fix(antigravity): keep the signature from a standalone thought part

[devmello]

Summary

Fixes #897. When Antigravity returns the reasoning signature on its own thought part instead of on the functionCall part, the replay cache dropped it, so the next turn went out unsigned and upstream rejected it. The cache now pairs a standalone thought signature with the functionCall that follows it in the same parts array. A signature on the call part itself still wins, an unpaired one is dropped at the end of the array, and byte accounting is untouched. Pairing stays within one observed array; a thought and its call split across streamed chunks is out of scope since the reported captures are same-array.

Verification

• Four new tests in tests/google-antigravity-replay.test.ts: the standalone shape replays, the call's own signature wins, no backward or cross-observe pairing, and non-thought parts do not attach.
• Unit repro: [{thought, thoughtSignature}, {functionCall}] lost its signature before the fix and round-trips after.
• bun run test, typecheck, lint:gui, privacy:scan.

Checklist

• Scope stays focused and avoids unrelated cleanup.
• Docs or release notes were updated when needed.
• Security-sensitive changes were reviewed for secrets, auth, and unsafe defaults.

Summary by CodeRabbit

• Bug Fixes

  • Improved replay handling for function calls preceded by standalone thought signatures.
  • Ensured the correct signature is used when multiple signatures are present.
  • Prevented signatures from being incorrectly reused across unrelated events or attached to unsupported content.
  • Preserved existing validation and cache-size protections for valid replayed calls.

• Tests

  • Added coverage for signature pairing, precedence, isolation, and invalid attachment scenarios.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

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Run ID: b19c1563-16c3-4b1d-8da5-691bb48215be

📥 Commits

Reviewing files that changed from the base of the PR and between 6a7351b and db293dc.

📒 Files selected for processing (2)

• src/adapters/google-antigravity-replay.ts
• tests/google-antigravity-replay.test.ts

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📝 Walkthrough

Walkthrough

The replay observer now carries signatures from standalone thought parts to the next function call in the same parts array. Call-local signatures take precedence. Tests cover pairing order, state isolation, and invalid non-thought signatures.

Changes

Antigravity replay cache

Layer / File(s)	Summary
Pending signature association and validation src/adapters/google-antigravity-replay.ts:368-369, src/adapters/google-antigravity-replay.ts:385-407, tests/google-antigravity-replay.test.ts:67-112	The observer stores signatures from standalone thought parts and applies them to the next function call. A call’s own signature takes precedence, and pending state is cleared after pairing. Calls without a usable signature or identity remain skipped. Tests verify immediate forward pairing, precedence, no backward or cross-observation pairing, and rejection on non-thought parts.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers: lidge-jun

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the primary change: preserving signatures from standalone thought parts in Antigravity replay.
Linked Issues check	✅ Passed	The adapter and tests implement standalone thought-signature pairing, call-signature precedence, same-array limits, and unchanged replay mechanics required by issue #897.
Out of Scope Changes check	✅ Passed	The changes are limited to Antigravity replay pairing logic and focused tests directly related to issue #897.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[Ingwannu]

Confirmed as a real provider-compatibility defect. The patch keeps the repair narrow: same-array forward pairing only, call-local signature precedence, no cross-observation carry, no non-thought attachment, and no change to the existing replay cache limits or identity key.

Verification:

• applied cleanly on current dev (3cd75ab0)
• bun test tests/google-antigravity-replay.test.ts: 39 passed
• bun run typecheck: passed
• repository Cross-platform CI and React Doctor: passed

No blocking findings.