Microsoft agentically ports Copilot runtime to Rust for $120K
Summary
The Register reports that Microsoft has ported the GitHub Copilot runtime from TypeScript/Node to Rust, using AI agents to automate much of the porting work. The migration cost around $120k in AI token usage and 14.5 weeks of effort, with about 430k lines converted to 800k lines of Rust and a dramatic performance improvement in a specific workload, though dozens of regressions were observed. The piece also discusses broader themes about using agents and compilers in software development, including the caution that compilers are teachers, not oracle, and the emergent behaviors of agentic workflows.