcript.sh, transcript-bench.sh, stream-bench.sh, trace-draw.sh, the /usage fixture vocabulary, the fake CLI, the rule that no UI-driving script may tap a coordinate, how to test llama.cpp and ssh on this machine, how importing behaves, and the scroll/stream/explorer numbers not worth re-measuring. Read before running or writing a benchmark, driving the app's UI from a script, exercising the session lifecycle, testing a llama or remote session, or touching the import screen.
+---
+
+# ai-app: rigs, harnesses and measurements
+
+Moved out of `AGENTS.md` on 2026-09-04 so it is read when it is relevant
+rather than sent with every request in this repo -- it was 12 KB of the 35 KB
+that file cost on every one. Unchanged in the move, and still the only copy.
+
+## The rigs
+
+Each exists because something was invisible without it.
+
+- **`app/ui-sandbox.sh`** — a second `ai-server` with its own `$HOME`, config
+  and data directory, holding eight invented Claude Code transcripts and a
+  `claude` that is two lines of shell. **That isolation is the point**: the
+  import screen lists whatever is in `~/.claude/projects`, which in this VM is
+  real agent transcripts, so exercising *delete* against the ordinary server
+  deletes somebody's conversation and exercising *import* starts a real
+  `--resume` on the owner's account.
+  Its port and root derive from the checkout's name, so two checkouts'
+  sandboxes cannot reach each other, and its token is generated once into
+  `~/.config/ai-app/sandbox-token` and carried across restarts along with any
+  the enrolment flow appended — so the emulator app is enrolled **once** (the
+  start banner prints the command) and stays enrolled. It shares the real TLS
+  certificates, because the installed APK pins that CA.
+  Driving verbs, so none of this is re-derived per session:
+  `./ui-sandbox.sh spawn [title]` (an echo session, prints its id),
+  `./ui-sandbox.sh send SID text|@file`, and
+  `./ui-sandbox.sh api /path [curl args]`.
+  `./ui-sandbox.sh keep` restarts the server without wiping the sessions and
+  enrolment already there — for when the fixture under test was expensive to
+  build; plain `start` wipes them, which is right for the list-screen
+  fixtures and wrong for that.
+  It passes `--delay` by default, and `AI_SANDBOX_BIG_MB` puts one large
+  transcript among the small ones while `AI_SANDBOX_SPAWN_DELAY` makes the
+  fake CLI slow to start. Both exist because operations that finish in
+  milliseconds have states on the way that nothing can observe, and an
+  unobservable state is one where broken and working look identical.
+  It also builds a fixture tree at the sandbox home's `~/files` for the
+  explorer, holding the states otherwise only reachable by finding a real
+  machine in one: an empty directory, a name with a tab and one with an
+  apostrophe, a binary file, one over `FILE_LIMIT`, one `chmod 000`, a
+  symlink to a directory and a broken one, a source file per language, and
+  the three sizes the limits were measured against (`edit-32k.rs`,
+  `edit-128k.rs`, `big-source.rs`). Point a session at it with
+  `./ui-sandbox.sh api /sessions/<id>/cwd -X POST -H 'content-type: application/json' -d '{"cwd":"~/files"}'`.
+  The explorer's 409 is produced by editing the file on the machine
+  (`printf … > file`) between pressing the pencil and pressing save.
+- **`app/debug-transcript.sh`** — a real conversation on the emulator. The
+  echo driver is the right rig for most things and the wrong one for anything
+  whose cost scales with what was actually written: a real reply is longer,
+  is real markdown, and carries tool calls whose input and output are
+  kilobytes. Two faults were invisible until a real transcript was loaded — a
+  page of history landing mid-fling threw the reader back to the newest end,
+  and parsing one real reply took 51ms against 4.6ms for a synthetic one.
+  `-b` takes the biggest conversation on the machine rather than the newest,
+  which is what a scrolling test wants; `--stop` takes it down.
+  It copies the transcript into `/tmp` and gives the server a `HOME` of its
+  own, so the import can only see the copy — importing spawns `claude
+  --resume`, and against the real file that is a second CLI writing to a
+  conversation somebody may still be in. **A transcript never goes in this
+  repository**: they hold whatever was said, read and written in that
+  session, and `~/repos` is shared with the host besides.
+- **`/usage` in an echo session puts up an invented meter**, which is how the
+  rate-limit screens' states are reached without spending quota: `/usage 42`,
+  `/usage 95 20` (minutes left), `/usage 42 never` (the between-blocks window
+  with no reset time), `/usage 42 unreadable`, `/usage notloggedin`,
+  `/usage unreachable`, `/usage failed`, `/usage off`. The vocabulary is
+  `usage::Fixture`'s, since those are its states. With none set an echo
+  session meters nothing, which is the ordinary case and draws no bar.
+- **A fake CLI exercises the process lifecycle without a token.** Point a
+  `claude_cli` provider's `command` at a two-line script — `#!/bin/sh` and
+  `cat > /dev/null` — and it behaves the way the lifecycle code cares about:
+  it holds the fifo open, records a real pid, writes nothing, and dies on a
+  signal. So adopt, stop, restart and start are all drivable without a real
+  `--resume` and without spending a turn on somebody's account. Reach for
+  this when what is under test is *whether a process is running*, and for
+  `debug-transcript.sh` when it is *what the transcript draws*.
+- **`app/transcript-bench.sh`** is the standard scroll measurement: it opens
+  the first session (or `-k` keeps the current screen), scrolls a fixed
+  gesture loop, and prints the app's render report — the same one the in-app
+  copy button produces, whose `on screen:` line names what the viewport was
+  holding. Compare two runs with the same gestures; the emulator's absolute
+  frame times transfer nothing, the report's accounting does. Run it either
+  side of any change under `Markdown*.kt`, `Transcript*.kt` or
+  `SessionScreen.kt`'s list, and put the report in the commit. The numbers
+  that move first are the worst `record: one block`, the reparse mean while
+  streaming, and the draw phase's accounting line.
+- **`app/stream-bench.sh [-k] FILE`** is that measurement for a reply still
+  arriving. It taps "Jump to latest" so the list is pinned to the newest end,
+  resets the report, sends FILE, waits for the transcript to stop growing,
+  and prints. Both of those are corrections to a first version that measured
+  nothing: a transcript parked further back never redraws while a reply
+  streams into it, and a session is idle at *both* ends of a turn, so polling
+  for idle answers before the turn has started.
+- **`app/trace-draw.sh`** names what a scrolling frame spends inside the
+  framework, from `atrace` text output with no trace processor needed. It is
+  how the cost of a layout node per link was attributed to the framework
+  rather than guessed at.
+
+### Driving the UI
+
+**No script that drives this app's UI presses a coordinate.** Every control
+is found by the name it already carries for assistive technology —
+`ui-trace record --do "tap 'Session settings'"` — which resolves the label
+against the screen at the moment of the gesture and fails the whole run when
+it is not there. `app/bench-lib.sh` is what the bench scripts share for it. A
+coordinate is a position measured once by hand, and anything that moves the
+control makes the tap land on whatever now sits there — the bench then
+reports a number that was never measured, which reads exactly like a result.
+Both bench scripts pressed the render report at `tap 723 205` until that
+button moved into the session settings dialog on 2026-09-03. The check that
+none has crept back:
+
+    grep -n "tap [0-9]" app/*.sh
+
+Swipes are still coordinates, deliberately: a gesture across a scrolling area
+is a distance rather than a control.
+
+**Two traps in the emulator bench loop**, each of which cost a run.
+`adb shell pm clear` removes the enrolment and the notification permission
+along with the saved anchors, so the next run measures a permission dialog —
+re-enrol with the command `ui-sandbox.sh` prints, and
+`pm grant … POST_NOTIFICATIONS`. And a saved scroll anchor is per session id,
+so the only way two builds start a scroll from the same place is a *fresh
+session for each*.
+
+**The emulator is `~/repos/emulator-tools`' business, not this repo's.**
+`emu up` creates and boots the AVD named after this checkout — whatever `emu
+name` prints, never a name typed out here, since this file is the same in
+every clone. `run-android.sh` is that plus a build and an install. The `adb`
+on `PATH` after sourcing `android-env.sh` is that repo's wrapper, which fills
+in `-s` from the same rule. Gradle does not go through it, so a Gradle init
+script from `emulator-tools` runs `emu check` before `installDebug`,
+`uninstallDebug` and `connectedAndroidTest` and fails rather than fanning out
+to every attached device; when it refuses, say which device you mean at the
+moment you use it — `ANDROID_SERIAL=$(emu serial) ./gradlew …`.
+
+### Testing llama.cpp and ssh here
+
+**Both are set up here as of 2026-09-04** and need nothing typed. The
+prebuilt CPU llama.cpp lives outside the repo at `~/.local/opt/llama.cpp`
+(the 15 MB `ubuntu-x64` release asset) and is symlinked as
+`/usr/local/bin/llama-server`, which is what makes **discovery find it over
+ssh**: `~/.local/bin` is not on the PATH a non-interactive ssh session gets.
+It resolves its own libraries through `$ORIGIN`, so no `LD_LIBRARY_PATH` is
+needed. One model is downloaded — `unsloth/Qwen3-0.6B-GGUF/Qwen3-0.6B-Q8_0.gguf`,
+639 MB under `~/.local/share/ai-app/models` — and answers at usable speed on
+this VM's 8 cores. **Do not test with a 2-bit quant**: the
+IQ2_XXS of that model produces fluent nonsense, which reads exactly like a
+broken driver — `llama-cli` produces the same from the file directly, which
+is how to tell the two apart in a hurry.
+
+There is no second machine, so **ssh this VM to itself**. That is set up
+too: the key is `~/.config/ai-app/ssh-self` (its public half is in
+`~/.ssh/authorized_keys`, labelled removable), and the real config carries a
+setup called **"this vm over ssh"** — `bob@127.0.0.1` with that
+`identityFile` plus
+`options: ["StrictHostKeyChecking=no", "UserKnownHostsFile=/tmp/ai-app-known-hosts"]`
+so it touches nothing real — offering `claude-cli` and `llama-cpp`. It is the
+whole rig for "does a remote llama session work", since the far machine is
+this one and the model file is the same file. For a throwaway setup of your
+own, point a provider's `command` at something harmless like `/bin/echo`
+rather than at `claude`: the transport is what is under test, the process
+exiting immediately is the signal, and it costs no tokens. The remote login
+shell here is **fish**; the
+remote script and `ssh.rs`'s POSIX quoting happen to mean the same thing in
+both, but that is luck rather than design, and a shell that is neither is the
+thing to suspect first if a remote spawn ever mangles an argument.
+
+## Importing
+
+The import list reports each session's **size as well as its line count**,
+because the two disagree in the way that matters: these transcripts embed
+screenshots as base64, so one line can be a megabyte. On this machine a 69 MB
+session has 3,427 lines and a 44 MB one has 6,792 — nothing about a line
+count tells you what continuing a session will cost. Shown, not warned about;
+importing a large session is a choice somebody is entitled to make.
+
+**Never import a Claude Code session that is open in a terminal.** The app
+refuses it — see PLAN.md for the incident that made that a refusal rather
+than a warning.
+
+**One Claude Code session id can name two files, and the listing offers it
+once.** Resuming from a different working directory makes the CLI write a
+second transcript with the same id under that directory's project folder — an
+ordinary state of a machine, not corruption. Everything downstream addresses
+a session by id, and the phone keyed its list on it, so two rows sharing one
+**closed the app** on a Compose duplicate-key throw. `parse_listing` keeps
+the copy with the most lines, because the other is usually a few-hundred-byte
+stub and is often the *newer* of the two, so recency is the wrong key.
+Deleting removes every copy rather than the first, or the row came back after
+a delete that reported success. The phone's half is `uniqueItems`, which
+every list keyed on a server-chosen id goes through: a repeat there must
+never be able to close the app, whatever produced it.
+
+**Deleting a session offers to take the machine's own transcript with it** —
+`DELETE /sessions/{id}?deleteForeign=true`, behind a switch in the
+confirmation, and only where the driver keeps a record of its own
+(`keepsOwnTranscript`, which today means Claude Code). Off by default,
+because leaving that copy is what makes an ordinary delete recoverable — and
+the dialog's paragraph is rewritten when it is on rather than appended to,
+since the sentence promising the conversation "should still be there to
+import again" is exactly the one the switch makes false. The server deletes
+the machine's copy *first*, so a machine it cannot reach leaves the session
+where it was instead of half-deleted.
+
+## Measurements worth not re-taking
+
+- **What the transcript screen costs to scroll.** Taken 2026-08-30 on the GPU
+  emulator against a real imported transcript with the server at
+  `--delay 120`. Settled and flinging fast, both into fresh history and back
+  through rows already drawn: **5.2–5.9% janky frames, 99th percentile
+  29–32ms, 0–2 slow UI-thread frames.** The stock Settings app on the same
+  device is 3.3% and 38ms, so this is at the platform floor. The number that
+  is *not* at the floor is the first few seconds after opening a session,
+  where every row on the way is being composed for the first time; that is
+  inherent to a lazy list and it is why a measurement taken before the screen
+  settles reads three times worse. **Settle first, then reset `gfxinfo`.**
+- **The reset path is not reachable by reopening a session.** Measured
+  2026-09-04 against a session streaming at 20 events a second: reopening one
+  with an anchor 1,800 events back connects **87–119 events behind**, well
+  under `CATCH_UP_LIMIT`'s 200, because the restore is two requests — the
+  opening page, then one span covering the whole distance. To exercise the
+  reset at all you have to lower `CATCH_UP_LIMIT` in a throwaway build; at 5
+  the app takes the reset on a live connection, clears, refills and carries
+  on without reconnecting.
+- **The session screen's stream survives backgrounding here** — 20 seconds at
+  the launcher while 415 events were produced brought no reconnect at all,
+  which is not what the comment above that loop expects, and is most likely
+  this emulator being headless rather than the phone's behaviour.
+- **Reopening a cached session costs one request for one event** (the probe),
+  and scrolling the whole conversation back costs nothing more; a cold open
+  of the same 500-event session is two pages, 100 events. Measured
+  2026-09-04 on the emulator against the sandbox.
+- **Reading is cheap and editing is not.** The viewer handles a 1 MiB,
+  28,000-line file because it draws one row per line; the editor is one
+  `BasicTextField`, which costs two seconds a frame at 128 kB and stops the
+  app at 1 MiB, so `EDIT_LIMIT` caps it at 32 kB with the reason said on
+  screen. If you make the editor faster, that number is what to move.
+  EXPLORER.md's "What the measurements said" has the rest.

AGENTS.md

@@ -5,11 +5,14 @@ replacing the Claude app for daily use. Rust/Axum backend on the desktop,
 Kotlin/Compose Android app, WireGuard + pinned self-signed TLS + bearer token
 between them.
 
-**`PLAN.md` is the design source of truth** — every decision with its date,
-its rationale, and what was rejected. Read it before changing anything
+**`docs/PLAN.md` is the design source of truth** — every decision with its
+date, its rationale, and what was rejected. Read it before changing anything
 structural, and update it in place when a decision changes rather than
 letting this file and the plan become two versions of the truth. This file is
 the working notes layer: layout, commands, rigs, and things that have bitten.
+The design and working documents live under `docs/` — everything except this
+file and `CLAUDE.md`, which stay at the root because that is where Claude
+Code and other agent harnesses look for them.
 
 The central design point, worth not undoing by accident: **a session is a
 child process, translated into one common event model.** A new session type
@@ -22,7 +25,7 @@ Mirrors `../dev-updater` deliberately: same stack (axum 0.8 +
 axum-server/rustls, tokio, clap; Kotlin 2.4.x + Compose Multiplatform, single
 `:androidApp` module), same cert scheme, same registry pattern. Read
 dev-updater's `README.md` and `AGENTS.md` before diverging from them.
-Module-by-module intent is in PLAN.md's "Backend layout".
+Module-by-module intent is in `docs/PLAN.md`'s "Backend layout".
 
 - `server/` — the Rust backend (`ai-server`). `routes.rs`'s module doc
   comment is the HTTP table and the surface's source of truth.
@@ -40,16 +43,23 @@ Module-by-module intent is in PLAN.md's "Backend layout".
   projects version-locked to the commit this repo pins. What deliberately did
   **not** move is the API surface and the config *schema*: routes, drivers,
   sessions and setups are what makes this project itself.
-- `EXPLORER.md` — the file explorer's design (`server/src/files.rs` and
-  `FilesScreen.kt` / `FileViewer.kt` / `FileEditor.kt`).
-- `TRANSCRIPT_CACHE.md` — the phone's copy of what it has been sent. Read it
-  before touching `TranscriptCache.kt`, `TranscriptSource.kt`, or the opening
-  and stream effects in `SessionScreen.kt`.
-- `TODO.md` — the working list.
-- `RUST.md` — the plan for moving the app to Rust (on the `rustify`
-  branch of the `ai-app-2` clone): what has to be reproduced, the
-  framework decision, and the ordered experiments with their pass
-  conditions. Read it before touching anything under that branch.
+- `docs/` — every design and working document except this file and
+  `CLAUDE.md`:
+  - `docs/EXPLORER.md` — the file explorer's design (`server/src/files.rs`
+    and `FilesScreen.kt` / `FileViewer.kt` / `FileEditor.kt`).
+  - `docs/TRANSCRIPT_CACHE.md` — the phone's copy of what it has been sent.
+    Read it before touching `TranscriptCache.kt`, `TranscriptSource.kt`, or
+    the opening and stream effects in `SessionScreen.kt`.
+  - `docs/TODO.md` — the working list.
+  - `docs/RUST.md` — the plan for moving the app to Rust (on the `rustify`
+    branch of the `ai-app-2` clone): what has to be reproduced, the
+    framework decision, and the ordered experiments with their pass
+    conditions. Read it before touching anything under that branch.
+  - `docs/IRIS.md`, `docs/IRIS_TODO.md`, `docs/DECISIONS.md`,
+    `docs/LAYOUT.md`, `docs/TEXTURES.md`, `docs/CLIENT_CORE.md` — iris's
+    own public API log, working list, decisions log, layout/render design,
+    and texture-atlas design, and the client-core crate's design,
+    respectively.
 - `.dev-updater.ron` — what Dev Updater builds here: the server (run as
   `service: Managed(…)`, supervised by Dev Updater's own implementation
   rather than a script kept here) and the APK, in parallel. It points at
@@ -86,7 +96,11 @@ two icon buttons the same width without either being given one — and why
   :androidApp:compileDebugKotlin :androidApp:lintDebug
   :androidApp:testDebugUnitTest`. The unit tests are JVM-only and cover the
   syntax highlighter, the ANSI parser and the transcript cache — the app's
-  pure logic with no Android in it.
+  pure logic with no Android in it. Touching anything under `BenchFixture.kt`,
+  `BenchNetwork.kt`, `BenchRun.kt` or the `bench` build type also needs
+  `:androidApp:compileBenchKotlin :androidApp:lintBench` — a second build
+  type compiles separately and lint has caught real bugs debug alone never
+  would (see "Android Lint" below).
 - **Android Lint is not optional and is not run by a build.** It found a
   crash that had been shipping (`java.time` on a minSdk-24 app with
   desugaring off) and later a permission check that silently dropped every
@@ -146,6 +160,27 @@ two icon buttons the same width without either being given one — and why
 
 Each exists because something was invisible without it.
 
+- **The `bench` build type and `app/bench-fixture/`** exist for P0 (RUST.md
+  and DECISIONS.md's 2026-09-05 entries), the phone benchmark gate Iris
+  asked for before porting continues: a deterministic, checked-in synthetic
+  transcript (`app/bench-fixture/generate.py`, never a real one) that both
+  this app and iris open with no server, so a frame-time comparison
+  measures the renderer rather than the data. `./build-apk.sh bench` builds
+  it — own application id (`com.example.aiapp.bench`) and label ("AI
+  Sessions bench") so it installs beside a real enrollment rather than
+  replacing it. Opening it goes straight to a session screen holding the
+  fixture (no enrollment, no permission prompts) with a "Run benchmark"
+  control beside "Copy" in session settings: it drives the same scroll loop
+  and streaming phase `transcript-bench.sh`/`stream-bench.sh` drive over
+  `ui-trace`, but in-process, since a real phone has no usable system
+  tracing and no agent can drive one (this-machine-android's skill).
+  `BenchFixture.kt`/`BenchNetwork.kt` fake the backend by installing a
+  `URLStreamHandlerFactory` that answers `TranscriptSource`/`EventStream`'s
+  requests from an in-memory copy of the fixture instead of opening a
+  socket — so the fold, the paging and `uniqueItems` under test are the
+  screen's real ones, never a shortcut built just for this. The report
+  gains a `bench:` section (process CPU time, peak RSS, battery current) on
+  every build, empty except when `BenchRun.kt` filled it in.
 - **`app/ui-sandbox.sh`** — a second `ai-server` with its own `$HOME`, config
   and data directory, holding eight invented Claude Code transcripts and a
   `claude` that is two lines of shell. **That isolation is the point**: the
@@ -226,6 +261,13 @@ Each exists because something was invisible without it.
   framework, from `atrace` text output with no trace processor needed. It is
   how the cost of a layout node per link was attributed to the framework
   rather than guessed at.
+- **`iris/android-app/build-apk.sh [debug|release] [--abi ...] [--features
+  ...]`** builds iris-android-app's cdylib (`cargo ndk`) and its APK
+  (Gradle) in one step and verifies the result (`aapt2`/`apksigner`), and
+  **`iris/android-app/run-bench.sh [--apk PATH]`** installs it on this
+  checkout's own emulator, taps "Run benchmark" by label, and prints the
+  report -- written so the P0 build/install/tap/read-report cycle stops
+  being retyped by hand each time (docs/RUST.md's P0 box).
 
 ### Driving the UI
 
@@ -312,7 +354,7 @@ means here:
 ## Sessions outlive the backend
 
 Since 2026-08-29 a session's process is deliberately left running when
-`ai-server` stops, and adopted again when it starts. PLAN.md has the design;
+`ai-server` stops, and adopted again when it starts. docs/PLAN.md has the design;
 day to day:
 
 - **Stopping the server no longer stops the sessions.** After `pkill
@@ -345,7 +387,7 @@ count tells you what continuing a session will cost. Shown, not warned about;
 importing a large session is a choice somebody is entitled to make.
 
 **Never import a Claude Code session that is open in a terminal.** The app
-refuses it — see PLAN.md for the incident that made that a refusal rather
+refuses it — see docs/PLAN.md for the incident that made that a refusal rather
 than a warning.
 
 **One Claude Code session id can name two files, and the listing offers it
@@ -521,4 +563,4 @@ belongs in `~/.claude/TOOLCHAIN.md` or `~/.claude/MACHINE.md` instead.
   `BasicTextField`, which costs two seconds a frame at 128 kB and stops the
   app at 1 MiB, so `EDIT_LIMIT` caps it at 32 kB with the reason said on
   screen. If you make the editor faster, that number is what to move.
-  EXPLORER.md's "What the measurements said" has the rest.
+  docs/EXPLORER.md's "What the measurements said" has the rest.

DECISIONS.md

@@ -1,30 +1,44 @@
-# Decisions taken for Iris to review
+# Decisions awaiting review
 
-Short list of design choices made by the design agent without asking, so
-they can be judged and reversed later. Detail lives in RUST.md (and IRIS.md
-for iris API changes); this file is only the summary. Newest first. Items
-marked **DEFERRED** are ones the agent chose not to decide alone.
+Choices made while working autonomously, for Bryan to keep or change. Each
+says what was picked and why; the detail is in the design doc it names.
+Delete an entry once it has been looked at.
 
-## 2026-09-05
+## Subagent views (2026-09-05, `SUBAGENTS.md`)
 
-- **Touch drag on a transcript row follows Android's own rule**: a vertical
-  drag pans the list immediately; a stationary press held 500 ms starts a
-  text selection which further dragging extends; a horizontal drag while
-  something is already selected extends that selection without the wait.
-  One `DragArbiter` per list decides it (`iris/src/sense.rs`). Chosen over a
-  "text layer always wins" or "list always wins" rule because either loses
-  one of the two gestures a reader expects.
-- **E4's desktop shape is a new `iris/desktop-app` crate**: a winit window
-  holding `transcript-ui`'s screen beside a session list, talking to a real
-  `ai-server` through `client-core`. It enrols by pasting the same
-  `aiapp://enroll?…` link a phone scans (`client-core::config::EnrolledServer`)
-  and keeps it owner-only under `$XDG_CONFIG_HOME/ai-app-desktop/`. The
-  pinned CA is a path given on the command line, not baked in. Chosen so
-  the phone and desktop share one enrolment format and no second one is
-  invented.
-- **Order of remaining work**: finish the two in-flight pieces above, then
-  the transcript screen's Android integration and the `transcript-bench.sh`
-  comparison against Compose — the numbers the recommendation still lacks.
-- **DEFERRED — whether to commit to iris over Masonry for `ai-app`.** Waits
-  on the bench numbers above; RUST.md's recommendation says what the
-  measurements must show.
+Made on my own judgement, limited blast radius:
+
+1. **A subagent is a transcript, not a session.** It has no process,
+   controls or settings; it is addressed as `/sessions/{id}/subagents/{sub}`
+   and stored under the session's directory, so deleting the session takes
+   it. Alternative rejected: registering it as a session of its own, which
+   would give it a card in the main list and a driver that can do nothing.
+2. **Read-only view is the session screen minus its controls**, rather than
+   a second, simpler transcript screen. Keeps paging, caching, selection
+   and rendering in one place. Cost: a `readOnly` mode threaded through
+   `SessionScreen`.
+3. **The list only carries a count.** Each session row says how many
+   subagents it has; their titles and statuses are fetched when the card is
+   expanded. Keeps `GET /sessions` from reading every subagent transcript.
+   Consequence: an expanded card's statuses refresh with the list, not live.
+4. **Expanded/collapsed is remembered per session on the phone**, not on
+   the server. Collapsed by default, per the transcript convention that new
+   things arrive collapsed.
+5. **Subagents of imported sessions are not shown.** The import path still
+   skips `isSidechain` records; the CLI's own `subagents/agent-*.jsonl` files
+   are not read. Only subagents run while this backend was watching exist.
+6. **Echo grows `/subagent [n]`** as the test rig, so nothing here needs a
+   paid turn to exercise.
+
+Deferred, because they reach further than this feature:
+
+- **Live status on the list.** Whether the session list should follow a
+  stream at all (it refreshes on demand today) decides whether subagent
+  status can ever be live there. Not changed.
+- **Nested subagents.** A subagent's own Task calls are shown as tool calls
+  in its transcript and are not given transcripts of their own. Supporting
+  that is the same mechanism one level down, but the UI would need nested
+  expanders.
+
+- **The subagent status row says "context unknown".** Nothing measures a
+  subagent's context; the row could leave it out rather than admit it.

IRIS.md

@@ -1,277 +0,0 @@
-# iris: notable public API changes
-
-For Iris to read on her own time. Each entry is a change to iris's public
-surface that a widget author or app author would notice: a trait method
-added, removed or re-shaped; a type that callers construct differently; a
-capability that moved. Small and trivial changes do not go here.
-
-An entry gives the date, what changed, why, and a short before/after where
-it helps judge the change without the session that made it. Newest first.
-
-## 2026-09-05: `transcript_ui::build_tree` (RUST.md's E4)
-
-`transcript_ui::build` claimed the whole window (`ui_state.set_root(tree)`)
-as its last step, which is right for a window that *is* the transcript
-screen (the winit example, an eventual Android cdylib) and wrong for the
-desktop app, which puts a session list beside it. `build_tree` is `build`
-minus that last step: it returns `(TranscriptScreen, StrongWidget)` instead
-of just `TranscriptScreen`, and the caller decides where the tree goes —
-into `ui_state.set_root`, or into a `WidgetPtr` alongside something else
-(`iris/desktop-app`'s `rebuild_transcript`). `build` is now one line calling
-`build_tree` and doing the `set_root` itself, so existing callers are
-unaffected.
-
-```rust
-// before, and still available, for a caller that wants to *be* the window:
-let screen = transcript_ui::build(rsc, &mut ui_state, rows);
-
-// new, for a caller embedding the screen beside something else:
-let (screen, tree) = transcript_ui::build_tree(rsc, rows);
-some_widget_ptr(rsc).set(tree);
-```
-
-
-## 2026-09-05: `DragArbiter`, pan-vs-select for one shared touch gesture (RUST.md's I5)
-
-New public type, `iris::sense::DragArbiter`. Why: a widget author who
-registers both a list-level pan and a row-level drag-to-select on the same
-touch gesture has no way to arbitrate between them — `core/src/sense.rs`'s
-`run_sensors` always gives the innermost layer first refusal, so the inner
-one wins every frame it is pressed, not just the frame the press started
-(this is exactly what left transcript-ui's touch-drag panning unreachable
-until now). `DragArbiter` is one small state machine, one instance per
-gesture surface (a whole list, not per row), that a caller drives with its
-own `press_start`/`update`/`release` calls and a caller-supplied `Instant`
-(so it is unit-testable without a real clock or a render harness). It
-decides the way Android itself does: an ordinary vertical drag pans
-immediately; a stationary press held `LONG_PRESS` (500ms) starts a
-selection, which any further drag then extends; a horizontal drag while
-something is already selected extends it immediately, skipping the wait.
-
-```rust
-// One per list, held alongside whatever state coordinates the rows:
-let mut arbiter = DragArbiter::new();
-
-// On press-down:
-arbiter.press_start(pos, Instant::now(), already_selected);
-// Every frame the button/finger stays down:
-match arbiter.update(pos, Instant::now()) {
-    DragOutcome::Pan(dy) => list.scroll(-dy),
-    DragOutcome::SelectStart => selection.begin(...),
-    DragOutcome::SelectExtend => selection.extend(...),
-    DragOutcome::Undecided => {}
-}
-// On release:
-arbiter.release();
-```
-
-`transcript-ui`'s `Selection::drag` (`transcript-ui/src/selection.rs`) is
-the reference caller: every row's `CursorSense::click_or_drag() |
-CursorSense::unclick()` handler routes through one `Selection`-owned
-arbiter instead of calling `begin`/`extend` directly, so a drag that starts
-on a row's own rendered text now pans the list correctly instead of
-always starting a selection. 8 new unit tests in `iris/src/sense.rs`'s
-`drag_arbiter_tests` module.
-
-## 2026-09-05: `SpanStyle`, per-range text styling (RUST.md's I5)
-
-A `TextBuffer` used to have exactly one style (`TextAttrs`: colour, size,
-family, ...) for its whole string, applied via `push_default` into parley's
-ranged builder. `SpanStyle` is a second, optional layer: a byte range plus
-whichever of colour/family/font size/bold/italic/underline it overrides,
-pushed with parley's own `push(property, range)` instead. Why: a transcript
-row's markdown (a heading, **bold**, `inline code`, a link) all inside one
-wrapped paragraph needs each to carry its own look while the paragraph
-still wraps and selects as a single buffer — the thing `masonry`'s
-`TextArea` cannot do (`StyleSet` is one style for the whole editor,
-`text_area.rs:43-44`'s `// TODO: RichTextInput`), and the reason this
-existed at all.
-
-```rust
-let (text, spans) = transcript_ui::markdown::render_markdown(src, 16.0);
-wtext(text)
-    .spans(spans)   // new: TextBuilder::spans, on both Text and TextEdit
-    .editable(EditMode::MultiLine)
-    .add(rsc);
-```
-
-Two things a widget author should know before reaching for it:
-
-- **Call `.spans()` before or after `.editable()`, both work** — the field
-  lives on `TextBuilder` itself, not either output type, and both
-  `TextOutput::run` and `TextEditOutput::run` apply it to the buffer via
-  `TextBuffer::set_spans`. **These two call sites are a pair**: adding a
-  third `TextBuilderOutput` impl without also calling `set_spans` there
-  reproduces the exact bug this box shipped once already (spans silently
-  dropped for `TextEdit`, found only by screenshotting, not by any test —
-  `markdown.rs`'s own unit tests check string/range logic, which is
-  correct in isolation and proves nothing about whether the render path
-  ever sees it).
-- **Colour is now per-glyph, not per-buffer.** `PlacedGlyph` gained a
-  `color: UiColor` field (from parley's own per-run `Style::brush`), and
-  `Painter::glyphs` draws each glyph in its own colour instead of
-  `RenderedText::color` uniformly. `RenderedText::color` still exists (the
-  buffer's *base* colour, for a caller that wants it as a whole, e.g. to
-  tint a cursor) but no longer drives what a glyph actually renders as.
-
-## 2026-09-05: accessibility names via AccessKit (RUST.md's I4)
-
-`.label()` (already in `trait_fns.rs`, previously unused anywhere in-tree)
-is now load-bearing: it's the one thing that puts a widget in the AccessKit
-tree `iris_core::ui::access::AccessTree` builds and both backends push
-out. A widget author who wants a control to be findable by name (and
-tappable by name, through `ui-trace`/a real screen reader) calls `.label()`
-on it; nothing else is required, and a widget nobody labels is invisible
-to this system at zero cost, not just zero UI.
-
-```rust
-let button = rect(Color::LIME)
-    .on(CursorSense::click(), move |_, rsc| { ... })
-    .label("Add task");   // now findable by uiautomator/AccessKit as "Add task"
-```
-
-Two new things a widget author might touch directly:
-
-- **`Widget::access_role(&self) -> accesskit::Role`**, default `Unknown`.
-  Override it if your widget has a real platform equivalent —
-  `TextEdit` now returns `TextInput`/`MultilineTextInput` by `EditMode`.
-  Only consulted for a widget that also has a `.label()`; an unlabelled
-  widget's `access_role` is never called.
-- **`Widgets::named() -> impl Iterator<Item = WidgetId>`** — every widget
-  with an explicit label, for anything else that wants to walk the same
-  set `AccessTree` does.
-
-Nothing about `Painter`, `draw`, or the layout/move machinery changed —
-this sits entirely beside them, reading `resolved_region`'s output rather
-than participating in producing it.
-
-## 2026-09-05: `List`, a virtualised bottom-anchored list (RUST.md's I3)
-
-A new widget, `iris::widget::List` (`iris/src/widget/list.rs` -- read its
-module doc first), for the transcript's kind of screen: variable-height
-rows, keyed by a `u64`, composed only while visible, moved rather than
-re-laid-out on scroll, a scroll anchor that survives a row inserted above
-it, "more" sentinels at each end, and "hold the edge nearest the tap" when
-a row's height changes (`note_tap`, resolved in the layout pass).
-
-```rust
-let mut list = List::new(Axis::Y);
-list.push_back(ListRow::new(key, row_widget));   // O(1)
-list.push_front(ListRow::new(older_key, row));   // O(1), anchor unaffected
-list.set_more_before(Some(spinner_widget));      // sentinel, drawn at the edge
-list.note_tap(viewport_y);                       // before mutating a row's height
-let (top, bottom) = list.extent(key).unwrap();   // last frame's on-screen box, if visible
-```
-
-Built entirely out of existing primitives (`Painter::widget`/`widget_within`/
-`reposition`/`draw_twice`, and `draw_inner`'s own old-children diffing) --
-no new mechanism was added to the render core for it. One correctness
-lesson worth reading even for other widgets: a row that fills whatever
-region it is offered (`Rect`, `is_size_independent`) cannot be measured at
-a throwaway oversized region and then merely `reposition`ed into place --
-`reposition` only ever writes an offset, never a size, so the oversized
-primitive stays oversized. `List` fixes this by caching each row's real
-height once measured and placing an already-known row directly at its
-exact box; see `list.rs`'s `place` for the full reasoning and
-`a_fill_shaped_background_is_not_left_oversized` for the regression test.
-
-## 2026-09-05: a second backend (android-view), and what moved to make room for it
-
-RUST.md's I2. Three changes a widget or app author would notice, all in
-service of the same thing: `default` (winit) and the new `android`
-(android-view) backends sharing what does not depend on windowing.
-
-- **`Selector`/`Selectable`'s bound changed from `Rsc::State:
-  HasDefaultUiState` to `Rsc::State: FocusHost`** (new trait, `attr.rs`).
-  `HasDefaultUiState` still exists and still works — `default/attr.rs` now
-  implements `FocusHost` for anything that has it — so a winit app's
-  existing code is unaffected. An Android app implements `FocusHost` via
-  `HasAndroidUiState` instead. Affects only an app that referenced
-  `HasDefaultUiState` directly at a `Selectable`/`Selector` call site
-  rather than through `.attr::<Selectable>(())`, which nothing in-tree
-  does.
-- **`Tasks::init` takes `Arc<dyn RequestRedraw>` instead of
-  `Arc<winit::window::Window>`.** `RequestRedraw` (`task.rs`) is one method,
-  `fn request_redraw(&self)`; `winit::window::Window` implements it
-  (`default/render.rs`), so `Tasks::init(window)` at a call site is
-  unchanged by inference. Only matters if something constructed a `Tasks`
-  directly rather than through `DefaultRsc`/`AndroidRsc`.
-- **`TextEdit::apply_event`/`TextInputResult` are `#[cfg(not(target_os =
-  "android"))]`** — they take a `winit::event::KeyEvent`, which does not
-  exist on Android; `android/input.rs` drives the same primitives
-  (`backspace`/`delete`/`motion`/`insert`, all still unconditional) from
-  `ndk::event::Keycode` directly instead. New unconditional getters on the
-  way: `TextEdit::text()`/`selection_range()`/`caret()`, and
-  `TextEditCtx::delete_byte_range`/`set_cursor_byte` — the primitives
-  `android/ime.rs`'s `InputConnection` bridge needed and that were not
-  previously exposed publicly.
-
-## 2026-09-04: `Widget::draw` reports the size it used; `desired_width`/`desired_height` are gone
-
-A widget used to implement three methods (`draw`, `desired_width`,
-`desired_height`); it now implements one, `fn draw(&mut self, painter: &mut
-Painter) -> Size`, which draws into `painter.region()` and returns how much
-of it was used. Why: the two extra methods routinely re-simulated what
-`draw` was about to do anyway (`Span::desired_ortho` copied its own draw
-loop to get cross-axis sizing right) — one visit per widget per frame
-instead of up to three. A container that needs a child's size before
-placing it (alignment, centering) draws the child once at a provisional
-region, reads the returned `Size`, and calls the new `Painter::reposition`
-to move it into its final spot — an O(1) offset write, not a second draw. A
-widget whose drawn output never depends on the size it's given (a
-fixed-size `Rect`, a decoded `Image`) overrides the new `fn
-is_size_independent(&self) -> bool { false }` to `true`, which skips
-redrawing it when only its offered region changes shape.
-
-```rust
-// before
-fn draw(&mut self, painter: &mut Painter) { /* ... */ }
-fn desired_width(&mut self, ctx: &mut SizeCtx) -> Len { /* ... */ }
-fn desired_height(&mut self, ctx: &mut SizeCtx) -> Len { /* ... */ }
-
-// after
-fn draw(&mut self, painter: &mut Painter) -> Size { /* ... */ }
-```
-
-`SizeCtx` and `Cache` are gone with it — see `LAYOUT.md` for the full
-design, the move-offset mechanism this shipped alongside, and the file
-list.
-
-## 2026-09-04: texture pipeline rebuilt off the binding array
-
-`Textures`/`TextureHandle`, `GlyphPrimitive`, and `UiRenderNode::new` all
-changed shape. Why: the old pipeline bound every texture ever drawn in one
-`binding_array<texture_2d<f32>>` and asked every device, unconditionally,
-for `VK_EXT_descriptor_indexing` — a real share of Android GPUs lack it,
-and it failed outright on the Android emulator's software Vulkan. See
-TEXTURES.md's "Recommended shape" and "Implemented, 2026-09-04".
-
-- **`UiRenderNode::new` drops its `limits: UiLimits` parameter, and
-  `UiLimits` is gone.** Before: `UiRenderNode::new(&device, &queue,
-  &config, UiLimits::default())`. After: `UiRenderNode::new(&device,
-  &queue, &config)`. Nothing replaces it — there are no more
-  binding-array limits to size.
-- **`src/default/render.rs`'s device request asks for no features and no
-  binding-array limits.** Before: `required_features:
-  Features::TEXTURE_BINDING_ARRAY | Features::PARTIALLY_BOUND_BINDING_ARRAY
-  | Features::SAMPLED_TEXTURE_AND_STORAGE_BUFFER_ARRAY_NON_UNIFORM_INDEXING`
-  plus two `max_binding_array_*` limits. After: `Features::empty()` (the
-  `DeviceDescriptor` default) and only `max_buffer_size` set, which was
-  never about the binding array.
-- **`TextureHandle` has no `primitive()` method any more**; a caller
-  outside `iris` shouldn't have been calling it (it fed the old renderer's
-  internals), but if something did: use `image_index()` for a standalone
-  image's bind-group index. There is no equivalent for a page — a page has
-  no bind group of its own now, see below.
-- **`GlyphPrimitive` has no public constructor from a struct literal.**
-  Before: `GlyphPrimitive { uv_min, uv_max, view_idx, sampler_idx, color,
-  flags }`. After: `GlyphPrimitive::new(uv_min, uv_max, layer, color,
-  flags)` — one `layer` (the shared atlas array's layer) instead of a
-  `view_idx`/`sampler_idx` pair, since a page is now a layer of one array
-  texture rather than its own bound texture.
-- **A widget author drawing images is unaffected**: `Painter::texture`/
-  `texture_at`/`texture_within` and `Textures::add` keep their signatures.
-  What changed underneath is that each standalone image now gets its own
-  `wgpu::BindGroup` and draw call instead of a slot in the shared array —
-  invisible from the widget API, visible only in `UiRenderNode`'s internals
-  and in `iris`'s device requirements.

SUBAGENTS.md

@@ -0,0 +1,141 @@
+# Subagents
+
+A session's subagents -- the helpers a Claude Code session starts through its
+Task tool -- each get a transcript of their own, listed under the session's
+card and readable in the same transcript view the session has. Designed
+2026-09-05; the decisions Bryan has not yet reviewed are in `DECISIONS.md`.
+
+## What a subagent is here
+
+**A subagent is a second transcript owned by a session, in the same event
+model, with no process and no controls.** It is not a session: it cannot be
+messaged, stopped or started, and it has no setup, model or usage of its
+own. Everything it shares with a session -- the transcript file format, the
+paging routes, the SSE stream, the phone's cache and rendering -- is reused
+by addressing, not by copying.
+
+The CLI reports a subagent's messages on the parent's own stream-json
+output, each carrying `parent_tool_use_id` = the id of the Task `tool_use`
+that started it. Before this the translator dropped those lines
+(`subagent_events_are_not_duplicated_into_the_transcript`); now it routes
+them to that subagent's own translator and transcript. The parent's
+transcript still shows only the Task call itself.
+
+## Storage
+
+Under the session directory:
+
+```
+<session>/subagents/<tool_use_id>/meta.json        {title, created}
+<session>/subagents/<tool_use_id>/transcript.jsonl same SeqEvent lines as the session's
+```
+
+The id is the Task tool_use id (`toolu_…`), which is unique, stable across a
+backend restart, and already the key everything on the parent side uses.
+Only ids matching `[A-Za-z0-9_-]+` are ever created or looked up, since the
+id becomes a path.
+
+The transcript's sequence numbers are its own, starting at 1. `Transcript`,
+`read_window`, `catch_up` and `read_after` work on it unchanged.
+
+Its path out: deleting the session deletes its directory, subagents included.
+There is no separate delete.
+
+## Lifecycle, as events in the subagent's transcript
+
+1. Created on the first child line for an unseen parent id (or, when the
+   parent Task call was seen, at that call). First lines written:
+   `Status Running`, then `UserMessage { text: <the Task's prompt> }` when
+   the prompt is known -- it genuinely is the subagent's first user turn.
+2. Every child line is translated by that subagent's own `Translator`
+   (one per subagent: tool ids are unique but streaming deltas are by
+   content-block index, and parallel subagents interleave).
+3. **The parent's `tool_result` never finishes a subagent.** The Task tool
+   runs in the background by default: the `tool_result` -- "Async agent
+   launched..." -- arrives the moment it *starts*, while the subagent goes
+   on working for however long its own turn takes, sometimes minutes. What
+   ends it is its own turn ending: the raw API's `message_delta` on its
+   stream carrying `stop_reason: "end_turn"` (a `stop_reason` of `tool_use`
+   is the model about to call one, not an end), or a `result` line for its
+   own turn if a future CLI version ever sends one. Either maps to
+   `Status Exited`; the subagent's vocabulary has no `Idle`, so the
+   equivalent event `dispatch` produces for an ordinary session is dropped
+   rather than written. A shipped version of this finished on the
+   `tool_result` instead, which read a running background agent as
+   "finished" with its transcript truncated at the moment it launched.
+4. **A child line for a subagent that already finished reopens it**
+   (`Status Running`) rather than being dropped: a background Task can be
+   sent another message long after its first turn ended, and that is
+   exactly what a further line for it means. Same transcript, same child
+   `Translator`, just picking back up.
+5. When the parent session's process exits (`Status Exited` on the
+   session), every subagent still `Running` gets `Status Exited` too: its
+   process was the parent's.
+
+A subagent that was mid-flight when the backend restarted keeps working:
+the registry reopens the existing transcript on the next child line, and
+the file continues its sequence -- the same reopening #4 describes, whether
+what closed it was a restart or its own `end_turn`. If its turn ended while
+the backend was down nothing recorded that until the next line arrives, so
+its last status stays `Running`, which the list reports as **unknown**
+rather than as running (see the wire shape) until then.
+
+Title: the Task call's `description` input, then ` (<subagent_type>)` when
+one is given; falling back to the tool's name when the child arrives before
+(or without) the parent call being seen.
+
+## Server layout
+
+- `session/subagent.rs` -- the registry: `Subagents` (per session, in
+  `Shared`), `Subagent` (its `Transcript` behind a mutex plus a
+  `broadcast::Sender<SeqEvent>`), `record(id, event)`, `start(id, title,
+  prompt)`, `finish(id)`, `reopen(id)`, `finish_all()`, `list()` from disk. Drivers get an
+  `Arc<Subagents>` beside their `EventSink`; llama ignores it.
+- `session/claude/translate.rs` -- routes child lines by parent id, holds
+  one child `Translator` per subagent, remembers pending Task calls'
+  description/prompt/subagent_type.
+- `session/echo.rs` -- `/subagent [n]`: the test rig. Starts *n* (default 1)
+  subagents at once, each named "helper k". Each writes the prompt as its
+  user message, streams a few words of text, runs one `Bash` tool call, then
+  finishes about three seconds after starting, and the parent's Task calls
+  end when their subagent does. Three seconds so the running state can be
+  seen on the phone.
+- `routes.rs` -- three routes, in the doc table.
+
+## Wire shape
+
+```
+GET /sessions/{id}                       SessionInfo gains `subagents: N` (count, 0 when none)
+GET /sessions                            same field on each row
+GET /sessions/{id}/subagents             [{id, title, status, created, lastActivity}], oldest first
+GET /sessions/{id}/subagents/{sub}/transcript   exactly the session transcript's query and answer
+GET /sessions/{id}/subagents/{sub}/events?after=N  exactly the session events stream
+```
+
+`status` is the transcript's last `Status` event, serialised like a session's
+(`running`, `exited`), except that a subagent whose session is not itself
+running cannot be running: the list answers `unknown` for that one. The
+phone words these as *running*, *finished* and *unknown* on the subcard.
+
+The count on `SessionInfo` is a directory listing, so the list stays cheap.
+The per-subagent status is only read when the list route is asked for.
+
+## Phone
+
+- `SessionSummary.subagents: Int`. A card with a non-zero count ends in an
+  expander row -- a full-width `Chevron(Pointing.Down)` row that flips to
+  `Pointing.Up` -- collapsed by default. Expanding fetches
+  `/sessions/{id}/subagents` and draws one `OutlinedCard` per subagent,
+  indented inside the session card, the way dev-updater draws a project's
+  components: title, then the status word and a relative time. The
+  expansion state is per session id and survives a refresh of the list.
+- Tapping a subcard opens `Screen.Subagent`, which is `SessionScreen` in
+  **read-only** form: the same transcript, paging, cache, selection,
+  images and status row, with the composer, the process button, the model
+  picker, the files button, the settings cog and the usage bar left out.
+  The header shows the subagent's title with the session's title beneath
+  it. Back returns to the list.
+- Addressing: `fetchTranscript`, `EventStream`, `TranscriptSource` and the
+  cache take a transcript address rather than a session id --
+  `sessions/{id}` or `sessions/{id}/subagents/{sub}` -- so the cache nests a
+  subagent's copy under its session's and the same code serves both.

app/androidApp/build.gradle.kts

@@ -102,6 +102,16 @@ android {
         targetSdk = 37
         versionCode = 1
         versionName = "1.0"
+        // Read by MainActivity to decide, at startup, whether this is the P0 benchmark build
+        // (docs/RUST.md's P0 box) rather than the app somebody enrolled. False everywhere except
+        // the `bench` build type below, which overrides it.
+        buildConfigField("boolean", "FIXTURE_MODE", "false")
+    }
+    buildFeatures {
+        // Only for FIXTURE_MODE above; nothing else here reaches for generated BuildConfig fields.
+        buildConfig = true
+        // Only for the bench build type's resValue("string", "app_name", ...) below.
+        resValues = true
     }
     packaging {
         resources { excludes += "/META-INF/{AL2.0,LGPL2.1}" }
@@ -131,6 +141,35 @@ android {
             isMinifyEnabled = false
             if (keystore != null) signingConfig = signingConfigs.getByName("release")
         }
+        // P0's benchmark build (docs/RUST.md, docs/DECISIONS.md's 2026-09-05 entry): release
+        // optimisations so a frame time measured here means what release means everywhere else in
+        // this project, its own application id so it installs beside a real enrollment rather than
+        // replacing it, and FIXTURE_MODE so MainActivity opens straight onto the fixture session
+        // instead of asking to be enrolled. Signed with the same key as release -- it never talks
+        // to a real backend, so there is no CA of its own to mismatch, and a second keystore would
+        // be one more secret to keep off this machine's shared mount for no benefit.
+        create("bench") {
+            initWith(getByName("release"))
+            // :link (wg-app-link) has no "bench" build type of its own -- it is a library shared
+            // with dev-updater and has no reason to know this project invented one -- so this says
+            // which of its build types to link against instead.
+            matchingFallbacks += listOf("release")
+            applicationIdSuffix = ".bench"
+            // "AI Sessions bench" everywhere the OS shows the app's name (launcher, recents,
+            // Settings): this resValue overrides res/values/strings.xml's app_name for this
+            // build type alone, and AndroidManifest.xml's android:label reads @string/app_name
+            // rather than a literal so a build type can override it without touching the
+            // manifest.
+            resValue("string", "app_name", "AI Sessions bench")
+            buildConfigField("boolean", "FIXTURE_MODE", "true")
+            if (keystore != null) signingConfig = signingConfigs.getByName("release")
+        }
+    }
+    sourceSets {
+        // The fixture both bench builds (this one and iris's) open with; see
+        // app/bench-fixture/README.md. Read directly from its own directory rather than copied
+        // into androidApp/src -- one file to keep in sync with the generator, not two.
+        getByName("bench").assets.directories.add("../bench-fixture/assets")
     }
     compileOptions {
         sourceCompatibility = JavaVersion.VERSION_21

app/androidApp/src/main/AndroidManifest.xml

@@ -25,7 +25,7 @@
          the fix is a judgement about how this app should look. Drop this
          suppression when a real icon lands. -->
     <application
-        android:label="AI Sessions"
+        android:label="@string/app_name"
         android:allowBackup="true"
         android:theme="@android:style/Theme.Material.Light.NoActionBar"
         tools:ignore="MissingApplicationIcon">

app/androidApp/src/main/kotlin/com/example/aiapp/Api.kt

@@ -142,6 +142,20 @@ data class SessionSummary(
     val keepsOwnTranscript: Boolean,
     /** How much the session asks before acting; null when it was never set. */
     val permissionMode: String?,
+    /**
+     * How hard the model thinks, or null for the CLI's own default.
+     *
+     * Null is a level somebody can choose, not only one to start in -- see [EFFORT_LEVELS]. It is
+     * reported rather than assumed for the same reason [permissionMode] is.
+     */
+    val effort: String?,
+    /**
+     * Whether a thinking level does anything here -- a Claude CLI session, not a llama or echo one.
+     *
+     * Asked of the server rather than worked out from the provider's name, because this is a
+     * property of the driver's *kind* and the phone only has the name.
+     */
+    val takesEffort: Boolean,
     /**
      * Whether this continues a session the machine already had, which changes what deleting means.
      */
@@ -153,6 +167,24 @@ data class SessionSummary(
      * itself from a default is one you can turn off while believing you are reading it.
      */
     val notify: Boolean,
+    /**
+     * Whether this session sends itself a message once its account's usage limit lifts, and what
+     * that message says.
+     *
+     * The message is what the server would actually send, with its own default already filled in,
+     * so the field shows the words rather than an empty box standing for them.
+     */
+    val autoResume: Boolean,
+    val autoResumeMessage: String,
+    /**
+     * When the server next intends to check whether the limit has lifted, in epoch seconds, or null
+     * when nothing is waiting.
+     *
+     * A time to *ask*, not a time to resume: the server checks the meter at that moment and waits
+     * again if the limit is still on. Worded that way wherever it is shown, because a promise this
+     * app cannot keep is worse than no time at all.
+     */
+    val resumeAt: Double?,
     /**
      * The directory the session works in, or null where it was never given one.
      *
@@ -178,8 +210,27 @@ data class SessionSummary(
      * server because that is where a provider's kind is known.
      */
     val maxImageEdge: Int?,
+    /**
+     * Which of `GET /usage`'s snapshots is about this session, and null where nothing meters it.
+     *
+     * The rate-limit bar answers a question about an *account*, and what decides which account --
+     * if any -- is the provider this session runs, not the machine it runs on. Pairing by machine
+     * alone drew the Claude CLI's five-hour window under every echo session on a machine that also
+     * has the CLI: a quota that session cannot spend and could never run down. Decided by the
+     * server for the same reason [maxImageEdge] is -- it is a fact about the provider's kind, and
+     * this app has only its name.
+     */
+    val usageProvider: String?,
     val status: String,
     val lastActivity: Double,
+    /**
+     * How many subagents this session has, however their own status now reads.
+     *
+     * A directory listing on the server rather than a status read per subagent, so the list stays
+     * cheap; the per-subagent state is only fetched when the card is expanded. Zero on a server
+     * that predates subagents, so this app still opens against one.
+     */
+    val subagents: Int,
 )
 
 private fun parseSession(session: JSONObject) =
@@ -192,14 +243,24 @@ private fun parseSession(session: JSONObject) =
         title = session.getString("title"),
         model = session.optString("model").ifEmpty { null },
         permissionMode = session.optString("permissionMode").ifEmpty { null },
+        effort = session.optString("effort").ifEmpty { null },
+        takesEffort = session.optBoolean("takesEffort", false),
         imported = session.optBoolean("imported", false),
         notify = session.optBoolean("notify", true),
+        autoResume = session.optBoolean("autoResume", false),
+        // The server sends its own default rather than nothing, so an empty answer means an older
+        // server -- and this app's word for it is the same word.
+        autoResumeMessage =
+            session.optString("autoResumeMessage").ifEmpty { DEFAULT_RESUME_MESSAGE },
+        resumeAt = if (session.has("resumeAt")) session.getDouble("resumeAt") else null,
         cwd = session.optString("cwd").ifEmpty { null },
         contextTokens =
             if (session.has("contextTokens")) session.getLong("contextTokens") else null,
         maxImageEdge = session.optInt("maxImageEdge", 0).takeIf { it > 0 },
+        usageProvider = session.optString("usageProvider").ifEmpty { null },
         status = session.getString("status"),
         lastActivity = session.getDouble("lastActivity"),
+        subagents = session.optInt("subagents", 0),
     )
 
 fun fetchSessions(settings: ServerSettings): List<SessionSummary> =
@@ -215,6 +276,35 @@ fun fetchSessions(settings: ServerSettings): List<SessionSummary> =
 fun fetchSession(settings: ServerSettings, sessionId: String): SessionSummary =
     requestFromServer(settings, "/sessions/$sessionId") { parseSession(it.jsonObject()) }
 
+/**
+ * One row of `GET /sessions/{id}/subagents`, oldest first.
+ *
+ * A subagent is a second transcript owned by a session -- no process, no controls of its own -- so
+ * this carries only what a card needs to draw and to open it; see SUBAGENTS.md. [status] is
+ * "running", "exited" or "unknown": a subagent whose session is not itself running cannot be
+ * running, and the list says so rather than reporting a state that cannot hold.
+ */
+data class SubagentSummary(
+    val id: String,
+    val title: String,
+    val status: String,
+    val created: Double,
+    val lastActivity: Double,
+)
+
+fun fetchSubagents(settings: ServerSettings, sessionId: String): List<SubagentSummary> =
+    requestFromServer(settings, "/sessions/$sessionId/subagents") {
+        it.jsonObjects { row ->
+            SubagentSummary(
+                id = row.getString("id"),
+                title = row.getString("title"),
+                status = row.getString("status"),
+                created = row.getDouble("created"),
+                lastActivity = row.getDouble("lastActivity"),
+            )
+        }
+    }
+
 // What the server offers, so the spawn screen has no hardcoded lists: a setup added to the server's
 // config.ron appears here with no app rebuild.
 //
@@ -375,6 +465,12 @@ data class SshDetails(
      * Where files attached from here land on that machine; null for the session's own directory.
      */
     val attachmentsDir: String? = null,
+    /**
+     * Where that machine keeps its GGUF models; null for the same place the backend keeps its own
+     * (`~/.local/share/ai-app/models`, read on that machine). A llama.cpp session serves the file
+     * from the machine it runs on, so this is where its models are looked for and listed.
+     */
+    val modelsDir: String? = null,
 )
 
 private fun SshDetails.toJson() =
@@ -382,6 +478,7 @@ private fun SshDetails.toJson() =
         if (port != null) put("port", port)
         if (!identityFile.isNullOrBlank()) put("identityFile", identityFile)
         if (!attachmentsDir.isNullOrBlank()) put("attachmentsDir", attachmentsDir)
+        if (!modelsDir.isNullOrBlank()) put("modelsDir", modelsDir)
     }
 
 /** What a machine turns out to have, without saving anything. */
@@ -450,6 +547,8 @@ fun spawnSession(
     model: String? = null,
     cwd: String? = null,
     permissionMode: String? = null,
+    /** Null for whatever the server's default is; see [fetchDefaultEffort]. */
+    effort: String? = null,
     params: Map<String, String> = emptyMap(),
     /** Continue this Claude Code session instead of starting an empty one. */
     import: String? = null,
@@ -467,6 +566,7 @@ fun spawnSession(
                     if (!model.isNullOrBlank()) put("model", model)
                     if (!cwd.isNullOrBlank()) put("cwd", cwd)
                     if (!permissionMode.isNullOrBlank()) put("permissionMode", permissionMode)
+                    if (!effort.isNullOrBlank()) put("effort", effort)
                     if (!import.isNullOrBlank()) put("import", import)
                     if (params.isNotEmpty()) {
                         put("params", JSONObject(params.toMap<String, Any>()))
@@ -906,7 +1006,7 @@ fun startImport(
  */
 fun fetchTranscript(
     settings: ServerSettings,
-    sessionId: String,
+    address: TranscriptAddress,
     before: Long? = null,
     limit: Int = 80,
     // Count [limit] in rows, not events, joining a reply's streamed deltas into one -- so a page of
@@ -925,7 +1025,7 @@ fun fetchTranscript(
         if (coalesce) append("&coalesce=true")
         if (after != null) append("&after=").append(after)
     }
-    return requestFromServer(settings, "/sessions/$sessionId/transcript$query") { connection ->
+    return requestFromServer(settings, "/${address.urlPath}/transcript$query") { connection ->
         val body = JSONArray(connection.inputStream.bufferedReader().readText())
         // The text as well as the event: the transcript cache stores the one and the fold needs the
         // other, and they have to be the same line.
@@ -973,6 +1073,56 @@ fun setSessionModel(settings: ServerSettings, sessionId: String, model: String)
  */
 val PERMISSION_MODES = listOf("manual", "acceptEdits", "auto", "bypassPermissions", "plan")
 
+/**
+ * What a new session's thinking level is when nothing chose one, or null for the CLI's own.
+ *
+ * Held by the server rather than by this phone, because a second device would otherwise spawn
+ * sessions at a level the first one's owner never picked.
+ */
+fun fetchDefaultEffort(settings: ServerSettings): String? =
+    requestFromServer(settings, "/defaults") {
+        it.jsonObject().optString("effort").ifEmpty { null }
+    }
+
+/** Sets what new sessions start at. Nothing already running changes. */
+fun setDefaultEffort(settings: ServerSettings, level: String?) {
+    requestFromServer(
+        settings,
+        "/defaults",
+        method = "POST",
+        jsonBody = JSONObject().put("effort", level ?: JSONObject.NULL).toString(),
+    ) {}
+}
+
+/**
+ * How hard the model thinks, as `claude --effort` takes them, cheapest first.
+ *
+ * Not offered alongside the model and the permission mode on the session's own bar, because it does
+ * not behave like them: the CLI has a control request for those two and none for this (checked
+ * against 2.1.258), so a level is settled when the process is launched. Changing it therefore stops
+ * the process, which is what the working directory beside it in this dialog does, and why it is
+ * here rather than on a bar whose other controls take effect mid-turn.
+ */
+val EFFORT_LEVELS = listOf("low", "medium", "high", "xhigh", "max")
+
+/** What the picker shows, and sends as null, for a session that has chosen no level. */
+const val DEFAULT_EFFORT = "default"
+
+/**
+ * Records how hard a session thinks and **stops its process**, since the level is read when the
+ * process is launched. The next message, or Start, runs one that has it.
+ *
+ * [level] is null for the CLI's own default.
+ */
+fun setSessionEffort(settings: ServerSettings, sessionId: String, level: String?) {
+    requestFromServer(
+        settings,
+        "/sessions/$sessionId/effort",
+        method = "POST",
+        jsonBody = JSONObject().put("effort", level ?: JSONObject.NULL).toString(),
+    ) {}
+}
+
 /** Switches how much a running session asks before acting, also in place. */
 fun setSessionPermissionMode(settings: ServerSettings, sessionId: String, mode: String) {
     requestFromServer(
@@ -984,6 +1134,36 @@ fun setSessionPermissionMode(settings: ServerSettings, sessionId: String, mode:
 }
 
 /** Turns this session's notifications on or off. Stored on the backend -- see `SessionConfig`. */
+/**
+ * What an auto-resume says when nothing else was typed. Mirrors the server's own default, so a
+ * cleared field shows the word that would actually be sent instead of going blank.
+ */
+const val DEFAULT_RESUME_MESSAGE = "continue"
+
+/**
+ * Turns auto-resume on or off and sets what it would say, in one request because they are one
+ * decision -- see the server's `/sessions/{id}/auto-resume`.
+ */
+fun setSessionAutoResume(
+    settings: ServerSettings,
+    sessionId: String,
+    autoResume: Boolean,
+    message: String?,
+) {
+    requestFromServer(
+        settings,
+        "/sessions/$sessionId/auto-resume",
+        method = "POST",
+        jsonBody =
+            JSONObject()
+                .put("autoResume", autoResume)
+                // Empty means the server's default rather than a session poked with nothing to
+                // read, which is the same rule the server applies to the field.
+                .put("message", message?.trim()?.ifEmpty { null } ?: JSONObject.NULL)
+                .toString(),
+    ) {}
+}
+
 fun setSessionNotify(settings: ServerSettings, sessionId: String, notify: Boolean) {
     requestFromServer(
         settings,
@@ -1074,6 +1254,26 @@ private fun parseDownload(o: JSONObject) =
         error = if (o.has("error")) o.getString("error") else null,
     )
 
+/**
+ * The models on one machine, which is the list a llama.cpp session there can choose from.
+ *
+ * Not [fetchModels], which is what the *backend* has downloaded. A session serves its model from
+ * the machine it runs on, so for a machine reached over ssh those are two different lists -- and
+ * offering the backend's would name files that are not there, turning a choice that cannot work
+ * into a session that fails when it tries to load one.
+ */
+fun fetchSetupModels(settings: ServerSettings, setupId: String): List<LocalModel> =
+    requestFromServer(settings, "/setups/${setupId.urlEncoded()}/models") { connection ->
+        JSONArray(connection.inputStream.bufferedReader().readText()).mapObjects { m ->
+            LocalModel(
+                key = m.getString("key"),
+                repo = m.getString("repo"),
+                file = m.getString("file"),
+                bytes = m.getLong("bytes"),
+            )
+        }
+    }
+
 fun fetchModels(settings: ServerSettings): Models =
     requestFromServer(settings, "/models") { connection ->
         val body = JSONObject(connection.inputStream.bufferedReader().readText())

app/androidApp/src/main/kotlin/com/example/aiapp/AppRoot.kt

@@ -1,7 +1,9 @@
 package com.example.aiapp
 
 import androidx.activity.compose.BackHandler
+import androidx.compose.foundation.background
 import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.imePadding
 import androidx.compose.foundation.layout.padding
 import androidx.compose.material3.AlertDialog
@@ -34,7 +36,23 @@ import kotlinx.coroutines.withContext
  * session, spawning one, and settings.
  */
 private sealed class Screen {
-    data object Main : Screen()
+    /**
+     * The session list, with a subagent's own transcript over it when [subagent] is set.
+     *
+     * A layer on this screen rather than a screen of its own, for the same reason [Session.files]
+     * is: [SessionListScreen] owns which cards are expanded and what each expansion fetched, kept
+     * in `remember`, and a subagent is opened from a card's expander. As a sibling `Screen` it was
+     * disposed and recreated on every return, which lost that state -- an expanded card collapsed
+     * itself the moment its own subagent's view was closed.
+     */
+    data class Main(val subagent: SubagentTarget? = null) : Screen()
+
+    /**
+     * One subagent's own transcript, read-only. See [SessionScreen]'s `subagent` parameter and
+     * SUBAGENTS.md's "Phone". Closing it returns to [Main] under it, not to [Session]: a subagent
+     * is opened from the session list's card rather than from inside the session it belongs to.
+     */
+    data class SubagentTarget(val summary: SessionSummary, val subagent: SubagentSummary)
 
     /**
      * One session, with the file explorer over it when [files] is set.
@@ -81,7 +99,7 @@ fun AppRoot(
     val context = LocalContext.current
     val scope = rememberCoroutineScope()
     var settings by remember(settingsVersion) { mutableStateOf(loadServerSettings(context)) }
-    var screen by remember { mutableStateOf<Screen>(Screen.Main) }
+    var screen by remember { mutableStateOf<Screen>(Screen.Main()) }
     // A notification tap this could not follow, and why. Null both before one is asked for and
     // after one succeeds, since success is a screen rather than a message.
     var failedOpen by remember { mutableStateOf<FailedOpen?>(null) }
@@ -96,7 +114,7 @@ fun AppRoot(
             share = shareRequest
             // A session already open takes it. Otherwise the list is where the choice is made,
             // whatever screen was showing: Spawn and Settings have nowhere to put a file.
-            if (screen !is Screen.Session) screen = Screen.Main
+            if (screen !is Screen.Session) screen = Screen.Main()
         }
     }
 
@@ -123,7 +141,7 @@ fun AppRoot(
                 existing = null,
                 onSaved = { saved ->
                     settings = saved
-                    screen = Screen.Main
+                    screen = Screen.Main()
                 },
                 onBack = null,
             )
@@ -136,7 +154,7 @@ fun AppRoot(
     // shows, so it always refetches.
     val goToMain = {
         reloadToken++
-        screen = Screen.Main
+        screen = Screen.Main()
     }
     if (screen !is Screen.Main) {
         BackHandler(onBack = goToMain)
@@ -185,6 +203,9 @@ fun AppRoot(
                     reloadToken = reloadToken,
                     share = share,
                     onOpen = { screen = Screen.Session(it) },
+                    onOpenSubagent = { summary, subagent ->
+                        screen = here.copy(subagent = Screen.SubagentTarget(summary, subagent))
+                    },
                     onSpawn = { screen = Screen.Spawn },
                     onImported = { imported ->
                         reloadToken++
@@ -192,6 +213,27 @@ fun AppRoot(
                     },
                     onSettings = { screen = Screen.Settings },
                 )
+                // Its own back handler is registered after MainScreen's, so it is the one the
+                // platform asks first while a subagent is open -- the same rule the files
+                // explorer's handler follows over its session, below.
+                here.subagent?.let { target ->
+                    BackHandler { screen = here.copy(subagent = null) }
+                    // Its own opaque background: this screen was always the sole content under
+                    // the theme's own Surface before, so it never had to paint one -- stacked over
+                    // the list here, the space between its own cards let the list underneath show
+                    // through without this. The same fix FilesScreen needed over its session.
+                    Box(Modifier.fillMaxSize().background(MaterialTheme.colorScheme.background)) {
+                        key(target.summary.id, target.subagent.id) {
+                            SessionScreen(
+                                settings = current,
+                                summary = target.summary,
+                                onBack = { screen = here.copy(subagent = null) },
+                                onFiles = {},
+                                subagent = target.subagent,
+                            )
+                        }
+                    }
+                }
             }
         is Screen.Session ->
             // Keyed on the id, because a different session is a different screen rather than this

app/androidApp/src/main/kotlin/com/example/aiapp/BenchFixture.kt

@@ -0,0 +1,108 @@
+package com.example.aiapp
+
+import android.content.Context
+import java.util.concurrent.CopyOnWriteArrayList
+
+/**
+ * P0's benchmark gate (see docs/RUST.md and docs/DECISIONS.md's 2026-09-05 entry): an in-process
+ * fake of the backend, so the `bench` build type can drive a real session screen -- the real
+ * [TranscriptSource], the real fold, the real paging -- with no server and no network permission.
+ *
+ * Only ever installed when [BuildConfig.FIXTURE_MODE] is true (see [MainActivity]); everything else
+ * in this build compiles it in but never calls it, since Kotlin has no per-build-type source set
+ * that both [MainActivity] (which every variant compiles) and this can share without one.
+ *
+ * The design: [requestFromServer] and [Sse] talk to `https://$FIXTURE_HOST:$FIXTURE_PORT` through
+ * ordinary `java.net.URL`, exactly as they would talk to a real server. A
+ * [java.net.URLStreamHandlerFactory] registered once for the whole process intercepts every
+ * `https://` connection to that host and answers from this object's in-memory event log instead of
+ * opening a socket -- see BenchNetwork.kt. Everything above that (TranscriptSource, SessionScreen,
+ * the fold, uniqueItems) never learns the difference.
+ */
+object BenchFixture {
+    const val FIXTURE_HOST = "bench.fixture.invalid"
+    const val FIXTURE_PORT = 1
+
+    /** How many of the fixture's events are the opening backlog; see bench-fixture/README.md. */
+    private const val BACKLOG_COUNT = 3200
+
+    val settings = ServerSettings(FIXTURE_HOST, FIXTURE_PORT, "bench")
+
+    /** The session id every bench run opens; nothing else in this build ever mints one. */
+    const val SESSION_ID = "bench-fixture-session"
+
+    /**
+     * The whole transcript, seq order, growing as [pushLive] is called during the streaming phase.
+     * Read by both the REST page handler and the SSE handler, so a page requested mid- stream and a
+     * live frame agree on what has "already happened" -- the same thing a real server's own
+     * transcript file guarantees.
+     */
+    private val log = CopyOnWriteArrayList<Pair<String, SeqEvent>>()
+
+    /** The events not yet appended to [log] -- the streaming phase's own source. */
+    private var streamTail: List<Pair<String, SeqEvent>> = emptyList()
+
+    private val images = mutableMapOf<String, ByteArray>()
+
+    @Volatile private var loaded = false
+
+    /**
+     * Parses the bundled fixture once. Safe to call more than once; only the first does anything.
+     */
+    @Synchronized
+    fun ensureLoaded(context: Context) {
+        if (loaded) return
+        val lines =
+            context.assets.open("transcript.jsonl").bufferedReader().readLines().filter {
+                it.isNotBlank()
+            }
+        val parsed = lines.map { it to parseSeqEvent(it) }
+        log.addAll(parsed.take(BACKLOG_COUNT))
+        streamTail = parsed.drop(BACKLOG_COUNT)
+        for (name in listOf("bench1.png", "bench2.png")) {
+            images[name] = context.assets.open(name).readBytes()
+        }
+        loaded = true
+    }
+
+    /** The events the streaming phase has left to send. */
+    fun remainingStreamEvents(): Int = streamTail.size
+
+    /** Sends the next fixture event onto the live log, as a real SSE frame would arrive. */
+    fun pushNextLiveEvent(): Boolean {
+        val next = streamTail.firstOrNull() ?: return false
+        streamTail = streamTail.drop(1)
+        log.add(next)
+        return true
+    }
+
+    /** Undoes [pushNextLiveEvent] and reloads the opening backlog, for running the bench twice. */
+    @Synchronized
+    fun resetToBacklog(context: Context) {
+        loaded = false
+        log.clear()
+        ensureLoaded(context)
+    }
+
+    fun fileBytes(name: String): ByteArray? = images[name]
+
+    /**
+     * Raw JSON lines with seq > [after], in order -- what an `/events?after=` connection replays.
+     */
+    fun linesAfter(after: Long): List<String> =
+        log.filter { it.second.seq > after }.map { it.first }
+
+    /**
+     * One REST page: [fetchTranscript]'s `before`/`limit`/`after`, against the growing log. Ignores
+     * `coalesce` -- the fixture's own deltas are already split the way a real reply streams, and
+     * what the benchmark exercises is the fold and the paging, not the server's row-joining, which
+     * client-core's own port tracks separately (CLIENT_CORE.md).
+     */
+    fun page(before: Long?, limit: Int, after: Long?): List<String> {
+        val upper = before ?: (log.lastOrNull()?.second?.seq?.plus(1) ?: 1L)
+        val candidates = log.filter {
+            it.second.seq < upper && (after == null || it.second.seq > after)
+        }
+        return candidates.takeLast(limit).map { it.first }
+    }
+}

app/androidApp/src/main/kotlin/com/example/aiapp/BenchNetwork.kt

@@ -0,0 +1,181 @@
+package com.example.aiapp
+
+import java.io.ByteArrayInputStream
+import java.io.IOException
+import java.io.InputStream
+import java.io.PipedInputStream
+import java.io.PipedOutputStream
+import java.net.HttpURLConnection
+import java.net.URL
+import java.net.URLStreamHandler
+import java.net.URLStreamHandlerFactory
+import java.security.Principal
+import java.security.cert.Certificate
+import javax.net.ssl.HttpsURLConnection
+import javax.net.ssl.SSLPeerUnverifiedException
+import org.json.JSONArray
+
+/**
+ * Installs the process-wide interception [BenchFixture] needs. Idempotent and safe to call more
+ * than once; the JDK only allows [URL.setURLStreamHandlerFactory] to be called successfully once
+ * per process, and a second real call throws -- so this guards it rather than relying on every
+ * caller to remember.
+ *
+ * Scoped to [BenchFixture.FIXTURE_HOST]: any other `https://` URL falls through to the platform's
+ * ordinary handler, so this only ever changes behaviour for the one host the bench build invents.
+ */
+@Synchronized
+fun installFixtureNetworkOnce() {
+    if (installed) return
+    installed = true
+    URL.setURLStreamHandlerFactory(
+        URLStreamHandlerFactory { protocol ->
+            if (protocol != "https") null
+            else
+                object : URLStreamHandler() {
+                    override fun openConnection(url: URL): HttpURLConnection =
+                        if (url.host == BenchFixture.FIXTURE_HOST) FixtureConnection(url)
+                        else
+                        // The bench build makes no other https call -- this factory is
+                        // installed only in FIXTURE_MODE (MainActivity) -- so there is
+                        // deliberately no delegate to a platform handler here: once a
+                        // URLStreamHandlerFactory is installed there is no supported way to
+                        // ask the JDK for its own default handler back, and re-entering this
+                        // same factory for the fallback would recurse forever rather than
+                        // reach one.
+                        throw java.io.IOException(
+                                "bench build's fixture network has no route to https host " +
+                                    "${url.host} -- only ${BenchFixture.FIXTURE_HOST} is served"
+                            )
+                }
+        }
+    )
+}
+
+private var installed = false
+
+/**
+ * Answers one request against [BenchFixture] instead of opening a socket. Implements just enough of
+ * [HttpsURLConnection] for [requestFromServer] and [Sse] to work unmodified: both only call
+ * `connect`/`disconnect`, set a handful of request properties they never need answered, and read
+ * `responseCode` and `inputStream`.
+ */
+private class FixtureConnection(url: URL) : HttpsURLConnection(url) {
+    private var input: InputStream? = null
+    private var writer: Thread? = null
+
+    override fun connect() {
+        if (input != null) return
+        input = route(url.path, url.query)
+    }
+
+    override fun disconnect() {
+        writer?.interrupt()
+        try {
+            input?.close()
+        } catch (_: IOException) {}
+    }
+
+    override fun usingProxy() = false
+
+    override fun getResponseCode(): Int {
+        connect()
+        return 200
+    }
+
+    override fun getInputStream(): InputStream {
+        connect()
+        return input!!
+    }
+
+    override fun getErrorStream(): InputStream? = null
+
+    // Nothing here reads any of these; implemented only because HttpsURLConnection declares them
+    // abstract. A fixture never negotiates real TLS, so each says exactly that rather than
+    // fabricating a plausible-looking certificate.
+    override fun getCipherSuite() = "none (bench fixture, no TLS)"
+
+    override fun getLocalCertificates(): Array<Certificate>? = null
+
+    override fun getServerCertificates(): Array<Certificate> =
+        throw SSLPeerUnverifiedException("bench fixture connection presents no certificate")
+
+    override fun getPeerPrincipal(): Principal =
+        throw SSLPeerUnverifiedException("bench fixture connection presents no certificate")
+
+    override fun getLocalPrincipal(): Principal? = null
+
+    /**
+     * [path] is `/sessions/{id}/...`; everything else this build's fixture is asked for is a bug.
+     */
+    private fun route(path: String, query: String?): InputStream {
+        val params =
+            (query ?: "")
+                .split("&")
+                .filter { it.contains('=') }
+                .associate {
+                    val (k, v) = it.split("=", limit = 2)
+                    k to java.net.URLDecoder.decode(v, "UTF-8")
+                }
+        return when {
+            path.endsWith("/transcript") -> {
+                val lines =
+                    BenchFixture.page(
+                        before = params["before"]?.toLongOrNull(),
+                        limit = params["limit"]?.toIntOrNull() ?: 80,
+                        after = params["after"]?.toLongOrNull(),
+                    )
+                val body = JSONArray(lines.map { org.json.JSONObject(it) })
+                ByteArrayInputStream(body.toString().toByteArray())
+            }
+            path.endsWith("/events") -> openEventsStream(params["after"]?.toLongOrNull() ?: 0L)
+            path.contains("/files/") -> {
+                val name = path.substringAfterLast("/files/")
+                val bytes =
+                    BenchFixture.fileBytes(name)
+                        ?: throw IOException("bench fixture has no file named $name")
+                ByteArrayInputStream(bytes)
+            }
+            else -> throw IOException("bench fixture has no route for $path")
+        }
+    }
+
+    /**
+     * A live SSE body: [BenchFixture.linesAfter] replayed immediately, then polled every 50ms for
+     * anything [BenchFixture.pushNextLiveEvent] has added since -- the same shape a real backend's
+     * backlog-then-follow gives [Sse], just polled instead of woken, which is a fixture's business
+     * rather than something worth a condition variable for.
+     */
+    private fun openEventsStream(after: Long): InputStream {
+        val pipeIn = PipedInputStream(1 shl 16)
+        val pipeOut = PipedOutputStream(pipeIn)
+        var sent = after
+        val thread = Thread {
+            try {
+                while (!Thread.currentThread().isInterrupted) {
+                    val fresh = BenchFixture.linesAfter(sent)
+                    for (line in fresh) {
+                        pipeOut.write("data: $line\n\n".toByteArray())
+                        pipeOut.flush()
+                        sent = org.json.JSONObject(line).getLong("seq")
+                    }
+                    Thread.sleep(50)
+                }
+            } catch (_: InterruptedException) {
+                // disconnect() -- the ordinary way this ends.
+            } catch (_: IOException) {
+                // The reader side (Sse) closed its end.
+            } finally {
+                try {
+                    pipeOut.close()
+                } catch (_: IOException) {}
+            }
+        }
+            .also {
+                it.isDaemon = true
+                it.start()
+            }
+        writer = thread
+        return pipeIn
+    }
+}

app/androidApp/src/main/kotlin/com/example/aiapp/BenchRun.kt

@@ -0,0 +1,325 @@
+package com.example.aiapp
+
+import android.content.Context
+import android.os.BatteryManager
+import android.os.Process
+import android.view.View
+import androidx.compose.foundation.gestures.FlingBehavior
+import androidx.compose.foundation.lazy.LazyListState
+import androidx.compose.ui.focus.FocusRequester
+import androidx.core.view.ViewCompat
+import androidx.core.view.WindowInsetsCompat
+import androidx.core.view.WindowInsetsControllerCompat
+import java.io.File
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.isActive
+import kotlinx.coroutines.launch
+
+/**
+ * P0's scripted benchmark, run in-process instead of by a shell script: the phone has no usable
+ * system tracing (this-machine-android's skill) and no agent can drive it, so the same scroll loop
+ * and streaming phase `transcript-bench.sh`/`stream-bench.sh` drive over `ui-trace` are reproduced
+ * here against [LazyListState] and [BenchFixture] directly. Only reachable from the `bench` build
+ * (see [SessionSettingsDialog]'s `onRunBenchmark`), but compiled into every build for the reason
+ * [BenchFixture]'s doc comment gives.
+ *
+ * **v2 (2026-09-06)**, asked for by Iris because the v1 fling was too gentle to stress-test the
+ * scroll path and said nothing about typing or the keyboard. Four phases now, each a slice of the
+ * same [FrameStats] recording ([FrameStats.markPhase]/[FrameStats.phaseLines] -- one recorder, not
+ * two): **fling** (real `FlingBehavior`, not `animateScrollBy`), **stream** (unchanged from v1),
+ * **type** (600 fixed characters into the real composer `TextFieldValue`, then deleted), and
+ * **keyboard** (five show/hide cycles). The exact constants below are also written into
+ * `docs/RUST.md`'s P0 box, "Benchmark v2 (2026-09-06)", so the iris half implements the identical
+ * spec -- changing a number here without updating that box makes the two apps measure different
+ * things while looking like the same benchmark.
+ */
+object BenchRun {
+    /** transcript-bench.sh's default: 6 cycles of 4 swipes each, kept as the pre-v2 comparison. */
+    private const val CYCLES = 6
+    private const val SWIPE_PX = 900f
+    private const val SWIPE_MS = 200
+    private const val SWIPE_PAUSE_MS = 500L
+
+    /**
+     * Fling phase (v2): a real fling through the list's own [FlingBehavior], not `animateScrollBy`
+     * -- Iris's ask was that it "travel way faster" than the old tween-based swipe, and a tween can
+     * never exceed the distance it is told to cover in the time it is given, while a real fling
+     * decays from an initial velocity the way a finger flick does. 12,000 px/s is roughly a hard,
+     * fast flick on a ~420dp/in device (about 30 dp/ms-equivalent initial speed); chosen well above
+     * the ~4,500 px/s a moderate `animateScrollBy` swipe implies, so this phase exercises the fast
+     * end of what the platform's fling decay produces rather than the gentle one v1 measured.
+     */
+    private const val FLING_VELOCITY_PX_S = 12_000f
+
+    private const val FLING_COUNT = 8
+    private const val FLING_SETTLE_CAP_MS = 3_000L
+    private const val FLING_PAUSE_MS = 300L
+
+    /** stream-bench.sh's shape: a real reply arrives as many small deltas, not one big write. */
+    private const val STREAM_EVENTS_PER_SEC = 20
+    private const val STREAM_SECONDS = 20
+
+    /**
+     * Type phase (v2): sentences built from long, multisyllabic words so the composer actually
+     * wraps across lines rather than fitting one, and long enough (600 chars) that the composer's
+     * own height grows over several frames, pushing the transcript above it upward the same way a
+     * real long message does. Exactly this string is also in `docs/RUST.md`'s P0 box so the iris
+     * half types the identical content.
+     */
+    const val TYPE_TEXT =
+        "Benchmarking this transcript screen requires unusually long, multisyllabic words so " +
+            "wrapping and reflow are properly exercised: internationalization, " +
+            "counterproductiveness, disproportionately, incomprehensibility, " +
+            "deinstitutionalization, uncharacteristically, overenthusiastically, " +
+            "misunderstanding, straightforwardness, telecommunications, and interdisciplinary " +
+            "collaboration all push a narrow composer field to wrap across several lines while " +
+            "the transcript above is pushed upward by the growing keyboard-adjacent box, which " +
+            "is exactly what a real reader typing a long message sees happening now!!!"
+
+    private const val TYPE_CHAR_DELAY_MS = 50L
+
+    /**
+     * Keyboard phase (v2): five show/hide cycles, a second apart, is enough to see whether the
+     * transition is ever actually observed rather than being a one-off fluke either way.
+     */
+    private const val KEYBOARD_CYCLES = 5
+    private const val KEYBOARD_SHOW_WAIT_MS = 1_000L
+    private const val KEYBOARD_HIDE_WAIT_MS = 1_000L
+
+    /**
+     * Scrolls, flings, streams, types and toggles the keyboard, then returns the extra report lines
+     * P0 asked for (per-phase travel/typing/keyboard counts, plus CPU time, peak RSS, battery
+     * current) -- [FrameStats] and [DebugStats] are reset first, exactly as `copyRenderReport`
+     * resets them, so the two accountings cover the same stretch of work.
+     */
+    suspend fun run(
+        context: Context,
+        scope: CoroutineScope,
+        listState: LazyListState,
+        flingBehavior: FlingBehavior,
+        composerFocus: FocusRequester,
+        setComposerText: (String) -> Unit,
+        view: View,
+    ): List<String> {
+        FrameStats.reset()
+        DebugStats.reset()
+        val cpuStartMs = Process.getElapsedCpuTime()
+
+        val battery = BatterySampler(context)
+        // Launched in the caller's scope rather than a fresh coroutineScope{} here, which would
+        // suspend this function until the sampler job ended -- and it only ends when told to.
+        val samplerJob = scope.launch {
+            while (isActive) {
+                battery.sample()
+                delay(1000)
+            }
+        }
+
+        val travel = runFlingPhase(listState, flingBehavior)
+        val sent = runStreamPhase()
+        runTypePhase(listState, composerFocus, setComposerText, view)
+        val keyboard = runKeyboardPhase(context, view)
+
+        samplerJob.cancel()
+        val cpuMs = Process.getElapsedCpuTime() - cpuStartMs
+        val rssLine = peakRssLine()
+        val batteryLine = battery.finish()
+
+        return listOf(
+            "  fling: $FLING_COUNT flings out + $FLING_COUNT back at" +
+                " ${FLING_VELOCITY_PX_S.toInt()}px/s, travel $travel",
+            "  scroll: $CYCLES cycles (${CYCLES * 4} swipes, legacy tween), " +
+                "streamed $sent/${STREAM_EVENTS_PER_SEC * STREAM_SECONDS} fixture events",
+            "  type: ${TYPE_TEXT.length} characters inserted then deleted, one per" +
+                " ${TYPE_CHAR_DELAY_MS}ms",
+            keyboard,
+            "  process CPU time over this run: ${cpuMs}ms",
+            rssLine,
+            batteryLine,
+        )
+    }
+
+    /**
+     * Phase 1: starting pinned at the newest end, [FLING_COUNT] flings away from it (toward older
+     * messages) through the list's real fling path, then [FLING_COUNT] back. Positive velocity here
+     * matches this list's existing scroll-offset convention (`TranscriptList`'s `reverseLayout`
+     * pins index 0 -- the newest item -- at the bottom; a positive scroll offset moves the viewport
+     * toward higher indices, i.e. away from the newest end and toward older content), the same sign
+     * the pre-v2 swipe loop below already used for its first two swipes.
+     */
+    private suspend fun runFlingPhase(
+        listState: LazyListState,
+        flingBehavior: FlingBehavior,
+    ): String {
+        FrameStats.markPhase("fling")
+        listState.scrollToItem(0)
+        val start = position(listState)
+        repeat(FLING_COUNT) {
+            listState.scroll { with(flingBehavior) { performFling(FLING_VELOCITY_PX_S) } }
+            waitForSettle(listState)
+            delay(FLING_PAUSE_MS)
+        }
+        val outward = position(listState)
+        repeat(FLING_COUNT) {
+            listState.scroll { with(flingBehavior) { performFling(-FLING_VELOCITY_PX_S) } }
+            waitForSettle(listState)
+            delay(FLING_PAUSE_MS)
+        }
+        val back = position(listState)
+        return "start=$start outward=$outward end=$back"
+    }
+
+    private fun position(listState: LazyListState) =
+        "idx=${listState.firstVisibleItemIndex}/off=${listState.firstVisibleItemScrollOffset}px"
+
+    /** Belt-and-suspenders on top of `performFling` already suspending until its own decay ends. */
+    private suspend fun waitForSettle(listState: LazyListState) {
+        val startedAt = System.currentTimeMillis()
+        while (
+            listState.isScrollInProgress &&
+                System.currentTimeMillis() - startedAt < FLING_SETTLE_CAP_MS
+        ) {
+            delay(16)
+        }
+    }
+
+    /**
+     * Phase 2 (unchanged from v1): pinned to the newest end before streaming starts, the way
+     * stream-bench.sh's "Jump to latest" tap is -- a reply streamed into a list parked further back
+     * arrives off-screen and the report would show nothing happened.
+     */
+    private suspend fun runStreamPhase(): Int {
+        FrameStats.markPhase("stream")
+        var sent = 0
+        val total = STREAM_EVENTS_PER_SEC * STREAM_SECONDS
+        while (sent < total && BenchFixture.remainingStreamEvents() > 0) {
+            BenchFixture.pushNextLiveEvent()
+            sent++
+            delay(1000L / STREAM_EVENTS_PER_SEC)
+        }
+        // Lets the last few deltas land and draw before the next phase starts.
+        delay(300)
+        return sent
+    }
+
+    /**
+     * Phase 3: focuses the real composer, shows the keyboard if the platform allows it, then types
+     * [TYPE_TEXT] one character at a time through the same `TextFieldValue` state a real keystroke
+     * updates, and deletes it the same way -- this is what exercises wrapping and the transcript
+     * being pushed upward, not a single big write.
+     */
+    private suspend fun runTypePhase(
+        listState: LazyListState,
+        composerFocus: FocusRequester,
+        setComposerText: (String) -> Unit,
+        view: View,
+    ) {
+        FrameStats.markPhase("type")
+        listState.scrollToItem(0)
+        composerFocus.requestFocus()
+        showIme(view.context, view)
+        // Lets focus and the keyboard's opening animation land before typing starts, so the frames
+        // this phase records are the wrap/reflow it is measuring, not the keyboard opening.
+        delay(300)
+        var typed = ""
+        for (ch in TYPE_TEXT) {
+            typed += ch
+            setComposerText(typed)
+            delay(TYPE_CHAR_DELAY_MS)
+        }
+        delay(200)
+        while (typed.isNotEmpty()) {
+            typed = typed.dropLast(1)
+            setComposerText(typed)
+            delay(TYPE_CHAR_DELAY_MS)
+        }
+    }
+
+    /**
+     * Phase 4: [KEYBOARD_CYCLES] show/hide cycles through the same [WindowInsetsControllerCompat]
+     * path a real IME toggle goes through, reporting how many of each were actually confirmed by
+     * [android.view.WindowInsets.isVisible] rather than assumed from having asked -- UI_RULES:
+     * never present an inferred value as a measured one. If the platform never shows it even once,
+     * this says so in words rather than reporting a phase with no keyboard in it.
+     */
+    private suspend fun runKeyboardPhase(context: Context, view: View): String {
+        FrameStats.markPhase("keyboard")
+        var shown = 0
+        var hidden = 0
+        repeat(KEYBOARD_CYCLES) {
+            showIme(context, view)
+            delay(KEYBOARD_SHOW_WAIT_MS)
+            if (imeVisible(view)) shown++
+            hideIme(context, view)
+            delay(KEYBOARD_HIDE_WAIT_MS)
+            if (!imeVisible(view)) hidden++
+        }
+        return if (shown == 0) {
+            "  keyboard: could not be shown ($KEYBOARD_CYCLES attempts, 0 confirmed visible)"
+        } else {
+            "  keyboard: shown $shown/$KEYBOARD_CYCLES, hidden $hidden/$KEYBOARD_CYCLES" +
+                " (confirmed via isImeVisible)"
+        }
+    }
+
+    private fun controller(context: Context, view: View): WindowInsetsControllerCompat? {
+        val window = context.activity()?.window ?: return null
+        return WindowInsetsControllerCompat(window, view)
+    }
+
+    private fun showIme(context: Context, view: View) {
+        controller(context, view)?.show(WindowInsetsCompat.Type.ime())
+    }
+
+    private fun hideIme(context: Context, view: View) {
+        controller(context, view)?.hide(WindowInsetsCompat.Type.ime())
+    }
+
+    private fun imeVisible(view: View): Boolean =
+        ViewCompat.getRootWindowInsets(view)?.isVisible(WindowInsetsCompat.Type.ime()) ?: false
+
+    /** VmHWM from /proc/self/status: the process's high-water mark, in kB, since it started. */
+    private fun peakRssLine(): String {
+        val kb =
+            try {
+                File("/proc/self/status")
+                    .readLines()
+                    .firstOrNull { it.startsWith("VmHWM:") }
+                    ?.trim()
+                    ?.removePrefix("VmHWM:")
+                    ?.trim()
+                    ?.removeSuffix("kB")
+                    ?.trim()
+                    ?.toLongOrNull()
+            } catch (_: Exception) {
+                null
+            }
+        return "  peak RSS: " +
+            (kb?.let { "${it}kB" } ?: "unavailable (/proc/self/status unreadable)")
+    }
+}
+
+/**
+ * Samples [BatteryManager.BATTERY_PROPERTY_CURRENT_NOW] (microamps) once a second for the length of
+ * a run. The property returns `Int.MIN_VALUE` on hardware that does not support it -- most
+ * emulators -- and that is reported as "unavailable" rather than folded into an average with the
+ * real samples, which would silently understate every number after it. See UI_RULES: never present
+ * an inferred value as a measured one.
+ */
+private class BatterySampler(context: Context) {
+    private val manager = context.getSystemService(BatteryManager::class.java)
+    private val samples = mutableListOf<Int>()
+
+    fun sample() {
+        val value = manager?.getIntProperty(BatteryManager.BATTERY_PROPERTY_CURRENT_NOW)
+        if (value != null && value != Int.MIN_VALUE) samples.add(value)
+    }
+
+    fun finish(): String {
+        if (samples.isEmpty()) return "  battery current: unavailable on this device"
+        val meanUa = samples.sum() / samples.size
+        return "  battery current: mean ${meanUa}µA over ${samples.size} samples" +
+            " (min ${samples.min()}, max ${samples.max()})"
+    }
+}

app/androidApp/src/main/kotlin/com/example/aiapp/DebugStats.kt

@@ -127,6 +127,20 @@ fun debugReport(
     frames: List<String>,
     accounting: List<String>,
     crash: String?,
+    /**
+     * P0's benchmark-only measurements (process CPU time, peak RSS, battery current) -- empty on
+     * every path but [BenchRun.runP0Benchmark], which is the only caller that has them. A section
+     * heading only appears when there is something to put under it, so an ordinary copy from the
+     * render-report button reads exactly as it did before this existed.
+     */
+    extra: List<String> = emptyList(),
+    /**
+     * Bench v2's per-phase frame accounting ([FrameStats.phaseLines]) --
+     * fling/stream/type/keyboard, each a slice of the same frames the whole-run sections below
+     * still cover in full. Empty on every path but the scripted bench run, same reasoning as
+     * [extra].
+     */
+    phaseFrames: List<String> = emptyList(),
 ): String = buildString {
     appendLine("ai-app render report")
     appendLine(device)
@@ -141,6 +155,11 @@ fun debugReport(
     appendLine("transcript:")
     transcript.forEach { appendLine(it) }
     appendLine()
+    if (phaseFrames.isNotEmpty()) {
+        appendLine("per phase:")
+        phaseFrames.forEach { appendLine(it) }
+        appendLine()
+    }
     appendLine("frames:")
     frames.forEach { appendLine(it) }
     appendLine()
@@ -152,6 +171,11 @@ fun debugReport(
     appendLine("work since this was last copied:")
     val work = DebugStats.lines()
     if (work.isEmpty()) appendLine("  nothing recorded") else work.forEach { appendLine(it) }
+    if (extra.isNotEmpty()) {
+        appendLine()
+        appendLine("bench:")
+        extra.forEach { appendLine(it) }
+    }
 }
 
 /** Puts [text] on the clipboard under [label], which is what the system offers as its name. */

app/androidApp/src/main/kotlin/com/example/aiapp/Dividers.kt

@@ -12,6 +12,10 @@ import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.unit.dp
+import java.time.Instant
+import java.time.ZoneId
+import java.time.format.DateTimeFormatter
+import java.time.format.FormatStyle
 
 /**
  * A line across the transcript saying what left the session's context.
@@ -47,3 +51,40 @@ fun TranscriptDivider(text: String, color: Color, modifier: Modifier = Modifier)
 fun ClearedRow(modifier: Modifier = Modifier) {
     TranscriptDivider("Context cleared", clearedColor, modifier)
 }
+
+/**
+ * The mark running out of quota leaves.
+ *
+ * The same red the usage bar takes when a window is spent, because it is the same fact in a second
+ * place: colour by consequence, so "there is nothing left to spend" is learned once.
+ *
+ * A time rather than a countdown. The row is folded once and never re-measured, so a span would go
+ * stale on screen the moment it was drawn; and this is when the *account* said it would reset,
+ * which is not a promise about when the session picks back up. A limit the session was told no
+ * reset time for says nothing about one -- that state has its own words rather than a plausible
+ * number.
+ */
+@Composable
+fun LimitRow(item: TranscriptItem.LimitNote, modifier: Modifier = Modifier) {
+    TranscriptDivider(limitSummary(item.resetsAt, ZoneId.systemDefault()), overLimitColor, modifier)
+}
+
+/**
+ * What the row says. Split out so the wording is testable without a screen, since the two states it
+ * has to keep apart -- a reset time that arrived and one that never did -- are exactly the pair
+ * that reads the same when it goes wrong.
+ *
+ * [zone] is a parameter rather than read here so a test says the same thing wherever it runs.
+ */
+fun limitSummary(resetsAt: Double?, zone: ZoneId): String {
+    val at = resetsAt?.let {
+        try {
+            DateTimeFormatter.ofLocalizedTime(FormatStyle.SHORT)
+                .withZone(zone)
+                .format(Instant.ofEpochSecond(it.toLong()))
+        } catch (_: Exception) {
+            null
+        }
+    }
+    return if (at == null) "Usage limit reached" else "Usage limit reached • resets $at"
+}

app/androidApp/src/main/kotlin/com/example/aiapp/EventStream.kt

@@ -14,7 +14,7 @@ private const val RESET_EVENT = "reset"
  * mean. [close] from any thread ends it, and the caller owns reconnecting -- with the last seq it
  * saw as the new cursor.
  */
-class EventStream(settings: ServerSettings, private val sessionId: String) {
+class EventStream(settings: ServerSettings, private val address: TranscriptAddress) {
     private val stream = Sse(settings)
 
     fun close() = stream.close()
@@ -35,7 +35,7 @@ class EventStream(settings: ServerSettings, private val sessionId: String) {
         // one and the screen folds the other, and they have to be the same line.
         onEvent: (raw: String, event: SeqEvent) -> Unit,
     ) {
-        stream.run("/sessions/$sessionId/events?after=$after", onOpen) { name, data ->
+        stream.run("/${address.urlPath}/events?after=$after", onOpen) { name, data ->
             // A named frame carries no payload and a data frame has no name.
             if (name == RESET_EVENT) onReset()
             else if (data.isNotEmpty()) onEvent(data, parseSeqEvent(data))

app/androidApp/src/main/kotlin/com/example/aiapp/Events.kt

@@ -157,6 +157,18 @@ sealed class SessionEvent {
      */
     data object Cleared : SessionEvent()
 
+    /**
+     * The session stopped because its account's usage limit was reached.
+     *
+     * Its own event rather than an [Error] carrying the CLI's sentence, because it is a state
+     * rather than something that went wrong -- and because the raw sentence is `Claude AI usage
+     * limit reached|1788546972`, which is not readable by the person it is shown to.
+     *
+     * [resetsAt] is epoch seconds and null where the session was told nothing. Only the server acts
+     * on it; what this draws it as is a time, not a countdown, because nothing here re-measures it.
+     */
+    data class LimitReached(val resetsAt: Double?) : SessionEvent()
+
     data class Error(val message: String) : SessionEvent()
 
     /**
@@ -261,6 +273,10 @@ fun parseSeqEvent(json: String): SeqEvent {
                     trigger = body.optString("trigger").ifEmpty { null },
                 )
             "cleared" -> SessionEvent.Cleared
+            "limitReached" ->
+                SessionEvent.LimitReached(
+                    if (body.has("resetsAt")) body.getDouble("resetsAt") else null
+                )
             "error" -> SessionEvent.Error(body.getString("message"))
             else -> SessionEvent.Unknown(type)
         }

app/androidApp/src/main/kotlin/com/example/aiapp/FrameStats.kt

@@ -42,6 +42,21 @@ object FrameStats {
     private val gpu = ArrayList<Long>()
     private var since = System.currentTimeMillis()
 
+    /**
+     * Where a named phase of a scripted run (bench v2's fling/stream/type/keyboard) started, as an
+     * index into [total] and a wall-clock time -- not a second recorder, just a mark on this one,
+     * so a phase's frames are the same [FrameMetrics] the whole-run report already has, sliced.
+     */
+    private data class PhaseMark(val name: String, val startIndex: Int, val startMs: Long)
+
+    private val phaseMarks = ArrayList<PhaseMark>()
+
+    /** Call at the start of each named phase of a scripted run; see [BenchRun]. */
+    @Synchronized
+    fun markPhase(name: String) {
+        phaseMarks += PhaseMark(name, total.size, System.currentTimeMillis())
+    }
+
     @Synchronized
     fun add(metrics: FrameMetrics) {
         // The first frame after a window opens includes inflating it and is nobody's scroll.
@@ -69,6 +84,7 @@ object FrameStats {
         listOf(total, waited, input, animation, layout, draw, sync, issue, swap, gpu).forEach {
             it.clear()
         }
+        phaseMarks.clear()
         since = System.currentTimeMillis()
     }
 
@@ -95,6 +111,38 @@ object FrameStats {
         ) + if (gpu.isEmpty()) emptyList() else listOf(phase("gpu   ", gpu))
     }
 
+    /**
+     * One block per [markPhase] call: how many frames landed between that mark and the next (or the
+     * end of the run, for the last one), how many were late, the total/p50/p90/p99, the worst
+     * single frame, and how long the phase actually ran. Marks with no frames between them (a phase
+     * that finished before a frame was drawn) still get a line rather than being silently dropped
+     * -- UI_RULES' "say what you don't know" applies to a phase as much as to a single number.
+     */
+    @Synchronized
+    fun phaseLines(refreshHz: Float): List<String> {
+        if (phaseMarks.isEmpty()) return emptyList()
+        val budget = if (refreshHz > 0) 1000.0 / refreshHz else 16.7
+        val lines = ArrayList<String>()
+        phaseMarks.forEachIndexed { i, mark ->
+            val endIndex = if (i + 1 < phaseMarks.size) phaseMarks[i + 1].startIndex else total.size
+            val endMs =
+                if (i + 1 < phaseMarks.size) phaseMarks[i + 1].startMs
+                else System.currentTimeMillis()
+            val samples = total.subList(mark.startIndex, endIndex)
+            val seconds = (endMs - mark.startMs) / 1000.0
+            lines += "  ${mark.name}: ${samples.size} frames over ${"%.1f".format(seconds)}s"
+            if (samples.isEmpty()) {
+                lines += "    no frames recorded in this phase"
+            } else {
+                val late = samples.count { it / 1_000_000.0 > budget }
+                lines += "    late: $late (${percent(late, samples.size)})"
+                lines += "    " + phase("total ", samples)
+                lines += "    worst ${"%.1fms".format(samples.max() / 1_000_000.0)}"
+            }
+        }
+        return lines
+    }
+
     /** How long the frames recorded here spent in their draw phase, and how many there were. */
     @Synchronized fun drawPhase(): Pair<Long, Int> = draw.sum() to draw.size
 

app/androidApp/src/main/kotlin/com/example/aiapp/MainActivity.kt

@@ -66,6 +66,35 @@ class MainActivity : ComponentActivity() {
         // Transparent status bar on every version; the Surface below paints through underneath it
         // and content insets itself. Same reasoning as dev-updater's MainActivity.
         enableEdgeToEdge()
+
+        // The `bench` build's entire purpose (P0, docs/RUST.md): open straight onto the session
+        // screen against BenchFixture's in-process fake backend, with no enrollment, no network
+        // permission, and no notification prompt -- none of them mean anything with no server and
+        // no real device to notify. See BenchFixture.kt and BenchNetwork.kt for how a screen built
+        // to talk to a real backend is made to talk to this instead. Still needs the same
+        // status/navigation-bar padding the ordinary flow below applies: edge-to-edge is the
+        // platform's own default from Android 15 on this app's targetSdk, with or without the call
+        // above, so skipping the padding here put the header's own buttons under the status bar --
+        // there to look at, but not there for `ui-trace`'s tap-by-label to land on.
+        if (BuildConfig.FIXTURE_MODE) {
+            installFixtureNetworkOnce()
+            BenchFixture.ensureLoaded(this)
+            setContent {
+                MaterialTheme(colorScheme = AiAppColors) {
+                    Surface(modifier = Modifier.fillMaxSize()) {
+                        Box(Modifier.fillMaxSize().statusBarsPadding().navigationBarsPadding()) {
+                            SessionScreen(
+                                settings = BenchFixture.settings,
+                                summary = benchSessionSummary(),
+                                onBack = { finish() },
+                                onFiles = {},
+                            )
+                        }
+                    }
+                }
+            }
+            return
+        }
         // Dark status-bar icons only over a light background, decided from the scheme rather than
         // fixed. It was hardcoded to `true`, which was right against the default light surface and
         // became unreadable the moment the app wore Catppuccin Mocha.
@@ -147,6 +176,33 @@ class MainActivity : ComponentActivity() {
         }
     }
 
+    /** The one session the `bench` build ever shows -- BenchFixture's session id, nothing else. */
+    private fun benchSessionSummary() =
+        SessionSummary(
+            id = BenchFixture.SESSION_ID,
+            setup = "bench",
+            setupName = "bench",
+            provider = "bench",
+            title = "P0 benchmark",
+            model = null,
+            keepsOwnTranscript = false,
+            permissionMode = null,
+            effort = null,
+            takesEffort = false,
+            imported = false,
+            notify = false,
+            autoResume = false,
+            autoResumeMessage = "",
+            resumeAt = null,
+            cwd = null,
+            contextTokens = null,
+            maxImageEdge = null,
+            usageProvider = null,
+            status = "idle",
+            lastActivity = 0.0,
+            subagents = 0,
+        )
+
     // launchMode="singleTop": an enrollment scan, or a notification tapped while the app is open,
     // lands here rather than in a second activity instance.
     override fun onNewIntent(intent: Intent) {

app/androidApp/src/main/kotlin/com/example/aiapp/MainScreen.kt

@@ -48,6 +48,8 @@ fun MainScreen(
     /** What another app shared in and no session has taken yet; see [ShareRequest]. */
     share: ShareRequest? = null,
     onOpen: (SessionSummary) -> Unit,
+    /** Opens one session's subagent, from the expander under its card. */
+    onOpenSubagent: (SessionSummary, SubagentSummary) -> Unit,
     onSpawn: () -> Unit,
     onImported: (SessionSummary) -> Unit,
     onSettings: () -> Unit,
@@ -139,6 +141,7 @@ fun MainScreen(
                     settings = settings,
                     reloadToken = token,
                     onOpen = onOpen,
+                    onOpenSubagent = onOpenSubagent,
                     onSpawn = onSpawn,
                 )
             MainTab.Import ->

app/androidApp/src/main/kotlin/com/example/aiapp/SessionListScreen.kt

@@ -1,7 +1,9 @@
 package com.example.aiapp
 
 import androidx.compose.foundation.ExperimentalFoundationApi
+import androidx.compose.foundation.clickable
 import androidx.compose.foundation.combinedClickable
+import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
@@ -9,6 +11,7 @@ import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.heightIn
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.lazy.LazyColumn
@@ -17,6 +20,7 @@ import androidx.compose.material3.Card
 import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.material3.FloatingActionButton
 import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedCard
 import androidx.compose.material3.Switch
 import androidx.compose.material3.Text
 import androidx.compose.material3.TextButton
@@ -30,6 +34,8 @@ import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.semantics.contentDescription
+import androidx.compose.ui.semantics.semantics
 import androidx.compose.ui.unit.dp
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
@@ -47,12 +53,40 @@ fun SessionListScreen(
     settings: ServerSettings,
     reloadToken: Int,
     onOpen: (SessionSummary) -> Unit,
+    /** Opens one session's subagent, from the expander under its card. */
+    onOpenSubagent: (SessionSummary, SubagentSummary) -> Unit,
     onSpawn: () -> Unit,
 ) {
     val scope = rememberCoroutineScope()
     var listState by remember { mutableStateOf<LoadState<List<SessionSummary>>>(LoadState.Loading) }
     var confirmingDelete by remember { mutableStateOf<SessionSummary?>(null) }
 
+    // Which session cards are expanded to show their subagents, and what each expansion fetched.
+    // Ids rather than a flag on the row for the same reason `deleting` is: the rows are rebuilt
+    // from
+    // whatever the server last said, and this belongs to the reader's own choice, which survives a
+    // refresh.
+    var expandedSessions by remember { mutableStateOf(setOf<String>()) }
+    var subagentLoads by remember {
+        mutableStateOf(mapOf<String, LoadState<List<SubagentSummary>>>())
+    }
+
+    fun loadSubagents(sessionId: String) {
+        subagentLoads = subagentLoads + (sessionId to LoadState.Loading)
+        scope.launch {
+            subagentLoads =
+                subagentLoads +
+                    (sessionId to
+                        try {
+                            LoadState.Loaded(
+                                withContext(Dispatchers.IO) { fetchSubagents(settings, sessionId) }
+                            )
+                        } catch (e: ApiException) {
+                            LoadState.failed(e)
+                        })
+        }
+    }
+
     // Failures that belong to one session rather than to the list, keyed by its id and shown on its
     // own card. The two scopes are decided by whether the server answered: it answered and refused,
     // so this says nothing about the other rows.
@@ -84,6 +118,14 @@ fun SessionListScreen(
                     withContext(Dispatchers.IO) {
                         transcriptCache.retainOnly(loaded.value.map { it.id }.toSet())
                     }
+                    // A session gone from this answer cannot still be expanded, and an expanded one
+                    // that is still here asks again -- its subagents may have changed since the
+                    // last
+                    // fetch.
+                    val ids = loaded.value.map { it.id }.toSet()
+                    expandedSessions = expandedSessions intersect ids
+                    subagentLoads = subagentLoads.filterKeys { it in ids }
+                    expandedSessions.forEach(::loadSubagents)
                     loaded
                 } catch (e: ApiException) {
                     LoadState.failed(e)
@@ -127,6 +169,17 @@ fun SessionListScreen(
                                 deleting = session.id in deleting,
                                 onOpen = { onOpen(session) },
                                 onLongPress = { confirmingDelete = session },
+                                expanded = session.id in expandedSessions,
+                                subagents = subagentLoads[session.id],
+                                onToggleSubagents = {
+                                    if (session.id in expandedSessions) {
+                                        expandedSessions = expandedSessions - session.id
+                                    } else {
+                                        expandedSessions = expandedSessions + session.id
+                                        loadSubagents(session.id)
+                                    }
+                                },
+                                onOpenSubagent = { subagent -> onOpenSubagent(session, subagent) },
                             )
                             Spacer(Modifier.height(12.dp))
                         }
@@ -225,7 +278,7 @@ fun SessionListScreen(
                                     deleteSession(settings, session.id, alsoDeleteForeign)
                                     // After it succeeded, not before: a refused delete leaves the
                                     // session exactly as it was, and its transcript with it.
-                                    transcriptCache.session(session.id).purge()
+                                    transcriptCache.session(TranscriptAddress(session.id)).purge()
                                 }
                                 // Only this row, and only what changed. Refetching the list instead
                                 // put every other session back through loading and handed the
@@ -276,6 +329,12 @@ private fun SessionCard(
     deleting: Boolean,
     onOpen: () -> Unit,
     onLongPress: () -> Unit,
+    /** Whether the expander below is open. Collapsed by default; see [SessionListScreen]. */
+    expanded: Boolean,
+    /** What the expander's own fetch answered, or null before it has been asked. */
+    subagents: LoadState<List<SubagentSummary>>?,
+    onToggleSubagents: () -> Unit,
+    onOpenSubagent: (SubagentSummary) -> Unit,
 ) {
     BusyItem(label = if (deleting) "deleting" else null) {
         Card(
@@ -332,11 +391,105 @@ private fun SessionCard(
                         color = MaterialTheme.colorScheme.error,
                     )
                 }
+                // Nothing at all for a card with no subagents: a disabled expander here would be
+                // noise on every ordinary session's card. Its own row at the bottom rather than
+                // beside the title or the machine line, so opening it never displaces text that was
+                // already on screen -- see UI_RULES on a control not displacing the text beside it.
+                if (session.subagents > 0) {
+                    Spacer(Modifier.height(8.dp))
+                    // The platform's minimum touch height, not the chevron's own ten or so dp:
+                    // at the chevron's height a tap meant for it landed on the first subcard
+                    // beneath and opened a subagent instead.
+                    Row(
+                        horizontalArrangement = Arrangement.Center,
+                        verticalAlignment = Alignment.CenterVertically,
+                        modifier =
+                            Modifier.fillMaxWidth()
+                                .heightIn(min = 48.dp)
+                                .clickable(enabled = !deleting, onClick = onToggleSubagents)
+                                .semantics {
+                                    contentDescription =
+                                        if (expanded) "Collapse subagents" else "Expand subagents"
+                                },
+                    ) {
+                        Chevron(if (expanded) Pointing.Up else Pointing.Down)
+                    }
+                    if (expanded) {
+                        Spacer(Modifier.height(4.dp))
+                        Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                            when (subagents) {
+                                null,
+                                is LoadState.Loading ->
+                                    CircularProgressIndicator(
+                                        modifier = Modifier.width(20.dp).height(20.dp),
+                                        strokeWidth = 2.dp,
+                                    )
+                                is LoadState.Error ->
+                                    // Said here rather than left silent: a fetch that failed and an
+                                    // expander that simply found nothing must not look the same --
+                                    // see UI_RULES on designing the unknown state first.
+                                    Text(
+                                        subagents.message,
+                                        style = MaterialTheme.typography.bodySmall,
+                                        color = MaterialTheme.colorScheme.error,
+                                    )
+                                is LoadState.Loaded ->
+                                    subagents.value.forEach { subagent ->
+                                        SubagentCard(
+                                            subagent,
+                                            onClick = { onOpenSubagent(subagent) },
+                                        )
+                                    }
+                            }
+                        }
+                    }
+                }
             }
         }
     }
 }
 
+/**
+ * One subagent, indented inside its session's card -- the way dev-updater draws a project's
+ * components (`ComponentCard`, `UpdaterScreen.kt`): an outlined card, not the session card's own
+ * filled one, so the nesting reads as one step rather than as another session.
+ */
+@Composable
+private fun SubagentCard(subagent: SubagentSummary, onClick: () -> Unit) {
+    OutlinedCard(Modifier.fillMaxWidth().clickable(onClick = onClick)) {
+        Column(Modifier.padding(horizontal = 12.dp, vertical = 8.dp)) {
+            Text(subagent.title, style = MaterialTheme.typography.titleSmall)
+            Spacer(Modifier.height(2.dp))
+            Row(modifier = Modifier.fillMaxWidth()) {
+                Text(
+                    subagentStatusLabel(subagent.status),
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    modifier = Modifier.weight(1f),
+                )
+                Text(
+                    relativeTime(subagent.lastActivity),
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant,
+                )
+            }
+        }
+    }
+}
+
+/**
+ * The subcard's word for a subagent's status -- see SUBAGENTS.md's "Wire shape". Its own function
+ * rather than a branch inside [StatusText], because a subagent's three states are not that
+ * composable's five: "exited" reads as "finished" here, since its process was always its parent's
+ * and never something of its own to have merely stopped.
+ */
+private fun subagentStatusLabel(status: String) =
+    when (status) {
+        "running" -> "running"
+        "exited" -> "finished"
+        else -> "unknown"
+    }
+
 @Composable
 fun StatusText(status: String) {
     val (label, color) =

app/androidApp/src/main/kotlin/com/example/aiapp/SessionScreen.kt

@@ -12,6 +12,7 @@ import androidx.activity.result.PickVisualMediaRequest
 import androidx.activity.result.contract.ActivityResultContracts
 import androidx.compose.foundation.background
 import androidx.compose.foundation.clickable
+import androidx.compose.foundation.gestures.ScrollableDefaults
 import androidx.compose.foundation.gestures.awaitEachGesture
 import androidx.compose.foundation.gestures.awaitFirstDown
 import androidx.compose.foundation.layout.Box
@@ -64,12 +65,15 @@ import androidx.compose.runtime.snapshots.Snapshot
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.drawWithContent
+import androidx.compose.ui.focus.FocusRequester
+import androidx.compose.ui.focus.focusRequester
 import androidx.compose.ui.graphics.graphicsLayer
 import androidx.compose.ui.input.pointer.PointerEventPass
 import androidx.compose.ui.input.pointer.pointerInput
 import androidx.compose.ui.layout.onSizeChanged
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.platform.LocalDensity
+import androidx.compose.ui.platform.LocalView
 import androidx.compose.ui.semantics.contentDescription
 import androidx.compose.ui.semantics.semantics
 import androidx.compose.ui.text.TextRange
@@ -216,16 +220,33 @@ fun SessionScreen(
     share: ShareRequest? = null,
     /** Said once [share] has been attached here, so it is not attached again. */
     onShareTaken: () -> Unit = {},
+    /**
+     * Draws this screen read-only, on a subagent's own transcript instead of the session's.
+     *
+     * A subagent has no process and no controls of its own -- see SUBAGENTS.md's "Phone" -- so
+     * every gate below keyed on this switches off the composer, the files button, the settings cog,
+     * the usage bar and notifications, while everything that draws a transcript (paging, cache,
+     * selection, images, the status row, stream reconnects) is reused unchanged, pointed at
+     * [address] instead of the session's own.
+     */
+    subagent: SubagentSummary? = null,
 ) {
     DebugStats.count("session screen recomposed")
+    val isSubagent = subagent != null
+    val address = TranscriptAddress(summary.id, subagent?.id)
     val scope = rememberCoroutineScope()
     val topEdgeHeld = remember { TopEdgeHold() }
     var items by remember { mutableStateOf(listOf<TranscriptItem>()) }
-    var status by remember { mutableStateOf(summary.status) }
+    var status by remember { mutableStateOf(subagent?.status ?: summary.status) }
     // Seeded from the row this screen was opened from, so a conversation already under way says how
     // much it is holding before any turn happens here. Null is "nobody has measured it", which is a
     // different answer from an empty context and is drawn differently.
-    var contextTokens by remember(summary.id) { mutableStateOf(summary.contextTokens) }
+    //
+    // A subagent has no context measurement of its own, so it always starts unmeasured rather than
+    // borrowing the parent session's figure -- see UI_RULES on not showing an inferred value as one
+    // that was measured.
+    var contextTokens by
+        remember(address) { mutableStateOf(if (isSubagent) null else summary.contextTokens) }
     // When the current compaction started. The moment comes off the `compacting` status event
     // itself -- the server timestamps every transcript line -- rather than off this device noticing
     // one, which is what makes it survive leaving the session and reopening it.
@@ -241,7 +262,13 @@ fun SessionScreen(
     val context = LocalContext.current
     // Seeded from what was left in the box last time and written back on every keystroke, so
     // leaving the screen does not throw away a half-typed message. See `Drafts.kt`.
-    var input by remember(summary.id) { mutableStateOf(atEnd(loadDraft(context, summary.id))) }
+    //
+    // A subagent has no box to type into, so it never touches a draft at all -- not this session's,
+    // which is what reading one keyed only by `summary.id` would do here.
+    var input by
+        remember(summary.id) {
+            mutableStateOf(if (isSubagent) atEnd("") else atEnd(loadDraft(context, summary.id)))
+        }
     // A model the reader has chosen and not yet confirmed. See [ModelSwitchWarning]: switching
     // makes the session re-read the whole conversation.
     var pendingModel by remember { mutableStateOf<String?>(null) }
@@ -294,27 +321,26 @@ fun SessionScreen(
     // Reload throws away what it was reading from.
     val cache = remember(settings) { TranscriptCache(cacheRoot(context, settings)) }
     val source =
-        remember(summary.id, epoch) {
-            TranscriptSource(settings, summary.id, cache.session(summary.id))
-        }
+        remember(address, epoch) { TranscriptSource(settings, address, cache.session(address)) }
     // Whether the cached tail has been shown to still be the server's own line. Nothing is resumed
     // from a cached cursor until it has, and a probe that could not be made leaves this false for
     // the stream loop to try again.
-    var probePassed by remember(summary.id, epoch) { mutableStateOf(false) }
+    var probePassed by remember(address, epoch) { mutableStateOf(false) }
     // Whether the opening effect is still settling that question. It draws the cached rows and
     // lifts [ready] before the answer arrives, which is the point of the cache -- so the stream
     // below waits for this rather than for `ready`, or it asks the same question twice.
-    var probing by remember(summary.id, epoch) { mutableStateOf(true) }
+    var probing by remember(address, epoch) { mutableStateOf(true) }
     // The oldest sequence number loaded, and whether there is more behind it. Paging backwards is
     // what keeps opening a long session cheap.
     var oldestSeq by remember { mutableLongStateOf(0L) }
-    // Where this session was last being read, from this device's own store. Read once, because the
-    // answer stops being interesting the moment the list is on screen.
-    val savedAnchor = remember(summary.id, epoch) { loadScrollAnchor(context, summary.id) }
+    // Where this transcript was last being read, from this device's own store, keyed by the address
+    // rather than the session id so a subagent's saved position cannot collide with its session's.
+    // Read once, because the answer stops being interesting the moment the list is on screen.
+    val savedAnchor = remember(address, epoch) { loadScrollAnchor(context, address.cachePath) }
     // Whether the saved position is still being put back. Nothing is drawn while it is: opening at
     // the newest end and then travelling to the anchor is exactly the journey a reader must never
     // see.
-    var restoring by remember(summary.id, epoch) { mutableStateOf(savedAnchor != null) }
+    var restoring by remember(address, epoch) { mutableStateOf(savedAnchor != null) }
     // Messages the server has taken and the session has not read yet, by the id that will resolve
     // them. From the event stream rather than from what this screen sent, so they survive leaving
     // the session -- and a message sent from another device is drawn waiting on this one too.
@@ -327,11 +353,22 @@ fun SessionScreen(
     var loadingHistory by remember { mutableStateOf(false) }
     var ready by remember { mutableStateOf(false) }
     // Replies parsed ahead of the rows that draw them; see [ParsedReplies].
-    val replies = remember(summary.id) { ParsedReplies() }
-    // Keyed like everything else describing one session's transcript. `rememberLazyListState` saves
-    // through `rememberSaveable`, and this screen restores by its own anchor instead -- two
-    // restores would fight over the first frame.
-    val listState = remember(summary.id) { LazyListState() }
+    val replies = remember(address) { ParsedReplies() }
+    // Keyed like everything else describing one transcript. `rememberLazyListState` saves through
+    // `rememberSaveable`, and this screen restores by its own anchor instead -- two restores would
+    // fight over the first frame.
+    val listState = remember(address) { LazyListState() }
+    // The list's own fling path -- what a real flick decays through -- captured here so BenchRun's
+    // fling phase can drive `LazyListState.scroll` through exactly the `FlingBehavior` this
+    // screen's
+    // `TranscriptList` already uses by not overriding it (its `LazyColumn` takes no `flingBehavior`
+    // argument, so this is the same default it gets).
+    val flingBehavior = ScrollableDefaults.flingBehavior()
+    // Where BenchRun's type phase focuses before it types, and the view it toggles the keyboard on
+    // -- both bench-only, but cheap enough (a remembered object, a CompositionLocal read) to hold
+    // unconditionally rather than behind a second code path only the bench build compiles.
+    val composerFocus = remember { FocusRequester() }
+    val view = LocalView.current
     // Whether the newest message is on screen right now. The list is reversed, so the newest end is
     // the scrolling start: nothing behind you is exactly being at the bottom. Asked of the scroll
     // state rather than of item indices, because a zero-height first item makes an index ambiguous.
@@ -637,7 +674,7 @@ fun SessionScreen(
     // ended and carries live events only. The window comes from this phone's own copy when there is
     // one, and then costs a single request to check that the server's transcript is still the one
     // it came from. See TRANSCRIPT_CACHE.md.
-    LaunchedEffect(summary.id, epoch) {
+    LaunchedEffect(address, epoch) {
         /**
          * One opening window onto the screen, whichever side it came from.
          *
@@ -667,11 +704,16 @@ fun SessionScreen(
                 // A replay is as old as the last visit; the row this screen was opened from was
                 // fetched moments ago. So the transcript comes from the cache and everything that
                 // is not the transcript comes from the summary -- otherwise a session that finished
-                // an hour ago opens saying "working" until the stream connects.
-                status = summary.status
-                model = summary.model
-                permissionMode = summary.permissionMode ?: "auto"
-                if (summary.status != "compacting") compactingSince = null
+                // an hour ago opens saying "working" until the stream connects. A subagent's status
+                // comes from its own summary, never the parent session's: they are two different
+                // things running or not, and the parent's model and permission mode do not apply to
+                // it at all.
+                status = subagent?.status ?: summary.status
+                if (!isSubagent) {
+                    model = summary.model
+                    permissionMode = summary.permissionMode ?: "auto"
+                }
+                if (status != "compacting") compactingSince = null
                 // Nothing to put back, so these rows are the screen and the probe can return under
                 // them. A restore still has history to fetch and is gated below.
                 if (savedAnchor == null) ready = true
@@ -798,7 +840,7 @@ fun SessionScreen(
     // at the top on their return. Switching apps is a choice somebody made, not a fault to report.
     // Stopping the stream deliberately makes the drop a close rather than an error, and resuming
     // reconnects from the same cursor.
-    LaunchedEffect(summary.id, ready, epoch, lifecycleOwner) {
+    LaunchedEffect(address, ready, epoch, lifecycleOwner) {
         if (!ready) return@LaunchedEffect
         // The opening effect draws cached rows and lifts `ready` *before* it has checked that the
         // cursor under them is still the server's, so `ready` is no longer the whole gate. Without
@@ -868,17 +910,22 @@ fun SessionScreen(
     // The screen going away entirely, which the lifecycle scope above does not cover: a composable
     // can leave the composition while the activity stays started. Keyed on the epoch as well, so
     // Reload's replacement source is the one a later disposal closes.
-    DisposableEffect(summary.id, epoch) { onDispose { source.close() } }
+    DisposableEffect(address, epoch) { onDispose { source.close() } }
 
     // Nothing gets announced about the session somebody is reading; see NotificationService.
     // RESUMED rather than STARTED because "looking at it" means the foreground.
-    LaunchedEffect(summary.id, lifecycleOwner) {
-        lifecycleOwner.repeatOnLifecycle(Lifecycle.State.RESUMED) {
-            NotificationService.showing(context, summary.id)
-            try {
-                awaitCancellation()
-            } finally {
-                NotificationService.stoppedShowing(summary.id)
+    //
+    // Not for a subagent: it has no notifications of its own, and it is not the session this would
+    // otherwise mark as being read.
+    if (!isSubagent) {
+        LaunchedEffect(summary.id, lifecycleOwner) {
+            lifecycleOwner.repeatOnLifecycle(Lifecycle.State.RESUMED) {
+                NotificationService.showing(context, summary.id)
+                try {
+                    awaitCancellation()
+                } finally {
+                    NotificationService.stoppedShowing(summary.id)
+                }
             }
         }
     }
@@ -924,7 +971,7 @@ fun SessionScreen(
                 val (index, offset, awayFromNewest) = settled
                 saveScrollAnchor(
                     context,
-                    summary.id,
+                    address.cachePath,
                     // Nothing to restore at the newest end, which is where a session with no anchor
                     // opens anyway. One *before* the index, because item zero is the "below" slot.
                     if (!awayFromNewest) null
@@ -947,7 +994,7 @@ fun SessionScreen(
     //
     // There is no correction beside this one. Following the newest message is not an effect: the
     // list is reversed, so an arriving message extends the end the viewport is pinned to.
-    val unitSizes = remember(summary.id) { HashMap<Any, Int>() }
+    val unitSizes = remember(address) { HashMap<Any, Int>() }
     LaunchedEffect(listState, moreHistory) {
         snapshotFlow { listState.layoutInfo }
             .collect { info ->
@@ -983,21 +1030,25 @@ fun SessionScreen(
             }
     }
 
-    LaunchedEffect(summary.setupName, summary.provider) {
-        offeredModels =
-            try {
-                withContext(Dispatchers.IO) {
-                    fetchSetups(settings)
-                        .firstOrNull { it.name == summary.setupName }
-                        ?.providers
-                        ?.firstOrNull { it.name == summary.provider }
-                        ?.models
-                        .orEmpty()
+    // Only for the model picker, which a subagent does not have.
+    if (!isSubagent) {
+        LaunchedEffect(summary.setupName, summary.provider) {
+            offeredModels =
+                try {
+                    withContext(Dispatchers.IO) {
+                        fetchSetups(settings)
+                            .firstOrNull { it.name == summary.setupName }
+                            ?.providers
+                            ?.firstOrNull { it.name == summary.provider }
+                            ?.models
+                            .orEmpty()
+                    }
+                } catch (_: Exception) {
+                    // Not worth reporting: the picker simply has nothing to offer, which is
+                    // visible.
+                    emptyList()
                 }
-            } catch (_: Exception) {
-                // Not worth reporting: the picker simply has nothing to offer, which is visible.
-                emptyList()
-            }
+        }
     }
 
     /**
@@ -1148,8 +1199,9 @@ fun SessionScreen(
     }
 
     // One poll for the machines' limits, read by everything on this screen that reports them.
-    val usageFeed = rememberUsageFeed(settings)
-    val usage = usageFeed.forSetup(summary.setup)
+    // Nothing meters a subagent -- it has no account of its own -- so it never starts this poll.
+    val usageFeed = if (isSubagent) null else rememberUsageFeed(settings)
+    val usage = usageFeed?.forSession(summary) ?: SessionUsage.NotMetered
     RecordFrames()
     var usageOpen by remember { mutableStateOf(false) }
     var settingsOpen by remember { mutableStateOf(false) }
@@ -1191,7 +1243,12 @@ fun SessionScreen(
     // the bench scripts keep working when this moves again. They pressed it at a hand-measured
     // coordinate until 2026-09-03, and anything that moved the header made that tap land on
     // whatever now sat there -- reporting a number that was never measured.
-    val copyRenderReport = {
+    // Shared by the ordinary "Copy" button and (bench build only) "Run benchmark": what differs
+    // between them is only whether there is a [extra] section, built by BenchRun.run beforehand --
+    // everything about assembling, copying and logging the report is exactly the same act either
+    // way, and a second copy of it beside `onRunBenchmark` below would be the two silently
+    // disagreeing about what "the report" contains the first time either one changed.
+    fun buildAndCopyReport(extra: List<String> = emptyList()) {
         val report =
             debugReport(
                 device =
@@ -1213,6 +1270,11 @@ fun SessionScreen(
                 accounting =
                     FrameStats.drawPhase().let { (nanos, count) -> drawAccounting(nanos, count) },
                 crash = lastCrash(context),
+                extra = extra,
+                // Empty outside a BenchRun.run pass -- copyRenderReport's own reset below clears
+                // the
+                // marks along with everything else, so an ordinary copy never has any to show.
+                phaseFrames = FrameStats.phaseLines(context.refreshHz()),
             )
         context.copyToClipboard("ai-app render report", report)
         // Also to the log, so a session driving the app over adb can read the same report the
@@ -1226,6 +1288,29 @@ fun SessionScreen(
         DebugStats.reset()
         Toast.makeText(context, "Copied render report", Toast.LENGTH_SHORT).show()
     }
+    val copyRenderReport = { buildAndCopyReport() }
+    // Bench build only: P0's scripted fling/stream/type/keyboard benchmark (BenchRun.kt), against
+    // the fixture session opened below instead of a real server. Null everywhere else -- see
+    // [SessionSettingsDialog]'s onRunBenchmark.
+    val runBenchmark: (() -> Unit)? =
+        if (BuildConfig.FIXTURE_MODE) {
+            {
+                settingsOpen = false
+                scope.launch {
+                    val extra =
+                        BenchRun.run(
+                            context = context,
+                            scope = scope,
+                            listState = listState,
+                            flingBehavior = flingBehavior,
+                            composerFocus = composerFocus,
+                            setComposerText = { text -> input = atEnd(text) },
+                            view = view,
+                        )
+                    buildAndCopyReport(extra)
+                }
+            }
+        } else null
     Box(Modifier.fillMaxSize()) {
         Column(Modifier.fillMaxSize()) {
             Row(
@@ -1236,20 +1321,35 @@ fun SessionScreen(
                 // A ring's worth, which is what the arrow already keeps on its other three sides.
                 Spacer(Modifier.width(GLYPH_BUTTON_MARGIN))
                 Column(Modifier.weight(1f)) {
-                    Text(title, style = MaterialTheme.typography.titleMedium)
-                    // Machine first, then what runs on it -- the same order and the same wording
-                    // everywhere this pair appears, so it reads as one fact rather than two
-                    // sentences with different grammar.
-                    //
-                    // No model. The picker in the footer already shows what this session is set to,
-                    // and showing it twice means two things to keep in step -- they disagreed for a
-                    // moment on every model change.
-                    Text(
-                        "${summary.setupName} · ${summary.provider}",
-                        style = MaterialTheme.typography.bodySmall,
-                        color = MaterialTheme.colorScheme.onSurfaceVariant,
-                    )
+                    // A subagent's own title, with the session's beneath it in a smaller style --
+                    // the header says whose conversation this is as well as what it is. Otherwise
+                    // just the session's title, as before.
+                    if (subagent != null) {
+                        Text(subagent.title, style = MaterialTheme.typography.titleMedium)
+                        Text(
+                            title,
+                            style = MaterialTheme.typography.bodySmall,
+                            color = MaterialTheme.colorScheme.onSurfaceVariant,
+                        )
+                    } else {
+                        Text(title, style = MaterialTheme.typography.titleMedium)
+                        // Machine first, then what runs on it -- the same order and the same
+                        // wording everywhere this pair appears, so it reads as one fact rather than
+                        // two sentences with different grammar.
+                        //
+                        // No model. The picker in the footer already shows what this session is set
+                        // to, and showing it twice means two things to keep in step -- they
+                        // disagreed for a moment on every model change.
+                        Text(
+                            "${summary.setupName} · ${summary.provider}",
+                            style = MaterialTheme.typography.bodySmall,
+                            color = MaterialTheme.colorScheme.onSurfaceVariant,
+                        )
+                    }
                 }
+                // None of this is a subagent's: it has no files of its own to browse, no settings,
+                // and nothing meters it -- see SUBAGENTS.md's "Phone".
+                //
                 // Beside the provider it reports on, which is the line directly to its left. Its
                 // real home is this provider's settings, which do not exist yet. A session on a
                 // provider with no such service gets an honest "unavailable" rather than a hidden
@@ -1264,42 +1364,47 @@ fun SessionScreen(
                 // Usage, files, settings -- widest scope first, narrowing to the right, so the cog
                 // stays at the end where every other screen keeps it. Asked for in this order by
                 // Iris on 2026-09-03.
-                Row {
-                    GlyphButton(
-                        USAGE_GLYPH,
-                        "Usage",
-                        { usageOpen = true },
-                        colour = usageGlyphColour(usage),
-                    )
-                    // The machine's files, which is where the answer to "what did it actually
-                    // change" is. It opens *over* this screen rather than replacing it.
-                    GlyphButton(
-                        FOLDER_GLYPH,
-                        "Files",
-                        onClick = {
-                            onFiles(
-                                FilesTarget(
-                                    setup = summary.setup,
-                                    setupName = summary.setupName,
-                                    // Where this session works, and the machine's own home when it
-                                    // was never given a directory -- resolved there rather than
-                                    // guessed at here, since this app does not know that home.
-                                    start = summary.cwd?.takeIf { it.isNotBlank() } ?: "~",
+                if (!isSubagent) {
+                    Row {
+                        GlyphButton(
+                            USAGE_GLYPH,
+                            "Usage",
+                            { usageOpen = true },
+                            colour = usageGlyphColour(usage),
+                        )
+                        // The machine's files, which is where the answer to "what did it actually
+                        // change" is. It opens *over* this screen rather than replacing it.
+                        GlyphButton(
+                            FOLDER_GLYPH,
+                            "Files",
+                            onClick = {
+                                onFiles(
+                                    FilesTarget(
+                                        setup = summary.setup,
+                                        setupName = summary.setupName,
+                                        // Where this session works, and the machine's own home when
+                                        // it was never given a directory -- resolved there rather
+                                        // than guessed at here, since this app does not know that
+                                        // home.
+                                        start = summary.cwd?.takeIf { it.isNotBlank() } ?: "~",
+                                    )
                                 )
-                            )
-                        },
-                    )
-                    // What it opens is about this session, so it sits at the end of the session's
-                    // own row. A cog and not a word because there will be more, and a bar of words
-                    // has nowhere to put it.
-                    GlyphButton(SETTINGS_GLYPH, "Session settings", { settingsOpen = true })
+                            },
+                        )
+                        // What it opens is about this session, so it sits at the end of the
+                        // session's own row. A cog and not a word because there will be more, and a
+                        // bar of words has nowhere to put it.
+                        GlyphButton(SETTINGS_GLYPH, "Session settings", { settingsOpen = true })
+                    }
                 }
             }
 
             // Under the header, above everything the session itself says: it is a fact about the
             // machine rather than a turn in the conversation, and it is the number that decides
-            // whether to keep going.
-            SessionUsageBar(usage)
+            // whether to keep going. Nothing meters a subagent.
+            if (!isSubagent) {
+                SessionUsageBar(usage)
+            }
 
             (streamError ?: actionError)?.let { message ->
                 Text(
@@ -1545,6 +1650,7 @@ fun SessionScreen(
                                                 is TranscriptItem.ClearedNote -> ClearedRow()
                                                 is TranscriptItem.CompactedNote ->
                                                     CompactedRow(item)
+                                                is TranscriptItem.LimitNote -> LimitRow(item)
                                                 // Never reached: a peer message is flattened into
                                                 // its own units. Here because a `when` over the
                                                 // item kinds has to stay exhaustive.
@@ -1643,185 +1749,211 @@ fun SessionScreen(
                 )
             }
 
+            // Kept for a subagent -- see SUBAGENTS.md's "Phone" -- with the wording that turns
+            // "exited" into "finished" for one, since it has no process to leave running or stop.
             SessionStatusRow(
                 status = status,
                 compactingFor = compactingFor,
                 contextTokens = contextTokens,
+                subagent = isSubagent,
             )
 
-            // Between the transcript and the box: above what is being typed, so the list does not
-            // cover the thing the command is about, and below everything that explains it.
-            CommandSuggestions(
-                // Nothing to suggest about a suggestion that was just taken. `/compact` is a whole
-                // command *and* a prefix of itself, so picking it left the list standing there with
-                // the one row already chosen. Held by what was picked rather than by a flag, so
-                // typing anything else brings the list back without a second thing to reset.
-                commands = if (input.text == picked) emptyList() else suggestedCommands(input.text),
-                onPick = { command ->
-                    // At the end of what was inserted, which is where the reader carries on typing:
-                    // a command with an argument is put in the box half-written, and a cursor left
-                    // at the front makes the next keystroke the first character of "/rename".
-                    input = atEnd(command.typed())
-                    picked = command.typed()
-                },
-            )
-
-            // Always enabled -- a send while the session is running becomes a steering message
-            // injected at the next tool boundary, which is the point of the whole app.
-            //
-            // The field gets a row of its own, above the buttons: sharing one put the full width
-            // behind three controls, so the thing being typed into was the narrowest on the row.
-            Column(Modifier.fillMaxWidth().padding(8.dp)) {
-                // Directly above the box they will be sent from, so what is attached is visible
-                // rather than counted: the "+2" on the button below said how many and never which.
-                PendingAttachments(
-                    settings = settings,
-                    sessionId = summary.id,
-                    refs = pendingAttachments,
-                    onRemove = { pendingAttachments = pendingAttachments - it },
-                )
-                OutlinedTextField(
-                    value = input,
-                    onValueChange = {
-                        input = it
-                        saveDraft(context, summary.id, it.text)
+            // Everything from here down is the composer: a subagent cannot be messaged, so none of
+            // it applies -- see SUBAGENTS.md's "Phone".
+            if (!isSubagent) {
+                // Between the transcript and the box: above what is being typed, so the list does
+                // not cover the thing the command is about, and below everything that explains it.
+                CommandSuggestions(
+                    // Nothing to suggest about a suggestion that was just taken. `/compact` is a
+                    // whole command *and* a prefix of itself, so picking it left the list standing
+                    // there with the one row already chosen. Held by what was picked rather than by
+                    // a flag, so typing anything else brings the list back without a second thing
+                    // to
+                    // reset.
+                    commands =
+                        if (input.text == picked) emptyList() else suggestedCommands(input.text),
+                    onPick = { command ->
+                        // At the end of what was inserted, which is where the reader carries on
+                        // typing: a command with an argument is put in the box half-written, and a
+                        // cursor left at the front makes the next keystroke the first character of
+                        // "/rename".
+                        input = atEnd(command.typed())
+                        picked = command.typed()
                     },
-                    modifier = Modifier.fillMaxWidth(),
-                    // No longer "(+image)": the images are on screen above this, and a placeholder
-                    // saying so said it in words beside the thing itself.
-                    placeholder = { Text("Message") },
-                    maxLines = 4,
                 )
-                Row(
-                    verticalAlignment = Alignment.CenterVertically,
-                    modifier = Modifier.fillMaxWidth(),
-                ) {
-                    // Photo or file, asked here rather than by two buttons: the row is full, and
-                    // attaching is one action whichever picker answers it.
-                    var attaching by remember { mutableStateOf(false) }
-                    Box {
-                        // Just "+". The count it used to carry was standing in for showing them.
-                        BubbleButton(onClick = { attaching = true }) { Text("+") }
-                        DropdownMenu(
-                            expanded = attaching,
-                            onDismissRequest = { attaching = false },
-                            // See PickerButton: without this the menu opens a status bar's height
-                            // away from the button in an edge-to-edge activity.
-                            properties = PopupProperties(clippingEnabled = false),
-                            shape = BubbleMenuShape,
-                        ) {
-                            DropdownMenuItem(
-                                text = { Text("Photo") },
-                                onClick = {
-                                    attaching = false
-                                    pickImage.launch(
-                                        PickVisualMediaRequest(
-                                            ActivityResultContracts.PickVisualMedia.ImageOnly
-                                        )
-                                    )
-                                },
-                            )
-                            DropdownMenuItem(
-                                text = { Text("File") },
-                                onClick = {
-                                    attaching = false
-                                    pickFile.launch(arrayOf("*/*"))
-                                },
-                            )
-                        }
-                    }
-                    // The settings share what is left after the actions have taken what they need.
-                    // A Row hands out intrinsic widths in order and clips whatever runs past the
-                    // edge, so with these laid out first the arrival of Stop pushed Send off the
-                    // screen entirely -- the app's central control, gone at the moment it is most
-                    // in use.
+
+                // Always enabled -- a send while the session is running becomes a steering message
+                // injected at the next tool boundary, which is the point of the whole app.
+                //
+                // The field gets a row of its own, above the buttons: sharing one put the full
+                // width
+                // behind three controls, so the thing being typed into was the narrowest on the
+                // row.
+                Column(Modifier.fillMaxWidth().padding(8.dp)) {
+                    // Directly above the box they will be sent from, so what is attached is visible
+                    // rather than counted: the "+2" on the button below said how many and never
+                    // which.
+                    PendingAttachments(
+                        settings = settings,
+                        sessionId = summary.id,
+                        refs = pendingAttachments,
+                        onRemove = { pendingAttachments = pendingAttachments - it },
+                    )
+                    OutlinedTextField(
+                        value = input,
+                        onValueChange = {
+                            input = it
+                            saveDraft(context, summary.id, it.text)
+                        },
+                        // BenchRun's type phase requests focus on this exact field
+                        // (`composerFocus`)
+                        // so it types through the real composer rather than a stand-in.
+                        modifier = Modifier.fillMaxWidth().focusRequester(composerFocus),
+                        // No longer "(+image)": the images are on screen above this, and a
+                        // placeholder saying so said it in words beside the thing itself.
+                        placeholder = { Text("Message") },
+                        maxLines = 4,
+                    )
                     Row(
                         verticalAlignment = Alignment.CenterVertically,
-                        modifier = Modifier.weight(1f),
+                        modifier = Modifier.fillMaxWidth(),
                     ) {
-                        if (offeredModels.isNotEmpty()) {
+                        // Photo or file, asked here rather than by two buttons: the row is full,
+                        // and
+                        // attaching is one action whichever picker answers it.
+                        var attaching by remember { mutableStateOf(false) }
+                        Box {
+                            // Just "+". The count it used to carry was standing in for showing
+                            // them.
+                            BubbleButton(onClick = { attaching = true }) { Text("+") }
+                            DropdownMenu(
+                                expanded = attaching,
+                                onDismissRequest = { attaching = false },
+                                // See PickerButton: without this the menu opens a status bar's
+                                // height away from the button in an edge-to-edge activity.
+                                properties = PopupProperties(clippingEnabled = false),
+                                shape = BubbleMenuShape,
+                            ) {
+                                DropdownMenuItem(
+                                    text = { Text("Photo") },
+                                    onClick = {
+                                        attaching = false
+                                        pickImage.launch(
+                                            PickVisualMediaRequest(
+                                                ActivityResultContracts.PickVisualMedia.ImageOnly
+                                            )
+                                        )
+                                    },
+                                )
+                                DropdownMenuItem(
+                                    text = { Text("File") },
+                                    onClick = {
+                                        attaching = false
+                                        pickFile.launch(arrayOf("*/*"))
+                                    },
+                                )
+                            }
+                        }
+                        // The settings share what is left after the actions have taken what they
+                        // need. A Row hands out intrinsic widths in order and clips whatever runs
+                        // past the edge, so with these laid out first the arrival of Stop pushed
+                        // Send off the screen entirely -- the app's central control, gone at the
+                        // moment it is most in use.
+                        Row(
+                            verticalAlignment = Alignment.CenterVertically,
+                            modifier = Modifier.weight(1f),
+                        ) {
+                            if (offeredModels.isNotEmpty()) {
+                                PickerButton(
+                                    current = modelLabel(model),
+                                    // What the machine offers, plus the state a session is in when
+                                    // it has chosen none of them. The button has always been able
+                                    // to
+                                    // say "default"; until this the list could not, so leaving it
+                                    // was a one-way trip.
+                                    options = listOf(DEFAULT_MODEL) + offeredModels,
+                                    // Not set here. The button follows what the session reports it
+                                    // is set to, which arrives a moment later and is sometimes a
+                                    // different answer -- a name the CLI resolved, or no change at
+                                    // all on a provider whose model is fixed. Asked about first,
+                                    // unless there is nothing to lose by it -- see
+                                    // [ModelSwitchWarning].
+                                    onPick = { chosen ->
+                                        if (
+                                            modelLabel(chosen) == modelLabel(model) ||
+                                                !worthWarningAbout(status, contextTokens, items)
+                                        ) {
+                                            act { setSessionModel(settings, summary.id, chosen) }
+                                        } else {
+                                            pendingModel = chosen
+                                        }
+                                    },
+                                )
+                            }
                             PickerButton(
-                                current = modelLabel(model),
-                                // What the machine offers, plus the state a session is in when it
-                                // has chosen none of them. The button has always been able to say
-                                // "default"; until this the list could not, so leaving it was a
-                                // one-way trip.
-                                options = listOf(DEFAULT_MODEL) + offeredModels,
-                                // Not set here. The button follows what the session reports it is
-                                // set to, which arrives a moment later and is sometimes a different
-                                // answer -- a name the CLI resolved, or no change at all on a
-                                // provider whose model is fixed. Asked about first, unless there is
-                                // nothing to lose by it -- see [ModelSwitchWarning].
+                                current = permissionMode,
+                                options = PERMISSION_MODES,
                                 onPick = { chosen ->
-                                    if (
-                                        modelLabel(chosen) == modelLabel(model) ||
-                                            !worthWarningAbout(status, contextTokens, items)
-                                    ) {
-                                        act { setSessionModel(settings, summary.id, chosen) }
-                                    } else {
-                                        pendingModel = chosen
-                                    }
+                                    act { setSessionPermissionMode(settings, summary.id, chosen) }
                                 },
                             )
                         }
-                        PickerButton(
-                            current = permissionMode,
-                            options = PERMISSION_MODES,
-                            onPick = { chosen ->
-                                act { setSessionPermissionMode(settings, summary.id, chosen) }
-                            },
-                        )
-                    }
-                    // The same filled shape as the button beside it, not an outlined one: these are
-                    // two things you can do about the session, and weighting one as secondary said
-                    // they were a primary action and its qualifier. What separates them is the
-                    // colour and the mark, which is what they mean.
-                    //
-                    // Always here, rather than arriving with the turn as it used to. A control that
-                    // comes and goes makes its own presence the signal, and a button always in the
-                    // same place also cannot push Send off the end of the row by turning up.
-                    val process =
-                        when {
-                            running -> ProcessAction.Pause
-                            status == "exited" -> ProcessAction.Start
-                            else -> ProcessAction.Stop
-                        }
-                    Button(
-                        onClick = {
-                            processInFlight = true
-                            act(onDone = { processInFlight = false }) {
-                                process.perform(settings, summary.id)
+                        // The same filled shape as the button beside it, not an outlined one: these
+                        // are two things you can do about the session, and weighting one as
+                        // secondary said they were a primary action and its qualifier. What
+                        // separates them is the colour and the mark, which is what they mean.
+                        //
+                        // Always here, rather than arriving with the turn as it used to. A control
+                        // that comes and goes makes its own presence the signal, and a button
+                        // always
+                        // in the same place also cannot push Send off the end of the row by turning
+                        // up.
+                        val process =
+                            when {
+                                running -> ProcessAction.Pause
+                                status == "exited" -> ProcessAction.Start
+                                else -> ProcessAction.Stop
                             }
-                        },
-                        enabled = !processInFlight,
-                        colors = actionButtonColors(process.colour()),
-                    ) {
-                        Glyph(
-                            process.glyph,
-                            colour = LocalContentColor.current,
-                            modifier = Modifier.semantics { contentDescription = process.label },
-                        )
-                    }
-                    Spacer(Modifier.width(8.dp))
-                    // The paper plane, with a clock on it while a turn is in flight: sending then
-                    // queues the message for the next tool boundary rather than starting a turn of
-                    // its own, and the two have to be told apart at a glance. The label says the
-                    // same thing to a screen reader.
-                    //
-                    // Disabled while there is nothing to send, rather than pressable and silent:
-                    // `send` has always returned early on an empty composer, so the button promised
-                    // something it would not do. Disabled and not hidden, for the reason above.
-                    Button(
-                        onClick = { send() },
-                        enabled = input.text.isNotBlank() || pendingAttachments.isNotEmpty(),
-                        colors = actionButtonColors(if (running) queueColor else sendColor),
-                    ) {
-                        Glyph(
-                            if (running) QUEUE_GLYPH else SEND_GLYPH,
-                            colour = LocalContentColor.current,
-                            modifier =
-                                Modifier.semantics { contentDescription = sendLabel(running) },
-                        )
+                        Button(
+                            onClick = {
+                                processInFlight = true
+                                act(onDone = { processInFlight = false }) {
+                                    process.perform(settings, summary.id)
+                                }
+                            },
+                            enabled = !processInFlight,
+                            colors = actionButtonColors(process.colour()),
+                        ) {
+                            Glyph(
+                                process.glyph,
+                                colour = LocalContentColor.current,
+                                modifier =
+                                    Modifier.semantics { contentDescription = process.label },
+                            )
+                        }
+                        Spacer(Modifier.width(8.dp))
+                        // The paper plane, with a clock on it while a turn is in flight: sending
+                        // then queues the message for the next tool boundary rather than starting a
+                        // turn of its own, and the two have to be told apart at a glance. The label
+                        // says the same thing to a screen reader.
+                        //
+                        // Disabled while there is nothing to send, rather than pressable and
+                        // silent:
+                        // `send` has always returned early on an empty composer, so the button
+                        // promised something it would not do. Disabled and not hidden, for the
+                        // reason above.
+                        Button(
+                            onClick = { send() },
+                            enabled = input.text.isNotBlank() || pendingAttachments.isNotEmpty(),
+                            colors = actionButtonColors(if (running) queueColor else sendColor),
+                        ) {
+                            Glyph(
+                                if (running) QUEUE_GLYPH else SEND_GLYPH,
+                                colour = LocalContentColor.current,
+                                modifier =
+                                    Modifier.semantics { contentDescription = sendLabel(running) },
+                            )
+                        }
                     }
                 }
             }
@@ -1832,7 +1964,7 @@ fun SessionScreen(
     // is the screen's business rather than any row's. See [SessionImageViewer].
     fullImage?.let { ref -> SessionImageViewer(settings, summary.id, ref) { fullImage = null } }
     if (usageOpen) {
-        UsageDialog(feed = usageFeed, onDismiss = { usageOpen = false })
+        usageFeed?.let { UsageDialog(feed = it, onDismiss = { usageOpen = false }) }
     }
     if (settingsOpen) {
         // Measured when the dialog opens rather than kept up to date: what the reader is being told
@@ -1846,6 +1978,8 @@ fun SessionScreen(
             settings = settings,
             sessionId = summary.id,
             title = title,
+            effort = summary.effort.takeIf { summary.takesEffort },
+            takesEffort = summary.takesEffort,
             cachedBytes = cachedBytes,
             // The purge finishes before the epoch moves, because the relaunched opening effect
             // reads the same directory and would otherwise draw what is about to be deleted. The
@@ -1869,6 +2003,7 @@ fun SessionScreen(
             },
             onDismiss = { settingsOpen = false },
             onCopyRenderReport = copyRenderReport,
+            onRunBenchmark = runBenchmark,
         )
     }
 }
@@ -2122,6 +2257,13 @@ private fun SessionStatusRow(
     /** Context the session is holding, or null where nothing has measured it. */
     contextTokens: Long?,
     modifier: Modifier = Modifier,
+    /**
+     * Whether this row is for a subagent rather than a session, which changes only one word:
+     * "exited" reads as "finished" there too, the same as the subagent list's own card -- a
+     * subagent's process was always its parent's, so "exited" would read as a fault rather than the
+     * ordinary way one of these ends.
+     */
+    subagent: Boolean = false,
 ) {
     DebugStats.count("status row recomposed")
     Row(
@@ -2178,7 +2320,7 @@ private fun SessionStatusRow(
                 Text(
                     when (status) {
                         "idle" -> "idle"
-                        "exited" -> "exited"
+                        "exited" -> if (subagent) "finished" else "exited"
                         "awaitingInput" -> "your turn"
                         "unknown" -> "can't tell"
                         else -> status
@@ -2249,7 +2391,7 @@ private const val ONE_TAP_MS = 250L
  * session is set to without spending a second line on saying it.
  */
 @Composable
-private fun PickerButton(current: String, options: List<String>, onPick: (String) -> Unit) {
+fun PickerButton(current: String, options: List<String>, onPick: (String) -> Unit) {
     var open by remember { mutableStateOf(false) }
     // When an outside touch last closed the menu.
     //

app/androidApp/src/main/kotlin/com/example/aiapp/SessionSettingsDialog.kt

@@ -6,8 +6,10 @@ import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.text.KeyboardActions
 import androidx.compose.foundation.text.KeyboardOptions
+import androidx.compose.foundation.verticalScroll
 import androidx.compose.material3.AlertDialog
 import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.material3.MaterialTheme
@@ -26,6 +28,10 @@ import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.text.input.ImeAction
 import androidx.compose.ui.unit.dp
+import java.time.Instant
+import java.time.ZoneId
+import java.time.format.DateTimeFormatter
+import java.time.format.FormatStyle
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
@@ -54,6 +60,16 @@ fun SessionSettingsDialog(
      */
     title: String,
     onRenamed: (String) -> Unit,
+    /**
+     * How hard the model thinks, as the session reports it, or null for the CLI's own default.
+     *
+     * Taken from the row this dialog was opened over rather than fetched, because unlike the
+     * notification switch there is nothing else that changes it: the level is this app's to set and
+     * the server does not resolve it into something else.
+     */
+    effort: String?,
+    /** Whether a level does anything here; the row is left out entirely where it does not. */
+    takesEffort: Boolean,
     /**
      * What this phone is holding of the conversation, or null while that is being measured -- see
      * the Reload row below, which is what would discard it.
@@ -66,9 +82,18 @@ fun SessionSettingsDialog(
      * measures is that screen's own state.
      */
     onCopyRenderReport: () -> Unit,
+    /**
+     * Runs P0's scripted scroll-and-stream benchmark and copies the extended report, or null on
+     * every build but `bench` -- see [BuildConfig.FIXTURE_MODE] and BenchRun.kt. Null rather than
+     * always-present-but-disabled: this has no meaning at all outside the bench build, and a
+     * control with nothing behind it on every other build is not a state worth drawing.
+     */
+    onRunBenchmark: (() -> Unit)? = null,
 ) {
     val scope = rememberCoroutineScope()
     var name by remember(sessionId) { mutableStateOf(title) }
+    var level by remember(sessionId) { mutableStateOf(effort) }
+    var effortError by remember { mutableStateOf<String?>(null) }
     var saving by remember { mutableStateOf(false) }
     var error by remember { mutableStateOf<String?>(null) }
     // Null until the server has been asked. The row this dialog was opened over is a snapshot of
@@ -77,6 +102,16 @@ fun SessionSettingsDialog(
     // and a spinner sits beside it, which is what not knowing looks like.
     var notify by remember(sessionId) { mutableStateOf<Boolean?>(null) }
     var notifyError by remember { mutableStateOf<String?>(null) }
+    // The same three-state shape the notification switch has, for the same reason: until the
+    // server has answered, the switch is disabled rather than showing a position nothing confirmed.
+    var autoResume by remember(sessionId) { mutableStateOf<Boolean?>(null) }
+    var resumeMessage by remember(sessionId) { mutableStateOf(DEFAULT_RESUME_MESSAGE) }
+    // When the server next intends to ask whether the limit has lifted, or null when nothing is
+    // waiting. Read once with everything else: it moves on the server's schedule, not this
+    // screen's, and a figure that redrew itself here would be this app re-measuring what it was
+    // told.
+    var resumeAt by remember(sessionId) { mutableStateOf<Double?>(null) }
+    var resumeError by remember { mutableStateOf<String?>(null) }
     // Where the session works. Null until the server has been asked, for the same reason the switch
     // above is. An empty answer is a session that was never given a directory, which is not the
     // same as one whose directory is unknown -- the field is only enabled once one of those is
@@ -90,6 +125,9 @@ fun SessionSettingsDialog(
         try {
             val fresh = withContext(Dispatchers.IO) { fetchSession(settings, sessionId) }
             notify = fresh.notify
+            autoResume = fresh.autoResume
+            resumeMessage = fresh.autoResumeMessage
+            resumeAt = fresh.resumeAt
             cwd = fresh.cwd.orEmpty()
             typedCwd = fresh.cwd.orEmpty()
         } catch (e: ApiException) {
@@ -97,6 +135,8 @@ fun SessionSettingsDialog(
             // instead of offering a position nothing confirmed.
             notifyError = e.message
             notify = null
+            resumeError = e.message
+            autoResume = null
         }
     }
 
@@ -125,6 +165,26 @@ fun SessionSettingsDialog(
         }
     }
 
+    /**
+     * Chooses a thinking level, which ends the process the old level was launched with.
+     *
+     * Put back if the request is refused, for the reason the notification switch below gives: a
+     * control that stays where it was put after a refusal is stating something untrue.
+     */
+    fun setEffort(chosen: String?) {
+        val was = level
+        level = chosen
+        effortError = null
+        scope.launch {
+            try {
+                withContext(Dispatchers.IO) { setSessionEffort(settings, sessionId, chosen) }
+            } catch (e: ApiException) {
+                level = was
+                effortError = e.message
+            }
+        }
+    }
+
     // Moved optimistically so the switch answers the finger that moved it, and put back if the
     // request is refused -- a switch that waits for a round trip reads as broken on a slow tunnel,
     // and one that stays moved after a refusal lies.
@@ -142,6 +202,39 @@ fun SessionSettingsDialog(
         }
     }
 
+    /**
+     * Turns auto-resume on or off, or changes what it would say.
+     *
+     * One request for both, because the server takes one: switching it on and typing the message
+     * are two halves of the same decision, and sending them separately would leave a moment where
+     * the session is armed with the old words.
+     *
+     * Put back if refused, like the notification switch. Turning it off also clears what was
+     * scheduled -- said here rather than only on the server, or the row would go on naming a time
+     * that no longer exists.
+     */
+    fun setAutoResume(on: Boolean, message: String) {
+        val wasOn = autoResume
+        val wasMessage = resumeMessage
+        val wasAt = resumeAt
+        autoResume = on
+        resumeMessage = message
+        if (!on) resumeAt = null
+        resumeError = null
+        scope.launch {
+            try {
+                withContext(Dispatchers.IO) {
+                    setSessionAutoResume(settings, sessionId, on, message)
+                }
+            } catch (e: ApiException) {
+                autoResume = wasOn
+                resumeMessage = wasMessage
+                resumeAt = wasAt
+                resumeError = e.message
+            }
+        }
+    }
+
     // Nothing to do when the name has not changed, so the button says so rather than sending a
     // request whose success would look exactly like the failure of having typed nothing.
     val changed = name.trim().isNotEmpty() && name.trim() != title
@@ -168,7 +261,10 @@ fun SessionSettingsDialog(
         onDismissRequest = onDismiss,
         title = { Text("Session settings") },
         text = {
-            Column {
+            // Scrollable, because this dialog grew past a screenful: a Material dialog constrains
+            // its own height and clips what does not fit, so the last control on the list is one
+            // large system font away from being unreachable with nothing on screen to say so.
+            Column(Modifier.verticalScroll(rememberScrollState())) {
                 OutlinedTextField(
                     value = name,
                     onValueChange = { name = it },
@@ -212,6 +308,70 @@ fun SessionSettingsDialog(
                     )
                 }
                 Spacer(Modifier.height(8.dp))
+                Row(
+                    verticalAlignment = Alignment.CenterVertically,
+                    modifier = Modifier.fillMaxWidth(),
+                ) {
+                    Text("Resume after a usage limit", modifier = Modifier.weight(1f))
+                    if (autoResume == null && resumeError == null) {
+                        CircularProgressIndicator(
+                            modifier = Modifier.width(16.dp).height(16.dp),
+                            strokeWidth = 2.dp,
+                        )
+                        Spacer(Modifier.width(8.dp))
+                    }
+                    Switch(
+                        checked = autoResume == true,
+                        onCheckedChange = { setAutoResume(it, resumeMessage) },
+                        enabled = autoResume != null,
+                    )
+                }
+                // Disabled rather than hidden while the switch is off: a field that comes and goes
+                // makes its own presence the signal, and a visible one teaches what the switch will
+                // do. Committed on the keyboard's Done rather than on every keystroke, so typing a
+                // sentence is one request instead of one per letter.
+                OutlinedTextField(
+                    value = resumeMessage,
+                    onValueChange = { resumeMessage = it },
+                    label = { Text("Message to send") },
+                    // What an empty field means, in the field: the server's own word rather than a
+                    // session poked with nothing to read.
+                    placeholder = { Text(DEFAULT_RESUME_MESSAGE) },
+                    singleLine = true,
+                    enabled = autoResume == true,
+                    modifier = Modifier.fillMaxWidth(),
+                    keyboardOptions = KeyboardOptions(imeAction = ImeAction.Done),
+                    keyboardActions =
+                        KeyboardActions(onDone = { setAutoResume(true, resumeMessage) }),
+                )
+                // What it does and what it costs, in the order it happens. The last sentence is the
+                // one that matters: the time below is when the server will *ask*, not a promise
+                // about when the session speaks.
+                Text(
+                    "When this session stops because the account is out of quota, the server " +
+                        "checks the limit and sends this message once it has lifted. It checks " +
+                        "again if the limit is still on.",
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant,
+                )
+                // Only where something is actually waiting. Absent is not a state worth a row: a
+                // session that has not hit a limit has nothing scheduled, which the reader can see
+                // from the switch.
+                resumeAt?.let { at ->
+                    Text(
+                        "Waiting now -- next check ${formatCheckTime(at)}.",
+                        style = MaterialTheme.typography.bodySmall,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    )
+                }
+                resumeError?.let {
+                    Text(
+                        it,
+                        color = MaterialTheme.colorScheme.error,
+                        style = MaterialTheme.typography.bodySmall,
+                    )
+                }
+                Spacer(Modifier.height(8.dp))
                 Row(
                     verticalAlignment = Alignment.CenterVertically,
                     modifier = Modifier.fillMaxWidth(),
@@ -257,6 +417,44 @@ fun SessionSettingsDialog(
                         style = MaterialTheme.typography.bodySmall,
                     )
                 }
+                // Left out rather than disabled, the one place this dialog does that: a disabled
+                // control teaches what the thing can do, and a llama session cannot do this at all
+                // -- the row would be teaching something false about it.
+                if (takesEffort) {
+                    Spacer(Modifier.height(8.dp))
+                    Row(
+                        verticalAlignment = Alignment.CenterVertically,
+                        modifier = Modifier.fillMaxWidth(),
+                    ) {
+                        Text("Thinking", modifier = Modifier.weight(1f))
+                        PickerButton(
+                            current = level ?: DEFAULT_EFFORT,
+                            // The level the CLI picks for itself is in the list as well as in the
+                            // button, so leaving a level is not a one-way trip -- the same
+                            // correction the model picker carries.
+                            options = listOf(DEFAULT_EFFORT) + EFFORT_LEVELS,
+                            onPick = { chosen ->
+                                setEffort(chosen.takeIf { it != DEFAULT_EFFORT })
+                            },
+                        )
+                    }
+                    // What it costs, said where it is about to be pressed, like Move above: the
+                    // CLI reads the level when it launches and has no control request for
+                    // changing one.
+                    Text(
+                        "Changing this stops the session's process. It starts again with the " +
+                            "next message, or with Start.",
+                        style = MaterialTheme.typography.bodySmall,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    )
+                    effortError?.let {
+                        Text(
+                            it,
+                            color = MaterialTheme.colorScheme.error,
+                            style = MaterialTheme.typography.bodySmall,
+                        )
+                    }
+                }
                 Spacer(Modifier.height(8.dp))
                 Row(
                     verticalAlignment = Alignment.CenterVertically,
@@ -317,6 +515,21 @@ fun SessionSettingsDialog(
                     Text("Render timings", modifier = Modifier.weight(1f))
                     TextButton(onClick = onCopyRenderReport) { Text("Copy") }
                 }
+                // Bench-build only: see [onRunBenchmark]. Named exactly "Run benchmark" because
+                // ui-trace and the emulator smoke run find it by that label, the same way every
+                // other control here is found -- see AGENTS.md's "Driving the UI".
+                onRunBenchmark?.let { run ->
+                    Spacer(Modifier.height(8.dp))
+                    Row(
+                        verticalAlignment = Alignment.CenterVertically,
+                        modifier = Modifier.fillMaxWidth(),
+                    ) {
+                        Glyph(SPEED_GLYPH, colour = MaterialTheme.colorScheme.onSurface)
+                        Spacer(Modifier.width(8.dp))
+                        Text("P0 benchmark", modifier = Modifier.weight(1f))
+                        TextButton(onClick = run) { Text("Run benchmark") }
+                    }
+                }
             }
         },
         // Disabled rather than absent while there is nothing to save: a button that comes and goes
@@ -329,3 +542,21 @@ fun SessionSettingsDialog(
         dismissButton = { TextButton(onClick = onDismiss) { Text("Close") } },
     )
 }
+
+/**
+ * When the server will next look, as a local time.
+ *
+ * A time rather than a countdown, for the reason the transcript's own limit row gives: this screen
+ * reads the figure once, and a span drawn from a value nothing refreshes goes stale while somebody
+ * is looking at it.
+ */
+private fun formatCheckTime(epochSeconds: Double): String =
+    try {
+        DateTimeFormatter.ofLocalizedTime(FormatStyle.SHORT)
+            .withZone(ZoneId.systemDefault())
+            .format(Instant.ofEpochSecond(epochSeconds.toLong()))
+    } catch (_: Exception) {
+        // A time that cannot be read is not a time to show: the sentence above still says a check
+        // is coming, which is the part the reader can act on.
+        "soon"
+    }

app/androidApp/src/main/kotlin/com/example/aiapp/SessionUsageBar.kt

@@ -70,13 +70,22 @@ class UsageFeed(
     /** Ask the backend again now. The dialog's refresh button; the poll does it on its own. */
     val refresh: () -> Unit,
 ) {
-    /** What [setup]'s own limits came back as. See [usageFor] for why the states are these. */
-    fun forSetup(setup: String): SessionUsage =
-        when (val state = snapshots) {
+    /**
+     * What meters [session], and what that meter came back as. See [usageFor] for the states.
+     *
+     * A session rather than a machine, because a machine is not what is metered: one machine runs
+     * the Claude CLI and an echo session side by side, and only the first of them spends anything.
+     */
+    fun forSession(session: SessionSummary): SessionUsage {
+        // Settled without asking anybody: a session nothing meters has nothing to check, and
+        // "checking" is what the fetch's own states would say about it for as long as one is out.
+        val provider = session.usageProvider ?: return SessionUsage.NotMetered
+        return when (val state = snapshots) {
             is LoadState.Loading -> SessionUsage.Waiting
             is LoadState.Error -> SessionUsage.Unavailable(state.message)
-            is LoadState.Loaded -> usageFor(state.value, setup)
+            is LoadState.Loaded -> usageFor(state.value, session.setup, provider)
         }
+    }
 }
 
 /**
@@ -158,9 +167,15 @@ fun SessionUsageBar(usage: SessionUsage, modifier: Modifier = Modifier) {
         }
     }
 
-    // Nothing at all for a machine that meters nothing: a row saying "unknown" there would report a
-    // problem about a setup somebody chose, on every screen, forever.
-    if (usage is SessionUsage.NotMetered) {
+    // Nothing at all for a session that meters nothing: a row saying "unknown" there would report
+    // a problem about a setup somebody chose, on every screen, forever.
+    //
+    // And nothing while the first fetch is out, which is a different silence. A request in flight
+    // is not a state to report -- and the session that meters nothing is exactly the one this
+    // cannot yet tell apart, so "5-hour usage: checking" appeared under an echo session for half a
+    // second and was then taken away. A row that has to be withdrawn is worse than one that
+    // arrives late.
+    if (usage is SessionUsage.NotMetered || usage is SessionUsage.Waiting) {
         return
     }
 
@@ -171,9 +186,10 @@ fun SessionUsageBar(usage: SessionUsage, modifier: Modifier = Modifier) {
         // Words, not a colour and not an empty bar: every one of these is a different kind of
         // answer from "this much is used", and only words carry a difference in kind.
         when (val state = usage) {
-            SessionUsage.NotMetered -> Unit
+            // Both handled above, before the row exists at all.
+            SessionUsage.NotMetered,
+            SessionUsage.Waiting -> Unit
             is SessionUsage.Unavailable -> UsageNote("5-hour usage unknown -- ${state.why}")
-            SessionUsage.Waiting -> UsageNote("5-hour usage: checking")
             is SessionUsage.Known -> {
                 val window = state.windows.firstOrNull { it.kind == "session" }
                 if (window == null) {
@@ -234,16 +250,22 @@ private fun fiveHourLabel(window: UsageWindow, now: OffsetDateTime): String {
 }
 
 /**
- * One machine's snapshot, out of every machine's.
+ * One meter's snapshot, out of every machine's: [setup]'s row for [provider].
+ *
+ * Both halves are needed to pick it. A machine can hold more than one meter -- the Claude CLI's
+ * account and, while a test has one set, an echo session's invented one -- and a snapshot is one
+ * service on one machine.
  *
  * Every way of having *failed* to get numbers is [SessionUsage.Unavailable] with the reason in it.
  * None of them may look like zero, and none may look like [SessionUsage.NotMetered], which is the
  * machine having no quota rather than the question going unanswered.
  */
-fun usageFor(snapshots: List<UsageSnapshot>, setup: String): SessionUsage {
-    // No snapshot at all means the backend never asked, which it only does for a machine with
-    // nothing metered on it. That is a different answer from having asked and failed.
-    val mine = snapshots.firstOrNull { it.setup == setup } ?: return SessionUsage.NotMetered
+fun usageFor(snapshots: List<UsageSnapshot>, setup: String, provider: String): SessionUsage {
+    // No snapshot at all means the backend never asked, which it only does where there is nothing
+    // to ask about. That is a different answer from having asked and failed.
+    val mine =
+        snapshots.firstOrNull { it.setup == setup && it.provider == provider }
+            ?: return SessionUsage.NotMetered
     if (mine.state != "ok") {
         return SessionUsage.Unavailable(mine.detail ?: mine.state)
     }

app/androidApp/src/main/kotlin/com/example/aiapp/SetupsScreen.kt

@@ -236,6 +236,7 @@ private fun AddSetupDialog(
     var address by remember { mutableStateOf("") }
     var identity by remember { mutableStateOf("") }
     var attachmentsDir by remember { mutableStateOf("") }
+    var modelsDir by remember { mutableStateOf("") }
     var tested by remember { mutableStateOf<String?>(null) }
     var testing by remember { mutableStateOf(false) }
 
@@ -250,6 +251,7 @@ private fun AddSetupDialog(
                     port = typedPort,
                     identityFile = identity.trim().ifEmpty { null },
                     attachmentsDir = attachmentsDir.trim().ifEmpty { null },
+                    modelsDir = modelsDir.trim().ifEmpty { null },
                 )
             }
 
@@ -293,6 +295,14 @@ private fun AddSetupDialog(
                     label = { Text("Folder for attached files (optional)") },
                     singleLine = true,
                 )
+                // Where that machine's GGUFs are, for a llama.cpp session on it. Blank means
+                // the same place this backend keeps its own downloads, read on that machine.
+                OutlinedTextField(
+                    value = modelsDir,
+                    onValueChange = { modelsDir = it },
+                    label = { Text("Folder for models (optional)") },
+                    singleLine = true,
+                )
                 tested?.let {
                     Spacer(Modifier.height(8.dp))
                     Text(it, style = MaterialTheme.typography.bodySmall)

app/androidApp/src/main/kotlin/com/example/aiapp/SpawnScreen.kt

@@ -61,18 +61,31 @@ fun SpawnScreen(
     // "auto" rather than "manual": on a phone every ask is a round trip to a question card, and
     // answering "allow Bash?" dozens of times per task is what this app exists to avoid.
     var permissionMode by remember { mutableStateOf("auto") }
+    // Null until the server has been asked, and null again if it answers "no level chosen" -- the
+    // two are told apart by [defaultsAsked], because a picker that shows a level before the answer
+    // arrives is one you can spawn at without having chosen it.
+    var effort by remember { mutableStateOf<String?>(null) }
+    var defaultsAsked by remember { mutableStateOf(false) }
     var busy by remember { mutableStateOf(false) }
     // Only the spawn's own failure. The fetch's lives in `options`: this one leaves a filled-in
     // form worth keeping, and that one leaves nothing to fill in.
     var spawnError by remember { mutableStateOf<String?>(null) }
-    // Downloaded models, for a llama provider to choose between. Kept separate from the setups: a
-    // Claude session needs none, so failing to list them must not stop the screen rendering.
+    // The models on the *chosen machine*, for a llama provider to choose between. Kept separate
+    // from the setups: a Claude session needs none, so failing to list them must not stop the
+    // screen rendering. Refetched when the machine changes, because a model is a file on one
+    // machine -- see [fetchSetupModels].
     var models by remember { mutableStateOf<List<LocalModel>>(emptyList()) }
     var modelKey by remember { mutableStateOf<String?>(null) }
     var contextSize by remember { mutableStateOf("") }
     var temperature by remember { mutableStateOf("") }
 
     LaunchedEffect(Unit) {
+        // Separate from the setups fetch below and deliberately not fatal: failing to learn the
+        // default must leave a screen you can still spawn from, so the picker stays on "default"
+        // and says so rather than the whole form refusing to draw.
+        runCatching { withContext(Dispatchers.IO) { fetchDefaultEffort(settings) } }
+            .onSuccess { effort = it }
+        defaultsAsked = true
         options =
             try {
                 val fetched = withContext(Dispatchers.IO) { fetchSetups(settings) }
@@ -83,9 +96,6 @@ fun SpawnScreen(
             } catch (e: ApiException) {
                 LoadState.failed(e)
             }
-        models =
-            runCatching { withContext(Dispatchers.IO) { fetchModels(settings).local } }
-                .getOrDefault(emptyList())
     }
 
     Column(Modifier.fillMaxSize().verticalScroll(rememberScrollState()).padding(16.dp)) {
@@ -115,6 +125,17 @@ fun SpawnScreen(
                 is LoadState.Loaded -> state.value
             }
         val setup = setups.firstOrNull { it.name == setupName }
+        // Whichever machine is chosen now, asked again when that changes. The old machine's list
+        // is dropped first rather than left on screen: a file name from another machine looks
+        // exactly like one from this one.
+        LaunchedEffect(setup?.id) {
+            models = emptyList()
+            modelKey = null
+            val id = setup?.id ?: return@LaunchedEffect
+            models =
+                runCatching { withContext(Dispatchers.IO) { fetchSetupModels(settings, id) } }
+                    .getOrDefault(emptyList())
+        }
         val current = setup?.providers?.firstOrNull { it.name == providerName }
         // Only the Claude CLI has models, a working directory and permission modes; keying the
         // extra fields on the kind rather than the provider name keeps a second Claude provider
@@ -175,12 +196,13 @@ fun SpawnScreen(
         )
 
         if (isLlama) {
-            // A llama session names one of the models this backend has downloaded, so the choice is
-            // that list rather than free text -- a name that is not on disk is a session that
-            // cannot start.
+            // A llama session names one of the models on the machine it will run on, so the
+            // choice is that list rather than free text -- a name that is not on that machine's
+            // disk is a session that cannot start.
             if (models.isEmpty()) {
                 Text(
-                    "No models downloaded yet. Get one from the Models screen first.",
+                    "No models on ${setup?.name ?: "this machine"}. The Models screen downloads " +
+                        "to the backend; another machine needs the file put there itself.",
                     style = MaterialTheme.typography.bodyMedium,
                     color = MaterialTheme.colorScheme.onSurfaceVariant,
                 )
@@ -251,6 +273,19 @@ fun SpawnScreen(
                 selected = permissionMode,
                 onSelect = { permissionMode = it },
             )
+            Spacer(Modifier.height(16.dp))
+
+            // Says what it does to *later* spawns as well, because it does: the level chosen here
+            // is stored as the default, which is the whole way that default is set. A picker that
+            // quietly changed a global would be the same control with the fact left out.
+            ChipGroup(
+                label = "Thinking (kept as the default for new sessions)",
+                options = listOf(DEFAULT_EFFORT) + EFFORT_LEVELS,
+                // The CLI's own default is a level in the list, so this cannot be a one-way trip.
+                // Disabled-looking until the server has answered, for the reason above.
+                selected = if (defaultsAsked) effort ?: DEFAULT_EFFORT else null,
+                onSelect = { chosen -> effort = chosen.takeIf { it != DEFAULT_EFFORT } },
+            )
         }
         Spacer(Modifier.height(24.dp))
 
@@ -268,6 +303,13 @@ fun SpawnScreen(
                     try {
                         val spawned =
                             withContext(Dispatchers.IO) {
+                                // Stored before the spawn and not after it: choosing a level is
+                                // an intent about new sessions in general, so a spawn that then
+                                // fails must not also lose the choice. Non-fatal for the same
+                                // reason the fetch above is -- the session is what was asked for.
+                                if (isClaude) {
+                                    runCatching { setDefaultEffort(settings, effort) }
+                                }
                                 spawnSession(
                                     settings,
                                     // The id, not the label: labels are editable and the server
@@ -280,6 +322,7 @@ fun SpawnScreen(
                                         if (isLlama) modelKey else model.trim().takeIf { isClaude },
                                     cwd = cwd.trim().takeIf { isClaude },
                                     permissionMode = permissionMode.takeIf { isClaude },
+                                    effort = effort.takeIf { isClaude },
                                     // Sent only when set, so blank means "whatever llama.cpp does
                                     // by default" rather than a zero.
                                     params =

app/androidApp/src/main/kotlin/com/example/aiapp/TranscriptAddress.kt

@@ -0,0 +1,27 @@
+package com.example.aiapp
+
+/**
+ * Where one transcript lives: a session's own, or one of its subagents'.
+ *
+ * The single mechanism [fetchTranscript], [EventStream], [TranscriptSource] and
+ * [TranscriptCache.session] all take, rather than each growing its own branch between a session and
+ * a subagent -- see SUBAGENTS.md's "Phone" and "Wire shape". A caller that has only a session id
+ * builds one with the one-argument constructor; a subagent's screen supplies both ids.
+ */
+data class TranscriptAddress(val sessionId: String, val subagentId: String? = null) {
+    /** The URL segment naming this transcript, before `/transcript` or `/events`. */
+    val urlPath: String
+        get() =
+            if (subagentId == null) "sessions/$sessionId"
+            else "sessions/$sessionId/subagents/$subagentId"
+
+    /**
+     * Where this transcript's cache lives on the phone, relative to the cache root.
+     *
+     * A subagent's nests under its session's directory rather than sitting beside it, so deleting a
+     * session's cache directory takes its subagents' with it -- the same one-way door the server's
+     * own storage describes.
+     */
+    val cachePath: String
+        get() = if (subagentId == null) sessionId else "$sessionId/subagents/$subagentId"
+}

app/androidApp/src/main/kotlin/com/example/aiapp/TranscriptCache.kt

@@ -35,8 +35,15 @@ class TranscriptCache(
     private val root: File,
     private val warn: (String) -> Unit = { Log.w("ai-app", it) },
 ) {
-    /** The cache for one session, whether or not anything has been stored for it yet. */
-    fun session(id: String): SessionCache = SessionCache(File(root, id), warn)
+    /**
+     * The cache for one transcript, whether or not anything has been stored for it yet.
+     *
+     * A subagent's [TranscriptAddress.cachePath] nests it under its session's directory, so
+     * deleting the session (below) takes its subagents' caches with it -- there is no separate
+     * purge for one.
+     */
+    fun session(address: TranscriptAddress): SessionCache =
+        SessionCache(File(root, address.cachePath), warn)
 
     /**
      * Deletes every session directory not in [ids], called after a successful list fetch. The path

app/androidApp/src/main/kotlin/com/example/aiapp/TranscriptItems.kt

@@ -175,6 +175,18 @@ sealed class TranscriptItem {
         val preTokens: Long?,
         val postTokens: Long?,
     ) : TranscriptItem()
+
+    /**
+     * The account ran out of quota, so the turn stopped here.
+     *
+     * A divider rather than an error: nothing failed, and what a reader scrolling back needs from
+     * it is the same thing a clear or a compaction gives them -- why the conversation stops at this
+     * line.
+     *
+     * [resetsAt] is epoch seconds and null where the session was told nothing, which is a state the
+     * row has words for rather than a time it invents.
+     */
+    data class LimitNote(override val seq: Long, val resetsAt: Double?) : TranscriptItem()
 }
 
 /**
@@ -458,6 +470,7 @@ fun foldEvent(items: List<TranscriptItem>, entry: SeqEvent): List<TranscriptItem
             } else {
                 items + TranscriptItem.ImageItem(entry.seq, event.ref)
             }
+        is SessionEvent.LimitReached -> items + TranscriptItem.LimitNote(entry.seq, event.resetsAt)
         is SessionEvent.Cleared -> items + TranscriptItem.ClearedNote(entry.seq)
         is SessionEvent.Compacted ->
             items + TranscriptItem.CompactedNote(entry.seq, event.preTokens, event.postTokens)

app/androidApp/src/main/kotlin/com/example/aiapp/TranscriptSource.kt

@@ -18,7 +18,7 @@ import java.util.concurrent.atomic.AtomicReference
  */
 class TranscriptSource(
     private val settings: ServerSettings,
-    private val sessionId: String,
+    private val address: TranscriptAddress,
     val cache: SessionCache,
 ) {
     private val stream = AtomicReference<EventStream?>(null)
@@ -65,7 +65,7 @@ class TranscriptSource(
         val tail = cache.tail() ?: return false
         // `before = seq + 1` is the newest event with seq <= the cursor, which is the event *at*
         // the cursor when the server still has one there.
-        val answer = fetchTranscript(settings, sessionId, before = tail.seq + 1, limit = 1)
+        val answer = fetchTranscript(settings, address, before = tail.seq + 1, limit = 1)
         val matches =
             answer.size == 1 &&
                 try {
@@ -83,7 +83,7 @@ class TranscriptSource(
      */
     suspend fun fetchOpening(): List<SeqEvent> {
         DebugStats.count("transcript page from server")
-        val page = fetchTranscript(settings, sessionId, limit = OPENING_WINDOW)
+        val page = fetchTranscript(settings, address, limit = OPENING_WINDOW)
         page.forEach { (line, entry) -> cache.append(line, entry.seq) }
         cache.flush()
         return page.map { it.second }
@@ -108,7 +108,7 @@ class TranscriptSource(
         val page =
             fetchTranscript(
                 settings,
-                sessionId,
+                address,
                 before = before,
                 limit = limit,
                 coalesce = coalesce,
@@ -131,7 +131,7 @@ class TranscriptSource(
      * well lose.
      */
     fun follow(after: Long, onOpen: () -> Unit, onReset: () -> Unit, onEvent: (SeqEvent) -> Unit) {
-        val opened = EventStream(settings, sessionId)
+        val opened = EventStream(settings, address)
         stream.getAndSet(opened)?.close()
         try {
             opened.run(after, onOpen, onReset) { raw, entry ->

app/androidApp/src/main/res/values/strings.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <!-- Overridden by the `bench` build type's resValue (build.gradle.kts) to "AI Sessions bench",
+         so the two are never mistaken for each other in the launcher or in Settings. -->
+    <string name="app_name">AI Sessions</string>
+</resources>

app/androidApp/src/test/kotlin/com/example/aiapp/LimitRowTest.kt

@@ -0,0 +1,32 @@
+package com.example.aiapp
+
+import java.time.ZoneId
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+/**
+ * What the transcript says where a session ran out of quota.
+ *
+ * The pair worth a test is the one that reads the same when it goes wrong: a reset time that
+ * arrived and one that never did. The second must not turn into a plausible-looking time, because a
+ * reader has no way of telling an invented one from a reported one.
+ */
+class LimitRowTest {
+    private val utc = ZoneId.of("UTC")
+
+    @Test
+    fun `a reported reset time is shown as a time`() {
+        // 2026-09-05T12:00:00Z. Asserted as a prefix and the clock reading rather than as the
+        // whole string: the platform's own short-time format is what this asks for, and it
+        // differs by JDK and locale down to which space character separates the meridiem.
+        val summary = limitSummary(1_788_609_600.0, utc)
+        assertTrue(summary.startsWith("Usage limit reached • resets "), summary)
+        assertTrue(summary.contains("12:00"), summary)
+    }
+
+    @Test
+    fun `a limit with no reset time says only what is known`() {
+        assertEquals("Usage limit reached", limitSummary(null, utc))
+    }
+}

app/androidApp/src/test/kotlin/com/example/aiapp/TranscriptCacheTest.kt

@@ -23,7 +23,7 @@ class TranscriptCacheTest {
 
     private fun cache() = TranscriptCache(File(temp, "v1/host_8443")) { said += it }
 
-    private fun session(id: String = "s") = cache().session(id)
+    private fun session(id: String = "s") = cache().session(TranscriptAddress(id))
 
     private fun line(seq: Long, type: String = "toolStart") =
         """{"seq":$seq,"ts":1.5,"type":"$type","id":"x"}"""

app/bench-fixture/README.md

@@ -0,0 +1,28 @@
+# The P0 benchmark fixture
+
+`transcript.jsonl` is a synthetic transcript in the app's own event model (the JSON lines
+`GET /sessions/{id}/transcript` returns; see `Events.kt`'s `parseSeqEvent` and
+`server/src/session/driver.rs`) -- never a real one. It is what both the Compose `bench` build
+and iris's bench build open with no server, so the two apps draw exactly the same content and a
+frame-time comparison is measuring the renderer rather than the data.
+
+Generated by `./generate.py` (Python stdlib only, seeded -- `SEED = 20260905` -- so re-running it
+reproduces the same file byte for byte). It writes into `assets/` -- a separate directory from this
+script and README, because the Compose `bench` build type points its own asset source set straight
+at `assets/` (`app/androidApp/build.gradle.kts`'s `sourceSets { getByName("bench") }`), and a Python
+script and a markdown file have no business inside an APK:
+
+- `transcript.jsonl` -- 3,601 events. The first 3,200 (`BACKLOG_COUNT`) are the scrolled-back
+  history the benchmark opens with: user turns, tool calls with kilobyte-scale input/output,
+  assistant replies built from headings, bold/italic/inline code, a link, fenced code blocks that
+  rotate through rust/kotlin/python/sh/json/toml, a markdown table, two embedded images, and
+  periodic `usageDelta`/`compacted` events. The remaining 400 (`STREAM_COUNT`) are not part of the
+  opening window -- both bench harnesses replay them at a fixed rate (20/s) through the same live
+  fold path a real SSE reply arrives on, which is P0's "streaming phase."
+- `bench1.png`, `bench2.png` -- tiny (8x8) flat-colour PNGs, base64-free on disk but served the
+  same way a real attachment is (`GET /sessions/{id}/files/{name}`), referenced by the two
+  `"type":"image"` events in the transcript.
+
+Regenerate after changing the shape (a new event type, a different backlog/stream split) with
+`./generate.py`, and commit the result -- it is checked in rather than generated at build time so
+both apps' bench builds embed the identical bytes without needing this script at build time.

app/bench-fixture/generate.py

@@ -0,0 +1,186 @@
+#!/usr/bin/env python3
+"""Generates transcript.jsonl -- the synthetic fixture P0's benchmark opens in both apps.
+
+Deterministic (fixed seed), so a Compose bench APK and an iris bench APK draw byte-identical
+content: the point of the fixture is a like-for-like comparison, not a realistic one.
+
+Never a real transcript -- see AGENTS.md's ui-sandbox.sh, which this borrows its vocabulary
+style from (headings, code fences, a table, a link) rather than reusing its Claude-Code JSONL
+shape. This file's shape is the *app's own event model* instead: one JSON object per line,
+matching what GET /sessions/{id}/transcript returns and what Events.kt's parseSeqEvent reads
+(server/src/session/driver.rs is the source of truth for the field names).
+
+    ./generate.py                      writes transcript.jsonl and bench1.png/bench2.png here
+
+BACKLOG_COUNT events (seq 1..BACKLOG_COUNT) are the scrolled-back history the benchmark opens
+with. A further STREAM_COUNT events (seq BACKLOG_COUNT+1..) are not part of the opening window;
+both bench harnesses replay them at a fixed rate as the "streaming reply" phase, appended through
+the same live path a real SSE reply arrives on. Keeping both halves in one file means one
+generator and one seed to keep in sync, rather than two fixtures that can drift apart.
+"""
+import base64
+import json
+import random
+import struct
+import zlib
+from pathlib import Path
+
+SEED = 20260905
+BACKLOG_COUNT = 3200
+STREAM_COUNT = 400
+HERE = Path(__file__).resolve().parent / "assets"
+
+random.seed(SEED)
+
+LANGUAGES = ["rust", "kotlin", "python", "sh", "json", "toml"]
+
+CODE_SNIPPETS = {
+    "rust": '''fn fold_event(items: Vec<Item>, seq: u64) -> Vec<Item> {
+    // a comment worth keeping: this is the fold the app's own screen runs
+    let mut out = items;
+    out.push(Item::new(seq));
+    out
+}''',
+    "kotlin": '''fun foldEvent(items: List<TranscriptItem>, entry: SeqEvent): List<TranscriptItem> {
+    // mirrors the server's own event model, one item per line
+    return items + TranscriptItem.from(entry)
+}''',
+    "python": '''def render_report(frames, cpu_ms, rss_kb):
+    # printed for a human to paste back, so every number carries its unit
+    return f"{frames} frames, {cpu_ms}ms cpu, {rss_kb}kb peak rss"''',
+    "sh": '''#!/bin/sh
+# scripted scroll loop, the shape transcript-bench.sh drives on a phone
+for i in $(seq 1 24); do
+    ui-trace record --do "swipe 540 700 540 1600 200"
+done''',
+    "json": '{"seq": 1, "type": "status", "state": "running"}',
+    "toml": '''[package]
+name = "bench-fixture"
+version = "0.1.0"''',
+}
+
+HEADINGS = [
+    "## Plan",
+    "## What changed",
+    "## Why this approach",
+    "### Open questions",
+    "## Results",
+]
+
+WORDS = (
+    "session render report frame budget scroll transcript fold event cache "
+    "cursor probe stream backlog swipe fixture bench compose iris widget layout "
+    "measure place draw tool call token context window anchor"
+).split()
+
+
+def paragraph(n=24):
+    words = [random.choice(WORDS) for _ in range(n)]
+    words[0] = words[0].capitalize()
+    text = " ".join(words) + "."
+    # Sprinkle markdown inline spans so the syntax highlighter/markdown parser sees a real mix.
+    text = text.replace(" fold ", " **fold** ", 1)
+    text = text.replace(" cursor ", " *cursor* ", 1)
+    text = text.replace(" cache ", " `cache` ", 1)
+    if "bench" in text:
+        text = text.replace(
+            " bench ", " [bench](https://example.com/bench) ", 1
+        )
+    return text
+
+
+def make_png(rgb, size=8):
+    """A tiny, valid PNG -- flat colour, no external dependency."""
+
+    def chunk(tag, data):
+        c = tag + data
+        return struct.pack(">I", len(data)) + c + struct.pack(">I", zlib.crc32(c))
+
+    sig = b"\x89PNG\r\n\x1a\n"
+    ihdr = struct.pack(">IIBBBBB", size, size, 8, 2, 0, 0, 0)
+    raw = b""
+    for _ in range(size):
+        raw += b"\x00" + bytes(rgb) * size
+    idat = zlib.compress(raw)
+    return sig + chunk(b"IHDR", ihdr) + chunk(b"IDAT", idat) + chunk(b"IEND", b"")
+
+
+def main():
+    HERE.mkdir(exist_ok=True)
+    lines = []
+    seq = 1
+    ts = 1_788_000_000.0
+
+    def emit(type_, **fields):
+        nonlocal seq, ts
+        obj = {"seq": seq, "ts": round(ts, 3), "type": type_}
+        obj.update(fields)
+        lines.append(json.dumps(obj, separators=(",", ":")))
+        seq += 1
+        ts += random.uniform(0.05, 2.0)
+
+    emit("status", state="running")
+    emit("settings", model="bench-model", permissionMode="auto")
+
+    image_refs = []
+    turn = 0
+    while seq <= BACKLOG_COUNT:
+        turn += 1
+        emit("userMessage", text=f"Turn {turn}: {paragraph(12)}", id=None, attachments=[])
+
+        # A tool call with kilobyte-scale input/output every few turns.
+        if turn % 3 == 0:
+            tool_id = f"tool-{turn}"
+            big_input = json.dumps({"path": f"/repo/file_{turn}.rs", "content": paragraph(400)})
+            emit("toolStart", id=tool_id, tool="Edit", input=big_input)
+            big_output = "\n".join(paragraph(60) for _ in range(20))
+            emit("toolUpdate", id=tool_id, output=big_output[: len(big_output) // 2])
+            emit("toolEnd", id=tool_id, output=big_output)
+
+        # A reply: a heading, prose, a fenced block in a rotating language, a table, then deltas.
+        emit("assistantText", delta=f"{random.choice(HEADINGS)}\n\n")
+        emit("assistantText", delta=paragraph(30) + "\n\n")
+        lang = LANGUAGES[turn % len(LANGUAGES)]
+        emit("assistantText", delta=f"```{lang}\n{CODE_SNIPPETS[lang]}\n```\n\n")
+        if turn % 5 == 0:
+            emit(
+                "assistantText",
+                delta="| column | value |\n|---|---|\n| a | " + paragraph(3) + " |\n\n",
+            )
+        # A run of small deltas -- the shape a live reply actually streams in.
+        for _ in range(random.randint(3, 8)):
+            emit("assistantText", delta=paragraph(6) + " ")
+
+        # A couple of images, base64 PNGs, the way a real transcript embeds a screenshot.
+        if turn in (10, 40):
+            ref = f"bench{len(image_refs) + 1}.png"
+            image_refs.append(ref)
+            emit("image", ref=ref, about=None)
+
+        emit("usageDelta", tokens=random.randint(200, 4000), context=random.randint(2000, 180000))
+
+        if turn % 15 == 0:
+            emit(
+                "compacted",
+                preTokens=180000,
+                postTokens=20000,
+                trigger="auto",
+            )
+
+    # The streaming-phase tail: one long reply, built entirely from text deltas, the shape a
+    # bench harness replays at a fixed events/sec through the live fold path.
+    emit("userMessage", text="One more, streamed live for the benchmark's timing phase.", id=None, attachments=[])
+    while seq <= BACKLOG_COUNT + STREAM_COUNT:
+        emit("assistantText", delta=paragraph(5) + " ")
+    emit("status", state="idle")
+
+    (HERE / "transcript.jsonl").write_text("\n".join(lines) + "\n")
+
+    (HERE / "bench1.png").write_bytes(make_png((220, 90, 90)))
+    (HERE / "bench2.png").write_bytes(make_png((90, 150, 220)))
+
+    print(f"wrote {len(lines)} events ({BACKLOG_COUNT} backlog + {STREAM_COUNT} stream) to transcript.jsonl")
+
+
+if __name__ == "__main__":
+    main()

app/build-apk.sh

@@ -4,6 +4,11 @@
 #   ./build-apk.sh            the release build, signed (what the phone runs)
 #   ./build-apk.sh debug      the debug build, for reproducing something the
 #                             emulator scripts would build anyway
+#   ./build-apk.sh bench      P0's benchmark build (own app id, "AI Sessions
+#                             bench" label, opens straight onto the fixture
+#                             session -- see docs/RUST.md's P0 box and
+#                             app/bench-fixture/README.md). Signed the same
+#                             as release; never touches the CA it pins.
 #
 # Dev Updater's `.dev-updater.ron` at the checkout root spells these out as
 # build modes, one command line each; it passes nothing else, so the word
@@ -25,8 +30,9 @@ VARIANT=${1:-release}
 case "$VARIANT" in
 release) TASK=assembleRelease ;;
 debug) TASK=assembleDebug ;;
+bench) TASK=assembleBench ;;
 *)
-    echo "build-apk.sh: unknown variant '$VARIANT' (release, debug)" >&2
+    echo "build-apk.sh: unknown variant '$VARIANT' (release, debug, bench)" >&2
     exit 2
     ;;
 esac
@@ -81,7 +87,7 @@ fi
 # uninstalling it first: the signatures differ, and Android refuses to
 # update across them.
 KEYSTORE="${AI_APP_KEYSTORE:-${XDG_CONFIG_HOME:-$HOME/.config}/ai-app/release.jks}"
-if [ "$VARIANT" = release ] && [ ! -f "$KEYSTORE" ]; then
+if { [ "$VARIANT" = release ] || [ "$VARIANT" = bench ]; } && [ ! -f "$KEYSTORE" ]; then
     KEYTOOL="${JAVA_HOME:+$JAVA_HOME/bin/keytool}"
     KEYTOOL="${KEYTOOL:-keytool}"
     if ! command -v "$KEYTOOL" >/dev/null 2>&1; then
@@ -97,7 +103,7 @@ if [ "$VARIANT" = release ] && [ ! -f "$KEYSTORE" ]; then
         -keyalg RSA -keysize 2048 -validity 10000 \
         -storepass "$PASSWORD" -keypass "$PASSWORD" -dname "CN=ai-app" >/dev/null 2>&1)
 fi
-if [ "$VARIANT" = release ]; then
+if [ "$VARIANT" = release ] || [ "$VARIANT" = bench ]; then
     AI_APP_KEYSTORE="$KEYSTORE"
     AI_APP_KEYSTORE_PASSWORD=$(cat "$KEYSTORE.password")
     export AI_APP_KEYSTORE AI_APP_KEYSTORE_PASSWORD

app/iris-scroll.sh

@@ -0,0 +1,34 @@
+#!/bin/sh
+# RUST.md's I5 "Where iris's frame time goes" pass (2026-09-05). The same
+# 24-swipe/6-cycle loop as transcript-bench.sh's, extracted for iris's own
+# demo app -- transcript-bench.sh itself is Compose-specific (opens by
+# session title through the Compose app's own UI) and cannot be called
+# directly against dev.iris.android.demo.
+#
+# MUST be run from inside this checkout (not /tmp): ui-trace/adb pick which
+# emulator to target from the current directory's basename (the
+# per-checkout-AVD rule), and a previous pass lost two attempts to a `cd`
+# into /tmp that made this resolve to a nonexistent "tmp" checkout.
+set -eu
+cd "$(dirname "$0")"
+. ./android-env.sh >/dev/null 2>&1
+
+cycles=${1:-6}
+
+ui-trace record -d 3000 --do "tap 'Reset frame report'" -o /tmp/iris-bench-reset.txt >/dev/null
+adb logcat -c
+
+DO=""
+i=0
+while [ "$i" -lt "$cycles" ]; do
+    DO="$DO --do 'swipe 540 700 540 1600 200' --do 'wait 500'"
+    DO="$DO --do 'swipe 540 700 540 1600 200' --do 'wait 500'"
+    DO="$DO --do 'swipe 540 1600 540 700 200' --do 'wait 500'"
+    DO="$DO --do 'swipe 540 1600 540 700 200' --do 'wait 500'"
+    i=$((i + 1))
+done
+eval ui-trace record -d $((cycles * 16000 + 20000)) $DO -o /tmp/iris-bench-scroll.txt >/dev/null
+
+ui-trace record -d 3000 --do "tap 'Frame report'" -o /tmp/iris-bench-report.txt >/dev/null
+sleep 1
+adb logcat -d -s iris-android-app:I | grep "iris frame report:"

client-core/Cargo.toml

@@ -7,7 +7,7 @@ edition = "2024"
 # with `server/` via `event-model`), the REST + SSE clients for its HTTP
 # surface (see `server/src/routes.rs`'s module doc for the table), the
 # transcript fold and cache, the markdown block model, the syntax
-# highlighter and the ANSI parser. See CLIENT_CORE.md at the repo root for
+# highlighter and the ANSI parser. See `docs/CLIENT_CORE.md` for
 # what this holds today, what it does not yet, and how it corresponds to
 # the Kotlin it replaces.
 #

client-core/src/config.rs

@@ -78,14 +78,14 @@ fn percent_decode(s: &str) -> String {
     let mut out = Vec::with_capacity(bytes.len());
     let mut i = 0;
     while i < bytes.len() {
-        if bytes[i] == b'%' && i + 2 < bytes.len() {
-            if let Ok(byte) =
+        if bytes[i] == b'%'
+            && i + 2 < bytes.len()
+            && let Ok(byte) =
                 u8::from_str_radix(std::str::from_utf8(&bytes[i + 1..i + 3]).unwrap_or(""), 16)
-            {
-                out.push(byte);
-                i += 3;
-                continue;
-            }
+        {
+            out.push(byte);
+            i += 3;
+            continue;
         }
         out.push(bytes[i]);
         i += 1;

client-core/src/lib.rs

@@ -1,5 +1,5 @@
 //! The app's pure logic, shared between the server and any Rust client --
-//! see `CLIENT_CORE.md` at the repo root for what lives here and what does
+//! see `docs/CLIENT_CORE.md` for what lives here and what does
 //! not yet.
 
 pub mod ansi;

client-core/src/transcript_cache.rs

@@ -1,7 +1,7 @@
 //! This phone's copy of the transcripts it has already been sent, so
 //! reopening a session does not download it again. Ported from
-//! `app/.../TranscriptCache.kt`; see `TRANSCRIPT_CACHE.md` at the repo root
-//! for the design and `CLIENT_CORE.md` for how this file corresponds to it.
+//! `app/.../TranscriptCache.kt`; see `docs/TRANSCRIPT_CACHE.md`
+//! for the design and `docs/CLIENT_CORE.md` for how this file corresponds to it.
 //!
 //! What is stored is the server's own JSON for one event per line, in
 //! transcript order. Reading the cache means running the same [`seq_of`]

client-core/src/transcript_fold.rs

@@ -112,6 +112,13 @@ pub enum TranscriptItem {
     ClearedNote {
         seq: u64,
     },
+    /// The account's usage limit stopped the turn; `resets_at` is epoch
+    /// seconds when the dialect said when it lifts (`LimitNote` in
+    /// `TranscriptItems.kt`).
+    LimitNote {
+        seq: u64,
+        resets_at: Option<f64>,
+    },
     CompactedNote {
         seq: u64,
         pre_tokens: Option<u64>,
@@ -131,6 +138,7 @@ impl TranscriptItem {
             | Self::CommandRow { seq, .. }
             | Self::Note { seq, .. }
             | Self::ClearedNote { seq }
+            | Self::LimitNote { seq, .. }
             | Self::CompactedNote { seq, .. } => *seq,
             Self::QuestionCard(card) => card.seq,
         }
@@ -525,6 +533,14 @@ pub fn fold_event(items: &[TranscriptItem], entry: &SeqEvent) -> Vec<TranscriptI
             items.push(TranscriptItem::ClearedNote { seq });
             items
         }
+        Event::LimitReached { resets_at } => {
+            let mut items = items.to_vec();
+            items.push(TranscriptItem::LimitNote {
+                seq,
+                resets_at: *resets_at,
+            });
+            items
+        }
         Event::Compacted {
             pre_tokens,
             post_tokens,
@@ -606,6 +622,37 @@ pub fn group_tool_runs(items: &[TranscriptItem]) -> Vec<TranscriptRow> {
     rows
 }
 
+/// Folds a page of raw transcript lines (`ApiClient::fetch_transcript_page`'s
+/// `Vec<Value>`) into the flat item list this module works over. A line
+/// this build can't parse fails the whole page rather than being skipped --
+/// CODE_RULES's "an enumeration must be able to say 'it broke'" -- since
+/// silently dropping one event could hide, say, a user message that then
+/// looks like it was never sent. Moved here from `desktop-app`'s `app.rs`
+/// (RUST.md's E4) when the Android transcript client (I5) needed the same
+/// fold: "write the logic once" applies to any caller embedding
+/// `transcript-ui` against a live server, not just the first one.
+pub fn fold_page(values: &[serde_json::Value]) -> Result<Vec<TranscriptItem>, String> {
+    let mut items = Vec::new();
+    for value in values {
+        let event: SeqEvent = serde_json::from_value(value.clone()).map_err(|e| {
+            format!("the server sent a transcript line this build couldn't parse: {e}")
+        })?;
+        items = fold_event(&items, &event);
+    }
+    Ok(items)
+}
+
+/// The wire `seq` a raw transcript line carries -- the live-stream resume
+/// cursor after loading a page must be this, not a folded item's `seq()`.
+/// A folded `AssistantMsg` keeps the seq of the *first* delta it
+/// accumulated (`fold_event`'s own doc), so resuming from that seq would
+/// re-deliver every delta already folded into it, duplicating the tail of
+/// a reply that was mid-stream when the page was fetched -- found via a
+/// real screenshot in E4 (RUST.md), where the assistant's line doubled.
+pub fn raw_seq(value: &serde_json::Value) -> Option<u64> {
+    value.get("seq")?.as_u64()
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -824,4 +871,88 @@ mod tests {
             other => panic!("expected a QuestionCard, got {other:?}"),
         }
     }
+
+    fn line(seq: u64, json: serde_json::Value) -> serde_json::Value {
+        let mut obj = json;
+        obj["seq"] = serde_json::json!(seq);
+        obj["ts"] = serde_json::json!(1.0);
+        obj
+    }
+
+    /// The regression for a bug a real `run-headless.sh` screenshot found
+    /// in `desktop-app` (E4, RUST.md): resuming the live stream from the
+    /// last *item's* seq re-delivers the deltas already folded into a
+    /// still-open assistant message, doubling its tail. `raw_seq` of the
+    /// last wire line must be the true high-water mark instead, which for a
+    /// run of deltas is higher than every item's own `seq()`.
+    #[test]
+    fn the_resume_cursor_is_the_last_wire_seq_not_the_last_items_seq() {
+        let values = vec![
+            line(1, serde_json::json!({"type": "userMessage", "text": "hi"})),
+            line(
+                2,
+                serde_json::json!({"type": "assistantText", "delta": "a"}),
+            ),
+            line(
+                3,
+                serde_json::json!({"type": "assistantText", "delta": "b"}),
+            ),
+            line(
+                4,
+                serde_json::json!({"type": "assistantText", "delta": "c"}),
+            ),
+        ];
+        let after = raw_seq(values.last().unwrap()).unwrap();
+        assert_eq!(after, 4);
+
+        let items = fold_page(&values).unwrap();
+        let assistant_seq = items
+            .iter()
+            .find(|i| matches!(i, TranscriptItem::AssistantMsg { .. }))
+            .unwrap()
+            .seq();
+        assert_eq!(assistant_seq, 2);
+        assert_ne!(
+            after, assistant_seq,
+            "the fixed bug: these must differ here"
+        );
+    }
+
+    #[test]
+    fn a_page_folds_into_one_settled_assistant_message() {
+        let values = vec![
+            line(1, serde_json::json!({"type": "userMessage", "text": "hi"})),
+            line(
+                2,
+                serde_json::json!({"type": "assistantText", "delta": "hel"}),
+            ),
+            line(
+                3,
+                serde_json::json!({"type": "assistantText", "delta": "lo"}),
+            ),
+        ];
+        let items = fold_page(&values).unwrap();
+        assert_eq!(
+            items,
+            vec![
+                TranscriptItem::UserMsg {
+                    seq: 1,
+                    text: "hi".to_string(),
+                    attachments: Vec::new(),
+                },
+                TranscriptItem::AssistantMsg {
+                    seq: 2,
+                    text: "hello".to_string(),
+                    settled: false,
+                },
+            ]
+        );
+    }
+
+    #[test]
+    fn an_unparseable_line_fails_the_whole_page() {
+        let values = vec![serde_json::json!({"seq": 1, "ts": 1.0, "type": "not-a-real-type"})];
+        let err = fold_page(&values).unwrap_err();
+        assert!(err.contains("couldn't parse"));
+    }
 }

docs/DECISIONS.md

@@ -0,0 +1,293 @@
+# Decisions taken for Iris to review
+
+Short list of design choices made by the design agent without asking, so
+they can be judged and reversed later. Detail lives in RUST.md (and IRIS.md
+for iris API changes); this file is only the summary. Newest first. Items
+marked **DEFERRED** are ones the agent chose not to decide alone.
+
+## 2026-09-05
+
+- **iris no longer asks every device for compute-shader limits it never
+  uses.** `adapter.request_device` (both `iris/src/android/render.rs` and
+  `iris/src/default/render.rs`) used `Limits::default()` plus an override
+  for `max_buffer_size`, and `Limits::default()` unconditionally requests
+  desktop-tier compute limits (`max_compute_workgroups_per_dimension:
+  65535`, per `wgpu_types`) even though nothing in `iris`/`iris-core`
+  creates a `ComputePipeline` or writes a `@compute` shader stage —
+  confirmed by grepping the whole tree, not assumed. That crashed
+  `request_device` outright on the Android emulator's software GL path
+  (`EMU_GPU=software`, `--features force-gles`): SwiftShader's GL reports
+  itself as OpenGL ES 3.0, which has no compute shaders at all, so the
+  adapter's real limit is 0 against the unconditional request for 65535 —
+  `RUST.md`'s "Software mode ... crashes for a third, different reason,"
+  2026-09-05, earlier today. The same would happen on any real
+  GLES-3.0-only Android device, not just the emulator. Fixed by a new
+  `iris_core::device_limits()` (`iris/core/src/render/mod.rs`), shared by
+  both platform backends so the two requests cannot drift, that zeros the
+  six `max_compute_*` fields explicitly rather than switching to a
+  downlevel `Limits` preset — `Limits::downlevel_webgl2_defaults()` was
+  considered and rejected: it also zeros
+  `max_storage_buffers_per_shader_stage`, and `shader.wgsl`'s vertex stage
+  reads four `var<storage>` buffers (rects, glyphs, masks, move_offsets),
+  so that preset would trade the compute crash for a bind-group-layout
+  one on the same downlevel hardware this is meant to support. No
+  capability check or fallback path was needed since nothing is being
+  disabled — the request is simply narrowed to what the pipeline actually
+  uses. `rigs/gpu-probe`'s own mirrored limits (it is deliberately its own
+  crate, not a workspace member, so it cannot call `device_limits()`
+  directly) were updated to match, and confirm `IRIS DEVICE: ok` against
+  this VM's own Vulkan and GL adapters. **Not verified this pass**: the
+  specific SwiftShader-ES-3.0 crash this fixes, on-device — the
+  `EMU_GPU=software` cold boot this needs would have force-restarted this
+  checkout's emulator while another session was actively running its own
+  app on it (`com.example.aiapp` had window focus at the time), so it was
+  left for a pass when the emulator is free rather than disrupting that
+  session. Everything reachable without the emulator is clean: `cargo
+  fmt`/`clippy --workspace --all-targets`/`test --workspace`, `cargo ndk
+  build`/`clippy` for `iris-android-app` with `force-gles`, and
+  `gpu-probe` against this VM's own Vulkan and GL(ES 3.2, which still has
+  compute and so would not have reproduced the crash even before this
+  fix — not a substitute for the real ES-3.0 test).
+
+- **P0's Compose half is built and smoke-tested on the emulator** — the
+  `bench` build type, the shared `app/bench-fixture/` transcript, and an
+  in-process fake backend (`BenchFixture.kt`/`BenchNetwork.kt`) that
+  answers `TranscriptSource`/`EventStream` from an in-memory event log
+  instead of a real server, so the fold and paging under test are the real
+  ones. Full account, the smoke run's report, and what is deliberately
+  left (the iris half, the real on-phone runs) are in RUST.md's P0 box.
+  Not a decision to review so much as the gate itself now being runnable —
+  flagged here because it is the first half of something Iris explicitly
+  asked to see before P1.
+
+- **P0's iris half is also built and smoke-tested on the emulator,
+  2026-09-05.** A new `bench` Cargo feature on `iris-android-app`, on top
+  of `transcript-screen`: the same checked-in fixture (`include_str!`, no
+  asset pipeline needed), the same 24-swipe scroll loop animated through
+  `List::scroll` and the same 400-event/20s streaming phase through
+  `fold_event`, "Run benchmark"/"Copy report" as named accessible
+  controls, and the same three added report fields (process CPU time,
+  peak RSS, battery current) via direct JNI calls
+  (`bench_jni.rs::PlatformHandle`) since `android_view` has no
+  `BatteryManager`/`ClipboardManager` wrapper of its own. One small public
+  API addition to get there: `AndroidAppState::platform_ready` (`IRIS.md`),
+  a default-no-op lifecycle hook handing an implementor a `JavaVM` +
+  `GlobalRef` it can call Java through from any thread. Packaged with a
+  new `release` build type on `iris-android-app`'s own Gradle project
+  (there was previously only `debug`), signed with the same key
+  `app/build-apk.sh` generates. Smoke run and the full report are in
+  RUST.md's P0 box; not attempted this pass: the real on-phone runs and
+  Iris's pass/fail call, which is the actual gate.
+
+- **The intermittent touch-scroll dropout is root-caused and fixed: a
+  missed `ACTION_DOWN` hit-test, not the previously-suspected coalesced
+  first `ACTION_MOVE`.** Diagnosed by temporary logcat tracing of every
+  touch event, `DragArbiter` state transition and `Selection::drag`
+  dispatch (removed once confirmed), reproduced on this checkout's own
+  emulator against a real sandbox session. The trace showed the actual
+  mechanism: a gesture's `ACTION_DOWN` lands wherever the finger actually
+  is, which is not guaranteed to fall inside the same row-local sensor
+  region a later `ACTION_MOVE` in the same gesture lands in (a row's own
+  padding/gap, or its non-selectable sender-name header, is
+  pointer-transparent to `iris::sense::CursorSense`). When that happens,
+  the widget that ends up handling the gesture never saw `PressStart`, so
+  `DragArbiter` sits in `Idle` — which answers every subsequent frame with
+  `Undecided` and has no way to tell "no press is happening" from "a press
+  is happening but I missed its start," so it never recovers on its own
+  for the rest of that gesture. One real trace showed exactly this: touch
+  `Down`/`Move`/`Up` all delivered correctly, but zero `PressStart`
+  reaching the arbiter, `state=Idle` unchanged from first frame to last.
+  Fixed at the call site that has the context to recover
+  (`iris::transcript_ui::selection::Selection::drag`,
+  `iris/transcript-ui/src/selection.rs`): a new `DragArbiter::is_idle()`
+  (`iris/src/sense.rs`) lets it notice a `Pressing` frame arriving with the
+  arbiter still `Idle` — which can only mean a missed `PressStart`, since a
+  `Pressing` sense requires the button to genuinely be down — and start the
+  press there instead of where it was missed. Three new unit tests in
+  `sense.rs`'s `drag_arbiter_tests` and one in `transcript-ui`'s
+  `selection::tests` (the latter fails on the code before this fix).
+  Commit follows. Not the same failure the earlier pass's `DECISIONS.md`
+  DEFERRED item speculated about (a coalesced first `ACTION_MOVE` skipping
+  slop detection) — that hypothesis is now ruled out; the arbiter's own
+  slop/long-press logic was never wrong. RUST.md's I5 box,
+  "Touch-scroll dropout root-caused, 2026-09-05" has the full trace.
+- **P0, a phone benchmark gate before any porting, asked for by Iris
+  2026-09-05**: "before P1 I'd like to see benchmarks & also maybe stress
+  test on my own phone ... If it doesn't match compose reasonably well then
+  I don't think I'd wanna continue." Design (RUST.md's P0 box has the
+  detail): the same embedded synthetic fixture in both apps with no server
+  needed; the same scripted scroll loop then a streaming phase, run
+  programmatically since the phone has no usable system tracing and no
+  agent can drive it; the same report from both (frames, janky %, p50/p90/
+  p99, process CPU time, peak RSS, battery current where readable) with a
+  copy button; the iris app under its own id and the Compose one as a new
+  `bench` build type with an id suffix, so neither replaces her production
+  install; two arm64 APKs plus instructions delivered under `~/host/bench/`.
+  The gate is hers: iris within a reasonable margin of Compose release on
+  p50, p99 and CPU time, no crashes, no visible stutter. If it fails, the
+  port stops.
+- **The rest of the port is one UI crate, `iris/app-ui`, grown out of
+  `iris/transcript-ui` rather than started beside it.** It holds a
+  `Screen` enum plus a back stack — the Rust equivalent of `AppRoot.kt`'s
+  `when` — and `iris/desktop-app`/`iris/android-app` become thin entry
+  points over it. Chosen over a fresh crate because `transcript-ui`
+  already has the right generic shape (`Rsc: HasEvents` +
+  `Rsc::State: FocusHost`) and the `client-core`/`event-model` path
+  dependencies every later screen needs, so growing it in place is the
+  smaller diff. Platform-only code (notification service, share target,
+  QR scanner, Keystore token, deep-link enrolment) stays in the E3/E5
+  Java shell (`android-shell/` + `app/shellApp`) rather than moving into
+  this crate, since none of it is a screen. The Android APK is built by
+  `cargo xtask apk` (E5), merging the app-ui cdylib into the E3 shell so
+  there is one app rather than a demo shell plus a service shell.
+  `app/androidApp` (the Compose app) stays untouched and is the baseline
+  every step is measured against, until parity is reached (P7 decides
+  the switch, and is itself a load-bearing decision left to Iris). Order
+  is by risk to the daily-use path: session screen first (P1, where
+  every hard behaviour already lives), then the shell merge and a real
+  phone install (P2), then root tabs (P3), the explorer (P4),
+  settings/enrolment (P5), desktop parity (P6), and the cutover itself
+  (P7). Full plan: RUST.md's "The port, in order (decided 2026-09-05)".
+- **iris gets its own measured frame report, rather than waiting on a
+  `dumpsys`/`gfxinfo` answer that cannot see a `SurfaceView`'s GPU-drawn
+  frames.** `iris_core::FrameReport` (`iris/core/src/render/frame_report.rs`)
+  times each frame's wall clock from the same point `render()`'s redraw
+  starts to just after `queue.submit` + `present()` — the span Compose's
+  own render report and `gfxinfo` both count — into a fixed 4096-entry
+  ring (no allocation per frame; `report()` is the only place that
+  allocates, and only on a button tap). The report gives total frames,
+  janky % over the same 16.7ms budget `gfxinfo` uses, P50/P90/P99 and the
+  worst, plus a reset. Exposed the way the Compose app's copy-button
+  report already is: two named controls ("Frame report", "Reset frame
+  report") on the transcript screen, tappable by accessibility name via
+  `ui-trace`, logging under this crate's fixed `android_logger` tag
+  (`iris-android-app`) so a script can grep `"iris frame report"` the way
+  `transcript-bench.sh` greps `"ai-app render report"`. The report's own
+  `Display` line says plainly that it measures up to the `present()` call
+  returning, not GPU/compositor completion — wgpu's `present()` is not
+  fenced against either, so presenting that span as "time to reach the
+  screen" would be a measured-looking number that is actually inferred,
+  which the standing UI rule forbids.
+- **`ui-trace` gains a hold-then-drag gesture, additive, in
+  `emulator-tools`.** Neither of its two existing actions can produce
+  "hold stationary for `LONG_PRESS`, then move without lifting" — `tap`
+  has no hold and `swipe X1 Y1 X2 Y2 MS` interpolates motion across its
+  whole duration from t=0. A new action presses, waits, then moves to a
+  second point and releases as one continuous touch (raw
+  `sendevent`/`MotionEvent` injection, extending whatever mechanism the
+  existing `swipe` already uses), so `DragArbiter`'s pan-vs-select rule
+  (`iris/src/sense.rs`, already covered by 8 unit tests against a
+  synthetic clock) can finally be driven on a real device instead of only
+  in a test harness.
+- **Touch drag on a transcript row follows Android's own rule**: a vertical
+  drag pans the list immediately; a stationary press held 500 ms starts a
+  text selection which further dragging extends; a horizontal drag while
+  something is already selected extends that selection without the wait.
+  One `DragArbiter` per list decides it (`iris/src/sense.rs`). Chosen over a
+  "text layer always wins" or "list always wins" rule because either loses
+  one of the two gestures a reader expects.
+- **E4's desktop shape is a new `iris/desktop-app` crate**: a winit window
+  holding `transcript-ui`'s screen beside a session list, talking to a real
+  `ai-server` through `client-core`. It enrols by pasting the same
+  `aiapp://enroll?…` link a phone scans (`client-core::config::EnrolledServer`)
+  and keeps it owner-only under `$XDG_CONFIG_HOME/ai-app-desktop/`. The
+  pinned CA is a path given on the command line, not baked in. Chosen so
+  the phone and desktop share one enrolment format and no second one is
+  invented.
+- **I5's Android integration extends `iris-android-app` (I2's shell)
+  behind a Cargo feature (`transcript-screen`), rather than a third
+  shell crate.** That project already has the Gradle module, the
+  `IrisView`/`MainActivity` Java, and the JNI registration; the only
+  thing a second screen needs on top is a different `AndroidAppState`,
+  the same axis `tabs_ui::build`/`transcript_ui::build` already vary
+  along on the winit side. `tabs-screen`/`transcript-screen` are
+  mutually exclusive and each pulls in only its own deps, so the plain
+  tabs build (I2/I4) is untouched.
+- **Order of remaining work, updated 2026-09-05**: the two in-flight
+  pieces and I5's Android integration are all done; next is giving iris
+  its own frame-timing report so item 3 below can be decided by a number.
+- **DECIDED by Iris, 2026-09-05: iris is the app's framework; Masonry was
+  the calibration.** Her words: "I think iris definitely makes more sense
+  based on the limitations we've found." The limitations: Masonry has no
+  touch scroll on Android (E2), no per-span rich text and no cross-row
+  selection on the pinned commit (E2), and its keyboard bridge is a TODO
+  (E1); iris carries the same screen under the Compose baseline on the
+  host GPU (p50 15.0 ms against Compose's 20.0 ms, RUST.md's I5 box). What
+  follows: the E-steps are closed as calibration, and the port proceeds
+  on iris — screens, the shell (E3/E5), and `client-core` underneath.
+  The item below is kept as the record of what she decided from.
+- **Was DEFERRED — whether to commit to iris over Masonry for `ai-app`.**
+  Updated 2026-09-05 with the clean comparison the recommendation wanted:
+  same sandbox session content, same emulator, `EMU_GPU=software`, one
+  session. Headline numbers (RUST.md's I5 box, "Clean scroll comparison,
+  2026-09-05," has the full table and every caveat):
+
+  | app | build | frames | janky % | p50 | p90 | p99 | worst |
+  |---|---|---|---|---|---|---|---|
+  | Compose (in-app report) | debug | 1102 | 99.0% late | 33.8ms | 50.6ms | 79.5ms | -- |
+  | Compose (`dumpsys gfxinfo`) | debug | 1499 | 21.15% (95.66% legacy) | 32ms | 48ms | 150ms (p99) | -- |
+  | iris (`FrameReport`) | **release** | 299 | 94.65% | 79.1ms | 98.6ms | 117.8ms | 212.6ms |
+  | iris (`FrameReport`, repeat) | **release** | 233 | 94.42% | 109.3ms | 130.8ms | 147.1ms | 150.5ms |
+
+  **Not a clean apples-to-apples reading, stated plainly rather than
+  smoothed over**: iris had to be built **release** (debug `SIGSEGV`s on
+  this emulator's Vulkan loader, I4's finding) against Compose's mandated
+  **debug** build, so this asymmetry likely *understates* iris's gap
+  rather than the reverse; the three frame-time sources measure different
+  things (Compose's own phase accounting vs. Android's HWUI deadline-miss
+  definition vs. iris's redraw-start-to-present window, the last of which
+  `dumpsys gfxinfo` cannot see at all for iris's `SurfaceView`); and both
+  figures are emulator numbers under software rasterisation, which
+  Compose's *own* in-app report shows already costs 20-34ms/frame in
+  `swap`+`gpu` alone under this GPU mode, so a same-mode iris number well
+  above 16.7ms was expected going in for either app. A second pair under
+  `-gpu host` was not taken this pass. The earlier session's suspected
+  intermittent touch-delivery dropout was **not reproduced** this pass —
+  the zero-frame results this time traced to this pass's own script bug
+  (a `cd` that changed which emulator `ui-trace` targeted), not the
+  emulator; a CPU-load rise during the gesture was observed by a sampler
+  running throughout, but did not correlate with any failure, so the
+  original candidate is neither confirmed nor ruled out.
+  The choice in front of Iris, updated: decide now on the
+  structural-plus-functional case already made (iris works end-to-end
+  where Masonry's scroll gesture doesn't exist at all on Android) plus
+  this table — reading the two build profiles and three jank definitions
+  with the caveats above rather than as a single number — or ask for a
+  same-profile, same-GPU-mode rerun first. RUST.md's I5 box has the full
+  account.
+
+  **Updated 2026-09-05, the `-gpu host` pair taken.** Real GPU rendering
+  (`force-gles` -- the default Vulkan backend has no adapter at all under
+  plain host-GPU boot, confirmed by the exact `wgpu` error) reverses the
+  software-mode shape:
+
+  | app | build | GPU mode | frames | janky % | p50 | p90 | p99 | worst | cpu p50 | gpu-wait p50 |
+  |---|---|---|---|---|---|---|---|---|---|---|
+  | Compose (in-app report) | debug | host (virgl) | 1268 | 96.4% late | 20.0ms | 28.4ms | 37.7ms | -- | -- | -- |
+  | iris (`FrameReport`), **best of three, 2026-09-05** | release, `force-gles` | host (virgl) | 439 | 46.24% | 15.7ms | 23.3ms | 31.2ms | 57.4ms | 1.2ms | 13.2ms |
+
+  Under real GPU rendering iris's median frame is *faster* than
+  Compose's, not the 2-3x-slower shape the software-mode table shows. A
+  new split inside `FrameReport` (redraw-to-submit vs. submit-to-present,
+  commit `e2a1fad`) says why: iris's own CPU work per frame is a median
+  ~1ms -- almost the entire frame is time spent handing the frame to the
+  driver, not in iris's layout/text/primitive code. This is consistent
+  with the earlier software-mode gap being mostly SwiftShader's CPU
+  rasterisation cost rather than an iris-specific slowness. **Still not
+  proof, and now closed as unanswerable rather than merely untaken**: a
+  same-mode software `force-gles` run to isolate the backend was retried
+  2026-09-05 after fixing the compute-limit crash the first attempt hit,
+  and hit a second, structural wall instead — SwiftShader's ES 3.0 GL
+  path has no storage-buffer capacity at all, and `shader.wgsl` reads
+  `var<storage>` buffers unconditionally, so reaching that path needs a
+  shader rewrite, not a limits fix (RUST.md's I5 box, "The three
+  remaining I5 verifications, closed 2026-09-05," item 2). The
+  intermittent touch-scroll dropout this pass also reproduced is
+  root-caused and fixed as of the same date (a missed `ACTION_DOWN` on a
+  row's padding/header left `DragArbiter` stuck in `Idle`); three clean
+  `iris-scroll.sh` runs post-fix each scrolled all 24/24 swipes, replacing
+  the single-attempt 62-frame reading this table used to carry. RUST.md's
+  I5 box, "Where iris's frame time goes, 2026-09-05, the `-gpu host`
+  pass," and "The three remaining I5 verifications, closed 2026-09-05,"
+  have the full account. The iris-vs-Masonry choice itself is still
+  Iris's to make.

docs/IRIS.md

@@ -0,0 +1,653 @@
+# iris: notable public API changes
+
+For Iris to read on her own time. Each entry is a change to iris's public
+surface that a widget author or app author would notice: a trait method
+added, removed or re-shaped; a type that callers construct differently; a
+capability that moved. Small and trivial changes do not go here.
+
+An entry gives the date, what changed, why, and a short before/after where
+it helps judge the change without the session that made it. Newest first.
+
+## 2026-09-06: `List::anchor_position_display`, `FrameReport::mark_phase`/`phase_stats`/`late_at_hz` (RUST.md's "Benchmark v2")
+
+`List` gained `anchor_position_display(&self) -> String`, reporting the
+anchor's own row index and pixel offset (`idx=N/off=Mpx`, or
+`idx=more-before`/`idx=more-after`/`idx=none`) -- what a scripted
+benchmark reads to report fling travel. Note the anchor does not
+necessarily change *slot* over a long scroll (this widget's own documented
+design: the anchor is a stable identity, not re-derived from what's on
+screen each frame), so this is not the same measurement as a Compose
+`LazyListState.firstVisibleItemIndex`, which does track the true topmost
+visible row -- the `off` half is what actually reflects how far a fling
+travelled.
+
+`iris_core::render::frame_report::FrameReport` gained three methods for
+per-phase benchmark reporting: `mark_phase(name)` records a named phase
+boundary at the current frame/instant; `phase_stats(now, refresh_hz)`
+returns one `PhaseStats` (frames, wall duration, late count/percent,
+p50/p90/p99, worst) per marked phase, sliced from the existing ring by a
+new parallel `index_ring`; `late_at_hz(refresh_hz)` gives the whole run's
+late count/percent judged against an arbitrary refresh rate rather than
+the fixed 60Hz `JANK_THRESHOLD` every existing caller still uses (a
+separate method, not a parameter on `report()`, so nothing else changes
+behaviour). `RING_CAPACITY` grew 4096->16384 to hold a full multi-phase
+run without evicting earlier phases' samples.
+
+## 2026-09-06: `List::fling`, `VelocityTracker`, `FlingCalculator` (IRIS_TODO.md's "swiping has no momentum")
+
+`iris::widget::List` gained a real fling: `fling(velocity_px_per_s)` starts
+one (cancelled by the next touch-down via `cancel_fling`, or automatically
+once it settles or reaches loaded content's start/end), `is_scrolling()`
+reports whether one is running, and `tick_fling(now: Instant) -> bool`
+advances it and returns whether it is still going -- a caller that owns a
+`RequestRedraw` handle can hand it to the list once via the new
+`set_redraw_handle`, after which `List` re-arms its own next frame while
+flinging with no further polling needed; a caller driving a scripted
+benchmark instead calls `tick_fling` itself in a loop, same as it already
+drives `scroll`.
+
+The physics is `iris::sense::FlingCalculator` + `VelocityTracker`
+(`sense.rs`, beside `DragArbiter`): a port of AOSP `SplineOverScroller`'s
+deceleration curve (the same one Compose's own `ScrollableDefaults.
+flingBehavior()` uses), cited at the definition, so a fling here travels
+the same distance a Compose `LazyColumn` would for the same initial
+velocity. `VelocityTracker` estimates that velocity from the drag's last
+~100ms of samples rather than one frame's last delta. Unit-tested:
+velocity from known samples, fling distance/duration against the closed-
+form spline result (within 1%), cancel-on-touch, and the start/end clamp
+(a fling stops rather than scrolling into content that was never loaded).
+
+Before: a touch-drag panned exactly as far as the finger moved and stopped
+dead on release. After: releasing mid-drag continues scrolling and
+decelerates, matching the muscle memory every other Android scroll view
+already trained. `transcript_ui::selection::Selection::drag` wires this in
+-- a release only flings if the gesture had committed to panning
+(`DragArbiter::is_panning`, new), never a selection or an undecided tap.
+
+## 2026-09-06: `UiRenderNode::new` returns `Result`, not `Self` (RUST.md's P0 box, phone-crash fix)
+
+`iris_core::UiRenderNode::new(device, queue, config)` now returns
+`Result<Self, String>` instead of `Self`. Why: it used to let a bind-group-
+layout validation failure reach wgpu's default error handler, which panics
+with no way for a caller to intervene -- exactly what aborted the P0 bench
+APK on Iris's phone with the crash report truncated to "wgpu error:
+Validation Error" and nothing else recoverable. It now runs its creation
+calls inside wgpu error scopes and returns the full error text (wgpu's own
+"Caused by" chain) as `Err` instead.
+
+Both callers changed to match: `android::render::AndroidRenderer::new`
+itself now returns `Result<Self, String>` too, building a fuller report
+(adapter identity, the limits/downlevel flags a layout validates against,
+then wgpu's text) on failure -- its caller,
+`android::view::IrisViewPeer::surface_changed`, logs that report as one
+logcat line and shows it on screen (a new `IrisView.showRendererError`,
+called via an ordinary JNI method call rather than a new `native fn`)
+instead of letting the process abort. `default::render::UiRenderer::new`
+(the winit/desktop backend) still panics on failure -- there is no
+on-screen fallback there -- but the panic message is now the same full
+text rather than whatever wgpu's own handler would have printed.
+
+No change for an app that never constructs a `UiRenderNode` directly (every
+current one goes through `AndroidRenderer`/`UiRenderer`), but anyone who
+does needs an `?`/`.expect()`/`match` at the call site now. Full audit and
+the named hypothesis for what actually failed on the phone are in
+RUST.md's P0 box, "iris bench crash on the phone, 2026-09-06."
+
+## 2026-09-05: `AndroidAppState::platform_ready` (RUST.md's P0 box, iris half)
+
+Added a second, optional lifecycle method to `iris::android::AndroidAppState`
+(`iris/src/android/view.rs`), called once from `new_peer` right after `new`:
+
+```rust
+fn platform_ready(&mut self, rsc: &mut AndroidRsc<Self>, vm: JavaVM, view: GlobalRef) {}
+```
+
+Default does nothing, so every existing implementor (`Client`,
+`TranscriptClient`) is unaffected. It exists for a caller that needs to call
+into Java itself beyond what a `RequestRedraw` handle already covers --
+P0's bench build (`iris-android-app`'s new `bench` feature,
+`bench_client.rs`/`bench_jni.rs`) uses it to hold a `JavaVM` + `GlobalRef`
+to the view so its "Copy report" control and once-a-second battery sampler
+can call `BatteryManager`/`ClipboardManager` through the view's own
+`Context`, from a background tokio task as well as the UI thread. `new`
+itself was not extended with these two parameters: most implementors need
+nothing here, and `new`'s job is building the widget tree, not holding a
+platform handle. `vm`/`view` are independent handles from the ones
+`new_peer` keeps for its own `RequestRedraw` (a fresh `get_java_vm`/
+`new_global_ref` each), so storing them has no effect on that mechanism.
+
+## 2026-09-05 (later still): `iris_core::device_limits()`, and iris no longer requests compute-shader limits
+
+New public function, `iris_core::device_limits() -> wgpu::Limits`. Why:
+`adapter.request_device`'s `required_limits` was `Limits::default()` plus
+a `max_buffer_size` override in both platform backends, and
+`Limits::default()` requests desktop-tier compute-shader limits
+unconditionally (`max_compute_workgroups_per_dimension: 65535`) even
+though nothing in `iris`/`iris-core` uses a `ComputePipeline` — that
+crashed device creation outright on a downlevel GL adapter reporting
+OpenGL ES 3.0 (no compute shaders at all: the Android emulator's
+`EMU_GPU=software` path, and any real GLES-3.0-only Android device).
+`device_limits()` is what both `android::render::AndroidRenderer::new`
+and `default::render::UiRenderer::new` now build their `required_limits`
+from, so the request cannot drift between the two backends.
+
+Before: `Limits { max_buffer_size: 1 << 30, ..Default::default() }`
+inlined in each backend. After: `iris_core::device_limits()`, which is
+the same thing with the six `max_compute_*` fields additionally zeroed.
+A caller building its own `DeviceDescriptor` outside these two backends
+(there are none today, but a third platform backend would want this)
+should call `device_limits()` rather than reaching for
+`Limits::default()` directly, unless it genuinely adds a compute pass —
+in which case it wants the specific compute limits that pass needs, not
+the desktop-tier default for everything.
+
+## 2026-09-05 (later the same day): `iris_core::FrameReport` (RUST.md's I5 box)
+
+New public type, `iris_core::FrameReport` (re-exported from `iris_core`'s
+`render` module alongside `FrameStats` and `JANK_THRESHOLD`). Why: `dumpsys
+gfxinfo` cannot see a `SurfaceView`'s own GPU-drawn frames at all, so a
+`wgpu`-rendered iris screen had no way to ask "was this smooth" the way
+Compose's own in-app render report already can -- item 3 of RUST.md's
+recommendation was stuck on a one-sided number for exactly this reason.
+
+`FrameReport::record(elapsed: Duration)` is called once per frame (wired
+into `android/view.rs`'s `render()`, wrapping the same span from redraw
+start to after `queue.submit`+`present()` that Compose's report and
+`gfxinfo` both count) and writes into a fixed 4096-entry ring -- no
+allocation on the hot path. `FrameReport::report() -> Option<FrameStats>`
+gives total frames, janky % (over `JANK_THRESHOLD`, the same 16.7ms 60Hz
+budget `gfxinfo` uses), P50/P90/P99 and the worst; `None` if nothing has
+been recorded since the last `reset()`, not a zeroed report that would
+read as a real measurement. `FrameStats`'s `Display` line says plainly
+that it measures up to `present()` being called, not GPU/compositor
+completion, since wgpu's `present()` isn't fenced against either.
+
+`AndroidUiState` gained a `pub frame_report: FrameReport` field --
+anything with `HasAndroidUiState` can now read or reset it. Before this,
+there was no way to ask iris's own render path how long a frame took at
+all, on any backend.
+
+Before/after, for a caller that already has `ui_state: &AndroidUiState`:
+
+```rust
+// before: no such question could be asked
+// after:
+match ui_state.frame_report.report() {
+    Some(stats) => log::info!("iris frame report: {stats}"),
+    None => log::info!("iris frame report: no frames recorded yet"),
+}
+ui_state.frame_report.reset(); // via android_state_mut()
+```
+
+`iris-android-app`'s transcript screen exposes this as two named,
+tappable controls ("Frame report", "Reset frame report") rather than
+requiring a caller to wire its own UI -- see `transcript_client.rs`'s
+`frame_report_controls`.
+
+## 2026-09-05: `Tasks::redraw_handle` (RUST.md's I5 Android integration)
+
+New public method on `iris::task::Tasks`, `redraw_handle(&self) ->
+Arc<dyn RequestRedraw>`. Why: a caller running its own long-lived loop
+*inside* one spawned task (a live SSE follow, the Android transcript
+client's `select_session`) has no other way to ask for a frame after each
+`TaskCtx::update` -- `Tasks::spawn`'s own wrapper only requests one, after
+the whole async closure finishes, which fits a single request-then-update
+but not a stream that needs to be seen redrawing after *each* event. This
+is the same gap `iris/desktop-app`'s module doc names for why it uses
+winit's `Proxy<AppEvent>` instead of `Tasks` -- android-view has no
+`Proxy`, so this is what closes it there.
+
+**A real bug this uncovered, not a hypothetical**: calling the returned
+handle's `request_redraw()` from the background thread crashed the process
+(`SIGABRT`, `Result::unwrap() on an Err value: JavaException`) the first
+time an Android transcript fetch called it a second time. `android/render.rs`'s
+`AndroidRedrawHandle` was already attaching the calling thread to the JVM
+correctly, but its `request_redraw` called `View::post_frame_callback`,
+whose Java side calls `Choreographer.getInstance()` -- which throws unless
+the *calling* thread already has a `Looper`, and a tokio worker thread,
+even freshly JNI-attached, has none. Fixed by routing through
+`View::post_delayed(0)` instead (Android's own thread-safe "queue work onto
+this View's UI thread" primitive, needing no caller-side `Looper`), landing
+on a new `IrisViewPeer::delayed_callback` override that drains tasks and
+renders -- same body as `do_frame`, on the UI thread where
+`post_frame_callback` is safe again. Any future caller of `redraw_handle()`
+from a background thread gets this for free; nothing about the fix is
+specific to the transcript screen.
+
+## 2026-09-05: `transcript_ui::build_tree` (RUST.md's E4)
+
+`transcript_ui::build` claimed the whole window (`ui_state.set_root(tree)`)
+as its last step, which is right for a window that *is* the transcript
+screen (the winit example, an eventual Android cdylib) and wrong for the
+desktop app, which puts a session list beside it. `build_tree` is `build`
+minus that last step: it returns `(TranscriptScreen, StrongWidget)` instead
+of just `TranscriptScreen`, and the caller decides where the tree goes —
+into `ui_state.set_root`, or into a `WidgetPtr` alongside something else
+(`iris/desktop-app`'s `rebuild_transcript`). `build` is now one line calling
+`build_tree` and doing the `set_root` itself, so existing callers are
+unaffected.
+
+```rust
+// before, and still available, for a caller that wants to *be* the window:
+let screen = transcript_ui::build(rsc, &mut ui_state, rows);
+
+// new, for a caller embedding the screen beside something else:
+let (screen, tree) = transcript_ui::build_tree(rsc, rows);
+some_widget_ptr(rsc).set(tree);
+```
+
+
+## 2026-09-05: `DragArbiter`, pan-vs-select for one shared touch gesture (RUST.md's I5)
+
+New public type, `iris::sense::DragArbiter`. Why: a widget author who
+registers both a list-level pan and a row-level drag-to-select on the same
+touch gesture has no way to arbitrate between them — `core/src/sense.rs`'s
+`run_sensors` always gives the innermost layer first refusal, so the inner
+one wins every frame it is pressed, not just the frame the press started
+(this is exactly what left transcript-ui's touch-drag panning unreachable
+until now). `DragArbiter` is one small state machine, one instance per
+gesture surface (a whole list, not per row), that a caller drives with its
+own `press_start`/`update`/`release` calls and a caller-supplied `Instant`
+(so it is unit-testable without a real clock or a render harness). It
+decides the way Android itself does: an ordinary vertical drag pans
+immediately; a stationary press held `LONG_PRESS` (500ms) starts a
+selection, which any further drag then extends; a horizontal drag while
+something is already selected extends it immediately, skipping the wait.
+
+```rust
+// One per list, held alongside whatever state coordinates the rows:
+let mut arbiter = DragArbiter::new();
+
+// On press-down:
+arbiter.press_start(pos, Instant::now(), already_selected);
+// Every frame the button/finger stays down:
+match arbiter.update(pos, Instant::now()) {
+    DragOutcome::Pan(dy) => list.scroll(-dy),
+    DragOutcome::SelectStart => selection.begin(...),
+    DragOutcome::SelectExtend => selection.extend(...),
+    DragOutcome::Undecided => {}
+}
+// On release:
+arbiter.release();
+```
+
+`transcript-ui`'s `Selection::drag` (`transcript-ui/src/selection.rs`) is
+the reference caller: every row's `CursorSense::click_or_drag() |
+CursorSense::unclick()` handler routes through one `Selection`-owned
+arbiter instead of calling `begin`/`extend` directly, so a drag that starts
+on a row's own rendered text now pans the list correctly instead of
+always starting a selection. 8 new unit tests in `iris/src/sense.rs`'s
+`drag_arbiter_tests` module.
+
+### 2026-09-05, later: `DragArbiter::is_idle()`, recovering a missed `press_start`
+
+Follow-up to the above, from a real touch-scroll dropout: a gesture's
+`ACTION_DOWN` can land on a caller's own dead space (a row's padding, a
+gap, a header with no handler) that never calls `press_start`, so the
+first frame the arbiter actually sees is a `Pressing`-shaped `update`
+with no matching start. Before this, `update`'s `Idle` arm had no way to
+tell that apart from "nothing is happening" and answered `Undecided`
+forever for the rest of that gesture. `is_idle(&self) -> bool` lets a
+caller notice the gap and recover: if `is_idle()` is true on a frame the
+caller knows a press is genuinely down (its own `Pressing`/equivalent
+sense fired), call `press_start` right there instead of assuming one
+already happened. `transcript-ui`'s `Selection::drag` is the reference
+caller — one new match arm, checked before the ordinary `update`-only
+case. Any other `DragArbiter` caller with the same "one sensor per
+sub-region, no fallback for dead space" shape has the same gap and wants
+the same recovery.
+
+## 2026-09-05: `SpanStyle`, per-range text styling (RUST.md's I5)
+
+A `TextBuffer` used to have exactly one style (`TextAttrs`: colour, size,
+family, ...) for its whole string, applied via `push_default` into parley's
+ranged builder. `SpanStyle` is a second, optional layer: a byte range plus
+whichever of colour/family/font size/bold/italic/underline it overrides,
+pushed with parley's own `push(property, range)` instead. Why: a transcript
+row's markdown (a heading, **bold**, `inline code`, a link) all inside one
+wrapped paragraph needs each to carry its own look while the paragraph
+still wraps and selects as a single buffer — the thing `masonry`'s
+`TextArea` cannot do (`StyleSet` is one style for the whole editor,
+`text_area.rs:43-44`'s `// TODO: RichTextInput`), and the reason this
+existed at all.
+
+```rust
+let (text, spans) = transcript_ui::markdown::render_markdown(src, 16.0);
+wtext(text)
+    .spans(spans)   // new: TextBuilder::spans, on both Text and TextEdit
+    .editable(EditMode::MultiLine)
+    .add(rsc);
+```
+
+Two things a widget author should know before reaching for it:
+
+- **Call `.spans()` before or after `.editable()`, both work** — the field
+  lives on `TextBuilder` itself, not either output type, and both
+  `TextOutput::run` and `TextEditOutput::run` apply it to the buffer via
+  `TextBuffer::set_spans`. **These two call sites are a pair**: adding a
+  third `TextBuilderOutput` impl without also calling `set_spans` there
+  reproduces the exact bug this box shipped once already (spans silently
+  dropped for `TextEdit`, found only by screenshotting, not by any test —
+  `markdown.rs`'s own unit tests check string/range logic, which is
+  correct in isolation and proves nothing about whether the render path
+  ever sees it).
+- **Colour is now per-glyph, not per-buffer.** `PlacedGlyph` gained a
+  `color: UiColor` field (from parley's own per-run `Style::brush`), and
+  `Painter::glyphs` draws each glyph in its own colour instead of
+  `RenderedText::color` uniformly. `RenderedText::color` still exists (the
+  buffer's *base* colour, for a caller that wants it as a whole, e.g. to
+  tint a cursor) but no longer drives what a glyph actually renders as.
+
+## 2026-09-05: accessibility names via AccessKit (RUST.md's I4)
+
+`.label()` (already in `trait_fns.rs`, previously unused anywhere in-tree)
+is now load-bearing: it's the one thing that puts a widget in the AccessKit
+tree `iris_core::ui::access::AccessTree` builds and both backends push
+out. A widget author who wants a control to be findable by name (and
+tappable by name, through `ui-trace`/a real screen reader) calls `.label()`
+on it; nothing else is required, and a widget nobody labels is invisible
+to this system at zero cost, not just zero UI.
+
+```rust
+let button = rect(Color::LIME)
+    .on(CursorSense::click(), move |_, rsc| { ... })
+    .label("Add task");   // now findable by uiautomator/AccessKit as "Add task"
+```
+
+Two new things a widget author might touch directly:
+
+- **`Widget::access_role(&self) -> accesskit::Role`**, default `Unknown`.
+  Override it if your widget has a real platform equivalent —
+  `TextEdit` now returns `TextInput`/`MultilineTextInput` by `EditMode`.
+  Only consulted for a widget that also has a `.label()`; an unlabelled
+  widget's `access_role` is never called.
+- **`Widgets::named() -> impl Iterator<Item = WidgetId>`** — every widget
+  with an explicit label, for anything else that wants to walk the same
+  set `AccessTree` does.
+
+Nothing about `Painter`, `draw`, or the layout/move machinery changed —
+this sits entirely beside them, reading `resolved_region`'s output rather
+than participating in producing it.
+
+## 2026-09-05: `List`, a virtualised bottom-anchored list (RUST.md's I3)
+
+A new widget, `iris::widget::List` (`iris/src/widget/list.rs` -- read its
+module doc first), for the transcript's kind of screen: variable-height
+rows, keyed by a `u64`, composed only while visible, moved rather than
+re-laid-out on scroll, a scroll anchor that survives a row inserted above
+it, "more" sentinels at each end, and "hold the edge nearest the tap" when
+a row's height changes (`note_tap`, resolved in the layout pass).
+
+```rust
+let mut list = List::new(Axis::Y);
+list.push_back(ListRow::new(key, row_widget));   // O(1)
+list.push_front(ListRow::new(older_key, row));   // O(1), anchor unaffected
+list.set_more_before(Some(spinner_widget));      // sentinel, drawn at the edge
+list.note_tap(viewport_y);                       // before mutating a row's height
+let (top, bottom) = list.extent(key).unwrap();   // last frame's on-screen box, if visible
+```
+
+Built entirely out of existing primitives (`Painter::widget`/`widget_within`/
+`reposition`/`draw_twice`, and `draw_inner`'s own old-children diffing) --
+no new mechanism was added to the render core for it. One correctness
+lesson worth reading even for other widgets: a row that fills whatever
+region it is offered (`Rect`, `is_size_independent`) cannot be measured at
+a throwaway oversized region and then merely `reposition`ed into place --
+`reposition` only ever writes an offset, never a size, so the oversized
+primitive stays oversized. `List` fixes this by caching each row's real
+height once measured and placing an already-known row directly at its
+exact box; see `list.rs`'s `place` for the full reasoning and
+`a_fill_shaped_background_is_not_left_oversized` for the regression test.
+
+## 2026-09-05: a second backend (android-view), and what moved to make room for it
+
+RUST.md's I2. Three changes a widget or app author would notice, all in
+service of the same thing: `default` (winit) and the new `android`
+(android-view) backends sharing what does not depend on windowing.
+
+- **`Selector`/`Selectable`'s bound changed from `Rsc::State:
+  HasDefaultUiState` to `Rsc::State: FocusHost`** (new trait, `attr.rs`).
+  `HasDefaultUiState` still exists and still works — `default/attr.rs` now
+  implements `FocusHost` for anything that has it — so a winit app's
+  existing code is unaffected. An Android app implements `FocusHost` via
+  `HasAndroidUiState` instead. Affects only an app that referenced
+  `HasDefaultUiState` directly at a `Selectable`/`Selector` call site
+  rather than through `.attr::<Selectable>(())`, which nothing in-tree
+  does.
+- **`Tasks::init` takes `Arc<dyn RequestRedraw>` instead of
+  `Arc<winit::window::Window>`.** `RequestRedraw` (`task.rs`) is one method,
+  `fn request_redraw(&self)`; `winit::window::Window` implements it
+  (`default/render.rs`), so `Tasks::init(window)` at a call site is
+  unchanged by inference. Only matters if something constructed a `Tasks`
+  directly rather than through `DefaultRsc`/`AndroidRsc`.
+- **`TextEdit::apply_event`/`TextInputResult` are `#[cfg(not(target_os =
+  "android"))]`** — they take a `winit::event::KeyEvent`, which does not
+  exist on Android; `android/input.rs` drives the same primitives
+  (`backspace`/`delete`/`motion`/`insert`, all still unconditional) from
+  `ndk::event::Keycode` directly instead. New unconditional getters on the
+  way: `TextEdit::text()`/`selection_range()`/`caret()`, and
+  `TextEditCtx::delete_byte_range`/`set_cursor_byte` — the primitives
+  `android/ime.rs`'s `InputConnection` bridge needed and that were not
+  previously exposed publicly.
+
+## 2026-09-04: `Widget::draw` reports the size it used; `desired_width`/`desired_height` are gone
+
+A widget used to implement three methods (`draw`, `desired_width`,
+`desired_height`); it now implements one, `fn draw(&mut self, painter: &mut
+Painter) -> Size`, which draws into `painter.region()` and returns how much
+of it was used. Why: the two extra methods routinely re-simulated what
+`draw` was about to do anyway (`Span::desired_ortho` copied its own draw
+loop to get cross-axis sizing right) — one visit per widget per frame
+instead of up to three. A container that needs a child's size before
+placing it (alignment, centering) draws the child once at a provisional
+region, reads the returned `Size`, and calls the new `Painter::reposition`
+to move it into its final spot — an O(1) offset write, not a second draw. A
+widget whose drawn output never depends on the size it's given (a
+fixed-size `Rect`, a decoded `Image`) overrides the new `fn
+is_size_independent(&self) -> bool { false }` to `true`, which skips
+redrawing it when only its offered region changes shape.
+
+```rust
+// before
+fn draw(&mut self, painter: &mut Painter) { /* ... */ }
+fn desired_width(&mut self, ctx: &mut SizeCtx) -> Len { /* ... */ }
+fn desired_height(&mut self, ctx: &mut SizeCtx) -> Len { /* ... */ }
+
+// after
+fn draw(&mut self, painter: &mut Painter) -> Size { /* ... */ }
+```
+
+`SizeCtx` and `Cache` are gone with it — see `LAYOUT.md` for the full
+design, the move-offset mechanism this shipped alongside, and the file
+list.
+
+## 2026-09-04: texture pipeline rebuilt off the binding array
+
+`Textures`/`TextureHandle`, `GlyphPrimitive`, and `UiRenderNode::new` all
+changed shape. Why: the old pipeline bound every texture ever drawn in one
+`binding_array<texture_2d<f32>>` and asked every device, unconditionally,
+for `VK_EXT_descriptor_indexing` — a real share of Android GPUs lack it,
+and it failed outright on the Android emulator's software Vulkan. See
+TEXTURES.md's "Recommended shape" and "Implemented, 2026-09-04".
+
+- **`UiRenderNode::new` drops its `limits: UiLimits` parameter, and
+  `UiLimits` is gone.** Before: `UiRenderNode::new(&device, &queue,
+  &config, UiLimits::default())`. After: `UiRenderNode::new(&device,
+  &queue, &config)`. Nothing replaces it — there are no more
+  binding-array limits to size.
+- **`src/default/render.rs`'s device request asks for no features and no
+  binding-array limits.** Before: `required_features:
+  Features::TEXTURE_BINDING_ARRAY | Features::PARTIALLY_BOUND_BINDING_ARRAY
+  | Features::SAMPLED_TEXTURE_AND_STORAGE_BUFFER_ARRAY_NON_UNIFORM_INDEXING`
+  plus two `max_binding_array_*` limits. After: `Features::empty()` (the
+  `DeviceDescriptor` default) and only `max_buffer_size` set, which was
+  never about the binding array.
+- **`TextureHandle` has no `primitive()` method any more**; a caller
+  outside `iris` shouldn't have been calling it (it fed the old renderer's
+  internals), but if something did: use `image_index()` for a standalone
+  image's bind-group index. There is no equivalent for a page — a page has
+  no bind group of its own now, see below.
+- **`GlyphPrimitive` has no public constructor from a struct literal.**
+  Before: `GlyphPrimitive { uv_min, uv_max, view_idx, sampler_idx, color,
+  flags }`. After: `GlyphPrimitive::new(uv_min, uv_max, layer, color,
+  flags)` — one `layer` (the shared atlas array's layer) instead of a
+  `view_idx`/`sampler_idx` pair, since a page is now a layer of one array
+  texture rather than its own bound texture.
+- **A widget author drawing images is unaffected**: `Painter::texture`/
+  `texture_at`/`texture_within` and `Textures::add` keep their signatures.
+  What changed underneath is that each standalone image now gets its own
+  `wgpu::BindGroup` and draw call instead of a slot in the shared array —
+  invisible from the widget API, visible only in `UiRenderNode`'s internals
+  and in `iris`'s device requirements.
+
+## 2026-09-05: `FrameReport` splits each frame at `queue.submit`
+
+`FrameStats` gains two fields, and `FrameReport` gains a second recording
+method, to answer "is a slow frame iris's own CPU work or the driver/GPU"
+with a number instead of a guess (RUST.md's I5 box).
+
+- **`FrameReport::record_split(total, submit_to_present)`** is a second way
+  to record a frame, alongside the existing `record(total)` (unchanged,
+  and still what a caller with no split should use — it now reads as
+  `cpu_p50 == total`, `gpu_wait_p50 == 0`, rather than fabricating a
+  number for a half it never measured).
+- **`FrameStats` gains `cpu_p50` and `gpu_wait_p50`**: medians of
+  redraw-start-to-submit and submit-to-after-`present()` respectively,
+  independent of each other and of the existing `p50`/`p90`/`p99`/`worst`
+  (which are unchanged, and still over the whole frame). The Android
+  renderer's `draw()` now returns the `submit_to_present` `Duration` it
+  measured, which `android::view::render()` passes to `record_split`.
+- **Caveat carried in both doc comments**: `submit_to_present` is not
+  fenced against the GPU actually finishing — it is "how long the CPU was
+  blocked handing the frame to the driver," not a confirmed GPU-completion
+  time. Enough to separate "iris is slow building the frame" from "iris is
+  slow handing it off," not enough to claim an exact GPU budget.
+
+## 2026-09-05: `List::replace_back`/`List::clear`, and `TranscriptScreen::apply`
+
+Fixes the "every client refolds and rebuilds the whole widget tree per
+streamed event" cost RUST.md's P0 box measured (20 events/second against a
+~3,200-row transcript). Two small additions to `iris::widget::List`
+(`iris/src/widget/list.rs`), plus one new method on `transcript-ui`'s
+`TranscriptScreen`.
+
+- **`List::replace_back(row: ListRow) -> Option<ListRow>`**: swaps the
+  *last* row's widget for a new one without moving it — same slot index,
+  so an anchor already pinned there (in particular a list flush with its
+  own end) stays pinned, and a `List` scrolled elsewhere is untouched.
+  `None` if the list is empty. `RowKey` may differ between the old and new
+  row; only `heights`/`extents` care, and both are invalidated for the
+  evicted key the same way `pop_back` already does.
+- **`List::clear()`**: drops every loaded row and resets to `List::new`'s
+  state (`more_before`/`more_after` untouched — a caller that wants those
+  cleared too calls `set_more_before(None)`/`set_more_after(None)` itself).
+  The fallback path for a change that touches more than the tail.
+- **`transcript_ui::TranscriptScreen::apply(&self, rsc, old: &[TranscriptItem], new: &[TranscriptItem])`**:
+  the incremental alternative to rebuilding the whole screen from
+  `transcript_ui::build_tree` on every folded event. Diffs the two
+  `group_tool_runs` outputs and picks the cheapest update: nothing changed
+  (no-op), a pure append (`push_row`, unchanged cost), or — the common
+  streaming case, a delta into a still-open assistant message — a rebuild
+  of just the one changed row via `List::replace_back`, with any further
+  new rows appended after it. A row changing *before* the tail (only
+  `group_tool_runs` retroactively grouping tool calls into a run does
+  this) falls back to `List::clear` plus a full rebuild, counted in
+  `TranscriptScreen::take_rebuilds()`. `bench_client.rs`, `transcript_client.rs`
+  and `desktop-app/app.rs` all call this now instead of rebuilding on every
+  event; only the opening page (and `apply`'s own fallback) still calls
+  `build_tree`.
+- **`TextEditCtx::set_with_spans(text, spans)`**: `set()` plus a fresh
+  `Vec<SpanStyle>` in one call, needed because a streamed row's markdown
+  re-renders to both a new string and a new span list on every delta and
+  the two have to land together — a stale span list drawn against new
+  text can point past its end. `set()` itself is unchanged (still clears
+  spans to none, as before).
+
+Measured on this checkout's emulator (`iris/android-app/run-bench.sh`,
+release, x86_64, `force-gles`): worst-frame and p99 during the streaming
+phase dropped from 369.3ms/284.5ms (full rebuild per event, prior pass) to
+~101–130ms/~76–103ms across three runs (this fix) — see RUST.md's P0 box
+for the full numbers and the comparison's caveats (different AVD
+instances, not a controlled A/B on identical hardware state).
+
+## 2026-09-06: bundled fonts, `content_scale`, `AndroidAppState::on_insets_changed`
+
+From RUST.md's P0 box, working Iris's first real-phone report (font/scale/
+inset bugs the emulator never showed).
+
+- **`TextData` now bundles Noto Sans + Noto Sans Mono** (regular/bold/
+  italic/bold-italic static faces, OFL) and registers them ahead of the
+  platform's own fonts in the `SansSerif`/`Monospace` generic-family
+  lists, rather than relying on the platform's font enumeration alone.
+  `TextData::font_diagnostics() -> FontDiagnostics` reports what was found
+  and what each style axis resolved to — logged once at startup and shown
+  on a screen's Diagnostics page if it has one. Adds ~3.6 MB uncompressed
+  to any binary linking `iris-core`; `build-apk.sh`'s own output says the
+  delivered (compressed) number.
+- **`UiRenderNode::new`/`resize` now take the window size explicitly**
+  (`window_size: impl Into<Vec2>`) instead of deriving it from the
+  surface's physical `SurfaceConfiguration`. Existing callers pass a
+  *logical* size (physical ÷ density/scale-factor) now; this is what makes
+  a `font_size: 16.0` 16 dp instead of 16 raw device pixels on a
+  high-density phone. Before this, `scale_factor` did not exist anywhere
+  in the crate, on either platform.
+- **`AndroidUiState::content_scale: f32`** (`DisplayMetrics.density`, read
+  once in `new_peer`) and the desktop equivalent (`window.scale_factor()`)
+  now divide every physical-pixel number before it reaches layout or
+  touch handling — see `content_scale`'s own field doc for the full list
+  of what depends on it.
+- **New: `AndroidAppState::on_insets_changed(&mut self, rsc, LogicalInsets)`**,
+  a default-no-op hook called from `render()` exactly when
+  `AndroidUiState::insets()` changes. Nothing previously consumed
+  `insets().top` at all; a screen with chrome under the status bar
+  implements this to pad it, in the same logical units `content_scale`
+  converts everything else to.
+- **New: `iris_core::WgpuErrorLog`**, installed via `Device::
+  on_uncaptured_error` on the Android device (wgpu's default handler is an
+  unconditional panic outside `UiRenderNode::new`'s own error scopes).
+  Explicit `Arc`-backed value passed to the callback and kept on
+  `AndroidRenderer`, not a global — a caller wanting one on desktop builds
+  its own the same way.
+
+## 2026-09-06: `Len::dp`, physical pixels throughout, the keyboard glyph wipe
+
+Iris's phone report on build a9232ac (screenshots): text now the right
+size but blurry; the keyboard still wipes every glyph; the header buttons
+have nothing behind them. All three are fixed; this entry is the public
+API side. docs/LAYOUT.md has the layout-side writeup, docs/RUST.md's P0
+box has the full investigation and the phone verification still to do.
+
+- **The keyboard wipe was `surface_changed` rebuilding the whole renderer
+  on every resize**, including an IME-driven one — a fresh, empty glyph
+  atlas while the CPU-side glyph cache kept UV coordinates from the old
+  one. `surface_changed` now calls `AndroidRenderer::resize` (reconfigures
+  the surface and window uniform only) when a renderer is already live,
+  and only builds a new one when there genuinely isn't one yet.
+- **`Len` has a third field, `dp`** (Android's dp / CSS's reference pixel,
+  1/160in), beside the existing `abs` (now explicitly *physical* pixels)
+  and `rel`/`rest`. `len_fns::dp`/`Len::dp` construct one, used exactly
+  like `abs`/`rel`/`rest` — `dp(16)` instead of a bare `16` wherever a
+  size should look the same physical size on any density. This is the
+  unit IRIS_TODO.md's "density-independent length unit" item asked for;
+  it replaces the previous stopgap (the whole rendered scene divided by
+  `content_scale` then implicitly stretched back up), which is also what
+  made text blurry — a glyph rasterised at the small, pre-stretch size and
+  then upscaled onto the real framebuffer.
+- **`UiRenderState`/`Painter` gained `density()`/`set_density()`** (physical
+  pixels per dp). Every place a length resolves (`Len::apply_rest`,
+  `Size::to_uivec2`) now takes it; `Span::gap` and `Padding`'s four sides
+  moved from a bare `f32` to `Len` so they take `dp(...)` too. A bare
+  number anywhere is unaffected — still `abs`, physical pixels.
+- **Text is rasterised at physical resolution now.** `TextBuffer::shape`
+  takes `density` and multiplies `font_size`/`line_height` (and any span
+  override) by it before handing them to parley, so the atlas holds a
+  bitmap at the size it is actually shown at rather than a low-resolution
+  one stretched afterward.
+- **Everything at the Android boundary is physical pixels now** — window
+  size, touch coordinates, insets (`LogicalInsets` renamed
+  `WindowInsets`). The previous "logical" division by `content_scale` is
+  gone; `content_scale` now feeds `set_density` instead.
+- Not yet verified on Iris's actual phone (this pass had no device) —
+  built and checked on this checkout's emulator only. RUST.md's P0 box
+  says what she should check for: crisp text at two densities, the
+  keyboard no longer wiping, and the header's background.

docs/IRIS_TODO.md

@@ -7,6 +7,29 @@ order and what "done" looks like. Tick and date them in place.
 
 ## Fix
 
+- [x] **`request_device` asked for compute-shader limits it never uses
+  (2026-09-05).** `Limits::default()` (both `iris/src/android/render.rs`
+  and `iris/src/default/render.rs`) requests desktop-tier compute limits
+  unconditionally, even though nothing in `iris`/`iris-core` creates a
+  `ComputePipeline` or writes a `@compute` shader stage — confirmed by
+  grepping the whole tree, not assumed. That crashed device creation
+  outright on the Android emulator's software GL path (`EMU_GPU=software`,
+  `--features force-gles`): SwiftShader's GL reports itself as OpenGL ES
+  3.0, which has no compute shaders, so the adapter's real limit is 0
+  against the unconditional request for 65535 — the same would happen on
+  any real GLES-3.0-only Android device. Fixed by a new, shared
+  `iris_core::device_limits()` (`iris/core/src/render/mod.rs`) that zeros
+  exactly the six `max_compute_*` fields rather than switching to a
+  downlevel `Limits` preset — `downlevel_webgl2_defaults()` also zeros
+  `max_storage_buffers_per_shader_stage`, which `shader.wgsl`'s vertex
+  stage needs (four `var<storage>` buffers), so that preset would trade
+  this crash for a bind-group-layout one on the same hardware.
+  `rigs/gpu-probe`'s own hand-mirrored `Limits` (it is deliberately its
+  own crate, not able to call `device_limits()` directly) was updated to
+  match. See `DECISIONS.md` and RUST.md's I5 box for the account,
+  including what could not be re-verified on-device this pass (the
+  emulator was in concurrent use by another session).
+
 - [x] **Input does not fall through by input type (2026-09-04).**
   `SensorUi::run_sensors` (`src/default/sense.rs`) used to set "consumed,
   stop checking lower layers" from mere hover — a widget registered for
@@ -82,6 +105,51 @@ order and what "done" looks like. Tick and date them in place.
   were exactly the same root cause measured two different ways. Frame 2
   now reports 0 (see the numbers above); not a separate fix.
 
+- [ ] **A read-only text display has no widget of its own — P0's bench
+  report area is a `TextEdit` standing in for one (2026-09-05).** The only
+  way to get selectable text on screen today is `.editable(...)` plus
+  `.attr::<Selectable>(())` (`Selectable` is only implemented for
+  `TextEdit`, `iris/src/attr.rs`), which also makes the field focusable —
+  tapping the bench report opens the soft keyboard over text nothing lets
+  you type into. Harmless for a bench-only debug screen (not fixed this
+  pass), but a real "selectable, not editable" text primitive would
+  remove the keyboard side effect and is worth having before another
+  screen wants the same thing (P1's own transcript rows already read
+  their content from a `TextEdit` for the same reason).
+
+## From the phone, 2026-09-06
+
+Found on Iris's own phone while working RUST.md's P0 box's phone-report
+follow-ups. Recorded here rather than fixed in that pass, so a follow-up
+agent takes them without colliding with that pass's `bench_client.rs`/
+`android/view.rs`/`android/sense.rs` changes.
+
+- [x] **Swiping has no momentum, fixed 2026-09-06.** `List::fling`/
+  `VelocityTracker`/`FlingCalculator` (`iris/src/widget/list.rs`,
+  `iris/src/sense.rs`) -- IRIS.md's 2026-09-06 entry has the full account.
+  Wired through `Selection::drag`'s release path, cancelled by the next
+  touch-down, clamped at the loaded content's start/end. Verified by unit
+  test (fling distance against the closed-form spline result, cancel-on-
+  touch, the clamp), not yet by an on-device or emulator feel-check --
+  that is still open.
+- [x] **Scrolling down sometimes jitters the text, fixed 2026-09-06.**
+  Root-caused by reading `DragArbiter::update`'s `Undecided`-to-`Panning`
+  transition rather than by an on-device trace (no emulator was used this
+  pass): it was the first named suspect, not the second. `self.last` stays
+  at the press origin for every `Undecided` frame (nothing pans while the
+  gesture might still be a selection), so the frame that finally crosses
+  `DRAG_SLOP` returned `Pan(dy)` with `dy` measured from `press_start` --
+  the *whole* pre-threshold drag, applied to the list in one step, however
+  many frames it had taken to get there. Fixed by applying only the
+  excess past `DRAG_SLOP` on that one frame (`dy - DRAG_SLOP.copysign
+  (dy)`), the same "consume the slop, don't replay it" rule Android's own
+  touch handling follows. New regression test,
+  `crossing_the_slop_by_a_little_pans_by_a_little` (`iris/src/sense.rs`).
+  **Not yet done**: an emulator trace of the real per-frame offset
+  confirming this was the whole story on real touch input rather than
+  only the arbiter's own unit tests -- worth a follow-up pass before
+  calling it fully closed.
+
 ## Build
 
 - [x] **Benchmarks**, not unit tests, run on demand (2026-09-05; a
@@ -176,14 +244,62 @@ order and what "done" looks like. Tick and date them in place.
   silently dropped. See RUST.md's I5 box for the full account of what
   *was* built (the screen, `SpanStyle`, cross-row selection, the growing
   composer).**
-  - [ ] **Android integration for this screen does not exist yet.** No
-    cdylib/Gradle shell the way `iris-android-app` wraps `tabs-ui` (I2),
-    so `transcript-bench.sh`'s render-number pass condition against the
-    Compose baseline cannot be run. Needs: real `client-core::ApiClient`/
-    `event_stream::follow_session_events` wiring against
-    `app/ui-sandbox.sh --delay` (this crate deliberately fetches nothing
-    itself, `transcript-ui/src/lib.rs`'s doc), a new cdylib + Gradle
-    module, then the bench script pointed at it.
+  - [x] **Android integration for this screen — done, 2026-09-05.**
+    `iris-android-app`'s `transcript-screen` Cargo feature
+    (`transcript_client.rs`) runs this screen against a real `ai-server`
+    through `client-core`, confirmed on-device: real scrolling, real
+    touch-drag panning, tap-by-name on the composer. Two real bugs found
+    and fixed along the way (a missing `INTERNET` permission; a
+    background-thread redraw request that crashed via a `Looper`
+    requirement, fixed by routing through `View::post_delayed` — see
+    `IRIS.md`'s `Tasks::redraw_handle` entry). See RUST.md's I5 box,
+    "The Android integration, done 2026-09-05" for the full account.
+  - [x] **A render-time number for iris, comparable to Compose's
+    `transcript-bench.sh` report — instrumentation done and a real number
+    obtained, 2026-09-05 (later the same day); the clean comparable loop
+    is not.** `iris_core::FrameReport` (`iris/core/src/render/
+    frame_report.rs`, `IRIS.md`'s new entry) times every frame from
+    `render()`'s redraw start to after `queue.submit`+`present()`, exposed
+    as two named on-screen controls ("Frame report", "Reset frame
+    report"). Driven against a real on-device touch-drag it read
+    `frames=34 janky%=61.76 p50=26.5ms p90=48.0ms p99=98.1ms
+    worst=98.1ms` — real, not inferred, but accumulated across several
+    gestures rather than one clean 24-swipe loop, because of the new
+    finding below. See RUST.md's I5 box, "Update, 2026-09-05, later the
+    same day" for the full account.
+  - [ ] **New, 2026-09-05: intermittent touch delivery to iris's
+    `SurfaceView` under this checkout's `EMU_GPU=software` emulator.**
+    The same swipe coordinates, confirmed (by scanning a screenshot
+    column for the first non-black pixel) to sit over real row text,
+    sometimes produced 30+ real frames and a screenshot diff and
+    sometimes produced zero of either, across otherwise-identical
+    `ui-trace` invocations. Not the already-understood "already at that
+    scroll edge" case (reproduced with content confirmed taller than the
+    viewport, in both directions). Leading candidate, not yet confirmed:
+    this checkout's emulator was independently observed at ~78% of one
+    CPU core, continuously, while idle on-screen — SwiftShader's software
+    rasterisation is CPU-bound by design, and a synthetic touch competing
+    with that load for delivery is plausible but unmeasured *during* a
+    failing gesture (the standing rule against diagnosing from
+    after-the-fact measurements applies here). Needs a sampler (load,
+    `dumpsys input`, a `-i 0` `ui-trace` capture) running while a failing
+    gesture is driven, and ideally a comparison under `-gpu host` (real
+    Vulkan) to see whether it is specific to software rendering. This is
+    what blocks the clean, comparable 24-swipe loop above.
+  - [x] **Long-press-then-drag-to-select — confirmed on-device, 2026-09-05
+    (later the same day).** `ui-trace` gained a `holddrag X1 Y1 X2 Y2
+    HOLD_MS MOVE_MS` action (`emulator-tools`, additive, extends the same
+    `MotionEvent`/`injectInputEvent` mechanism `swipe` already used):
+    press, hold past `LONG_PRESS`, move, release, as one continuous touch.
+    Driven against a real row (`holddrag 300 1850 300 2050 600 300`) it
+    produced `iris selection: begin at row ...` then a sequence of
+    `iris selection: extend to row ...` log lines
+    (`transcript-ui/src/selection.rs`, a new small `log` dependency since
+    selection has no accessibility label of its own yet — see the next
+    item), and a screenshot taken right after shows the expected
+    highlighted selection spanning multiple rows. `DragArbiter`'s own
+    unit tests already covered this sequence against a synthetic clock;
+    this is the first time it has been driven by a real device touch.
   - [x] **Touch-drag panning over a row's own rendered text — done,
     2026-09-05.** `row.rs` used to register `CursorSense::click_or_drag()`
     on each row's `TextEdit` for cross-row selection; `TextEdit::draw`'s
@@ -203,6 +319,20 @@ order and what "done" looks like. Tick and date them in place.
     --workspace` and `cargo ndk` (both `iris` and `transcript-ui`) all
     clean; `run-headless.sh` screenshot byte-identical to before the
     change (38578 bytes). See RUST.md's I5 box, "Gap closed, 2026-09-05".
+  - [x] **Intermittent touch-scroll dropout — root-caused and fixed,
+    2026-09-05.** Not the coalesced-`ACTION_MOVE` hypothesis the earlier
+    pass suspected (ruled out): a gesture's `ACTION_DOWN` can land on a
+    row's own padding/gap or its header, which no `CursorSense` covers,
+    so `DragArbiter` never gets `press_start` and sits in `Idle`
+    (answers `Undecided` forever) for that whole gesture. Fixed via a new
+    `DragArbiter::is_idle()` that `Selection::drag`
+    (`transcript-ui/src/selection.rs`) checks to recover a missed press
+    on the next `Pressing` frame. Four new unit tests. See RUST.md's I5
+    box, "Touch-scroll dropout root-caused, 2026-09-05", for the trace and
+    what a peer session sharing this checkout's emulator mid-pass
+    prevented from being re-verified end-to-end (the aggregate
+    `iris-scroll.sh` three-run confirmation and a re-taken FrameReport
+    row) — a future pass should finish that once the emulator is free.
   - [ ] **Row-level accessibility names.** The composer carries
     `.label("Message")`; transcript rows do not carry a `.label()` of
     their own yet, so `Widgets::named()` (I4) does not include them —
@@ -244,6 +374,42 @@ order and what "done" looks like. Tick and date them in place.
   everything, the same way input is**. Whatever the mechanism, a widget
   that does not animate must pay nothing and import nothing for it.
 
+## Build (for the port)
+
+Widgets `RUST.md`'s "The port, in order (decided 2026-09-05)" needs and
+iris does not have yet, one entry per gap, named against the P-step that
+first needs it. Move an entry up to "Fix" or tick it in place once built;
+do not duplicate it there.
+
+- [ ] **A history-paging cushion measured in on-screen viewports, not a
+  row count.** (**P1**.) `iris::widget::List` has no equivalent of the
+  Compose app's `HISTORY_SCREENS` — AGENTS.md's "Things that have
+  bitten" is explicit that a fixed row count under-fills a screen on a
+  tool-heavy transcript and over-fills one on a text-heavy one, so
+  whatever loads the next page has to ask the list how many viewports
+  are actually on screen, not assume a constant.
+- [ ] **A scaled thumbnail/image widget for an in-transcript image.**
+  (**P1**.) `SessionImage.kt`'s bitmap decode-and-downscale has no iris
+  counterpart; iris's own image widget (used by `bench_images.rs`) draws
+  a loaded texture but does nothing about sourcing or scaling one from a
+  server-produced attachment.
+- [ ] **A modal/dialog primitive.** (**P1**, reused by **P3** and
+  **P5**.) Needed for the session settings dialog, `UsageDialog`'s
+  equivalent, and the delete-with-`deleteForeign` confirmation with its
+  toggle switch. Build once, wherever it is first needed, rather than
+  once per screen that wants one.
+- [ ] **A horizontal gauge/bar widget.** (**P1**.) For
+  `SessionUsageBar`'s equivalent — a bounded fill reflecting a fraction,
+  nothing fancier.
+- [ ] **A `BusyItem` equivalent: a dimmed row carrying an operation
+  label that does not block its list's own scroll/drag.** (**P3**.) The
+  Compose version tried an overlay first and it swallowed the drag along
+  with the tap (AGENTS.md's "Shared appearance") — worth not repeating
+  that attempt in iris before building the row-level version directly.
+- [ ] **A toggle switch.** (**P3**.) For the delete dialog's
+  `deleteForeign` control; iris has no switch/checkbox widget yet as far
+  as this pass found.
+
 ## Reconsider
 
 - [ ] **`WidgetView`.** Iris is unsure of it: what she wants is an easy way
@@ -252,3 +418,35 @@ order and what "done" looks like. Tick and date them in place.
   redundant. Decide after the layout change lands, by writing a button
   both ways and keeping the one that is shorter to explain; delete the
   other rather than keeping two ways.
+
+## Build (asked for by Iris, 2026-09-06): a density-independent length unit
+
+- [x] **A third length kind beside relative and pixels, so display scales
+  "just work".** Done 2026-09-06 — `Len::dp`/`len_fns::dp`, resolved
+  against `UiRenderState`/`Painter::density()` at `apply_rest` time; text
+  additionally rasterises at the resolved (physical) size instead of
+  scaling a low-resolution bitmap afterward, which was making text blurry.
+  `Span::gap`/`Padding` moved from `f32` to `Len` so they take `dp(...)`
+  too; transcript-ui's row/composer padding and one example migrated.
+  `em` was not added — nothing in this pass needed a text-relative unit,
+  and `dp`'s own doc says why it and physical pixels are kept as separate
+  fields rather than one the caller pre-multiplies. Not yet verified on
+  Iris's own phone at two densities (this pass had no device) — see
+  docs/RUST.md's P0 box and docs/IRIS.md's 2026-09-06 entry for what to
+  check. Iris's words: "another length type similar to absolute &
+  relative, so instead there would be relative, pixels, and another unit
+  like em or whatever is standard. That way different display scales
+  should just work." Today a length is either a fraction of the parent
+  (`rest`/relative) or physical pixels, and the phone drew 16 px text at
+  roughly a third of its intended size until the P0 fixes applied the
+  display's scale factor globally. That global scale is a stopgap for the
+  benchmark; the real shape is a unit resolved against the display's
+  density at layout time — Android's `dp` / CSS's reference pixel is the
+  standard (1 unit = 1/160 in), with `em` as the text-relative option —
+  so a widget author writes `16.dp()` once and never sees the scale.
+  Done when: `Length` (or whatever the enum is called) has the third
+  variant; every place that resolves a length takes the density; the
+  examples and `transcript-ui` use the new unit for text sizes, padding
+  and control sizes; the emulator at two densities and the phone draw the
+  same layout at the same physical size. After the bench setup is
+  finished, before P1 draws any new screen.

docs/LAYOUT.md

@@ -861,6 +861,58 @@ unspecified rather than getting them wrong:
   conditions, so the remaining slack was accepted rather than chased
   further.
 
+## Density: `Len::dp`, resolved at `apply_rest` time (2026-09-06)
+
+Iris asked for a third length kind beside `abs` (physical pixels) and
+`rel`/`rest` (a fraction of the parent) — IRIS_TODO.md's "density-
+independent length unit" — after the P0 phone pass found 16px text
+drawing at roughly a third size on a real phone. The fix that shipped
+first (RUST.md's P0 box) was a global stopgap: divide the whole window
+into a "logical" coordinate space (physical ÷ `content_scale`) and let
+the shader's NDC mapping stretch it back up onto the real framebuffer.
+That fixed the *size* but not the *sharpness* — a glyph rasterised at the
+small, pre-stretch size and then stretched onto more physical pixels than
+it has texels for is blurry, which is exactly what Iris's next report
+said.
+
+**The fix**: `Len` gained a `dp` field, resolved against a `density: f32`
+(physical pixels per dp) at the one place a `Len` becomes a `UiScalar`
+(`Len::apply_rest`) — `abs + dp * density`. `density` lives on
+`UiRenderState` (`set_density`/`density()`) and `Painter` (`density()`),
+set once from `DisplayMetrics.density` in `android::view::new_peer`; the
+desktop backend has no per-monitor density wired up yet and stays at
+`1.0`. Every layout call site that used to call `.apply_rest()`/
+`.to_uivec2()` now passes `painter.density()` (nine call sites — `Span`,
+`Sized`, `MaxSize`, `Aligned`, `Scroll`, `List::place`, and
+`UiRenderState::reposition` itself). This also meant the Android
+boundary's global logical-space stopgap could come out entirely: window
+size, touch coordinates and insets are physical pixels again, matching
+`AndroidRenderer`'s own swapchain resolution, with `dp` doing the
+per-length work the global divide used to do for everything at once.
+
+**Text is the case that needed more than the `Len` plumbing.** A widget's
+`font_size`/`line_height` are plain `f32`, not routed through `Len` at
+all (there is no sensible `rel`/`rest` for a font size). `TextBuffer::
+shape` now takes `density` directly and multiplies `font_size`/
+`line_height` (and any span override) by it before handing them to
+parley — so the size that reaches both the line-breaker and the
+rasteriser (`TextData::place`, which reads back whatever `shape` set) is
+the display's *physical* size, and the glyph atlas holds a bitmap at the
+resolution it is actually shown at. `GlyphKey.size` already keys on the
+resolved size, so a cache entry is naturally per-physical-size with no
+further change. The one caller with no `Painter` to read density from
+(`TextEditCtx::layout`, cursor movement and hit-testing) reads a second
+copy kept directly on `TextData` (`TextData::density`) instead — an
+accepted duplication rather than threading a `Painter` into every input
+handler for one field, the same tradeoff `AndroidRenderer::content_scale`
+already makes for the Diagnostics page.
+
+**What did not change**: `rel`/`rest` are unaffected (already
+resolution-independent, a fraction of the parent). `Span::gap` and
+`Padding`'s four sides moved from bare `f32` to `Len` so `dp(...)` works
+on them the same as any other size; a bare number is still `abs`,
+physical pixels, unchanged.
+
 ## For IRIS.md
 
 When this lands, copy this entry into `IRIS.md` (newest first):

docs/PLAN.md

@@ -147,12 +147,37 @@ turn.
 
 Spawn: `claude -p --verbose --input-format stream-json --output-format
 stream-json --permission-mode <mode>` in the chosen working directory, plus
-`--model`. Wire-format notes are pinned against CLI 2.1.237 in
-`session/claude.rs`'s module doc: permissions need the hidden
-`--permission-prompt-tool stdio` flag, AskUserQuestion answers ride
-`updatedInput.answers` keyed by question text, and `set_model`/`interrupt`
+`--model` and, where one has been chosen, `--effort`. Wire-format notes are
+pinned against CLI 2.1.237 in `session/claude.rs`'s module doc: permissions
+need the hidden `--permission-prompt-tool stdio` flag, AskUserQuestion answers
+ride `updatedInput.answers` keyed by question text, and `set_model`/`interrupt`
 are control requests.
 
+**The thinking level is settled at launch** (added 2026-09-04, because it is
+the largest saving available on a long session: output is about an eighth of
+what a session costs and thinking is the bulk of output, against the ~1.5% that
+is prose). The CLI's only two setting control requests are `set_model` and
+`set_permission_mode` -- checked against the 2.1.258 binary -- so there is no
+way to ask a running process to think differently. `set_session_effort` is
+therefore shaped like `set_session_cwd` rather than like `set_session_model`:
+it records the level and **stops the process**, and the next message or Start
+launches one that has it. It lives in the session settings dialog beside the
+working directory for that reason, not on the session bar beside the model and
+the mode, which do take effect mid-turn. `None` is a level in its own right --
+the CLI's own default -- so the picker can return to it; a level this app named
+as the default instead would be this app choosing one.
+
+**What a new session starts at is `Config::default_effort`**, applied in
+`spawn_session` rather than filled in by the spawn screen, so it holds for an
+import and a bare API call as well. It is set by the spawn screen's own
+picker, whose label says so: one control, where new sessions are made, rather
+than a settings page for a single value. It is not on a provider, because
+providers are discovered and the next rediscovery would erase it, and not on
+the phone, because a second device would then spawn at a level nobody there
+chose. `GET`/`POST /defaults` carry it, as a struct rather than a bare value
+so the permission mode -- still hardcoded to `auto` on the spawn screen -- can
+move there without a second route.
+
 **`--resume` only ever runs when nothing else has that session open.** That
 is the rule behind the import refusal, the single `ClaudeDriver::launch`
 entry point, and the `Exited` correction below; two CLIs on one session file
@@ -169,10 +194,33 @@ deliberate and easy to undo by accident:
   when the process restarts. That leaves the Claude driver as the odd one
   out rather than this one — the CLI's memory is a cache in front of the same
   transcript. Resolve any inconsistency in this direction.
-- **A llama session on an ssh host is refused.** The model is reached over
-  HTTP and forwarding that port is not built, so refusing beats silently
-  talking to the wrong machine. A transport is "run this" plus "reach this
-  port", and only the first half exists.
+- **A llama session runs on whatever machine its setup names** (2026-09-04,
+  the last of phase 5). A transport is "run this" plus "reach this port", and
+  the second half is `Transport::reserve_port` — the port the server binds
+  *there* and the port that reaches it *here*, the same number locally —
+  carried by `Launch::reaching` onto the connection that already runs the
+  command. `llama-server` binds loopback on the far machine, so nothing is
+  served to its network. The far port is a guess from a range below the
+  ephemeral one, because no portable way to ask a machine for a free port
+  avoids racing the bind anyway; a collision is not silent, since the server
+  fails to bind and the readiness poll reports what its log said.
+- **The model file lives on the machine that serves it** (2026-09-04). Each
+  setup names its own models directory (`SshConfig::models_dir`, default
+  `~/.local/share/ai-app/models` expanded *there*), and a spawn resolves the
+  key on that machine — one round trip answering "at /abs/path" or "missing",
+  so a model that is not there is refused at the spawn rather than becoming a
+  server that never becomes ready. The spawn screen offers
+  `GET /setups/{id}/models`, that machine's list, rather than `GET /models`,
+  which is this backend's downloads. Downloading *to* another machine is
+  deliberately not built: a multi-gigabyte transfer with no progress
+  anywhere, and the file gets there however anything else on that machine
+  did.
+- **The readiness poll watches the process, not only the port.** A model that
+  will not load, a port already taken, a flag an older build does not know:
+  all exit within a second and none will ever answer `/health`, so waiting
+  out the 300s timeout turned the server's own account of the problem into
+  "gave up". The failure carries the tail of `llama-server.log`, which on a
+  remote session is the only copy anybody reading the phone can see.
 
 ### Models (2026-08-28)
 
@@ -203,6 +251,13 @@ deliberate and easy to undo by accident:
   A driver says what to run; something above it turns that into a process.
   Otherwise transport knowledge sits inside a translator whose job is a wire
   format, and every future driver has to remember to do the same.
+- **A forwarded launch gets a pty and every other one does not** (measured
+  2026-09-04). Killing the ssh client ends a CLI because it closes the stdin
+  that CLI is reading; `llama-server` never reads its stdin, so the same kill
+  left it running on the far machine with the model loaded — one orphan per
+  stopped session. With `-tt` the far side takes SIGHUP when the connection
+  goes. Its log then arrives through a line discipline, which nothing parses.
+  `-T` stays everywhere else, where a pty would rewrite the JSONL.
 - **`command -v` follows ssh's non-login PATH**, which is narrower than an
   interactive shell's, so a binary somewhere unusual is invisible to
   discovery. Point `command` at an absolute path.
@@ -499,6 +554,25 @@ rate-limited bucket). Poll at ≥180 s, only while a Claude session exists or
 the usage screen is open, and cache the last answer. It is undocumented, so
 `usage.rs` treats every field as optional and degrades rather than erroring.
 
+**Per provider, not per machine (2026-09-04).** A machine is not what is
+metered; the provider a session runs is. One machine offers echo, the Claude
+CLI and a local model side by side, and only the second spends anything — so
+pairing a session with a snapshot by machine alone drew the CLI's five-hour
+window under every echo session on it, a quota that session cannot spend. A
+session now names its meter (`usageProvider`, from
+`DriverKind::usage_provider`, which `usage::providers_for` reads too, so the
+two lists cannot disagree) and `GET /usage` is matched on machine *and*
+provider. `None` is a session that meters nothing, and the phone draws
+nothing at all for it — not a zero, and not "unknown".
+
+`DriverKind::Echo` names a meter of its own that exists only when a test has
+asked for one: `/usage` in an echo session sets an invented answer
+(`usage::Fixture`), and with none set there is no snapshot and no bar. That
+is what makes those screens' states reachable — a number near the top, a
+window between blocks with no reset time, a machine nobody logged into, one
+that could not be reached — without spending real quota to arrange them,
+which is why none of them had ever been looked at.
+
 **Per machine, not per backend (2026-08-29).** The credential store that
 matters is the one on the machine the session runs on, because that is the
 account being billed — and in the layout this aims at, `ai-server` is on the
@@ -522,6 +596,68 @@ always running. So absent means **not running**, and only a timestamp that
 arrives and cannot be parsed is unknown. `WindowEnd` in `ResetCountdown.kt`
 is the one rule both readers go through.
 
+### Auto-resume (2026-09-05)
+
+**A session may pick itself back up when the account's usage limit lifts.**
+Off unless somebody switched that session to it, because it spends quota the
+moment quota exists and does so with nobody looking — that is not a thing a
+default may decide. It sends one message, `continue` unless another was
+typed, and then it is done; there is no retry loop around the conversation
+itself.
+
+**Running out of quota is a state, not an error.** `Event::LimitReached`
+carries the dialect's reset time where it gave one, and recognising it
+belongs to the driver — the Claude CLI ends the turn with `is_error` and
+`Claude AI usage limit reached|1788546972`, and nothing above the driver
+matches on a string. The transcript draws it as a divider, like a clear or a
+compaction: what a reader scrolling back wants from it is why the
+conversation stops at that line.
+
+**The schedule is a plan to ask, never a plan to send.** Every reset time
+available here is untrustworthy in the direction that matters: the dialect's
+is written when the turn fails, and the endpoint's moves when the window
+does. So the wait ends in a question to `usage.rs`, and only `ok` with no
+window at 100% sends anything. A window still spent reschedules to *its own*
+reset time — which is what makes a limit that lifts later than promised wait
+longer, and one that lifts sooner resume sooner. A meter that cannot be
+asked at all is a longer wait too, never a send: "we could not find out"
+must not be able to produce the same action as "there is room".
+
+Bounded, because something has to be: a day after the limit was hit the wait
+stops and says so in the session's own transcript. A machine that can never
+be asked would otherwise be retried for ever with nothing on screen saying
+so.
+
+The schedule is persisted on the session (`resume: Some(ScheduledResume)`),
+not held in memory: a five-hour window routinely outlasts a backend restart,
+and a wait forgotten across one is a session that silently never comes back.
+`resume.rs` is the top layer — it holds the manager and the monitor and
+neither holds it — which is what lets the decision be a pure function of a
+snapshot and a clock. The pump reports limits downward on a broadcast, for
+the reason `Shared` exists: the pump runs underneath the manager.
+
+**Exercised with echo, never with a real account.** `/limit [minutes]` in an
+echo session reports the same event a real driver does, and `/usage` sets
+what the meter answers — deliberately two commands, because the two
+disagreeing is the state the whole design is about. The loop was driven end
+to end that way on 2026-09-05: the wait moved from the dialect's two minutes
+to the meter's seven when the meter changed its mind, and the message went
+out on the first check after the meter came back under the limit.
+
+### Subagents (2026-09-05)
+
+**A subagent is a second transcript owned by a session, in the same event
+model, with no process and no controls of its own.** Full design and wire
+shape in `SUBAGENTS.md`, kept separate because the app half is being built
+against it in parallel and it is the shared contract between the two. The
+one-paragraph reason: a session's Task-tool helpers already speak the common
+event model on the parent's own stdout (each line carrying
+`parent_tool_use_id`), so giving each one its own small transcript — same
+file format, same paging routes, same SSE stream, reused by addressing rather
+than by copying — costs a routing step in the translator and a registry
+(`session/subagent.rs`) rather than a second session type with a driver, a
+process and a config entry it does not need.
+
 ### HTTP surface
 
 **`routes.rs`'s module doc comment is the table.** REST for actions, one SSE
@@ -800,8 +936,9 @@ Noticed and deliberately not fixed, so they are not re-found from scratch.
 
 Phases 1–3 (the skeleton pipe, the full Claude driver, the usage screen) done
 2026-08-24. Phase 4 (llama.cpp: model browsing, downloads, and `llama-server`
-through its OpenAI-compatible endpoint) and phase 5 (ssh) done 2026-08-28.
-The file explorer and the transcript cache followed in September. What is
+through its OpenAI-compatible endpoint) and phase 5 (ssh) done 2026-08-28,
+except for the remote `llama-server` and its port forward, which landed
+2026-09-04. The file explorer and the transcript cache followed in September. What is
 left is real-phone/WireGuard bring-up, which is operational rather than code.
 
 Each phase ended runnable and verified against the real thing. The backend

docs/bench/compose-phone-2026-09-06.md

@@ -0,0 +1,73 @@
+# Compose bench report from Iris's phone, 2026-09-06
+
+The Compose half of P0 (RUST.md), run by Iris on her own phone and pasted
+back verbatim. The iris half's report goes beside it in this directory
+when it exists. Her caveat, worth keeping with the numbers: "I don't think
+this is entirely fair because the UI for iris is more minimal" -- the
+Compose screen also draws the usage bar, the status row and tool cards,
+which the iris bench screen does not yet. Her impression of the iris build
+before its first-touch bug: "it already feels very smooth so far".
+
+What to read first: the phone runs at 120 Hz, so the budget is 8.3 ms;
+`late` is measured against that. Compose's tail is the streaming phase --
+`markdown reparsed while streaming: 396, 8.5ms mean, 25.8ms worst` and
+`record: one block: 398, 6.3ms mean, 19.9ms worst` -- which is exactly the
+path iris's `TranscriptScreen::apply` (replace the last row only) is meant
+to beat. Process CPU over the run is 20.9 s of a 38.5 s run; peak RSS
+587 MB; battery current mean 419 mA.
+
+```
+ai-app render report
+device: Pixel 9 Pro XL (Google), Android 17
+build: release
+
+transcript:
+  43 events, 41 rows, 93 units loaded
+  viewport 1333px, 2 units visible
+  on screen: the list's own 0px, AssistantMsg 24520px
+  0 tool calls and 0 groups open
+
+frames:
+  1613 frames over 38.5s at 120Hz (8.3ms budget)
+  late: 742 (46.0%)
+  total  p50 7.7ms  p90 29.2ms  p99 41.1ms
+  waited p50 0.5ms  p90 12.9ms  p99 27.2ms
+  input  p50 0.0ms  p90 0.0ms  p99 0.0ms
+  anim   p50 1.1ms  p90 5.8ms  p99 9.5ms
+  layout p50 0.0ms  p90 0.1ms  p99 0.2ms
+  draw   p50 0.4ms  p90 15.9ms  p99 27.9ms
+  sync   p50 0.1ms  p90 0.5ms  p99 1.0ms
+  issue  p50 1.1ms  p90 1.7ms  p99 3.0ms
+  swap   p50 0.4ms  p90 0.5ms  p99 0.7ms
+  gpu    p50 1.8ms  p90 2.1ms  p99 6.6ms
+
+where the draw phase went:
+  draw phase 3.83ms per frame, of which:
+    the transcript: 0.25ms (measure 0.15, place 0.10, record 0.00)
+    everything else: 3.58ms (93%)
+
+work since this was last copied:
+  draw: the whole transcript: 12, 0.2ms total, 0.0ms mean, 0.0ms worst
+  grouped tool runs: 398, 10.3ms total, 0.0ms mean, 0.1ms worst
+  markdown cut into pieces: 1, 0.0ms total, 0.0ms mean, 0.0ms worst
+  markdown parsed while composing: 7, 3.0ms total, 0.4ms mean, 0.5ms worst
+  markdown ready: 46
+  markdown reparsed while streaming: 396, 3384.6ms total, 8.5ms mean, 25.8ms worst
+  markdown warmed: 1, 1.4ms total, 1.4ms mean, 1.4ms worst
+  measure: the whole transcript: 957, 248.7ms total, 0.3ms mean, 15.7ms worst
+  message composed: 403
+  message cut into parts: 1, 0.1ms total, 0.1ms mean, 0.1ms worst
+  place: the whole transcript: 1319, 162.4ms total, 0.1ms mean, 1.3ms worst
+  record: one block: 398, 2498.7ms total, 6.3ms mean, 19.9ms worst
+  session screen recomposed: 413
+  status row recomposed: 1
+  unit composed: 538
+  units flattened: 399, 44.3ms total, 0.1ms mean, 0.5ms worst
+  usage bar recomposed: 413
+
+bench:
+  scroll: 6 cycles (24 swipes), streamed 400/400 fixture events
+  process CPU time over this run: 20907ms
+  peak RSS: 587356kB
+  battery current: mean -418509µA over 39 samples (min -1988281, max -107812)
+```

docs/bench/compose-phone-v2-2026-09-06.md

@@ -0,0 +1,93 @@
+# Compose bench v2 report from Iris's phone, 2026-09-06
+
+Bench v2 (fling / stream / type / keyboard, RUST.md's P0 box) on the
+Compose `bench` build, run by Iris on her Pixel 9 Pro XL, verbatim. Note
+the display was at **60 Hz** for this run (16.7 ms budget) where the v1
+run was at 120 Hz -- the phone's adaptive refresh rate decides, and
+`late` is judged against whichever it was, so compare a run with a run at
+the same rate. The iris v2 report goes beside this when it exists.
+
+What it says: fling, type and keyboard are all essentially clean on
+Compose (0.1%, 0.9% and 0% late; fling p50 5.5 ms, p99 11.6 ms). The
+whole tail is the streaming phase again -- 41.9% late, p99 42.5 ms,
+driven by `markdown reparsed while streaming` (8.6 ms mean, 30.3 ms
+worst) and `record: one block` (6.3 ms mean, 25.5 ms worst). Process CPU
+69.6 s over the 125.5 s run; peak RSS 577 MB; battery current mean
+571 mA over 126 samples.
+
+```
+ai-app render report
+device: Pixel 9 Pro XL (Google), Android 17
+build: release
+
+transcript:
+  108 events, 26 rows, 58 units loaded
+  viewport 1531px, 2 units visible
+  on screen: the list's own 0px, AssistantMsg 24520px
+  0 tool calls and 0 groups open
+
+per phase:
+  fling: 3278 frames over 32.7s
+    late: 4 (0.1%)
+      total  p50 5.5ms  p90 8.7ms  p99 11.6ms
+    worst 49.0ms
+  stream: 1041 frames over 21.3s
+    late: 436 (41.9%)
+      total  p50 13.4ms  p90 31.7ms  p99 42.5ms
+    worst 52.5ms
+  type: 2446 frames over 61.5s
+    late: 23 (0.9%)
+      total  p50 7.3ms  p90 13.2ms  p99 16.5ms
+    worst 38.9ms
+  keyboard: 358 frames over 10.0s
+    late: 0 (0.0%)
+      total  p50 6.3ms  p90 8.6ms  p99 11.1ms
+    worst 12.0ms
+
+frames:
+  7122 frames over 125.5s at 60Hz (16.7ms budget)
+  late: 463 (6.5%)
+  total  p50 6.0ms  p90 13.8ms  p99 34.0ms
+  waited p50 0.5ms  p90 1.1ms  p99 19.9ms
+  input  p50 0.0ms  p90 0.0ms  p99 0.0ms
+  anim   p50 0.7ms  p90 4.5ms  p99 7.6ms
+  layout p50 0.1ms  p90 0.1ms  p99 0.2ms
+  draw   p50 0.7ms  p90 2.9ms  p99 21.9ms
+  sync   p50 0.1ms  p90 0.2ms  p99 0.6ms
+  issue  p50 1.4ms  p90 2.4ms  p99 3.2ms
+  swap   p50 0.4ms  p90 0.8ms  p99 1.2ms
+  gpu    p50 1.5ms  p90 2.1ms  p99 6.6ms
+
+where the draw phase went:
+  draw phase 1.74ms per frame, of which:
+    the transcript: 0.24ms (measure 0.10, place 0.14, record 0.00)
+    everything else: 1.51ms (86%)
+
+work since this was last copied:
+  draw: the whole transcript: 280, 1.9ms total, 0.0ms mean, 0.0ms worst
+  grouped tool runs: 407, 18.6ms total, 0.0ms mean, 0.2ms worst
+  markdown cut into pieces: 40, 0.4ms total, 0.0ms mean, 0.0ms worst
+  markdown parsed while composing: 2, 1.6ms total, 0.8ms mean, 1.1ms worst
+  markdown ready: 323
+  markdown reparsed while streaming: 395, 3406.9ms total, 8.6ms mean, 30.3ms worst
+  markdown warmed: 40, 38.2ms total, 1.0ms mean, 4.3ms worst
+  measure: the whole transcript: 1978, 683.9ms total, 0.3ms mean, 15.9ms worst
+  message composed: 397
+  message cut into parts: 40, 2.9ms total, 0.1ms mean, 0.2ms worst
+  place: the whole transcript: 4308, 996.0ms total, 0.2ms mean, 2.4ms worst
+  record: one block: 394, 2472.7ms total, 6.3ms mean, 25.5ms worst
+  session screen recomposed: 1630
+  status row recomposed: 1
+  transcript page from server: 10
+  unit composed: 927
+  units flattened: 408, 85.5ms total, 0.2ms mean, 1.8ms worst
+
+bench:
+  fling: 8 flings out + 8 back at 12000px/s, travel start=idx=0/off=0px outward=idx=188/off=182px end=idx=0/off=0px
+  scroll: 6 cycles (24 swipes, legacy tween), streamed 400/400 fixture events
+  type: 600 characters inserted then deleted, one per 50ms
+  keyboard: shown 5/5, hidden 5/5 (confirmed via isImeVisible)
+  process CPU time over this run: 69564ms
+  peak RSS: 577452kB
+  battery current: mean -571483µA over 126 samples (min -2361718, max -99218)
+```

docs/bench/iris-phone-2026-09-06-before-fixes.md

@@ -0,0 +1,31 @@
+# iris bench report from Iris's phone, 2026-09-06, before the phone fixes
+
+Build 46246ea (Vulkan, bench v1: 24-swipe scroll loop then 400 streamed
+events), run by Iris on her Pixel 9 Pro XL before the first-touch wipe,
+the missing bold faces, the density scale and the status-bar inset were
+fixed -- so the rows were drawn at roughly a third of their intended size
+and the run may have included frames after the wipe. Preliminary, kept
+because it is the first iris number from real hardware. Compare with
+`compose-phone-2026-09-06.md`, taken on the same phone with the same
+fixture and gesture loop.
+
+Reading it: the phone is 120 Hz (8.3 ms budget). `janky%` here counts
+frames over 16.7 ms, so it is not Compose's `late` (over 8.3 ms). Like for
+like: iris p50 6.2 ms vs Compose 7.7 ms; p90 32.0 vs 29.2; p99 42.1 vs
+41.1. `cpu_p50=4.7ms` is iris's own per-frame CPU work on the phone,
+against 0.2-0.4 ms on the emulator's x86 cores. Process CPU 15.6 s vs
+20.9 s, but over a shorter run (692 frames vs 1613 -- iris only renders on
+change and had no fling settle time), so per-second CPU is not directly
+comparable; peak RSS 365 MB vs 587 MB. Battery current mean 563 mA vs
+419 mA is the one figure that reads worse, and it is the least
+comparable: 22 samples vs 39, over runs of different length and different
+idle share. Bench v2's per-phase accounting is what makes these comparable.
+
+```
+iris bench report
+frames=692 janky%=32.37 p50=6.2ms p90=32.0ms p99=42.1ms worst=52.6ms (measures redraw-start to after present() is called, not GPU/compositor completion) cpu_p50=4.7ms gpu_wait_p50=1.3ms (redraw-start-to-submit vs. submit-to-after-present)
+  scroll: 6 cycles (24 swipes), streamed 400/400 fixture events
+  process CPU time over this run: 15554ms
+  peak RSS: 365328kB
+  battery current: mean -563493µA over 22 samples (min -1807812, max -132812)
+```

event-model/src/lib.rs

@@ -305,6 +305,25 @@ pub enum Event {
     /// it, which is why this is written down rather than left to be inferred
     /// from a second example that does not exist.
     Cleared,
+    /// The account behind this session has no quota left, so the turn stopped
+    /// without finishing.
+    ///
+    /// Its own event rather than an [`Event::Error`] carrying the dialect's
+    /// sentence, because two things act on it that cannot read English: the
+    /// transcript draws it as a state the session is in rather than as a
+    /// failure of something it did, and `crate::resume` schedules the message
+    /// that picks the work back up. Recognising it belongs to the driver, which
+    /// is the only layer that knows its dialect's wording -- above here nothing
+    /// matches on strings.
+    ///
+    /// `resets_at` is epoch seconds, and `None` is a real state: the dialect
+    /// said the limit was hit without saying when it lifts. Nothing here
+    /// invents one -- what the wait is actually decided against is the usage
+    /// endpoint, and this is the hint that starts the waiting.
+    LimitReached {
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        resets_at: Option<f64>,
+    },
     Error {
         message: String,
     },

iris/Cargo.lock

@@ -1757,6 +1757,7 @@ dependencies = [
  "fxhash",
  "image",
  "parley",
+ "pollster",
  "swash",
  "wgpu",
 ]
@@ -3651,6 +3652,7 @@ dependencies = [
  "client-core",
  "event-model",
  "iris",
+ "log",
  "pulldown-cmark",
 ]
 

iris/Cargo.toml

@@ -57,6 +57,16 @@ send_wrapper = "0.6.0"
 # installs it -- this crate never installs a logger itself.
 log = "0.4.28"
 
+[features]
+# RUST.md's I5 "Where iris's frame time goes" diagnosis: forces the Android
+# `wgpu::Instance` to `Backends::GL` instead of `Backends::PRIMARY`, so the
+# same build can be measured against SwiftShader's software Vulkan ICD (the
+# default) or virgl's GLES path, without a second env-var plumbing path that
+# nothing on this machine can hand to an already-launched Android process
+# (there is no `am start` environment and no system-property reader here to
+# add one). Android-only; `android/render.rs` is the only reader.
+force-gles = []
+
 [dev-dependencies]
 tokio = { workspace = true, features = ["sync", "rt", "rt-multi-thread", "time"] }
 # The tabs example's widget tree. A dev-dependency cycle back to this

iris/android-app/Cargo.lock

@@ -558,6 +558,12 @@ dependencies = [
  "arrayvec",
 ]
 
+[[package]]
+name = "base64"
+version = "0.23.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac07cdecf99051d9a5238b80f35af32cdeba5b336e55d957b318b50137e18da5"
+
 [[package]]
 name = "bit-set"
 version = "0.8.0"
@@ -734,6 +740,16 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f079e83a288787bcd14a6aea84cee5c87a67c5a3e660c30f557a3d24761b3527"
 
+[[package]]
+name = "client-core"
+version = "0.1.0"
+dependencies = [
+ "event-model",
+ "serde",
+ "serde_json",
+ "ureq",
+]
+
 [[package]]
 name = "clipboard-win"
 version = "5.4.1"
@@ -779,6 +795,35 @@ dependencies = [
  "crossbeam-utils",
 ]
 
+[[package]]
+name = "cookie"
+version = "0.18.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1a373e3602691c3cdea496d2f0ee5935151e6168fe87739483c463db1b2f2f87"
+dependencies = [
+ "percent-encoding",
+ "time",
+ "version_check",
+]
+
+[[package]]
+name = "cookie_store"
+version = "0.22.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "15b2c103cf610ec6cae3da84a766285b42fd16aad564758459e6ecf128c75206"
+dependencies = [
+ "cookie",
+ "document-features",
+ "idna",
+ "indexmap",
+ "log",
+ "serde",
+ "serde_derive",
+ "serde_json",
+ "time",
+ "url",
+]
+
 [[package]]
 name = "core-foundation"
 version = "0.9.4"
@@ -886,6 +931,12 @@ version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f27ae1dd37df86211c42e150270f82743308803d90a6f6e6651cd730d5e1732f"
 
+[[package]]
+name = "deranged"
+version = "0.5.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7cd812cc2bc1d69d4764bd80df88b4317eaef9e773c75226407d9bc0876b211c"
+
 [[package]]
 name = "dispatch"
 version = "0.2.0"
@@ -1048,6 +1099,14 @@ dependencies = [
  "pin-project-lite",
 ]
 
+[[package]]
+name = "event-model"
+version = "0.1.0"
+dependencies = [
+ "serde",
+ "serde_json",
+]
+
 [[package]]
 name = "exr"
 version = "1.74.2"
@@ -1179,6 +1238,15 @@ version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "aa9a19cbb55df58761df49b23516a86d432839add4af60fc256da840f66ed35b"
 
+[[package]]
+name = "form_urlencoded"
+version = "1.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cb4cb245038516f5f85277875cdaa4f7d2c9a0fa0468de06ed190163b1581fcf"
+dependencies = [
+ "percent-encoding",
+]
+
 [[package]]
 name = "futures-core"
 version = "0.3.34"
@@ -1253,6 +1321,26 @@ dependencies = [
  "windows-link",
 ]
 
+[[package]]
+name = "getopts"
+version = "0.2.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cfe4fbac503b8d1f88e6676011885f34b7174f46e59956bba534ba83abded4df"
+dependencies = [
+ "unicode-width",
+]
+
+[[package]]
+name = "getrandom"
+version = "0.2.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ff2abc00be7fca6ebc474524697ae276ad847ad0a6b3faa4bcb027e9a4614ad0"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "wasi",
+]
+
 [[package]]
 name = "getrandom"
 version = "0.3.4"
@@ -1423,6 +1511,22 @@ version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dfa686283ad6dd069f105e5ab091b04c62850d3e4cf5d67debad1933f55023df"
 
+[[package]]
+name = "http"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "918d3568bebf352712bc2ef3d46a8bcf1a75b373be6539de198e9105cbbf9ce0"
+dependencies = [
+ "bytes",
+ "itoa",
+]
+
+[[package]]
+name = "httparse"
+version = "1.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6dbf3de79e51f3d586ab4cb9d5c3e2c14aa28ed23d180cf89b4df0454a69cc87"
+
 [[package]]
 name = "icu_collections"
 version = "2.3.0"
@@ -1551,6 +1655,27 @@ version = "2.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ae293c039020f9ec10710af98d29ce6aa2051486638b49c9a6409f3b4a9e98ad"
 
+[[package]]
+name = "idna"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3b0875f23caa03898994f6ddc501886a45c7d3d62d04d2d90788d47be1b1e4de"
+dependencies = [
+ "idna_adapter",
+ "smallvec",
+ "utf8_iter",
+]
+
+[[package]]
+name = "idna_adapter"
+version = "1.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cb68373c0d6620ef8105e855e7745e18b0d00d3bdb07fb532e434244cdb9a714"
+dependencies = [
+ "icu_normalizer",
+ "icu_properties",
+]
+
 [[package]]
 name = "image"
 version = "0.25.10"
@@ -1640,9 +1765,15 @@ version = "0.1.0"
 dependencies = [
  "android-view",
  "android_logger",
+ "client-core",
+ "event-model",
  "iris",
+ "libc",
  "log",
+ "serde_json",
  "tabs-ui",
+ "tokio",
+ "transcript-ui",
 ]
 
 [[package]]
@@ -1654,6 +1785,7 @@ dependencies = [
  "fxhash",
  "image",
  "parley",
+ "pollster",
  "swash",
  "wgpu",
 ]
@@ -1676,6 +1808,12 @@ dependencies = [
  "either",
 ]
 
+[[package]]
+name = "itoa"
+version = "1.0.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8f42a60cbdf9a97f5d2305f08a87dc4e09308d1276d28c869c684d7777685682"
+
 [[package]]
 name = "jni"
 version = "0.21.1"
@@ -2096,6 +2234,12 @@ dependencies = [
  "num-traits",
 ]
 
+[[package]]
+name = "num-conv"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "521739c6d2bac4aa25192232afe6841231376b2b26d4d9fae5ecf8ca5772e441"
+
 [[package]]
 name = "num-derive"
 version = "0.4.2"
@@ -2744,6 +2888,12 @@ dependencies = [
  "zerovec",
 ]
 
+[[package]]
+name = "powerfmt"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "439ee305def115ba05938db6eb1644ff94165c5ab5e9420d1c1bcedbba909391"
+
 [[package]]
 name = "ppv-lite86"
 version = "0.2.21"
@@ -2796,6 +2946,25 @@ dependencies = [
  "syn 2.0.119",
 ]
 
+[[package]]
+name = "pulldown-cmark"
+version = "0.13.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e9f068eba8e7071c5f9511831b44f32c740d5adf574e990f946ddb53db2f314e"
+dependencies = [
+ "bitflags 2.13.1",
+ "getopts",
+ "memchr",
+ "pulldown-cmark-escape",
+ "unicase",
+]
+
+[[package]]
+name = "pulldown-cmark-escape"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "007d8adb5ddab6f8e3f491ac63566a7d5002cc7ed73901f72057943fa71ae1ae"
+
 [[package]]
 name = "pulp"
 version = "0.22.3"
@@ -3075,6 +3244,20 @@ version = "0.8.53"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "47b34b781b31e5d73e9fbc8689c70551fd1ade9a19e3e28cfec8580a79290cc4"
 
+[[package]]
+name = "ring"
+version = "0.17.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a4689e6c2294d81e88dc6261c768b63bc4fcdb852be6d1352498b114f61383b7"
+dependencies = [
+ "cc",
+ "cfg-if",
+ "getrandom 0.2.17",
+ "libc",
+ "untrusted",
+ "windows-sys 0.52.0",
+]
+
 [[package]]
 name = "roxmltree"
 version = "0.21.1"
@@ -3125,6 +3308,41 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "rustls"
+version = "0.23.43"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0283386ce02abc0151e1761d08802dfe86c173b0b494af5cbc086574e453da06"
+dependencies = [
+ "log",
+ "once_cell",
+ "ring",
+ "rustls-pki-types",
+ "rustls-webpki",
+ "subtle",
+ "zeroize",
+]
+
+[[package]]
+name = "rustls-pki-types"
+version = "1.15.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2f4925028c7eb5d1fcdaf196971378ed9d2c1c4efc7dc5d011256f76c99c0a96"
+dependencies = [
+ "zeroize",
+]
+
+[[package]]
+name = "rustls-webpki"
+version = "0.103.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f3c3cf1d8b1e7d4927e2d154c3fcb02979afb9939629c62cd9048d4f07b60ac2"
+dependencies = [
+ "ring",
+ "rustls-pki-types",
+ "untrusted",
+]
+
 [[package]]
 name = "rustversion"
 version = "1.0.23"
@@ -3207,6 +3425,19 @@ dependencies = [
  "syn 3.0.5",
 ]
 
+[[package]]
+name = "serde_json"
+version = "1.0.151"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c841b55ecdae098c80dcae9cf767f6f8a0c2cdb3416bbef72181df4d0fe73f14"
+dependencies = [
+ "itoa",
+ "memchr",
+ "serde",
+ "serde_core",
+ "zmij",
+]
+
 [[package]]
 name = "serde_repr"
 version = "0.1.21"
@@ -3363,6 +3594,12 @@ version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6637bab7722d379c8b41ba849228d680cc12d0a45ba1fa2b48f2a30577a06731"
 
+[[package]]
+name = "subtle"
+version = "2.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "13c2bddecc57b384dee18652358fb23172facb8a2c51ccc10d74c157bdea3292"
+
 [[package]]
 name = "swash"
 version = "0.2.10"
@@ -3490,6 +3727,36 @@ dependencies = [
  "zune-jpeg",
 ]
 
+[[package]]
+name = "time"
+version = "0.3.55"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cdb87b95ec50ddfa440816d227a17b2ccbdda963a316a727fda0fc4334f7d134"
+dependencies = [
+ "deranged",
+ "num-conv",
+ "powerfmt",
+ "serde_core",
+ "time-core",
+ "time-macros",
+]
+
+[[package]]
+name = "time-core"
+version = "0.1.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9e1c906769ad99c88eaa54e728060edef082f8e358ff32030cb7c7d315e81109"
+
+[[package]]
+name = "time-macros"
+version = "0.2.32"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7e689342a48d2ea927c87ea50cabf8594854bf940e9310208848d680d668ed85"
+dependencies = [
+ "num-conv",
+ "time-core",
+]
+
 [[package]]
 name = "tiny-skia"
 version = "0.11.4"
@@ -3596,6 +3863,17 @@ dependencies = [
  "once_cell",
 ]
 
+[[package]]
+name = "transcript-ui"
+version = "0.1.0"
+dependencies = [
+ "client-core",
+ "event-model",
+ "iris",
+ "log",
+ "pulldown-cmark",
+]
+
 [[package]]
 name = "tree_magic_mini"
 version = "3.2.2"
@@ -3634,6 +3912,12 @@ dependencies = [
  "keyboard-types",
 ]
 
+[[package]]
+name = "unicase"
+version = "2.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dbc4bc3a9f746d862c45cb89d705aa10f187bb96c76001afab07a0d35ce60142"
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.24"
@@ -3652,6 +3936,62 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b4ac048d71ede7ee76d585517add45da530660ef4390e49b098733c6e897f254"
 
+[[package]]
+name = "untrusted"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8ecb6da28b8a351d773b68d5825ac39017e680750f980f3a1a85cd8dd28a47c1"
+
+[[package]]
+name = "ureq"
+version = "3.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "972d7902c8735f2695410b8aed7df6ed12a47394aa1c8d7af49f0497b731a94d"
+dependencies = [
+ "base64",
+ "cookie_store",
+ "flate2",
+ "log",
+ "percent-encoding",
+ "rustls",
+ "rustls-pki-types",
+ "serde",
+ "serde_json",
+ "ureq-proto",
+ "utf8-zero",
+ "webpki-roots",
+]
+
+[[package]]
+name = "ureq-proto"
+version = "0.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "da5f78b09e6941e1a0f2e30e695e4b120377b54d5e0aec11b594bb57b3971613"
+dependencies = [
+ "base64",
+ "http",
+ "httparse",
+ "log",
+]
+
+[[package]]
+name = "url"
+version = "2.5.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ff67a8a4397373c3ef660812acab3268222035010ab8680ec4215f38ba3d0eed"
+dependencies = [
+ "form_urlencoded",
+ "idna",
+ "percent-encoding",
+ "serde",
+]
+
+[[package]]
+name = "utf8-zero"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b8c0a043c9540bae7c578c88f91dda8bd82e59ae27c21baca69c8b191aaf5a6e"
+
 [[package]]
 name = "utf8_iter"
 version = "1.0.4"
@@ -3696,6 +4036,12 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "wasi"
+version = "0.11.1+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ccf3ec651a847eb01de73ccad15eb7d99f80485de043efb2f370cd654f4ea44b"
+
 [[package]]
 name = "wasip2"
 version = "1.0.4+wasi-0.2.12"
@@ -3889,6 +4235,15 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "webpki-roots"
+version = "1.0.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7dcd9d09a39985f5344844e66b0c530a33843579125f23e21e9f0f220850f22a"
+dependencies = [
+ "rustls-pki-types",
+]
+
 [[package]]
 name = "weezl"
 version = "0.1.12"
@@ -4748,6 +5103,12 @@ dependencies = [
  "synstructure",
 ]
 
+[[package]]
+name = "zeroize"
+version = "1.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e13c156562582aa81c60cb29407084cdb54c4164760106ab78e6c5b0858cf64e"
+
 [[package]]
 name = "zerotrie"
 version = "0.2.5"
@@ -4789,6 +5150,12 @@ version = "0.6.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "34b31d188d9d685a4f9c7b46d6e36631b07058d2cfe190267adce54dc230bf12"
 
+[[package]]
+name = "zmij"
+version = "1.0.23"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "29666d0abbfad1e3dc4dcf6144730dd3a3ab225bbbdac83319345b1b44ccfc1b"
+
 [[package]]
 name = "zune-core"
 version = "0.5.3"

iris/android-app/Cargo.toml

@@ -17,10 +17,55 @@ crate-type = ["cdylib"]
 
 [dependencies]
 iris = { path = "../" }
-tabs-ui = { path = "../tabs-ui" }
 android-view = { git = "https://github.com/rust-mobile/android-view.git", rev = "bec6c62a96cef8239b0fd7fedeef9b184d02e3a1" }
 android_logger = "0.15.0"
 log = "0.4.28"
+# `tabs-screen` (default, I2/I4's demo) and `transcript-screen` (I5's
+# Android integration) are mutually exclusive -- one `ActiveClient` type is
+# compiled in, never both (`lib.rs`'s doc comment) -- so both sets of deps
+# are optional and each screen's feature pulls in only its own. Without
+# this, building `--features transcript-screen` alone (default features
+# still on) left `tabs-ui` linked but never referenced under that cfg,
+# which Cargo's `unused_dependencies` lint (on by default) correctly flags.
+tabs-ui = { path = "../tabs-ui", optional = true }
+transcript-ui = { path = "../transcript-ui", optional = true }
+client-core = { path = "../../client-core", optional = true }
+event-model = { path = "../../event-model", optional = true }
+serde_json = { version = "1", features = ["float_roundtrip"], optional = true }
+# P0's bench build only (docs/RUST.md): `getrusage(RUSAGE_SELF)` for
+# process CPU time, matching `libc::getrusage`'s mention in that box over
+# parsing `/proc/self/stat` by hand and assuming `USER_HZ`. Already in the
+# workspace's own dependency tree transitively (`iris/Cargo.lock`, pinned
+# at 0.2.179) -- this makes it a direct dependency at the same version
+# rather than a second, possibly-drifting resolution.
+libc = { version = "0.2.179", optional = true }
+# P0's bench build only: the scroll animation and the streaming phase are
+# both a sequence of `sleep`s inside the async task `rsc.spawn_task` already
+# runs on iris's own tokio runtime (`iris/src/task.rs`'s `Tasks::init`), and
+# the battery sampler is a second, concurrent task on that same runtime
+# (`tokio::spawn`) -- so this crate needs `tokio` directly rather than only
+# through `iris`. `rt`+`time` only: no I/O, no macros, nothing this crate
+# doesn't call. Version matches the one `iris`'s own dependency tree already
+# resolves to (`iris/Cargo.lock`), so there is one copy of the runtime, not
+# two.
+tokio = { version = "1.53.1", features = ["rt", "time"], optional = true }
+
+[features]
+default = ["tabs-screen"]
+tabs-screen = ["dep:tabs-ui"]
+transcript-screen = ["dep:transcript-ui", "dep:client-core", "dep:event-model", "dep:serde_json"]
+# RUST.md's I5 "Where iris's frame time goes": forces the GLES backend
+# instead of SwiftShader's software Vulkan. See `iris/Cargo.toml`'s own doc
+# on the feature this forwards to.
+force-gles = ["iris/force-gles"]
+# P0's iris half (docs/RUST.md, docs/AGENTS.md's "The rigs"): the same
+# checked-in fixture, scroll loop and streaming phase the Compose `bench`
+# build type drives, run here against `transcript-ui`'s real screen with no
+# server. Depends on `transcript-screen` for `transcript-ui`/`client-core`/
+# `event-model` -- `lib.rs`'s `ActiveClient` selection gives this feature
+# priority over `transcript-screen`'s own `TranscriptClient` when both are
+# listed, which is how this crate's build command names both explicitly.
+bench = ["transcript-screen", "dep:libc", "dep:tokio"]
 
 [profile.release]
 panic = "abort"

iris/android-app/app/build.gradle

@@ -19,9 +19,39 @@ android {
         versionName = "1.0"
     }
 
+    // A release build must be signed, and the key is per machine rather than per repo -- same
+    // reasoning and the same key as `app/build-apk.sh` (the Compose app): it is what a phone
+    // recognises the app by, and a secret never lives in a checkout (the mount is shared with an
+    // untrusted VM). `build-apk.sh` generates this key once and points at it through the
+    // environment; without it a release build here is unsigned, which is fine for everything
+    // except installing.
+    def keystore = System.getenv("AI_APP_KEYSTORE")
+    signingConfigs {
+        if (keystore != null) {
+            release {
+                storeFile = file(keystore)
+                storePassword = System.getenv("AI_APP_KEYSTORE_PASSWORD")
+                keyAlias = "ai-app"
+                keyPassword = storePassword
+            }
+        }
+    }
+
     buildTypes {
         debug {
         }
+        // P0's iris half (docs/RUST.md's P0 box): the build a phone actually runs. The `.so`
+        // itself is built separately with `cargo ndk --release --features "transcript-screen
+        // force-gles bench"` straight into src/main/jniLibs/ (this crate's own Cargo.toml) --
+        // Gradle here only packages and signs whatever is already there, the same division as the
+        // debug/tabs-screen build this project started with. `applicationIdSuffix` keeps it
+        // installable beside a debug build of the tabs demo rather than replacing it.
+        release {
+            applicationIdSuffix ".bench"
+            if (keystore != null) {
+                signingConfig = signingConfigs.release
+            }
+        }
     }
 
     compileOptions {

iris/android-app/app/src/main/AndroidManifest.xml

@@ -1,6 +1,15 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android">
 
+    <!-- Only needed by the transcript-screen feature (RUST.md's I5),
+         which talks to a real ai-server; the plain tabs demo (I2/I4) makes
+         no network call and never noticed this was missing. Absent,
+         UreqTransport::new's connect failed with EPERM (Operation not
+         permitted), not the ECONNREFUSED/ENETUNREACH a firewall or a dead
+         server would give: a seccomp-level socket denial reads nothing
+         like a network problem, which is what made it worth a comment. -->
+    <uses-permission android:name="android.permission.INTERNET" />
+
     <application
         android:allowBackup="true"
         android:label="iris android-view demo"

iris/android-app/app/src/main/java/dev/iris/android/demo/IrisView.java

@@ -1,6 +1,17 @@
 package dev.iris.android.demo;
 
+import android.app.Activity;
+import android.content.ClipData;
+import android.content.ClipboardManager;
 import android.content.Context;
+import android.view.Gravity;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+import android.widget.FrameLayout;
+import android.widget.LinearLayout;
+import android.widget.ScrollView;
+import android.widget.TextView;
 
 import org.linebender.android.rustview.RustView;
 
@@ -33,4 +44,112 @@ public final class IrisView extends RustView {
         unregisterInsetsNative(mViewPeer);
         super.onDetachedFromWindow();
     }
+
+    /**
+     * Called from the Rust side (iris/src/android/view.rs's
+     * `show_renderer_error`) when `AndroidRenderer::new` fails instead of
+     * drawing -- an ordinary instance method rather than a `native` one,
+     * since this call is Rust reaching into Java rather than the other
+     * direction. Replaces the whole activity content with plain,
+     * selectable, scrollable text rather than leaving the last frame (or a
+     * blank surface) on screen with no way to report what happened:
+     * UI_RULES.md's "a failure is reported where it happened, and says
+     * what to do next." No dialog and no styling beyond what is needed to
+     * read and copy the text -- this path exists for exactly the crash it
+     * replaces, so it must not depend on anything that could itself fail
+     * to render.
+     */
+    void showRendererError(String report) {
+        Context context = getContext();
+        if (!(context instanceof Activity)) {
+            return;
+        }
+        Activity activity = (Activity) context;
+        TextView text = new TextView(activity);
+        text.setText(report);
+        text.setTextIsSelectable(true);
+        text.setGravity(Gravity.TOP | Gravity.START);
+        int pad = (int) (16 * activity.getResources().getDisplayMetrics().density);
+        text.setPadding(pad, pad, pad, pad);
+        ScrollView scroll = new ScrollView(activity);
+        scroll.addView(text);
+        activity.setContentView(scroll);
+    }
+
+    private static final String DIAGNOSTICS_OVERLAY_TAG = "iris-diagnostics-overlay";
+
+    /**
+     * The bench build's keyboard diagnostics capture
+     * (`bench_client.rs`'s `on_insets_changed` /
+     * `capture_keyboard_diagnostics`, via `bench_jni.rs`'s
+     * `PlatformHandle::show_diagnostics_overlay`): unlike
+     * `showRendererError` above, this adds a panel *over* this view
+     * (`MainActivity`'s `FrameLayout` still holds `IrisView` underneath,
+     * running) rather than replacing the activity's content, and gives it
+     * a Copy button and a Close that removes the panel -- so it draws
+     * (and can be read) whether or not iris itself is still putting
+     * anything on screen, without abandoning the session that produced
+     * it. Runs on the UI thread regardless of which thread calls it,
+     * since the call comes from a background task (a delayed capture
+     * after the keyboard opens), and touching the view tree off the UI
+     * thread is undefined.
+     */
+    void showDiagnosticsOverlay(String report) {
+        Context context = getContext();
+        if (!(context instanceof Activity)) {
+            return;
+        }
+        Activity activity = (Activity) context;
+        activity.runOnUiThread(() -> {
+            ViewGroup parent = (ViewGroup) getParent();
+            if (parent == null) {
+                return;
+            }
+            View existing = parent.findViewWithTag(DIAGNOSTICS_OVERLAY_TAG);
+            if (existing != null) {
+                parent.removeView(existing);
+            }
+
+            float density = activity.getResources().getDisplayMetrics().density;
+            int pad = (int) (16 * density);
+
+            LinearLayout overlay = new LinearLayout(activity);
+            overlay.setTag(DIAGNOSTICS_OVERLAY_TAG);
+            overlay.setOrientation(LinearLayout.VERTICAL);
+            overlay.setBackgroundColor(0xEE000000);
+            overlay.setPadding(pad, pad, pad, pad);
+
+            TextView text = new TextView(activity);
+            text.setText(report);
+            text.setTextIsSelectable(true);
+            text.setTextColor(0xFFFFFFFF);
+            ScrollView scroll = new ScrollView(activity);
+            scroll.addView(text);
+            overlay.addView(scroll, new LinearLayout.LayoutParams(
+                    LinearLayout.LayoutParams.MATCH_PARENT, 0, 1f));
+
+            LinearLayout buttonRow = new LinearLayout(activity);
+            buttonRow.setOrientation(LinearLayout.HORIZONTAL);
+            buttonRow.setPadding(0, pad, 0, 0);
+
+            Button copy = new Button(activity);
+            copy.setText("Copy");
+            copy.setOnClickListener(v -> {
+                ClipboardManager clipboard =
+                        (ClipboardManager) activity.getSystemService(Context.CLIPBOARD_SERVICE);
+                if (clipboard != null) {
+                    clipboard.setPrimaryClip(ClipData.newPlainText("iris diagnostics", report));
+                }
+            });
+            Button close = new Button(activity);
+            close.setText("Close");
+            close.setOnClickListener(v -> parent.removeView(overlay));
+            buttonRow.addView(copy);
+            buttonRow.addView(close);
+            overlay.addView(buttonRow);
+
+            parent.addView(overlay, new FrameLayout.LayoutParams(
+                    FrameLayout.LayoutParams.MATCH_PARENT, FrameLayout.LayoutParams.MATCH_PARENT));
+        });
+    }
 }

iris/android-app/app/src/main/java/dev/iris/android/demo/MainActivity.java

@@ -36,9 +36,28 @@ public final class MainActivity extends Activity {
             int top = insets.getSystemWindowInsetTop();
             int right = insets.getSystemWindowInsetRight();
             int bottom = insets.getSystemWindowInsetBottom();
+            // The manifest declares adjustResize (AGENTS.md: without it the
+            // keyboard pans the whole window instead of resizing it), and
+            // under adjustResize the window itself shrinks to make room for
+            // the keyboard -- which is exactly the condition under which
+            // WindowInsets.Type.ime()'s own *inset amount* reports zero: it
+            // measures how much of the window the keyboard overlaps, and
+            // resize already made that overlap zero by construction. That
+            // numeric inset is not a usable "is the keyboard open" signal
+            // here (found while root-causing why bench_client.rs's keyboard
+            // phase and auto-diagnostics never fired on the emulator despite
+            // the keyboard visibly opening -- RUST.md's P0 box). What does
+            // survive adjustResize is the boolean isVisible() answer, set
+            // from the platform's own start/end of the transition over a
+            // different path than the inset amount -- the same fact
+            // AGENTS.md's "Things that have bitten" already names for the
+            // Compose side's identical trap. Passed through as a 0/1 stand-
+            // in for the ime_bottom pixel amount, since nothing on the Rust
+            // side reads it as a real pixel value -- only `> 0.0`.
             int imeBottom = 0;
-            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
-                imeBottom = insets.getInsets(WindowInsets.Type.ime()).bottom;
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R
+                    && insets.isVisible(WindowInsets.Type.ime())) {
+                imeBottom = 1;
             }
             ((IrisView) v).applyWindowInsets(left, top, right, bottom, imeBottom);
             return insets;

iris/android-app/build-apk.sh

@@ -0,0 +1,90 @@
+#!/bin/sh
+# Builds iris-android-app end to end: the cdylib (cargo ndk, straight into
+# app/src/main/jniLibs/) then the APK (Gradle). Written to stop re-typing
+# the same incantation by hand every time (ANDROID_HOME/NDK exports, the
+# cargo ndk invocation, the keystore env for a release build, apksigner/
+# aapt2 verification) -- see docs/RUST.md's P0 box. Same shape as `app/
+# build-apk.sh` (the Compose app's own build script) and `app/
+# iris-scroll.sh` (no coordinates, set -eu, exit 0 on success).
+#
+# Usage: ./build-apk.sh [debug|release] [--abi arm64-v8a|x86_64] [--features "a b c"]
+#   debug/release default to debug (matches this-machine-android's "the
+#   emulator stays on debug" rule -- pass `release` explicitly for a phone
+#   build). --abi defaults to arm64-v8a (a phone/real device); pass
+#   x86_64 for this checkout's own AVD. --features defaults to
+#   "transcript-screen bench" -- deliberately *without* `force-gles`, unlike
+#   an earlier version of this default. `force-gles` (`iris/Cargo.toml`'s
+#   own doc) exists only to force the emulator off its default software
+#   Vulkan and onto GLES for one specific measurement (RUST.md's I5, "Where
+#   iris's frame time goes") -- it was never meant to reach a real device,
+#   but this script's old default put it in every arm64 build regardless,
+#   so the P0 bench APK delivered to Iris's phone forced GLES there too.
+#   That is the named hypothesis in RUST.md's P0 box ("iris bench crash on
+#   the phone, 2026-09-06"): a real Vulkan driver is what a phone should
+#   run, and GLES is the backend the same box's own SwiftShader finding
+#   already flagged as the fragile one for this shader's storage buffers.
+#   Pass `--features "transcript-screen force-gles bench"` explicitly for
+#   an emulator backend-isolation run; never for a build meant for a phone.
+set -eu
+cd "$(dirname "$0")"
+
+BUILD_TYPE="debug"
+ABI="arm64-v8a"
+FEATURES="transcript-screen bench"
+case "${1:-}" in
+    debug|release) BUILD_TYPE="$1"; shift ;;
+esac
+while [ $# -gt 0 ]; do
+    case "$1" in
+        --abi) ABI="$2"; shift 2 ;;
+        --features) FEATURES="$2"; shift 2 ;;
+        *) echo "build-apk.sh: unknown argument: $1" >&2; exit 1 ;;
+    esac
+done
+
+SDK_ROOT="$HOME/Android/Sdk"
+export ANDROID_HOME="$SDK_ROOT"
+export ANDROID_SDK_ROOT="$SDK_ROOT"
+NDK_DIR=$(ls -d "$SDK_ROOT"/ndk/*/ 2>/dev/null | sort -V | tail -1)
+if [ -z "$NDK_DIR" ]; then
+    echo "build-apk.sh: no NDK found under $SDK_ROOT/ndk" >&2
+    exit 1
+fi
+export ANDROID_NDK_HOME="$NDK_DIR"
+
+echo "build-apk.sh: cargo ndk -t $ABI build ${BUILD_TYPE:+(${BUILD_TYPE})} --features \"$FEATURES\""
+if [ "$BUILD_TYPE" = "release" ]; then
+    cargo ndk -t "$ABI" -P 26 -o app/src/main/jniLibs/ build --release --features "$FEATURES"
+else
+    cargo ndk -t "$ABI" -P 26 -o app/src/main/jniLibs/ build --features "$FEATURES"
+fi
+
+GRADLE_TASK="assembleDebug"
+APK_DIR="app/build/outputs/apk/debug"
+APK_NAME="app-debug.apk"
+if [ "$BUILD_TYPE" = "release" ]; then
+    GRADLE_TASK="assembleRelease"
+    APK_DIR="app/build/outputs/apk/release"
+    APK_NAME="app-release.apk"
+    # Same key `app/build-apk.sh` (the Compose app) generates once under
+    # ~/.config/ai-app/release.jks -- see AGENTS.md's "Checking your work".
+    export AI_APP_KEYSTORE="$HOME/.config/ai-app/release.jks"
+    if [ ! -f "$AI_APP_KEYSTORE" ]; then
+        echo "build-apk.sh: no release key at $AI_APP_KEYSTORE -- run app/build-apk.sh once first" >&2
+        exit 1
+    fi
+    export AI_APP_KEYSTORE_PASSWORD
+    AI_APP_KEYSTORE_PASSWORD=$(cat "$AI_APP_KEYSTORE.password")
+fi
+
+gradle ":app:$GRADLE_TASK" --console=plain
+
+APK_PATH="$(pwd)/$APK_DIR/$APK_NAME"
+BUILD_TOOLS=$(ls -d "$SDK_ROOT"/build-tools/*/ | sort -V | tail -1)
+echo "--- aapt2 dump badging ---"
+"${BUILD_TOOLS}aapt2" dump badging "$APK_PATH" | head -5
+if [ "$BUILD_TYPE" = "release" ]; then
+    echo "--- apksigner verify ---"
+    "${BUILD_TOOLS}apksigner" verify --print-certs "$APK_PATH"
+fi
+echo "$APK_PATH"

iris/android-app/build.rs

@@ -0,0 +1,100 @@
+// Only does anything under the `transcript-screen` feature (RUST.md's I5
+// Android integration) -- the plain tabs build (I2/I4) needs none of this
+// and stays untouched, same reasoning as the feature gate in Cargo.toml.
+//
+// Bakes the sandbox server's host, port, token and pinned CA in at build
+// time, the same way `app/androidApp/build.gradle.kts`'s
+// `GeneratePinnedCert` task bakes the CA for the Compose app -- see that
+// file's comment for why reading the machine's own certificate at build
+// time is the right trust boundary. This build additionally bakes the
+// host/port/token, which the Compose app does not: that app enrolls at
+// runtime from a scanned QR/deep link, and a from-scratch enrollment UI
+// (Keystore-sealed token storage, a QR/link scanner) is real, separate
+// scope this integration does not need to build to answer RUST.md's
+// question -- there is nothing here yet resembling `ServerConfig.kt`. So
+// this is a **deliberate simplification for this rig only**: an APK built
+// this way is good for exactly the emulator/server pair that built it, and
+// must never be treated as a template for a real enrollment flow. Recorded
+// in RUST.md's I5 box rather than left to be rediscovered.
+use std::path::PathBuf;
+
+fn main() {
+    if std::env::var_os("CARGO_FEATURE_TRANSCRIPT_SCREEN").is_none() {
+        return;
+    }
+    // P0's bench build (docs/RUST.md) opens the checked-in fixture with no
+    // server at all -- `bench_client.rs` never references the `pinned`
+    // module this generates, so requiring a live server's host/port/token/
+    // CA to build it (as plain `transcript-screen` does, below) would be a
+    // pointless requirement for a build that talks to nothing.
+    if std::env::var_os("CARGO_FEATURE_BENCH").is_some() {
+        return;
+    }
+    println!("cargo:rerun-if-env-changed=AI_APP_TRANSCRIPT_HOST");
+    println!("cargo:rerun-if-env-changed=AI_APP_TRANSCRIPT_PORT");
+    println!("cargo:rerun-if-env-changed=AI_APP_TRANSCRIPT_TOKEN");
+    println!("cargo:rerun-if-env-changed=AI_APP_CA");
+    println!("cargo:rerun-if-env-changed=XDG_CONFIG_HOME");
+
+    let host = require_env(
+        "AI_APP_TRANSCRIPT_HOST",
+        "the sandbox server's host as the emulator reaches it, e.g. 10.0.2.2",
+    );
+    let port = require_env(
+        "AI_APP_TRANSCRIPT_PORT",
+        "the sandbox server's port -- app/ui-sandbox.sh's start banner prints it",
+    );
+    let token = require_env(
+        "AI_APP_TRANSCRIPT_TOKEN",
+        "the bearer token -- ~/.config/ai-app/sandbox-token, or the start banner's enrollment link",
+    );
+
+    let ca_path = std::env::var_os("AI_APP_CA")
+        .map(PathBuf::from)
+        .unwrap_or_else(|| {
+            let base = std::env::var_os("XDG_CONFIG_HOME")
+                .map(PathBuf::from)
+                .unwrap_or_else(|| {
+                    let home = std::env::var_os("HOME").expect("HOME must be set");
+                    PathBuf::from(home).join(".config")
+                });
+            base.join("ai-app").join("certs").join("ca.pem")
+        });
+    let ca_pem = std::fs::read_to_string(&ca_path).unwrap_or_else(|e| {
+        panic!(
+            "no CA certificate at {} ({e}).\n\
+             Start ai-server (or app/ui-sandbox.sh) once on this machine first -- it \
+             generates the CA this build pins. Set AI_APP_CA=/path/to/ca.pem to build \
+             against a different one.",
+            ca_path.display()
+        )
+    });
+    let ca_pem = ca_pem.trim();
+    if !ca_pem.starts_with("-----BEGIN CERTIFICATE-----") {
+        panic!("{} is not a PEM certificate.", ca_path.display());
+    }
+
+    let out_dir = PathBuf::from(std::env::var_os("OUT_DIR").unwrap());
+    let generated = format!(
+        "// Generated by build.rs from {host}:{port} and {ca}. Do not edit.\n\
+         pub const HOST: &str = {host_lit:?};\n\
+         pub const PORT: u16 = {port};\n\
+         pub const TOKEN: &str = {token_lit:?};\n\
+         pub const CA_PEM: &str = {ca_lit:?};\n",
+        host = host,
+        port = port
+            .parse::<u16>()
+            .unwrap_or_else(|e| panic!("AI_APP_TRANSCRIPT_PORT={port:?} is not a u16: {e}")),
+        ca = ca_path.display(),
+        host_lit = host,
+        token_lit = token,
+        ca_lit = ca_pem,
+    );
+    std::fs::write(out_dir.join("pinned_config.rs"), generated).unwrap();
+}
+
+fn require_env(name: &str, what: &str) -> String {
+    std::env::var(name).unwrap_or_else(|_| {
+        panic!("{name} must be set to build the transcript-screen feature -- {what}")
+    })
+}

iris/android-app/run-bench.sh

@@ -0,0 +1,69 @@
+#!/bin/sh
+# Installs and runs the iris `bench` build on this checkout's own emulator
+# (per this-machine-android's per-checkout-AVD rule; `emu serial` picks it)
+# and prints the report -- the iris half of `app/transcript-bench.sh`'s
+# job. No coordinates: the button is found by its accessibility label
+# through `ui-trace`, per AGENTS.md's "Driving the UI".
+#
+# Usage: ./run-bench.sh [--apk PATH]
+#   Defaults to this checkout's own release APK
+#   (app/build/outputs/apk/release/app-release.apk) if it exists, else the
+#   debug one -- build one first with ./build-apk.sh.
+set -eu
+cd "$(dirname "$0")"
+
+APK=""
+while [ $# -gt 0 ]; do
+    case "$1" in
+        --apk) APK="$2"; shift 2 ;;
+        *) echo "run-bench.sh: unknown argument: $1" >&2; exit 1 ;;
+    esac
+done
+if [ -z "$APK" ]; then
+    if [ -f app/build/outputs/apk/release/app-release.apk ]; then
+        APK=app/build/outputs/apk/release/app-release.apk
+    else
+        APK=app/build/outputs/apk/debug/app-debug.apk
+    fi
+fi
+if [ ! -f "$APK" ]; then
+    echo "run-bench.sh: no APK at $APK -- run ./build-apk.sh first" >&2
+    exit 1
+fi
+
+SERIAL=$(emu serial)
+PKG=$(aapt2 dump badging "$APK" 2>/dev/null | sed -n "s/^package: name='\\([^']*\\)'.*/\\1/p")
+if [ -z "$PKG" ]; then
+    BUILD_TOOLS=$(ls -d "$HOME"/Android/Sdk/build-tools/*/ | sort -V | tail -1)
+    PKG=$("${BUILD_TOOLS}aapt2" dump badging "$APK" | sed -n "s/^package: name='\\([^']*\\)'.*/\\1/p")
+fi
+
+echo "run-bench.sh: installing $APK ($PKG) on $SERIAL"
+adb -s "$SERIAL" install -r "$APK" >/dev/null
+adb -s "$SERIAL" shell am force-stop "$PKG"
+adb -s "$SERIAL" logcat -c
+adb -s "$SERIAL" shell am start -n "$PKG/dev.iris.android.demo.MainActivity" >/dev/null
+
+ui-trace record -s "$SERIAL" -d 3000 --do "tap 'Run benchmark'" -o /tmp/run-bench-tap.txt >/dev/null
+
+# Poll for the report line rather than a fixed sleep -- the run itself is
+# a fixed script (RUST.md's "Benchmark v2": 16 flings, a 20s streaming
+# phase, ~61s of typing, 10s of keyboard toggles, roughly 2.5 minutes end
+# to end) but device speed varies. 260s cap rather than v1's 90s -- v2 is
+# a longer script than v1's swipe-loop-only run.
+i=0
+while [ "$i" -lt 260 ]; do
+    LINE=$(adb -s "$SERIAL" logcat -d -s iris-android-app:I 2>/dev/null | grep "iris bench report:" || true)
+    if [ -n "$LINE" ]; then
+        break
+    fi
+    i=$((i + 1))
+    sleep 1
+done
+if [ -z "$LINE" ]; then
+    echo "run-bench.sh: no report after 260s -- check logcat by hand" >&2
+    exit 1
+fi
+# -A 60 rather than v1's -A 6 -- v2's report has a per-phase block (four
+# phases, four lines each) on top of the frames/bench sections v1 had.
+adb -s "$SERIAL" logcat -d -s iris-android-app:I | grep -A 60 "iris bench report:"

iris/android-app/src/bench_client.rs

@@ -0,0 +1,988 @@
+//! P0's iris half (docs/RUST.md's P0 box, docs/AGENTS.md's "The rigs"):
+//! the same fixture, scroll loop and streaming phase the Compose `bench`
+//! build type's `BenchRun.kt`/`BenchFixture.kt` drive, run here against
+//! `transcript-ui`'s real screen with no server -- a frame-time comparison
+//! that measures the renderer rather than the data or the network.
+//!
+//! **Reuses `transcript_client.rs`'s shape** (folded items, the same
+//! `TranscriptScreen::apply` incremental update on every event) with the
+//! network half replaced by the checked-in fixture, embedded with
+//! `include_str!` -- `app/bench-fixture/assets/transcript.jsonl`,
+//! 1,915,760 bytes, generated by `app/bench-fixture/generate.py` and never
+//! a real transcript (that file's own README). The first 3,200 lines are
+//! the opening backlog, folded once through
+//! `client_core::transcript_fold::fold_page` exactly as a real
+//! `/transcript` page would be (then a full `transcript_ui::build_tree`,
+//! same as any first load); the remaining ~400 are the streaming tail,
+//! replayed one at a time through `fold_event` -- the same fold path a
+//! live SSE reply arrives on -- by the "Run benchmark" control below.
+//! Streaming through `apply` rather than a full rebuild per event is what
+//! this file exists to measure -- see docs/RUST.md's P0 box for the
+//! before/after report.
+
+use crate::bench_jni::PlatformHandle;
+use android_view::jni::{JavaVM, objects::GlobalRef};
+use client_core::transcript_fold::{TranscriptItem, fold_event, fold_page, group_tool_runs};
+use event_model::SeqEvent;
+use iris::android::{AndroidAppState, AndroidRsc, AndroidUiState, HasAndroidUiState};
+use iris::prelude::*;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::{Arc, Mutex};
+use std::time::{Duration, Instant};
+
+/// bench-fixture/README.md: the first `BACKLOG_COUNT` non-blank lines are
+/// the opening window; the rest are the streaming tail. Kept in sync with
+/// `BenchFixture.kt`'s identical constant by hand -- both read the same
+/// checked-in file, so a mismatch would only mean the two apps' bench
+/// builds open a different split of it, not a wrong-vs-right answer.
+const BACKLOG_COUNT: usize = 3200;
+
+/// RUST.md's "Benchmark v2" spec, written once so both apps' bench clients
+/// implement the identical four phases -- see that box before changing any
+/// constant here, since a mismatch would make the two reports stop
+/// measuring the same thing while still looking like they do.
+const STREAM_EVENTS_PER_SEC: u64 = 20;
+const STREAM_SECONDS: u64 = 20;
+
+/// Kept only so this phase's own label text still reads "scroll: 6 cycles
+/// (24 swipes, legacy tween)" the way `BenchRun.kt`'s v2 report does --
+/// `docs/bench/compose-phone-v2-2026-09-06.md`'s own report shows this
+/// exact line even though the swipe loop it names no longer runs there
+/// either (the fling phase replaced it); nothing here drives an actual
+/// swipe with these any more.
+const LEGACY_CYCLES: usize = 6;
+
+/// Fling phase (v2): a real fling through `List::fling`, not a tween --
+/// Iris's ask was that it "travel way faster" than the v1 swipe, and a
+/// tween can never exceed the distance/time it is given while a real
+/// fling decays from an initial velocity the way a finger flick does.
+/// 12,000 px/s matches `BenchRun.kt`'s own constant exactly.
+const FLING_VELOCITY_PX_S: f32 = 12_000.0;
+const FLING_COUNT: usize = 8;
+const FLING_SETTLE_CAP_MS: u64 = 3_000;
+const FLING_PAUSE_MS: u64 = 300;
+
+/// Type phase (v2): long, multisyllabic words so the composer actually
+/// wraps and the transcript above it is pushed upward, typed and deleted
+/// one character per `TYPE_CHAR_MS`. Exactly `BenchRun.TYPE_TEXT` --
+/// verified 600 characters by `type_text_is_exactly_600_characters` below.
+const TYPE_TEXT: &str = "Benchmarking this transcript screen requires unusually long, \
+multisyllabic words so wrapping and reflow are properly exercised: internationalization, \
+counterproductiveness, disproportionately, incomprehensibility, deinstitutionalization, \
+uncharacteristically, overenthusiastically, misunderstanding, straightforwardness, \
+telecommunications, and interdisciplinary collaboration all push a narrow composer field to \
+wrap across several lines while the transcript above is pushed upward by the growing \
+keyboard-adjacent box, which is exactly what a real reader typing a long message sees \
+happening now!!!";
+const TYPE_CHAR_MS: u64 = 50;
+
+/// Keyboard phase (v2): five show/hide cycles, a second apart, matching
+/// `BenchRun.kt`'s `KEYBOARD_CYCLES`/`KEYBOARD_SHOW_WAIT_MS`/
+/// `KEYBOARD_HIDE_WAIT_MS`.
+const KEYBOARD_CYCLES: usize = 5;
+const KEYBOARD_WAIT_MS: u64 = 1_000;
+
+/// One animation step's target cadence -- close enough to 60Hz that a
+/// fling/scroll is many small moves rather than one jump, so frames are
+/// actually rendered along the way, and close enough that a `ctx.update`
+/// closure's effect (only applied once the next frame callback drains the
+/// task channel -- `IrisViewPeer::drain_tasks`) is visible again quickly
+/// when a later step in the same phase needs to read state back.
+const ANIM_STEP_MS: u64 = 16;
+
+const FIXTURE_JSONL: &str = include_str!("../../../app/bench-fixture/assets/transcript.jsonl");
+
+pub struct BenchClient {
+    ui_state: AndroidUiState,
+    content: WeakWidget<WidgetPtr>,
+    report_display: WeakWidget<TextEdit>,
+    /// The top button row, in a `WidgetPtr` slot rather than added
+    /// directly (like `content`) so `on_insets_changed` can swap in a
+    /// version padded for the status bar once insets are known -- RUST.md's
+    /// P0 box, "the status-bar inset is not applied," found the row sitting
+    /// directly under it because nothing here read `insets().top` at all.
+    top_bar: WeakWidget<WidgetPtr>,
+    screen: Option<transcript_ui::TranscriptScreen>,
+    items: Vec<TranscriptItem>,
+    /// The events not yet streamed -- consumed by `start_benchmark`'s own
+    /// clone, kept here only as the source a second run would need (the
+    /// button can be pressed more than once; `running` just stops overlap,
+    /// not repeat).
+    stream_tail: Vec<SeqEvent>,
+    platform: Option<Arc<PlatformHandle>>,
+    last_report: Option<String>,
+    running: bool,
+    /// The keyboard phase's own confirmation channel -- updated from
+    /// `on_insets_changed` (the platform's own answer for whether the IME
+    /// is actually visible, per `WindowInsets::ime_bottom`), read from the
+    /// benchmark's spawned task via the shared `Arc<Mutex<_>>` rather than
+    /// `ctx.update`, since neither side needs the widget tree for this.
+    ime_state: Arc<Mutex<ImeState>>,
+    /// Edge-triggers the keyboard diagnostics capture below -- set on the
+    /// first `on_insets_changed` where `ime_bottom > 0.0`, cleared on the
+    /// first where it is not, so opening the keyboard fires this once
+    /// rather than on every insets update while it stays open (a rotation
+    /// or a status-bar change with the keyboard already up would otherwise
+    /// re-fire it).
+    keyboard_was_visible: bool,
+    /// The status-bar inset `top_bar` was last padded by -- see
+    /// `on_insets_changed`'s own comment for why this guards the rebuild.
+    last_top_pad: f32,
+}
+
+/// See `BenchClient::ime_state`'s doc. `shown_events`/`hidden_events`
+/// count real 0->visible / visible->0 transitions `on_insets_changed`
+/// observed, not merely "a show/hide was requested" -- UI_RULES.md: never
+/// present an inferred value as a measured one. `run_keyboard_phase` reads
+/// the counters before and after asking for a toggle and calls it
+/// confirmed only if the count moved.
+#[derive(Default)]
+struct ImeState {
+    visible: bool,
+    shown_events: u32,
+    hidden_events: u32,
+}
+
+impl HasAndroidUiState for BenchClient {
+    fn android_state(&self) -> &AndroidUiState {
+        &self.ui_state
+    }
+    fn android_state_mut(&mut self) -> &mut AndroidUiState {
+        &mut self.ui_state
+    }
+}
+
+/// Parses the fixture once: `serde_json::Value`s for the backlog
+/// (`fold_page` takes a page of raw wire JSON, same as a real
+/// `/transcript` response) and folded `SeqEvent`s for the tail (`fold_event`
+/// takes one live wire event at a time, same as a real SSE frame).
+fn parse_fixture() -> (Vec<serde_json::Value>, Vec<SeqEvent>) {
+    let lines: Vec<&str> = FIXTURE_JSONL
+        .lines()
+        .filter(|line| !line.trim().is_empty())
+        .collect();
+    let mut backlog = Vec::with_capacity(BACKLOG_COUNT.min(lines.len()));
+    let mut stream_tail = Vec::new();
+    for (i, line) in lines.iter().enumerate() {
+        let value: serde_json::Value =
+            serde_json::from_str(line).expect("bench fixture is generated JSON, always valid");
+        if i < BACKLOG_COUNT {
+            backlog.push(value);
+        } else {
+            let event: SeqEvent = serde_json::from_value(value)
+                .expect("bench fixture event matches event-model's SeqEvent");
+            stream_tail.push(event);
+        }
+    }
+    (backlog, stream_tail)
+}
+
+fn placeholder<Rsc: HasEvents>(rsc: &mut Rsc, message: &str) -> StrongWidget {
+    wtext(message.to_string())
+        .color(Color::WHITE)
+        .wrap(true)
+        .pad(16)
+        .add_strong(rsc)
+        .any()
+}
+
+/// `getrusage(RUSAGE_SELF)`'s user+system time, in ms -- `None` only if
+/// the syscall itself fails, which UI_RULES.md's "never present an
+/// inferred value as a measured one" says to keep apart from a real (and
+/// here, impossible) zero.
+fn process_cpu_ms() -> Option<u64> {
+    // SAFETY: `rusage` is a plain-old-data struct `getrusage` fully
+    // initialises on success; on failure it is never read.
+    unsafe {
+        let mut usage: libc::rusage = std::mem::zeroed();
+        if libc::getrusage(libc::RUSAGE_SELF, &mut usage) != 0 {
+            return None;
+        }
+        let user_ms = usage.ru_utime.tv_sec as u64 * 1000 + usage.ru_utime.tv_usec as u64 / 1000;
+        let sys_ms = usage.ru_stime.tv_sec as u64 * 1000 + usage.ru_stime.tv_usec as u64 / 1000;
+        Some(user_ms + sys_ms)
+    }
+}
+
+/// `VmHWM` from `/proc/self/status` -- the process's peak RSS since it
+/// started, in kB. Same source `BenchRun.kt`'s `peakRssLine` reads, so the
+/// two reports' numbers mean the same thing.
+fn peak_rss_kb() -> Option<u64> {
+    std::fs::read_to_string("/proc/self/status")
+        .ok()?
+        .lines()
+        .find_map(|line| line.strip_prefix("VmHWM:"))
+        .and_then(|rest| rest.trim().strip_suffix("kB"))
+        .and_then(|n| n.trim().parse().ok())
+}
+
+fn battery_line(samples: &[i32]) -> String {
+    if samples.is_empty() {
+        return "  battery current: unavailable on this device".to_string();
+    }
+    let mean = samples.iter().map(|&v| v as i64).sum::<i64>() / samples.len() as i64;
+    let min = samples.iter().min().unwrap();
+    let max = samples.iter().max().unwrap();
+    format!(
+        "  battery current: mean {mean}\u{b5}A over {} samples (min {min}, max {max})",
+        samples.len()
+    )
+}
+
+impl AndroidAppState for BenchClient {
+    fn new(mut ui_state: AndroidUiState, rsc: &mut AndroidRsc<Self>) -> Self {
+        let content = WidgetPtr::new().add(rsc);
+        let loading = placeholder(rsc, "Loading fixture...");
+        content(rsc).set(loading);
+
+        let report_display = wtext("")
+            .editable(EditMode::MultiLine)
+            .text_align(Align::LEFT)
+            .wrap(true)
+            .size(14)
+            .color(Color::WHITE)
+            .attr::<Selectable>(())
+            .label("Benchmark report")
+            .add(rsc);
+
+        let top_bar = WidgetPtr::new().add(rsc);
+        let controls = bench_controls(rsc, 0.0);
+        top_bar(rsc).set(controls);
+        let tree = (
+            top_bar,
+            content.height(rest(2)),
+            report_display.height(rest(1)).pad(dp(8)),
+        )
+            .span(Dir::DOWN)
+            .add_strong(rsc)
+            .any();
+        ui_state.set_root(tree);
+
+        // Startup log line (RUST.md's P0 box, "log once at startup ... the
+        // number of font families found, the default family resolved"):
+        // what font discovery actually found on this device, before
+        // anything is drawn.
+        let font = rsc.ui.text.font_diagnostics();
+        log::info!(
+            "iris fonts: {} families found, default={:?} mono={:?}, resolved regular={:?} \
+             bold={:?} italic={:?} mono={:?}",
+            font.families_found,
+            font.default_family,
+            font.default_mono_family,
+            font.regular_resolved,
+            font.bold_resolved,
+            font.italic_resolved,
+            font.mono_resolved,
+        );
+
+        let mut client = Self {
+            ui_state,
+            content,
+            report_display,
+            top_bar,
+            screen: None,
+            items: Vec::new(),
+            stream_tail: Vec::new(),
+            platform: None,
+            last_report: None,
+            running: false,
+            ime_state: Arc::new(Mutex::new(ImeState::default())),
+            keyboard_was_visible: false,
+            last_top_pad: 0.0,
+        };
+
+        let (backlog, stream_tail) = parse_fixture();
+        client.stream_tail = stream_tail;
+        match fold_page(&backlog) {
+            Ok(items) => {
+                client.items = items;
+                client.rebuild_transcript(rsc);
+            }
+            Err(message) => {
+                client.show_message(rsc, &format!("Couldn't fold the bench fixture: {message}"))
+            }
+        }
+        client
+    }
+
+    fn platform_ready(&mut self, _rsc: &mut AndroidRsc<Self>, vm: JavaVM, view: GlobalRef) {
+        self.platform = Some(Arc::new(PlatformHandle::new(vm, view)));
+    }
+
+    fn back_pressed(&mut self, _rsc: &mut AndroidRsc<Self>, _render: &mut UiRenderState) -> bool {
+        false
+    }
+
+    /// Pads the top button row by the status-bar inset -- see `top_bar`'s
+    /// field comment. Rebuilds the row rather than mutating a stored
+    /// `Padding` in place, since nothing here holds a handle to one --
+    /// but **only when `insets.top` actually changed**: this callback
+    /// also fires on every `ime_bottom` change (the keyboard sliding
+    /// in/out fires several intermediate insets updates), which has
+    /// nothing to do with the status bar, and rebuilding on every one of
+    /// those was the root cause of a real bug (found on Iris's phone,
+    /// RUST.md's P0 box): each rebuild drops the old `top_bar` content
+    /// and marks the *widget itself* dirty (`Widgets::get_dyn_mut`'s
+    /// `needs_redraw.insert`), which redraws it in place at its last
+    /// known slot -- independently of the *parent* `Span`'s own
+    /// resize-triggered redraw, which redraws the whole row again from
+    /// its two-phase placement (`Span::draw`'s doc: a provisional
+    /// full-region draw, then a real one). A `.set()` landing between
+    /// those two phases left one dirty-widget redraw's primitives
+    /// un-freed while the `Span`-driven redraw drew its own copy,
+    /// producing two live copies of the same three buttons in one frame
+    /// -- one at the header's real slot, one wherever `Span`'s
+    /// provisional phase happened to leave it (visibly inside the
+    /// transcript area), each still holding its own working `on(click)`
+    /// handlers, so a tap meant for whatever was under the stray copy
+    /// hit "Run benchmark" instead. Skipping the rebuild when nothing it
+    /// depends on changed removes the repeated `.set()` calls entirely
+    /// -- confirmed fixed by reproducing the exact repro (tap the
+    /// composer, wait for the keyboard) and checking a `ui-trace`
+    /// element listing for exactly one "Run benchmark" afterward.
+    ///
+    /// Also two things downstream of the same `ime_bottom` transition:
+    /// **the keyboard phase's own confirmation signal** (`ime_state`'s
+    /// doc -- the platform's own answer for whether the IME actually
+    /// opened or closed, rather than assumed from having called
+    /// `show_ime`/`hide_ime`), and **the trigger for the keyboard
+    /// diagnostics capture** (RUST.md's P0 box): the IME resizing the
+    /// surface is exactly the case a previous commit found wiped text,
+    /// and Iris needs a way to get a report off the phone even if that
+    /// (or some other keyboard-triggered regression) is still happening
+    /// on the build she is holding -- `capture_keyboard_diagnostics`
+    /// below fires ~500ms after the keyboard becomes visible, once per
+    /// keyboard opening, and shows its report in a plain overlay view
+    /// that draws independently of whatever iris itself is doing.
+    fn on_insets_changed(
+        &mut self,
+        rsc: &mut AndroidRsc<Self>,
+        insets: iris::android::WindowInsets,
+    ) {
+        if insets.top != self.last_top_pad {
+            self.last_top_pad = insets.top;
+            let controls = bench_controls(rsc, insets.top);
+            (self.top_bar)(rsc).set(controls);
+        }
+
+        let ime_visible = insets.ime_bottom > 0.0;
+
+        let mut ime = self.ime_state.lock().unwrap();
+        if ime_visible && !ime.visible {
+            ime.shown_events += 1;
+        }
+        if !ime_visible && ime.visible {
+            ime.hidden_events += 1;
+        }
+        ime.visible = ime_visible;
+        drop(ime);
+
+        if ime_visible && !self.keyboard_was_visible {
+            self.keyboard_was_visible = true;
+            let redraw = rsc.tasks.redraw_handle();
+            rsc.spawn_task(async move |mut ctx| {
+                tokio::time::sleep(Duration::from_millis(KEYBOARD_DIAGNOSTICS_DELAY_MS)).await;
+                ctx.update(|state: &mut BenchClient, rsc| {
+                    state.capture_keyboard_diagnostics(rsc);
+                });
+                redraw.request_redraw();
+            });
+        } else if !ime_visible {
+            self.keyboard_was_visible = false;
+        }
+    }
+}
+
+/// How long to wait after the keyboard becomes visible before capturing
+/// diagnostics -- long enough that the resize, the reported wipe (if it is
+/// still happening) and a couple of frames have all had time to land, per
+/// AGENTS.md's "so that operations that finish in milliseconds have states
+/// on the way that nothing can observe" reasoning applied the other way:
+/// this wants to observe the state *after* the transition settles, not
+/// mid-flight.
+const KEYBOARD_DIAGNOSTICS_DELAY_MS: u64 = 500;
+
+type Rsc = AndroidRsc<BenchClient>;
+
+/// The header row's own backdrop -- see `bench_controls`'s doc comment on
+/// why it needs one at all. A dark neutral rather than pure black
+/// (`android::render::CLEAR_COLOR`) so the row reads as a distinct panel
+/// instead of a hole in the background the buttons happen to float in.
+const HEADER_SURFACE: UiColor = UiColor::new(28, 28, 34, 255);
+
+/// `top_pad` is the status-bar inset in physical pixels (0.0 until
+/// `on_insets_changed` has run once) -- folded in here, rather than
+/// exposing the unadded builder for a caller to `.pad()` itself, because
+/// naming that builder's type at each call site is more machinery than a
+/// top-of-screen padding number is worth.
+///
+/// **Backed by an opaque rect the full size of the row, not just the three
+/// buttons.** Iris's phone report (docs/RUST.md's P0 box, screenshots on
+/// build a9232ac): "the header buttons have nothing behind them and
+/// overlap the transcript text" -- before this, only each button's own
+/// `rect(...)` painted anything, so the gaps between and around them (and
+/// the status-bar strip above them) showed whatever was one layer back
+/// (`CLEAR_COLOR`, black), and the row's true height was three
+/// physical-pixel-sized (`abs`, not `dp`) button boxes rather than the
+/// density-correct size the transcript below was already using post-P0 --
+/// exactly what reads as "overlap" once the two disagree. Fixed two ways
+/// together: a `HEADER_SURFACE` rect stacked behind the whole row (this
+/// function), and every size below moved from a bare number (physical
+/// pixels) to `dp(...)` (IRIS_TODO.md's density-independent length unit),
+/// so the row's reserved height in the outer `Span::DOWN`
+/// (`AndroidAppState::new`) matches what is actually painted.
+fn bench_controls(rsc: &mut Rsc, top_pad: f32) -> StrongWidget {
+    let run_rect = rect(Color::rgb(40, 70, 40))
+        .on(
+            CursorSense::click(),
+            |ctx: EventIdCtx<'_, Rsc, _, _>, rsc: &mut Rsc| {
+                ctx.state.start_benchmark(rsc);
+            },
+        )
+        .label("Run benchmark");
+    let run = (
+        run_rect,
+        wtext("Run benchmark").size(18).text_align(Align::CENTER),
+    )
+        .stack()
+        .pad(dp(8))
+        .add(rsc);
+
+    let copy_rect = rect(Color::rgb(50, 50, 60))
+        .on(
+            CursorSense::click(),
+            |ctx: EventIdCtx<'_, Rsc, _, _>, _rsc: &mut Rsc| {
+                ctx.state.copy_report();
+            },
+        )
+        .label("Copy report");
+    let copy = (
+        copy_rect,
+        wtext("Copy report").size(18).text_align(Align::CENTER),
+    )
+        .stack()
+        .pad(dp(8))
+        .add(rsc);
+
+    let diag_rect = rect(Color::rgb(60, 45, 70))
+        .on(
+            CursorSense::click(),
+            |ctx: EventIdCtx<'_, Rsc, _, _>, rsc: &mut Rsc| {
+                ctx.state.show_diagnostics(rsc);
+            },
+        )
+        .label("Diagnostics");
+    let diagnostics = (
+        diag_rect,
+        wtext("Diagnostics").size(18).text_align(Align::CENTER),
+    )
+        .stack()
+        .pad(dp(8))
+        .add(rsc);
+
+    let buttons = (run, copy, diagnostics).span(Dir::RIGHT).add(rsc);
+
+    (rect(HEADER_SURFACE), buttons)
+        .stack()
+        .height(dp(56))
+        .pad(Padding::top(top_pad))
+        .add_strong(rsc)
+        .any()
+}
+
+impl BenchClient {
+    fn show_message(&mut self, rsc: &mut Rsc, message: &str) {
+        let widget = placeholder(rsc, message);
+        (self.content)(rsc).set(widget);
+        self.screen = None;
+    }
+
+    fn rebuild_transcript(&mut self, rsc: &mut Rsc) {
+        let rows = group_tool_runs(&self.items);
+        let (screen, tree) = transcript_ui::build_tree(rsc, rows);
+        (self.content)(rsc).set(tree);
+        self.screen = Some(screen);
+    }
+
+    /// RUST.md's P0 box: "a named `Diagnostics` control ... with 'copy this
+    /// and send it to Iris'." Fills `report_display` (the same TextEdit the
+    /// benchmark report uses) rather than a separate widget, so the
+    /// existing "Copy report" button and clipboard path work on whichever
+    /// text is currently shown -- `last_report` is what `copy_report` reads,
+    /// so it's set here too rather than adding a second copy path.
+    fn show_diagnostics(&mut self, rsc: &mut Rsc) {
+        let font = rsc.ui.text.font_diagnostics();
+        let frame_report = match self.android_state().frame_report.report() {
+            Some(stats) => format!("{stats}"),
+            None => "no frames recorded yet".to_string(),
+        };
+        let report = match &self.android_state().renderer {
+            Some(renderer) => renderer.diagnostics_report(&font, &frame_report),
+            None => "iris diagnostics: no renderer yet (no surface)".to_string(),
+        };
+        self.report_display.edit(rsc).set(&report);
+        self.last_report = Some(report);
+    }
+
+    /// The keyboard's own diagnostics capture -- see `on_insets_changed`'s
+    /// doc comment. Reuses `show_diagnostics`'s exact report (so it is the
+    /// same text the on-screen `Diagnostics` button produces, plus the
+    /// per-frame log `FrameReport` already keeps around the resize --
+    /// `frame_report.report()` above covers "the frames around the
+    /// resize" without a second accounting mechanism), then does three
+    /// things the button does not: logs it (so a `logcat` pull gets it
+    /// even if nothing on screen does), copies it to the clipboard
+    /// unprompted, and shows it in the shell's plain overlay view, which
+    /// draws independently of iris's own renderer -- the whole point,
+    /// since the renderer is exactly what might be in the wiped state
+    /// this exists to report on.
+    fn capture_keyboard_diagnostics(&mut self, rsc: &mut Rsc) {
+        self.show_diagnostics(rsc);
+        let Some(report) = self.last_report.clone() else {
+            return;
+        };
+        log::info!("iris keyboard diagnostics:\n{report}");
+        let Some(platform) = &self.platform else {
+            log::info!("iris keyboard diagnostics: no platform handle, can't reach the shell");
+            return;
+        };
+        if platform.copy_to_clipboard("iris keyboard diagnostics", &report) {
+            log::info!("iris keyboard diagnostics: copied to clipboard");
+        } else {
+            log::info!("iris keyboard diagnostics: clipboard copy failed");
+        }
+        platform.show_diagnostics_overlay(&report);
+    }
+
+    fn copy_report(&mut self) {
+        let Some(report) = &self.last_report else {
+            log::info!("iris bench report: nothing to copy -- run the benchmark first");
+            return;
+        };
+        let Some(platform) = &self.platform else {
+            log::info!("iris bench report: no platform handle, can't reach the clipboard");
+            return;
+        };
+        if platform.copy_to_clipboard("iris bench report", report) {
+            log::info!("iris bench report: copied to clipboard");
+        } else {
+            log::info!("iris bench report: clipboard copy failed");
+        }
+    }
+
+    /// RUST.md's "Benchmark v2": fling, then stream (unchanged from v1),
+    /// then type, then keyboard, then the report -- run in-process for the
+    /// same reason `BenchRun.kt`'s own doc gives (no usable system tracing
+    /// on a real phone, no agent that can drive one).
+    fn start_benchmark(&mut self, rsc: &mut Rsc) {
+        if self.running {
+            log::info!("iris bench report: already running");
+            return;
+        }
+        self.running = true;
+        self.android_state_mut().frame_report.reset();
+        self.report_display.edit(rsc).set("Running benchmark...");
+
+        let redraw = rsc.tasks.redraw_handle();
+        let platform = self.platform.clone();
+        let stream_tail = self.stream_tail.clone();
+        let ime_state = self.ime_state.clone();
+        let refresh_hz = platform
+            .as_ref()
+            .and_then(|p| p.refresh_rate_hz())
+            .unwrap_or(60.0);
+        let cpu_start = process_cpu_ms();
+        let run_started_at = Instant::now();
+
+        rsc.spawn_task(async move |mut ctx| {
+            // The battery sampler runs for the whole run, once a second,
+            // the same cadence `BatterySampler` uses on the Compose side
+            // -- via its own JNI-attached thread, not `ctx.update`, since
+            // a sample needs no widget-tree access.
+            let sampler_done = Arc::new(AtomicBool::new(false));
+            let samples = Arc::new(Mutex::new(Vec::<i32>::new()));
+            let sampler = platform.clone().map(|platform| {
+                let done = sampler_done.clone();
+                let samples = samples.clone();
+                tokio::spawn(async move {
+                    while !done.load(Ordering::Relaxed) {
+                        if let Some(value) = platform.battery_current_ua() {
+                            samples.lock().unwrap().push(value);
+                        }
+                        tokio::time::sleep(Duration::from_secs(1)).await;
+                    }
+                })
+            });
+
+            let travel = run_fling_phase(&mut ctx, &redraw).await;
+            let (sent, total) = run_stream_phase(&mut ctx, &redraw, stream_tail).await;
+            run_type_phase(&mut ctx, &redraw, &platform).await;
+            let keyboard = run_keyboard_phase(&mut ctx, &platform, &ime_state).await;
+
+            sampler_done.store(true, Ordering::Relaxed);
+            if let Some(sampler) = sampler {
+                let _ = sampler.await;
+            }
+            let battery = battery_line(&samples.lock().unwrap());
+            let cpu_line = match (cpu_start, process_cpu_ms()) {
+                (Some(start), Some(end)) => {
+                    format!(
+                        "  process CPU time over this run: {}ms",
+                        end.saturating_sub(start)
+                    )
+                }
+                _ => "  process CPU time over this run: unavailable".to_string(),
+            };
+            let rss_line = match peak_rss_kb() {
+                Some(kb) => format!("  peak RSS: {kb}kB"),
+                None => "  peak RSS: unavailable (/proc/self/status unreadable)".to_string(),
+            };
+            let total_seconds = run_started_at.elapsed().as_secs_f64();
+
+            ctx.update(move |state: &mut BenchClient, rsc| {
+                state.running = false;
+                let now = Instant::now();
+                let phase_lines: String = state
+                    .android_state()
+                    .frame_report
+                    .phase_stats(now, refresh_hz)
+                    .iter()
+                    .map(|p| format!("{p}\n"))
+                    .collect();
+                let per_phase = if phase_lines.is_empty() {
+                    String::new()
+                } else {
+                    format!("per phase:\n{phase_lines}\n")
+                };
+                let frames_block = match state.android_state().frame_report.report() {
+                    Some(stats) => {
+                        let (late, late_pct) =
+                            state.android_state().frame_report.late_at_hz(refresh_hz);
+                        format!(
+                            "frames:\n  {} frames over {:.1}s at {:.0}Hz ({:.1}ms budget)\n  \
+                             late: {late} ({late_pct:.1}%)\n  total  p50 {:.1}ms  p90 {:.1}ms  \
+                             p99 {:.1}ms\n  worst {:.1}ms\n  cpu_p50 {:.1}ms  gpu_wait_p50 {:.1}ms",
+                            stats.total_frames,
+                            total_seconds,
+                            refresh_hz,
+                            1000.0 / refresh_hz as f64,
+                            stats.p50.as_secs_f64() * 1000.0,
+                            stats.p90.as_secs_f64() * 1000.0,
+                            stats.p99.as_secs_f64() * 1000.0,
+                            stats.worst.as_secs_f64() * 1000.0,
+                            stats.cpu_p50.as_secs_f64() * 1000.0,
+                            stats.gpu_wait_p50.as_secs_f64() * 1000.0,
+                        )
+                    }
+                    None => "frames:\n  no frames recorded".to_string(),
+                };
+                let scroll_line = format!(
+                    "  scroll: {LEGACY_CYCLES} cycles ({} swipes, legacy tween), streamed \
+                     {sent}/{total} fixture events",
+                    LEGACY_CYCLES * 4
+                );
+                let fling_line = format!(
+                    "  fling: {FLING_COUNT} flings out + {FLING_COUNT} back at \
+                     {FLING_VELOCITY_PX_S}px/s, travel {travel}"
+                );
+                let type_line = format!(
+                    "  type: {} characters inserted then deleted, one per {TYPE_CHAR_MS}ms",
+                    TYPE_TEXT.chars().count()
+                );
+                let report = format!(
+                    "iris bench report\n{per_phase}{frames_block}\n\nbench:\n{fling_line}\n\
+                     {scroll_line}\n{type_line}\n{keyboard}\n{cpu_line}\n{rss_line}\n{battery}"
+                );
+                log::info!("iris bench report: {report}");
+                state.report_display.edit(rsc).set(&report);
+                state.last_report = Some(report);
+            });
+            redraw.request_redraw();
+        });
+    }
+}
+
+/// Runs `f` against the real `BenchClient`/`Rsc` on the main thread (the
+/// same `ctx.update` every other mutation here goes through) and returns
+/// its result to the caller's async task -- `ctx.update` alone has no way
+/// to hand a value back, since the closure only actually runs once the
+/// next frame callback drains `IrisViewPeer`'s task channel
+/// (`drain_tasks`). **Must call `redraw.request_redraw()` itself, right
+/// after enqueueing** -- `ctx.update` only ever pushes onto a channel;
+/// nothing drains it until something schedules the frame callback that
+/// calls `drain_tasks`, and a caller relying on some *earlier*,
+/// already-in-flight `request_redraw()` to cover a *later* `ctx.update`
+/// deadlocks the moment that earlier callback has already fired and
+/// drained everything queued before this call existed. Cost a real hang
+/// in this file's first version of the fling phase: every loop iteration
+/// after the first sat forever with nothing scheduled to drain it.
+/// Polls rather than assuming one `ANIM_STEP_MS` sleep is enough, since a
+/// slow device's frame callback can lag further than that.
+async fn read_from_state<T, F>(
+    ctx: &mut iris::task::TaskCtx<Rsc>,
+    redraw: &Arc<dyn RequestRedraw>,
+    f: F,
+) -> T
+where
+    T: Send + 'static,
+    F: FnOnce(&mut BenchClient, &mut Rsc) -> T + Send + 'static,
+{
+    let (tx, rx) = std::sync::mpsc::channel();
+    ctx.update(move |state: &mut BenchClient, rsc| {
+        let _ = tx.send(f(state, rsc));
+    });
+    redraw.request_redraw();
+    loop {
+        if let Ok(value) = rx.try_recv() {
+            return value;
+        }
+        tokio::time::sleep(Duration::from_millis(ANIM_STEP_MS)).await;
+    }
+}
+
+/// Phase 1: starting pinned at the newest end, `FLING_COUNT` flings away
+/// from it (toward older messages) through `List::fling`, then
+/// `FLING_COUNT` back. Outward is *negative* in this list's `scroll`
+/// convention (`List::scroll`'s own doc: positive moves *later* content
+/// into view) -- the opposite sign `BenchRun.kt`'s `runFlingPhase` uses,
+/// since `TranscriptList`'s `LazyColumn` and this list define "positive"
+/// the other way around; the two apps' *travel* is still directly
+/// comparable because both report it as a row index + pixel offset, not a
+/// signed distance.
+async fn run_fling_phase(
+    ctx: &mut iris::task::TaskCtx<Rsc>,
+    redraw: &Arc<dyn RequestRedraw>,
+) -> String {
+    ctx.update(|state: &mut BenchClient, _rsc| {
+        state.android_state_mut().frame_report.mark_phase("fling");
+    });
+    ctx.update(|state: &mut BenchClient, rsc| {
+        if let Some(screen) = &state.screen {
+            (screen.list)(rsc).jump_to_end();
+        }
+    });
+    redraw.request_redraw();
+    // Lets the next frame's `repair_anchor` resolve `jump_to_end`'s
+    // `anchor = None` into a real slot before `start` is read.
+    tokio::time::sleep(Duration::from_millis(ANIM_STEP_MS * 2)).await;
+    let start = read_anchor_position(ctx, redraw).await;
+
+    for _ in 0..FLING_COUNT {
+        ctx.update(|state: &mut BenchClient, rsc| {
+            if let Some(screen) = &state.screen {
+                (screen.list)(rsc).fling(-FLING_VELOCITY_PX_S);
+            }
+        });
+        redraw.request_redraw();
+        wait_for_fling_settle(ctx, redraw).await;
+        tokio::time::sleep(Duration::from_millis(FLING_PAUSE_MS)).await;
+    }
+    let outward = read_anchor_position(ctx, redraw).await;
+
+    for _ in 0..FLING_COUNT {
+        ctx.update(|state: &mut BenchClient, rsc| {
+            if let Some(screen) = &state.screen {
+                (screen.list)(rsc).fling(FLING_VELOCITY_PX_S);
+            }
+        });
+        redraw.request_redraw();
+        wait_for_fling_settle(ctx, redraw).await;
+        tokio::time::sleep(Duration::from_millis(FLING_PAUSE_MS)).await;
+    }
+    let end = read_anchor_position(ctx, redraw).await;
+
+    format!("start={start} outward={outward} end={end}")
+}
+
+async fn read_anchor_position(
+    ctx: &mut iris::task::TaskCtx<Rsc>,
+    redraw: &Arc<dyn RequestRedraw>,
+) -> String {
+    read_from_state(ctx, redraw, |state, rsc| match &state.screen {
+        Some(screen) => (screen.list)(rsc).anchor_position_display(),
+        None => "idx=none".to_string(),
+    })
+    .await
+}
+
+/// Ticks the fling forward in ~60Hz steps (the same shape
+/// `run_stream_phase`'s per-event loop and the old `animate_scroll` used)
+/// until it settles or `FLING_SETTLE_CAP_MS` passes -- belt-and-suspenders
+/// the same way `BenchRun.kt`'s own `waitForSettle` is, since a fling's
+/// own spline-decided `duration()` already caps how long it can run.
+async fn wait_for_fling_settle(
+    ctx: &mut iris::task::TaskCtx<Rsc>,
+    redraw: &Arc<dyn RequestRedraw>,
+) {
+    let cap = Duration::from_millis(FLING_SETTLE_CAP_MS);
+    let started = Instant::now();
+    while started.elapsed() < cap {
+        let still_scrolling = read_from_state(ctx, redraw, |state, rsc| match &state.screen {
+            Some(screen) => (screen.list)(rsc).tick_fling(Instant::now()),
+            None => false,
+        })
+        .await;
+        if !still_scrolling {
+            return;
+        }
+        tokio::time::sleep(Duration::from_millis(ANIM_STEP_MS)).await;
+    }
+}
+
+/// Phase 2, unchanged from v1: pinned to the newest end before streaming
+/// starts (matching `stream-bench.sh`'s "Jump to latest" tap), then
+/// `STREAM_EVENTS_PER_SEC * STREAM_SECONDS` fixture events replayed
+/// through the real `fold_event`/`TranscriptScreen::apply` path. Returns
+/// `(sent, total)`.
+async fn run_stream_phase(
+    ctx: &mut iris::task::TaskCtx<Rsc>,
+    redraw: &Arc<dyn RequestRedraw>,
+    stream_tail: Vec<SeqEvent>,
+) -> (usize, usize) {
+    ctx.update(|state: &mut BenchClient, _rsc| {
+        state.android_state_mut().frame_report.mark_phase("stream");
+    });
+    ctx.update(|state: &mut BenchClient, rsc| {
+        if let Some(screen) = &state.screen {
+            (screen.list)(rsc).jump_to_end();
+        }
+    });
+    redraw.request_redraw();
+
+    let total = (STREAM_EVENTS_PER_SEC * STREAM_SECONDS) as usize;
+    let mut sent = 0usize;
+    for event in stream_tail.into_iter().take(total) {
+        ctx.update(move |state: &mut BenchClient, rsc| {
+            let old_items = state.items.clone();
+            state.items = fold_event(&state.items, &event);
+            match &state.screen {
+                Some(screen) => screen.apply(rsc, &old_items, &state.items),
+                None => state.rebuild_transcript(rsc),
+            }
+        });
+        redraw.request_redraw();
+        sent += 1;
+        tokio::time::sleep(Duration::from_millis(1000 / STREAM_EVENTS_PER_SEC)).await;
+    }
+    // Lets the last few deltas land and draw before the next phase starts
+    // -- `BenchRun.kt`'s own closing delay.
+    tokio::time::sleep(Duration::from_millis(300)).await;
+    (sent, total)
+}
+
+/// Phase 3: focuses the real composer, shows the keyboard, then types
+/// `TYPE_TEXT` one character at a time through the composer `TextEdit`'s
+/// real edit path (`set`, the same call a real keystroke's `onValueChange`
+/// makes -- `Composer::build_composer`'s `field`), and deletes it the same
+/// way.
+async fn run_type_phase(
+    ctx: &mut iris::task::TaskCtx<Rsc>,
+    redraw: &Arc<dyn RequestRedraw>,
+    platform: &Option<Arc<PlatformHandle>>,
+) {
+    ctx.update(|state: &mut BenchClient, _rsc| {
+        state.android_state_mut().frame_report.mark_phase("type");
+    });
+    ctx.update(|state: &mut BenchClient, rsc| {
+        if let Some(screen) = &state.screen {
+            (screen.list)(rsc).jump_to_end();
+            state.set_focus(Some(screen.composer.field));
+        }
+    });
+    redraw.request_redraw();
+    if let Some(p) = platform {
+        p.show_ime();
+    }
+    // Lets focus and the keyboard's opening animation land before typing
+    // starts, so the frames this phase records are the wrap/reflow it is
+    // measuring, not the keyboard opening -- `BenchRun.kt`'s own delay.
+    tokio::time::sleep(Duration::from_millis(300)).await;
+
+    let mut typed = String::new();
+    for ch in TYPE_TEXT.chars() {
+        typed.push(ch);
+        let text = typed.clone();
+        ctx.update(move |state: &mut BenchClient, rsc| {
+            if let Some(screen) = &state.screen {
+                screen.composer.field.edit(rsc).set(&text);
+            }
+        });
+        redraw.request_redraw();
+        tokio::time::sleep(Duration::from_millis(TYPE_CHAR_MS)).await;
+    }
+    tokio::time::sleep(Duration::from_millis(200)).await;
+    while !typed.is_empty() {
+        typed.pop();
+        let text = typed.clone();
+        ctx.update(move |state: &mut BenchClient, rsc| {
+            if let Some(screen) = &state.screen {
+                screen.composer.field.edit(rsc).set(&text);
+            }
+        });
+        redraw.request_redraw();
+        tokio::time::sleep(Duration::from_millis(TYPE_CHAR_MS)).await;
+    }
+}
+
+/// Phase 4: `KEYBOARD_CYCLES` show/hide cycles through the shell's own
+/// `InputMethodManager` (`bench_jni.rs`'s `show_ime`/`hide_ime`), each
+/// confirmed by `on_insets_changed`'s real `ime_bottom` transition rather
+/// than assumed from the JNI call having returned -- `ImeState`'s doc.
+/// "keyboard: could not be shown" if the platform never confirms it even
+/// once, per UI_RULES.md ("design the unknown/failed state before the
+/// answer's").
+async fn run_keyboard_phase(
+    ctx: &mut iris::task::TaskCtx<Rsc>,
+    platform: &Option<Arc<PlatformHandle>>,
+    ime_state: &Arc<Mutex<ImeState>>,
+) -> String {
+    ctx.update(|state: &mut BenchClient, _rsc| {
+        state
+            .android_state_mut()
+            .frame_report
+            .mark_phase("keyboard");
+    });
+    let mut shown = 0;
+    let mut hidden = 0;
+    for _ in 0..KEYBOARD_CYCLES {
+        let before_shown = ime_state.lock().unwrap().shown_events;
+        if let Some(p) = platform {
+            p.show_ime();
+        }
+        tokio::time::sleep(Duration::from_millis(KEYBOARD_WAIT_MS)).await;
+        if ime_state.lock().unwrap().shown_events > before_shown {
+            shown += 1;
+        }
+
+        let before_hidden = ime_state.lock().unwrap().hidden_events;
+        if let Some(p) = platform {
+            p.hide_ime();
+        }
+        tokio::time::sleep(Duration::from_millis(KEYBOARD_WAIT_MS)).await;
+        if ime_state.lock().unwrap().hidden_events > before_hidden {
+            hidden += 1;
+        }
+    }
+    if shown == 0 {
+        format!("  keyboard: could not be shown ({KEYBOARD_CYCLES} attempts, 0 confirmed visible)")
+    } else {
+        format!(
+            "  keyboard: shown {shown}/{KEYBOARD_CYCLES}, hidden {hidden}/{KEYBOARD_CYCLES} \
+             (confirmed via on_insets_changed)"
+        )
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::TYPE_TEXT;
+
+    /// `BenchRun.kt`'s own `TYPE_TEXT` is verified `.length == 600`; this
+    /// is the same string, so it has to match exactly or the two apps'
+    /// type phases stop typing the same content -- RUST.md's "Benchmark
+    /// v2" spec is one shared string for both.
+    #[test]
+    fn type_text_is_exactly_600_characters() {
+        assert_eq!(TYPE_TEXT.chars().count(), 600);
+    }
+}

iris/android-app/src/bench_jni.rs

@@ -0,0 +1,252 @@
+//! JNI calls the `bench` feature needs that go through the shell's own
+//! Java side rather than anything `iris`/`android-view` already wraps:
+//! `BatteryManager.getIntProperty(BATTERY_PROPERTY_CURRENT_NOW)` for the
+//! per-second battery sample, `ClipboardManager.setPrimaryClip` for the
+//! "Copy report" control (P0's iris half, docs/RUST.md), and -- added for
+//! RUST.md's "Benchmark v2" -- `Display.getRefreshRate()` for the phase
+//! report's real late-frame budget and `InputMethodManager.
+//! showSoftInput`/`hideSoftInputFromWindow` for the keyboard phase. None
+//! of these are part of `android_view::context`'s own `Context`/
+//! `Resources` wrappers (that file's own `// TODO: more methods?`), so
+//! this calls them directly rather than growing that crate's wrapper for
+//! calls this crate alone needs.
+//!
+//! Holds its own `JavaVM` + `GlobalRef` to the view (handed in through
+//! [`iris::android::AndroidAppState::platform_ready`]) so it can attach
+//! whichever thread calls it -- the battery sampler runs on a background
+//! tokio task, not the UI thread the rest of `IrisViewPeer`'s JNI calls
+//! run on. `JavaVM::attach_current_thread` is safe to call from a thread
+//! already attached (the `jni` crate detects it and does not double
+//! attach), so no caller here needs to know or care which thread it is.
+
+use android_view::jni::{
+    JNIEnv, JavaVM,
+    objects::{GlobalRef, JObject, JValue},
+};
+
+/// `android.os.BatteryManager.BATTERY_PROPERTY_CURRENT_NOW` -- not exposed
+/// as a constant anywhere reachable without the Android SDK jar, so named
+/// here with its source rather than left as a bare `2`.
+const BATTERY_PROPERTY_CURRENT_NOW: i32 = 2;
+
+pub struct PlatformHandle {
+    vm: JavaVM,
+    view: GlobalRef,
+}
+
+impl PlatformHandle {
+    pub fn new(vm: JavaVM, view: GlobalRef) -> Self {
+        Self { vm, view }
+    }
+
+    fn context<'e>(&self, env: &mut JNIEnv<'e>) -> Option<JObject<'e>> {
+        env.call_method(
+            self.view.as_obj(),
+            "getContext",
+            "()Landroid/content/Context;",
+            &[],
+        )
+        .ok()?
+        .l()
+        .ok()
+    }
+
+    fn system_service<'e>(
+        &self,
+        env: &mut JNIEnv<'e>,
+        context: &JObject<'e>,
+        name: &str,
+    ) -> Option<JObject<'e>> {
+        let jname = env.new_string(name).ok()?;
+        env.call_method(
+            context,
+            "getSystemService",
+            "(Ljava/lang/String;)Ljava/lang/Object;",
+            &[JValue::Object(jname.as_ref())],
+        )
+        .ok()?
+        .l()
+        .ok()
+    }
+
+    /// One sample of `BATTERY_PROPERTY_CURRENT_NOW`, in microamps. `None`
+    /// on any JNI failure, on a device with no `BatteryManager` service,
+    /// or when the platform itself answers "not supported" -- `0` or
+    /// `Integer.MIN_VALUE` are both documented SDK answers for that, and
+    /// both would read as a real (and wrong) measurement if folded into an
+    /// average rather than named apart. UI_RULES.md: never present an
+    /// inferred value as a measured one.
+    pub fn battery_current_ua(&self) -> Option<i32> {
+        let mut guard = self.vm.attach_current_thread().ok()?;
+        let env: &mut JNIEnv = &mut guard;
+        let context = self.context(env)?;
+        let battery_manager = self.system_service(env, &context, "batterymanager")?;
+        let value = env
+            .call_method(
+                &battery_manager,
+                "getIntProperty",
+                "(I)I",
+                &[JValue::Int(BATTERY_PROPERTY_CURRENT_NOW)],
+            )
+            .ok()?
+            .i()
+            .ok()?;
+        if value == 0 || value == i32::MIN {
+            None
+        } else {
+            Some(value)
+        }
+    }
+
+    /// Puts `text` on the system clipboard through `ClipboardManager` --
+    /// `true` only if the whole JNI chain (service lookup, `ClipData`,
+    /// `setPrimaryClip`) succeeded.
+    pub fn copy_to_clipboard(&self, label: &str, text: &str) -> bool {
+        self.try_copy_to_clipboard(label, text).is_some()
+    }
+
+    fn try_copy_to_clipboard(&self, label: &str, text: &str) -> Option<()> {
+        let mut guard = self.vm.attach_current_thread().ok()?;
+        let env: &mut JNIEnv = &mut guard;
+        let context = self.context(env)?;
+        let clipboard = self.system_service(env, &context, "clipboard")?;
+        let jlabel = env.new_string(label).ok()?;
+        let jtext = env.new_string(text).ok()?;
+        let clip = env
+            .call_static_method(
+                "android/content/ClipData",
+                "newPlainText",
+                "(Ljava/lang/CharSequence;Ljava/lang/CharSequence;)Landroid/content/ClipData;",
+                &[
+                    JValue::Object(jlabel.as_ref()),
+                    JValue::Object(jtext.as_ref()),
+                ],
+            )
+            .ok()?
+            .l()
+            .ok()?;
+        env.call_method(
+            &clipboard,
+            "setPrimaryClip",
+            "(Landroid/content/ClipData;)V",
+            &[JValue::Object(&clip)],
+        )
+        .ok()?;
+        Some(())
+    }
+
+    /// The display's own refresh rate in Hz (`View::getDisplay()` ->
+    /// `Display::getRefreshRate()`), for RUST.md's "Benchmark v2": late
+    /// frames are judged against *this* device's real budget, not an
+    /// assumed 60Hz -- a 90Hz or 120Hz phone would otherwise call frames
+    /// "late" that met their own faster deadline. `None` if the view is
+    /// not yet attached to a window (`getDisplay` returns `null`) or the
+    /// platform reports a non-positive rate, which is not a real answer
+    /// either.
+    pub fn refresh_rate_hz(&self) -> Option<f32> {
+        let mut guard = self.vm.attach_current_thread().ok()?;
+        let env: &mut JNIEnv = &mut guard;
+        let display = env
+            .call_method(
+                self.view.as_obj(),
+                "getDisplay",
+                "()Landroid/view/Display;",
+                &[],
+            )
+            .ok()?
+            .l()
+            .ok()?;
+        if display.is_null() {
+            return None;
+        }
+        let rate = env
+            .call_method(&display, "getRefreshRate", "()F", &[])
+            .ok()?
+            .f()
+            .ok()?;
+        if rate > 0.0 { Some(rate) } else { None }
+    }
+
+    /// `InputMethodManager.showSoftInput(view, 0)` -- the keyboard phase's
+    /// own show, called directly rather than through the focus-driven
+    /// `pending_show_keyboard` path `android/view.rs` uses for a real tap,
+    /// since RUST.md's "Benchmark v2" spec asks for this "through the
+    /// shell's InputMethodManager" independent of focus state. `true` only
+    /// if the platform itself reports the request succeeded -- whether the
+    /// IME actually became visible is confirmed separately, from
+    /// `on_insets_changed`, per UI_RULES.md ("never present an inferred
+    /// value as a measured one").
+    pub fn show_ime(&self) -> bool {
+        self.try_toggle_ime(true).unwrap_or(false)
+    }
+
+    /// `InputMethodManager.hideSoftInputFromWindow(windowToken, 0)`.
+    pub fn hide_ime(&self) -> bool {
+        self.try_toggle_ime(false).unwrap_or(false)
+    }
+
+    fn try_toggle_ime(&self, show: bool) -> Option<bool> {
+        let mut guard = self.vm.attach_current_thread().ok()?;
+        let env: &mut JNIEnv = &mut guard;
+        let context = self.context(env)?;
+        let imm = self.system_service(env, &context, "input_method")?;
+        if show {
+            env.call_method(
+                &imm,
+                "showSoftInput",
+                "(Landroid/view/View;I)Z",
+                &[JValue::Object(self.view.as_obj()), JValue::Int(0)],
+            )
+            .ok()?
+            .z()
+            .ok()
+        } else {
+            let token = env
+                .call_method(
+                    self.view.as_obj(),
+                    "getWindowToken",
+                    "()Landroid/os/IBinder;",
+                    &[],
+                )
+                .ok()?
+                .l()
+                .ok()?;
+            env.call_method(
+                &imm,
+                "hideSoftInputFromWindow",
+                "(Landroid/os/IBinder;I)Z",
+                &[JValue::Object(&token), JValue::Int(0)],
+            )
+            .ok()?
+            .z()
+            .ok()
+        }
+    }
+
+    /// Shows `report` in the shell's plain-view diagnostics overlay
+    /// (`IrisView.showDiagnosticsOverlay`) -- a real `TextView` plus Copy
+    /// and Close controls, added over whatever iris itself is drawing
+    /// rather than replacing it (unlike `android::view::show_renderer_error`,
+    /// which exists for the case the renderer can never recover from and
+    /// intentionally never returns). Called from a background task after
+    /// the keyboard-open delay (`bench_client.rs`'s `on_insets_changed`),
+    /// so the Java side hops onto the UI thread itself before touching the
+    /// view tree -- see that method's own comment.
+    pub fn show_diagnostics_overlay(&self, report: &str) -> bool {
+        self.try_show_diagnostics_overlay(report).is_some()
+    }
+
+    fn try_show_diagnostics_overlay(&self, report: &str) -> Option<()> {
+        let mut guard = self.vm.attach_current_thread().ok()?;
+        let env: &mut JNIEnv = &mut guard;
+        let jreport = env.new_string(report).ok()?;
+        env.call_method(
+            self.view.as_obj(),
+            "showDiagnosticsOverlay",
+            "(Ljava/lang/String;)V",
+            &[JValue::Object(jreport.as_ref())],
+        )
+        .ok()?;
+        Some(())
+    }
+}

iris/android-app/src/lib.rs

@@ -1,5 +1,5 @@
-//! The android-view demo app: iris's `tabs` widget tree (`tabs_ui::build`,
-//! shared with the winit example) running through
+//! The android-view demo app: by default, iris's `tabs` widget tree
+//! (`tabs_ui::build`, shared with the winit example) running through
 //! `iris::android`'s `ViewPeer`. This is RUST.md's I2 pass condition made
 //! concrete -- there is no UI here beyond what `tabs-ui` already draws.
 //!
@@ -9,6 +9,32 @@
 //! wrapping `iris::android::new_peer`'s generic function in a concrete
 //! `extern "system" fn`, since `register_view_class` wants a plain
 //! function pointer.
+//!
+//! **`transcript-screen` feature (RUST.md's I5 Android integration):** with
+//! `--features transcript-screen`, `new_view_peer` instantiates
+//! `transcript_client::TranscriptClient` instead of the tabs `Client`
+//! below, against a real `ai-server` (see that module's doc). Chosen over a
+//! third shell crate: this one already has the Gradle project, the
+//! `IrisView`/`MainActivity` Java, and the JNI registration I2 built and
+//! measured against, and the only thing a transcript screen needs on top
+//! is a different `AndroidAppState` -- the same axis `tabs_ui::build` vs.
+//! `transcript_ui::build` already varies along on the winit side (compare
+//! `iris/examples/tabs.rs` and `iris/transcript-ui/examples/transcript.rs`).
+//! A build picks one screen or the other, never both, so `Client` and
+//! `TranscriptClient` are cfg-gated apart rather than switched at runtime --
+//! there is no in-app navigation to switch *to* on either side yet.
+//!
+//! **`bench` feature (P0's iris half, docs/RUST.md):** a third
+//! `AndroidAppState`, `bench_client::BenchClient`, on the same axis --
+//! `transcript_ui::build_tree` again, this time against the checked-in
+//! fixture (`app/bench-fixture/assets/transcript.jsonl`) instead of a real
+//! server, with a "Run benchmark" control that drives the same scroll loop
+//! and streaming phase the Compose `bench` build type's `BenchRun.kt`
+//! does. `bench` depends on `transcript-screen` (Cargo.toml) for
+//! `transcript-ui`/`client-core`/`event-model`, so both features end up
+//! enabled together -- `ActiveClient` below gives `bench` priority in that
+//! case, the same way `transcript-screen` already takes priority over the
+//! default `tabs-screen`.
 
 use android_view::{
     Context, View,
@@ -18,19 +44,30 @@ use android_view::{
     },
     register_view_class,
 };
+#[cfg(not(feature = "transcript-screen"))]
 use iris::android::{AndroidAppState, AndroidRsc, AndroidUiState, HasAndroidUiState};
+#[cfg(not(feature = "transcript-screen"))]
 use iris::prelude::*;
 use log::LevelFilter;
 use std::ffi::c_void;
 
+#[cfg(feature = "bench")]
+mod bench_client;
+#[cfg(feature = "bench")]
+mod bench_jni;
+#[cfg(all(feature = "transcript-screen", not(feature = "bench")))]
+mod transcript_client;
+
 /// The app's `View` subclass, matching the Java side's package --
 /// `app/src/main/java/dev/iris/android/demo/IrisView.java`.
 const VIEW_CLASS: &str = "dev/iris/android/demo/IrisView";
 
+#[cfg(not(feature = "transcript-screen"))]
 pub struct Client {
     ui_state: AndroidUiState,
 }
 
+#[cfg(not(feature = "transcript-screen"))]
 impl HasAndroidUiState for Client {
     fn android_state(&self) -> &AndroidUiState {
         &self.ui_state
@@ -40,6 +77,7 @@ impl HasAndroidUiState for Client {
     }
 }
 
+#[cfg(not(feature = "transcript-screen"))]
 impl AndroidAppState for Client {
     fn new(mut ui_state: AndroidUiState, rsc: &mut AndroidRsc<Self>) -> Self {
         // `widgets.info` is the winit example's frame-debug readout, kept
@@ -61,12 +99,19 @@ impl AndroidAppState for Client {
     }
 }
 
+#[cfg(not(feature = "transcript-screen"))]
+type ActiveClient = Client;
+#[cfg(all(feature = "transcript-screen", not(feature = "bench")))]
+type ActiveClient = transcript_client::TranscriptClient;
+#[cfg(feature = "bench")]
+type ActiveClient = bench_client::BenchClient;
+
 extern "system" fn new_view_peer<'local>(
     env: JNIEnv<'local>,
     view: View<'local>,
     context: Context<'local>,
 ) -> jlong {
-    iris::android::new_peer::<Client>(env, view, context)
+    iris::android::new_peer::<ActiveClient>(env, view, context)
 }
 
 /// # Safety

iris/android-app/src/transcript_client.rs

@@ -0,0 +1,392 @@
+//! RUST.md's I5 Android integration: `transcript-ui`'s screen filling the
+//! whole window on android-view, against a real `ai-server` through
+//! `client-core` -- the missing half `iris-android-app` (I2) only had for
+//! `tabs-ui` until now. Behind the `transcript-screen` Cargo feature so the
+//! plain build (`cargo ndk build`, no `--features`) stays exactly the tabs
+//! demo I2/I4 already measured against.
+//!
+//! **Deliberate simplification, recorded rather than left to be
+//! rediscovered (RUST.md's I5 box has the full account)**: there is no
+//! session list and no enrollment UI here. The server, port, token and
+//! pinned CA are baked in at build time (`build.rs`'s
+//! `AI_APP_TRANSCRIPT_HOST`/`_PORT`/`_TOKEN`/`AI_APP_CA`), and the first
+//! session `ApiClient::fetch_sessions` returns is opened automatically --
+//! there is nothing to tap to get there, which is what `transcript-bench.sh`
+//! and `ui-trace` need to land straight on the screen under test. A real
+//! app needs `desktop-app`'s `EnrolledServer`/QR-link flow or E3's
+//! Keystore-sealed `ServerConfig.kt`; building a second one of those was
+//! not this pass's job.
+//!
+//! **Reuses `iris/desktop-app`'s `app.rs` shape almost exactly** --
+//! `fold_event`/`group_tool_runs`/`fold_page`/`raw_seq` from
+//! `client_core::transcript_fold`, a `generation` counter guarding against
+//! a stale background response. What differs is only the redraw
+//! mechanism: android-view has no `winit::EventLoopProxy`, so this uses
+//! `iris::task::Tasks::redraw_handle` (new, added alongside this box) to
+//! request a frame after each `TaskCtx::update` instead of relying on
+//! `Tasks::spawn`'s single end-of-future redraw -- see that method's own
+//! doc for why.
+//!
+//! **Streaming no longer costs a full rebuild** (fixed after the P0 gate
+//! showed why it mattered -- 20 events/second means 20 rebuilds/second of
+//! a ~3,200-row transcript otherwise): `apply_event` calls
+//! `transcript_ui::TranscriptScreen::apply` with the item list before and
+//! after `fold_event`, which updates only the row(s) that actually
+//! changed (almost always just the one open assistant message) instead of
+//! refolding and rebuilding every row. `rebuild_transcript` still runs
+//! the whole widget tree once, for the opening page and for `apply`'s own
+//! rare regroup fallback.
+
+use client_core::api::{ApiClient, UreqTransport};
+use client_core::event_stream::{StreamItem, follow_session_events};
+use client_core::transcript_fold::{TranscriptItem, fold_event, fold_page, group_tool_runs};
+use event_model::SeqEvent;
+use iris::android::{AndroidAppState, AndroidRsc, AndroidUiState, HasAndroidUiState};
+use iris::prelude::*;
+use std::sync::Arc;
+use std::sync::atomic::{AtomicU64, Ordering};
+
+mod pinned {
+    include!(concat!(env!("OUT_DIR"), "/pinned_config.rs"));
+}
+
+pub struct TranscriptClient {
+    ui_state: AndroidUiState,
+    /// The screen's own content -- everything under the fixed
+    /// [`frame_report_controls`] bar, which is built once (`new`, below)
+    /// and never touched by `show_message`/`rebuild_transcript`'s own
+    /// `set` calls the way `desktop-app`'s `transcript_ptr` isn't touched
+    /// by rebuilding the session list beside it.
+    content: WeakWidget<WidgetPtr>,
+    screen: Option<transcript_ui::TranscriptScreen>,
+    /// The folded transcript as of the last rebuild -- kept here (not
+    /// re-derived) for the same reason `desktop-app`'s `Client::items`
+    /// exists: a live `StreamEvent` only carries one new wire event, and
+    /// `fold_event` needs everything folded so far to fold it in.
+    items: Vec<TranscriptItem>,
+    /// The session currently open -- `None` only before the first fetch
+    /// resolves. Read back by `apply_event`'s rebuild, which has no session
+    /// id of its own (a live `SeqEvent` doesn't carry one).
+    session_id: Option<String>,
+    /// Bumped every time a new session load starts; a background response
+    /// checks it before touching state, so a slow reply for a session this
+    /// screen has moved on from can't overwrite what replaced it. There is
+    /// only ever one session here (no list to switch away to), but the
+    /// guard still matters for the *first* fetch racing a `stop`/`start`.
+    generation: Arc<AtomicU64>,
+}
+
+impl HasAndroidUiState for TranscriptClient {
+    fn android_state(&self) -> &AndroidUiState {
+        &self.ui_state
+    }
+    fn android_state_mut(&mut self) -> &mut AndroidUiState {
+        &mut self.ui_state
+    }
+}
+
+/// Builds one `UreqTransport` from the config `build.rs` baked in. Called
+/// twice per session load, same as `desktop-app`'s `build_transport`
+/// closure -- `ApiClient` and the live-stream follow each need their own,
+/// since `UreqTransport` holds its own `ureq::Agent`.
+fn build_transport() -> Result<UreqTransport, String> {
+    let base_url = format!("https://{}:{}", pinned::HOST, pinned::PORT);
+    UreqTransport::new(
+        base_url,
+        pinned::TOKEN.to_string(),
+        pinned::CA_PEM.as_bytes(),
+    )
+    .map_err(|e| e.to_string())
+}
+
+fn placeholder<Rsc: HasEvents>(rsc: &mut Rsc, message: &str) -> StrongWidget {
+    wtext(message.to_string())
+        .color(Color::WHITE)
+        .wrap(true)
+        .pad(16)
+        .add_strong(rsc)
+        .any()
+}
+
+/// The two named controls RUST.md's I5 box ("Measurements taken" (b))
+/// drives by name over `ui-trace`, e.g. `ui-trace record --do "tap 'Frame
+/// report'"`. `dumpsys gfxinfo` cannot see this screen's own GPU-drawn
+/// frames at all -- this is the screen's own equivalent of the Compose
+/// app's "Copy render timings" control, logged rather than clipboarded
+/// (no clipboard wiring exists here) under this crate's own fixed
+/// `android_logger` tag (`iris-android-app`, `lib.rs`'s `JNI_OnLoad`),
+/// grep-able on the fixed string `"iris frame report"` the way
+/// `transcript-bench.sh` greps `"ai-app render report"`.
+fn frame_report_controls(rsc: &mut AndroidRsc<TranscriptClient>) -> WeakWidget {
+    type Rsc = AndroidRsc<TranscriptClient>;
+    let report_rect = rect(Color::rgb(50, 50, 60))
+        .on(
+            CursorSense::click(),
+            |ctx: EventIdCtx<'_, Rsc, _, _>, _rsc: &mut Rsc| match ctx
+                .state
+                .android_state()
+                .frame_report
+                .report()
+            {
+                Some(stats) => log::info!("iris frame report: {stats}"),
+                None => log::info!(
+                    "iris frame report: no frames recorded -- scroll first, then press this"
+                ),
+            },
+        )
+        .label("Frame report");
+    let report = (
+        report_rect,
+        wtext("Frame report").size(18).text_align(Align::CENTER),
+    )
+        .stack()
+        .pad(8)
+        .add(rsc);
+
+    let reset_rect = rect(Color::rgb(70, 40, 40))
+        .on(
+            CursorSense::click(),
+            |ctx: EventIdCtx<'_, Rsc, _, _>, _rsc: &mut Rsc| {
+                ctx.state.android_state_mut().frame_report.reset();
+                log::info!("iris frame report: reset");
+            },
+        )
+        .label("Reset frame report");
+    let reset = (
+        reset_rect,
+        wtext("Reset").size(18).text_align(Align::CENTER),
+    )
+        .stack()
+        .pad(8)
+        .add(rsc);
+
+    (report, reset).span(Dir::RIGHT).height(56).add(rsc)
+}
+
+impl AndroidAppState for TranscriptClient {
+    fn new(mut ui_state: AndroidUiState, rsc: &mut AndroidRsc<Self>) -> Self {
+        let content = WidgetPtr::new().add(rsc);
+        let loading = placeholder(rsc, "Loading sessions...");
+        content(rsc).set(loading);
+
+        let tree = (frame_report_controls(rsc), content.height(rest(1)))
+            .span(Dir::DOWN)
+            .add_strong(rsc)
+            .any();
+        ui_state.set_root(tree);
+
+        let mut client = Self {
+            ui_state,
+            content,
+            screen: None,
+            items: Vec::new(),
+            session_id: None,
+            generation: Arc::new(AtomicU64::new(0)),
+        };
+        client.spawn_fetch_sessions(rsc);
+        client
+    }
+
+    fn back_pressed(&mut self, _rsc: &mut AndroidRsc<Self>, _render: &mut UiRenderState) -> bool {
+        // No screen stack of its own -- same "let the activity finish"
+        // answer `iris-android-app`'s tabs `Client` already gives.
+        false
+    }
+}
+
+impl TranscriptClient {
+    fn show_message(&mut self, rsc: &mut AndroidRsc<Self>, message: &str) {
+        let widget = placeholder(rsc, message);
+        (self.content)(rsc).set(widget);
+        self.screen = None;
+    }
+
+    fn spawn_fetch_sessions(&mut self, rsc: &mut AndroidRsc<Self>) {
+        let redraw = rsc.tasks.redraw_handle();
+        let my_generation = self.generation.load(Ordering::SeqCst);
+        let generation = self.generation.clone();
+        rsc.spawn_task(async move |mut ctx| {
+            let outcome = match build_transport() {
+                Ok(transport) => ApiClient::new(transport)
+                    .fetch_sessions()
+                    .map_err(|e| e.to_string()),
+                Err(e) => Err(format!("couldn't set up TLS: {e}")),
+            };
+            ctx.update(move |state: &mut TranscriptClient, rsc| {
+                if generation.load(Ordering::SeqCst) != my_generation {
+                    return;
+                }
+                match outcome {
+                    Ok(sessions) => match sessions.into_iter().next() {
+                        Some(session) => state.select_session(rsc, session.id),
+                        None => state.show_message(rsc, "No sessions on the sandbox server."),
+                    },
+                    Err(message) => {
+                        state.show_message(rsc, &format!("Couldn't list sessions: {message}"))
+                    }
+                }
+            });
+            redraw.request_redraw();
+        });
+    }
+
+    /// Loads the opening page, then follows the live SSE stream for the
+    /// rest of this session's life -- `desktop-app`'s `select_session`
+    /// almost verbatim, with `Proxy::send_event` replaced by `ctx.update` +
+    /// `redraw.request_redraw()` (see this module's doc).
+    fn select_session(&mut self, rsc: &mut AndroidRsc<Self>, session_id: String) {
+        let my_generation = self.generation.fetch_add(1, Ordering::SeqCst) + 1;
+        self.items.clear();
+        self.session_id = Some(session_id.clone());
+        self.show_message(rsc, "Loading transcript...");
+
+        let redraw = rsc.tasks.redraw_handle();
+        let live_generation = self.generation.clone();
+        rsc.spawn_task(async move |mut ctx| {
+            let transports =
+                build_transport().and_then(|rest| build_transport().map(|stream| (rest, stream)));
+            let (rest, stream_transport) = match transports {
+                Ok(pair) => pair,
+                Err(e) => {
+                    let message = format!("couldn't set up TLS: {e}");
+                    ctx.update(move |state: &mut TranscriptClient, rsc| {
+                        if live_generation.load(Ordering::SeqCst) == my_generation {
+                            state.show_message(rsc, &message);
+                        }
+                    });
+                    redraw.request_redraw();
+                    return;
+                }
+            };
+            let api = ApiClient::new(rest);
+
+            // The most recent 200 events, coalesced -- the same page size
+            // `desktop-app` uses; RUST.md's I3/history-paging work is what
+            // a real scrollback would reuse (out of scope here, same as
+            // E4).
+            let page: Result<Vec<serde_json::Value>, String> = api
+                .fetch_transcript_page(&session_id, None, 200, true)
+                .map_err(|e| e.to_string());
+            // The wire `seq` of the last line, not a folded item's `seq()`
+            // -- see `client_core::transcript_fold::raw_seq`'s doc for why
+            // resuming from the latter re-delivers deltas already folded
+            // into an in-progress reply.
+            let after = page
+                .as_ref()
+                .ok()
+                .and_then(|values| values.last())
+                .and_then(client_core::transcript_fold::raw_seq)
+                .unwrap_or(0);
+            let result = page.and_then(|values| fold_page(&values));
+
+            {
+                let live_generation = live_generation.clone();
+                ctx.update(move |state: &mut TranscriptClient, rsc| {
+                    if live_generation.load(Ordering::SeqCst) != my_generation {
+                        return;
+                    }
+                    match result {
+                        Ok(items) => {
+                            state.items = items;
+                            state.rebuild_transcript(rsc);
+                        }
+                        Err(message) => {
+                            state.show_message(rsc, &format!("Couldn't load transcript: {message}"))
+                        }
+                    }
+                });
+            }
+            redraw.request_redraw();
+
+            if live_generation.load(Ordering::SeqCst) != my_generation {
+                return;
+            }
+            // The outer closure here is an `FnMut` -- `follow_session_events`
+            // calls it once per line -- so it captures `live_generation` by
+            // move and re-clones it for each inner `ctx.update` closure
+            // rather than moving a shared `stop`-style helper into itself:
+            // a value moved out of an `FnMut`'s captures on one call leaves
+            // nothing there for the next.
+            let _ =
+                follow_session_events(
+                    &stream_transport,
+                    &session_id,
+                    after,
+                    move |item| match item {
+                        StreamItem::Open | StreamItem::Reset => {
+                            live_generation.load(Ordering::SeqCst) == my_generation
+                        }
+                        StreamItem::Event { event, .. } => {
+                            if live_generation.load(Ordering::SeqCst) != my_generation {
+                                return false;
+                            }
+                            let live_generation = live_generation.clone();
+                            ctx.update(move |state: &mut TranscriptClient, rsc| {
+                                if live_generation.load(Ordering::SeqCst) != my_generation {
+                                    return;
+                                }
+                                state.apply_event(rsc, &event);
+                            });
+                            redraw.request_redraw();
+                            true
+                        }
+                    },
+                );
+        });
+    }
+
+    /// Rebuilds the whole widget tree from `self.items` -- same tradeoff as
+    /// `desktop-app`'s `rebuild_transcript` (this module's doc comment).
+    /// Reads `self.session_id` rather than taking one, since every caller
+    /// (the opening page, and every live event) already has it set there.
+    fn rebuild_transcript(&mut self, rsc: &mut AndroidRsc<Self>) {
+        let in_progress = self
+            .screen
+            .as_ref()
+            .map(|screen| screen.composer.field.edit(rsc).text.text().to_string())
+            .filter(|t| !t.is_empty());
+
+        let rows = group_tool_runs(&self.items);
+        let (screen, tree) = transcript_ui::build_tree(rsc, rows);
+
+        if let Some(text) = in_progress {
+            screen.composer.field.edit(rsc).set(&text);
+        }
+        if let Some(session_id) = self.session_id.clone() {
+            let field = screen.composer.field;
+            rsc.register_event(field, Submit, move |ctx, rsc| {
+                let text = field.edit(rsc).take();
+                let text = text.trim().to_string();
+                if !text.is_empty() {
+                    ctx.state.send_message(session_id.clone(), text);
+                }
+            });
+        }
+
+        (self.content)(rsc).set(tree);
+        self.screen = Some(screen);
+    }
+
+    fn apply_event(&mut self, rsc: &mut AndroidRsc<Self>, event: &SeqEvent) {
+        let old_items = self.items.clone();
+        self.items = fold_event(&self.items, event);
+        match &self.screen {
+            // The common path: update only the row(s) that actually
+            // changed instead of refolding and rebuilding all ~3,200 of
+            // them per event (RUST.md's P0 streaming-phase fix).
+            Some(screen) => screen.apply(rsc, &old_items, &self.items),
+            // No screen yet (the opening page hasn't landed) -- build one
+            // the ordinary way once it has.
+            None => self.rebuild_transcript(rsc),
+        }
+    }
+
+    fn send_message(&mut self, session_id: String, text: String) {
+        std::thread::spawn(move || {
+            if let Ok(transport) = build_transport() {
+                let api = ApiClient::new(transport);
+                let _ = api.send_message(&session_id, &text, &[]);
+            }
+        });
+    }
+}

iris/core/Cargo.toml

@@ -5,6 +5,12 @@ edition.workspace = true
 
 [dependencies]
 wgpu = { workspace = true }
+# Only for `UiRenderNode::new`'s `push_error_scope`/`pop_error_scope` pair
+# (renderer-creation error reporting, RUST.md's P0 phone-crash box) --
+# `block_on` turns that one async pop into the same synchronous call shape
+# `device_limits()`'s two callers already use for `request_adapter`/
+# `request_device`, rather than making this crate's one entry point async.
+pollster = { workspace = true }
 bytemuck ={ workspace = true }
 image = { workspace = true }
 parley = { workspace = true }

iris/core/assets/fonts/OFL.txt

@@ -0,0 +1,201 @@
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+
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iris/core/src/orientation/len.rs

@@ -9,7 +9,31 @@ pub struct Size {
 
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub struct Len {
+    /// Physical pixels -- a raw device pixel, unaffected by the display's
+    /// density. Rare to want directly (a hairline border is the usual
+    /// case); most sizes should be `dp` instead. See `dp`'s own doc for why
+    /// the two are kept separate rather than one field a caller has to
+    /// remember to pre-multiply.
     pub abs: f32,
+    /// Density-independent pixels -- Android's `dp` / CSS's reference pixel
+    /// (1 unit = 1/160in), resolved against the display's density at
+    /// layout time (`apply_rest`'s `density` parameter) rather than at the
+    /// point a widget is built, since density is a property of the device
+    /// this ends up running on, not of the widget tree. This is the unit
+    /// IRIS_TODO.md's "a density-independent length unit" item asked for,
+    /// 2026-09-06: before it existed, every size in the tree was `abs`
+    /// (physical pixels), and the only way to make a 16px design draw at
+    /// the right *size* on a denser display was a single global multiply
+    /// applied to the whole rendered scene after layout -- which is also
+    /// what made text blurry (RUST.md's P0 box, "blurry ... glyphs drawn
+    /// at logical size and stretched by the scale"): a glyph rasterised at
+    /// 16 physical px and then stretched 3x by that global multiply is a
+    /// 48px area sampled from a 16px bitmap. Resolving `dp` per-length at
+    /// layout time instead means the font size handed to the text shaper
+    /// is already the physical size (`16.0.dp() * 3.0`), so the glyph
+    /// atlas rasterises at the display's real resolution and nothing
+    /// downstream needs to stretch anything.
+    pub dp: f32,
     pub rel: f32,
     pub rest: f32,
 }
@@ -67,10 +91,10 @@ impl Size {
         }
     }
 
-    pub fn to_uivec2(self) -> UiVec2 {
+    pub fn to_uivec2(self, density: f32) -> UiVec2 {
         UiVec2 {
-            x: self.x.apply_rest(),
-            y: self.y.apply_rest(),
+            x: self.x.apply_rest(density),
+            y: self.y.apply_rest(density),
         }
     }
 
@@ -98,26 +122,43 @@ impl Size {
 impl Len {
     pub const ZERO: Self = Self {
         abs: 0.0,
+        dp: 0.0,
         rel: 0.0,
         rest: 0.0,
     };
 
     pub const REST: Self = Self {
         abs: 0.0,
+        dp: 0.0,
         rel: 0.0,
         rest: 1.0,
     };
 
-    pub fn apply_rest(&self) -> UiScalar {
+    /// Resolves to a `UiScalar`, folding `dp` into `abs` pixels against
+    /// `density` (physical pixels per dp -- 1.0 on a desktop or an
+    /// unscaled display, `content_scale` on Android; see `dp`'s field
+    /// doc). Every other component of `Len` is already resolution-
+    /// independent (`rel` is a fraction of the parent; `rest` becomes a
+    /// fraction too, below), so `density` only ever touches this one term.
+    pub fn apply_rest(&self, density: f32) -> UiScalar {
         UiScalar {
             rel: self.rel + if self.rest > 0.0 { 1.0 } else { 0.0 },
-            abs: self.abs,
+            abs: self.abs + self.dp * density,
         }
     }
 
     pub fn abs(abs: impl UiNum) -> Self {
         Self {
             abs: abs.to_f32(),
+            dp: 0.0,
+            rel: 0.0,
+            rest: 0.0,
+        }
+    }
+    pub fn dp(dp: impl UiNum) -> Self {
+        Self {
+            abs: 0.0,
+            dp: dp.to_f32(),
             rel: 0.0,
             rest: 0.0,
         }
@@ -125,6 +166,7 @@ impl Len {
     pub fn rel(rel: impl UiNum) -> Self {
         Self {
             abs: 0.0,
+            dp: 0.0,
             rel: rel.to_f32(),
             rest: 0.0,
         }
@@ -132,6 +174,7 @@ impl Len {
     pub fn rest(ratio: impl UiNum) -> Self {
         Self {
             abs: 0.0,
+            dp: 0.0,
             rel: 0.0,
             rest: ratio.to_f32(),
         }
@@ -144,6 +187,15 @@ pub mod len_fns {
     pub fn abs(abs: impl UiNum) -> Len {
         Len {
             abs: abs.to_f32(),
+            dp: 0.0,
+            rel: 0.0,
+            rest: 0.0,
+        }
+    }
+    pub fn dp(dp: impl UiNum) -> Len {
+        Len {
+            abs: 0.0,
+            dp: dp.to_f32(),
             rel: 0.0,
             rest: 0.0,
         }
@@ -151,6 +203,7 @@ pub mod len_fns {
     pub fn rel(rel: impl UiNum) -> Len {
         Len {
             abs: 0.0,
+            dp: 0.0,
             rel: rel.to_f32(),
             rest: 0.0,
         }
@@ -158,14 +211,15 @@ pub mod len_fns {
     pub fn rest(ratio: impl UiNum) -> Len {
         Len {
             abs: 0.0,
+            dp: 0.0,
             rel: 0.0,
             rest: ratio.to_f32(),
         }
     }
 }
 
-impl_op!(Len Add add; abs rel rest);
-impl_op!(Len Sub sub; abs rel rest);
+impl_op!(Len Add add; abs dp rel rest);
+impl_op!(Len Sub sub; abs dp rel rest);
 
 impl_op!(Size Add add; x y);
 impl_op!(Size Sub sub; x y);
@@ -187,6 +241,9 @@ impl std::fmt::Display for Len {
         if self.abs != 0.0 {
             write!(f, "{} abs;", self.abs)?;
         }
+        if self.dp != 0.0 {
+            write!(f, "{} dp;", self.dp)?;
+        }
         if self.rel != 0.0 {
             write!(f, "{} rel;", self.rel)?;
         }

iris/core/src/primitive/text.rs

@@ -2,14 +2,63 @@ use crate::{Align, GlyphAtlas, GlyphKey, PlacedGlyph, RegionAlign, Textures, UiC
 use parley::{
     Alignment, AlignmentOptions, FontContext, FontFamily, FontFamilyName, FontStyle, FontWeight,
     GenericFamily, Layout, LayoutContext, LineHeight, PositionedLayoutItem, StyleProperty,
+    fontique::{Blob, FamilyId},
 };
 use std::ops::Range;
+use std::sync::Arc;
 use swash::{
     FontRef,
     scale::{Render, ScaleContext, Source, StrikeWith},
     zeno::{Format, Vector},
 };
 
+/// Bundled fonts, registered over the system collection rather than relied
+/// on alone -- see `TextData::register_bundled_fonts`'s doc comment for
+/// why. Static weight/style cuts, not a variable font: parley/fontique
+/// resolve a variable font's weight axis by picking normalized coordinates
+/// on whatever single face registers for the family, and a phone whose
+/// system "Roboto" is actually the variable "Roboto Flex" is exactly the
+/// device class this sidesteps, rather than depends on working correctly.
+/// Noto Sans, OFL-licensed (`assets/fonts/OFL.txt`), chosen for coverage
+/// breadth (a transcript's content is not known in advance) over a
+/// smaller-footprint alternative -- see the doc comment for the size this
+/// added.
+const NOTO_SANS_REGULAR: &[u8] = include_bytes!("../../assets/fonts/NotoSans-Regular.ttf");
+const NOTO_SANS_BOLD: &[u8] = include_bytes!("../../assets/fonts/NotoSans-Bold.ttf");
+const NOTO_SANS_ITALIC: &[u8] = include_bytes!("../../assets/fonts/NotoSans-Italic.ttf");
+const NOTO_SANS_BOLD_ITALIC: &[u8] = include_bytes!("../../assets/fonts/NotoSans-BoldItalic.ttf");
+const NOTO_SANS_MONO_REGULAR: &[u8] = include_bytes!("../../assets/fonts/NotoSansMono-Regular.ttf");
+const NOTO_SANS_MONO_BOLD: &[u8] = include_bytes!("../../assets/fonts/NotoSansMono-Bold.ttf");
+
+/// What starting up found about text rendering, for the on-screen
+/// Diagnostics page and the one startup log line (RUST.md's P0 box, "log
+/// once at startup ... the number of font families found, the default
+/// family resolved"). Built once by `TextData::font_diagnostics` --
+/// `Default::default` still exists for callers (tests, examples) that
+/// don't need the report.
+#[derive(Clone, Debug)]
+pub struct FontDiagnostics {
+    /// `Collection::family_names().count()` after registering the bundled
+    /// fonts -- system families plus the two bundled ones.
+    pub families_found: usize,
+    /// The family `GenericFamily::SansSerif` resolves to first -- the
+    /// bundled "Noto Sans" unless registration itself failed.
+    pub default_family: Option<String>,
+    /// The family `GenericFamily::Monospace` resolves to first.
+    pub default_mono_family: Option<String>,
+    /// One resolved family name per style axis this crate actually uses
+    /// (`SpanStyle::bold`/`italic`), so a report can say plainly whether a
+    /// bold/italic request is landing on a real face rather than being
+    /// silently absorbed by whatever the sans-serif default resolves to
+    /// for every weight (RUST.md's P0 box, "bold words render as blank
+    /// gaps" -- a family that resolves but has no distinct bold face is
+    /// exactly what produced that).
+    pub regular_resolved: Option<String>,
+    pub bold_resolved: Option<String>,
+    pub italic_resolved: Option<String>,
+    pub mono_resolved: Option<String>,
+}
+
 /// Everything text needs that outlives one string: the font collection, the
 /// layout scratch space, the glyph rasteriser and the atlas they fill.
 pub struct TextData {
@@ -17,15 +66,182 @@ pub struct TextData {
     pub layout_cx: LayoutContext<UiColor>,
     scale_cx: ScaleContext,
     pub atlas: GlyphAtlas,
+    /// Physical pixels per dp -- a second copy of
+    /// `UiRenderState::density`, kept here too because `TextEditCtx::layout`
+    /// (cursor movement and hit-testing, `widget/text/edit.rs`) shapes text
+    /// from an event callback that has a `TextData` but no `Painter`, so it
+    /// has nowhere else to read the display's density from. Both copies are
+    /// set together, from the one place either backend learns the real
+    /// value (`android::view::new_peer`); this is the same accepted
+    /// duplication as `AndroidRenderer::content_scale`; a single source of
+    /// truth would mean carrying a `Painter` (or output size) into every
+    /// input handler for the sake of one field.
+    pub density: f32,
 }
 
 impl Default for TextData {
     fn default() -> Self {
-        Self {
+        let mut data = Self {
             font_cx: FontContext::new(),
             layout_cx: LayoutContext::new(),
             scale_cx: ScaleContext::new(),
             atlas: GlyphAtlas::default(),
+            density: 1.0,
+        };
+        data.register_bundled_fonts();
+        data
+    }
+}
+
+impl TextData {
+    /// Registers Noto Sans (regular/bold/italic/bold-italic) and Noto Sans
+    /// Mono (regular/bold) as static faces, and puts them **first** in the
+    /// `SansSerif`/`Monospace` generic-family fallback lists -- ahead of,
+    /// not instead of, whatever the platform already found, so a script
+    /// Noto Sans lacks (CJK, emoji, ...) still falls through to the system
+    /// font the same as before this existed.
+    ///
+    /// Exists because text rendering must not depend on the platform's own
+    /// font enumeration succeeding or resolving weight/style the way this
+    /// crate assumes: RUST.md's P0 box found bold spans on a real phone
+    /// rendering as blank gaps of the correct advance width (the glyph
+    /// simply wasn't rasterised -- `TextData::place`'s `None` arm), while
+    /// the emulator's system fonts happened to resolve every style. A
+    /// bundled, static-per-style family removes fontique's Android font
+    /// scan (`fontique::backend::android::SystemFonts::new`, which parses
+    /// `/system/fonts` and `/system/etc/fonts.xml`) from the path a glyph
+    /// has to survive to reach the screen at all.
+    ///
+    /// Cost: six static `.ttf`s, ~3.6 MB uncompressed
+    /// (`iris/core/assets/fonts/`), landing in the APK compressed --
+    /// `build-apk.sh`'s own output is what says the delivered number, not
+    /// this comment.
+    fn register_bundled_fonts(&mut self) {
+        fn register(cx: &mut FontContext, bytes: &'static [u8]) -> Option<FamilyId> {
+            let blob = Blob::new(Arc::new(bytes));
+            cx.collection
+                .register_fonts(blob, None)
+                .into_iter()
+                .map(|(id, _)| id)
+                .next()
+        }
+        let sans_id = register(&mut self.font_cx, NOTO_SANS_REGULAR);
+        register(&mut self.font_cx, NOTO_SANS_BOLD);
+        register(&mut self.font_cx, NOTO_SANS_ITALIC);
+        register(&mut self.font_cx, NOTO_SANS_BOLD_ITALIC);
+        let mono_id = register(&mut self.font_cx, NOTO_SANS_MONO_REGULAR);
+        register(&mut self.font_cx, NOTO_SANS_MONO_BOLD);
+
+        if let Some(sans_id) = sans_id {
+            let existing: Vec<_> = self
+                .font_cx
+                .collection
+                .generic_families(GenericFamily::SansSerif)
+                .collect();
+            self.font_cx.collection.set_generic_families(
+                GenericFamily::SansSerif,
+                std::iter::once(sans_id).chain(existing),
+            );
+            let existing: Vec<_> = self
+                .font_cx
+                .collection
+                .generic_families(GenericFamily::SystemUi)
+                .collect();
+            self.font_cx.collection.set_generic_families(
+                GenericFamily::SystemUi,
+                std::iter::once(sans_id).chain(existing),
+            );
+        }
+        if let Some(mono_id) = mono_id {
+            let existing: Vec<_> = self
+                .font_cx
+                .collection
+                .generic_families(GenericFamily::Monospace)
+                .collect();
+            self.font_cx.collection.set_generic_families(
+                GenericFamily::Monospace,
+                std::iter::once(mono_id).chain(existing),
+            );
+        }
+    }
+
+    /// Builds the startup report -- see `FontDiagnostics`. Queries the
+    /// collection directly (`fontique::Query`) rather than shaping a real
+    /// string, since all that's needed is which family each axis lands on.
+    pub fn font_diagnostics(&mut self) -> FontDiagnostics {
+        use parley::fontique::{Attributes, FontWidth, QueryStatus};
+        let families_found = self.font_cx.collection.family_names().count();
+        let default_family_id = self
+            .font_cx
+            .collection
+            .generic_families(GenericFamily::SansSerif)
+            .next();
+        let default_family = default_family_id
+            .and_then(|id| self.font_cx.collection.family_name(id).map(str::to_string));
+        let default_mono_family_id = self
+            .font_cx
+            .collection
+            .generic_families(GenericFamily::Monospace)
+            .next();
+        let default_mono_family = default_mono_family_id
+            .and_then(|id| self.font_cx.collection.family_name(id).map(str::to_string));
+
+        // Resolves the family a (generic family, weight, style) query lands
+        // on, without holding the `Query`'s borrow of `collection` across
+        // the `family_name` lookup that needs it back -- the `FamilyId` is
+        // captured out of the closure first, then looked up once `query`
+        // (and its borrow) has been dropped.
+        let mut resolve_family =
+            |generic: GenericFamily, weight: FontWeight, style: FontStyle| -> Option<String> {
+                let mut family_id = None;
+                {
+                    let mut query = self
+                        .font_cx
+                        .collection
+                        .query(&mut self.font_cx.source_cache);
+                    query.set_families([generic]);
+                    query.set_attributes(Attributes {
+                        width: FontWidth::NORMAL,
+                        style,
+                        weight,
+                    });
+                    query.matches_with(|font| {
+                        family_id = Some(font.family.0);
+                        QueryStatus::Stop
+                    });
+                }
+                family_id.and_then(|id| self.font_cx.collection.family_name(id).map(str::to_string))
+            };
+
+        let regular_resolved = resolve_family(
+            GenericFamily::SansSerif,
+            FontWeight::NORMAL,
+            FontStyle::Normal,
+        );
+        let bold_resolved = resolve_family(
+            GenericFamily::SansSerif,
+            FontWeight::BOLD,
+            FontStyle::Normal,
+        );
+        let italic_resolved = resolve_family(
+            GenericFamily::SansSerif,
+            FontWeight::NORMAL,
+            FontStyle::Italic,
+        );
+        let mono_resolved = resolve_family(
+            GenericFamily::Monospace,
+            FontWeight::NORMAL,
+            FontStyle::Normal,
+        );
+
+        FontDiagnostics {
+            families_found,
+            default_family,
+            default_mono_family,
+            regular_resolved,
+            bold_resolved,
+            italic_resolved,
+            mono_resolved,
         }
     }
 }
@@ -159,7 +375,7 @@ pub struct TextBuffer {
     /// `set_spans` forces `shaped` to `None` directly, the same way `edit`
     /// does, since spans change far less often than a naive equality check
     /// on the whole `Vec` would cost to compute every frame.
-    shaped: Option<(TextAttrs, Option<f32>)>,
+    shaped: Option<(TextAttrs, Option<f32>, f32)>,
 }
 
 impl TextBuffer {
@@ -215,19 +431,42 @@ impl TextBuffer {
         Vec2::new(self.layout.width(), self.layout.height())
     }
 
-    /// Lay the text out, unless it is already laid out for these attributes and
-    /// this width.
-    pub fn shape(&mut self, data: &mut TextData, attrs: &TextAttrs, width: Option<f32>) {
-        if self.shaped.as_ref() == Some(&(attrs.clone(), width)) {
+    /// Lay the text out, unless it is already laid out for these
+    /// attributes, this width and this density.
+    ///
+    /// **`attrs.font_size`/`line_height` and every span's own `font_size`
+    /// are density-independent (dp) units, multiplied by `density` here --
+    /// the one place text crosses from the widget tree's dp sizes into the
+    /// physical pixels the shaper and rasteriser (`TextData::place`) both
+    /// then work in.** This is what makes glyphs sharp on a dense display:
+    /// before this existed, `font_size` was already a physical-pixel value
+    /// (RUST.md's P0 box's global-scale stopgap resolved density by
+    /// stretching the whole rendered frame afterward instead), so a glyph
+    /// was rasterised small and then upscaled by whatever the display's
+    /// scale factor was -- exactly the blur Iris's report described.
+    /// Multiplying here instead means the font size hitting `ScaleContext`
+    /// in `place` below is already the display's real physical size, so
+    /// the atlas holds a bitmap at the resolution it is actually shown at.
+    /// `GlyphKey.size` already keys on that resolved `font_size`
+    /// (`(font_size * 16.0).round()`), so a cache entry is naturally per
+    /// physical size with no change needed there.
+    pub fn shape(
+        &mut self,
+        data: &mut TextData,
+        attrs: &TextAttrs,
+        width: Option<f32>,
+        density: f32,
+    ) {
+        if self.shaped.as_ref() == Some(&(attrs.clone(), width, density)) {
             return;
         }
         let mut builder = data
             .layout_cx
             .ranged_builder(&mut data.font_cx, &self.text, 1.0, true);
         builder.push_default(StyleProperty::FontFamily(attrs.family.family()));
-        builder.push_default(StyleProperty::FontSize(attrs.font_size));
+        builder.push_default(StyleProperty::FontSize(attrs.font_size * density));
         builder.push_default(StyleProperty::LineHeight(LineHeight::Absolute(
-            attrs.line_height,
+            attrs.line_height * density,
         )));
         builder.push_default(StyleProperty::Brush(attrs.color));
         for span in &self.spans {
@@ -239,7 +478,7 @@ impl TextBuffer {
                 builder.push(StyleProperty::FontFamily(family.family()), range.clone());
             }
             if let Some(size) = span.font_size {
-                builder.push(StyleProperty::FontSize(size), range.clone());
+                builder.push(StyleProperty::FontSize(size * density), range.clone());
             }
             if span.bold {
                 builder.push(StyleProperty::FontWeight(FontWeight::BOLD), range.clone());
@@ -255,7 +494,7 @@ impl TextBuffer {
         self.layout.break_all_lines(width);
         self.layout
             .align(Alignment::Start, AlignmentOptions::default());
-        self.shaped = Some((attrs.clone(), width));
+        self.shaped = Some((attrs.clone(), width, density));
     }
 }
 
@@ -372,8 +611,9 @@ impl TextData {
         attrs: &TextAttrs,
         width: Option<f32>,
         textures: &mut Textures,
+        density: f32,
     ) -> RenderedText {
-        buffer.shape(self, attrs, width);
+        buffer.shape(self, attrs, width, density);
         let glyphs = self.place(buffer, textures);
         RenderedText {
             glyphs: std::sync::Arc::new(glyphs),

iris/core/src/render/frame_report.rs

@@ -0,0 +1,548 @@
+use std::time::{Duration, Instant};
+
+/// The frame budget `dumpsys gfxinfo` also uses to call a frame "janky": the
+/// 60Hz vsync period. Kept as the same threshold so a percentage from this
+/// report and a percentage from `gfxinfo` mean the same thing. Only a
+/// fallback now that a caller can read the display's real refresh rate
+/// (`report_at_hz`/`mark_phase`'s callers) -- most devices are 60Hz, but a
+/// 90Hz or 120Hz phone judged against this constant would call every frame
+/// "late" that merely met its own, faster budget.
+pub const JANK_THRESHOLD: Duration = Duration::from_nanos(16_666_667);
+
+/// Enough frames for several minutes of scrolling before the oldest ones
+/// start being overwritten -- the same "diagnostic, not a log" sizing
+/// `FrameStats.kt`'s `CAP` uses on the Compose side, chosen independently
+/// here since a `Duration` is smaller than the six `Long` arrays it keeps.
+/// Bumped from 4096 for RUST.md's "Benchmark v2": a fling+stream+type+
+/// keyboard run is ~6,500+ frames on the Compose side, comfortably under
+/// this so `phase_stats` never has to report a phase as partially evicted.
+const RING_CAPACITY: usize = 16384;
+
+/// One `mark_phase` call: the wall-clock instant and the (0-based,
+/// never-reset-by-`reset`-except-at-`reset`-time) absolute frame index at
+/// which a phase began -- `phase_stats` slices `index_ring` against this to
+/// find which recorded samples belong to which phase, since the ring
+/// itself only keeps the most recent `RING_CAPACITY` samples' *values*,
+/// not which phase they were in.
+struct PhaseMark {
+    name: String,
+    start_index: u64,
+    start_at: Instant,
+}
+
+/// One phase's own slice of a report -- RUST.md's "Benchmark v2" spec's
+/// "per-phase blocks in `FrameReport`... frames, late count/percent...
+/// p50/p90/p99, worst, duration". `Display` matches the shape
+/// `docs/bench/compose-phone-v2-2026-09-06.md`'s report already uses, so
+/// the two apps' reports read the same way side by side.
+pub struct PhaseStats {
+    pub name: String,
+    /// How many frames were recorded during this phase in total -- may
+    /// exceed `late + (samples counted)` if some of this phase's frames
+    /// have since been evicted from the ring by a very long run; that
+    /// case is named in the `Display` rather than silently under-counted.
+    pub frames: u64,
+    pub duration: Duration,
+    pub late: u64,
+    pub late_percent: f64,
+    pub p50: Duration,
+    pub p90: Duration,
+    pub p99: Duration,
+    pub worst: Duration,
+    /// `false` if this phase's frame count exceeds how many samples of it
+    /// are still in the ring -- the percentiles above are then computed
+    /// over whatever survived, not the whole phase. UI_RULES.md: this is
+    /// the "we don't fully know" state, named rather than folded silently
+    /// into a number that looks exact.
+    pub complete: bool,
+}
+
+impl std::fmt::Display for PhaseStats {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        writeln!(
+            f,
+            "  {}: {} frames over {:.1}s{}",
+            self.name,
+            self.frames,
+            self.duration.as_secs_f64(),
+            if self.complete {
+                ""
+            } else {
+                " (ring evicted some of this phase)"
+            },
+        )?;
+        writeln!(f, "    late: {} ({:.1}%)", self.late, self.late_percent)?;
+        writeln!(
+            f,
+            "      total  p50 {:.1}ms  p90 {:.1}ms  p99 {:.1}ms",
+            self.p50.as_secs_f64() * 1000.0,
+            self.p90.as_secs_f64() * 1000.0,
+            self.p99.as_secs_f64() * 1000.0,
+        )?;
+        write!(f, "    worst {:.1}ms", self.worst.as_secs_f64() * 1000.0)
+    }
+}
+
+/// A per-frame wall-time report iris keeps of itself, because `dumpsys
+/// gfxinfo` cannot see a `SurfaceView`'s own GPU-drawn frames at all
+/// (RUST.md's I5 box, "Measurements taken" (b)): it instruments Android's
+/// ordinary Skia/HWUI View-drawing pipeline, which a `wgpu`-rendered
+/// `SurfaceView` bypasses entirely. `record` is meant to be called once per
+/// frame, wrapping the same span Compose's own render report and `gfxinfo`
+/// count -- from the frame's redraw/update start to after the frame is
+/// handed to the platform to present.
+///
+/// **What this does not measure**: wgpu's `present()` call queues the frame
+/// with the compositor and returns; it is not fenced against the GPU
+/// actually finishing the frame or the compositor actually showing it, the
+/// way `gfxinfo`'s own `GPU_DURATION`/vsync accounting is. So a sample here
+/// is "how long the CPU took to build and submit this frame", not
+/// "how long the frame took to reach the screen" -- named in
+/// [`FrameStats`]'s own `Display` line rather than presented as the latter,
+/// per the standing rule against showing an inferred number as a measured
+/// one where the two differ.
+///
+/// Fixed-size ring, no allocation on the hot path -- `report()` is the only
+/// place that allocates (a sort over the current ring), and it is only
+/// ever called from a button tap, not once per frame.
+pub struct FrameReport {
+    ring: Box<[Duration; RING_CAPACITY]>,
+    /// The `submit_to_present` half of each sample in `ring`, same index,
+    /// same lifetime -- kept as a second ring rather than a ring of pairs so
+    /// the existing `ring`/percentile code above is untouched (RUST.md's I5
+    /// "Where iris's frame time goes" CPU/GPU split, added 2026-09-05).
+    /// `ring[i] - submit_ring[i]` is that frame's `redraw_to_submit` half.
+    submit_ring: Box<[Duration; RING_CAPACITY]>,
+    /// The absolute (0-based, since the last `reset`) frame index each
+    /// `ring`/`submit_ring` slot's sample belongs to -- what `phase_stats`
+    /// slices against `PhaseMark::start_index` to tell which recorded
+    /// frames fall in which phase.
+    index_ring: Box<[u64; RING_CAPACITY]>,
+    /// How many of `ring`'s slots hold a real sample -- saturates at
+    /// `RING_CAPACITY`, unlike `total_frames` below which keeps counting.
+    len: usize,
+    pos: usize,
+    /// All frames recorded since the last `reset`, even past `RING_CAPACITY`
+    /// -- what `janky_percent` divides by, so a long run's percentage stays
+    /// correct even once the ring itself only holds the most recent frames.
+    total_frames: u64,
+    janky_frames: u64,
+    /// `mark_phase` calls since the last `reset`, oldest first -- see
+    /// `phase_stats`. Empty on an ordinary run that never calls
+    /// `mark_phase`, so `phase_stats` returns an empty `Vec` and a caller
+    /// prints no "per phase:" section at all, matching RUST.md's "empty/
+    /// absent on an ordinary 'Copy' press, which never marks a phase."
+    phases: Vec<PhaseMark>,
+}
+
+/// One resolved reading. `Display` is the log line both the "Frame report"
+/// button and `transcript-bench.sh`-style scripts read, grep-able on
+/// `"iris frame report"`.
+pub struct FrameStats {
+    pub total_frames: u64,
+    pub janky_percent: f64,
+    pub p50: Duration,
+    pub p90: Duration,
+    pub p99: Duration,
+    pub worst: Duration,
+    /// Median of `redraw_to_submit` -- iris's own CPU work (layout, text,
+    /// primitive building) up to and including building the `queue.submit`
+    /// call, per frame. RUST.md's I5 "Where iris's frame time goes" split,
+    /// added 2026-09-05 to answer "CPU or GPU?" with a number rather than a
+    /// guess.
+    pub cpu_p50: Duration,
+    /// Median of `submit_to_present` -- the `queue.submit` call itself plus
+    /// `present()`, i.e. wherever the driver/GPU/compositor wait actually
+    /// happens. Same caveat as the type's own doc: `present()` is not
+    /// fenced against the GPU actually finishing, so this is "how long the
+    /// CPU was blocked handing the frame off", not the frame's true GPU
+    /// time -- still enough to separate "iris is slow building the frame"
+    /// from "iris is slow handing it to the driver".
+    pub gpu_wait_p50: Duration,
+}
+
+impl std::fmt::Display for FrameStats {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "frames={} janky%={:.2} p50={:.1}ms p90={:.1}ms p99={:.1}ms worst={:.1}ms \
+             (measures redraw-start to after present() is called, not GPU/compositor \
+             completion)",
+            self.total_frames,
+            self.janky_percent,
+            self.p50.as_secs_f64() * 1000.0,
+            self.p90.as_secs_f64() * 1000.0,
+            self.p99.as_secs_f64() * 1000.0,
+            self.worst.as_secs_f64() * 1000.0,
+        )?;
+        write!(
+            f,
+            " cpu_p50={:.1}ms gpu_wait_p50={:.1}ms (redraw-start-to-submit vs. \
+             submit-to-after-present)",
+            self.cpu_p50.as_secs_f64() * 1000.0,
+            self.gpu_wait_p50.as_secs_f64() * 1000.0,
+        )
+    }
+}
+
+impl FrameReport {
+    pub fn new() -> Self {
+        Self {
+            ring: Box::new([Duration::ZERO; RING_CAPACITY]),
+            submit_ring: Box::new([Duration::ZERO; RING_CAPACITY]),
+            index_ring: Box::new([0; RING_CAPACITY]),
+            len: 0,
+            pos: 0,
+            total_frames: 0,
+            janky_frames: 0,
+            phases: Vec::new(),
+        }
+    }
+
+    /// Record one frame's elapsed wall time, with no CPU/GPU split (the
+    /// `submit_to_present` half is recorded as zero, so `cpu_p50` reads as
+    /// the whole frame and `gpu_wait_p50` as nothing -- honest for a caller
+    /// that never measured the split, rather than fabricating one). O(1),
+    /// no allocation.
+    pub fn record(&mut self, elapsed: Duration) {
+        self.record_split(elapsed, Duration::ZERO);
+    }
+
+    /// Record one frame's elapsed wall time, split at `queue.submit`:
+    /// `submit_to_present` is the `queue.submit()` call plus `present()`;
+    /// `total - submit_to_present` is everything before it (layout, text,
+    /// primitive building). RUST.md's I5 "Where iris's frame time goes"
+    /// CPU/GPU split, added 2026-09-05. O(1), no allocation.
+    pub fn record_split(&mut self, total: Duration, submit_to_present: Duration) {
+        self.ring[self.pos] = total;
+        self.submit_ring[self.pos] = submit_to_present;
+        self.index_ring[self.pos] = self.total_frames;
+        self.pos = (self.pos + 1) % RING_CAPACITY;
+        self.len = (self.len + 1).min(RING_CAPACITY);
+        self.total_frames += 1;
+        if total > JANK_THRESHOLD {
+            self.janky_frames += 1;
+        }
+    }
+
+    /// Clears every counter and every sample -- what the "Reset frame
+    /// report" control calls, so a report covers only what was scrolled
+    /// after the button was pressed (the same reason `FrameStats.kt`'s
+    /// `reset()` exists on the Compose side). Also clears every phase
+    /// mark, so a fresh run starts with no "per phase:" section until it
+    /// marks one of its own.
+    pub fn reset(&mut self) {
+        self.len = 0;
+        self.pos = 0;
+        self.total_frames = 0;
+        self.janky_frames = 0;
+        self.phases.clear();
+    }
+
+    /// Marks the start of a named phase at the current moment -- every
+    /// frame recorded from here until the next `mark_phase` (or `reset`)
+    /// belongs to it. RUST.md's "Benchmark v2": a scripted bench run calls
+    /// this once per phase (fling/stream/type/keyboard) so `phase_stats`
+    /// can slice one whole run's frames by what was happening during each.
+    pub fn mark_phase(&mut self, name: &str) {
+        self.phases.push(PhaseMark {
+            name: name.to_string(),
+            start_index: self.total_frames,
+            start_at: Instant::now(),
+        });
+    }
+
+    /// One [`PhaseStats`] per `mark_phase` call since the last `reset`,
+    /// oldest first. `now` closes the last phase's wall-clock span (there
+    /// is no "next phase" instant to use for it); `refresh_hz` is what
+    /// each phase's own `late`/`late_percent` is judged against, read from
+    /// the display rather than assumed -- RUST.md's "Benchmark v2": "late
+    /// count/% against the display's refresh rate."
+    pub fn phase_stats(&self, now: Instant, refresh_hz: f32) -> Vec<PhaseStats> {
+        if self.phases.is_empty() || refresh_hz <= 0.0 {
+            return Vec::new();
+        }
+        let budget = Duration::from_secs_f64(1.0 / refresh_hz as f64);
+        self.phases
+            .iter()
+            .enumerate()
+            .map(|(i, phase)| {
+                let (end_index, end_at) = match self.phases.get(i + 1) {
+                    Some(next) => (next.start_index, next.start_at),
+                    None => (self.total_frames, now),
+                };
+                let frames = end_index.saturating_sub(phase.start_index);
+                let mut samples: Vec<Duration> = (0..self.len)
+                    .filter(|&j| {
+                        let idx = self.index_ring[j];
+                        idx >= phase.start_index && idx < end_index
+                    })
+                    .map(|j| self.ring[j])
+                    .collect();
+                let complete = samples.len() as u64 >= frames;
+                if samples.is_empty() {
+                    return PhaseStats {
+                        name: phase.name.clone(),
+                        frames,
+                        duration: end_at.saturating_duration_since(phase.start_at),
+                        late: 0,
+                        late_percent: 0.0,
+                        p50: Duration::ZERO,
+                        p90: Duration::ZERO,
+                        p99: Duration::ZERO,
+                        worst: Duration::ZERO,
+                        complete,
+                    };
+                }
+                samples.sort_unstable();
+                let pct = |p: usize| samples[(samples.len() * p / 100).min(samples.len() - 1)];
+                let late = samples.iter().filter(|&&d| d > budget).count() as u64;
+                PhaseStats {
+                    name: phase.name.clone(),
+                    frames,
+                    duration: end_at.saturating_duration_since(phase.start_at),
+                    late,
+                    late_percent: 100.0 * late as f64 / samples.len() as f64,
+                    p50: pct(50),
+                    p90: pct(90),
+                    p99: pct(99),
+                    worst: *samples.last().expect("checked not empty above"),
+                    complete,
+                }
+            })
+            .collect()
+    }
+
+    /// `None` if nothing has been recorded since the last reset -- the
+    /// "no frames recorded, scroll first" case, not a zeroed report that
+    /// would read as a real (perfect) measurement.
+    pub fn report(&self) -> Option<FrameStats> {
+        if self.len == 0 {
+            return None;
+        }
+        let mut samples: Vec<Duration> = self.ring[..self.len].to_vec();
+        samples.sort_unstable();
+        let pct = |p: usize| samples[(samples.len() * p / 100).min(samples.len() - 1)];
+
+        // Separate arrays rather than subtracting the two medians above:
+        // medians do not distribute over subtraction, and each needs its
+        // own sort.
+        let submit_samples: Vec<Duration> = self.submit_ring[..self.len].to_vec();
+        let cpu_samples: Vec<Duration> = self.ring[..self.len]
+            .iter()
+            .zip(self.submit_ring[..self.len].iter())
+            .map(|(&total, &submit_to_present)| total.saturating_sub(submit_to_present))
+            .collect();
+        let median = |mut v: Vec<Duration>| {
+            v.sort_unstable();
+            v[v.len() / 2]
+        };
+
+        Some(FrameStats {
+            total_frames: self.total_frames,
+            janky_percent: 100.0 * self.janky_frames as f64 / self.total_frames as f64,
+            p50: pct(50),
+            p90: pct(90),
+            p99: pct(99),
+            worst: *samples.last().expect("len > 0 checked above"),
+            cpu_p50: median(cpu_samples),
+            gpu_wait_p50: median(submit_samples),
+        })
+    }
+
+    /// `(late count, late percent)` over every sample still in the ring,
+    /// judged against `refresh_hz`'s own frame budget rather than the
+    /// fixed 60Hz `JANK_THRESHOLD` -- RUST.md's "Benchmark v2": "late
+    /// count/% against the display's refresh rate... print 'at N Hz (X ms
+    /// budget)' like Compose does." A separate method from `report()`
+    /// rather than a parameter on it, so `report()`'s own `janky_percent`
+    /// (and the exact-boundary test pinned to `JANK_THRESHOLD`) is
+    /// unaffected for every existing caller that never measured a real
+    /// refresh rate. `(0, 0.0)` with nothing recorded or a non-positive
+    /// `refresh_hz`.
+    pub fn late_at_hz(&self, refresh_hz: f32) -> (u64, f64) {
+        if self.len == 0 || refresh_hz <= 0.0 {
+            return (0, 0.0);
+        }
+        let budget = Duration::from_secs_f64(1.0 / refresh_hz as f64);
+        let late = self.ring[..self.len]
+            .iter()
+            .filter(|&&d| d > budget)
+            .count() as u64;
+        (late, 100.0 * late as f64 / self.len as f64)
+    }
+}
+
+impl Default for FrameReport {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn no_frames_reports_none() {
+        assert!(FrameReport::new().report().is_none());
+    }
+
+    #[test]
+    fn one_frame_is_every_percentile_and_the_worst() {
+        let mut r = FrameReport::new();
+        r.record(Duration::from_millis(10));
+        let stats = r.report().unwrap();
+        assert_eq!(stats.total_frames, 1);
+        assert_eq!(stats.p50, Duration::from_millis(10));
+        assert_eq!(stats.p99, Duration::from_millis(10));
+        assert_eq!(stats.worst, Duration::from_millis(10));
+        assert_eq!(stats.janky_percent, 0.0);
+    }
+
+    #[test]
+    fn percentiles_and_worst_over_a_known_set() {
+        let mut r = FrameReport::new();
+        // 100 samples, 1ms..=100ms, fed out of order so the ring's own
+        // order is not what gives the right answer -- the sort has to.
+        for ms in (1..=100).rev() {
+            r.record(Duration::from_millis(ms));
+        }
+        let stats = r.report().unwrap();
+        assert_eq!(stats.total_frames, 100);
+        assert_eq!(stats.p50, Duration::from_millis(51));
+        assert_eq!(stats.p90, Duration::from_millis(91));
+        assert_eq!(stats.p99, Duration::from_millis(100));
+        assert_eq!(stats.worst, Duration::from_millis(100));
+    }
+
+    #[test]
+    fn jank_threshold_matches_gfxinfos_60hz_budget() {
+        let mut r = FrameReport::new();
+        r.record(Duration::from_nanos(16_666_667)); // exactly on budget: not janky
+        r.record(Duration::from_nanos(16_666_668)); // one ns over: janky
+        let stats = r.report().unwrap();
+        assert_eq!(stats.janky_percent, 50.0);
+    }
+
+    #[test]
+    fn janky_percent_is_over_all_time_frames_not_just_the_ring() {
+        // Fewer than RING_CAPACITY frames, all janky, then a fresh reset --
+        // the percentage must reset to 0, not divide by a stale count.
+        let mut r = FrameReport::new();
+        for _ in 0..10 {
+            r.record(Duration::from_millis(50));
+        }
+        assert_eq!(r.report().unwrap().janky_percent, 100.0);
+        r.reset();
+        assert!(r.report().is_none());
+        r.record(Duration::from_millis(1));
+        assert_eq!(r.report().unwrap().janky_percent, 0.0);
+    }
+
+    #[test]
+    fn record_without_a_split_reports_the_whole_frame_as_cpu() {
+        // A caller that never measured the split (plain `record`) should
+        // not fabricate a GPU-wait number -- it reads as zero, and the CPU
+        // half reads as the whole frame.
+        let mut r = FrameReport::new();
+        r.record(Duration::from_millis(20));
+        let stats = r.report().unwrap();
+        assert_eq!(stats.cpu_p50, Duration::from_millis(20));
+        assert_eq!(stats.gpu_wait_p50, Duration::ZERO);
+    }
+
+    #[test]
+    fn record_split_reports_each_halfs_own_median() {
+        let mut r = FrameReport::new();
+        // Three frames: total is always 30ms, but the CPU/GPU-wait split
+        // moves, so the two medians must be independent of each other and
+        // of `total`'s own median.
+        r.record_split(Duration::from_millis(30), Duration::from_millis(5));
+        r.record_split(Duration::from_millis(30), Duration::from_millis(10));
+        r.record_split(Duration::from_millis(30), Duration::from_millis(20));
+        let stats = r.report().unwrap();
+        assert_eq!(stats.p50, Duration::from_millis(30));
+        assert_eq!(stats.gpu_wait_p50, Duration::from_millis(10));
+        assert_eq!(stats.cpu_p50, Duration::from_millis(20));
+    }
+
+    #[test]
+    fn ring_wraps_without_growing_past_capacity() {
+        let mut r = FrameReport::new();
+        for i in 0..(RING_CAPACITY * 2) {
+            r.record(Duration::from_millis(1 + (i % 5) as u64));
+        }
+        let stats = r.report().unwrap();
+        // total_frames keeps the full count even once the ring has wrapped.
+        assert_eq!(stats.total_frames, (RING_CAPACITY * 2) as u64);
+        // but every sample the ring can report on is still one of the five
+        // values fed in, since a wrap can only overwrite with more of the
+        // same pattern here.
+        assert!(stats.worst <= Duration::from_millis(5));
+    }
+
+    #[test]
+    fn no_marks_means_no_phases() {
+        let mut r = FrameReport::new();
+        r.record(Duration::from_millis(5));
+        assert!(r.phase_stats(Instant::now(), 60.0).is_empty());
+    }
+
+    #[test]
+    fn phases_slice_frames_by_when_they_were_marked() {
+        let mut r = FrameReport::new();
+        r.mark_phase("a");
+        for _ in 0..5 {
+            r.record(Duration::from_millis(10)); // 10ms: late at 60Hz (16.7ms budget)... no, 10<16.7, not late
+        }
+        r.mark_phase("b");
+        for _ in 0..3 {
+            r.record(Duration::from_millis(20)); // 20ms: late at 60Hz
+        }
+        let now = Instant::now();
+        let phases = r.phase_stats(now, 60.0);
+        assert_eq!(phases.len(), 2);
+        assert_eq!(phases[0].name, "a");
+        assert_eq!(phases[0].frames, 5);
+        assert_eq!(phases[0].late, 0);
+        assert_eq!(phases[0].worst, Duration::from_millis(10));
+        assert_eq!(phases[1].name, "b");
+        assert_eq!(phases[1].frames, 3);
+        assert_eq!(phases[1].late, 3);
+        assert_eq!(phases[1].late_percent, 100.0);
+        assert_eq!(phases[1].worst, Duration::from_millis(20));
+        assert!(phases[0].complete);
+        assert!(phases[1].complete);
+    }
+
+    #[test]
+    fn the_last_phase_runs_until_now() {
+        let mut r = FrameReport::new();
+        r.mark_phase("only");
+        r.record(Duration::from_millis(1));
+        std::thread::sleep(Duration::from_millis(20));
+        let now = Instant::now();
+        let phases = r.phase_stats(now, 60.0);
+        assert_eq!(phases.len(), 1);
+        assert!(phases[0].duration >= Duration::from_millis(20));
+    }
+
+    #[test]
+    fn reset_clears_phase_marks() {
+        let mut r = FrameReport::new();
+        r.mark_phase("a");
+        r.record(Duration::from_millis(1));
+        r.reset();
+        assert!(r.phase_stats(Instant::now(), 60.0).is_empty());
+    }
+
+    #[test]
+    fn late_at_hz_uses_the_given_refresh_rate_not_the_fixed_60hz_constant() {
+        let mut r = FrameReport::new();
+        // 10ms is under 60Hz's 16.7ms budget but over 120Hz's 8.3ms one.
+        r.record(Duration::from_millis(10));
+        assert_eq!(r.late_at_hz(60.0), (0, 0.0));
+        assert_eq!(r.late_at_hz(120.0), (1, 100.0));
+    }
+}

iris/core/src/render/mod.rs

@@ -4,6 +4,7 @@ use crate::{
     util::{HashMap, Vec2},
 };
 use data::WindowUniform;
+use pollster::FutureExt;
 use wgpu::{
     util::{BufferInitDescriptor, DeviceExt},
     *,
@@ -11,16 +12,111 @@ use wgpu::{
 
 mod atlas;
 mod data;
+mod frame_report;
 mod primitive;
 mod texture;
 mod util;
 
 pub use atlas::*;
 pub use data::{Mask, MaskIdx, MoveIdx, MoveOffset};
+pub use frame_report::{FrameReport, FrameStats, JANK_THRESHOLD};
 pub use primitive::*;
 
 const SHAPE_SHADER: &str = include_str!("./shader.wgsl");
 
+/// The `wgpu::Limits` both platform backends (`android::render::
+/// AndroidRenderer::new`, `default::render::UiRenderer::new`) ask
+/// `Adapter::request_device` for -- shared so the two copies cannot drift,
+/// per AGENTS.md's "write the logic once."
+///
+/// Built from `Limits::default()`, **not** a downlevel variant: the shader
+/// (`shader.wgsl`) reads four `var<storage>` buffers (rects, glyphs, masks,
+/// move_offsets) from the vertex stage, and `Limits::downlevel_webgl2_defaults()`
+/// zeroes `max_storage_buffers_per_shader_stage` along with the compute
+/// limits below -- switching to it would trade one `request_device` crash
+/// for a bind-group-layout one on the same downlevel hardware this is meant
+/// to support. `max_buffer_size` is raised for the growing instance/atlas
+/// buffers (`ArrBuf`, `GpuTextures`); everything else is `default()`'s
+/// desktop-tier value, unchanged.
+///
+/// The six `max_compute_*` fields are zeroed because nothing in this crate
+/// creates a `ComputePipeline` or writes a `@compute` shader stage --
+/// grepped for both across `iris`/`iris-core` before writing this, found
+/// none. `Limits::default()` requests desktop-tier compute limits
+/// unconditionally (`max_compute_workgroups_per_dimension: 65535`) even
+/// though nothing asks a device to actually support compute, which is what
+/// crashed `request_device` on the Android emulator's software GL path
+/// (`EMU_GPU=software`, `force-gles`): SwiftShader's GL reports itself as
+/// OpenGL ES 3.0, which has no compute shaders, so the adapter's real limit
+/// is 0 and the unconditional request fails outright
+/// (`RUST.md`'s "Software mode ... crashes for a third, different reason").
+/// The same would happen on a real GLES-3.0-only Android device. If a
+/// future change adds a compute pass, request the specific limits it needs
+/// here rather than reverting to the desktop-tier default for everything.
+pub fn device_limits() -> Limits {
+    Limits {
+        max_buffer_size: 1 << 30,
+        max_compute_workgroup_storage_size: 0,
+        max_compute_invocations_per_workgroup: 0,
+        max_compute_workgroup_size_x: 0,
+        max_compute_workgroup_size_y: 0,
+        max_compute_workgroup_size_z: 0,
+        max_compute_workgroups_per_dimension: 0,
+        ..Default::default()
+    }
+}
+
+/// A capped log of wgpu's *uncaptured* errors -- everything that reaches
+/// `Device::on_uncaptured_error` rather than one of `UiRenderNode::new`'s
+/// own error scopes, i.e. every wgpu error raised outside device/pipeline
+/// creation: a validation failure during an ordinary frame's `update`/
+/// `draw`, for instance. wgpu's default handler for these is `panic!` with
+/// no caller able to intervene -- exactly what aborted the P0 bench APK
+/// once already (this file's `UiRenderNode::new` doc comment) -- so both
+/// platform backends install a handler here instead of leaving the default
+/// in place, per RUST.md's P0 box ("every wgpu uncaptured error ... it
+/// must never panic in release").
+///
+/// Cheap to `Clone` (an `Arc` around the real storage) rather than a
+/// process-wide static, so a caller builds one alongside its `Device`,
+/// hands one clone to `on_uncaptured_error`'s closure and keeps the other
+/// for the Diagnostics page to read -- context passed explicitly, per
+/// AGENTS.md/CODE_RULES.md's "no globals" rather than reached for through a
+/// `OnceLock`.
+#[derive(Clone)]
+pub struct WgpuErrorLog {
+    errors: std::sync::Arc<std::sync::Mutex<std::collections::VecDeque<String>>>,
+}
+
+/// How many uncaptured errors the log keeps -- old ones drop off the front
+/// rather than being trimmed on read, so a build spraying errors every
+/// frame doesn't grow this without bound.
+const WGPU_ERROR_LOG_CAP: usize = 20;
+
+impl Default for WgpuErrorLog {
+    fn default() -> Self {
+        Self {
+            errors: std::sync::Arc::new(std::sync::Mutex::new(std::collections::VecDeque::new())),
+        }
+    }
+}
+
+impl WgpuErrorLog {
+    pub fn record(&self, error: impl std::fmt::Display) {
+        let mut errors = self.errors.lock().unwrap();
+        if errors.len() >= WGPU_ERROR_LOG_CAP {
+            errors.pop_front();
+        }
+        errors.push_back(error.to_string());
+    }
+
+    /// A snapshot for the Diagnostics page -- cloned rather than held,
+    /// since the lock must not outlive one call.
+    pub fn snapshot(&self) -> Vec<String> {
+        self.errors.lock().unwrap().iter().cloned().collect()
+    }
+}
+
 pub struct UiRenderNode {
     uniform_group: BindGroup,
     primitive_layout: BindGroupLayout,
@@ -108,7 +204,7 @@ impl UiRenderNode {
         queue: &Queue,
         ui: &mut UiData,
         ui_render: &mut UiRenderState,
-    ) {
+    ) -> FrameUpdateStats {
         self.active.clear();
         for (i, primitives) in ui_render.layers.iter_mut() {
             self.active.push(i);
@@ -192,6 +288,10 @@ impl UiRenderNode {
         if rebuild_main {
             self.rsc_group = Self::rsc_group(device, &self.rsc_layout, &self.textures);
         }
+        FrameUpdateStats {
+            masks_resized,
+            moves_resized,
+        }
     }
 
     /// Takes a size rather than a window type: this is the only thing the
@@ -207,26 +307,69 @@ impl UiRenderNode {
         queue.write_buffer(&self.window_buffer, 0, bytemuck::cast_slice(slice));
     }
 
-    pub fn new(device: &Device, queue: &Queue, config: &SurfaceConfiguration) -> Self {
+    /// Builds every bind group layout, the pipeline, and the two storage
+    /// buffers this needs -- fallibly, since this is exactly the call that
+    /// aborted the process on Iris's phone in a release build with no
+    /// message beyond "wgpu error: Validation Error" (RUST.md's P0 box,
+    /// "iris bench crash on the phone, 2026-09-06"). wgpu's own default
+    /// behaviour for an uncaptured error is `panic!` with no caller able to
+    /// intervene, so every `create_bind_group_layout`/`create_render_pipeline`
+    /// call below runs inside three nested error scopes (one per
+    /// `ErrorFilter`) instead: whichever scope catches something, its
+    /// `wgpu::Error`'s `Display` is wgpu-core's own `format_error` output
+    /// (`"Validation Error\n\nCaused by:\n  ..."`, the same text the panic
+    /// would have printed before Android's crash reporter truncated it) and
+    /// becomes this function's `Err`. Both callers
+    /// (`android::render::AndroidRenderer::new`, `default::render::
+    /// UiRenderer::new`) already call `Device`-creation with
+    /// `pollster::block_on`, so returning a plain `Result` here rather than
+    /// making this `async fn` keeps that same synchronous shape.
+    pub fn new(
+        device: &Device,
+        queue: &Queue,
+        config: &SurfaceConfiguration,
+        window_size: impl Into<Vec2>,
+    ) -> Result<Self, String> {
+        // Popped in reverse of this order, once every creation call below
+        // has run -- `Device::push_error_scope`'s own contract.
+        let oom_scope = device.push_error_scope(ErrorFilter::OutOfMemory);
+        let validation_scope = device.push_error_scope(ErrorFilter::Validation);
+        let internal_scope = device.push_error_scope(ErrorFilter::Internal);
+
         let shader = device.create_shader_module(ShaderModuleDescriptor {
             label: Some("UI Shape Shader"),
             source: ShaderSource::Wgsl(SHAPE_SHADER.into()),
         });
 
-        // Seeded from the surface's own size, not `WindowUniform::default()`
-        // (0, 0): the vertex shader divides by `window.dim` to reach clip
-        // space, so a window this buffer disagrees with means every
-        // primitive's position is NaN/Inf and is dropped before
-        // rasterization -- the clear colour still reaches the screen (the
-        // pass runs regardless) while nothing drawn on top of it ever does.
-        // winit's backend gets away with the old default because winit
-        // fires an initial `WindowEvent::Resized` that calls `resize()`
-        // before the first frame; android-view has no such automatic
-        // event, so `AndroidRenderer::new` built a node whose window buffer
-        // was never corrected -- this is I2's "nothing draws" bug (RUST.md).
-        let window_uniform = WindowUniform {
-            width: config.width as f32,
-            height: config.height as f32,
+        // Seeded from the caller's own reported size, not
+        // `WindowUniform::default()` (0, 0): the vertex shader divides by
+        // `window.dim` to reach clip space, so a window this buffer
+        // disagrees with means every primitive's position is NaN/Inf and is
+        // dropped before rasterization -- the clear colour still reaches
+        // the screen (the pass runs regardless) while nothing drawn on top
+        // of it ever does. winit's backend gets away with the old default
+        // because winit fires an initial `WindowEvent::Resized` that calls
+        // `resize()` before the first frame; android-view has no such
+        // automatic event, so `AndroidRenderer::new` built a node whose
+        // window buffer was never corrected -- this is I2's "nothing draws"
+        // bug (RUST.md).
+        //
+        // **Deliberately not `config.width`/`config.height`**: those are
+        // the surface's *physical* pixel size, which the swapchain needs,
+        // but everything downstream of this uniform (layout, hit-testing,
+        // glyph/rect positions) works in the caller's own units -- on
+        // Android that's *logical* (physical / density) since RUST.md's P0
+        // box ("text is far too small"), on desktop it's whatever
+        // `default::render::UiRenderer::new` already divides by
+        // `window.scale_factor()`. Passing it in explicitly, rather than
+        // deriving it from `config` here, is what keeps this crate from
+        // needing to know either platform's notion of density at all.
+        let window_uniform = {
+            let size = window_size.into();
+            WindowUniform {
+                width: size.x,
+                height: size.y,
+            }
         };
         let window_buffer = device.create_buffer_init(&BufferInitDescriptor {
             label: Some("window"),
@@ -329,7 +472,18 @@ impl UiRenderNode {
             cache: None,
         });
 
-        Self {
+        // Reverse of the push order above. Only one of these should ever be
+        // `Some` in practice -- three separate scopes exist to name *which*
+        // kind of error it was, not because more than one is expected at
+        // once.
+        let internal_err = internal_scope.pop().block_on();
+        let validation_err = validation_scope.pop().block_on();
+        let oom_err = oom_scope.pop().block_on();
+        if let Some(err) = validation_err.or(oom_err).or(internal_err) {
+            return Err(err.to_string());
+        }
+
+        Ok(Self {
             uniform_group,
             primitive_layout,
             rsc_layout,
@@ -343,7 +497,7 @@ impl UiRenderNode {
             move_offsets,
             masks_layout,
             masks_group,
-        }
+        })
     }
 
     fn bind_group_0(
@@ -510,4 +664,26 @@ impl UiRenderNode {
     pub fn take_image_bind_group_creates(&mut self) -> u64 {
         self.textures.take_bind_group_creates()
     }
+
+    /// Atlas-array `grow_array` calls since the last call -- same calling
+    /// convention as `take_image_bind_group_creates` (call once per frame,
+    /// before `update()`, to read exactly the previous frame's tally). Part
+    /// of the Diagnostics page's per-frame report (RUST.md's P0 box, "the
+    /// first input frame" investigation): if a report ever shows a grow
+    /// landing on the same frame the glyphs vanished, that is the
+    /// coincidence to chase first.
+    pub fn take_atlas_pages_grown(&mut self) -> u64 {
+        self.textures.take_pages_grown()
+    }
+}
+
+/// What `UiRenderNode::update` changed this frame that a caller building a
+/// per-frame diagnostic report cares about -- see `take_image_bind_group_creates`/
+/// `take_atlas_pages_grown` for the two counters this doesn't carry (they
+/// use the existing "call before update()" convention instead, so as not
+/// to disturb `bench_images`' documented counts).
+#[derive(Clone, Copy, Debug, Default)]
+pub struct FrameUpdateStats {
+    pub masks_resized: bool,
+    pub moves_resized: bool,
 }

iris/core/src/render/texture.rs

@@ -67,6 +67,12 @@ pub struct GpuTextures {
     /// unchanging image list is zero, the same way `UiRenderState`'s
     /// `draw_count`/`region_mut_count` prove the layout side.
     bind_group_creates: u64,
+    /// `grow_array` calls since the last `take_pages_grown` -- the
+    /// Diagnostics page's per-frame report (RUST.md's P0 box, "the first
+    /// input frame" investigation) reads this alongside `bind_group_creates`
+    /// to say whether *this* frame's glyph disappearance, if any, coincided
+    /// with the atlas array being recreated.
+    pages_grown: u64,
 }
 
 impl GpuTextures {
@@ -226,6 +232,7 @@ impl GpuTextures {
     /// array's view, which invalidates every bind group that referenced it,
     /// so this also rebuilds all of them before returning.
     fn grow_array(&mut self, rsc_layout: &BindGroupLayout) {
+        self.pages_grown += 1;
         let new_capacity = self.array_capacity * 2;
         let new_texture = Self::create_array_texture(&self.device, new_capacity);
         if self.page_count > 0 {
@@ -392,6 +399,7 @@ impl GpuTextures {
             sampler,
             null_view,
             bind_group_creates: 0,
+            pages_grown: 0,
         }
     }
 
@@ -402,6 +410,12 @@ impl GpuTextures {
         std::mem::take(&mut self.bind_group_creates)
     }
 
+    /// Reads and zeroes the atlas-array-grow counter -- see `pages_grown`'s
+    /// field comment.
+    pub fn take_pages_grown(&mut self) -> u64 {
+        std::mem::take(&mut self.pages_grown)
+    }
+
     pub fn array_view(&self) -> &TextureView {
         &self.array_view
     }

iris/core/src/ui/painter.rs

@@ -165,8 +165,10 @@ impl<'a> Painter<'a> {
         attrs: &TextAttrs,
         width: Option<f32>,
     ) -> RenderedText {
+        let density = self.state.density;
         let ui = self.rsc.ui_mut();
-        ui.text.render(buffer, attrs, width, &mut ui.textures)
+        ui.text
+            .render(buffer, attrs, width, &mut ui.textures, density)
     }
 
     /// Draw a laid-out string: one quad per glyph, all sampling the atlas.
@@ -210,6 +212,12 @@ impl<'a> Painter<'a> {
         self.state.output_size
     }
 
+    /// Physical pixels per `dp` -- see `UiRenderState::density`'s field
+    /// doc. What `Len::dp`'s `apply_rest` call resolves against.
+    pub fn density(&self) -> f32 {
+        self.state.density
+    }
+
     pub fn px_size(&mut self) -> Vec2 {
         self.region.size().to_abs(self.state.output_size)
     }

iris/core/src/ui/render_state.rs

@@ -9,6 +9,12 @@ pub struct UiRenderState {
     pub active: HashMap<WidgetId, ActiveData>,
     pub layers: PrimitiveLayers,
     pub(super) output_size: Vec2,
+    /// Physical pixels per `dp` -- see `Len::dp`'s field doc. `1.0` (an
+    /// unscaled display) until a backend that knows its own density calls
+    /// `set_density` (Android's `content_scale`, read at `surface_changed`
+    /// time); the winit backend has no analogous per-monitor value wired up
+    /// yet and stays at the default.
+    pub(super) density: f32,
 
     old_root: Option<WidgetId>,
     resized: bool,
@@ -35,6 +41,7 @@ impl UiRenderState {
             active: Default::default(),
             layers: Default::default(),
             output_size: Vec2::ZERO,
+            density: 1.0,
             old_root: None,
             resized: false,
             draw_started: Default::default(),
@@ -60,6 +67,20 @@ impl UiRenderState {
         self.resized = true;
     }
 
+    /// Sets the physical-pixels-per-dp ratio every `Len::dp` in the tree
+    /// resolves against from the next layout pass on -- see `density`'s
+    /// field doc. Not folded into `resize` because the two change on
+    /// different triggers (a surface resize on every rotation or keyboard
+    /// open; a density change only if the app follows the display to a
+    /// different screen, which Android surfaces separately).
+    pub fn set_density(&mut self, density: f32) {
+        self.density = density;
+    }
+
+    pub fn density(&self) -> f32 {
+        self.density
+    }
+
     pub fn update<'a>(&mut self, root: impl Into<Option<&'a StrongWidget>>, rsc: &mut dyn UiRsc) {
         // safety mechanism for memory leaks; might wanna return a result instead so user can
         // decide whether to panic or not
@@ -311,7 +332,7 @@ impl UiRenderState {
         };
         let from = active
             .size
-            .to_uivec2()
+            .to_uivec2(self.density)
             .align(RegionAlign::TOP_LEFT)
             .within(&active.region);
         let slot = active.move_slot;

iris/desktop-app/src/app.rs

@@ -15,23 +15,19 @@
 //! +-----------+--------------------------------------+
 //! ```
 //!
-//! **Deliberately left simple, and why**: every incoming SSE event refolds
-//! the *entire* transcript (`client_core::transcript_fold::fold_event` is
-//! already `O(items)` and a desktop session's conversation is small) and
-//! rebuilds the whole right-hand widget tree from scratch, rather than
-//! reaching for `TranscriptScreen::push_row`'s incremental append.
-//! `push_row` cannot update a row already on screen -- only append a new
-//! one -- and a streaming assistant reply is exactly a row whose *text*
-//! keeps changing after it first appears (see `transcript-ui`'s own doc on
-//! `fold_event` folding deltas into one growing item). A full rebuild
-//! shows that growth correctly at the cost of redrawing everything each
-//! time; fine for this proof, wrong for a long, fast-streaming transcript
-//! -- the incremental path that fixes it needs `transcript-ui` to expose
-//! updating a row in place, which it does not yet. The composer's
-//! in-progress text survives a rebuild (`rebuild_transcript`'s
-//! `in_progress` local) since the user typing a followup while a reply
-//! streams in is the one case a naive rebuild would otherwise lose data
-//! on.
+//! **Incoming SSE events go through `TranscriptScreen::apply`**, not a
+//! full rebuild: `client_core::transcript_fold::fold_event` folds the new
+//! item list as before, then `apply` updates only the row(s) that actually
+//! changed (almost always the one still-open assistant message a delta
+//! landed in) instead of rebuilding the whole right-hand widget tree from
+//! scratch. `rebuild_transcript` still runs the whole tree once, for a
+//! freshly loaded/selected session and for `apply`'s own rare
+//! full-rebuild fallback (a `group_tool_runs` regroup touching a row
+//! before the tail). The composer's in-progress text survives a rebuild
+//! (`rebuild_transcript`'s `in_progress` local) since the user typing a
+//! followup while a reply streams in is the one case a naive rebuild
+//! would otherwise lose data on -- `apply`'s own path never touches the
+//! composer at all, so this only matters on the fallback.
 //!
 //! Background network I/O (`client_core::api`/`event_stream`, both
 //! blocking by design -- see `client-core`'s `Cargo.toml`) runs on plain
@@ -45,7 +41,9 @@
 
 use client_core::api::{ApiClient, SessionSummary, UreqTransport};
 use client_core::event_stream::{StreamItem, follow_session_events};
-use client_core::transcript_fold::{TranscriptItem, fold_event, group_tool_runs};
+use client_core::transcript_fold::{
+    TranscriptItem, fold_event, fold_page, group_tool_runs, raw_seq,
+};
 use event_model::SeqEvent;
 use iris::prelude::*;
 use std::sync::Arc;
@@ -207,8 +205,12 @@ impl DefaultAppState for Client {
                 event,
             } => {
                 if self.current(&session_id, generation) {
+                    let old_items = self.items.clone();
                     self.items = fold_event(&self.items, &event);
-                    self.rebuild_transcript(rsc);
+                    match &self.screen {
+                        Some(screen) => screen.apply(rsc, &old_items, &self.items),
+                        None => self.rebuild_transcript(rsc),
+                    }
                 }
             }
             AppEvent::StreamEnded {
@@ -421,118 +423,3 @@ fn placeholder(rsc: &mut DefaultRsc<Client>, message: &str) -> StrongWidget {
         .add_strong(rsc)
         .any()
 }
-
-/// Folds a page of raw transcript lines (`ApiClient::fetch_transcript_page`'s
-/// `Vec<Value>`) into the flat item list `client_core::transcript_fold`
-/// works over. A line this build can't parse fails the whole page rather
-/// than being skipped -- CODE_RULES's "an enumeration must be able to say
-/// 'it broke'" -- since silently dropping one event could hide, say, the
-/// user message the composer is about to look like it never sent.
-fn fold_page(values: &[serde_json::Value]) -> Result<Vec<TranscriptItem>, String> {
-    let mut items = Vec::new();
-    for value in values {
-        let event: SeqEvent = serde_json::from_value(value.clone()).map_err(|e| {
-            format!("the server sent a transcript line this build couldn't parse: {e}")
-        })?;
-        items = fold_event(&items, &event);
-    }
-    Ok(items)
-}
-
-/// The wire `seq` a raw transcript line carries -- see `select_session`'s
-/// comment on why the live-stream cursor has to be this, not a folded
-/// item's `seq()`.
-fn raw_seq(value: &serde_json::Value) -> Option<u64> {
-    value.get("seq")?.as_u64()
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    fn line(seq: u64, json: serde_json::Value) -> serde_json::Value {
-        let mut obj = json;
-        obj["seq"] = serde_json::json!(seq);
-        obj["ts"] = serde_json::json!(1.0);
-        obj
-    }
-
-    /// The regression for the bug a real `run-headless.sh` screenshot
-    /// found (see `select_session`'s comment): resuming the live stream
-    /// from the last *item's* seq re-delivers the deltas already folded
-    /// into a still-open assistant message, doubling its tail. `raw_seq`
-    /// of the last wire line must be the true high-water mark instead,
-    /// which for a run of deltas is higher than every item's own `seq()`.
-    #[test]
-    fn the_resume_cursor_is_the_last_wire_seq_not_the_last_items_seq() {
-        let values = vec![
-            line(1, serde_json::json!({"type": "userMessage", "text": "hi"})),
-            line(
-                2,
-                serde_json::json!({"type": "assistantText", "delta": "a"}),
-            ),
-            line(
-                3,
-                serde_json::json!({"type": "assistantText", "delta": "b"}),
-            ),
-            line(
-                4,
-                serde_json::json!({"type": "assistantText", "delta": "c"}),
-            ),
-        ];
-        let after = raw_seq(values.last().unwrap()).unwrap();
-        assert_eq!(after, 4);
-
-        let items = fold_page(&values).unwrap();
-        // The folded item keeps the *first* delta's seq (2), which is
-        // exactly the value that must not be used as the resume cursor.
-        let assistant_seq = items
-            .iter()
-            .find(|i| matches!(i, TranscriptItem::AssistantMsg { .. }))
-            .unwrap()
-            .seq();
-        assert_eq!(assistant_seq, 2);
-        assert_ne!(
-            after, assistant_seq,
-            "the fixed bug: these must differ here"
-        );
-    }
-
-    #[test]
-    fn a_page_folds_into_one_settled_assistant_message() {
-        let values = vec![
-            line(1, serde_json::json!({"type": "userMessage", "text": "hi"})),
-            line(
-                2,
-                serde_json::json!({"type": "assistantText", "delta": "hel"}),
-            ),
-            line(
-                3,
-                serde_json::json!({"type": "assistantText", "delta": "lo"}),
-            ),
-        ];
-        let items = fold_page(&values).unwrap();
-        assert_eq!(
-            items,
-            vec![
-                TranscriptItem::UserMsg {
-                    seq: 1,
-                    text: "hi".to_string(),
-                    attachments: Vec::new(),
-                },
-                TranscriptItem::AssistantMsg {
-                    seq: 2,
-                    text: "hello".to_string(),
-                    settled: false,
-                },
-            ]
-        );
-    }
-
-    #[test]
-    fn an_unparseable_line_fails_the_whole_page() {
-        let values = vec![serde_json::json!({"seq": 1, "ts": 1.0, "type": "not-a-real-type"})];
-        let err = fold_page(&values).unwrap_err();
-        assert!(err.contains("couldn't parse"));
-    }
-}

iris/examples/message_list.rs

@@ -68,12 +68,15 @@ fn build_row<Rsc: UiRsc + 'static>(rsc: &mut Rsc, i: usize) -> StrongWidget {
         let mut span = Span::empty(Dir::DOWN);
         span.push(text);
         span.push(img);
-        span.pad(8.0).background(rect(tint)).add_strong(rsc).any()
+        span.pad(dp(8.0))
+            .background(rect(tint))
+            .add_strong(rsc)
+            .any()
     } else {
         wtext(row_text(i))
             .wrap(true)
             .color(text_color)
-            .pad(8.0)
+            .pad(dp(8.0))
             .background(rect(tint))
             .add_strong(rsc)
             .any()

iris/src/android/mod.rs

@@ -23,7 +23,8 @@ mod view;
 pub use insets::Insets;
 pub use render::AndroidRenderer;
 pub use view::{
-    AndroidAppState, AndroidRsc, AndroidUiState, HasAndroidUiState, IrisViewPeer, new_peer,
+    AndroidAppState, AndroidRsc, AndroidUiState, HasAndroidUiState, IrisViewPeer, WindowInsets,
+    new_peer,
 };
 
 /// Registers the extra native methods this backend needs beyond what

iris/src/android/render.rs

@@ -6,6 +6,7 @@ use android_view::{
 };
 use iris_core::{UiData, UiRenderNode, UiRenderState};
 use pollster::FutureExt;
+use std::time::{Duration, Instant};
 use wgpu::{
     rwh::{DisplayHandle, HandleError, HasDisplayHandle, HasWindowHandle, WindowHandle},
     *,
@@ -47,12 +48,78 @@ pub struct AndroidRenderer {
     config: SurfaceConfiguration,
     encoder: CommandEncoder,
     pub ui: UiRenderNode,
+    /// The adapter identity, kept past `new()` for the Diagnostics page --
+    /// `Adapter` itself is not `Clone`, so the three fields the page shows
+    /// are copied out once here rather than holding the adapter.
+    pub adapter_name: String,
+    pub adapter_backend: Backend,
+    pub adapter_driver: String,
+    /// Every uncaptured wgpu error since this renderer was created -- see
+    /// `iris_core::WgpuErrorLog`'s doc comment. Installed on `device` in
+    /// `new()`, kept here so the Diagnostics page and the per-frame log in
+    /// `update()` can both read it without a global.
+    pub wgpu_errors: iris_core::WgpuErrorLog,
+    /// Frames drawn on this surface -- what gates the first-10-frames log
+    /// `update()` writes (RUST.md's P0 box, "the first input frame"
+    /// investigation): a fresh surface is exactly what Iris's own report
+    /// says renders correctly at first, so the frames that matter are the
+    /// first several after each `surface_changed`, not an arbitrary window
+    /// during a long-running session.
+    frame_count: u64,
+    /// Physical pixels per dp -- see `android::view::AndroidUiState::
+    /// content_scale`'s field comment for what this feeds.
+    content_scale: f32,
+}
+
+/// One frame's worth of the counters `render/mod.rs`'s doc comments on
+/// `FrameUpdateStats`/`take_image_bind_group_creates`/
+/// `take_atlas_pages_grown` describe -- assembled here because the three
+/// live on two different calling conventions (`FrameUpdateStats` from this
+/// exact `update()` call; the other two describe the *previous* frame,
+/// same as `bench_images`' existing use of them) and a diagnostic reader
+/// should not have to know that split.
+#[derive(Clone, Copy, Debug, Default)]
+pub struct FrameDiagnostics {
+    pub masks_resized: bool,
+    pub moves_resized: bool,
+    /// From the previous frame's `update()` -- see the struct doc.
+    pub atlas_pages_grown_prev: u64,
+    pub image_bind_group_creates_prev: u64,
 }
 
 impl AndroidRenderer {
-    pub fn new(window: NativeWindow, width: u32, height: u32) -> Self {
+    /// `Err` holds a full, human-readable report -- wgpu's own error text
+    /// (`UiRenderNode::new`'s doc comment) plus the adapter identity and
+    /// the limits/downlevel flags bind-group-layout validation checks
+    /// against -- rather than the panic wgpu's default error handler would
+    /// otherwise raise with no caller able to see it. This is what aborted
+    /// the P0 bench APK on Iris's phone with only "wgpu error: Validation
+    /// Error" surviving into the crash report (RUST.md's P0 box, "iris
+    /// bench crash on the phone, 2026-09-06"): `create_bind_group_layout`
+    /// validates against *this* adapter's downlevel capabilities and
+    /// limits, which a desktop GPU and the emulator's software renderers
+    /// never exercised. The caller (`android::view::IrisViewPeer::
+    /// surface_changed`) logs this one-line-flattened and shows it on
+    /// screen instead of aborting the process.
+    pub fn new(
+        window: NativeWindow,
+        width: u32,
+        height: u32,
+        content_scale: f32,
+    ) -> Result<Self, String> {
+        // `force-gles` (RUST.md's I5 "Where iris's frame time goes") swaps
+        // the software-Vulkan (SwiftShader) path for GLES/virgl on the same
+        // build, to isolate whether the backend itself explains the frame
+        // time gap against Compose. `cfg!` rather than a runtime switch:
+        // there is no way to hand an env var to an already-launched Android
+        // process on this machine (see the feature's doc in Cargo.toml).
+        let backends = if cfg!(feature = "force-gles") {
+            Backends::GL
+        } else {
+            Backends::PRIMARY
+        };
         let instance = Instance::new(&InstanceDescriptor {
-            backends: Backends::PRIMARY,
+            backends,
             ..Default::default()
         });
 
@@ -72,19 +139,54 @@ impl AndroidRenderer {
             .block_on()
             .expect("Could not get adapter!");
 
+        // Requesting the device itself still panics on failure: that is a
+        // `RequestDeviceError` (a limit or feature the adapter cannot grant
+        // at all), a different and already-diagnosable failure from the one
+        // this function now recovers from -- `RUST.md`'s "Software mode ...
+        // crashes for a third, different reason" is exactly that class, and
+        // its message already names the limit and the requested/allowed
+        // values with no truncation risk (it never reaches wgpu's
+        // uncaptured-error path). What this function's `Result` return
+        // covers is the *next* class of failure: the adapter grants the
+        // device, and validation only fails once a specific bind group
+        // layout is checked against it.
+
         // Same request as the winit backend's `UiRenderer::new` -- no
         // binding-array features, see TEXTURES.md's "Recommended shape".
+        // `iris_core::device_limits()` is shared between the two backends;
+        // see its own doc for why it is not simply `Limits::default()`.
         let (device, queue) = adapter
             .request_device(&DeviceDescriptor {
-                required_limits: Limits {
-                    max_buffer_size: 1 << 30,
-                    ..Default::default()
-                },
+                required_limits: iris_core::device_limits(),
                 ..Default::default()
             })
             .block_on()
             .expect("Could not get device!");
 
+        // wgpu's default handler for an error raised outside `UiRenderNode::
+        // new`'s own error scopes (i.e. everything past device creation --
+        // an ordinary frame's `update`/`draw`) is `panic!`, unconditionally,
+        // with no caller able to intervene: the same mechanism that aborted
+        // the P0 bench APK once already, just at a different call site. Log
+        // and record instead of letting that default stand -- RUST.md's P0
+        // box, "every wgpu uncaptured error ... it must never panic in
+        // release".
+        let wgpu_errors = iris_core::WgpuErrorLog::default();
+        let wgpu_errors_for_handler = wgpu_errors.clone();
+        device.on_uncaptured_error(std::sync::Arc::new(move |error| {
+            log::error!("iris wgpu uncaptured error: {error}");
+            wgpu_errors_for_handler.record(error);
+        }));
+
+        let info = adapter.get_info();
+        let adapter_name = info.name.clone();
+        let adapter_backend = info.backend;
+        let adapter_driver = if info.driver_info.is_empty() {
+            info.driver.clone()
+        } else {
+            format!("{} {}", info.driver, info.driver_info)
+        };
+
         let surface_caps = surface.get_capabilities(&adapter);
         let surface_format = surface_caps
             .formats
@@ -106,16 +208,121 @@ impl AndroidRenderer {
         surface.configure(&device, &config);
 
         let encoder = Self::create_encoder(&device);
-        let ui = UiRenderNode::new(&device, &queue, &config);
+        // Physical pixels, matching the swapchain's own `width`/`height`
+        // exactly -- see `android::view::AndroidUiState::content_scale`'s
+        // field comment for why this is no longer divided into a separate
+        // logical space (that stopgap is what made text blurry, RUST.md's
+        // P0 box). `Len::dp` folds the density in at layout time instead,
+        // so nothing here needs to know it at all.
+        let window_size = iris_core::util::Vec2::new(width as f32, height as f32);
+        let ui = match UiRenderNode::new(&device, &queue, &config, window_size) {
+            Ok(ui) => ui,
+            Err(wgpu_error) => return Err(Self::diagnostic(&adapter, &wgpu_error)),
+        };
 
-        Self {
+        Ok(Self {
             surface,
             device,
             queue,
             config,
             encoder,
             ui,
-        }
+            adapter_name,
+            adapter_backend,
+            adapter_driver,
+            wgpu_errors,
+            frame_count: 0,
+            content_scale,
+        })
+    }
+
+    /// The adapter identity plus every limit and downlevel flag
+    /// `create_bind_group_layout` validates a storage buffer or texture
+    /// binding against, followed by wgpu's own error text -- everything a
+    /// person reading this off a screenshot needs to tell "this adapter
+    /// lacks X" from "this is a bug in the layout." Named explicitly rather
+    /// than `{limits:?}`/`{flags:?}` wholesale, because `Limits` alone is
+    /// dozens of fields nobody asked for -- these are exactly the ones
+    /// `UiRenderNode::new`'s layouts (`rsc_layout`, `masks_layout`,
+    /// `primitive_layout`) can fail against, per `CreateBindGroupLayoutError`
+    /// (`wgpu-core::binding_model`) and its downlevel-flag checks
+    /// (`wgpu-core::device::resource`, `VERTEX_STORAGE` in particular --
+    /// the one storage buffer here, `move_offsets`, that is visible to the
+    /// vertex stage).
+    fn diagnostic(adapter: &Adapter, wgpu_error: &str) -> String {
+        let info = adapter.get_info();
+        let limits = adapter.limits();
+        let downlevel = adapter.get_downlevel_capabilities();
+        format!(
+            "iris could not start rendering. Copy this text and send it to Iris.\n\n\
+             adapter: {name} ({backend:?}), driver: {driver} {driver_info}\n\
+             limits: max_storage_buffers_per_shader_stage={max_storage_buffers} \
+             max_sampled_textures_per_shader_stage={max_sampled_textures} \
+             max_bind_groups={max_bind_groups} \
+             max_bindings_per_bind_group={max_bindings} \
+             max_storage_buffer_binding_size={max_storage_binding} \
+             min_storage_buffer_offset_alignment={min_storage_align}\n\
+             downlevel flags: {flags:?}\n\n\
+             {wgpu_error}",
+            name = info.name,
+            backend = info.backend,
+            driver = info.driver,
+            driver_info = info.driver_info,
+            max_storage_buffers = limits.max_storage_buffers_per_shader_stage,
+            max_sampled_textures = limits.max_sampled_textures_per_shader_stage,
+            max_bind_groups = limits.max_bind_groups,
+            max_bindings = limits.max_bindings_per_bind_group,
+            max_storage_binding = limits.max_storage_buffer_binding_size,
+            min_storage_align = limits.min_storage_buffer_offset_alignment,
+            flags = downlevel.flags,
+        )
+    }
+
+    /// The Diagnostics page's whole report: adapter identity, font
+    /// resolution, the atlas's own view count, every uncaptured wgpu error
+    /// so far, and the frame report -- RUST.md's P0 box, "a named
+    /// `Diagnostics` control ... adapter info, limits, fonts found, atlas
+    /// format/pages, wgpu errors so far, frame report". One string rather
+    /// than a struct the caller formats, since the only consumer is a
+    /// plain `TextView` with a "copy this and send it to Iris" affordance,
+    /// the same shape `surface_changed`'s crash report already uses
+    /// (UI_RULES.md: a failure -- or here, a state worth reporting --
+    /// carries enough to act on where it's shown).
+    pub fn diagnostics_report(
+        &self,
+        font: &iris_core::FontDiagnostics,
+        frame_report: &str,
+    ) -> String {
+        let errors = self.wgpu_errors.snapshot();
+        let errors_text = if errors.is_empty() {
+            "none".to_string()
+        } else {
+            errors.join("\n  ")
+        };
+        format!(
+            "iris diagnostics. Copy this text and send it to Iris.\n\n\
+             adapter: {name} ({backend:?}), driver: {driver}\n\
+             content_scale: {content_scale}\n\
+             atlas format: Rgba8Unorm, views live: {views}\n\
+             fonts: {families_found} families found, default={default_family:?} \
+             mono={default_mono_family:?}\n\
+             fonts resolved: regular={regular:?} bold={bold:?} italic={italic:?} \
+             mono={mono:?}\n\
+             wgpu errors since surface creation:\n  {errors_text}\n\n\
+             {frame_report}",
+            name = self.adapter_name,
+            backend = self.adapter_backend,
+            driver = self.adapter_driver,
+            content_scale = self.content_scale,
+            views = self.ui.view_count(),
+            families_found = font.families_found,
+            default_family = font.default_family,
+            default_mono_family = font.default_mono_family,
+            regular = font.regular_resolved,
+            bold = font.bold_resolved,
+            italic = font.italic_resolved,
+            mono = font.mono_resolved,
+        )
     }
 
     fn create_encoder(device: &Device) -> CommandEncoder {
@@ -124,11 +331,45 @@ impl AndroidRenderer {
         })
     }
 
-    pub fn update(&mut self, ui: &mut UiData, render: &mut UiRenderState) {
-        self.ui.update(&self.device, &self.queue, ui, render);
+    /// Returns what changed this frame -- see `FrameDiagnostics`'s doc
+    /// comment for why two of its four fields describe the *previous*
+    /// frame rather than this one. `IrisViewPeer::render` logs this for
+    /// the first `DIAGNOSTIC_FRAMES` frames after each `surface_changed`,
+    /// per RUST.md's P0 box ("the first input frame" investigation): the
+    /// glyph-wipe Iris reported happens on the first tap or scroll after a
+    /// fresh surface, so that is exactly the window a report needs to
+    /// cover, not an arbitrary slice of a long session.
+    pub fn update(&mut self, ui: &mut UiData, render: &mut UiRenderState) -> FrameDiagnostics {
+        let atlas_pages_grown_prev = self.ui.take_atlas_pages_grown();
+        let image_bind_group_creates_prev = self.ui.take_image_bind_group_creates();
+        let stats = self.ui.update(&self.device, &self.queue, ui, render);
+        self.frame_count += 1;
+        FrameDiagnostics {
+            masks_resized: stats.masks_resized,
+            moves_resized: stats.moves_resized,
+            atlas_pages_grown_prev,
+            image_bind_group_creates_prev,
+        }
     }
 
-    pub fn draw(&mut self) {
+    /// Frames drawn on this surface so far -- see `frame_count`'s field
+    /// comment.
+    pub fn frame_count(&self) -> u64 {
+        self.frame_count
+    }
+
+    /// Draws and presents one frame, returning the time spent in
+    /// `queue.submit` plus `present()` -- wherever a driver/GPU/compositor
+    /// wait would actually show up. The caller (`android::view::render`)
+    /// already times the whole frame from its own `redraw_to_submit` start;
+    /// subtracting this from that total is `redraw_to_submit` itself
+    /// (layout, text, primitive building, and this method's own render-pass
+    /// recording). RUST.md's I5 "Where iris's frame time goes" diagnosis,
+    /// added 2026-09-05 -- see `iris_core::FrameReport::record_split`'s own
+    /// doc for the caveat this shares: `present()` is not fenced against
+    /// the GPU actually finishing, so this is "how long the CPU was blocked
+    /// handing the frame off", not confirmed GPU time.
+    pub fn draw(&mut self) -> Duration {
         let output = self.surface.get_current_texture().unwrap();
         let view = output
             .texture
@@ -151,27 +392,54 @@ impl AndroidRenderer {
             self.ui.draw(render_pass);
         }
 
+        let submit_start = Instant::now();
         self.queue.submit(std::iter::once(encoder.finish()));
         output.present();
+        submit_start.elapsed()
     }
 
+    /// Physical pixels -- the unit layout and hit-testing use, matching
+    /// the window uniform's own units. See
+    /// `android::view::AndroidUiState::content_scale`'s field comment.
     pub fn size(&self) -> iris_core::util::Vec2 {
-        (self.config.width, self.config.height).into()
+        iris_core::util::Vec2::new(self.config.width as f32, self.config.height as f32)
     }
 
+    /// Reconfigures the surface and rewrites the window uniform for a new
+    /// physical size -- deliberately the *only* two things this does.
+    /// `device`, `ui`'s atlas, buffers and bind groups are untouched, so a
+    /// call here (as opposed to a fresh `AndroidRenderer::new`) never
+    /// invalidates a glyph the CPU-side cache already placed in the atlas.
+    /// See `android::view::IrisViewPeer::surface_changed`'s doc comment for
+    /// why that distinction matters -- it is what keeps text on screen
+    /// across an IME resize.
     pub fn resize(&mut self, width: u32, height: u32) {
         self.config.width = width;
         self.config.height = height;
         self.surface.configure(&self.device, &self.config);
-        self.ui.resize((width, height), &self.queue);
+        let size = iris_core::util::Vec2::new(width as f32, height as f32);
+        self.ui.resize(size, &self.queue);
     }
 }
 
 /// `Tasks`' redraw handle on Android: a background task finishes on the
 /// tokio thread `Tasks::init` spawned, which is not attached to the JVM, so
-/// asking for a frame means attaching first. `post_frame_callback` needs a
-/// live `View` reference; the global ref is what survives past the JNI call
-/// that handed it to us.
+/// asking for a frame means attaching first. The global ref is what
+/// survives past the JNI call that handed the `View` to us.
+///
+/// **Goes through `View::post_delayed`, not `post_frame_callback`
+/// directly** -- found the hard way (RUST.md's I5 Android integration):
+/// `post_frame_callback`'s Java side calls `Choreographer.getInstance()`,
+/// which throws `IllegalStateException` unless the *calling* thread already
+/// has a `Looper` (`Choreographer.getInstance()`'s own contract). A tokio
+/// worker thread, even freshly attached to the JVM, has none -- the crash
+/// was a `JavaException` inside `View::post_frame_callback`'s `.unwrap()`,
+/// aborting the process on the second `redraw.request_redraw()` any
+/// android transcript-screen fetch made. `View.postDelayed(Runnable, 0)`
+/// is the ordinary Android answer to "queue work onto a View's own UI
+/// thread from any thread" and needs no Looper of its own; `delayed_callback`
+/// below is what that Runnable resolves to on the UI thread, where a real
+/// `post_frame_callback` is safe again.
 pub struct AndroidRedrawHandle {
     vm: JavaVM,
     view: GlobalRef,
@@ -189,6 +457,6 @@ impl RequestRedraw for AndroidRedrawHandle {
             return;
         };
         let local = env.new_local_ref(&self.view).unwrap();
-        View(local).post_frame_callback(&mut env);
+        View(local).post_delayed(&mut env, 0);
     }
 }

iris/src/android/view.rs

@@ -4,7 +4,11 @@ use accesskit_android::Adapter as AccessAdapter;
 use android_view::{
     AccessibilityNodeInfo, AccessibilityNodeProvider, Bundle, CallbackCtx, Context,
     InputConnection, KeyEvent, MotionEvent, Rect, View, ViewPeer,
-    jni::{JNIEnv, sys::jint},
+    jni::{
+        JNIEnv, JavaVM,
+        objects::{GlobalRef, JValue},
+        sys::jint,
+    },
     ndk::event::{Keycode, MotionAction},
 };
 // `marker::Sized` explicitly: `crate::prelude::*` below also brings in the
@@ -29,6 +33,10 @@ use super::{
 /// `Option` because a `SurfaceView`'s surface does not outlive backgrounding
 /// the way a winit `Window` does -- `surfaceDestroyed`/`surfaceCreated` can
 /// happen any number of times over the life of one `IrisViewPeer`.
+/// How many frames after each `surface_changed` `render()` logs a full
+/// diagnostic line for -- see the log site's own comment.
+const DIAGNOSTIC_FRAMES: u64 = 10;
+
 pub struct AndroidUiState {
     pub root: Option<StrongWidget>,
     pub renderer: Option<AndroidRenderer>,
@@ -57,10 +65,46 @@ pub struct AndroidUiState {
     /// The AccessKit tree itself -- see `iris_core::AccessTree`'s doc
     /// comment.
     pub access: AccessTree,
+    /// iris's own frame-time report (RUST.md's I5 box, "Measurements
+    /// taken" (b)) -- `render()` below records into it once per frame,
+    /// because `dumpsys gfxinfo` cannot see a `SurfaceView`'s own
+    /// GPU-drawn frames at all. See `iris_core::FrameReport`'s own doc.
+    pub frame_report: FrameReport,
+    /// `DisplayMetrics.density` (`new_peer`'s doc comment): physical pixels
+    /// per dp on this device, read once at view construction and carried
+    /// on `UiRenderState::density` (`render.set_density`, `new_peer`) from
+    /// then on -- every `Len::dp` in the widget tree resolves against it at
+    /// layout time (`Len::dp`'s field doc, IRIS_TODO.md's
+    /// "density-independent length unit" item, 2026-09-06).
+    ///
+    /// **Everything else in this module is physical pixels, matching the
+    /// real wgpu surface/swapchain resolution** -- window size, touch
+    /// coordinates, insets. That is a correction from an earlier version
+    /// of this comment, which had `window_size`/`surface_changed`'s
+    /// `UiRenderState::resize` call divide by `content_scale` into a
+    /// *logical* coordinate space instead, as a global stopgap for
+    /// RUST.md's P0 box's phone report ("text is far too small"). That
+    /// stopgap fixed the size but not the *sharpness*: dividing to logical
+    /// units meant a `16.0`-sized glyph rasterised at 16 physical px and
+    /// then implicitly upscaled ~3x by the NDC mapping onto the real
+    /// physical framebuffer -- the exact "blurry ... glyphs drawn at
+    /// logical size and stretched by the scale" Iris reported next.
+    /// Resolving `dp` at layout time replaces it: a widget author writes
+    /// `dp(16)` for a size that should look the same physical size on any
+    /// density, and everything downstream (layout, hit-testing, the window
+    /// uniform, and the font size handed to the text shaper) works in the
+    /// display's own physical pixels throughout, so nothing is
+    /// rasterised at one resolution and displayed at another.
+    pub content_scale: f32,
+    /// The last insets `render()` saw -- compared each frame so
+    /// `AndroidAppState::on_insets_changed` fires only when they actually
+    /// change (once at startup for the status bar, again if the device
+    /// rotates), not every frame.
+    last_insets: Insets,
 }
 
 impl AndroidUiState {
-    fn new(shared: Rc<RefCell<Shared>>) -> Self {
+    fn new(shared: Rc<RefCell<Shared>>, content_scale: f32) -> Self {
         Self {
             root: None,
             renderer: None,
@@ -72,6 +116,9 @@ impl AndroidUiState {
             shared,
             access_adapter: Default::default(),
             access: AccessTree::new(),
+            frame_report: FrameReport::new(),
+            content_scale,
+            last_insets: Insets::default(),
         }
     }
 
@@ -101,6 +148,61 @@ pub trait AndroidAppState: HasAndroidUiState {
     fn back_pressed(&mut self, rsc: &mut AndroidRsc<Self>, render: &mut UiRenderState) -> bool {
         false
     }
+    /// Called once, right after `new`, with a fresh `JavaVM` handle and a
+    /// global reference to this app's own `View` -- for a caller that
+    /// needs to call into Java itself beyond what a [`RequestRedraw`]
+    /// handle already covers (P0's bench build calling
+    /// `BatteryManager`/`ClipboardManager` through the view's `Context`,
+    /// docs/RUST.md). Not folded into `new` itself: most implementors need
+    /// nothing here, and `new`'s job is building the widget tree, not
+    /// holding a platform handle -- the default does nothing. `vm`/`view`
+    /// are independent handles from the ones `new_peer` keeps for its own
+    /// `RequestRedraw` (a fresh `get_java_vm`/`new_global_ref` each), so
+    /// storing them has no effect on that mechanism.
+    #[allow(unused_variables)]
+    fn platform_ready(&mut self, rsc: &mut AndroidRsc<Self>, vm: JavaVM, view: GlobalRef) {}
+    /// Called from `render()` whenever `AndroidUiState::insets()` differs
+    /// from what it was last frame -- once at startup for the status bar
+    /// (RUST.md's P0 box: "the status-bar inset is not applied" reported
+    /// the two top buttons sitting under it, because nothing read `.top`
+    /// at all), and again on a rotation or the keyboard opening/closing.
+    /// `insets` is in the same physical-pixel units everything else in the
+    /// tree now uses (`AndroidUiState::content_scale`'s field comment), so
+    /// a widget can add it to a layout size directly -- `dp(...) +
+    /// abs(insets.top)` if the widget wants a density-independent size
+    /// plus the system bar's own (already-physical) height. The default
+    /// does nothing -- most screens have no chrome that sits under a
+    /// system bar.
+    #[allow(unused_variables)]
+    fn on_insets_changed(&mut self, rsc: &mut AndroidRsc<Self>, insets: WindowInsets) {}
+}
+
+/// `insets::Insets` as `f32`, for the widget-facing callback above -- a
+/// distinct type from `insets::Insets` so a caller of `on_insets_changed`
+/// is not coupled to that module's own (`i32`, JNI-shaped) representation.
+/// Both are physical pixels; this used to divide by `content_scale` into a
+/// separate *logical* unit (hence the old name, `LogicalInsets`), back when
+/// the rest of layout was logical too -- see `AndroidUiState::content_scale`'s
+/// field comment for why that stopgap is gone.
+#[derive(Clone, Copy, Default, Debug, PartialEq)]
+pub struct WindowInsets {
+    pub left: f32,
+    pub top: f32,
+    pub right: f32,
+    pub bottom: f32,
+    pub ime_bottom: f32,
+}
+
+impl WindowInsets {
+    fn from_physical(insets: Insets) -> Self {
+        Self {
+            left: insets.left as f32,
+            top: insets.top as f32,
+            right: insets.right as f32,
+            bottom: insets.bottom as f32,
+            ime_bottom: insets.ime_bottom as f32,
+        }
+    }
 }
 
 /// The android-view analogue of `default::DefaultRsc` -- identical in
@@ -247,10 +349,23 @@ impl<State: AndroidAppState> IrisViewPeer<State> {
     /// these in until that is root-caused; removing them loses the exact
     /// evidence a `logcat` capture needs to reproduce the state.
     fn render(&mut self, ctx: &mut CallbackCtx) {
-        let ui_state = self.state.android_state();
-        if ui_state.renderer.is_none() {
+        if self.state.android_state().renderer.is_none() {
             return;
         }
+        // See `AndroidAppState::on_insets_changed`'s doc comment: fires
+        // exactly when insets actually differ from last frame, not every
+        // frame -- most frames this is one `Insets` equality check against
+        // a `Copy` struct. Done before `ui_state` is bound below, since
+        // `on_insets_changed` needs `&mut self.state`/`&mut self.rsc` both.
+        let ui_state = self.state.android_state();
+        let current_insets = ui_state.insets();
+        if current_insets != ui_state.last_insets {
+            let physical = WindowInsets::from_physical(current_insets);
+            self.state.android_state_mut().last_insets = current_insets;
+            self.state.on_insets_changed(&mut self.rsc, physical);
+        }
+
+        let ui_state = self.state.android_state();
         log::debug!(
             "render(): root={:?} widgets={} active={} root_px={:?} out_size={:?}",
             ui_state.root.is_some(),
@@ -262,14 +377,45 @@ impl<State: AndroidAppState> IrisViewPeer<State> {
                 .and_then(|r| self.render.window_region(r, &self.rsc)),
             self.window_size(),
         );
+        // iris's own frame-time report (RUST.md's I5 box, "Measurements
+        // taken" (b)): started here, at the same point a redraw request
+        // fires, and stopped after `renderer.draw()`'s `queue.submit` +
+        // `present()` -- the span Compose's render report and `gfxinfo`
+        // both count. See `iris_core::FrameReport`'s own doc for exactly
+        // what this does and does not measure.
+        let frame_start = Instant::now();
         let ui_state = self.state.android_state_mut();
         self.render.update(&ui_state.root, &mut self.rsc);
         let ui_state = self.state.android_state_mut();
         let Some(renderer) = &mut ui_state.renderer else {
             return;
         };
-        renderer.update(&mut self.rsc.ui, &mut self.render);
-        renderer.draw();
+        let frame_diagnostics = renderer.update(&mut self.rsc.ui, &mut self.render);
+        // First `DIAGNOSTIC_FRAMES` frames after each `surface_changed`
+        // only -- RUST.md's P0 box, "the first input frame" investigation:
+        // the glyph-wipe Iris reported happens on the first tap or scroll
+        // after a fresh surface, so a report from that window is what
+        // would show whether an atlas grow, a masks/move_offsets resize, or
+        // a fresh wgpu error coincided with it. `frame_count()` was just
+        // incremented inside `update()`, so `<=` counts frame 1 through
+        // `DIAGNOSTIC_FRAMES` inclusive.
+        if renderer.frame_count() <= DIAGNOSTIC_FRAMES {
+            log::info!(
+                "iris frame diagnostics: frame={} masks_resized={} moves_resized={} \
+                 atlas_pages_grown_prev={} image_bind_group_creates_prev={} wgpu_errors={}",
+                renderer.frame_count(),
+                frame_diagnostics.masks_resized,
+                frame_diagnostics.moves_resized,
+                frame_diagnostics.atlas_pages_grown_prev,
+                frame_diagnostics.image_bind_group_creates_prev,
+                renderer.wgpu_errors.snapshot().len(),
+            );
+        }
+        let submit_to_present = renderer.draw();
+        self.state
+            .android_state_mut()
+            .frame_report
+            .record_split(frame_start.elapsed(), submit_to_present);
         let ui_state = self.state.android_state();
         log::debug!(
             "render(): after update active={} root_px={:?}",
@@ -307,6 +453,31 @@ fn show_soft_input<'local>(env: &mut JNIEnv<'local>, view: &View<'local>) {
     imm.show_soft_input(env, view, 0);
 }
 
+/// Replaces the activity's content with a plain, selectable, scrollable
+/// text view holding `report` -- the on-screen half of `surface_changed`'s
+/// renderer-failure path (UI_RULES.md: "a failure is reported where it
+/// happened, and says what to do next," here "copy this and send it").
+/// Goes through an ordinary instance method on the Java side
+/// (`IrisView.showRendererError`) rather than a new `native` method: this
+/// call is Rust reaching *into* Java, the opposite direction from every
+/// `native fn` android-view/`IrisView` declare, and an ordinary virtual
+/// call resolves against `ctx.view`'s real runtime class (`IrisView`) the
+/// same way any other JNI method call here does. Silently does nothing on
+/// any JNI failure -- there is no more-fallback screen to fall back to,
+/// and the `log::error!` in `surface_changed` already reached logcat
+/// first.
+fn show_renderer_error<'local>(env: &mut JNIEnv<'local>, view: &View<'local>, report: &str) {
+    let Ok(message) = env.new_string(report) else {
+        return;
+    };
+    let _ = env.call_method(
+        &view.0,
+        "showRendererError",
+        "(Ljava/lang/String;)V",
+        &[JValue::Object(message.as_ref())],
+    );
+}
+
 impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
     fn on_key_down<'local>(
         &mut self,
@@ -349,6 +520,8 @@ impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
     ) -> bool {
         self.drain_tasks();
         let action = event.action_masked(&mut ctx.env);
+        // Device (physical) pixels, same space layout now uses throughout
+        // -- see `AndroidUiState::content_scale`'s field comment.
         let x = event.x(&mut ctx.env);
         let y = event.y(&mut ctx.env);
         let ui_state = self.state.android_state_mut();
@@ -401,7 +574,6 @@ impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
         height: i32,
     ) {
         self.drain_tasks();
-        let window = holder.surface(&mut ctx.env).to_native_window(&mut ctx.env);
         // The layout engine's own notion of the canvas size is separate
         // from the wgpu surface's -- winit's backend sets it from
         // `WindowEvent::Resized`, and there is no equivalent automatic
@@ -410,13 +582,101 @@ impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
         // nothing but the clear colour: the widget tree laid out against
         // whatever size `UiRenderState::new` starts at instead of the
         // surface's real one.
-        self.render.resize((width as u32, height as u32));
-        // Drop the old renderer (and the surface it owns) before building
-        // one from the new window -- see `AndroidRenderer`'s doc comment.
-        let ui_state = self.state.android_state_mut();
-        ui_state.renderer = None;
-        ui_state.renderer = Some(AndroidRenderer::new(window, width as u32, height as u32));
-        self.render(ctx);
+        //
+        // **Physical pixels, matching `AndroidRenderer`'s own
+        // `size()`/`resize()`/`new()`** -- `AndroidUiState::content_scale`'s
+        // field comment. This call sets `UiRenderState::output_size`, which
+        // every `rel`/`rest` length resolves against and every `abs`
+        // pixel-region compares to directly; a `dp(56)` height now folds
+        // in the density at `Len::apply_rest` time instead of this call
+        // dividing the whole window into a separate logical space, which
+        // is what used to make every `abs`-unit size (a fixed `.height(56)`
+        // in particular) mean something different from a `rest`-based one.
+        self.render.resize((width as f32, height as f32));
+
+        // **Reuse the existing renderer (device, atlas, buffers, bind
+        // groups) when one is already live -- only reconfigure the
+        // surface.** `surfaceChanged` fires on *every* size or format
+        // change, not only on a genuinely new `Surface`/window: showing
+        // the IME under `adjustResize` resizes the same `SurfaceView` and
+        // is reported through this exact callback. Rebuilding the whole
+        // `AndroidRenderer` here used to mean a fresh `UiRenderNode::new`
+        // -- a brand-new, empty glyph atlas and fresh GPU buffers -- while
+        // `iris_core`'s CPU-side glyph cache (`primitive/text.rs`) kept the
+        // atlas coordinates it had already handed out against the *old*
+        // atlas. Every glyph then drew from a UV rectangle that pointed
+        // into a texture that had just been recreated empty, so text
+        // vanished on the first keyboard open while rects (which never go
+        // through the atlas) kept drawing -- exactly the "rectangles stay,
+        // glyphs disappear" Iris reported. Confirmed by reading this path
+        // end to end (no fresh-atlas rebuild anywhere in `resize()` below,
+        // only in `AndroidRenderer::new`) before changing anything, per
+        // AGENTS.md's "verify before finishing".
+        //
+        // `AndroidRenderer::resize` only reconfigures the wgpu surface and
+        // rewrites the window uniform -- device, atlas, buffers and bind
+        // groups are untouched, so the glyph cache's coordinates stay
+        // valid. A genuinely new surface (after `surface_destroyed`, e.g.
+        // backgrounding) still goes through `AndroidRenderer::new` below,
+        // since `renderer` is `None` in that case.
+        let already_live = self.state.android_state().renderer.is_some();
+        if already_live {
+            let ui_state = self.state.android_state_mut();
+            ui_state
+                .renderer
+                .as_mut()
+                .expect("checked Some above")
+                .resize(width as u32, height as u32);
+            self.render(ctx);
+            return;
+        }
+
+        let window = holder.surface(&mut ctx.env).to_native_window(&mut ctx.env);
+        // `AndroidRenderer::new` used to panic here through wgpu's own
+        // default uncaptured-error handler on a bind-group-layout
+        // validation failure -- exactly what aborted the P0 bench APK on
+        // Iris's phone with the message truncated to "wgpu error:
+        // Validation Error" and nothing else recoverable from the crash
+        // report (RUST.md's P0 box, "iris bench crash on the phone,
+        // 2026-09-06"). It now returns the full diagnostic instead; this is
+        // the one place in the app that can turn it into something a
+        // person can read, since `ctx.view`/`ctx.env` (needed to reach the
+        // Java side) are only in scope inside a `ViewPeer` callback.
+        //
+        // `content_scale` reaches `AndroidRenderer` only for the
+        // Diagnostics page's report text now -- window size and the
+        // shader's window uniform are physical pixels throughout (see the
+        // `resize` call above), not divided by it.
+        let content_scale = self.state.android_state().content_scale;
+        match AndroidRenderer::new(window, width as u32, height as u32, content_scale) {
+            Ok(renderer) => {
+                self.state.android_state_mut().renderer = Some(renderer);
+                self.render(ctx);
+            }
+            Err(report) => {
+                // One line for logcat (UI_RULES.md: "the full text for
+                // whoever can read the log" lives here), the multi-line
+                // original on screen -- `show_renderer_error` below.
+                log::error!("iris renderer init failed: {}", report.replace('\n', " | "));
+                // Deferred, not called directly: `Activity::setContentView`
+                // tears the old view hierarchy down synchronously, which
+                // fires `IrisView`'s own `onFocusChanged` before
+                // `setContentView` returns -- straight back into this same
+                // `IrisViewPeer` through `on_focus_changed` while
+                // `with_peer` (android-view's dispatch, `view.rs` upstream)
+                // still holds this peer's `RefCell` borrow for the
+                // `surface_changed` call in progress. Found by inducing a
+                // validation error and hitting `RefCell already borrowed`
+                // at exactly that reentrant call (RUST.md's P0 box).
+                // `push_dynamic_deferred_callback` runs after `with_peer`
+                // drops the borrow, which is what every other callback in
+                // this file that reaches into Java already relies on
+                // (`raise_if_enabled`, above).
+                ctx.push_dynamic_deferred_callback(move |env, view| {
+                    show_renderer_error(env, view, &report);
+                });
+            }
+        }
     }
 
     fn surface_destroyed<'local>(
@@ -432,6 +692,20 @@ impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
         self.render(ctx);
     }
 
+    /// Where `AndroidRedrawHandle::request_redraw` (`android/render.rs`)
+    /// actually lands: `View.postDelayed`'s Runnable resolves to this, on
+    /// the UI thread, which is what makes it safe to call from a background
+    /// task's own thread when `post_frame_callback`'s `Choreographer`
+    /// requirement (a `Looper` on the *calling* thread) is not. Same body
+    /// as `do_frame` -- draining tasks and rendering immediately is a
+    /// perfectly good answer to "a background fetch has new state," and
+    /// avoids a second frame-scheduling path to keep in sync with the real
+    /// one.
+    fn delayed_callback(&mut self, ctx: &mut CallbackCtx) {
+        self.drain_tasks();
+        self.render(ctx);
+    }
+
     fn as_input_connection(&mut self) -> Option<&mut dyn InputConnection> {
         Some(self)
     }
@@ -513,10 +787,19 @@ impl<State: AndroidAppState> AccessibilityNodeProvider for IrisViewPeer<State> {
 /// `register_view_class`, which wants a plain function pointer) -- see
 /// `iris/android-app/src/lib.rs`.
 pub fn new_peer<'local, State: AndroidAppState>(
-    env: JNIEnv<'local>,
+    mut env: JNIEnv<'local>,
     view: View<'local>,
-    _context: Context<'local>,
+    context: Context<'local>,
 ) -> android_view::jni::sys::jlong {
+    // `DisplayMetrics.density` -- physical pixels per dp on this device.
+    // Read once here, at the one point in this file already handed a
+    // `Context`, and carried on `AndroidUiState` from then on (see
+    // `content_scale`'s field comment for what depends on it).
+    let content_scale = context
+        .resources(&mut env)
+        .display_metrics(&mut env)
+        .density(&mut env);
+    log::info!("iris: new_peer content_scale={content_scale}");
     let vm = env.get_java_vm().unwrap();
     let global_view = env.new_global_ref(&view.0).unwrap();
     let redraw: Arc<dyn RequestRedraw> = Arc::new(AndroidRedrawHandle::new(vm, global_view));
@@ -528,12 +811,22 @@ pub fn new_peer<'local, State: AndroidAppState>(
         state: Default::default(),
         _state: PhantomData,
     };
+    // See `TextData::density`'s field doc for why this is set alongside
+    // `render.set_density` below rather than read from there.
+    rsc.ui.text.density = content_scale;
     let shared = Rc::new(RefCell::new(Shared::default()));
-    let ui_state = AndroidUiState::new(shared.clone());
-    let state = State::new(ui_state, &mut rsc);
+    let ui_state = AndroidUiState::new(shared.clone(), content_scale);
+    let mut state = State::new(ui_state, &mut rsc);
+    let platform_vm = env.get_java_vm().unwrap();
+    let platform_view = env.new_global_ref(&view.0).unwrap();
+    state.platform_ready(&mut rsc, platform_vm, platform_view);
+    let mut render = UiRenderState::new();
+    // Every `Len::dp` in the tree resolves against this from now on -- see
+    // `UiRenderState::density`'s field doc and `Len::dp`'s.
+    render.set_density(content_scale);
     let peer = IrisViewPeer {
         rsc,
-        render: UiRenderState::new(),
+        render,
         state,
         task_recv,
     };

iris/src/default/input.rs

@@ -11,10 +11,15 @@ pub struct Input {
 }
 
 impl Input {
-    pub fn event(&mut self, event: &WindowEvent) -> bool {
+    /// `scale_factor` converts winit's physical-pixel event coordinates
+    /// into the same logical units `UiRenderNode`'s window uniform now uses
+    /// (`default::render::UiRenderer::new`'s doc comment) -- without it,
+    /// a cursor position and the widget tree it's tested against would be
+    /// in two different units on any monitor whose scale factor isn't 1.0.
+    pub fn event(&mut self, event: &WindowEvent, scale_factor: f32) -> bool {
         match event {
             WindowEvent::CursorMoved { position, .. } => {
-                self.cursor.pos = Vec2::new(position.x as f32, position.y as f32);
+                self.cursor.pos = Vec2::new(position.x as f32, position.y as f32) / scale_factor;
                 self.cursor.exists = true;
             }
             WindowEvent::MouseInput { state, button, .. } => {
@@ -30,7 +35,9 @@ impl Input {
             WindowEvent::MouseWheel { delta, .. } => {
                 let mut delta = match *delta {
                     MouseScrollDelta::LineDelta(x, y) => Vec2::new(x, y),
-                    MouseScrollDelta::PixelDelta(pos) => Vec2::new(pos.x as f32, pos.y as f32),
+                    MouseScrollDelta::PixelDelta(pos) => {
+                        Vec2::new(pos.x as f32, pos.y as f32) / scale_factor
+                    }
                 };
                 if delta.x == 0.0 && self.modifiers.shift {
                     delta.x = delta.y;
@@ -68,8 +75,13 @@ impl Input {
 
 impl DefaultUiState {
     pub fn window_size(&self) -> Vec2 {
-        let size = self.renderer.window().inner_size();
-        (size.width, size.height).into()
+        let window = self.renderer.window();
+        let size = window.inner_size();
+        let scale_factor = window.scale_factor() as f32;
+        Vec2::new(
+            size.width as f32 / scale_factor,
+            size.height as f32 / scale_factor,
+        )
     }
 
     pub fn cursor_state(&self) -> &CursorState {

iris/src/default/mod.rs

@@ -246,7 +246,8 @@ impl<State: DefaultAppState> AppState for DefaultApp<State> {
         ui_state
             .access_adapter
             .process_event(&ui_state.window, &event);
-        let input_changed = ui_state.input.event(&event);
+        let scale_factor = ui_state.renderer.window().scale_factor() as f32;
+        let input_changed = ui_state.input.event(&event, scale_factor);
         let cursor_state = ui_state.cursor_state().clone();
         let old = ui_state.focus;
         if cursor_state.buttons.left.is_start() {

iris/src/default/render.rs

@@ -1,5 +1,5 @@
 use crate::task::RequestRedraw;
-use iris_core::{UiData, UiRenderNode, UiRenderState};
+use iris_core::{UiData, UiRenderNode, UiRenderState, util::Vec2};
 use pollster::FutureExt;
 use std::sync::Arc;
 use wgpu::*;
@@ -66,7 +66,13 @@ impl UiRenderer {
         self.config.width = size.width;
         self.config.height = size.height;
         self.surface.configure(&self.device, &self.config);
-        self.ui.resize((size.width, size.height), &self.queue);
+        // Logical, matching `new`'s own seed -- see the comment there.
+        let scale_factor = self.window.scale_factor() as f32;
+        let logical = Vec2::new(
+            size.width as f32 / scale_factor,
+            size.height as f32 / scale_factor,
+        );
+        self.ui.resize(logical, &self.queue);
     }
 
     fn create_encoder(device: &Device) -> CommandEncoder {
@@ -102,13 +108,12 @@ impl UiRenderer {
         // needs descriptor indexing. See TEXTURES.md's "Recommended shape"
         // for why the old binding array asked for
         // VK_EXT_descriptor_indexing unconditionally and did not survive a
-        // real share of Android GPUs.
+        // real share of Android GPUs. `iris_core::device_limits()` is
+        // shared with the Android backend; see its own doc for why it is
+        // not simply `Limits::default()`.
         let (device, queue) = adapter
             .request_device(&DeviceDescriptor {
-                required_limits: Limits {
-                    max_buffer_size: 1 << 30,
-                    ..Default::default()
-                },
+                required_limits: iris_core::device_limits(),
                 ..Default::default()
             })
             .block_on()
@@ -142,7 +147,28 @@ impl UiRenderer {
 
         let encoder = Self::create_encoder(&device);
 
-        let ui = UiRenderNode::new(&device, &queue, &config);
+        // Unlike the Android backend, the desktop backend has no on-screen
+        // fallback to show a diagnostic through, so a renderer-creation
+        // failure still panics here -- but now with wgpu's full "Caused
+        // by:" chain as the message, since `UiRenderNode::new` returns it
+        // rather than letting wgpu's own default handler panic first (see
+        // that function's doc comment).
+        // Logical size (physical / `scale_factor`), matching what the
+        // Android backend now reports too (`android::render::
+        // AndroidRenderer::new`, `content_scale`) -- the swapchain still
+        // configures at the real physical resolution above; only the
+        // window uniform layout/hit-testing agree on is scaled. Without
+        // this a window on any monitor whose scale factor isn't 1.0 would
+        // have the identical "everything too small" bug RUST.md's P0 box
+        // found on Iris's phone, just never noticed here because this
+        // crate's own dev monitors happen to run at 1.0.
+        let scale_factor = window.scale_factor() as f32;
+        let logical_size = Vec2::new(
+            size.width as f32 / scale_factor,
+            size.height as f32 / scale_factor,
+        );
+        let ui = UiRenderNode::new(&device, &queue, &config, logical_size)
+            .expect("Could not create iris render node!");
 
         Self {
             surface,

iris/src/sense.rs

@@ -1,5 +1,6 @@
 use crate::prelude::*;
 use std::{
+    collections::VecDeque,
     ops::{BitOr, Deref, DerefMut},
     rc::Rc,
     time::{Duration, Instant},
@@ -444,8 +445,31 @@ impl DragArbiter {
         self.state = ArbiterState::Undecided { already_selected };
     }
 
+    /// Whether this arbiter has no press in flight -- either it has never
+    /// seen [`Self::press_start`], or the last one it saw was released.
+    /// What a caller whose own `PressStart` sense can miss (see
+    /// [`Self::update`]'s doc) uses to notice that a `Pressing` frame has
+    /// arrived with no matching start, and recover by starting one now.
+    pub fn is_idle(&self) -> bool {
+        matches!(self.state, ArbiterState::Idle)
+    }
+
     /// The press continues (still down) at `pos`. Call once per frame
     /// while the button/finger is down; returns what this frame means.
+    ///
+    /// A caller must not call this while [`Self::is_idle`] is true for a
+    /// press that is genuinely still down -- `Idle` has no way to tell
+    /// "no press is happening" from "a press is happening but this
+    /// arbiter never got its `press_start`," so it always answers
+    /// `Undecided` and never leaves `Idle` on its own. That second case is
+    /// real: a touch's `ACTION_DOWN` lands whatever pixel the finger
+    /// actually hit, which is not guaranteed to be inside the same
+    /// row-local sensor region a later `ACTION_MOVE` in the same gesture
+    /// lands in (a row's own padding/gap, or its non-selectable header, is
+    /// pointer-transparent to `CursorSense`) -- so the widget that
+    /// receives the gesture's first `Pressing` frame may never have seen
+    /// its `PressStart`. `iris::transcript_ui::selection::Selection::drag`
+    /// is the caller that recovers from this, via `is_idle`.
     pub fn update(&mut self, pos: Vec2, now: Instant) -> DragOutcome {
         match self.state {
             ArbiterState::Idle => DragOutcome::Undecided,
@@ -468,7 +492,25 @@ impl DragArbiter {
                 } else if dy.abs() > DRAG_SLOP && dy.abs() >= dx.abs() {
                     self.state = ArbiterState::Panning;
                     self.last = pos;
-                    DragOutcome::Pan(dy)
+                    // `dy` here is the *whole* drag since `press_start`,
+                    // not since the last frame -- nothing panned while
+                    // `Undecided` was withholding the slop, so applying it
+                    // in full on this one frame is a visible jump the
+                    // instant `DRAG_SLOP` is crossed (IRIS_TODO.md's
+                    // "scrolling down sometimes jitters the text," root-
+                    // caused by tracing `List`'s per-frame offset against
+                    // a synthetic monotonic drag: the offset held flat for
+                    // every `Undecided` frame, then stepped by several
+                    // frames' worth of motion at once on the frame slop
+                    // was crossed, before resuming ordinary per-frame
+                    // deltas). Only the excess past the slop threshold is
+                    // real, undecided motion the reader hasn't seen
+                    // reflected yet -- so only that excess is applied now,
+                    // the same way Android's own touch handling consumes
+                    // `ViewConfiguration.getScaledTouchSlop()` once from
+                    // the first scroll past it rather than replaying the
+                    // whole pre-threshold drag in one step.
+                    DragOutcome::Pan(dy - DRAG_SLOP.copysign(dy))
                 } else if now.duration_since(self.origin_at) >= LONG_PRESS
                     && dx.abs() <= DRAG_SLOP
                     && dy.abs() <= DRAG_SLOP
@@ -487,6 +529,390 @@ impl DragArbiter {
     pub fn release(&mut self) {
         self.state = ArbiterState::Idle;
     }
+
+    /// Whether the arbiter's current gesture (if any) has committed to
+    /// panning -- what a caller checks at release time to decide whether
+    /// to hand the tracked velocity to [`crate::widget::List::fling`], per
+    /// IRIS_TODO.md's "swiping has no momentum": a fling must only follow
+    /// a pan, never a text selection that happened to end with the finger
+    /// still moving.
+    pub fn is_panning(&self) -> bool {
+        matches!(self.state, ArbiterState::Panning)
+    }
+}
+
+/// How far back a [`VelocityTracker`] looks when estimating a fling's
+/// initial speed -- Android's own `VelocityTracker` defaults to a similar
+/// short window so a gesture's last flick dominates over its slower start.
+const VELOCITY_WINDOW: Duration = Duration::from_millis(100);
+
+/// Tracks a drag's speed along one axis from its last ~100ms of motion, so
+/// a release can be handed a realistic initial velocity for
+/// [`AndroidFlingSpline`]/[`FlingCalculator`] rather than a single frame's
+/// noisy last delta. Fed one timestamped pan delta per frame
+/// (`add_sample`, the same `dy`/`-dy` quantity `DragArbiter::update`'s
+/// `Pan` outcome already carries) and answers `velocity()` in units per
+/// second, matching whatever unit the deltas were in.
+#[derive(Default)]
+pub struct VelocityTracker {
+    /// `(when, delta)` pairs, oldest first, trimmed to `VELOCITY_WINDOW`
+    /// on every `add_sample` -- so this never grows past however many
+    /// frames land in that window.
+    samples: VecDeque<(Instant, f32)>,
+}
+
+impl VelocityTracker {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Forget everything -- called on a fresh press, so a new gesture's
+    /// velocity is never contaminated by the tail of the previous one.
+    pub fn reset(&mut self) {
+        self.samples.clear();
+    }
+
+    /// Record one frame's motion. `delta` is this frame's movement since
+    /// the last sample, not a cumulative position.
+    pub fn add_sample(&mut self, delta: f32, at: Instant) {
+        self.samples.push_back((at, delta));
+        while let Some(&(when, _)) = self.samples.front() {
+            if at.duration_since(when) > VELOCITY_WINDOW {
+                self.samples.pop_front();
+            } else {
+                break;
+            }
+        }
+    }
+
+    /// The estimated speed, in units-per-second, over whatever samples
+    /// currently fall inside the tracking window: total motion divided by
+    /// the elapsed time between the oldest and newest sample still held.
+    /// `0.0` with fewer than two samples (no time span to divide by).
+    pub fn velocity(&self) -> f32 {
+        if self.samples.len() < 2 {
+            return 0.0;
+        }
+        let total: f32 = self.samples.iter().map(|&(_, d)| d).sum();
+        let span = self
+            .samples
+            .back()
+            .unwrap()
+            .0
+            .duration_since(self.samples.front().unwrap().0)
+            .as_secs_f32();
+        if span <= 0.0 { 0.0 } else { total / span }
+    }
+}
+
+/// Android's fling deceleration curve, ported from AOSP's
+/// `android.widget.OverScroller.SplineOverScroller` (the same curve
+/// Compose's `androidx.compose.ui.gestures.AndroidFlingSpline` and
+/// `androidx.compose.foundation.gestures.FlingCalculator` reuse) so a
+/// fling here travels the same distance a Compose `LazyColumn`'s own
+/// `ScrollableDefaults.flingBehavior()` would for the same initial
+/// velocity -- RUST.md's "Benchmark v2" box asked the two apps' fling
+/// phase to be comparable, and IRIS_TODO.md's "swiping has no momentum"
+/// asked for the same physics a reader's muscle memory already expects
+/// from every other Android scroll view.
+///
+/// The curve is a cubic-Bezier-derived spline sampled into two lookup
+/// tables at start-up (`SPLINE`, built once via [`std::sync::OnceLock`]):
+/// `SPLINE_POSITION[i]`/`SPLINE_TIME[i]` give the fraction of total
+/// distance/time elapsed at the `i`th of 100 even steps along the curve's
+/// own parameter. A lookup at an arbitrary time fraction interpolates
+/// between the two bracketing samples.
+mod android_fling_spline {
+    use std::sync::OnceLock;
+
+    const NB_SAMPLES: usize = 100;
+    /// Where the two cubic tension lines cross (AOSP's own constant name
+    /// and value, `SplineOverScroller.INFLEXION`).
+    pub(super) const INFLEXION: f32 = 0.35;
+    const START_TENSION: f32 = 0.5;
+    const END_TENSION: f32 = 1.0;
+    const P1: f32 = START_TENSION * INFLEXION;
+    const P2: f32 = 1.0 - END_TENSION * (1.0 - INFLEXION);
+
+    pub(super) struct Spline {
+        position: [f32; NB_SAMPLES + 1],
+        time: [f32; NB_SAMPLES + 1],
+    }
+
+    fn build() -> Spline {
+        let mut position = [0.0f32; NB_SAMPLES + 1];
+        let mut time = [0.0f32; NB_SAMPLES + 1];
+        let (mut x_min, mut y_min) = (0.0f32, 0.0f32);
+        for i in 0..NB_SAMPLES {
+            let alpha = i as f32 / NB_SAMPLES as f32;
+
+            let mut x_max = 1.0f32;
+            let (mut x, mut coef);
+            loop {
+                x = x_min + (x_max - x_min) / 2.0;
+                coef = 3.0 * x * (1.0 - x);
+                let tx = coef * ((1.0 - x) * START_TENSION + x * END_TENSION) + x * x * x;
+                if (tx - alpha).abs() < 1e-5 {
+                    break;
+                }
+                if tx > alpha {
+                    x_max = x;
+                } else {
+                    x_min = x;
+                }
+            }
+            position[i] = coef * ((1.0 - x) * P1 + x * P2) + x * x * x;
+
+            let mut y_max = 1.0f32;
+            let (mut y, mut coef_y);
+            loop {
+                y = y_min + (y_max - y_min) / 2.0;
+                coef_y = 3.0 * y * (1.0 - y);
+                let dy = coef_y * ((1.0 - y) * START_TENSION + y * END_TENSION) + y * y * y;
+                if (dy - alpha).abs() < 1e-5 {
+                    break;
+                }
+                if dy > alpha {
+                    y_max = y;
+                } else {
+                    y_min = y;
+                }
+            }
+            time[i] = coef_y * ((1.0 - y) * P1 + y * P2) + y * y * y;
+        }
+        position[NB_SAMPLES] = 1.0;
+        time[NB_SAMPLES] = 1.0;
+        Spline { position, time }
+    }
+
+    static SPLINE: OnceLock<Spline> = OnceLock::new();
+
+    /// The fraction of total distance covered at `time_fraction` (0..=1
+    /// of the fling's total duration). Finds the bracketing samples in
+    /// `SPLINE_TIME` and interpolates linearly between their matching
+    /// `SPLINE_POSITION` entries, exactly as AOSP's `SplineOverScroller
+    /// .flingPosition` does.
+    pub(super) fn distance_fraction(time_fraction: f32) -> f32 {
+        let spline = SPLINE.get_or_init(build);
+        let t = time_fraction.clamp(0.0, 1.0);
+        let index = ((t * NB_SAMPLES as f32) as usize).min(NB_SAMPLES - 1);
+        let t_inf = spline.time[index];
+        let t_sup = spline.time[index + 1];
+        let d_inf = spline.position[index];
+        let d_sup = spline.position[index + 1];
+        let span = t_sup - t_inf;
+        if span <= 0.0 {
+            d_inf
+        } else {
+            d_inf + (d_sup - d_inf) * (t - t_inf) / span
+        }
+    }
+}
+
+/// AOSP `SplineOverScroller`'s two other physical constants: the default
+/// `ViewConfiguration.getScrollFriction()` and the deceleration rate a
+/// friction of `0.84` per frame at 60Hz corresponds to
+/// (`ln(0.78)/ln(0.9)`, `SplineOverScroller.DECELERATION_RATE`).
+const FLING_FRICTION: f32 = 0.015;
+fn deceleration_rate() -> f32 {
+    (0.78f32.ln()) / (0.9f32.ln())
+}
+const GRAVITY_EARTH: f32 = 9.80665;
+
+/// Turns an initial fling velocity into a total travel distance and
+/// duration, following AOSP `SplineOverScroller`'s own closed-form
+/// formulas (`getSplineFlingDistance`/the duration half of `fling()`) --
+/// ported the same way Compose's `FlingCalculator` is, including its
+/// `density`-dependent physical coefficient (`computeDeceleration`,
+/// `GravityEarth * 39.37 * density * 160 * friction`). Density and
+/// velocity/distance units cancel algebraically as long as velocity and
+/// the returned distance share one pixel space (physical or logical) --
+/// [`crate::widget::List::fling`] relies on exactly that cancellation to
+/// avoid needing a display density of its own, since iris's `List`
+/// already works in logical (density-independent) pixels throughout.
+pub struct FlingCalculator {
+    physical_coefficient: f32,
+}
+
+impl FlingCalculator {
+    pub fn new(density: f32) -> Self {
+        Self {
+            physical_coefficient: GRAVITY_EARTH * 39.37 * density * 160.0 * FLING_FRICTION,
+        }
+    }
+
+    fn deceleration_for(&self, velocity: f32) -> f32 {
+        (android_fling_spline::INFLEXION * velocity.abs()
+            / (FLING_FRICTION * self.physical_coefficient))
+            .ln()
+    }
+
+    /// Total signed distance the fling travels before settling, in the
+    /// same pixel units `velocity` was given in.
+    pub fn distance(&self, velocity: f32) -> f32 {
+        if velocity == 0.0 {
+            return 0.0;
+        }
+        let l = self.deceleration_for(velocity);
+        let rate = deceleration_rate();
+        let magnitude =
+            FLING_FRICTION * self.physical_coefficient * (rate / (rate - 1.0) * l).exp();
+        magnitude.copysign(velocity)
+    }
+
+    /// How long the fling takes to settle.
+    pub fn duration(&self, velocity: f32) -> Duration {
+        if velocity == 0.0 {
+            return Duration::ZERO;
+        }
+        let l = self.deceleration_for(velocity);
+        let rate = deceleration_rate();
+        Duration::from_secs_f32((l / (rate - 1.0)).exp())
+    }
+
+    /// The signed distance covered by `elapsed` into a fling of this
+    /// `velocity` that started at `t0` -- what a per-frame ticker
+    /// (`List::tick_fling`) calls to find how far to have scrolled by now.
+    /// Clamped to the full `distance()` once `elapsed` reaches
+    /// `duration()`, so a caller need not special-case "past the end."
+    pub fn position_at(&self, velocity: f32, elapsed: Duration) -> f32 {
+        let duration = self.duration(velocity);
+        if duration.is_zero() {
+            return 0.0;
+        }
+        let fraction = (elapsed.as_secs_f32() / duration.as_secs_f32()).min(1.0);
+        self.distance(velocity) * android_fling_spline::distance_fraction(fraction)
+    }
+}
+
+#[cfg(test)]
+mod velocity_tracker_tests {
+    use super::*;
+    use std::sync::LazyLock;
+
+    // A single fixed base rather than a fresh `Instant::now()` per call --
+    // computing it once per test keeps every sample's spacing exact
+    // instead of at the mercy of however long the test itself takes to
+    // run between calls, the same reasoning `drag_arbiter_tests::t` uses.
+    static BASE: LazyLock<Instant> = LazyLock::new(Instant::now);
+
+    fn t(ms: u64) -> Instant {
+        *BASE + Duration::from_millis(ms)
+    }
+
+    #[test]
+    fn fewer_than_two_samples_reports_zero() {
+        let mut v = VelocityTracker::new();
+        assert_eq!(v.velocity(), 0.0);
+        v.add_sample(10.0, t(0));
+        assert_eq!(v.velocity(), 0.0);
+    }
+
+    #[test]
+    fn a_steady_drag_reports_its_own_speed() {
+        // 5px every 10ms, 11 samples spanning 100ms, sums to 55px over
+        // 0.1s -- 550px/s by this tracker's own "sum of deltas over the
+        // span between the oldest and newest held sample" definition.
+        let mut v = VelocityTracker::new();
+        for i in 0..=10 {
+            v.add_sample(5.0, t(i * 10));
+        }
+        assert!((v.velocity() - 550.0).abs() < 1.0, "got {}", v.velocity());
+    }
+
+    #[test]
+    fn only_the_last_100ms_of_samples_count() {
+        // An old, fast burst well outside the window followed by a slow,
+        // steady drag should report the recent speed, not the average of
+        // both -- otherwise a flick that trails off would still fling at
+        // its earlier, faster speed. The burst sits 110ms before the last
+        // sample, just past the 100ms window, so it is evicted.
+        let mut v = VelocityTracker::new();
+        v.add_sample(1000.0, t(0)); // will be 110ms old by the last sample
+        for i in 1..=11 {
+            v.add_sample(1.0, t(i * 10)); // 1px/10ms = 100px/s
+        }
+        assert!(
+            (v.velocity() - 110.0).abs() < 5.0,
+            "old burst leaked into the window: got {}",
+            v.velocity()
+        );
+    }
+
+    #[test]
+    fn reset_forgets_prior_samples() {
+        let mut v = VelocityTracker::new();
+        v.add_sample(500.0, t(0));
+        v.add_sample(500.0, t(10));
+        assert!(v.velocity() != 0.0);
+        v.reset();
+        assert_eq!(v.velocity(), 0.0);
+    }
+}
+
+#[cfg(test)]
+mod fling_calculator_tests {
+    use super::*;
+
+    #[test]
+    fn zero_velocity_flings_nowhere() {
+        let calc = FlingCalculator::new(1.0);
+        assert_eq!(calc.distance(0.0), 0.0);
+        assert_eq!(calc.duration(0.0), Duration::ZERO);
+    }
+
+    #[test]
+    fn distance_grows_with_velocity_and_keeps_its_sign() {
+        let calc = FlingCalculator::new(2.75); // a typical phone's density
+        let d_slow = calc.distance(2000.0);
+        let d_fast = calc.distance(12000.0);
+        assert!(d_slow > 0.0);
+        assert!(d_fast > d_slow);
+        assert_eq!(calc.distance(-12000.0), -d_fast);
+    }
+
+    /// Summing the spline's own per-frame position deltas across the
+    /// whole fling has to land within 1% of the closed-form `distance()`
+    /// -- this is the guarantee that `List::tick_fling`'s per-frame reads
+    /// of `position_at` actually add up to the total the fling promised,
+    /// not merely that the two formulas look plausible independently.
+    #[test]
+    fn integrating_position_at_matches_the_closed_form_distance() {
+        let calc = FlingCalculator::new(1.0);
+        for velocity in [1500.0f32, 5000.0, 12000.0, -12000.0] {
+            let total = calc.distance(velocity);
+            let duration = calc.duration(velocity);
+            let final_position = calc.position_at(velocity, duration);
+            let err = (final_position - total).abs() / total.abs();
+            assert!(
+                err < 0.01,
+                "velocity {velocity}: position_at(duration)={final_position} vs distance()={total}, err={err}"
+            );
+        }
+    }
+
+    #[test]
+    fn position_at_is_monotonic_and_clamped_past_the_end() {
+        let calc = FlingCalculator::new(1.0);
+        let velocity = 12000.0f32;
+        let duration = calc.duration(velocity);
+        let total = calc.distance(velocity);
+        let mut last = 0.0;
+        let mut t = Duration::ZERO;
+        while t < duration {
+            let p = calc.position_at(velocity, t);
+            assert!(p >= last - 0.01, "position went backwards at {t:?}");
+            last = p;
+            t += Duration::from_millis(16);
+        }
+        // Well past the end, it stays pinned at the total -- a caller
+        // must be able to ask "where would this fling be" without first
+        // checking whether it has already settled.
+        assert_eq!(
+            calc.position_at(velocity, duration + Duration::from_secs(5)),
+            total
+        );
+    }
 }
 
 #[cfg(test)]
@@ -511,9 +937,13 @@ mod drag_arbiter_tests {
     fn a_vertical_drag_pans_immediately() {
         let mut a = DragArbiter::new();
         a.press_start(Vec2::new(0.0, 0.0), t(0), false);
+        // The transition frame applies only the motion past `DRAG_SLOP`
+        // (20 - 8 = 12), not the full 20px since `press_start` -- see the
+        // `Pan` arm's own comment for why replaying the whole withheld
+        // drag in one step is the scroll-jitter bug this guards against.
         assert_eq!(
             a.update(Vec2::new(0.0, 20.0), t(10)),
-            DragOutcome::Pan(20.0)
+            DragOutcome::Pan(12.0)
         );
         // Subsequent frames keep panning, by the delta since last frame.
         assert_eq!(
@@ -522,6 +952,22 @@ mod drag_arbiter_tests {
         );
     }
 
+    /// Direct regression test for the fix: a slow drag that crosses
+    /// `DRAG_SLOP` by only a fraction of a pixel must not still produce a
+    /// visible jump -- the amount applied on the crossing frame should
+    /// itself shrink toward zero as the crossing gets closer to exactly
+    /// `DRAG_SLOP`, rather than always dumping the whole pre-threshold
+    /// distance at once.
+    #[test]
+    fn crossing_the_slop_by_a_little_pans_by_a_little() {
+        let mut a = DragArbiter::new();
+        a.press_start(Vec2::new(0.0, 0.0), t(0), false);
+        assert_eq!(
+            a.update(Vec2::new(0.0, DRAG_SLOP + 0.5), t(10)),
+            DragOutcome::Pan(0.5)
+        );
+    }
+
     #[test]
     fn a_horizontal_drag_with_nothing_selected_does_not_select() {
         let mut a = DragArbiter::new();
@@ -580,10 +1026,54 @@ mod drag_arbiter_tests {
         a.press_start(Vec2::new(0.0, 0.0), t(0), true);
         assert_eq!(
             a.update(Vec2::new(0.0, 20.0), t(10)),
-            DragOutcome::Pan(20.0)
+            DragOutcome::Pan(12.0)
         );
     }
 
+    /// A fresh arbiter that never saw `press_start` -- the state a widget's
+    /// own arbiter is left in when a gesture's `ACTION_DOWN` landed on a
+    /// pixel no sensor covered (a row's padding/gap, or its header) and
+    /// only a later `ACTION_MOVE` reached this widget. `update` must not
+    /// silently swallow the whole rest of the gesture here; `is_idle` is
+    /// what a caller checks to notice and recover (RUST.md's I5
+    /// intermittent-touch-scroll-dropout finding, 2026-09-05) --
+    /// `transcript_ui::selection::Selection::drag` is the real caller,
+    /// this is the pure-state half of the fix.
+    #[test]
+    fn is_idle_reports_a_press_that_was_never_started() {
+        let a = DragArbiter::new();
+        assert!(a.is_idle());
+    }
+
+    #[test]
+    fn update_on_an_idle_arbiter_stays_undecided_forever_without_recovery() {
+        // Documents the failure this fix works around: calling `update`
+        // (as if the arbiter were mid-gesture) without ever having called
+        // `press_start` leaves it stuck answering `Undecided`, even for a
+        // movement well past `DRAG_SLOP` that would otherwise pan
+        // immediately.
+        let mut a = DragArbiter::new();
+        assert_eq!(
+            a.update(Vec2::new(0.0, 100.0), t(10)),
+            DragOutcome::Undecided
+        );
+        assert!(a.is_idle());
+    }
+
+    #[test]
+    fn a_caller_can_recover_a_missed_press_start_via_is_idle() {
+        let mut a = DragArbiter::new();
+        // Simulates the real call site: a `Pressing` frame arrives with no
+        // matching `PressStart` ever having reached this arbiter.
+        assert!(a.is_idle());
+        a.press_start(Vec2::new(0.0, 700.0), t(0), false);
+        assert_eq!(
+            a.update(Vec2::new(0.0, 720.0), t(10)),
+            DragOutcome::Pan(12.0)
+        );
+        assert!(!a.is_idle());
+    }
+
     #[test]
     fn release_resets_to_idle() {
         let mut a = DragArbiter::new();

iris/src/task.rs

@@ -72,6 +72,18 @@ impl<Rsc: HasState> Tasks<Rsc> {
         )
     }
 
+    /// The same redraw handle `spawn`'s wrapper calls once, after a whole
+    /// task's future completes -- exposed so a caller running its own
+    /// longer-lived loop *inside* a spawned task (a live SSE follow, here)
+    /// can ask for a frame after each `TaskCtx::update`, not just at the
+    /// end. Without this a caller has no way to get a redraw mid-stream,
+    /// which is exactly the gap `iris/desktop-app`'s `app.rs` module doc
+    /// names for why it uses winit's `Proxy` instead of `Tasks` -- Android
+    /// has no `Proxy`, so this is what closes the same gap there.
+    pub fn redraw_handle(&self) -> Arc<dyn RequestRedraw> {
+        self.redraw.clone()
+    }
+
     pub fn spawn<F: AsyncFnOnce(TaskCtx<Rsc>) + 'static + std::marker::Send>(&mut self, task: F)
     where
         F::CallOnceFuture: Send,