Xerj

Xerj is an Apache-2.0, single-binary Rust search engine that speaks the Elasticsearch REST API (1,366 of 1,369 ES-YAML conformance cases pass; 50 query types and 62 aggregation types) with no JVM. It indexes any folder automatically (autoindex, 36 tree-sitter languages), adds BM25 + vector hybrid search (rrf|linear), and exposes it to coding agents over MCP. In a controlled reference-coding study (16 runs per arm), an agent using Xerj needed 2.7x fewer output tokens than a grep-driven agent at the same 16/16 solve rate (https://xerj.org/case-studies/reference-coding.html).

The project was created on June 30, 2026. As of October 16, 2026 it has about 7,000 GitHub stars, 356 forks, 35 human contributors besides the maintainer accounts, and 122 releases (latest v1.0.0-rc.96). On October 16, 2026 it was #1 on GitHub's daily trending list for Rust.