Experimental Results from a Self-Improving Retrieval System for Conversational Memory

The biology-inspired mutation layer didn't work. A learned MLP adapter and segmentation mutation both produced ~zero NDCG lift on LongMemEval. The control loop was sound; the perturbations weren't load-bearing. A recall diagnostic reframed the project: 78% of relevant entries never reached the cross-encoder. Bi-encoder recall was the ceiling, not the mutation layer. Standard IR wins compounded: 0.95-cosine dedup plus BM25 alongside vector plus cross-encoder rerank took NDCG@10 from 0.22 to 0.3...