Internationalization (i18n)

When to use

• Implement or audit localization for supported product locales.

Not for: frontend-design for general layout.

Steps

1. Identify actual locales, tooling, translation ownership and affected surfaces.

2. Extract messages and use locale-aware pluralization, dates, numbers and routing in the actual rendering model.

3. Handle expansion, fonts, accessibility and fallbacks; add or test RTL only when relevant to supported locales.

4. Exercise translations, missing messages, locale persistence and relevant server/client boundaries.

Verify

• Supported messages and formatting are correct; routing and layout evidence covers actual locale requirements.

References

• engineering-principles.md — shared decision boundaries, scope and verification.
• references/i18n-checklist.md — locale-surface audit template, ICU syntax reference, RTL conversion checklist, locale-detection patterns, test-locale matrix
• references/server-i18n.md — RSC / App Router message loading, per-locale bundle splitting, request-scoped locale, hydration alignment