Session history: generate titles in the conversation language

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

When using Claude Code in Japanese, session titles in the history panel are always generated in English — even when the entire conversation is in Japanese.

Example:

• User message: 「このパソコンのFinder内のダウンロードの場所にあるファイルやフォルダを種類ごとに分けて整理して」
• Generated title: "Organize Downloads folder by file type"

The date group labels (本日 / 昨日 / 古い順) already respect the system locale, but the title generation does not. This inconsistency is confusing for non-English speakers.

Claude.ai generates session titles in the conversation language — Claude Code should do the same.

Proposed Solution

Update the session title generation prompt to detect the language of the conversation and produce the title in that language, rather than always defaulting to English.

Alternative Solutions

_No response_

Priority

Critical - Blocking my work

Feature Category

CLI commands and flags

Use Case Example

_No response_

Additional Context

_No response_