Windows: chat fails with "UNC paths are not supported. Defaulting to Windows directory." when using WSL paths

[MansGullberg]

Summary

On Windows, chat fails when the app is used with WSL-based paths. I get:

UNC paths are not supported. Defaulting to Windows directory.

This appears to be caused by the app or one of its spawned processes using a UNC WSL path such as:

\\wsl.localhost\Ubuntu\home\<user>\...

instead of a normal Windows drive path.

Environment

• App: T3 Code for Windows
• Version: v0.0.9
• OS: Windows 11
• WSL: Ubuntu
• Repo/files located in WSL, for example:
  • \\wsl.localhost\Ubuntu\home\<user>\...

What I expected

Chat should work when the project or Codex-related files are in WSL, or the app should convert the WSL path to a supported working directory before spawning the shell/process.

What actually happens

The app shows:

UNC paths are not supported. Defaulting to Windows directory.

After that, chat/session behavior breaks because the process is no longer running in the intended project directory.

Reproduction

1. Open T3 Code on Windows.
2. Use a project that lives in WSL, or otherwise make the app work against a WSL UNC path like:
   • \\wsl.localhost\Ubuntu\home\<user>\project
3. Start a chat/session.
4. The app throws:
   • UNC paths are not supported. Defaulting to Windows directory.

Notes

I also tried moving CODEX_HOME to a normal Windows path (C:\Users\<user>\.codex) so it would not point into WSL anymore.

That did not resolve the problem, which suggests the failing UNC path is likely the workspace/current working directory or another path the app passes into the spawned shell, not just CODEX_HOME.

Possible root cause

This looks like a Windows cmd.exe / process-launch limitation with UNC working directories. If the app starts a shell/process with a current directory like \\wsl.localhost\..., Windows falls back to C:\Windows instead.

Suggested fix

• Detect WSL UNC paths before launching the chat process.
• Avoid launching Windows shell commands with a UNC current working directory.
• Either:
  • support WSL execution directly, or
  • translate/mount the path to a drive-letter path before launch, or
  • show a clear error that WSL paths are not currently supported.

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This issue report was generated by GPT-5.4 on High running in the Codex app on Windows in a WSL environment.