fix(usage): repeat usage scans no longer decode unchanged Antigravity databases

[t3dotgg]

The Usage page made the desktop app show "reconnecting" for users with a large Antigravity history (#13852). Every getUsageSummary decoded every Antigravity .db on the server thread, even files that had not changed, so the event loop stalled for seconds on each request.

Now each database is decoded once and reused on later scans while the database and its -wal sidecar keep the same size, mtime, and ctime. The WAL is in the key because new rows land there before the main file changes. ctime is in the key because it moves on any write, even one that restores size and mtime. Aliases still merge across every database before the date window applies.

This does not fix the first scan after a server restart. The cache is in memory only, and the read still runs on the main thread. Those are follow-ups on the issue.

Takeover of #13902 by @derektrimm, rebased onto current main with no code changes. The original commits keep Derek's authorship.

Proof: vp test run src/usage/ (145 passed) and the server typecheck. I disabled the cache, then the WAL part of the key, then the ctime part, and each time exactly one new test failed. On 30 Antigravity databases copied from a real machine, a repeat scan went from 27 ms to 3 ms with the same 618 records.

🤖 Generated with Claude Code (Claude Opus 5.5)

[macroscopeapp]

Approvability

Verdict: Approved at 19c271f

Macroscope's review found this PR approvable — This is a focused usage-performance fix that reuses parsed Antigravity data only when the database and WAL are unchanged, while preserving alias merging and date filtering. Targeted tests cover cache reuse, WAL updates, and rewritten databases, with no product-default or static-analysis changes.

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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	5.0 KiB	4.9 KiB	−23 B (−0.5%)	6.8 KiB	✅
Codex	Thread snapshot wire	3.8 KiB	3.8 KiB	0 B (0.0%)	4.9 KiB	✅
Codex	Live turn WebSocket wire	1.2 KiB	1.2 KiB	−23 B (−1.9%)	2.0 KiB	✅
Codex	Live turn WebSocket decoded	20.9 KiB	20.8 KiB	−41 B (−0.2%)	29.3 KiB	✅
Codex	Live turn messages	2	1	−1 (−50.0%)	8	✅
Claude	Total thread wire	5.0 KiB	5.0 KiB	0 B (0.0%)	6.8 KiB	✅
Claude	Thread snapshot wire	3.8 KiB	3.8 KiB	0 B (0.0%)	4.9 KiB	✅
Claude	Live turn WebSocket wire	1.2 KiB	1.2 KiB	0 B (0.0%)	2.0 KiB	✅
Claude	Live turn WebSocket decoded	21.2 KiB	21.2 KiB	0 B (0.0%)	29.3 KiB	✅
Claude	Live turn messages	2	2	0 (0.0%)	8	✅

Baseline: 0647c48 · PR result: 19c271f · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 108.5 KiB
• Claude decoded thread snapshot: 108.8 KiB

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[coderabbitai]

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 0647c48 and 19c271f.

📒 Files selected for processing (3)

• apps/server/src/usage/UsageService.ts
• apps/server/src/usage/antigravityUsageReader.ts
• apps/server/src/usage/usageTranscriptReader.test.ts

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📝 Walkthrough

Walkthrough

Antigravity usage scans can reuse parsed candidates when the database and WAL fingerprints are unchanged. UsageService now retains and passes the cache across scans. Tests cover cache reuse, database rewrites, and WAL-only updates.

Changes

Antigravity usage cache

Layer / File(s)	Summary
Cache validation and reader tests apps/server/src/usage/antigravityUsageReader.ts, apps/server/src/usage/usageTranscriptReader.test.ts	The reader caches parsed candidates using database and WAL fingerprints based on size, modification time, and change time. Tests cover cache reuse under an exclusive lock, a database rewrite with restored size and modification time, and WAL-only changes.
Cache lifecycle across scans apps/server/src/usage/UsageService.ts	UsageService creates a cache and passes it to the Antigravity reader during scans. The documentation distinguishes Antigravity caching from OpenCode live database reads.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~12 minutes

Change: Bug fix

Suggested reviewers: maria-rcks

Merge Risk: ⚪ Minimal · up to 19c27

No actionable issue remains from this review. The change is mergeable after normal checks.

🚥 Pre-merge checks | ✅ 3 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description provides detailed problem, change, limitations, and verification information. However, it does not use the required section headings, and the Scope and approval information does not in…	Organize the description under the required Problem, Change, Scope and approval, and Verification headings. Add a link to the triaged issue or maintainer approval comment, or explain why this focused fix qualifies for the obvious-bug exempt…

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: repeat usage scans reuse unchanged Antigravity database results instead of decoding them again.
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.

Full details: Description check

Explanation

The description provides detailed problem, change, limitations, and verification information. However, it does not use the required section headings, and the Scope and approval information does not include explicit maintainer approval or explain why the fix qualifies for an exemption.

Resolution

Organize the description under the required Problem, Change, Scope and approval, and Verification headings. Add a link to the triaged issue or maintainer approval comment, or explain why this focused fix qualifies for the obvious-bug exemption.

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