Lens is basically a rust local first mmapped file base search store, it combines RAPTOR with LSP, semantic vectors and a dual dense/sparse encoding, and can learn a function over those to tune the weights of the relevance sources adaptively per query using your data. It also uses linear programming to select an "efficient" set of results that minimizes mutual information between result atoms -- regular rag/rerank pipelines just dump the top K, but those often have a significant amount of overlap so you bloat context for no benefit.