Copilot Runtime’s Shift From TypeScript to Rust
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Microsoft’s Copilot runtime reportedly moved entirely from TypeScript to Rust. The software layer supports GitHub Copilot and other Microsoft products, and AI was used in the port.
A module-by-module port over 14.5 weeks
According to The Register, Microsoft used Copilot and several large language models to port its Copilot runtime module by module. The effort reportedly took more than 135 releases over 14.5 weeks, cost about $120,000 in AI-token usage plus roughly three weeks of a developer’s time, and produced dozens of regressions that managers had to address.
The Copilot runtime was written in TypeScript, using Node.js and the V8 execution engine.
The Register reports that the runtime is now entirely written in Rust after AI agents converted 430,000 lines of TypeScript into 800,000 lines of production Rust.
The reported rewrite concerns a runtime used by the GitHub Copilot CLI, Copilot app, SDK, cloud agent, and integrations including VS Code, Visual Studio, Excel, Outlook, and PowerPoint. On one reported benchmark, the Rust implementation completed 120 one-turn session lifecycles per second versus 7.55 for the earlier TypeScript version; memory use for a 10-client batch was reported as 126 MB rather than 1,383 MB.
Sources
- The RegisterMicrosoft agentically ports Copilot runtime to Rust for $120KRead source →