Microsoft agentically ports Copilot runtime to Rust for $120K

Commenters debated Microsoft’s agent-driven port of the Copilot runtime from TypeScript to Rust, with several people highlighting the scale and performance claims. meerita relayed Andrea’s figures that production Rust totaled about 832,378 lines with another ~469,000 test lines, and that a lifecycle benchmark went from 7.55/sec in TypeScript to 120/sec in Rust (a 15.9x speedup). Some welcomed the speed and said the project makes Rust more appealing (jdw64), while hollowturtle argued that hand-optimizing the JavaScript might have closed much of the gap and that making the Rust idiomatic would demand far more effort, potentially shifting the bottleneck elsewhere.

Much of the discussion focused on process and code quality. Several commenters accused the work of “vibecoding” or LLM-driven stitching that produces bloated or poorly organized code (Rexxar, formerly_proven, applfanboysbgon), with dmix joking that extra lines were agent-added comments. Others defended large files as sometimes normal in legacy or complex projects (Rexxar, perching_aix, dgellow), while critics insisted huge monoliths hurt maintainability and should be split (sajithdilshan). Peripheral concerns included recent VS/Explorer glitches and offhand wishes for a GIL-free Python port (amelius).