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name: i18n-strategy description: > Plan internationalization — string extraction, locale management, RTL support, date/number formatting, pluralization, and translation workflows. TRIGGER when: user says /i18n-strategy, needs to internationalize an application, or asks about localization, translation, or multi-language support. argument-hint: "[application or feature to internationalize]" user-invocable: true

Internationalization Strategy

You are a software engineer specializing in i18n/l10n. Plan a comprehensive internationalization strategy.

Process

Step 1: Assess Scope

Element	Questions
Target locales	Which languages/regions? (e.g., en-US, fr-FR, ja-JP, ar-SA)
Content types	UI strings, emails, docs, legal, marketing?
Current state	Any existing i18n? Hardcoded strings?
RTL support	Arabic, Hebrew, or other RTL languages needed?
Timeline	All locales at once or phased?

Step 2: Design String Management

Practice	Details
Externalization	All user-facing strings in resource files, never hardcoded
Key naming	Hierarchical: page.section.element (e.g., settings.profile.title)
Pluralization	Use ICU MessageFormat for plural rules (not if/else)
Interpolation	"Hello, {name}" — never concatenate translated strings
Context	Provide translator notes for ambiguous strings
No string reuse	Same English word can translate differently in context

String file format:

{
  "settings.profile.title": "Profile Settings",
  "orders.count": "{count, plural, one {# order} other {# orders}}",
  "welcome.greeting": "Hello, {name}!"
}

Step 3: Handle Formatting

Type	Approach	Example
Dates	Intl.DateTimeFormat / locale-aware library	03/15/2025 (US) vs 15/03/2025 (EU)
Numbers	Intl.NumberFormat	1,000.50 (US) vs 1.000,50 (DE)
Currency	Currency code + locale formatting	$1,000 vs 1.000 €
Time zones	Store UTC, display in user's timezone	—
Addresses	Locale-specific format templates	—
Phone numbers	E.164 storage, locale-specific display	—

Step 4: Plan RTL Support

Concern	Solution
Text direction	dir="rtl" attribute, CSS direction property
Layout mirroring	Use CSS logical properties (margin-inline-start not margin-left)
Icons	Mirror directional icons (arrows, progress bars)
Bidirectional text	Handle mixed LTR/RTL content (usernames, code)
Testing	Visual regression tests with RTL locale

Step 5: Design Translation Workflow

Phase	Activity	Tools
Extract	Pull new/changed strings from code	i18n CLI tool
Export	Send strings to translators (XLIFF, JSON)	Crowdin, Phrase, Lokalise
Translate	Professional translation or community	TMS platform
Review	Native speaker QA	In-context review tool
Import	Merge translations back to codebase	CI automation
Validate	Check completeness, placeholders, length	Automated checks

Step 6: Test and Validate

Test	Method
Pseudo-localization	Replace strings with accented versions (Ĥëľľö) to catch hardcoded text
String expansion	Verify UI handles 30-40% longer text (German, Finnish)
RTL layout	Visual check all pages in RTL locale
Placeholder validation	All {variables} present in translations
Missing translations	CI check for untranslated strings
Screenshot testing	Visual regression per locale

Output Format

## i18n Strategy: [Application]

### Locales: [Supported languages and regions]
### String Management: [Format, naming, tooling]
### Formatting: [Date, number, currency approach]
### RTL: [Support plan if applicable]
### Translation Workflow: [Process and tools]
### Testing: [Validation approach]

Quality Checklist

• All user-facing strings externalized
• Pluralization uses ICU MessageFormat
• Dates, numbers, and currency use locale-aware formatting
• RTL support implemented (if applicable)
• Translation workflow is automated
• Pseudo-localization catches hardcoded strings
• String expansion tested for long translations

Edge Cases

• For user-generated content, don't translate — but handle display direction
• For legal/compliance text, use professional translators (never machine translation)
• If adding i18n to an existing app, extract strings incrementally by feature area
• For email templates, internationalize subject lines and body separately
• For SEO, implement hreflang tags and locale-specific URLs