[BUG] Session rename fails with ENOENT error: "no such file or directory, open 'n/a'"

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?

When attempting to rename a session, Claude Code throws an unhandled promise rejection error.

What Should Happen?

The session should be renamed without error.

Error Messages/Logs

Error: ENOENT: no such file or directory, open 'n/a'
      at openSync (unknown)
      at  (/$bunfs/root/claude:12:1277)
      at sW (/$bunfs/root/claude:11:8463)
      at appendFileSync (/$bunfs/root/claude:12:1200)
      at Dg_ (/$bunfs/root/claude:1049:3119)

  The error suggests the code is trying to write to a file path literally named `n/a` instead of a valid session file path.

Steps to Reproduce

1. Start a Claude Code session
2. Attempt to rename the session using the rename feature
3. Error is thrown immediately

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.0.75

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Cursor

Additional Information

_No response_