Bun Rewritten in Rust Appears to Already Be in Production in the Claude Code App

Simon Willison said he found evidence that Claude Code v2.1.181 includes an unpublished Rust-based Bun.

Searches surfaced Bun v1.4.0 references and Rust file traces, and Jarred Sumner's response further suggested it had been adopted.

The case highlights how AI agents can help port large software projects quickly and get them running in real product environments.