feat(mitm): translate Antigravity cloudcode end-to-end (Gap B)

[diegosouzapw]

Summary

Closes Gap B from the live MITM validation. The Antigravity IDE speaks cloudcode (the Gemini payload wrapped under request) and expects a cloudcode reply ({response:{candidates}}). The AgentBridge proxy forwarded that envelope verbatim to /v1/chat/completions (OpenAI) → 400 'messages', so the IDE could be decrypted/intercepted but never routed to a provider.

The fix wires the inbound cloudcode path, reusing the already-registered bidirectional translators — no new translators:

• provider.ts: detectFormatFromEndpoint classifies the /antigravity path as sourceFormat="antigravity" (mirrors /messages → claude). The pipeline then translates request antigravity→openai and response openai→antigravity (clientResponseFormat = sourceFormat).
• /v1/antigravity route (new): cloudcode-compatible endpoint — just calls handleChat (mirrors /v1/messages).
• server.cjs: routes cloudcode envelopes → /v1/antigravity and plain OpenAI bodies → /v1/chat/completions, via a testable shim.

Validation

• mitm-forward-target.test.ts — cloudcode envelope → /v1/antigravity, OpenAI → /chat/completions, non-envelope guard — 4
• antigravity-format-detection.test.ts — /antigravity path → antigravity, no disturbance to /messages //responses//chat/completions — 2
• Translators already covered: translator-antigravity-to-openai, translator-resp-openai-to-antigravity
• typecheck:core clean, lint clean
• Live (lab VPS): real Antigravity IDE → MITM → glm-5.2 → cloudcode reply rendered in the IDE — pending the standalone deploy (this PR's provider.ts + route compile into .next; only server.cjs/forwardTarget.cjs are hot-deployable). This is the Rule fix(ci): add environment for npm token access #18 fire-test for the full flow.

Stacking

Stacked on #4285 (Gap A) — server.cjs here builds on the intercept() rewrite from Gap A. Base will retarget to release/v3.8.30 once #4285 merges.

[chatgpt-codex-connector]

You have reached your Codex usage limits for code reviews. You can see your limits in the Codex usage dashboard.

[gemini-code-assist]

Code Review

This pull request introduces support for the Antigravity/cloudcode-compatible inbound endpoint. It adds path-based format detection for 'antigravity', a new /v1/antigravity API route, and MITM proxy forwarding logic to route cloudcode envelopes to this endpoint. Unit tests are also added to verify format detection and forwarding target resolution. The review feedback suggests making the translator initialization synchronous to prevent potential race conditions under concurrent startup requests.

Important

The consumer version of Gemini Code Assist on GitHub is being sunset. Starting June 18, 2026, new organization installations will be blocked, and all code review activity will officially cease on July 17, 2026.
For more details on the timeline and next steps, please review the Help Documentation.

[gemini-code-assist]

Since initTranslators is a synchronous function, wrapping it in an async function and using await introduces an unnecessary asynchronous gap (microtask yield) before initialized = true is set. If multiple requests hit this endpoint concurrently at startup, they can all pass the if (!initialized) check and call initTranslators() multiple times. Removing async/await makes the initialization completely synchronous and race-condition free.

Suggested change

	async function ensureInitialized() {
	if (!initialized) {
	await initTranslators();
	initialized = true;
	console.log("[SSE] Translators initialized for /v1/antigravity");
	}
	}
	function ensureInitialized() {
	if (!initialized) {
	initTranslators();
	initialized = true;
	console.log("[SSE] Translators initialized for /v1/antigravity");
	}
	}

[gemini-code-assist]

Since ensureInitialized is now synchronous, we can remove the await keyword when calling it.

Suggested change

	export async function POST(request: Request): Promise<Response> {
	await ensureInitialized();
	return await handleChat(request);
	}
	export async function POST(request: Request): Promise<Response> {
	ensureInitialized();
	return await handleChat(request);
	}