Microsoft agentically ports Copilot runtime to Rust for $120K
Microsoft successfully migrated the GitHub Copilot runtime from TypeScript to Rust using AI agents to perform the porting. The transition resulted in significant performance gains, including a 15.9x speedup and substantial memory efficiency improvements.
Why it matters
This demonstrates the practical utility of AI agents in large-scale software engineering and the performance benefits of memory-safe languages like Rust.
The Rust compiler remains unperturbed by the antics of the LLM
The software engine underpinning GitHub Copilot and a growing number of Microsoft products is now written entirely in Rust, with AI agents doing most of the porting work.
The migration cost about $120,000 in AI token usage plus about three weeks of a developer's time. However, managers also had to grapple with a few dozen regressions in the resulting code, pointing to AI’s ongoing challenges in understanding Rust.
The effort updated the runtime module-by-module until the job was completed, spanning over 135 releases across a 14.5-week time period. Roughly 1.3 port pull requests were opened per day.
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