[BUG] VERY Slow and unresponsive UI when CPU usage is high

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?

Claude Code UI becomes unresponsive and laggy, when the CPU usage is high. Also, when context is getting low, I also notice a laggy input consumption and missing chars.

Its impossible to work like that. Several seconds until a key-press is registered and showed. It accounts to typing but also to moving the cursor or right click paste: Characters are being swallowed, right-click paste is not registered at all. Its so SLOW!!!!! I cant stop the processes using the CPU to free up some cycles.

When the CPU is low in usage, typing is also not how I am used to it. The version 1.0.107 of CC I used before updating to the latest, did not show such slowliness.

How can I help to pinpoint the problem's cause?
My System: Win10, Windows Terminal.

• I did not try win10's command prompt (cmd), though.

greets,
Tony

What Should Happen?

Claude Code should not swallow characters I type, or other events. If it can't display it at the time of typing, then it should buffer and flush the buffer the next time possible.

Error Messages/Logs

- no logs

Steps to Reproduce

Run something that accounts for 80-90% CPU usage, start CC in windows terminal and try to type some prompts. This is absolutely reproducible on my system.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.7

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_