From what I've heard there are two main use cases:

- People use bun as an all-in-one frontend web bundler. Personally, I just use esbuild (and webpack, if I'm working on a system using its module federation, like Jupyterlab). My understanding is bun has a machine-translated port of esbuild (ported to Zig, then to Rust) built into it.

- Claude Code runs on bun.

The second point has to be why Anthropic acquired them.

It famously is extremely memory leaky, with the core team having no idea how to fix it. With the new AI-automated unsafe Rust migration, this piece of slop may never actually become production-ready.

I run it in production for multiple systems.

Ready to migrate back to node once the slop version is out.