Systematic sweep of 8 IVF_PQ configs on 100K × 768d resumes. num_sub_vectors is the dominant lever: 48 → 192 pushes recall from 0.795 → 0.970. Winner: partitions=500, bits=8, subs=192. Build 61s (vs 18s baseline), acceptable for background builds. Hybrid status: HNSW recall=1.00 at <1ms, Lance IVF_PQ recall=0.97 at 60ms. Both backends production-grade. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>