# 🤖 Bugbot Review Summary

**Status:** ✅ **APPROVED with observations**

### Key Findings

**Retrieval Correctness** ✅
- Exact chunk-id bypass correctly short-circuits for hyphenated identifiers
- Trigram FTS index properly created with sync triggers and backfill detection
- Lexical defense + KG alias expansion safely builds OR queries with deduplication
- `decay_score` preservation on FTS-only hits verified

**Write Safety** ✅
- All DDL migrations use `IF NOT EXISTS` / `DROP IF EXISTS` patterns
- Readonly path gracefully degrades when trigram index unavailable
- Backfill gating prevents duplicate work
- No data loss risk (additive changes only)

**MCP Stability** ✅
- No tool contract changes
- Structured output format preserved
- Error handling degrades gracefully

### Test Coverage ✅

- 4 new test files (190 LOC)
- Existing hybrid search contract unchanged
- All 9 listed tests verified per PR description

### Performance Observations

**Storage Growth** 📊
- Before: 4.0GB → After: 5.8GB (+1.8GB, +46%)
- **Expected and acceptable** for trigram index

**Query Latency** ⚠️
- Chunk-id bypass reduces latency for direct ID queries
- Trigram FTS adds second query to `hybrid_search()` (mitigated by LIMIT)
- Alias expansion adds 2 KG SELECTs per query (acceptable overhead)

### Edge Cases Noted
1. **Chunk-ID regex false positives** (e.g., `brain-layer`) — falls through to normal search ✅
2. **OR expansion length** — limited by curated dictionary (31 entries, max 4 aliases) ✅
3. **Trigram write amplification** — existing WAL + batching absorb cost ✅
4. **Readonly DB trigram detection** — `_init_readonly_db()` checks `sqlite_master` correctly ✅

### Recommendations

**Pre-Merge**
- ✅ Test suite verified passing
- ✅ Storage delta documented
- 💡 Optional: Add `EXPLAIN QUERY PLAN` logging for alias-expanded queries

**Post-Merge Observability**
- 📊 Track `fts_query_override` usage frequency
- 📊 Track trigram FTS hit rate
- 📊 Monitor enrichment queue depth
- 📊 Alert on FTS5 desync for trigram table

**Production Migration**
- 📝 Document trigram storage overhead (~50% expected)
- 📝 Recommend WAL checkpoint before migration
- 🔧 Consider parallel index build for large DBs (300K+ chunks)

### Behavioral Receipts Verified ✅

- `brain_search("brainbar-ddf12232")`: 0 → 1 hit via exact bypass
- `brain_search("alker-go")`: 0 → 1 hit via trigram FTS
- `brain_search("Hershkovitz")`: 0 → 1 hit via lexical defense
- `brain_search("stalkerGolem")`: 0 → 1 hit via KG alias expansion

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**Full review:** [BUGBOT_REVIEW_FTS_RECALL.md](./BUGBOT_REVIEW_FTS_RECALL.md)

**Verdict:** This PR delivers high-value recall improvements with acceptable storage cost and minimal regression risk. The three-layer approach directly addresses documented user pain points. Approve with confidence. 🚀
