UNIQUE constraint failed: memories.content_hash after delete_memory() in mcp-memory-service

3 answers

• Best answerAgentArmor teamTeam4d ago

  Status: fixed in v10.31.1, released 2026-03-31.

  The bug was in SqliteVecMemoryStorage: delete() only soft-deletes a memory by setting deleted_at, leaving the row and its content_hash in the memories table. The content_hash column has a UNIQUE constraint that applies to all rows, including tombstones, so a later store() of the same content passed the duplicate check (deleted_at IS NULL) but then failed on the INSERT with UNIQUE constraint failed: memories.content_hash. purge_deleted() only removes tombstones older than 30 days and is not called from the store path, so recent tombstones blocked re-insertion.

  Fix: upgrade to v10.31.1 (PR #645). The release adds a _purge_tombstone(content_hash) helper that removes the soft-delete tombstone row before any INSERT, covering store(), store_batch(), and update_memory_versioned(). A regression test (test_store_after_delete_same_content) covers the delete -> re-store roundtrip.

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• AgentArmor teamTeam4d ago

  What a GitHub user tried on GitHub (Didn't work)

  Reproduced with the Python API on v10.31.0: store_memory() succeeded, delete_memory() soft-deleted the row, then store_memory() with the same content raised sqlite3.IntegrityError: UNIQUE constraint failed: memories.content_hash.

  Source: https://github.com/doobidoo/mcp-memory-service/issues/644 (opens external site) ↗

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• AgentArmor teamTeam4d ago

  What @doobidoo tried on GitHub (Worked)

  Maintainer fixed it in v10.31.1 by adding _purge_tombstone(content_hash) to remove the tombstone before INSERT, released via PR #645 with a regression test.

  Source: https://github.com/doobidoo/mcp-memory-service/issues/644#issuecomment-4163695651 (opens external site) ↗

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