ducoterra
896cca2f23
PLAN.md locks the architectural decisions (WebRTC mesh with the sharer as sole offerer, JSON-only signaling, in-memory roster with no database, no auth, no CDN, Linux as the reference platform) and records the roster rules, the verification ladder, and the constraints that are accepted rather than hidden: the secure-context requirement, mesh upload scaling with watcher count, and the Wayland portal's per-share prompt. Phases are deliberately not written yet -- the prototype and its tests came first, so .agents/phases/todo/ holds only a README pointing at the candidate phase list in PLAN.md section 7. SECURITY.md answers the question a no-auth tool has to answer: not "who is allowed in" but "where is this allowed to run". It separates what an unauthenticated LAN visitor can do from the guarantees that are enforced and named to a test, and tells users the two things they will actually hit -- that http://<lan-ip> hides getDisplayMedia, and that on Wayland the compositor asks every time and mirror must not work around it. LLM-Generated: true
144 lines
7.5 KiB
Markdown
144 lines
7.5 KiB
Markdown
# mirror — Agent Operating Rules
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**Read `.agents/PLAN.md` before touching anything here.** It holds the locked
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architectural decisions; this file holds the rules for working inside them.
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`mirror` is browser-only screen mirroring for a local network: `/mirror` shares a
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window/screen/tab via the OS-native picker, `/watch` shows every live mirror and
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lets anyone take one fullscreen. Media flows peer-to-peer over WebRTC; the server
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is a roster and a signaling relay. Linux is the reference platform.
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---
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## 1. The order of reading
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1. `.agents/PLAN.md` — architecture, locked anchors, verification ladder.
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2. `README.md` — the user-facing contract.
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3. `SECURITY.md` — why there is no authentication, and what that costs.
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4. `src/mirror/registry.py` — the whole policy lives here. Read it before
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changing behavior; it is short and it is the product.
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## 2. Phased execution
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```
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.agents/
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├── PLAN.md ← locked design (do not edit without an explicit decision)
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└── phases/
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├── todo/ ← pending phases: NN_name/00_phase.md + NN_task.md
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└── complete/ ← finished phases, read-only history
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```
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* New work enters through the **`phase-authoring` skill**, never as a direct
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implementation of a vague request.
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* Phases run through the **`phased-execution` skill**.
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* Never edit anything in `phases/complete/`. Ask before editing `phases/todo/`.
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* Never edit `PLAN.md` unless the user explicitly authorises a change to a locked
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decision, and record the reason in the same change.
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* A phase is not done until every gate in §4 passes.
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*(The roadmap is intentionally empty at the prototype stage: a working prototype
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came first, and the candidate phase list is §7 of `PLAN.md`.)*
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## 3. Locked decisions that are easy to break by accident
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| Rule | Why it exists |
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|---|---|
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| **No external assets.** No CDN, remote font, remote icon, `@import`, or analytics | LAN/offline correctness. `tests/test_app.py::TestClientScripts::test_nothing_is_loaded_from_a_cdn` fails the build if you add one |
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| **No framework, no bundler** in `src/mirror/static/` | Two pages and one WebSocket. `node --check` is the entire frontend toolchain |
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| **Media never passes through the server** | The server relays JSON only. Anything that puts frames in the Python process violates A3 |
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| **`Registry` stays pure** — no sockets, no FastAPI, no `await` | It returns `list[Envelope]`. Transport lives in `Hub`. This is why the policy has 100%-ish unit coverage |
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| **camelCase on the wire, snake_case in Python**, via `alias_generator=to_camel` | A silently-dropped `displaySurface` was a real bug we shipped. Any new multi-word field needs an alias test |
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| **No authentication** (A11) | Product brief. If you think it needs auth, that is a `PLAN.md` discussion first — and see `SECURITY.md` |
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| **No STUN/TURN by default** | A LAN tool must not announce internal addresses to a third party |
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| **Teardown is broadcast to every viewer**, not just subscribers | Tiles are drawn on `stream_added`; a non-subscribed viewer still has a stale tile to clear |
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| **Keep both `<video>` elements `muted playsinline`** | Autoplay policy on iOS/Safari otherwise blocks the wall entirely |
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## 4. Gates — run all four before calling anything done
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```bash
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uv run ruff check . && uv run ruff format --check .
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uv run pyright # must be 0 errors
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uv run pytest # unit + API + browser E2E (~20s)
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MIRROR_REALDISPLAY=1 uv run pytest -m realdisplay # Linux-native X11 capture
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```
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Coverage is ~94%; the media path is covered by browser assertions, not by unit
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tests pretending to be WebRTC.
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## 5. Browser testing rules
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Non-negotiable, all learned the hard way (full notes in `PLAN.md` §5):
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* Launch with **`channel="chromium"`**. The headless shell has no media stack —
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`navigator.mediaDevices` does not exist there.
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* Serve pages over **`http://127.0.0.1:<port>`**. On `about:blank` or a plain
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LAN IP, `mediaDevices` is undefined and the test proves nothing.
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* Deterministic capture: `--use-fake-ui-for-media-stream
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--use-fake-device-for-media-stream` → a real, *moving* 1280×720 monitor stream.
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* Real capture (the `realdisplay` suite): private **Xvfb**, headed Chromium,
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`--auto-select-desktop-capture-source="Entire screen"`, `--ozone-platform=x11`,
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and **never** `--use-fake-ui-for-media-stream` (it approves the request without
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selecting a source and the capturer dies with `NotReadableError`).
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* **Strip `WAYLAND_DISPLAY` and `DBUS_SESSION_BUS_ADDRESS`** from any headed
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browser env (`tests/e2e/test_x11_capture.py::browser_env`). Otherwise the
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portal captures the developer's actual desktop and pops a permission dialog on
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their real screen.
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* Assert media on the **viewer's** `<video>` — decoded size and *frames that
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differ*. The sharer's preview proves nothing crossed the wire.
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* Two browser **processes**, not two contexts, when a test means "two machines".
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## 6. JavaScript rules
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* Plain ES modules loaded with `<script type="module">`. No globals beyond
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`window.__probe` in test scaffolding.
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* Every element a script looks up (`$("#id")`) must exist in its page — enforced
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by `test_every_element_the_script_reaches_for_exists`.
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* Element ids must not collide **across** pages (one shared stylesheet):
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`test_the_two_pages_share_no_element_ids_but_the_shared_chrome`. The only
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allowed shared ids are `net`, `notice`, `toast`.
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* WebRTC: the **sharer always offers, the viewer always answers**. Queue ICE
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candidates until `remoteDescription` exists; serialise offers per peer to avoid
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glare. Reuse `net.js` rather than duplicating socket logic.
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* Never move a `<video>` element's `srcObject` to "switch views" — move the
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element (that is how `/watch` staging works) so the peer connection survives.
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## 7. Python rules
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* `from __future__ import annotations`, full type hints, Google-style docstrings
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on public functions.
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* Starlette ≥1.10 raises **`WebSocketDisconnected`** (a `RuntimeError`) when the
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app has already closed a socket, and `WebSocketDisconnect` when the peer does.
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Catch both; read a socket you closed and you will crash the connection handler.
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* Registry errors are `RegistryError(code, message, fatal)`; `fatal` means the
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socket closes after the error frame is delivered. New error codes get a test.
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* No bare `except:`; swallow only what you can name, and say why in a comment.
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## 8. What to do when something behaves mysteriously
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Reproduce at the lowest layer that can fail:
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1. `curl -s localhost:8055/api/streams | python -m json.tool` — server truth.
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2. `websocat ws://localhost:8055/ws` — speak the protocol by hand (see PLAN §3).
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3. `uv run pytest tests/test_registry.py` — is the policy wrong, or the wiring?
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4. Only then reach for a browser, and print `pageerror`/`console` from the first
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line of the test.
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## 9. Commits
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* Conventional Commits (`feat:`, `fix:`, `test:`, `docs:`, `chore:`).
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* Always `--no-gpg-sign`, always append the trailer `LLM-Generated: true`
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(the `git-commit` skill does this).
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* Never commit `.env`, keys, or `.agents/phase-sessions/`.
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## 10. Quick reference
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| I want to… | Do |
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|---|---|
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| Run it | `uv run mirror serve` → `:8055` |
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| Share / watch | `/mirror` · `/watch` |
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| Debug with an editor | `DEBUGPY=1 uv run mirror serve` (port 5678) |
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| Server truth about mirrors | `GET /api/streams` |
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| What the browser may know | `GET /api/config` |
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| Everything fast, no browser | `uv run pytest -m "not e2e"` |
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| Only the real-desktop test | `MIRROR_REALDISPLAY=1 uv run pytest -m realdisplay` |
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