fix(server): sqlite transactions wait for the write lock instead of failing

[juliusmarminge]

Our node:sqlite client (packages/shared/src/nodeSqliteClient.ts) had two gaps:

• Transactions started with a deferred BEGIN. A transaction only takes the write lock at its first write. If another process commits after the transaction's first read (the t3 project CLI writes to the same database), that write fails immediately with SQLITE_BUSY_SNAPSHOT. busy_timeout can't wait that out, so the server command fails even though persistence/Layers/Sqlite.ts sets a 5 s busy timeout for exactly this case. Several orchestration-v2 transactions read before they write, such as the event sink.
• SQLite errors were all UnknownError. node:sqlite puts the result code on errcode, but classifySqliteError reads errno, so busy, locked, unique and constraint failures never got their own reasons.

Fix

• Writable connections begin transactions with BEGIN IMMEDIATE, so they wait for the lock up front. Read-only connections keep the deferred BEGIN, since they can't write. The trade-off: read-only transactions on a writable connection now queue behind other processes' writers. With one server connection behind a semaphore, that's only a cross-process cost.
• The SQLite code is copied from errcode to errno before classifying.

Upstream @effect/sql-sqlite-node (rc.115) already does both. I ported the two changes instead of switching to it, because upstream caches failed prepares for the cache TTL and our client deliberately doesn't (#10584).

Verification

New tests in nodeSqliteClient.test.ts, each run against a temp-file database with a second connection:

• a read, then another connection's write attempt, then our write: the other writer is blocked and our transaction commits;
• a transaction blocked by another writer reports LockTimeoutError;
• unique and not-null violations report UniqueViolation / ConstraintError.

Each new test fails when its fix is reverted. Other results:

• packages/shared typecheck is clean.
• Server persistence and projection tests pass (30 files).
• Desktop browser-cookie import tests pass, as do the migrate-dev-db and t3-sqlite-state script tests; these are the other users of the client.

Model/harness: Claude Opus 5.5 (1M context) via Claude Code in T3 Code.

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[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — The shared SQLite client changes the default transaction mode for writable connections, causing locks to be acquired before reads and potentially changing cross-process concurrency. Error classification and focused tests are straightforward, but the default runtime behavior change merits human review.

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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	4.9 KiB	4.9 KiB	0 B (0.0%)	6.8 KiB	✅
Codex	Thread snapshot wire	3.7 KiB	3.7 KiB	0 B (0.0%)	4.9 KiB	✅
Codex	Live turn WebSocket wire	1.2 KiB	1.2 KiB	0 B (0.0%)	2.0 KiB	✅
Codex	Live turn WebSocket decoded	20.4 KiB	20.4 KiB	0 B (0.0%)	29.3 KiB	✅
Codex	Live turn messages	2	2	0 (0.0%)	8	✅
Claude	Total thread wire	4.9 KiB	4.9 KiB	0 B (0.0%)	6.8 KiB	✅
Claude	Thread snapshot wire	3.7 KiB	3.7 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	20.8 KiB	20.8 KiB	0 B (0.0%)	29.3 KiB	✅
Claude	Live turn messages	2	2	0 (0.0%)	8	✅

Baseline: f870c41 · PR result: b92758d · 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: 106.1 KiB
• Claude decoded thread snapshot: 106.4 KiB

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

[coderabbitai]

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📝 Walkthrough

Walkthrough

The SQLite client now normalizes SQLite error codes before classification and starts transactions with different commands for read-only and writable connections. New tests cover constraint error categories, transaction locking, and lock timeouts.

Changes

SQLite client behavior

Layer / File(s)	Summary
Normalize and classify SQLite errors packages/shared/src/nodeSqliteClient.ts, packages/shared/src/nodeSqliteClient.test.ts	A helper copies a numeric errcode to errno when the cause lacks errno, then classifies errors from database operations. Tests check UniqueViolation for duplicate values and ConstraintError for a NULL value.
Select transaction mode and test locking packages/shared/src/nodeSqliteClient.ts, packages/shared/src/nodeSqliteClient.test.ts	Read-only connections start transactions with BEGIN; other connections use BEGIN IMMEDIATE. File-backed tests check locking between two connections and confirm that a blocked read raises LockTimeoutError when busy_timeout is zero.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant Transaction
  participant nodeSqliteClient
  participant SQLite database
  participant Second SQLite connection
  Transaction->>nodeSqliteClient: Start writable transaction
  nodeSqliteClient->>SQLite database: Begin with BEGIN IMMEDIATE
  Transaction->>SQLite database: Read counter
  Second SQLite connection->>SQLite database: Update counter
  SQLite database-->>Second SQLite connection: Return locked error
  Transaction->>SQLite database: Add ten and commit
  Second SQLite connection->>SQLite database: Add one

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Suggested reviewers: yashranaway

Merge Risk: 🟡 Moderate · up to b9275

Writable transactions still fail immediately when another process is writing, so they do not wait for the lock as intended. Configure a nonzero busy timeout before merging.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: writable SQLite transactions acquire the write lock up front instead of failing after a conflicting write.
Description check	✅ Passed	The description clearly explains the problem, fix, and verification. The Scope and approval information is incomplete: add a link to the triaged issue or maintainer approval, or explain why this focus…
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.

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Actionable comments posted: 1

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Inline comments:
Review comments at @packages/shared/src/nodeSqliteClient.ts:
- Line 285: Configure a nonzero busy timeout on the connection opened in the
nodeSqliteClient setup before transactions use the BEGIN IMMEDIATE mode. Reuse
the existing connection configuration or expose a timeout option, and ensure a
contending transaction can proceed after the current writer releases its lock.

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📥 Commits

Reviewing files that changed from the base of the PR and between f870c41 and b92758d.

📒 Files selected for processing (2)

• packages/shared/src/nodeSqliteClient.test.ts
• packages/shared/src/nodeSqliteClient.ts

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