Summary

Fixes #27143 — changing the embedding model (e.g. text-embedding-3-small → text-embedding-3-large) causes the gateway to get stuck with an infinite "typing..." indicator on Telegram after replying, becoming unresponsive to new messages.

Root cause: A race condition in MemoryIndexManager during safe reindex triggered by the model change. The reindex mutates shared state (this.db, this.vector.*) on the singleton manager instance while concurrent async operations (agent memory search, session warm) use the same instance. Additionally, a falsy dimension check in ensureVectorTable failed to drop stale vec0 tables when dimensions were reset to undefined during the reindex, and an unguarded vec0 INSERT could throw unhandled errors that corrupt the indexing pipeline.

Changes

1. Fix falsy dimension check in ensureVectorTable (manager-sync-ops.ts:223)

   • Changed this.vector.dims && this.vector.dims !== dimensions to this.vector.dims !== undefined && this.vector.dims !== dimensions
   • The truthy check skipped dropVectorTable() when dims was reset to undefined during safe reindex, leaving a stale vec0 table with wrong dimensions

2. Add reindexing guard flag (manager-sync-ops.ts)

   • New protected reindexing = false flag set during runSafeReindex
   • ensureVectorReady returns false when reindexing, causing search to gracefully fall back to the non-vec0 cosine similarity path instead of operating on a temp database that may be closed mid-query

3. Wrap vec0 INSERT in try-catch (manager-embedding-ops.ts:771-783)

   • The vec0 INSERT was the only vec0 write NOT wrapped in error handling — an unhandled throw from a dimension mismatch could corrupt the entire indexing pipeline
   • Now logs the error and continues indexing remaining chunks

4. Improve dropVectorTable error logging (manager-sync-ops.ts:244)

   • Changed from log.debug to log.warn — a failed table drop is a significant issue that was invisible at debug level

Test plan

• All 222 memory module tests pass (pnpm test src/memory/)
• All 67 typing/dispatch tests pass (pnpm test src/channels/typing.test.ts src/auto-reply/reply/reply-flow.test.ts src/auto-reply/reply/followup-runner.test.ts)
• Lint + format pass (pnpm check)
• Manual verification: change embedding model in config, restart gateway, send Telegram message — typing should stop after reply and gateway should remain responsive

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