[BUG] BUN_BE_BUN=1 does not work

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

With an environment variable BUN_BE_BUN=1, claude native binary cannot be used as bun since version 2.1.35.

What Should Happen?

Claude native binary behaves like bun with an environment variable BUN_BE_BUN=1.

https://bun.com/docs/bundler/executables#act-as-the-bun-cli

This is mentioned in bun's official reference and many skills rely on it to keep portabilility of scripts.

Error Messages/Logs

Steps to Reproduce

BUN_BE_BUN=1 claude version

• until 2.1.34: this shows bun version
• since 2.1.35: this shows claude version

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.34

Claude Code Version

2.1.38

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_