ai-app/AGENTS.md

ai-app

A phone interface to AI coding sessions (Claude Code and llama.cpp via pi), 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. Read it before building or changing anything structural. It records every decision with its date, its rationale, and the alternatives that were rejected and why — keep that habit when a decision changes: update the plan in place, don't let this file and the plan drift into two versions of the truth. This file is the working notes layer: conventions, commands, and things that have bitten.

The central design point, worth not undoing by accident: a session is a child process speaking JSONL over stdio, translated into one common event model. Claude Code (stream-json) and pi (RPC mode) are two translators behind one Driver trait; the transcript, the SSE stream, the phone UI, and SSH spawning (the same command wrapped in ssh host …) all work purely in the common model. A new session type is a new driver — never a session-type branch in shared code (routes, transcript, app screens).

Layout

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 (every session mutation funnels through the manager so in-memory and on-disk state can't come apart). Read dev-updater's README.md and AGENTS.md for the conventions before diverging from them; module-by-module intent for this repo is in PLAN.md's "Backend layout" section.

• server/src/session/import.rs — continuing a Claude Code session the machine already has. Claude Code keeps each one as JSONL under ~/.claude/projects/, and the CLI resumes one with --resume <id> — which claude.rs already does for crash recovery, so an import is that same path with the token written up front rather than a second way to start a session. The phone picks an id, never a path: the server resolves which file that is, so an enrolled token cannot become "read me an arbitrary file" — the same rule that keeps a command out of POST /setups. Only the tail is replayed (REPLAY_LINES) because these files reach tens of megabytes and the CLI reads the real one itself; what crosses the tunnel is what a person reads, not what the model is given. Images in the replayed tail are written into the session's files/ by the same function the live translator uses, so a screenshot looks the same whether it was watched happening or replayed afterwards, and the phone fetches the bytes only when it draws one. An imported session then keeps itself level with that file, so work done at a terminal appears without anyone pressing anything. Which new lines came from here is answered by counting the events this session has recorded, not by looking at its status — a turn that starts and finishes between two polls reads as idle at both, and its own output gets replayed on top of itself. That bug was visible on screen as donedone.
• server/src/usage.rs — rate-limit windows, asked of each machine that can run Claude, not of the backend. Credentials are read through the session Transport, so a remote setup is an ssh round trip and the local one is unchanged; the HTTP call stays here. A machine with no Claude provider is never asked. The four states (ok, notLoggedIn, unreachable, failed) exist because a machine nobody logged in on is a choice rather than a fault, and one error string made it look like one.
• server/src/models.rs — downloaded GGUF models and the HuggingFace browsing behind them. Downloads are keyed by the model rather than by who asked, so any device can watch one; they resume through HTTP Range, refuse to resume onto a partial from a different revision, and are checked against HuggingFace's published sha256 before the file gets its real name.
• server/ — Rust backend (ai-server). main.rs bootstraps (TLS, the auth layer, token/QR enrollment, wg0 binding), routes.rs has the HTTP table in its module doc comment, auth.rs the bearer-token middleware, config.rs the persisted schema (written in the shared RON house rules), session/ the manager (registry pattern), Driver trait + event model, EchoDriver, and transcripts.
• app/ — Compose Android app, single :androidApp module, package com.example.aiapp, label "AI Sessions". AppRoot.kt is the navigation when; MainScreen.kt the root's four tabs (sessions, import, models, setups) with settings and refresh on the title row; Api.kt/EventStream.kt the REST + SSE clients; Events.kt the event model mirror; ServerConfig.kt settings + Keystore-sealed token; screens in SessionListScreen/SessionScreen/SpawnScreen/SettingsScreen. Notifications.kt is the foreground service holding the notification stream and the one place that decides where a notification is said -- nothing for the session on screen, a SessionAlerts banner while the app is up, Android's drawer otherwise, never two of them. See PLAN.md's "Notifications: two places, never both". Icons are Nerd Fonts glyphs from a committed subset, not vector assets and not ordinary Unicode — NerdIcons.kt declares each codepoint and app/build-icon-font.sh subsets the font. The two lists have to agree: a codepoint in the Kotlin that the script did not subset is a glyph that silently isn't there. Rerun the script and commit its output when adding one; it needs network access. md-cog and md-refresh are deliberately the same codepoints dev-updater uses and must not drift from it. The subset is the Mono face, where every glyph is one em square — that is what makes two icon buttons the same width without either being given one, and it is why GLYPH_SIZE is smaller than it looks like it should be.
• .dev-updater.ron — what Dev Updater is asked to do with this checkout: the server (built in server/, run as service: Managed(...)) and the APK (built in app/), built in parallel. The project it serves is the repository, not either half of it, which is why this sits at the root rather than in app/. It points at resources.ron beside it, which says this project keeps its state as ai-app — so the Uninstall dialog offers ~/.local/share/ai-app and ~/.config/ai-app instead of saying it cannot tell. That file is ours, not Dev Updater's: it ignores keys it doesn't know, so anything else worth keeping in one place belongs there too. Note what deleting the config directory takes with it — the CA under certs, which is the one-way door described below. Managed means Dev Updater supervises ai-server with its own built-in service implementation rather than a script kept here. ai-app had such a script until 2026-08-28 and it was the generic case exactly — no arguments, no environment — so the two projects were maintaining one behaviour twice, including the OpenRC branch neither can test from a systemd machine. Worth knowing before pressing it: Stop on the server card stops the server that a phone reaches through the tunnel, so on that phone it stays down until someone starts it again from Dev Updater. Dev Updater reaches it over its own port and is unaffected, which is what makes the button safe to press and easy to regret.
• wg-app-link/ — a git submodule, and the half of this backend that dev-updater also needed: the pinned CA and leaf (certs), QR enrollment and the bearer token (enroll), wg0 binding and the certificate's SANs (netif), owner-only files (private), and the RON house rules (format). Both projects had written all five and they had drifted; see that repo's README.md for the diff that decided each one. Clone with git clone --recurse-submodules, or git submodule update --init in an existing checkout — server/ will not build without it, since it is a path dependency rather than a registry one, which is what keeps the two projects version-locked to the commit this repo pins. The certificates are the one-way door: the CA is generated once on first start into $XDG_CONFIG_HOME/ai-app/certs and regenerating it strands the installed app. What deliberately did not move is the API surface and the config schema — routes, drivers, sessions and setups are what makes this project itself.

Status

Phases 1–3 done 2026-08-24 (PLAN.md's phase list says what each verified): the skeleton pipe, the full Claude driver (streaming, tools, permission + AskUserQuestion cards, steering, interrupt, --resume crash recovery, images both ways), and the usage screen.

Phase 5 (SSH) is written and exercised (2026-08-28): a session names a host, session::transport turns that into an ssh host … invocation, and the driver never learns which it got.

Phase 4 (llama.cpp) works end to end, phone included (2026-08-28). Models are browsed and downloaded from HuggingFace (models.rs, resumable and verified), and session::llama runs one through llama-server over its OpenAI-compatible streaming endpoint. Two things are deliberate and easy to undo by accident: the conversation is rebuilt from the transcript rather than kept in the driver, because driver memory is invisible to a second device; and a llama session is refused on an ssh host, because the model is reached over HTTP and forwarding that port is not built.

Setups — machines, each carrying what it can run — are added, renamed, re-probed and removed from the app; providers are discovered by asking the machine, never typed, so the enrolled token cannot introduce a command. What is left is real-phone/WireGuard bring-up, which is operational rather than code.

command -v follows PATH under a non-interactive ssh session, which is not the PATH a login shell shows, so a binary somewhere unusual is invisible to discovery — llama.cpp unpacked into ~/.local/opt needs a symlink into ~/.local/bin before a setup finds it. The escape hatch for anything odder is editing config.ron on the backend, deliberately the one authority the phone does not have.

Testing llama.cpp here: the prebuilt CPU build lives outside the repo at ~/.local/opt/llama.cpp (the 15 MB ubuntu-x64 release asset). It needs its own directory on LD_LIBRARY_PATH, so start the server as LD_LIBRARY_PATH=~/.local/opt/llama.cpp ai-server … and point a provider's command at ~/.local/opt/llama.cpp/llama-server. A 0.6B Q8_0 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.

How to test SSH here, since there is no second machine: ssh this VM to itself. Generate a throwaway key, append the public half to ~/.ssh/authorized_keys, and configure a host of bob@127.0.0.1 with identityFile pointing at it plus options: ["StrictHostKeyChecking=no", "UserKnownHostsFile=…"] so it touches nothing real. 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. Take the key back out afterwards. Note the remote login shell here is fish; the remote script (cd '…' && exec '…') 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 isn't either is the thing to suspect first if a remote spawn ever mangles an argument.

Checking your work

• Server: ./run-tests.sh from the repo root (or cargo test from server/) + cargo clippy --all-targets + cargo fmt. The build stays warning-clean and rustfmt-clean at the defaults — there is no rustfmt.toml and there should not be one.
• App: from app/, . ./android-env.sh && ./gradlew :androidApp:ktfmtFormat :androidApp:compileDebugKotlin :androidApp:lintDebug — format, typecheck and lint, the app-side equivalent of the line above. Then ./build-apk.sh to produce the APK to install on a phone (through Dev Updater), or ./run-android.sh to build, install, and launch on the emulator.
• A row something is happening to is dimmed, drained of colour, inert, and says which operation in a word -- BusyItem, used by both the session list and the import list so the appearance is learned once. The word rather than a bare spinner because "deleting" and "importing" differ in kind. It dims and desaturates but does not make the row inert: the caller disables its own click handler while it passes a label. An overlay consuming pointer events was tried and swallowed the drag along with the tap, so a list could not be scrolled while anything in it was busy.
• Importing and deleting run on the server, not in the request, and a batch is handed over in one call. POST /setups/{id}/importable/delete and POST /setups/{id}/importable/import each take a list of session ids, answer 202, and do the work in spawned tasks -- because the phone that asked is free to leave and used to cancel its own batch by doing so. A list rather than a route per session because one request per row made a handover only as atomic as the network: some rows started and the rest were never asked for, and a row nobody asked for looks exactly like a row nobody picked. Every id is registered as in flight before the 202 goes back. Only the registering is atomic; the work itself settles per row, since six deletes that all roll back together is not something a filesystem offers. What replaces the reply is session::pending: every row of the listing carries pending and error, and GET /setups/{id}/importable/events streams the changes. Both, not either. The stream is a broadcast with no memory, so an operation that starts and finishes while it is still connecting is one nothing will ever be said about -- that left a row marked "waiting" for ever, and the listing is what repairs it. So the screen fetches again after a handover when anything still looks outstanding, and takes the row states from the answer rather than from what it remembers.
• A single tap still waits. "Continue this and take me to it" needs the session it made, and 202 does not carry one. The batch and the tap share spawn on the server so the two cannot drift about what importing means.
• The import screen selects in batches: hold to enter, tap to add. The options that act on a selection appear along the bottom, and are Delete and Import only. Submitting clears the selection immediately and marks every chosen row -- the one in flight as "importing" or "deleting", the rest as "waiting" -- so the bar goes away and the affected set is what says the work is happening. Rows are taken out as each one lands rather than all at the end: a finished row still sitting there looks exactly like one that has not been imported, and tapping it starts a second CLI on the same transcript. What that costs is that the rows below slide up under the reader's finger, so a row that has just moved ignores taps for half a second (SETTLE_MS).
• An answered question keeps its options and marks the one that was taken, in the same purple that says "picked" while it is still open -- it does not collapse into a line repeating the answer. The options are what the question was, and "Deny" alone does not say that Allow was the alternative. One rule in two places (AskedQuestion and PermissionAsk), since a permission is a question with two bare options rather than a different kind of thing. An answer typed into Other matches no option, so that one is still written out -- the state the marking cannot say.
• Anything that is a note about the conversation rather than a turn in it is closed by default: a tool call, a peer message, and now a memory note (<cc-memory>). Open-ness is the screen's, never the card's -- a card that remembered for itself forgets the moment the lazy list stops composing it, so a note opened and scrolled past would shut behind the reader.
• The full-screen image lives on the screen, not in the row that drew the thumbnail (SessionImageViewer). A Read whose result is an image is a row of one call until the next call arrives and makes it a group -- a different composable in a different part of the tree, so the old subtree and everything it remembered goes, the open dialog included. Somebody looking at a screenshot was thrown back to the transcript because the session made another tool call. /tools n gap puts an image on its first call so this is reproducible: open it, wait a gap, watch the row regroup.
• All transcript text is selectable, from one SelectionContainer around the whole list (TranscriptList.kt). Not per row: a transcript is one body of text to a reader, so a selection has to be able to run from a reply into the tool output under it -- and a container per row leaves whatever was drawn without one silently unselectable, which nothing on screen reports. Rows keep their tap handlers; selection is a long press.
• A queued message can be tapped to take it back, which is POST /sessions/{id}/unqueue and a messageDropped event -- see PLAN.md's "Taking a queued message back". On a Claude session it always refuses, and that is correct rather than broken: the driver writes a steer into the CLI the moment it arrives, so what the bubble is waiting for is the CLI reading it, not this server sending it. The refusal is drawn on the bubble. The echo driver really does hold its queue, so that is the rig for the case where the drop succeeds.
• 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.
• One Claude Code session id can name two files, and the listing offers it once. Resuming a session 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 (--resume, the delete glob, the in-flight registry) 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.
• A markdown table wraps its cells and never cuts one off. The renderer's own defaults draw every cell at one line with an ellipsis, which on a phone loses most of a table -- and an elided cell looks exactly like a short one, so nothing on screen says anything was cut. Markdown.kt supplies its own header and row blocks with maxLines = Int.MAX_VALUE and TextOverflow.Clip, cells aligned to the top of the row so a two-line cell does not re-centre its neighbours. Width is the other half: a column narrows to 136dp and no further, and past that the whole table scrolls sideways rather than squeezing -- 136 because it is the widest floor that still fits three columns across a phone, which is the commonest table there is. Exercise it with the echo driver's /table N (default six columns), which writes long cells on purpose: a fixture of tidy one-word values renders fine whether or not the truncation is fixed.
• 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 notification on Android 12 and below. It is fully clean as of 2026-08-31; keep it that way, and suppress with tools:ignore plus a written reason rather than by lowering the bar.
• The APK pins the CA of the machine that builds it, read at build time from $XDG_CONFIG_HOME/ai-app/certs/ca.pem (AI_APP_CA overrides) and generated into a constant. So the server must have started once on that machine first — the build stops with that instruction otherwise — and an APK built in this VM only works against a server in this VM.
• Run the server for development with --bind 127.0.0.1. Without it the server binds wg0, which exists here but is unreachable from the emulator (it dials 10.0.2.2). First run prints the enrollment QR/URI with the token — capture it from the log.
• app/debug-transcript.sh puts a real conversation on the emulator. The echo driver stays the right rig for most things and is 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 rather than a word. 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 all down again. 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.
• app/ui-sandbox.sh is the rig for anything that lists or deletes sessions. It starts 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. Neither is a price worth paying to look at a list. It shares the real TLS certificates, because the installed APK pins that CA, so run it while the ordinary server is down. It passes --delay by default for the reason the next entry gives, and AI_SANDBOX_BIG_MB puts one large transcript among the small ones -- 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.
• ai-server --delay MS holds every response back. Over the tunnel a phone's requests take tens to hundreds of milliseconds, and several faults live entirely in what the app does while one is outstanding. On a loopback server those windows close before anything can be observed, so the bug looks like it is not there.
• 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. Sibling to debug-transcript.sh, and the two cover different halves: reach for this when what is under test is whether a process is running, and for the script when it is what the transcript draws. (From the ai-app-2 session, 2026-08-30, which found a clock bug with it that the tests did not have.)
• Prefer exercising the server directly over going through the UI: curl --cacert ~/.config/ai-app/certs/ca.pem -H "Authorization: Bearer …" https://127.0.0.1:8443/sessions. The CA is wherever --certs put it — by default under $XDG_CONFIG_HOME (~/.config when that is unset), never in the checkout, so a relative certs/ca.pem finds nothing. The emulator app reaches it at https://10.0.2.2:8443; enroll it with adb -s "$SERIAL" shell "am start -a android.intent.action.VIEW -d 'aiapp://enroll?host=10.0.2.2&port=8443&token=…'" (quote so the device shell doesn't eat the &s).
• 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 — refusing when the machine has no room for one; emu list says what is attached and what it costs; emu down stops it. run-android.sh is that plus a build and an install. Run that repo's install.sh once if emu is missing. The adb on PATH after sourcing android-env.sh is that repo's wrapper, which fills in -s from the same rule — so a bare adb shell reaches this checkout's emulator and refuses to reach another one's. That defaulting is what makes the old advice unnecessary rather than wrong: with two attached and no -s, a bare adb shell pm list packages comes back empty, which reads as the app having been uninstalled rather than as the question being ambiguous. Gradle does not go through that wrapper, so it had the same hole until 2026-08-31: installDebug, uninstallDebug and connectedAndroidTest ask the adb server for every attached device and act on all of them, which is how one session's debug build landed on another's emulator. A Gradle init script from emulator-tools now runs emu check before those tasks and fails the build rather than fanning out. When it refuses, say which device you mean at the moment you use it — ANDROID_SERIAL=$(emu serial) ./gradlew … — rather than exporting a serial into the shell, which goes stale the next time an emulator restarts and another checkout's takes the port.

Where things run (host vs this VM)

Established 2026-08-25. The machine itself — the two boxes, the shared ~/repos mount, and why the VM is untrusted — is described once in ~/.claude/MACHINE.md; what follows is only what that means here.

• ai-server belongs on the host in production. That is where the LAN address the phone can reach is, and where WireGuard terminates. wg-setup-host.sh sets that up (keys, wg0.conf, the phone's QR); run it there with sudo WG_ENDPOINT=<ddns name>.
• The tunnel and the real phone can never terminate in the VM, because nothing outside can open a connection into it. Phone bring-up is host work.
• wg0 (10.66.0.1) exists in this VM too, so the production path — ai-server with no --bind — is exercisable during development. It has no reachable peer and doesn't need one. Consequence: with no --bind the emulator can't reach the server (it dials 10.0.2.2), so keep using --bind 127.0.0.1 for app work.
• ./test-wg-tunnel.sh up|test|down builds a real tunnel between two network namespaces inside one machine and drives the server through it — a genuine handshake against 10.66.0.1 with pinned TLS, no router or phone involved. That's how to verify the wg0-only posture.
• The claude CLI is only in the VM, so from the host it is a remote. The backend reaches it as it would any other machine: a configured host, and a session that names it.
• Nothing secret goes in the repo, which is shared with the host and attacker-writable under this project's threat model (PLAN.md's security section). State lives outside it: $XDG_CONFIG_HOME/ai-app/config.ron and certs/, $XDG_DATA_HOME/ai-app/sessions/, owner-only.
• Certificates are generated by the server, on first start, into $XDG_CONFIG_HOME/ai-app/certs (--certs overrides). The CA is created once and left alone; the leaf is reissued every start, so covering a new address is a restart. Starting the server in the VM therefore makes a separate throwaway dev CA — never install a build pinning that on the real phone.
• Point development at a scratch state directory rather than the real one: --config /tmp/…/config.ron --data-dir /tmp/…/sessions --port 8444.

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 — so restarting the backend does not end a turn. PLAN.md has the design; what matters day to day:

• Stopping the server no longer stops the sessions. After pkill ai-server the claude processes are still there, on purpose, and the next start picks them up (reattaching to the claude-cli it left running in the log). To end one, either POST /sessions/{id}/stop — which keeps the session and its transcript, and POST .../start brings the process back on the same conversation — or delete the session, which ends the conversation too.
• A message or a command sent to a stopped session starts it. POST .../message, .../command and .../compact go through SessionManager::send_message and ::run_command, which start a process first when the session is known to have exited and then hand the thing to the driver that has one behind it. Only on exited: unknown has a process that may well be reading its fifo. /rename starts one too, and for a sharper reason than the rest: the CLI keeps its own copy of the name, that copy is what its session picker and other agents' session lists show, and a session is only ever given a name at birth — every later start is a --resume — so a rename that reached no process would leave the two lists disagreeing for good. Its save happens before the telling, so a failure there says the telling failed rather than the rename. So the Start button is for when you want a process and nothing to say to it yet.
• A backend start adopts and starts nothing (2026-08-30). It picks up the processes still running and leaves every other session as it found it: listed, with its transcript and its stream, reporting exited, with no process and no driver until somebody asks for one. Restarting the server used to relaunch a driver for every session, which started a CLI for each one that had none — so a session stopped on purpose came back at the next rebuild, and the Idle the new driver announced stamped every row as active just now. If you are looking for a stopped session's process after a restart, there is deliberately none; press Start, or send it anything.
• A launch never moves a session's clock. A status it has to correct is written at the time of the last thing the session actually did, not at now(), and a session that has never done anything reports SessionConfig::created rather than the clock — its transcript is empty, since a driver announcing the state it starts in is not news, so there is no line to read a time off. Both are the same rule as Transcript::last_activity: a restart has been told nothing, so it must not claim anything happened.
• A session spawned while testing cleans itself up: --throwaway-sessions (2026-08-30), which a debug build defaults to on. Every session spawned by such a server is marked throwaway: true in config.ron, and its process is stopped — SIGTERM, then SIGKILL after process::STOP_GRACE — when the server exits or is sent SIGTERM/SIGINT. Sessions outliving the backend is right for the ones somebody is using and wrong for the ones a test made: those leave a claude behind that every later server adopts, and they pile up unnoticed (twelve on this machine in a day, each holding a conversation open). Two things worth knowing. The flag decides only what new sessions are marked as; what happens on the way out is decided by the mark, which is the session's own — so a session you spawned deliberately keeps running whichever server is up when one exits, and a throwaway one is cleaned away even by a server started without the flag. And the waiting is not optional: process::stop leaves its SIGKILL on a tokio timer, which a runtime that is shutting down never runs, so process::wait_gone does the waiting on the way out. Pass --throwaway-sessions=false to keep what a development server spawns.
• A process that has exited but not been reaped reads as dead, not alive. /proc/<pid>/stat keeps the entry — same pid, same start time — until the status is collected, so a zombie used to answer "still there", which made exited unsayable: the session showed unknown, its Start button never appeared, and stopping it said there was nothing to stop. process::stat_of reads the state field alongside the start time.
• Each session directory now holds process.json, stdin.fifo, stdout.log and stderr.log. stdout.log is the driver's input, read from the byte offset in process.json; removing either by hand while the session is live loses output or replays it.
• --resume only ever runs when nothing is running. That check is the fix for the incident below, and the reason there is one entry point (ClaudeDriver::launch) rather than a spawn and an attach. The status a launch reports obeys the same rule: a session recorded as exited whose launch has just started a process reports idle, because exited is the word that refuses every command and offers a phone the chance to start a second CLI on a live conversation.
• exited is never taken on trust; it is checked against the process record (corrected in session/mod.rs). It is the one status that draws the phone's Start button and lets start_session build a driver, so a record that is not known to be dead makes it false and the session reports unknown instead. Without that, a session adopted at a backend start kept the transcript's exited while its CLI was running, Start was accepted every press, and each press left another reader on the same process — which reads on screen as one reply written several times, interleaved (GotGotGot it — it — it —), not as anything to do with a button. A driver that start_session replaces gets Driver::detach for the same reason: swapping the Arc does not end the tasks the old one is running.
• Remote sessions are adopted too. The pid recorded for one is the ssh client's, on this machine — that is the process the backend owns, and it lives as long as the remote command does. (This said "local only" until 2026-08-29; the code never had that branch.) Note the far claude always has an sshd pipe on stdin whichever version started it, since the fifo is on the backend's side — so you cannot tell a backend's version by looking at a remote session's stdin.

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 now — it reads ~/.claude/sessions/<pid>.json, which Claude Code keeps for every live session, and checks the pid's start time so a descriptor left by a crashed CLI doesn't count. Refused rather than warned about, because on 2026-08-29 an agent imported the session it was itself running in. That put two claude --resume processes on one file: the whole 65 MB conversation, 154 embedded screenshots included, was re-appended to the transcript under a new prompt id, both copies replayed each other's writes as work done elsewhere, and the adopted one was billed for re-reading all of it. It ended at the account's session limit, with three claude processes running against one checkout.

Things that have bitten

Project-specific only — a lesson that would bite any project on this machine belongs in ~/.claude/TOOLCHAIN.md (toolchain versions) or ~/.claude/MACHINE.md (the machine itself) instead.

• tracing caches callsite interest process-wide. A test that hits a tracing::warn! with no subscriber installed can poison the interest cache for a concurrent test that captures logs (flaky "nothing was logged" failures). Keep every exercise of a logging code path under the one capturing subscriber — that's why the auth middleware has a single combined gating+logging test.
• The keyboard pans the window unless the activity opts into resize. Without android:windowSoftInputMode="adjustResize", opening the IME slides the whole window up (top bar off screen) instead of resizing — imePadding() alone doesn't fix it and the transcript looks empty.
• A PEM constant must start at the opening quotes. A generated """\n-----BEGIN CERTIFICATE----- costs Android's CertificateFactory its preamble sniff, so it tries DER instead and fails at runtime with ASN.1 ... DECODE_ERROR — nowhere near the code that produced it.
• A reconnecting phone used to be sent the entire backlog. The SSE stream replayed everything after the client's cursor, unbounded, while opening a session was bounded to a page — so a long disconnect delivered thousands of events one frame at a time. Past CATCH_UP_LIMIT the stream now sends a reset frame and the newest window instead, and the client rebuilds from it exactly as it does when the screen opens. The reset is not optional: without it the window is spliced onto rows that are no longer adjacent to it, which reads as ordinary output.
• The five-hour window has no reset time between blocks, and that is not a missing value. The usage API anchors it to the block it started in -- measured 2026-08-31, the reset came back as exactly five hours after work resumed, and the weekly windows in the same response carried the identical microsecond, so both are computed from one now() at request time. When no block is running there is nothing to reset and resets_at is null; the same response shows other idle windows with the same shape. The weekly ones always have a reset because a week is always running, which is why "the others seem fine". So resets_at absent means not running, and only a timestamp that arrives and cannot be parsed is unknown. The app collapsed both into one null and the session bar said "reset time unknown" for a machine behaving perfectly -- while the usage dialog, reading the same field, quietly drew nothing. WindowEnd in ResetCountdown.kt is now the one rule both go through.
• Resolving one importable session used to list every one of them. import::delete and the import seed both called list, which reads every transcript Claude Code has ever written -- measured at 3.7 seconds against the 867 MB in this VM, paid once per session in a batch. import::find takes the same script with one glob narrower, and delete resolves the path itself: 78ms. Ids are checked (is_session_id) before they reach that glob, since a / or .. in one walks it out of the projects directory and delete removes what it lands on.
• A transcript page used to cost the whole transcript. read_window read and parsed every line and then kept the last limit of them, so the work was the size of the conversation rather than the size of the answer: on a 21 MB, 24,000-event transcript one page took ~500ms of server time to return 620 KB, and took the same 500ms whichever page was asked for. A phone scrolling back paid it per page and every stream reconnect paid it again to find out nothing had happened. It is a bisection now (Indexed in transcript.rs) -- sequence numbers only increase, so the edge of a range is found by parsing one line per halving and only the window is built. Same page, ~110ms, of which ~20ms is the file scan. The file is still read whole; that is where the remaining cost is, and going further means a chunked backwards reader. RUST_LOG=ai_server=debug logs each page with what was asked and what came back, which is how to see a phone paging back in real time.
• A page is 800 events and a screen is a handful of rows, and the two have no fixed ratio. A run of thirty-five tool calls is one row; a reply is hundreds of text deltas folded into one. So anything that budgets in rows has to measure a screen rather than name a number: the history cushion was eight rows, which on a tool-heavy transcript is less than one screenful, and the reader hit the end of what was loaded on every swipe and stood there for a round trip. It is HISTORY_SCREENS viewports now, counted from what is actually on screen. Measured at the server, which is the one number here that does not depend on how the emulator renders: against a 24,000-event transcript, ten swipes asked for ten pages before and three after.
• What the transcript screen costs to scroll, for whoever measures it next. Taken 2026-08-30 on the GPU emulator (emu up provides one; a frame number from the software rasteriser means nothing -- see ~/.claude/MACHINE.md), against a real imported transcript with the debug 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 and what is left is the emulator rather than the app. 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.
• Only fetchTranscript was off the main thread; the fold was not. foldEvent returns a new list per event, so a page is that many copies of a growing list -- fine at 80 events and about 300,000 element copies at 800, run in the middle of the scroll that asked for it. warm had the same shape: the markdownIn scan that decides what to parse ran before the hop to Dispatchers.Default, over every assistant message loaded, on every page. Both are off it now. The shape to watch for is a withContext that wraps the fetch and leaves the work done with the result outside it.
• ZXing only looks for a dark code on a light ground. The enrollment QR is block characters in the terminal's foreground colour, so a dark-themed terminal renders it as a negative and the in-app scanner silently never matches — while the phone's own camera app, which tries both, does. The scanner asks for Intents.Scan.MIXED_SCAN, which alternates normal and inverted frames; keep it that way rather than making the server dictate the colours. EnrollmentScanActivity also turns off the library's 10% framing-rect inset (it decodes only what is inside it) and its laser/result-point decorations.