Add internationalization (i18n) support to Gemini CLI

[hoteye]

What would you like to be added?

Add comprehensive internationalization (i18n) support to Gemini CLI to make it accessible to non-English speaking developers worldwide.

Proposed Implementation:

• Integrate react-i18next for translation management
• Support language detection via GEMINI_LANG environment variable
• Create translation framework for core UI components:
  • Help system (/help command output)
  • Error messages and dialogs
  • Shell confirmation prompts
  • Status indicators and feedback
• Maintain full backward compatibility (English as default)
• Enable community-contributed translations

Technical Approach:

• Minimal performance impact through lazy loading of translation resources
• Type-safe translation keys using TypeScript
• Fallback mechanism to English for missing translations
• Integration with existing React + Ink architecture

Proposed Languages (Initial):

• English (default, no changes needed)
• Chinese (Simplified) - Large developer community
• Spanish - Second most spoken language globally
• French - Strong developer community in Europe/Africa

Example Implementation:

// Before
<Text>Basics:</Text>

// After
<Text>{t('help.basics')}</Text>

Why is this needed?

1. Global Accessibility: Gemini CLI is used by developers worldwide, but currently all UI text is hardcoded in English, creating barriers for non-English speakers.

2. Large International User Base: Search of existing issues reveals numerous IME-related problems for CJK languages (The UI is strange when using Japanese input. #4481, Poor real-time display of Korean IME composition in Gemini CLI #3014, Bug: Chinese IME composition is not handled correctly in the CLI #5833, Korean (Hangul) input drops the last character in Gemini CLI #2797, Chinese input BUG on MacOS #2618, etc.), indicating significant international usage. These users would greatly benefit from localized UI text.

3. Inclusive Design: Aligns with Google's commitment to inclusive design and global accessibility standards.

4. Community Growth: Enables broader community adoption and contribution from international developers.

5. Industry Standard: Modern CLI tools (like git, docker, npm) increasingly support internationalization.

6. Complementary to Existing Work: This proposal would complement the ongoing IME fixes by providing localized interface text for the same international users experiencing input issues.

Additional context

Research Findings:

• Analyzed the current codebase and identified ~197 user-facing text strings that would benefit from internationalization
• Searched existing issues - no duplicate requests found for UI language localization
• Current hardcoded text examples: "Basics:", "Shell mode", "Add context", error messages, confirmation dialogs

Technical Feasibility:

• Implementation can be done incrementally without breaking existing functionality
• React + Ink architecture already supports i18n libraries
• Estimated implementation: 2-3 weeks for core framework + initial languages

Impact Assessment:

• Zero breaking changes to existing functionality
• Opt-in feature (English remains default)
• Enables community contribution of additional languages
• Improves accessibility for international developers

Implementation Plan:

1. Set up i18n infrastructure with react-i18next
2. Extract hardcoded strings to translation keys
3. Implement language detection via environment variables
4. Add initial language packs (Chinese, Spanish, French)
5. Create contribution guidelines for community translations

I have signed the Google CLA and am prepared to implement this feature following the project's contribution guidelines.

[jacob314]

Thanks for the great breakdown of what is required for I18n support. We would welcome pull requests to implement this. Please ping me directly for any pull requests related to this and I will make sure I prioritize reviewing them.

[hoteye]

@jacob314 Hi! I've completed a PoC for i18n implementation. Here's the progress update:

Completed PoC Components

Core i18n Infrastructure

• react-i18next configuration integrated with Ink
• Custom useTranslation hook wrapper
• Bilingual resources (English/Chinese) with namespace design
• Command mapping system for automatic translation

Functional Demo Features

• HelpI18n component with internationalization
• /lang command for language switching (en/zh/current)
• /i18n-test command for demonstration
• Platform-aware keyboard shortcuts display

Technical Validations

Compatibility Testing

• react-i18next integrated with Ink components
• Dynamic language switching implemented
• Interpolation functionality ({{key}} parameters) working
• Namespace separation architecture tested

Dependencies Added

• react-i18next: 332KB (unpackaged)
• i18next: 546KB (unpackaged)
• Translation files: ~4.5KB current PoC implementation

Note: Performance impact analysis pending full integration testing.

Implementation Plan

Based on PoC results, implementation broken down to:

• Core architecture (2 days) - External translation files, dependency integration
• Component expansion (2 days) - AuthDialog, SettingsDialog, command system
• Testing and polish (2 days) - Test suite, documentation, edge cases

Total estimated effort: 6 days

Next Steps

Ready to proceed with full implementation. The PoC has addressed the main technical challenges. Would
appreciate any feedback on the approach before moving forward.

[jacob314]

Great please turn those commits into an early draft pr and I would be happy to review to give some early feedback to make sure it is in the right direction.