[BUG] /fork fails with EEXIST - introduced in v2.1.20

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?

❯ /fork
  ⎿  Failed to fork conversation: EEXIST: file already exists, mkdir 'C:\Users\andrew.claude\projects\C--Users-andrew-foo'

I repro this on v2.1.56, as well as -50, -49, -20. It does NOT repro on v2.1.19 or the earlier ones I tried.

Related bug: 27791
but that one says it was introduced much later (v2.1.49).

What Should Happen?

/fork should create a forked session

Error Messages/Logs

❯ /fork
  ⎿  Failed to fork conversation: EEXIST: file already exists, mkdir 'C:\Users\andrew.claude\projects\C--Users-andrew-foo'

Steps to Reproduce

in a cc session, try to use the command "/fork"
I suspect this is specific to Windows.
Maybe also to installing cc using winget

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

v2.1.19

Claude Code Version

2.1.56 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_