feat: gemini-cli as a codeoid backend over ACP (bundled, Google-subscription auth)

[saucam]

What

The fourth native harness backend: Google's gemini-cli, driven over ACP (Agent Client Protocol — the standardized editor↔agent JSON-RPC/stdio protocol; gemini-cli exposes it via its stable --acp flag). Auth is the user's Google-account OAuth living in ~/.gemini (free tier / AI Pro / Code Assist) — the same subscription posture as claude and codex; codeoid never touches tokens. Design + spike findings: docs/provider-gemini-acp-design.md (notably: there is no official Antigravity SDK — the community package by that name is an IDE-extension kit pointing the wrong way; ACP is the sanctioned machine surface).

Design

• Shared transport extracted: the codex JSON-RPC client generalizes into providers/jsonrpc-stdio.ts (StdioJsonRpcProcess); codex/rpc.ts is now a thin wrapper baking in the app-server subcommand. All codex tests pass unchanged — same wire behavior, one implementation.
• GeminiAcpProvider (acp/index.ts), deliberately protocol-thin so any ACP-speaking agent can become a backend with a different binary + registry entry:
  • session/new {cwd} → backing session id; session/prompt is the long-running request whose result is the turn boundary (stopReason → turn_done; usage reported as honest zeros — ACP carries none).
  • session/update → agent_message_chunk/agent_thought_chunk stream as text/thinking deltas; tool_call/tool_call_update become tool records (ACP tool kinds map to codeoid names: execute→Bash, read→Read, …).
  • session/request_permission → canUseTool — deny picks the agent's reject option; fail-closed throughout: no gate wired or no reject option offered → cancelled; fs/* and terminal/* client capabilities are declined at initialize (gemini-cli falls back to its own tools, all permission-gated) and any stray server request is refused, not guessed.
  • session/cancel → interrupt (turn resolves stopReason: "cancelled" — covered by a test).
• Bundled like pi: @google/gemini-cli@0.50.0 pinned as an optionalDependency (pure JS — runs under the daemon's own runtime, proven by a live smoke test). Resolution: config → PATH → bundled, with the feat: bundle pi so the backend works with zero install #141 supported-but-unavailable hint path. buildGeminiCliEnv allowlist (GEMINI_/GOOGLE_/LC_ + *_API_KEY; ~/.gemini via HOME).
• Provider id gemini-cli, distinct from the stateless gemini API backend. No wire changes.

Tests

fake-acp fixture models the ACP shape faithfully — session/prompt stays pending until the turn script finishes, permission requests carry allow/reject options, cancellation flips the hanging turn. A1–A9 cover streaming + stopReason, permission allow/deny round-trips, non-gated tool pairs, the structured history seed (one-shot), interrupt-as-cancel, fail-closed unknown requests, missing binary, and lifecycle; plus resolution order, registry activation/unavailable/disabled, and the live bundled smoke. Coverage checked locally before pushing this time: acp/index.ts 100% lines, resolve.ts 93%, shared transport 99%.

Known limits (in the design doc): no session/load resume yet (the canonical-history seed carries context instead), no model catalog (ACP has none — gemini-cli picks from its own config), plan/mode updates ignored for now. A live smoke needs a Google-logged-in gemini-cli.

bun run test (1267 pass), typecheck, lint green.

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 97.40566% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.81%. Comparing base (305e403) to head (4a60413).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/daemon/providers/registry.ts	70.37%	8 Missing ⚠️
src/daemon/providers/acp/resolve.ts	93.54%	2 Missing ⚠️
src/daemon/providers/jsonrpc-stdio.ts	99.09%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #143      +/-   ##
==========================================
+ Coverage   82.55%   82.81%   +0.25%     
==========================================
  Files         101      104       +3     
  Lines       17404    17722     +318     
==========================================
+ Hits        14368    14676     +308     
- Misses       3036     3046      +10     

Flag	Coverage Δ
daemon	82.81% <97.40%> (+0.25%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/config.ts	91.77% <100.00%> (+0.12%)	⬆️
src/daemon/providers/acp/index.ts	100.00% <100.00%> (ø)
src/daemon/providers/codex/rpc.ts	100.00% <100.00%> (+0.92%)	⬆️
src/daemon/providers/env.ts	100.00% <100.00%> (ø)
src/daemon/providers/jsonrpc-stdio.ts	99.09% <99.09%> (ø)
src/daemon/providers/acp/resolve.ts	93.54% <93.54%> (ø)
src/daemon/providers/registry.ts	90.12% <70.37%> (-3.96%)	⬇️

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[github-actions]

🤖 Gemini code review

The implementation of the Gemini ACP provider is very well-structured and generic. However, a potential reliability issue was identified in the shared stdio JSON-RPC transport where synchronous write errors on a destroyed stdin stream can crash the host daemon.

Findings: 🔴 0 · 🟠 1 · 🟡 0 · 🟢 0

Ignored 1 file(s) via ignore globs.

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_{Tokens spent · ⬆️ Input: 18,980 · ⬇️ Output: 285 · Σ Total: 26,663
Total may be higher due to thinking token counts.}