Microsoft Agentically Ports Copilot Runtime to Rust for $120K
The Register, Friday, September 18th, 2026
Agents converted 430,000 lines of TypeScript into 800,000 lines of Rust for $120K in tokens plus three weeks of developer time.
The runtime behind GitHub Copilot is now entirely Rust, with AI agents doing most of the porting.
The migration cost roughly $120,000 in token usage plus about three weeks of a developer's time, spanning 135 releases over 14.5 weeks at roughly 1.3 port pull requests per day, though managers had to handle a few dozen regressions that pointed to continuing agent difficulty with Rust.
The team replaced TypeScript modules case by case without restructuring the runtime, leaving optimization for later.
On a benchmark of 1,000 one-turn session lifecycles with 100 concurrent pipelines, TypeScript managed 7.55 per second against 120 per second for in-process Rust, a 15.9x speedup, and a 10-client agent batch dropped from 1,383 MB to 126 MB.