GitHub rewrote the Copilot agent runtime in Rust with Copilot agents
GitHub migrated the Copilot agent runtime from a TypeScript/Node.js/V8 implementation to over 800,000 lines of production Rust. Most of the Rust code was authored by AI agents via the GitHub Copilot app and CLI across 128 pull requests; the migration shipped incrementally, reportedly improving runtime performance by orders of magnitude and reducing startup and memory overhead for many Microsoft/GitHub products that share the runtime via the Copilot SDK.