fix(antigravity): bootstrap project via loadCodeAssist + fetchAvailableModels fallback

[NomenAK]

What

Bootstrap Antigravity project assignment via :loadCodeAssist before model discovery, and prefer /v1internal:fetchAvailableModels over /v1internal:models (which 404s for free-tier accounts).

Why

Two root causes were observed when antigravity discovery 404'd on every container boot:

1. /v1internal:models requires a prior /v1internal:loadCodeAssist call to assign a project id to the OAuth token. Without that bootstrap, the server has no context and returns 404 for all three base URLs (prod, daily, sandbox).
2. Even with the bootstrap, /v1internal:models is dead for free-tier accounts. The correct endpoint is /v1internal:fetchAvailableModels, which returns 200 with the full model list.

Both gaps confirmed by direct probing with a live token.

How

• New open-sse/services/antigravityProjectBootstrap.ts (~129 lines): ensureAntigravityProjectAssigned(accessToken, opts?) — idempotent loadCodeAssist call with per-token memoization, 8s timeout per URL, tries all 3 base URLs, non-fatal on failure
• Modify src/app/api/providers/[id]/models/route.ts:
  • Call ensureAntigravityProjectAssigned(accessToken) immediately after resolveAntigravityVersion()
  • Discovery loop iterates [...fetchAvailableModelsUrls, ...modelsDiscoveryUrls] — fetchAvailableModels first, :models kept as paid-tier fallback
• 9 new unit tests in tests/unit/antigravity-discovery-bootstrap.test.ts: memoization, fallthrough, non-fatal errors, auth headers, ordering, etc.
• Exports clearAntigravityProjectCache and getAntigravityProjectFromCache test helpers

Notes

The fix keeps :models in the fallback list because paid-tier accounts may still use it — happy to remove it entirely if you prefer the cleaner code path. Also happy to revise the cache eviction strategy or the timeout values if they don't fit upstream defaults.

[gemini-code-assist]

Code Review

This pull request introduces a bootstrap mechanism for the Google Cloud Code Assist API to ensure a project context is assigned to OAuth tokens before model discovery. It adds a new service, antigravityProjectBootstrap.ts, which handles memoized project assignment and integrates this step into the model discovery route. Comprehensive unit tests were also added to verify the bootstrap logic and execution order. Review feedback recommends using AbortSignal.timeout() for more concise timeout management and adopting the Headers constructor in tests to improve type safety when accessing request headers.

[gemini-code-assist]

For improved readability and to leverage modern platform APIs, you can simplify the timeout logic by using AbortSignal.timeout(). This avoids the need for manual setTimeout and clearTimeout management, making the code more concise and less error-prone.

    try {
      const response = await fetchImpl(url, {
        method: "POST",
        headers: getAntigravityHeaders("loadCodeAssist", accessToken),
        body: JSON.stringify({ metadata: getAntigravityLoadCodeAssistMetadata() }),
        signal: AbortSignal.timeout(BOOTSTRAP_TIMEOUT_MS),
      });

      if (!response.ok) {
        console.warn(
          `[models] antigravity loadCodeAssist failed at ${url} (${response.status}) — trying next`
        );
        continue;
      }

      const data = (await response.json()) as Record<string, unknown>;

      // cloudaicompanionProject may be a plain string or an object with an id field.
      const raw = data.cloudaicompanionProject;
      let projectId =
        typeof raw === "string"
          ? raw.trim()
          : raw &&
              typeof raw === "object" &&
              typeof (raw as Record<string, unknown>).id === "string"
            ? ((raw as Record<string, unknown>).id as string).trim()
            : "";

      if (projectId) {
        return projectId;
      }

      console.warn(
        `[models] antigravity loadCodeAssist at ${url} returned no project id — trying next`
      );
    } catch (error) {
      const msg = error instanceof Error ? error.message : String(error);
      console.warn(`[models] antigravity loadCodeAssist threw for ${url}: ${msg} — trying next`);
    }

[NomenAK]

Already addressed in 950aab2 (pushed after this review) — swapped the manual setTimeout / clearTimeout for AbortSignal.timeout(8_000). Thanks for the suggestion.

[gemini-code-assist]

The type assertion as Record<string, string> is not entirely safe because init.headers can have other types (e.g., a Headers object or string[][]). Using the Headers constructor is a more robust and type-safe way to parse the headers.

Suggested change

	const auth = (init?.headers as Record<string, string> | undefined)?.Authorization ?? "";
	const auth = new Headers(init?.headers).get("Authorization") ?? "";

[NomenAK]

Already addressed in 950aab2 — both headers assertions in the test now use new Headers(init.headers) and .get(...) instead of the unsafe Record<string, string> cast. Thanks.

[gemini-code-assist]

To improve type safety and robustness, it's better to use the Headers constructor to parse the headers rather than relying on a potentially unsafe type assertion. This ensures the code correctly handles all possible types for init.headers.

Suggested change

	capturedAuth = (init?.headers as Record<string, string> | undefined)?.Authorization ?? null;
	capturedAuth = new Headers(init?.headers).get("Authorization") ?? null;

[NomenAK]

Same fix in 950aab2 — second Headers ctor swap applied at the same time. Thanks for the pair of catches.

[NomenAK]

All 3 suggestions applied in 950aab2:

• AbortSignal.timeout() replaces the manual AbortController + setTimeout/clearTimeout pair (drops the finally block).
• Both test sites use new Headers(init?.headers).get("Authorization") instead of the Record cast.

Tests still pass (9/9 in antigravity-discovery-bootstrap.test.ts). Thanks for the review.

[diegosouzapw]

Thanks @NomenAK! Your contribution has been integrated into release/v3.8.0 and will ship in the upcoming release.

The PR branch was synced with the latest release/v3.8.0 (no conflicts) and squash-merged. The loadCodeAssist bootstrap + fetchAvailableModels fallback fix the antigravity model discovery flow nicely.

Reviewed and merged via the /review-prs-cc workflow.