[BUG] Sometimes responses are generated that ignore the language setting.

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?

Despite the user's global-level settings.json correctly setting "language": "Japanese", Claude sometimes returns English responses.

What Should Happen?

At the very least, messages directed at the user (text starting with ●) must be in Japanese.

Error Messages/Logs

Steps to Reproduce

There are no clear conditions; it happens suddenly.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.168

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_