[BUG] CRITICAL: Multiple Instances of Claude Code now prevent each other from working

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?

For some reason in 2.0.61, if I load two Claude code instances, they can no longer operate in parallel. Now when one runs, the other one stops and no more messages can be received by the other instance. This is a huge regression.

What Should Happen?

Multiple instances of cluade code should be able to run in parallel without interfering with each other

Error Messages/Logs

None

Steps to Reproduce

1. Open two instances of claude code.
2. Send a prompt in to one
3. Wati until its running
4. Send a prompt into the other instnace
5. Watch as the first instance halts and cannot proceed.
6. Observe the new messages to the first instance will not go through

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.0.50

Claude Code Version

2.0.61

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

This is a HUGE issue, please look to fix immediately. I like to be able to run multiple instances in parallel for my workflow