[BUG] Cursor becomes ANSI escape codes when moving around 'Ultrathink'

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 move my cursor in the 'Ultrathink' word, my cursor becomes ANSI escape codes like the image shows:

<img width="692" height="105" alt="Image" src="https://github.com/user-attachments/assets/c2c7bac1-66b2-43c7-9778-da94f2957548" />

(In the image, my cursor is on the position between 't' and 'r')

What Should Happen?

I expect my cursor is in the normal state.

Error Messages/Logs

N/A

Steps to Reproduce

1. open claude code in terminal
2. type "ultrathink" and then move cursor around this word.

Claude Model

Sonnet (default)

Is this a regression?

Seems working in v1.0.120.

Last Working Version

_No response_

Claude Code Version

1.0.128

Platform

AWS Bedrock

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_