[BUG] ENOEXEC error when running Claude Code on WSL2 (Bun v1.3.13 regression)

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?

Root Cause

Bun v1.3.13 introduced a regression where it tries to call reg.exe (Windows registry tool) via posix_spawn from within WSL2. Since /mnt/c/Windows/System32/reg.exe is a Windows PE executable, the Linux kernel cannot execute it and returns ENOEXEC.

What Should Happen?

Claude should open the TUI

Error Messages/Logs

## Error


662 |     var file = this.spawnfile = options.file, spawnargs;
663 |     if (options.args === @undefined)
664 |       spawnargs = this.spawnargs = [];
665 |     else
666 |       validateArray(options.args, "options.args"), spawnargs = this.spawnargs = options.args;
667 |       if (this.#handle = Bun.spawn({
             ^
ENOEXEC: unknown error, posix_spawn '/mnt/c/Windows/System32/reg.exe'
    path: "/mnt/c/Windows/System32/reg.exe",
 syscall: "posix_spawn",
   errno: -8,
    code: "ENOEXEC"

      at spawn (node:child_process:667:35)
      at spawn (node:child_process:14:39)
      at execFile (node:child_process:59:20)
      at <anonymous> (/$bunfs/root/src/entrypoints/cli.js:188:1452)

Bun v1.3.13 (Linux x64 baseline)

Steps to Reproduce

Steps to Reproduce

1. Install Bun v1.3.13 on WSL2
2. Install Claude Code via npm install -g @anthropic-ai/claude-code
3. Run claude — crashes immediately with the error above

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.118

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information

Workarounds attempted:
Global Bun Downgrade: Failed (Claude uses its own bundled v1.3.13).

PATH Mocking: Failed (The binary seems to call the absolute path /mnt/c/Windows/System32/reg.exe).

WSL Interop manual fix: echo ':WSLInterop:M::MZ::/init:PF' | sudo tee /proc/sys/fs/binfmt_misc/register (Only works if the kernel allows re-registration).

Recommended Fix for Users:
The only reliable way to bypass this until a new version is released with Bun v1.3.14+ is to force the use of a version that doesn't include the faulty runtime or use npx with an older tag:

Bash
Install a previous stable version that uses a different Bun/Node runtime
npm install -g @anthropic-ai/claude-code@0.2.23

All workaounds and Fixes were recommended and implemented by Gemini as at the moment Claude was dead :)