[FEATURE] Multilingual chat session 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

As a Korean-speaking developer, I write nearly all my prompts to Claude Code in Korean. Claude's responses are correctly rendered in Korean (via language: "korean" in settings.json and/or project-level instructions), but the auto-generated session titles shown in the VSCode extension sidebar are always generated in English, regardless of the input language or the language setting.

This creates a jarring mismatch in my workflow: my messages are in Korean, Claude's answers are in Korean, but the sidebar — which is how I navigate between dozens of ongoing sessions — is a wall of English summaries that don't match the language of the actual conversation content. It's harder to scan, harder to recognize sessions at a glance, and harder to search for past work by keyword (since I naturally remember the topic in Korean, not English).

The language setting in settings.json currently only affects Claude's response text, not the title/summary generator. There is no documented option to control the language of session title generation.

Proposed Solution

Ideally, the existing language setting in settings.json would also apply to auto-generated session titles, so that a user who sets "language": "korean" gets both Korean responses AND Korean session titles — consistent behavior across all text that Claude produces.

If extending language is too broad a change, an alternative would be to add a separate summaryLanguage (or titleLanguage) setting that users can configure independently. A third option would be to default session title generation to match the language of the first user message automatically.

Any of these would solve the problem. The key outcome I want: when I look at my sidebar, session titles are in the same language as the conversations themselves.

Alternative Solutions

_No response_

Priority

Medium - Would be very helpful

Feature Category

CLI commands and flags

Use Case Example

1. I open a new Claude Code session in VSCode and type (in Korean):

"교환 철회 완료시에 이전 페이지로 이동하게 될텐데, 아마 교환 상세페이지로 이동하면 거기서 다시 한번 더 이동하는 로직이 있을거야. (...) 이게 맞는지 현황 파악해봐 각각 시나리오별로 코드 로직 기반으로."

1. Claude correctly analyzes the code and responds in Korean.

1. I check the sidebar to find this session later — the auto-generated title reads:Analyze exchange cancellation return page logic

1. I have 15+ ongoing sessions, all with English titles, but all about Korean-language business logic discussions. To find this specific one, I have to either mentally translate every title or open each session to check the content.

Expected: The title would read something like 교환 철회 완료 후 페이지 이동 로직 분석 — matching the language I actually think and work in.

Additional Context

_No response_