fix(antigravity): persist replay expiry

[luvs01]

Summary

• Mark Antigravity replay snapshot state dirty when the periodic or lazy TTL sweep removes at least one in-memory session.
• Coalesce a sweep into one durable mutation generation while preserving the existing per-session deletion and byte-accounting path.
• Add a deterministic regression proving that a signature already flushed to disk is removed by the next explicit sweep and flush.

The replay cache already expired entries in memory, but expiry did not advance the snapshot mutation generation. During an idle period, the protected antigravity-replay.json file could therefore retain an opaque thought signature after its one-hour in-memory lifetime until some unrelated replay mutation or a later load rewrote the file.

Verification

• Bun 1.3.14: bun test --isolate tests/google-antigravity-replay.test.ts tests/state-store-sweeper.test.ts (72 pass)
• Bun 1.4.0-canary.1: the same focused command (72 pass)
• Bun 1.3.14 and Bun 1.4.0-canary.1: bun run typecheck
• Bun 1.3.14: bun run privacy:scan
• Latest-base integration sanity: bun test --isolate tests/model-rename-migration.test.ts (9 pass)
• Related lifecycle tests: bun test --isolate tests/state-store-sweeper.test.ts tests/shutdown-drain.test.ts tests/server-background-lifecycle.test.ts tests/storage-mutation-race.test.ts (43 pass)
• Regression activation: with only the production fix hunk removed, the new test fails because the durable snapshot still contains one session; restoring the fix makes it pass.
• Independent exact-diff review found no P0/P1/P2 issue in generation, debounce, flush, load, clear, or eviction interactions.
• Rebased onto dev at b583d64970e087bb85fa04b7356889070e06a0b5; the replay/sweeper plus latest usage/settings focused set passes on Bun 1.3.14 and Bun 1.4.0-canary.1 (120 pass each), with typecheck passing on both runtimes.
• Full Bun 1.3.14 suite was attempted and is not claimed green: unrelated Windows effective-account lookup failures and existing 5-second integration timeouts cascaded before Bun crashed after 1,355 seconds with an internal index-out-of-bounds panic (exit 3, peak RSS 2.08 GB). The changed subsystem and lifecycle suites above pass on the exact head.

Checklist

• Scope stays focused and avoids unrelated cleanup.
• Docs or release notes were updated when needed. This is an internal persistence-lifecycle correction with no user-facing configuration or command change.
• Security-sensitive changes were reviewed for secrets, auth, and unsafe defaults. The regression uses a synthetic signature and the implementation adds no logging or response fields.

Review readiness checklist

This PR stays in draft until every box below is ticked. Tick all four boxes once the requirements are met:

• All CI tests are green on my local testing.
• I pushed my PR to the latest dev commit.
• I resolved all correct Codex and CodeRabbit findings.
• My PR is ready for review.

Summary by CodeRabbit

• Bug Fixes

  • Expired replay sessions are now removed individually and their associated stored signatures are deleted from durable storage.
  • Persisted snapshots are updated automatically when expired sessions are swept.

• Tests

  • Added coverage confirming expired sessions and signatures are removed from saved snapshots.

[github-actions]

✅ Deterministic PR hygiene checks passed.

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ℹ️ Recent review info

⚙️ Run configuration

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Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 423338d5-a8c7-4a4e-8553-065849e3c1bb

📥 Commits

Reviewing files that changed from the base of the PR and between 3982dae and eb9fa39.

📒 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 expiry sweep now marks the durable snapshot dirty when it deletes sessions. A durability test verifies that flushing the snapshot removes expired sessions and their stored signatures.

Changes

Replay expiry persistence

Layer / File(s)	Summary
Mark expired-session deletions for persistence src/adapters/google-antigravity-replay.ts, tests/google-antigravity-replay.test.ts	deleteExpiredReplaySessions tracks deletions and marks the replay snapshot dirty at lines 525–533. The asynchronous test at lines 607–620 verifies that flushing after expiry removes all sessions and stored signatures.

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

Mergeability Score: 🟡 Moderate · up to eb9fa

The replay expiry fix is localized and its targeted validation passes, but the PR is still marked draft with required readiness checks incomplete, including a non-green full-suite result. Merge should wait for those checks to be completed or explicitly accepted by the owner.

Possibly related PRs

• lidge-jun/opencodex#1434: Introduced the replay-cache expiration and durable snapshot logic updated by this change.

Suggested reviewers: lidge-jun, yuxin-qiao

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: persisting expired Antigravity replay entries.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[github-actions]

⏳ DRAFT

• review readiness checklist open (2/4 boxes ticked).

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• Tick all four boxes in the PR description once you're done (currently 2/4).

Review readiness checklist

• ⬜ All CI tests are green on my local testing.
• ✅ I pushed my PR to the latest dev commit.
• ✅ I resolved all correct Codex and CodeRabbit findings.
• ⬜ My PR is ready for review.

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[luvs01]

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[luvs01]

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