[BUG] Long responses show repeated text chunks in scrollback on Windows 11 (PowerShell)

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 Claude Code produces a long response, sections of the response text appear duplicated in the scrollback buffer. Scrolling back up through the output reveals the same content block (headings, bullet lists, paragraphs) repeated multiple times. The duplication is not present while the response is streaming - it only becomes visible when scrolling back. I did not resize or move the terminal.

I opened a new terminal, asked a question that had a long answer, and got duplicated text. I attached the full output - you can see the "Mid-Season Fairness" header was printed 4 times.
claude code duplicate output.txt

What Should Happen?

Scrolling should not duplicate output - each section of the response appears exactly once in scrollback.

Error Messages/Logs

Steps to Reproduce

1. Ask a question that produces a long multi-section response (markdown with headers, tables, and lists)
2. Wait for the response to finish streaming
3. Scroll back up through the output (potentially repeatedly)

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.133

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Potentially related issues:

• #52020
• #49086
• #56718