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AIQuiet 5d · day 8

Microsoft's AI agents rewrite the GitHub Copilot runtime in Rust for $120K

A 430,000-line TypeScript codebase became 800,000 lines of Rust over 14.5 weeks, mostly done by AI coding agents.

newest coverage 5d agosummary written 6d ago21 pieces50 likes & upvotes65 comments NewswiresRedditHacker NewsMastodon

What to know

  • Microsoft used AI agents to convert the Copilot runtime from 430,000 lines of TypeScript to 800,000 lines of Rust in 14.5 weeks for about $120,000 in token costs.
  • Benchmarks cited by Microsoft show a 15.9x throughput speedup and roughly 11x lower memory use in the Rust version.
  • The project required human oversight to fix a few dozen regressions, and Microsoft says the structural optimization of the runtime is still to come.
  • Online commenters have questioned whether the reported token-cost figure is realistic given estimated compute costs for a project of this scale.

“The popular image of AI spewing code is almost backwards; at this scale, the work looked much more like iterative investigation, inspecting the current state, forming a hypothesis, making a targeted change, rinsing and repeating.”

Stephen Toub, Microsoft Distinguished Engineer · The Register ↗ · Sep 17

Stephen Toub Microsoft Distinguished EngineerMicrosoft Company behind GitHub CopilotGitHub Copilot Product/runtime being ported

Microsoft's AI agents rewrite the GitHub Copilot runtime in Rust for $120K
theregister.com

How it unfolded 1 development · click the chart to see its coverage articlespostscomments

Peak 10 pieces in two hours at Sep 20, 6 AM; 21 pieces over 8 days (2 articles · 4 posts · 15 comments) Sep 18, 4 PM — 1 piece · 1 article — Newswires 1Sep 18, 6 PM — 1 piece · 1 post — Reddit 1Sep 18, 8 PM — quietSep 18, 10 PM — 1 piece · 1 comment — Reddit 1Sep 19, 12 AM — 1 piece · 1 post — Hacker News 1Sep 19, 2 AM — quietSep 19, 4 AM — 1 piece · 1 comment — Reddit 1Sep 19, 6 AM — quietSep 19, 8 AM — quietSep 19, 10 AM — quietSep 19, 12 PM — quietSep 19, 2 PM — quietSep 19, 4 PM — quietSep 19, 6 PM — quietSep 19, 8 PM — quietSep 19, 10 PM — quietSep 20, 12 AM — quietSep 20, 2 AM — quietSep 20, 4 AM — 2 pieces · 1 article · 1 post — Hacker News 1, Newswires 1Sep 20, 6 AM — 10 pieces · 10 comments — Hacker News 10Sep 20, 8 AM — 2 pieces · 2 comments — Hacker News 2Sep 20, 10 AM — quietSep 20, 12 PM — 1 piece · 1 comment — Hacker News 1Sep 20, 2 PM — quietSep 20, 4 PM — quietSep 20, 6 PM — quietSep 20, 8 PM — quietSep 20, 10 PM — quietSep 21, 12 AM — quietSep 21, 2 AM — quietSep 21, 4 AM — quietSep 21, 6 AM — quietSep 21, 8 AM — quietSep 21, 10 AM — 1 piece · 1 post — Mastodon 1Sep 21, 12 PM — quietSep 21, 2 PM — quietSep 21, 4 PM — quietSep 21, 6 PM — quietSep 21, 8 PM — quietSep 21, 10 PM — quietSep 22, 12 AM — quietSep 22, 2 AM — quietSep 22, 4 AM — quietSep 22, 6 AM — quietSep 22, 8 AM — quietSep 22, 10 AM — quietSep 22, 12 PM — quietSep 22, 2 PM — quietSep 22, 4 PM — quietSep 22, 6 PM — quietSep 22, 8 PM — quietSep 22, 10 PM — quietSep 23, 12 AM — quietSep 23, 2 AM — quietSep 23, 4 AM — quietSep 23, 6 AM — quietSep 23, 8 AM — quietSep 23, 10 AM — quietSep 23, 12 PM — quietSep 23, 2 PM — quietSep 23, 4 PM — quietSep 23, 6 PM — quietSep 23, 8 PM — quietSep 23, 10 PM — quietSep 24, 12 AM — quietSep 24, 2 AM — quietSep 24, 4 AM — quietSep 24, 6 AM — quietSep 24, 8 AM — quietSep 24, 10 AM — quietSep 24, 12 PM — quietSep 24, 2 PM — quietSep 24, 4 PM — quietSep 24, 6 PM — quietSep 24, 8 PM — quietSep 24, 10 PM — quietYesterday, 12 AM — quietYesterday, 2 AM — quietYesterday, 4 AM — quietYesterday, 6 AM — quietYesterday, 8 AM — quietYesterday, 10 AM — quietYesterday, 12 PM — quietYesterday, 2 PM — quietYesterday, 4 PM — quietYesterday, 6 PM — quietYesterday, 8 PM — quietYesterday, 10 PM — quietToday, 12 AM — quietToday, 2 AM — quietToday, 4 AM — quietToday, 6 AM — quietToday, 8 AM — quietToday, 10 AM — quietToday, 12 PM — quiet 1
Sep 19Sep 20Sep 21Sep 22Sep 23Sep 24yesterdaynow · 1:19 PM ET
  1. 1

    Commenters question feasibility of the $120K token-cost figure

    On Reddit, a commenter estimates the compute costs implied by an Opus-class model on a 400,000-line-scale project would require roughly 60 billion tokens, questioning whether the reported $120,000 figure is consistent with known hardware and operational cost estimates.

    “Hardware mortization for an Opus class model is around 1$ per mil tokens alone, then you get operational costs in the same range... they would allegedly spend around 60b tokens on that project? Would be a bit rough for a 400kloc project…”
    — Minimonium

    • Oh boy. No. > Linux, and Unix, and iOS (which is lLinux under the hood) are substantially harder to install on diverse hardware. Just so you know, none of Apple’s operating system have ever been based on Linux, ever, in the entire history of the company. The kernel, XNU, is based on Mach and FreeBSD. > The *nix distros can’t even agree on a single…

      gplusplus314r/technology7d agoview on r/technology ↗
    2 more of the top 3 · 16 posts in this stretch

    • > The original TypeScript implementation completed 7.55 of those lifecycles per second, while Rust running in-process managed 120 per second - representing a 15.9x speedup on that particular workload.Does this impresses/surprises anyone? Two folds: 1) I believe the most optimized JavaScript code could near the performance of this phase 1 port…

      hollowturtleHacker News6d agoview on Hacker News ↗
    • Viss@mastodon.social

      good news for everyone running copilot for any reason: https://www. theregister.com/devops/2026/09 /18/microsoft-agentically-ports-copilot-runtime-to-rust-for-120k/5297549 it's vibecoded now so you can abandon it guilt free

      Viss@mastodon.socialMastodon5d agoview on Mastodon ↗
    all of them →
  2. background

    Benchmarks show 15.9x speedup and lower memory use in Rust — A benchmark of 1,000 one-turn session lifecycles found the Rust runtime completed 120 per second versus 7.55 for TypeScript, and a 10-client agent batch used 126 MB in Rust versus 1,383 MB in TypeScript, though managers had to fix a few dozen regressions introduced by the AI-driven port.

  3. background

    Microsoft details AI-driven Rust port of Copilot runtime — Microsoft Distinguished Engineer Stephen Toub publishes an account of using AI agents to convert 430,000 lines of TypeScript into 800,000 lines of production Rust for the runtime underlying GitHub Copilot, VS Code, Visual Studio, Excel, Outlook and other products; The Register reports the migration cost about $120,000 in token usage and three weeks of developer time across 135+ releases over 14.5 weeks.

Also covered reported alongside — the timeline has no entry for these yet

  1. 2 outlets Microsoft agentically ports Copilot runtime to Rust for $120K

    first by HN Frontpage, 6d ago · also The Register

What people are saying 11 voices from 1 site · best of 16 · verbatim