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

---
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.