Merge remote-tracking branch 'origin/rustify' into worktree-agent-a27094a7db775552a

# Conflicts:
#	docs/IRIS.md

docs/DECISIONS.md

@@ -7,6 +7,48 @@ 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
@@ -18,6 +60,25 @@ marked **DEFERRED** are ones the agent chose not to decide alone.
   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

docs/IRIS.md

@@ -8,6 +8,54 @@ 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: `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

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 +105,18 @@ 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).
+
 ## Build
 
 - [x] **Benchmarks**, not unit tests, run on demand (2026-09-05; a

docs/RUST.md

@@ -59,6 +59,21 @@ session spending an afternoon on them again.
   end-to-end this pass. The fix itself is verified by direct, targeted
   logcat traces taken before that interference began, not by the
   aggregate script.
+- **iris no longer requests compute-shader limits it never uses,
+  2026-09-05.** `adapter.request_device`'s `Limits::default()` asks for
+  desktop-tier compute limits unconditionally even though nothing in
+  `iris`/`iris-core` uses a `ComputePipeline` -- confirmed by grep, not
+  assumed -- which is what crashed `request_device` outright under
+  `EMU_GPU=software`'s `force-gles` path (SwiftShader's GL reports OpenGL
+  ES 3.0, no compute at all). New shared `iris_core::device_limits()`
+  zeros exactly the six compute fields; `rigs/gpu-probe`'s own mirrored
+  limits were updated and confirm `IRIS DEVICE: ok` on this VM's own
+  Vulkan and GL adapters. **The specific SwiftShader-ES-3.0 crash this
+  fixes was not re-verified on-device this pass** -- the cold boot needed
+  would have force-restarted this checkout's emulator while another
+  session had its own app focused on it, so it was left rather than
+  disrupted. See this box's "Fixed, 2026-09-05, later the same day"
+  subsection (under the software-mode crash it fixes) and `DECISIONS.md`.
 - **Decided 2026-09-05: iris over Masonry**, by Iris, from the host-GPU
   numbers in I5's box and E1/E2's findings. See the Recommendation's item
   3 and `DECISIONS.md`. Next: the remaining screens and the app on iris —
@@ -3211,6 +3226,45 @@ silently on real hardware.
       general) explains the ~80-150ms software-mode numbers, since no GLES
       number under software mode could be taken at all.
 
+      **Fixed, 2026-09-05, later the same day.** Not "requesting compute
+      limits only when the adapter reports them" (a capability check with
+      a fallback) -- simpler than that, because iris has no code path that
+      needs compute at all: grepped the whole `iris`/`iris-core` tree for
+      `ComputePipeline`/`@compute` and found none, so the right fix is to
+      stop asking for compute limits, full stop, rather than to build a
+      fallback for a capability nothing uses. `iris_core::device_limits()`
+      (`iris/core/src/render/mod.rs`) is the one place both platform
+      backends now build their `required_limits` from: `Limits::default()`
+      with the six `max_compute_*` fields zeroed and `max_buffer_size`
+      still raised, as before. `Limits::downlevel_webgl2_defaults()` was
+      the first thing tried and rejected -- it also zeros
+      `max_storage_buffers_per_shader_stage`, and `shader.wgsl`'s vertex
+      stage reads four `var<storage>` buffers, so it would have traded
+      this crash for a bind-group-layout one on the same hardware.
+      `rigs/gpu-probe`'s own `Limits` (necessarily a hand-mirrored copy --
+      that rig is deliberately its own crate, not a workspace member) was
+      updated to match and re-run: `IRIS DEVICE: ok` against this VM's own
+      Vulkan (Venus) and GL (virgl, reports OpenGL ES 3.2) adapters.
+      **Not verified against the actual SwiftShader-ES-3.0 failure this
+      pass**: the `EMU_GPU=software` cold boot needed to reproduce it would
+      have force-restarted this checkout's shared emulator while another
+      session had `com.example.aiapp` focused and running on it (`adb
+      shell dumpsys window`), so this pass left that measurement rather
+      than disrupting concurrent work -- matching AGENTS.md's "coordinate
+      with peer agents" guidance rather than contending for the emulator.
+      Everything else: `cargo fmt --all`/`clippy --workspace --all-targets`/
+      `test --workspace` clean, `cargo ndk build`/`clippy` for
+      `iris-android-app --features transcript-screen,force-gles` clean
+      (only the pre-existing unused-`tabs-ui`-dependency warning, unrelated
+      to this change). This also means the software-mode question two
+      boxes up is still open, for the same original reason plus this new
+      one: a GLES number under `EMU_GPU=software` still has not been
+      taken, now blocked on emulator availability rather than on the
+      crash. A future pass should cold-boot `EMU_GPU=software` once the
+      emulator is free, confirm `dev.iris.android.demo` no longer aborts
+      on `request_device`, and take the `iris-scroll.sh` FrameReport row
+      that pairs with this box's host-GPU one.
+
       **Verification, this update.** `cargo fmt --all` (no diff),
       `cargo clippy --workspace --all-targets` (no warnings from the new
       code; pre-existing `wgpu`/`winit`/`naga` future-incompat notices
@@ -3487,6 +3541,180 @@ device.
       this session was told not to touch `iris/`), and anything past the
       emulator — the actual on-phone runs and Iris's pass/fail call.
 
+      **iris half: done, 2026-09-05.** A `bench` Cargo feature on
+      `iris-android-app`, built on top of `transcript-screen`
+      (`bench = ["transcript-screen", "dep:libc", "dep:tokio"]`,
+      `iris/android-app/Cargo.toml`), gives `lib.rs`'s `ActiveClient`
+      priority a third `AndroidAppState` (`bench_client::BenchClient`)
+      over `TranscriptClient` when both features are listed together --
+      matching the exact build command below, which lists both.
+
+      **Fixture.** `include_str!("../../../app/bench-fixture/assets/
+      transcript.jsonl")` (1,915,760 bytes) at compile time -- no asset
+      pipeline needed the way the Compose half's Gradle source set does.
+      `bench_client::parse_fixture` splits the same way `BenchFixture.kt`
+      does: the first 3,200 non-blank lines parsed as `serde_json::Value`s
+      and folded once through `client_core::transcript_fold::fold_page`
+      (the real fold a `/transcript` page goes through), the rest parsed
+      as `event_model::SeqEvent`s and held back as the streaming tail.
+      `build.rs` (transcript-screen's own) now exits early under `bench`
+      before requiring a live server's host/port/token/CA -- `BenchClient`
+      never calls `build_transport()`, so that requirement made no sense
+      for a build that talks to nothing.
+
+      **"Run benchmark" (`.label("Run benchmark")`) and "Copy report"
+      (`.label("Copy report")`)** sit in a fixed bar above the transcript;
+      a selectable `TextEdit` (`.attr::<Selectable>(())`, the same
+      attribute the composer field uses) below it shows the report text.
+      Pressing "Run benchmark" resets `FrameReport`, then drives
+      `List::scroll` in ~60Hz steps (`ANIM_STEP_MS = 16`) to animate each
+      900px/200ms swipe rather than jumping it -- iris's `List` has no
+      built-in tween the way `animateScrollBy(tween(...))` gives Compose,
+      so this is the one place the two backends' bench code has to differ
+      in shape rather than only in numbers -- through the same
+      `rsc.tasks.redraw_handle()` + manual `request_redraw()` per step
+      `transcript_client.rs` already established (a `Tasks::spawn`d
+      future's *automatic* redraw fires once, after the whole future
+      completes, which would show nothing moving until the run ends).
+      After the scroll loop, `List::jump_to_end()` pins to the newest
+      content (matching `stream-bench.sh`'s "Jump to latest" tap), then
+      400 fixture events replay at 20/s through `fold_event` -- the same
+      fold path a live SSE frame takes in `transcript_client.rs`'s own
+      `apply_event` -- each one triggering `rebuild_transcript`'s full
+      `transcript_ui::build_tree` rebuild, same tradeoff as
+      `TranscriptClient`/`desktop-app`. A battery sampler runs
+      concurrently on its own `tokio::spawn`d task (not through
+      `ctx.update`, since a JNI battery read needs no widget-tree access),
+      attaching whichever thread it runs on via a stored `JavaVM` --
+      `AndroidAppState::platform_ready` (new, `IRIS.md`) is what hands
+      `bench_client.rs` that `JavaVM` + a `GlobalRef` to the view, since
+      neither was reachable from `AndroidAppState::new` before this box.
+
+      **Report fields.** `FrameStats`'s existing `Display` (frames, janky
+      %, p50/p90/p99, worst, and I5's own `cpu_p50`/`gpu_wait_p50` CPU/GPU
+      split) plus a `bench:`-shaped tail this box added: process CPU time
+      via `libc::getrusage(RUSAGE_SELF)` (user+system time; chosen over
+      parsing `/proc/self/stat` by hand to avoid assuming `USER_HZ`), peak
+      RSS from `/proc/self/status`'s `VmHWM` (same source `BenchRun.kt`
+      reads), and battery current sampled once a second via
+      `BatteryManager.getIntProperty(BATTERY_PROPERTY_CURRENT_NOW)`
+      through direct JNI calls (`bench_jni.rs`'s `PlatformHandle` --
+      `android_view::context`'s own `Context`/`Resources` wrappers have no
+      `getSystemService`, so this calls it directly rather than growing
+      that crate's wrapper for two one-off calls). `0`/`Integer.MIN_VALUE`
+      read as "unavailable" rather than folded into the average, matching
+      `BatterySampler`'s own rule and UI_RULES.md's "never present an
+      inferred value as a measured one." The report is logged under the
+      existing `iris-android-app` logcat tag on a line starting `iris
+      bench report:` (grep-able the same way `transcript_client.rs`'s
+      "Frame report" control already is), shown in the on-screen
+      `TextEdit`, and copied to the system clipboard by "Copy report"
+      through `ClipboardManager.setPrimaryClip` (`bench_jni.rs`, same
+      `PlatformHandle`).
+
+      **Build commands, all clean this pass:**
+      - `cargo fmt --all -- --check` (iris workspace) and
+        `cd iris/android-app && cargo fmt --all -- --check`: clean.
+      - `cargo clippy --workspace --all-targets` (iris workspace): clean
+        (only the pre-existing `wgpu`/`winit`/`naga` future-incompat
+        notice).
+      - `cargo test --workspace` (iris workspace): 39 + 8 + 10 = the same
+        pre-existing counts, all passing, unaffected by this box (it
+        touched no logic under test there beyond `AndroidAppState`'s new
+        default no-op method).
+      - `cargo ndk -t x86_64 -P 26 clippy --features "transcript-screen
+        force-gles bench" --lib -- -D warnings` (`iris/android-app`):
+        clean.
+      - `cargo ndk -t arm64-v8a -P 26 -o app/src/main/jniLibs/ build
+        --release --features "transcript-screen force-gles bench"`:
+        clean, `arm64-v8a/libmain.so` produced. The pre-existing "unused
+        dependency `tabs-ui`" Cargo advisory also appears on a plain
+        `--features transcript-screen` build with no `bench` (confirmed
+        by building that combination alone with fake env vars) -- not
+        something this box introduced, and not a clippy/rustc warning
+        (AGENTS.md's "keep the build clean" gate is `cargo clippy`, which
+        stays silent on it).
+
+      **Packaging.** No `cargo xtask apk` exists for `iris/android-app`
+      yet (I2's own Gradle project is the only pipeline), so this reused
+      that split rather than inventing one: `cargo ndk --release` above
+      builds the cdylib straight into `app/src/main/jniLibs/`, then a new
+      `release` build type in `app/build.gradle` (there was previously
+      only `debug`) packages and signs it --
+      `AI_APP_KEYSTORE=~/.config/ai-app/release.jks` +
+      `AI_APP_KEYSTORE_PASSWORD` (the same key `app/build-apk.sh`
+      generates for the Compose app) via `gradle :app:assembleRelease`,
+      with `applicationIdSuffix ".bench"` so it installs beside the plain
+      tabs demo rather than replacing it. `aapt2 dump badging` on the
+      result: `package: name='dev.iris.android.demo.bench'`, one native
+      library, `lib/arm64-v8a/libmain.so`. `apksigner verify
+      --print-certs` shows the same `CN=ai-app` certificate
+      `compose-bench-arm64.apk` is signed with.
+
+      **Emulator smoke run, 2026-09-05.** This checkout's own AVD
+      (`ai-app-2`) was in use by the session recording I5's clean-scroll
+      comparison in this same file (its Compose app was in the
+      foreground, confirmed via `dumpsys window`/`dumpsys activity
+      processes` before touching anything) -- rather than contend for it
+      (AGENTS.md's "coordinate with peer agents"), a second,
+      differently-named AVD was created (`AVD_NAME=ai-app-2-bench emu
+      up`, `pixel_10`/`android-36`/`google_apis`/`x86_64`, cold boot, host
+      GPU, no `EMU_GPU=software`), with 12GB of the VM's memory still
+      available after both were up (this-machine-android's "two are
+      comfortable" guidance). Installed via `adb -s emulator-5556 install
+      -r`, launched, driven by `ui-trace record -s emulator-5556 --do
+      "tap 'Run benchmark'"` (the control resolved by its accessibility
+      label, per AGENTS.md's "no coordinate" rule), then read back over
+      `adb logcat`:
+
+          iris bench report
+          frames=372 janky%=56.99 p50=19.5ms p90=219.5ms p99=284.5ms worst=369.3ms (measures redraw-start to after present() is called, not GPU/compositor completion) cpu_p50=0.4ms gpu_wait_p50=13.9ms (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: 24665ms
+            peak RSS: 224600kB
+            battery current: mean 900000µA over 21 samples (min 900000, max 900000)
+
+      "Copy report" was pressed immediately after and logged `iris bench
+      report: copied to clipboard` (`ClipboardManager.setPrimaryClip`
+      succeeded). No crash (`adb logcat`'s `FATAL`/`AndroidRuntime` lines
+      checked -- only `ui-trace`'s own runtime, unrelated), process alive
+      throughout (`dumpsys activity processes`), 400/400 stream events
+      confirmed sent.
+
+      Read this the same way the Compose half's own box already asks to
+      read its number: this is software-rasterised (well, GLES-over-virgl
+      under `force-gles`, per I5's "Where iris's frame time goes")
+      emulator output, "the harness runs end to end and produces every
+      field P0 asked for," not a phone number -- and the battery current
+      is again the emulator's fixed 900000µA mocked charger reporting a
+      constant, exactly what the Compose box's own run found, not a real
+      battery answering. `cpu_p50=0.4ms` (iris's own per-frame CPU work)
+      against a much larger `gpu_wait_p50`/`p50` again matches I5's "Where
+      iris's frame time goes" finding under real GPU rendering (`-gpu
+      host`, `force-gles`) -- the frame-time budget here is dominated by
+      the driver/compositor wait, not by iris's layout or primitive
+      building, though this run's `janky%`/`p90`/`p99` are considerably
+      worse than that earlier isolated pass, most likely the cost of this
+      AVD's very first cold boot plus running two emulators on this VM at
+      once (a fair comparison against Compose would need both apps run
+      back-to-back on the same freshly-booted device, not attempted this
+      pass since the second AVD was torn down immediately after per
+      AGENTS.md's "stop yours when you are done with it").
+
+      Copied to `~/host/bench/iris-bench-arm64.apk` (15,445,468 bytes) and
+      `~/host/bench/README.md`'s "iris" section filled in (install, open,
+      tap "Run benchmark", read the report from the on-screen text or
+      logcat, tap "Copy report", paste back).
+
+      **Not done this pass**: the actual on-phone runs and Iris's
+      pass/fail call between the two reports (P0's own pass condition) --
+      that needs Iris's phone, which this session has no access to.
+      `iris/src/android/view.rs` was touched (`AndroidAppState::
+      platform_ready`, `new_peer`'s wiring) -- confirmed to not be one of
+      the three files the concurrent `device_limits()` work on this
+      branch was using (`iris/core/src/render/mod.rs`,
+      `iris/src/android/render.rs`, `iris/src/default/render.rs`).
+
 - [ ] **P1 — session screen parity.** History paging backward (with the
       page-boundary healing `client-core` does not have yet, below),
       `TranscriptSource`-backed cache/server stitching, jump-to-latest,

iris/android-app/Cargo.lock

@@ -1768,9 +1768,11 @@ dependencies = [
  "client-core",
  "event-model",
  "iris",
+ "libc",
  "log",
  "serde_json",
  "tabs-ui",
+ "tokio",
  "transcript-ui",
 ]
 

iris/android-app/Cargo.toml

@@ -32,6 +32,23 @@ 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"]
@@ -41,6 +58,14 @@ transcript-screen = ["dep:transcript-ui", "dep:client-core", "dep:event-model",
 # 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/build.rs

@@ -22,6 +22,14 @@ 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");

iris/android-app/src/bench_client.rs

@@ -0,0 +1,418 @@
+//! 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, a full
+//! `transcript_ui::build_tree` rebuild per 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; 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.
+
+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::Arc;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::time::Duration;
+
+/// 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;
+
+/// `BenchRun.kt`'s own constants -- kept identical so the two apps' bench
+/// runs are the same gesture and the same load, which is the entire point
+/// of a shared fixture and a shared scripted loop (P0's pass condition).
+const CYCLES: usize = 6;
+const SWIPE_PX: f32 = 900.0;
+const SWIPE_MS: u64 = 200;
+const SWIPE_PAUSE_MS: u64 = 500;
+const STREAM_EVENTS_PER_SEC: u64 = 20;
+const STREAM_SECONDS: u64 = 20;
+/// One animation step's target cadence -- close enough to 60Hz that a
+/// `List::scroll` swipe is many small moves rather than one jump, so
+/// frames are actually rendered along the way (the point of animating it
+/// at all rather than calling `scroll` once per swipe).
+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>,
+    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,
+}
+
+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 controls = bench_controls(rsc);
+        let tree = (
+            controls,
+            content.height(rest(2)),
+            report_display.height(rest(1)).pad(8),
+        )
+            .span(Dir::DOWN)
+            .add_strong(rsc)
+            .any();
+        ui_state.set_root(tree);
+
+        let mut client = Self {
+            ui_state,
+            content,
+            report_display,
+            screen: None,
+            items: Vec::new(),
+            stream_tail: Vec::new(),
+            platform: None,
+            last_report: None,
+            running: false,
+        };
+
+        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
+    }
+}
+
+type Rsc = AndroidRsc<BenchClient>;
+
+fn bench_controls(rsc: &mut Rsc) -> WeakWidget {
+    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(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(8)
+        .add(rsc);
+
+    (run, copy).span(Dir::RIGHT).height(56).add(rsc)
+}
+
+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);
+    }
+
+    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");
+        }
+    }
+
+    /// P0's scripted run: `BenchRun.kt`'s scroll loop, then its streaming
+    /// phase, then the report -- run in-process for the same reason that
+    /// file'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 cpu_start = process_cpu_ms();
+
+        rsc.spawn_task(async move |mut ctx| {
+            // The swipe loop: two drags toward newer content, two back --
+            // a cycle returns to where it started, so the whole loop
+            // measures steady-state scrolling. `BenchRun.kt`'s own
+            // comment on this shape.
+            for _ in 0..CYCLES {
+                for delta in [SWIPE_PX, SWIPE_PX, -SWIPE_PX, -SWIPE_PX] {
+                    animate_scroll(&mut ctx, &redraw, delta, SWIPE_MS).await;
+                    tokio::time::sleep(Duration::from_millis(SWIPE_PAUSE_MS)).await;
+                }
+            }
+
+            // Pinned to the newest end before streaming starts, matching
+            // `stream-bench.sh`'s "Jump to latest" tap.
+            ctx.update(|state: &mut BenchClient, rsc| {
+                if let Some(screen) = &state.screen {
+                    (screen.list)(rsc).jump_to_end();
+                }
+            });
+            redraw.request_redraw();
+
+            // The battery sampler runs concurrently with the streaming
+            // phase, 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(std::sync::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 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| {
+                    state.items = fold_event(&state.items, &event);
+                    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 report is
+            // read -- `BenchRun.kt`'s own closing delay.
+            tokio::time::sleep(Duration::from_millis(300)).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(),
+            };
+
+            ctx.update(move |state: &mut BenchClient, rsc| {
+                state.running = false;
+                let scroll_line = format!(
+                    "  scroll: {CYCLES} cycles ({} swipes), streamed {sent}/{total} fixture events",
+                    CYCLES * 4
+                );
+                let frames_line = match state.android_state().frame_report.report() {
+                    Some(stats) => format!("{stats}"),
+                    None => "no frames recorded".to_string(),
+                };
+                let report = format!(
+                    "iris bench report\n{frames_line}\n{scroll_line}\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();
+        });
+    }
+}
+
+/// Moves `List::scroll` by `total_px` over `duration_ms`, in ~60Hz steps,
+/// so the swipe is many rendered frames rather than one jump -- the same
+/// shape `animateScrollBy(SWIPE_PX, tween(SWIPE_MS))` gives on the Compose
+/// side, in the one place the two backends have to differ (iris's `List`
+/// has no built-in tween, so this drives it by hand).
+async fn animate_scroll(
+    ctx: &mut iris::task::TaskCtx<Rsc>,
+    redraw: &Arc<dyn iris::task::RequestRedraw>,
+    total_px: f32,
+    duration_ms: u64,
+) {
+    let steps = (duration_ms / ANIM_STEP_MS).max(1);
+    let step_px = total_px / steps as f32;
+    for _ in 0..steps {
+        ctx.update(move |state: &mut BenchClient, rsc| {
+            if let Some(screen) = &state.screen {
+                (screen.list)(rsc).scroll(step_px);
+            }
+        });
+        redraw.request_redraw();
+        tokio::time::sleep(Duration::from_millis(ANIM_STEP_MS)).await;
+    }
+}

iris/android-app/src/bench_jni.rs

@@ -0,0 +1,134 @@
+//! 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, and `ClipboardManager.setPrimaryClip` for
+//! the "Copy report" control (P0's iris half, docs/RUST.md). Neither is
+//! 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 two one-off
+//! 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(())
+    }
+}

iris/android-app/src/lib.rs

@@ -23,6 +23,18 @@
 //! 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,
@@ -39,7 +51,11 @@ use iris::prelude::*;
 use log::LevelFilter;
 use std::ffi::c_void;
 
-#[cfg(feature = "transcript-screen")]
+#[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 --
@@ -85,8 +101,10 @@ impl AndroidAppState for Client {
 
 #[cfg(not(feature = "transcript-screen"))]
 type ActiveClient = Client;
-#[cfg(feature = "transcript-screen")]
+#[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>,

iris/core/src/render/mod.rs

@@ -23,6 +23,48 @@ 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()
+    }
+}
+
 pub struct UiRenderNode {
     uniform_group: BindGroup,
     primitive_layout: BindGroupLayout,

iris/src/android/render.rs

@@ -86,12 +86,11 @@ impl AndroidRenderer {
 
         // 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 {
+                required_limits: iris_core::device_limits(),
-                    max_buffer_size: 1 << 30,
-                    ..Default::default()
-                },
                 ..Default::default()
             })
             .block_on()

iris/src/android/view.rs

@@ -4,7 +4,7 @@ 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, sys::jint},
     ndk::event::{Keycode, MotionAction},
 };
 // `marker::Sized` explicitly: `crate::prelude::*` below also brings in the
@@ -107,6 +107,19 @@ 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) {}
 }
 
 /// The android-view analogue of `default::DefaultRsc` -- identical in
@@ -561,7 +574,10 @@ pub fn new_peer<'local, State: AndroidAppState>(
     };
     let shared = Rc::new(RefCell::new(Shared::default()));
     let ui_state = AndroidUiState::new(shared.clone());
-    let state = State::new(ui_state, &mut rsc);
+    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 peer = IrisViewPeer {
         rsc,
         render: UiRenderState::new(),

iris/src/default/render.rs

@@ -102,13 +102,12 @@ 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 {
+                required_limits: iris_core::device_limits(),
-                    max_buffer_size: 1 << 30,
-                    ..Default::default()
-                },
                 ..Default::default()
             })
             .block_on()

rigs/gpu-probe/src/main.rs

@@ -35,6 +35,34 @@ fn iris_features() -> Features {
 /// kept for the big storage buffers behind rects/glyphs.
 const IRIS_MAX_BUFFER_SIZE: u64 = 1 << 30;
 
+/// Mirrors `iris_core::device_limits()` (`iris/core/src/render/mod.rs`) --
+/// cannot call it directly, since this rig is deliberately its own crate,
+/// not a workspace member (this file's own Cargo.toml comment). Keep the
+/// two in sync by hand when one changes; this rig's whole purpose is "does
+/// the device iris actually builds come back," so a stale copy here would
+/// silently stop answering that question. Zeroed rather than left at
+/// `Limits::default()`'s desktop-tier values because nothing in iris
+/// creates a `ComputePipeline` or a `@compute` shader stage -- found by
+/// grepping the whole `iris`/`iris-core` tree before this rig's comment was
+/// written -- and the unconditional default request 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 at all, so the adapter's
+/// real limit is 0). The same would happen on a real GLES-3.0-only Android
+/// device.
+fn iris_limits() -> Limits {
+    Limits {
+        max_buffer_size: IRIS_MAX_BUFFER_SIZE,
+        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()
+    }
+}
+
 fn main() {
     vk::report();
 
@@ -104,10 +132,7 @@ fn main() {
     // limits requested, this is expected to succeed everywhere -- this rig
     // is what turned that from an assumption into a measurement, first on
     // this emulator's software Vulkan.
-    let wanted = Limits {
+    let wanted = iris_limits();
-        max_buffer_size: IRIS_MAX_BUFFER_SIZE,
-        ..Default::default()
-    };
     match pollster::block_on(adapter.request_device(&DeviceDescriptor {
         required_features: iris_features(),
         required_limits: wanted,