fix(server): the SQLite WAL file shrinks back after large writes

[t3dotgg]

The server's SQLite -wal file never gets smaller while the server runs. PASSIVE auto-checkpoints copy frames back into the database but keep the file at its largest size. A user with 9 days of uptime on T3 Code 0.0.40 (about 5,000 threads) had a 3.99 GB state.sqlite-wal. It grew by 1.13 GB in 17 hours.

Fix

• Set PRAGMA journal_size_limit to 32 MiB in the shared SQLite setup, right after journal_mode = WAL. SQLite now cuts the -wal file back to 32 MiB on the first commit after a WAL reset.
• In normal use the WAL stays near 4 MB (the default 1000-page auto-checkpoint), so the pragma does nothing there.
• The server and the CLI commands both open state.sqlite through this setup.
• No periodic wal_checkpoint(TRUNCATE). The connection is synchronous and has a 5 s busy handler. A TRUNCATE while another reader holds a snapshot would stall the event loop for up to 5 s.

Limits

This gives back disk space after a WAL reset. It does not stop WAL growth while another connection holds a read snapshot, because the WAL cannot reset then. The server writes through one connection in small transactions, so a 4 GB WAL most likely means a reader like that blocked resets. This PR does not fix the slowdown in the report by itself.

Verification

• New disk-backed test in Sqlite.test.ts. It goes through the real makeSqlitePersistenceLive layer on a temp file. It writes about 1.25x the limit in one statement and checks that the -wal file on disk is larger than the limit. Then it does one small insert and checks that the -wal file is at most the limit. It does not read back the pragma. It runs in about 200 ms.
• With the pragma removed, the test fails: expected 43630832 to be at most 33554432.
• vp test run apps/server/src/persistence/Layers/Sqlite.test.ts
• vp lint apps/server/src/persistence/Layers/Sqlite.ts apps/server/src/persistence/Layers/Sqlite.test.ts
• vp run --filter t3 typecheck

Related

• #12702 runs VACUUM main in WAL mode. That writes a WAL about the size of the database. This limit also cleans up that file after the next WAL reset.
• #5104 was closed because its test only read back a pragma. This test measures the file on disk instead.

Made by Claude Opus 5.5 (1M context) in Claude Code, running in T3 Code.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Improvements
  • SQLite write-ahead log files are now limited to 32 MiB after commits.

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — The change is a focused, tested SQLite storage fix, but it introduces a new hardcoded WAL-size default in the shared production persistence setup. That alters product runtime defaults and warrants human review.

No code changes detected at 8e5593c. Prior analysis still applies.

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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	13.5 KiB	13.5 KiB	+5 B (+0.0%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.1 KiB	7.1 KiB	−8 B (−0.1%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.5 KiB	6.5 KiB	+13 B (+0.2%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	56.3 KiB	56.3 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	10	10	0 (0.0%)	21	✅
Claude	Total thread wire	13.5 KiB	13.5 KiB	−5 B (−0.0%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.1 KiB	7.1 KiB	−8 B (−0.1%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.4 KiB	6.4 KiB	+3 B (+0.0%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	57.0 KiB	57.0 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	9	9	0 (0.0%)	21	✅

Baseline: 2a9832b · PR result: 8e5593c · 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: 114.0 KiB
• Claude decoded thread snapshot: 114.7 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.

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📒 Files selected for processing (2)

• apps/server/src/persistence/Layers/Sqlite.test.ts
• apps/server/src/persistence/Layers/Sqlite.ts

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📝 Walkthrough

Walkthrough

SQLite setup now applies a 32 MiB journal size limit. A test checks that a subsequent commit reduces the WAL file to at most that limit.

Changes

SQLite WAL size limit

Layer / File(s)	Summary
Configure and test the WAL size limit apps/server/src/persistence/Layers/Sqlite.ts, apps/server/src/persistence/Layers/Sqlite.test.ts	Defines and applies a 32 MiB journal_size_limit. The test verifies that the WAL file exceeds the limit after a large transaction and is at or below the limit after a subsequent commit.

Priority: ➖ Normal

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

Change: Bug fix

Suggested reviewers: juliusmarminge

Merge Risk: ⚪ Minimal · up to ef1a0

The change limits WAL size after a later commit for normal persistence workflows. The only uncovered writer is an isolated fixture-mutation utility, so no material merge blocker remains.

🚥 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. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2…
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.
Title check	✅ Passed	The title clearly and concisely describes the main change: reducing the SQLite WAL file after large writes.
Description check	✅ Passed	The description clearly explains the problem, implementation, limitations, testing, and related context. It omits the template checklist and separate "Why" heading, but it provides the required inform…

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