[BUG] Persistent UI rendering glitches during chat output and text editing

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?

There is a persistent rendering issue in the Claude Code interface when running on Windows Terminal. The UI fails to render text correctly, resulting in garbled output, overlapping text, and visual artifacts.

This glitch occurs not only when editing input (typing "/" and using backspace) but also actively during the chat rendering process when Claude generates responses. The /clear command is also unable to properly wipe the screen or fix these artifacts.

What Should Happen?

The terminal should render text cleanly without visual corruption, both during chat streaming and user input. The screen should update correctly, and the /clear command should wipe all previous content, restoring a clean prompt.

Error Messages/Logs

Steps to Reproduce

Scenario A (Chat Rendering):
Initiate a conversation or run a command that triggers a long response from Claude.
Watch the terminal as Claude renders the text stream.
Observe that the display becomes corrupted or fails to refresh cleanly, leaving glitched artifacts.

<img width="1262" height="642" alt="Image" src="https://github.com/user-attachments/assets/3af59611-cb2d-426b-a0f5-8b0ed1bfa255" />

Scenario B (Text Input):
Type the "/" character to open the command menu.
Press Backspace repeatedly to delete the character.
Observe the visual corruption on the current line.

<img width="1262" height="642" alt="Image" src="https://github.com/user-attachments/assets/51fe5e57-103d-42da-8853-1c38ac2a3ec6" />

Scenario C (Clear Command):
When the screen is in a glitched state, type /clear.
Observe that the terminal does not clear completely.

<img width="1262" height="642" alt="Image" src="https://github.com/user-attachments/assets/3a3c3935-f679-4945-9d2a-b67514a4bfda" />

Claude Model

Other

Is this a regression?

Yes, this worked in a previous version

Last Working Version

npm version

Claude Code Version

v2.1.19

Platform

Other

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_