[BUG] Chat Header UI Issue

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?

Bug Report: Chat Header UI Issue
Environment:

OS: Windows
Product: Claude Code

Description:
Chat header continuously expands and contracts during normal usage, causing disruptive page behavior.
Steps to Reproduce:

Open Claude Code interface
Scroll through chat content
Attempt to copy/paste text from conversation

Expected Behavior:
Header should remain stable during scrolling and text selection operations.
Actual Behavior:

Header repeatedly expands/contracts automatically
Page jumps to top during scrolling
Page jumps to top when copying content
Header occasionally gets stuck in expanded state
Content in middle of conversation becomes inaccessible
Copy/paste operations are severely impacted

Impact:
Makes it extremely difficult to review conversation history and copy code/text snippets.

What Should Happen?

Header should remain stable during scrolling and text selection operations.

Error Messages/Logs

Steps to Reproduce

Steps to Reproduce:

Open Claude Code interface
Scroll through chat content
Attempt to copy/paste text from conversation

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

v2.1.19

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

<img width="605" height="88" alt="Image" src="https://github.com/user-attachments/assets/ecf78255-6d18-453a-8619-2200dd6d881f" />

<img width="1112" height="252" alt="Image" src="https://github.com/user-attachments/assets/a232802c-cdf7-4322-9bde-d0c58c7887f6" />