retrieval-memory-brain

name

retrieval-memory-brain

description

The MAP of Murmur's shipped retrieval + agent-memory stack by file:symbol (hybrid fusion, FTS5/vec0 schema, embedding models, the reranker seam, bitemporal facts, consolidation, the entity graph, the eval harness) plus the MEASURED gaps and the load-bearing invariants. Use for any task touching retrieval quality, chunking, embeddings, reranking, fact/memory storage, consolidation, entity graph, or RAG eval. Not for embedder runtime cost on Metal (ondevice-model-perf).

retrieval-memory-brain — the shipped brain, by symbol

The knowledge map for Murmur's retrieval + agent-memory stack (the "brain"). This file is the LEAN index: what exists, where, and the invariants you cannot break. The deep, code-grounded material lives in references/*.md — load the one you need. Trust code, not this map: grep the symbol in the current tree before you rely on it (commands and storage are split across growing domain modules, and line anchors drift).

Pairs with the memory-retrieval-architect agent — dispatch it (or follow this skill yourself). Because every change here touches visibility_clause, lock-security-reviewer is a required second gate, and the recall verdict is adversarial-verifier's.

Hybrid retrieval map

Ask / related-notes / MCP retrieve through Db::search_hybrid_visible (storage/db.rs), which fuses three visibility-gated legs:

• FTS (keyword/BM25) — search_visible_impl + raw scores from fts_meeting_scores (external-content FTS5 over note + transcript + augmented topic chunks; -bm25, higher-better). Implicit-AND phrase match.
• KNN (vector) — search_semantic_visible + raw distances from knn_meeting_distances over the vec0 KNN tables (vec_chunks / topic_vec_chunks). Only informative when the real e5 model is present.
• Entity graph (GraphRAG-lite) — entities_matching_query → meetings_mentioning_entities_visible (deterministic co-mention neighbourhood, no LLM), positionally scored.

Fusion is embed::score_fuse(fts, knn, graph) — weighted (SCORE_FUSE_W_FTS/_W_KNN/_W_GRAPH = 0.4/0.4/0.2), min-max-normalized per leg, KNN distance inverted to 1/(1+d), query-adaptive empty-leg redistribution, ties → id-ASC. rrf_fuse (RRF_K=60) is the fallback + the doc-hit fuser (fuse_doc_hits). Full mechanics + the measured gaps: references/hybrid-fusion.md.

Embeddings & schema

• Model: multilingual-e5-small (selected_embed_model default; mmlw-retrieval-e5-small is the Polish-first alt). Real encoder embed/candle_bert.rs; active_embedder returns it when the model dir is present, else the hash-bag StubEmbedder (semantic == noise on the stub — always check which).
• EMBED_DIM = 384 is the vec0 column width. A model swap that stays 384 is ZERO schema migration but a full RE-INDEX (reindex_embeddings — vectors from different models are not comparable).
• e5 asymmetric prefixes are load-bearing: QUERY_PREFIX="query: " / PASSAGE_PREFIX="passage: " (embed_query/embed_passage). Chunking: chunk_note (~800 chars) / chunk_transcript (~1000+150 overlap) / augment_chunk_text (deterministic contextual header). Details: references/embeddings-and-reranking.md.

Reranker seam

rerank.rs (L1.4, Ask-only). Reranker trait; StubReranker (identity — no-model/cloud floor); PromptedReranker (pointwise {"relevant": bool} per candidate over the resident on-device reasoner, RERANK_TIMEOUT_MS=3000, RERANK_TOP_K=10). active_reranker → stub for "stub"/"cloud:*" reasoners (on-device-only, never cloud egress). Candidates arrive pre-gated → opens no read path. It is a STUB-grade lever today (measured: adds no value). Direction (cross-encoder / ColBERT): references/embeddings-and-reranking.md.

Bitemporal fact memory + consolidation

• Facts (facts.rs): reconcile_facts (pure) implements the Zep invalidate-not-delete pattern — a changed fact CLOSES the old row (valid_to) and ADDS a new open one; history is preserved. Parallel user_facts ("me") in user_memory.rs.
• Consolidation (memory.rs, L2.1 generative-agents recipe): run_consolidation_pass / consolidation_tick (hourly). Scores facts by composite_score = recency (0.995^hours) · importance · relevance (0.4/0.4/0.2); reflects important/populous entities into memory_rollups; GCs each rollup against its scope's current fact_set_hash. Details + invariants: references/memory-and-consolidation.md.

The measured gaps (honest, 2026-07-10)

Per eval/results/rag-bakeoff-real-vault.md — these are MEASURED, do not contradict without a re-run:

• hybrid 0.90 < semantic 0.95 on a deliberately semantic-favouring real query set is CORRECT hybrid behaviour, not a bug. Three fusion-tuning fixes all failed (adaptive redistribution = 0 change; OR-match FTS = reverted, regressed the CI baseline; graph-drop = 0 change — the "graph noise" hypothesis was WRONG). On keyword queries hybrid 0.90 > semantic 0.84 — hybrid is the robust choice.
• 18/20 hard queries have an EMPTY FTS leg (implicit-AND phrase match misses paraphrase/cross-lingual).
• The reranker adds no measured value (10 candidates exhaust the 3 s deadline → identity). A real win needs a cross-encoder, not sequential pointwise LLM calls.

The invariants

1. Every retrieval leg + every memory read is gated (visibility_clause / a *_visible reader). A sealed-not-unlocked meeting leaks nothing through FTS, KNN, graph, reranker, MCP, or a rollup.
2. Consolidation reads with the EMPTY unlock set (memory.rs no_unlocks = HashSet::new()) — derived memory never surfaces sealed content, even in a session where the folder is unlocked.
3. Embedders/rerankers are on-device or a stub — NEVER cloud (no candidate-snippet egress).
4. Consolidation purges on seal (purge_memory_rollups_tx inside every seal tx; scores/facts cascade).
5. Any chunk/model/prefix change MANDATES reindex_embeddings (never mix vectors from two models).

Because you inevitably touch a gate or the fact/rollup store, the lock-security-reviewer is a required second gate on any change here (see .codex/rules/lock-model.md).

The eval harness + honesty bar

eval/{mod,bakeoff}.rs. run_bakeoff / run_bakeoff_with_rerank → recall@k / nDCG@k / MRR per RetrievalMode (Fts/Semantic/Hybrid/Reranked). The real-vault run is #[ignore]d (run_bakeoff_over_real_db_from_env, MURMUR_BAKEOFF_DB/_DEK/_SET/_K/_OUT env). cargo test --lib proves the fusion + metric MATH and the gating purity; recall needs the real e5 model + Metal + a real PL/EN vault on a Mac. Report the delta against the committed synthetic baseline (rag-bakeoff-latest.md) AND the real vault; a synthetic number is not a real number. Runbook: references/rag-bakeoff-runbook.md.

Reference files (load on demand)

• references/hybrid-fusion.md — search_hybrid_visible + score_fuse mechanics, empty-leg redistribution, RRF fallback, the graph-noise + empty-FTS-leg gaps and candidate fixes.
• references/memory-and-consolidation.md — bitemporal reconcile_facts; consolidation scoring + fact_set_hash GC; the empty-unlock-set + purge-on-seal invariants.
• references/embeddings-and-reranking.md — the 384-dim vec0 lock + reindex mandate; e5 prefixes; swappable models; the reranker's stub-grade reality and the cross-encoder/ColBERT direction.
• references/rag-bakeoff-runbook.md — the real-vault MURMUR_BAKEOFF_* run; retrieval vs generation metrics; reporting the honest delta.