# Decisions: rag-hybrid-search-rrf

## Capability

sm-flow + OpenSpec fallback; apply pre-authorized.

## Depends

Delivery 1 archived.

## Grill (compressed, pre-authorized)

- Q: Full BM25 schema now? A: No — sparse-lite + RRF first; schema rebuild follow-up.
- Q: Default mode? A: dense default; hybrid opt-in.
- Q: Threshold score? A: keep dense-compatible L2 mapping.

## Design

Hybrid paths: dense unfiltered + dense filtered + lexical rank over union; RRF fuse by evidenceKey.