[BUG] Using backspace to clear a long prompt causes the UI to become unresponsive

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?

After pasting in a multi line prompt, if i use backspace to try and clear it out, the UI becomes unresponsive and never recovers.

What Should Happen?

UI not crash while deleting a prompt

Error Messages/Logs

None

Steps to Reproduce

Paste in a multiline prompt.
Hold down backspace to delete the prompt.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.17

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Xterm

Additional Information

_No response_