Desktop i18n

Keep localization organized as:

apps/desktop/
├── plugins/static-i18n-plugin.ts
└── src/i18n/
    ├── I18nRoot.tsx
    ├── runtime.ts
    ├── store.ts
    ├── generated/catalog.json
    └── locales/
        ├── zh-CN.json
        └── en-US.json

Author messages

• Use the global t() function with a static Simplified Chinese string literal: t("保存").
• Do not import or locally declare t.
• Keep calls inside render paths when the result must update after a language change. Do not translate module-level UI constants.
• Use named placeholders with a static object: t("第 {page} 页", { page }).
• Preserve every placeholder name exactly in all translations.
• Wrap all user-visible labels, descriptions, tooltips, empty states, validation messages, and accessibility labels. Do not wrap protocol tokens, model IDs, URLs, or product names that should remain unchanged.

Locale behavior

• system is the default preference.
• Resolve supported operating-system languages to their locale and fall back to en-US for every unsupported language.
• Persist only explicit locale selections. Removing the preference restores system-language behavior.
• Apply changes immediately and update the document lang attribute.

Update catalogs

From apps/desktop:

1. Run npm run i18n:scan after adding or changing t() sources.
2. Translate every empty entry in src/i18n/locales/en-US.json.
3. Never edit src/i18n/generated/catalog.json or zh-CN.json manually; scanning owns them.
4. Run npm run check. A normal build must fail on a missing translation or mismatched placeholder.

When adding another locale, add it to the plugin's supported locales, runtime locale type and messages, locale resolver, settings options, and provide a complete locale JSON file.