Claude Code uses Bun written in Rust for its Rust-based Bun port; Claude Code v2.1.181 and later reportedly rely on Bun Rust port
Read the original at simonwillison.net→In Rewriting Bun in Rust Jarred Sumner made the following claim: Claude Code v2.1.181 (released June 17th) and later use the Rust port of Bun. Startup got 10% faster on Linux but otherwise, barely anyone noticed....
Original headline: "Claude Code uses Bun written in Rust now"