[BUG] Cannot reliably `/fork` a forked conversation

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?

I forked a conversation.
worked on the two branches of the conversation separately

After that if I /fork the already forked conversation and run the claude --resume command that it gives me, it does not resume from the point where I did this last /fork but rather from the original /fork that I did

What Should Happen?

ideally the claude --resume command should start from where I made the new /fork

Error Messages/Logs

Steps to Reproduce

1. start claude and send some messages.
2. Run /fork to create a fork of the conversation.
3. run the claude --resume command that you get and work separately on the two sessions you now have
4. From that newly formed claude session, run /fork again.
5. Execute the claude --resume command provided after the second fork.
6. Observe that the session resumes from somewhere else (sometimes the original /fork point, sometimes a different session entirely)

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.59

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_