GitHub Migrates Copilot Runtime to Rust with AI-Assisted Rewrite

GitHub has migrated the runtime behind Copilot CLI, the Copilot app, and Copilot SDK from TypeScript and Node.js to Rust, replacing over 800,000 lines of production code in about 14.5 weeks and 128 pull requests. Client startup and session creation dropped from 5.25 seconds to 292 ms, and the runtime can now be embedded via a C ABI.

• Migration took about 14.5 weeks and 128 pull requests
• Client startup dropped from 5.25 seconds to 292 ms
• Rust runtime embeds via C ABI instead of Node.js and V8
• By August the runtime held 832,378 lines of Rust code