[FEATURE]Add a setting to control the language of auto-generated conversation titles

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

Conversation titles in the sidebar (auto-generated "Recents" summaries) are produced server-side and default to English even when the entire conversation is conducted in another language.

I run all my sessions in Japanese, but titles consistently appear in English (e.g., "Smartphone trackpad for PC control" for a fully-Japanese conversation). The sidebar is the primary surface for resuming past work, so English titles in an otherwise-Japanese workflow slow down scanning and force me to manually rename every conversation.

There is currently no settings.json key, environment variable, or CLAUDE.md instruction that influences title generation language. The existing language setting only affects Claude's responses, not titles.

Proposed Solution

Add one of the following (in order of preference):

Make the existing language setting also apply to title generation. Lowest-friction option — users who set language: "ja" already expect a localized experience.
Add a dedicated titleLanguage key in settings.json (e.g., "ja", "en", "auto"), defaulting to "auto" which detects the conversation's dominant language.
At minimum, auto-detect the dominant language of the conversation content and generate the title in that language without requiring any setting.

Alternative Solutions

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Priority

Medium - Would be very helpful

Feature Category

Configuration and settings

Use Case Example

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Additional Context

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