BM25 vs vector vs RRF hybrid on 85 chunks — vector MRR won (hybrid did not “always win”)

Canonical: Hybrid BM25 + vector precision on eWorld.liveCheck date: 2026-09-26 PT · API spend $0 (CPU) Self-built 85-chunk Northline Hybrid Lab + 15 graded queries (5 keyword / 5 semantic / 5 mixed).