# FS Module Documentation

## Purpose
Own filesystem API behavior for the web server runtime, including workspace-bound file operations, directory listing, reveal, and background command execution jobs.

## Entrypoints and structure
- `packages/web/server/lib/fs/routes.js`: route registration and runtime-owned state for `/api/fs/*` endpoints.
- `packages/web/server/lib/fs/search.js`: fuzzy filesystem search runtime used by non-FS routes (for example project icon discovery).

## Public exports
- `registerFsRoutes(app, dependencies)` from `routes.js`
  - Registers all filesystem routes:
    - `GET /api/fs/home`
    - `POST /api/fs/mkdir`
    - `GET /api/fs/read`
    - `GET /api/fs/raw`
    - `GET /api/fs/serve/:path(*)`
    - `POST /api/fs/write`
    - `POST /api/fs/upload`
    - `POST /api/fs/delete`
    - `POST /api/fs/rename`
    - `POST /api/fs/reveal`
    - `POST /api/fs/exec`
    - `GET /api/fs/exec/:jobId`
    - `GET /api/fs/list`
  - Owns exec job queue state (`execJobs`) and lifecycle/TTL pruning.
  - Enforces workspace boundary checks with active project + worktree fallback support.
  - The active project directory is validated with `fs.realpath`, so when the project root is itself a symlink the workspace base no longer matches the paths the client sends. Workspace resolution therefore retries against the raw directory the client requested (`requestedDirectory` from `resolveProjectDirectory`) before falling back to worktree roots. Symlinks are still resolved afterwards, and write/exec routes keep their canonical containment check against the resolved base.
- `createFsSearchRuntime({ fsPromises, path, spawn, resolveGitBinaryForSpawn })` from `search.js`
  - Returns `{ searchFilesystemFiles(rootPath, options) }`.
  - Supports fuzzy matching, hidden-file handling, and optional `git check-ignore` filtering.

## Composition contract with `index.js`
- `index.js` provides composition-time dependencies only (platform primitives + callbacks such as `resolveProjectDirectory`, `normalizeDirectoryPath`, and `buildAugmentedPath`).
- `index.js` no longer owns FS route handlers or FS exec job state.

## Notes for contributors
- Keep filesystem policy (workspace root checks, error mapping, exec timeout behavior) inside this module, not in the composition root.
- Filesystem `EPERM`/`EACCES` failures use the stable `reason: "os-permission"` response marker. Policy denials such as workspace-boundary or missing-grant failures must not use that marker because a native folder picker cannot remediate them.
- Read-only routes authorize the requested path against the workspace before resolving symlinks. A symlink reached through the workspace may therefore target a file outside it, while a directly requested outside path still requires an exact-path grant. Write routes keep canonical-target boundary checks.
- If adding new `/api/fs/*` endpoints, add them in `routes.js` and extend this document.
- `GET /api/fs/list` may resolve symlinks with `realpath` to read directory contents, but the response `path` and each entry `path` must stay in the caller's requested path space (`path.join(requestedPath, name)`). Returning real paths breaks file-tree expansion for directories reached through workspace symlinks.
- `POST /api/fs/upload` accepts one `application/octet-stream` body with `path` and optional `overwrite=true` query parameters. The body streams into a same-directory temp file with a 100 MiB default cap configurable through `OPENCHAMBER_FS_UPLOAD_MAX_BYTES`; failed and oversized uploads clean up that temp file. New files commit through an atomic no-replace link, existing files return `409` unless overwrite is explicit, directory targets are rejected, and the destination parent resolves before writing so uploads cannot escape through workspace symlinks.