[BUG]

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?

Claude Code crashes when processing Japanese text. The error occurs when handling multibyte characters like full-width question mark (？).

What Should Happen?

Claude Code should handle Japanese (and other multibyte) characters without crashing.

Error Messages/Logs

thread '<unnamed>' panicked at library/core/src/str/mod.rs:833:21:
  byte index 29 is not a char boundary; it is inside '？' (bytes 27..30) of `ることはありますか？';`
  fatal runtime error: failed to initiate panic, error 5, aborting
  zsh: abort      claude

Steps to Reproduce

1. Start Claude Code
2. Have a conversation in Japanese
3. Crash occurs randomly when processing Japanese text containing characters like ？ (full-width question mark)

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.0.76 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_