# Microsoft ports Copilot runtime to Rust using AI agents at $120K cost

Digest AI · Agents & Tools · published 2026-09-20T09:08:52Z

Canonical: https://digestai.news/story/microsoft-ports-copilot-runtime-to-rust-using-ai-agents-at-120k-cost

## Summary

Microsoft rewrote the Copilot runtime, which powers GitHub Copilot across VS Code, Office apps and other services, from TypeScript to Rust using AI agents. The migration consumed about $120,000 in AI token usage and roughly three weeks of a developer’s time, spanning 135 releases over a 14.5‑week period with an average of 1.3 port pull requests per day. Agents transformed 430,000 lines of TypeScript into 800,000 lines of production Rust.

A benchmark of 1,000 one‑turn session lifecycles showed the Rust version completing 120 lifecycles per second versus 7.55 for the original TypeScript implementation, a 15.9x speedup, while memory usage fell from 1,383 MB to 126 MB. Stephen Toub, a Microsoft Distinguished Engineer, noted that the agents spent much of the effort gathering information and coordinating across sessions, and highlighted regressions that required human oversight despite successful compilation.

## Key points

- Port cost $120,000 in AI token usage plus about three weeks of developer time.
- Agents rewrote 430,000 TypeScript lines into 800,000 Rust lines across 135 releases in 14.5 weeks.
- Benchmark showed Rust runtime handling 120 lifecycles per second versus 7.55 for TypeScript, a 15.9x speedup.

## Why it matters

The rewrite demonstrates that AI agents can automate large‑scale code migrations, delivering major performance and memory gains while costing a fraction of manual effort, signaling a new efficiency path for enterprise software development.

## Sources

1. [Microsoft agentically ports Copilot runtime to Rust for $120K](https://theregister.com/devops/2026/09/18/microsoft-agentically-ports-copilot-runtime-to-rust-for-120k/5297549) (theregister.com, 2026-09-20)

## Cite

Digest AI, "Microsoft ports Copilot runtime to Rust using AI agents at $120K cost", 20 September 2026, https://digestai.news/story/microsoft-ports-copilot-runtime-to-rust-using-ai-agents-at-120k-cost

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