[BUG] VSCode Extension Input Corrupts Latin Letters to Cyrillic Lookalikes

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?

Cyrillic in draft: NONE - clean

Bug Report: VSCode Extension Input Corrupts Latin Letters to Cyrillic Lookalikes

Environment

• Claude Code VSCode extension (latest)
• Windows 11
• Chinese IME (Microsoft Pinyin / Sogou Pinyin)

Summary
When typing mixed Chinese-English text in the VSCode extension chat input, certain Latin capital and lowercase letters are silently replaced with visually identical Cyrillic characters.

Affected characters (confirmed)

• C (U+0043) -> Cyrillic C (U+0421)
• A (U+0041) -> Cyrillic A (U+0410)
• E (U+0045) -> Cyrillic E (U+0415)
• e (U+0065) -> Cyrillic e (U+0435)
• o (U+006F) -> Cyrillic o (U+043E)
• y (U+0079) -> Cyrillic y (U+0443)

Verification method

• Same text typed in Windows Notepad and verified clean via https://www.babelstone.co.uk/Unicode/whatisit.html
• Same text submitted via PowerShell claude CLI: clean, no Cyrillic
• Only the VSCode extension input produces corrupted characters

Impact
This is a security-relevant bug. Cyrillic homoglyph substitution is a known prompt injection technique. File paths and commands containing these corrupted characters will silently fail. Users have no way to detect the corruption visually.

What Should Happen?

Claude should input and output pure ASCII anyway、anytime

Error Messages/Logs

Steps to Reproduce

Reproduction steps

1. Open Claude Code in VSCode on Windows with a Chinese IME active
2. Type a message containing mixed Chinese and English, e.g.: "please update CLAUDE.md and memory.md"
3. Submit the message
4. The text appears visually identical but contains Cyrillic lookalikes

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

1.23.104

Platform

Other

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_