Copilot · Oracle · Microsoft · Rust · The Register
Microsoft agentically ports Copilot runtime to Rust for $120K
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The Rust compiler remains unperturbed by the antics of the LLM.
Key facts
- In terms of memory, a 10-client batch of agents consumed 1,383 MB with TypeScript while the Rust rewrite consumed only 126 MB serving the same swarm
- The project used Copilot to rewrite Copilot, which in turn used several LLMs, GPT-5.6 Sol and Claude Opus 4.8 were both namechecked, to execute different parts of the job, depending on each LLM’s
- The porting session, which ended up taking 25 hours to complete, began by spending 56 minutes reading the documentation and making 122 tool calls for clarification
- The migration cost about $120,000 in AI token usage plus about three weeks of a developer's time
Summary
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. The effort updated the runtime module-by-module until the job was completed, spanning over 135 releases across a 14.5-week time period. Overall, agents converted 430,000 lines of TypeScript into 800,000 lines of production Rust. And Rust, known for its lean performance, did not disappoint.