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+---
+title: Mnemosyne
+type: system
+status: active
+created: 2026-07-22
+updated: 2026-08-02
+verified_on: 2026-08-02
+confidence: high
+tags: [memory, mnemosyne, backend]
+sources: [live-probe, mnemosyne-db, config, ops-profile-config]
+---
+
+# Mnemosyne
+
+## Purpose
+Primary agent memory store for Hermes.
+
+## Current Configuration
+- **Provider:** `mnemosyne`
+- **Enabled:** true
+- **Auto sleep:** true
+- **Default scope:** `session`
+- **Memory char limit:** 5000
+- **User char limit:** 3000
+- **Vector type:** int8
+- **Profile isolation:** true
+- **Shared surface read:** true
+- **Shared surface path:** `data/shared/mnemosyne.db`
+- **Skip contexts:** cron, flush, subagent, background, skill_loop
+- **Reflect max calls per session:** 3
+- **Sync roles:** user
+- **Flush every:** 6 turns
+- **Embedding model:** `BAAI/bge-small-en-v1.5` (384 dims)
+- **Embeddings via API:** false (local fastembed)
+
+## Database Stats (2026-08-02)
+| Table | Rows | Notes |
+|---|---|---|
+| `working_memory` | 1,476 | Active memories |
+| `episodic_memory` | 458 | Consolidated summaries |
+| `memory_embeddings` | 158 | Only working memories — **0 episodic** |
+| `memory` (legacy) | 2,181 | Old table, not migrated |
+| `vec_working` | 159 | Vector index rows |
+| Shared surface | 0 | Empty — cross-agent sharing not functional |
+
+## Known Issues
+
+### Vector embedding coverage gap
+- **Only 159/1,476 working memories (10.8%)** have vector embeddings
+- **0/458 episodic memories** have embeddings
+- Semantic search (`mnemosyne_recall`) falls back to FTS5 keyword matching for ~90% of working and 100% of episodic memories
+- This means recall quality is degraded — vector similarity can only search a tiny fraction of the memory store
+- **Root cause:** The embedding pipeline (fastembed) never processed the bulk of memories. The `vec_working` table was rebuilt once (Jul 18) but only captured 159 rows.
+- **Fix needed:** Backfill embeddings for all working and episodic memories. This requires running the embedding pipeline across the full dataset.
+
+### Profile isolation chosen over shared surface
+|- The ops profile was enabled with mnemosyne on 2026-08-02
+|- **Decision:** `profile_isolation: true` was set on ops, giving each profile its own independent memory bank — zero cross-contamination
+|- `data/shared/mnemosyne.db` exists with 0 rows; cross-profile sharing is intentionally unused
+|- This means Tusk (ops) and Rhino (default) do not share memories, which is the desired behaviour
+|- Config in `~/.hermes/profiles/ops/config.yaml`: `memory.mnemosyne.profile_isolation: true`, `allow_tool_override: false`, `shared_surface_read: false`
+|- Verified end-to-end on 2026-08-02: memory writes land correctly in both profiles independently
+
+### Legacy table not migrated
+- 2,181 rows in the old `memory` table are not in the new `working_memory`/`episodic_memory` system
+- These are only accessible via the legacy `memory` tool, not via `mnemosyne_recall`
+
+## Known Management Jobs
+- Mnemosyne Auto-Consolidate every 30m — script: `consolidate_mnemosyne.sh`, mode: no-agent
+- Mnemosyne DB Backup weekly Sunday 03:00 — script: `mnemosyne-backup.sh`, mode: no-agent
+- Mnemosyne Health Monitor every 12h — skill: `mnemosyne-operations`, reports only on exception
+- Mnemosyne Watchdog every 15m — script: `mnemosyne-watchdog.py`, mode: no-agent
+
+## History and Evidence
+- **2026-08-01 incident:** Automatic conversational capture was broken by stringified structured YAML, especially `sync_roles: "['user']"`. Fixed by rewriting with native YAML types. See [[incidents/2026-08-01-mnemosyne-capture-failure]].
+- **2026-08-01 cleanup:** Legacy always-injected memory reduced from 8,013 bytes to 4,998 bytes (memory) and 2,958 bytes (user).
+- **2026-07-29 incident:** `memory.mnemosyne.tools: None` caused schema loading warnings. Fixed by removing the line. See [[incidents/2026-07-29-mnemosyne-relay]].
+- **2026-07-29 relay scope corruption:** `RuntimeError: scope handle is not at the top of the stack` — 3 occurrences, self-resolved.
+
+## Related
+- [[concepts/agent-memory]]
+- [[comparisons/memory-backends]]
+- [[incidents/2026-08-01-mnemosyne-capture-failure]]
+- [[incidents/2026-07-29-mnemosyne-relay]]