[BUG] Console window hangs when claude is running more than one subagent

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 I'm using claude code, whenever claude launches more than one subagent at a time the responsiveness of the console window drops significantly. For example, if one agent needs a permission, there can be a multi-second delay between a keypress and seeing a result inside the console window. Sometimes I also notice flickering artifacts as well.

What Should Happen?

I'd expect the amount of subagents running in a single instance to have minimal impact on the main thread execution of the console window.

Error Messages/Logs

Steps to Reproduce

Direct claude to investigate a large project folder, direct to use multiple subagents.

Notice that while the subagents are running, the responsiveness of the terminal window is reduced.

Claude Model

Other

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.0.55

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_