bm25-rerank

Stateless BM25 reranker over a candidate set. Pair with dense retrieval to recover keyword matches an embedding might miss.

use bm25_rerank::rerank;
let docs = [
    "the quick brown fox",
    "a brown dog sleeps",
    "lazy fox jumps over",
];
let order = rerank("fox", &docs, Default::default());
// docs ordered by BM25 score, descending

Lucene-style IDF + smoothing. Zero deps. MIT or Apache-2.0.