[BUG] Word navigation only works for English letters, not Cyrillic characters

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?

Word navigation using Alt+Arrow (Option+Arrow on macOS) works correctly for English text but doesn't recognize word boundaries for
Cyrillic (Russian) characters in the Claude Code input line.

Word boundary detection appears to only recognize ASCII characters [a-zA-Z], causing Cyrillic and other non-ASCII text to be skipped or treated as non-word characters.

What Should Happen?

Word hop should work for all Unicode alphabetic characters, not just ASCII a-z/A-Z, similar to how it works in standard terminal applications (bash, zsh, etc.)

Error Messages/Logs

Steps to Reproduce

1. Type mixed text in the input line: hello привет world мир
2. Use Option+← / Option+→ (or Alt+← / Alt+→ on non-macOS keyboard) to jump between words
3. Observe that cursor jumps correctly between English words (hello, world) but skips over or doesn't recognize Russian words (привет, мир)

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.0.31 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Word hop works correctly for Cyrillic in the regular terminal (zsh 5.9 (x86_64-apple-darwin22.0)) outside of Claude Code