Elasticsearch changes the default for minimum_should_match according to the other clauses in the same bool. A should-only query requires one match, but should becomes optional when must or filter is present. The Elasticsearch bool query reference documents the defaults as one and zero respectively.

The gateway used to reject the common required-plus-optional shape unless the client explicitly sent minimum_should_match. Its gateway-side source evaluator also required one should match, which could incorrectly remove hits from post_filter, filter aggregations, and approximate lexical scans.

The default is now resolved once and shared by both the Qdrant filter translator and the source evaluator. This regression covers a document that matches filter.brand = Acme but not should.featured = true: it remains a hit when the minimum is omitted and is excluded when the client explicitly requests one match. A second regression covers the same boundary in the approximate text evaluator.

Run the focused checks without Qdrant:

cargo test bool_should

This aligns hit selection, not scoring. Elasticsearch uses optional query-context clauses to boost relevant documents. Filter-only optional clauses are omitted from the Qdrant filter when their effective minimum is zero, so they do not change Qdrant scores. Clients that require a should clause to affect eligibility should continue to send an explicit minimum_should_match.