Conversation tab title generated in the wrong language (French title for a Czech conversation)

What happened

The auto-generated conversation tab title in the VSCode extension came out in French for a conversation held entirely in Czech.

• My message: je ticket 313 jeste relevantni? (Czech)
• Generated tab title: Vérifier la pertinence d... (French)

The title-generation step appears to run outside the conversation, so it does not see CLAUDE.md or the conversation language. Here it picked a third language that appears nowhere in the session: neither the user's language (Czech) nor English.

Expected

The tab title should be in the language of the conversation, or at minimum in a consistent, predictable language (e.g. English). It should never be a language that does not appear in the session at all.

Steps to reproduce

1. Open the Claude Code VSCode extension.
2. Send a short first message in a non-English language (Czech here).
3. Look at the generated tab title.

Not deterministic on every run, but recurring with short non-English prompts.

Notes

I could not find any setting that controls the language of generated tab titles. If one exists, it is not discoverable.

Environment

• Claude Code 2.1.232
• VSCode extension
• Windows 11 Pro