- [x] Add `packages/simulation/src/backend` as the home for backend simulation layer replacements, exported from `backend/index.ts` as `simulationReplacements`; `@opencode-ai/simulation` is private/non-published and depends on logic/framework packages (`core`, `llm`, `effect`, OpenTUI), while `server` and `tui` consume it.
- [x] Wire simulation replacements through the server's `makeRoutes` via `Layer.unwrap` + dynamic `import("@opencode-ai/simulation/backend")` gated on `OPENCODE_SIMULATE`, so the simulation module is never loaded eagerly and `makeRoutes` stays synchronous.
- [x] Deny host filesystem escapes loudly: content/mutation operations outside the root fail with `PermissionDenied` simulation errors. Probe operations (`stat`/`access`/`exists`) report `NotFound` outside the root so walk-up loops (project discovery, `findUp`, `globUp`) terminate naturally.
- [x] Add `SimulationFSUtil` replacement (`simulation/fs-util.ts`): wraps the real `FSUtil` layer and reroutes `readDirectoryEntries`, `glob`, and `globUp` — which bypass the injected `FileSystem` via node `fs/promises` and the `glob` package — through the simulated filesystem.
- [x] Fix `LayerNode.hoist` conflict detection to compare node implementations instead of object identity; replacement rewriting produces dependency-rewritten copies of the same node, which previously false-positived as "conflicting implementations".
- [x] Add snapshot seeding from `OPENCODE_SIMULATE_STATE`: `files/` contents of the snapshot directory are read from the host once at layer-build time and seeded into the in-memory tree joined onto the anchor root.
- [x] Verify end to end: `opencode serve` boots with `OPENCODE_SIMULATE=1` + `OPENCODE_SIMULATE_STATE` + path/DB env seams (`OPENCODE_CONFIG_DIR`, `OPENCODE_TEST_HOME`, `OPENCODE_DB=:memory:`); `fs.list`/`fs.read` observe only seeded in-memory files; the anchor directory on the host remains empty after the run.
- [ ] Create the anchor directory + `chdir` + env seam setup automatically in CLI startup when simulation mode is enabled (currently set manually by the runner; a full run needs `OPENCODE_SIMULATE_STATE`, `OPENCODE_CONFIG_DIR`, `OPENCODE_TEST_HOME`, `OPENCODE_DB=:memory:`, and `XDG_*_HOME` pointed into the anchor, plus Bun's `--preload=@opentui/solid/preload` when launched outside `packages/cli`).
- [ ] Assert the anchor directory is still empty at the end of the run (KV/log/flock still write through real XDG paths; they are contained in the anchor by the env seams but not yet in-memory).
- [x] Add run-local simulated network (`packages/simulation/src/backend/network.ts`): replaces the `httpClient` platform node, resolves outbound HTTP against routes supplied at acquisition, denies unknown destinations loudly, and keeps an isolated bounded request log timestamped through Effect `Clock` (design: `simulated-network-llm.md`).
- [x] Add a simulated model provider behind the OpenAI route (`simulated-provider.ts` + `openai.ts`): real provider requests call `SimulatedProvider.Service.stream`; the Drive adapter streams response events back as schema-checked OpenAI Chat SSE consumed by the real protocol pipeline.
- [x] Scope the backend Drive control WebSocket, pending provider invocations, queues, and request fibers to `SimulatedProvider.layerDrive`. JSON-RPC remains at the named manifest's backend endpoint: `llm.attach` replays pending invocations; `llm.chunk`, `llm.finish`, `llm.disconnect`, and `llm.pending` control them; `llm.request` reports provider-native requests.
- [x] Scope the frontend Drive control WebSocket, request queue, renderer, and optional recording timeline to the TUI Effect scope. Server shutdown and request interruption precede renderer destruction; timeline finalization runs last and remains explicitly finishable through `ui.recording.finish`.
- [x] Decode Drive manifests through Effect `Config`, `FileSystem`, and `Schema`, with typed config, not-found, read, and decode failures.
- [x] Answer `https://models.dev/api.json` with an empty catalog in the simulated network; providers come from seeded config (`opencode.json` in the snapshot defines an openai-compatible provider with a dummy `apiKey`, which passes the catalog availability gate and resolves onto the real openai-chat route).
- [x] Fix `buildLocationServiceMap` to apply replacements when compiling hoisted global nodes; platform-node replacements (filesystem, httpClient) were silently ignored inside hoisted globals.
- [x] Verify end to end headless (real route stack in-process + backend control WS: prompt -> `llm.request` -> driver chunks -> assistant message contains driver text; script: `packages/server/script/e2e-sim.ts`) and through the TUI (fake renderer, both sockets: type + submit via TUI WS, answer `llm.request` via backend WS, assistant reply rendered on screen; script: `packages/tui/script/sim-llm-driver.ts`).
- [ ] Add simulated process registry (shell via `just-bash`, minimal fake `git`, deny unsupported spawns).
- [ ] Trace filesystem, process, and simulated provider activity (network requests are traced in the backend network log ring buffer; provider trace records still need adding on the backend control server).
- Wire simulation replacements through `AppNodeBuilder.build(...)` and `AppNodeBuilderV1.build(...)`.
- Create a real, empty anchor directory (`mkdtemp`) and `process.chdir` into it before any command resolves its working directory; skip creation when the runner already spawned the app inside an anchor.
- Root the in-memory filesystem at `process.cwd()` (the anchor). No cwd monkey-patching: cwd, `$PWD`, and `path.resolve()` stay truthful.
- Add snapshot loading from `OPENCODE_SIMULATE_STATE`: read the snapshot directory once at startup and seed the in-memory filesystem (snapshot `files/` paths joined onto the anchor root), config, env, and optional LLM/network state from it.
- Route config/data/state/cache/temp paths into the simulated space using existing env seams (`OPENCODE_CONFIG_DIR`, `OPENCODE_TEST_HOME`, `OPENCODE_DB=:memory:`), set before `packages/core/src/global.ts` import-time path setup runs.
- Deny host filesystem escapes loudly (paths outside the anchor root fail with typed simulation errors).
- Assert the anchor directory on the host is still empty at the end of the run; anything written there means a code path bypassed the simulated filesystem.
- Add simulated network registry and deny unknown external network by default.
- Add scriptable LLM boundary.
- Add simulated process registry:
- shell through `just-bash` against the simulated filesystem.
- minimal fake `git` support for discovery/status paths.
- deny unsupported process spawns.
- Add simulation-gated backend control routes, proxied only through the frontend WebSocket.
- Expose backend methods through the frontend server: filesystem seed/write, network register, LLM enqueue, backend snapshot.
- Trace filesystem, network, LLM, process, and backend control activity.
Done when:
- Unknown network fails with a simulation error.
- Host filesystem escape fails with a simulation error.
- The anchor directory on the host is empty after a run.
- The app boots from a snapshot directory via `OPENCODE_SIMULATE_STATE` and observes the seeded project files, config, and env through normal app paths.
