Claude Code Shifts to Bun Built with Rust

Simon Willison reported that Claude Code has transitioned to the Bun runtime. Bun is a JavaScript engine that is implemented in the Rust programming language. The change aims to improve performance and reliability for the code generation tool. Rust’s memory safety features are expected to reduce runtime errors. Developers can now leverage Bun’s fast startup and low overhead. The update reflects a broader trend toward Rust-based infrastructure in AI tooling. Early benchmarks suggest noticeable speed gains over previous setups. Users are encouraged to test the new environment and provide feedback.