App-server: GET /v1/artifacts and GET /v1/files for GPUI Preview and Files

[Hmbown]

GPUI Preview/Files fail closed on missing HTTP. Probed and named:

• GET /v1/artifacts — 404
• GET /v1/files — 404

GPUI uses local bounded reads against the workspace root instead. Do not invent a second file store in the desktop.

Reconcile crates/tui/src/runtime_api.rs against today's tip before adding routes. If these exist under another path (like plugins vs /v1/plugins), name it. Otherwise serve list/read (and write+revision for files) with sandbox/permission receipts.

Related: Hmbown/codewhale-apps#564, Hmbown/codewhale-apps#619.

[Hmbown]

Claimed 2026-09-14 — executing agent: Claude Fable 5.1 at Hunter's direction (0.9.14 takeover). Branch feat/app-server-routes-0914 from e9b761c08.

Reconciled against today's tip (crates/tui/src/runtime_api.rs + runtime_api/workspace.rs):

• GET /v1/workspace/files/search and GET /v1/workspace/status exist. There is no directory listing, no bounded file read, and no revision-checked write over HTTP — /v1/files was never a path.
• Artifacts are session-scoped in Core: oversized tool outputs are recorded as ArtifactRecords on the saved session (SavedSession.artifacts) and stored under sessions/<id>/artifacts/ (crates/tui/src/artifacts.rs). GET /v1/sessions/{id} does not expose them today; /v1/artifacts was never a path. Fleet receipt artifacts already have their own route (/v1/fleet/runs/{run_id}/receipts/{task_id}/evidence).

Claimed paths: crates/tui/src/runtime_api.rs (route table only), crates/tui/src/runtime_api/workspace.rs, crates/tui/src/runtime_api/sessions.rs, crates/tui/src/runtime_api/tests.rs, docs/RUNTIME_API.md, CHANGELOG.md.

Plan: GET /v1/workspace/files?path=<dir>&limit= (bounded, sandboxed listing; symlinks refused), GET /v1/workspace/files/read?path=&offset=&limit= (bounded read with a content revision), PUT /v1/workspace/files (revision-checked atomic write through the existing confined WorkspaceFile opener, 409 on drift) and GET /v1/sessions/{id}/artifacts + GET /v1/sessions/{id}/artifacts/{artifact_id} (list/bounded read of the existing records). No second file store; the workspace root is the server's configured workspace only.

[Hmbown]

Progress, 2026-09-14. Implemented on feat/app-server-routes-0914 as dc77f9ab9 (rebased onto cf37ea81ad), Awaiting Verification — an independent coach reviews before it lands.

Routes: GET /v1/workspace/files (bounded listing; .git never served; symlinks listed by kind, never followed), GET /v1/workspace/files/read (byte window + whole-file SHA-256 revision; utf-8 or base64), PUT /v1/workspace/files (atomic write through the existing confined WorkspaceFile opener; 201 create / 200 overwrite with matching expected_revision / 409 on drift naming the current revision / 413 above 4 MiB), GET /v1/sessions/{id}/artifacts and GET /v1/sessions/{id}/artifacts/{artifact_id} over the session's existing ArtifactRecords. Docs in docs/RUNTIME_API.md ("Workspace files and session artifacts").

Evidence so far: runtime_api:: under the hermetic wrapper + nextest ci profile 241 passed / 0 failed; fmt, CI-flag clippy, npm test 66+14+470, check:web, check-versions all green; a live probe against an isolated codewhale app-server --http built from the tree returned every documented status (401 unauthenticated, 403 symlink/.git, 400 traversal, 201→409→200 write sequence, nothing written outside the workspace). Known limits: optimistic concurrency (no lock), 501 on platforms without the confined opener, a byte window that splits a multi-byte character comes back as base64.