[BUG] Option+Backspace incorrect behavior with Cyrillic text

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?

Option+Backspace deletes unpredictably more text than expected when working with Cyrillic characters, while working correctly with Latin text.

What Should Happen?

Expected Behavior:
Option+Backspace should delete exactly one word, regardless of script
(Latin/Cyrillic)

Actual Behavior:
With Cyrillic text, multiple words are deleted unpredictably

Error Messages/Logs

Steps to Reproduce

1. Open Claude Code IDE
2. Type Cyrillic text: это тестовый текст на русском языке
3. Position cursor at the end of text
4. Press Option+Backspace multiple times
5. Observe that more than one word is deleted each time

Claude Model

Other

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

 1.0.119

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

Environment:

• OS: macOS 15.5 (24F74)
• Claude Code Version: 1.0.119
• System Language: Russian (ru-RU)
• System Locale: ru_RU