UI Localization / i18n support — Portuguese (pt-BR) and other languages

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

The Claude Code interface is only available in English. All menus, commands, status messages, tooltips, and UI text are displayed in English regardless of the user's language preference or system locale.

This creates a barrier for non-English speakers — particularly the large Portuguese-speaking developer community (Brazil + Portugal) — who must navigate an English-only interface even when they have "language": "portuguese" configured in settings.json (which only affects Claude's responses, not the UI itself).

Non-English developers should not have to work in a foreign language to use their development tools.

Proposed Solution

Add internationalization (i18n) support to Claude Code so that the UI language can be configured separately from the AI response language.

Proposed implementation:

• Add a "uiLanguage" setting to settings.json (e.g., "uiLanguage": "pt-BR")
• Or extend the existing "language" setting to also control UI language
• Translate all interface text: menus, slash command descriptions, status messages, error messages, spinner verbs, tips, and prompts

Initial language targets: Portuguese (pt-BR), Spanish (es), French (fr), German (de), Japanese (ja), Chinese (zh-CN)

This is standard i18n practice used by most developer tools (VS Code, JetBrains IDEs, etc.).

Alternative Solutions

• The "language" setting in settings.json only changes the language of Claude's AI responses — it does not affect the UI at all.
• No other workaround exists to change the interface language.
• Users currently must rely entirely on English UI regardless of their preference.

Priority

Medium - Would be very helpful

Feature Category

Configuration and settings

Use Case Example

_No response_

Additional Context

_No response_