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. 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.
• .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.
• 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. It is clean now apart from Compose 1.11.1 having a 1.12.0 available; 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.
• 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).
• Name the device on every adb call. This checkout runs its own emulator — run-android.sh derives the AVD name from the directory, so a second clone gets a second AVD rather than queueing for one shared machine-wide tdep. With more than one attached, a bare adb shell or adb get-state fails with more than one device/emulator and 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. Get the serial the way run-android.sh does — match adb -s <serial> emu avd name against the AVD — or export ANDROID_SERIAL, which every adb call honours without -s.

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 actually end one, delete the session — that is the only path that stops a process.
• 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.
• 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.
• 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.