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fix(search): expose backend capabilities instead of ignoring lexical and hybrid modes #56
Description
Finding
The public search interface accepts lexical, hybrid, and weighting controls for Chroma and pgvector, but those backends ignore the requested mode/weight and perform dense-only search.
Revision: 41ec093a745f1c0277893dc8f758b96b216c970f.
Reproduced evidence
Insert a synthetic document, then request search_mode="lexical":
| Backend | Actual result |
|---|---|
| Embedded Chroma | one result, dense score ~0.4997, sparse score 0 |
| Live remote Chroma | one result, dense score ~0.4997, sparse score 0 |
| Direct PostgreSQL/pgvector | one result, dense score ~0.4990, sparse score 0 |
Semantic ingestion/retrieval worked for all three. This is a capability/contract mismatch, not a claim that semantic search is unavailable.
Code inspection confirms that Chroma.search() and PgVectorStore.search() accept these arguments but always embed the query and perform dense search.
Expected outcome
- Expose supported search capabilities for the active backend.
- Either implement the advertised modes/weighting or explicitly reject unsupported combinations.
- Gate/label UI controls and MCP/API behavior accordingly; do not describe dense retrieval as lexical/BM25.
- True lexical mode must not require a dense-embedding gateway call.
- Add backend-specific semantic/lexical/hybrid and weighting tests. Preserve Qdrant's existing hybrid behavior.
This can be resolved with honest capability handling without necessarily implementing BM25 in every backend.
Activity
spelech commentedon Oct 27, 2026
Triage & Implementation Brief
1. Scope & Effort
app/services/vector_store/,app/api/routers/search.py)2. Root Cause & Context
Chroma and pgvector backends accept
search_mode="lexical"andsearch_mode="hybrid", but always perform dense-only search (lexical mode embeds the query and runs dense search).3. Implementation Plan
supported_search_modesproperty on all vector store backends:["dense", "sparse", "hybrid"]["dense"]["dense"]app/api/routers/search.py, validate the requested mode against the active backend's capabilities:4. Acceptance Criteria
google-labs-jules commentedon Oct 27, 2026
Jules is on it. When finished, you will see another comment and be able to review a PR.
google-labs-jules commentedon Oct 27, 2026
Ready for a review! A PR has been created.
google-labs-jules commentedon Oct 27, 2026
I apologize, but I encountered an unexpected error and wasn't able to complete the task.