[BUG] Korean text gets corrupted when copying (via /copy or selection) with new renderer enabled

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 the new renderer is enabled via CLAUDE_CODE_NO_FLICKER=1, copying text results in corrupted Korean characters.

This happens both when using the /copy command and when manually selecting text (drag + copy).

English text is copied correctly, but Korean text becomes garbled after being pasted.

What Should Happen?

Korean text should be copied correctly without corruption.

Error Messages/Logs

Steps to Reproduce

1. Set environment variable:

``
CLAUDE_CODE_NO_FLICKER=1
``

1. Launch Claude Code in PowerShell
2. Generate a response containing Korean text
3. Copy the text using either:

• /copy
• mouse selection (drag) + copy

1. Paste into another application

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.90

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

• Issue does not occur with English text
• Issue occurs with both /copy and manual selection
• Issue appears only when the new renderer is enabled
• Likely related to clipboard encoding or Unicode handling
• This issue does not occur when using the default renderer (i.e., without setting CLAUDE_CODE_NO_FLICKER). Korean text is copied correctly in that case.