[BUG] Chinese (CJK) characters displayed with orange highlight boxes in conversation/diff panel in vscode

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?

In the vscode Claude Code conversation panel (including the inline diff view shown after file edits), all Chinese (CJK) characters are rendered with visible orange rectangular boxes around them. This does not occur in the standard VSCode editor — opening a Markdown file containing Chinese text displays correctly with no boxes.

Actual Behavior

Every Chinese character in the Claude Code conversation/diff panel is surrounded by an

<img width="2176" height="186" alt="Image" src="https://github.com/user-attachments/assets/a93275de-caa4-4c49-a195-2b4907d15dd9" />

, making output visually cluttered and harder to read.

Troubleshooting Already Attempted

Added editor.unicodeHighlight.allowedLocales: { "zh-hans": true, "zh-hant": true } to settings.json — no effect on the panel.
Added CJK fonts ('Sarasa Mono SC', 'Microsoft YaHei') to editor.fontFamily — no effect on the panel.
Disabled all VSCode extensions except Claude Code — boxes still present. This confirms the issue is in the Claude Code extension's own webview rendering, not caused by any third-party extension.
Additional Notes

The issue is isolated to the Claude Code conversation panel (webview). The same Chinese characters render correctly in the VSCode editor (e.g., opening a .md file containing Chinese text shows no boxes). The webview appears not to inherit VSCode's editor Unicode/font settings.

What Should Happen?

No orange rectangular box for Chinese character.

Error Messages/Logs

Steps to Reproduce

1. Start a Claude Code session in VSCode.
2. Ask Claude to produce a response or file edit that includes Chinese characters.

Observe the conversation panel — all CJK characters are surrounded by orange boxes.

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.196

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_