Bun

https://bun.com/blog/bun-joins-anthropic

Rewriting Bun in Rust - https://bun.com/blog/bun-in-rust - Via: https://simonwillison.net/2026/Jul/19/claude-code-in-bun-in-rust/

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. Boring is good.