fix: prevent cross-session nested SQLite transactions during bootstrap

[100yenadmin]

Summary

• add a per-DB async transaction mutex for all explicit transaction entry points
• prevent cross-session nested-transaction SQLite failures on a shared DatabaseSync handle
• add regression coverage for cross-store / cross-session contention

Root cause

Lossless-Claw shares one SQLite DatabaseSync connection across sessions, but transaction serialization was only per session. Some transaction scopes span awaited async work (especially bootstrap), so a second session could issue BEGIN on the same connection while the first transaction was still open, triggering:

cannot start a transaction within a transaction

What changed

• added acquireTransactionLock(db) in src/transaction-mutex.ts
• wrapped all explicit transaction entry points with the per-DB mutex:
  • ConversationStore.withTransaction()
  • SummaryStore.replaceContextRangeWithSummary()
  • applyScopedDoctorRepair()
• added test/transaction-mutex.test.ts

Testing

• npx vitest run test/transaction-mutex.test.ts
• npx vitest run test/summary-store.test.ts test/migration.test.ts test/fts5-sanitize.test.ts

Notes / caveats

• This is a containment hotfix for Fix cross-session SQLite transaction collisions during bootstrap/restart #260, not a full transaction-architecture refactor.
• Adversarial review found the mutex is non-reentrant: nested same-DB transaction entry would hang instead of throwing. I did not find an in-tree current call path that triggers that for the patched entry points, so I’m shipping this as the narrow hotfix and treating reentrancy hardening as follow-up work.

[Copilot]

Pull request overview

Introduces a per-database async mutex to serialize explicit SQLite transaction entry points across sessions, preventing cannot start a transaction within a transaction failures when multiple sessions share one DatabaseSync connection during bootstrap/other awaited transaction scopes.

Changes:

• Added acquireTransactionLock(db) (per-DatabaseSync mutex via WeakMap) to serialize transaction entry.
• Wrapped explicit transaction entry points (ConversationStore.withTransaction, SummaryStore.replaceContextRangeWithSummary, applyScopedDoctorRepair) with the mutex.
• Added regression tests covering same-DB serialization, cross-store contention, and basic concurrency stress.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/transaction-mutex.ts	Adds per-DB async mutex used to serialize transaction entry across sessions.
src/store/conversation-store.ts	Wraps withTransaction() with the per-DB mutex to prevent cross-session nested BEGIN IMMEDIATE.
src/store/summary-store.ts	Wraps replaceContextRangeWithSummary() with the per-DB mutex to prevent nested BEGIN.
src/plugin/lcm-doctor-apply.ts	Wraps applyScopedDoctorRepair() transaction with the per-DB mutex.
test/transaction-mutex.test.ts	Adds regression coverage for concurrent transaction entry across sessions/stores.

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[100yenadmin]

TLDR: last patch fix created permanent lockout loop potential for any agent using LCM. For users experiencing the bug, the fix is to switch to legacy and agent will become responsive again. Bug can be recreated via fast restart, /new or /reset. Extremely difficult to debug ie code looked right but timing issues were unforeseeable until tested in production.

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated no new comments.

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[100yenadmin]

@jalehman discovered this bug last night after rollout. critical bug that locks user main agent up + subagents (if they are not isolated) and leaves them unresponsive without any log/errors.

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated no new comments.

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