# Claude Code uses Bun written in Rust now > Source: > Published: 2026-07-19 03:54:09+00:00 In [Rewriting Bun in Rust](https://bun.com/blog/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. Boring is good. I decided to have a poke at my own Claude Code installation to see if I could find evidence that it was using Bun written in Rust. I found these two commands convincing: ``` strings ~/.local/bin/claude | grep -m1 'Bun v1' ``` For me this outputs `Bun v1.4.0 (macOS arm64)` . The most recent release of [Bun on GitHub](https://github.com/oven-sh/bun/releases) is currently [v1.3.14](https://github.com/oven-sh/bun/releases/tag/bun-v1.3.14) from May 12th, so that v1.4.0 version number in Claude supports them shipping a preview of a not-yet-released Bun version. ``` strings ~/.local/bin/claude | grep -Eo 'src/[[:alnum:]_./-]+\.rs' ``` This outputs a list of [563 filenames](https://gist.github.com/simonw/c92fb0f67b114ac26e3b95a09ddccfdc), starting with these: ``` src/runtime/bake/dev_server/mod.rs src/runtime/bake/production.rs src/bundler/bundle_v2.rs ``` It looks like Bun in Rust is indeed being run in production across millions of different devices. Like Jarred said, "Boring is good". Tags: [bun](https://simonwillison.net/tags/bun), [rust](https://simonwillison.net/tags/rust), [anthropic](https://simonwillison.net/tags/anthropic), [claude-code](https://simonwillison.net/tags/claude-code), [jarred-sumner](https://simonwillison.net/tags/jarred-sumner)