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i18n-expert

This skill should be used when setting up, auditing, or enforcing internationalization/localization in UI codebases (React/TS, i18next or similar, JSON locales), including installing/configuring the i18n framework, replacing hard-coded strings, ensuring en-US/zh-CN coverage, mapping error codes to localized messages, and validating key parity, pluralization, and formatting.

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i18n-expert

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Use i18n-expert to audit and localize [codebase area] for [target locales], replacing user-facing strings with stable keys, localizing error messages, and resolving locale-key parity gaps.

Required inputs

  • [codebase area]
  • [target locales]

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SKILL.md

name: i18n-expertdescription: This skill should be used when setting up, auditing, or enforcing internationalization/localization in UI codebases (React/TS, i18next or similar, JSON locales), including installing/configuring the i18n framework, replacing hard-coded strings, ensuring en-US/zh-CN coverage, mapping error codes to localized messages, and validating key parity, pluralization, and formatting.

I18n Expert

Overview

Deliver a complete i18n setup + audit pass: configure the i18n framework, replace user-facing strings with keys, ensure locale parity, and validate pluralization/formatting for en-US and zh-CN.

Core Capabilities

  • Library selection and setup (React, Next.js, Vue).
  • Key architecture and locale file organization.
  • Translation generation and quality strategy (AI, professional, manual).
  • Routing and language detection/switching.
  • SEO and metadata localization (when applicable).
  • RTL support (only if RTL locales are in scope).

Scope Inputs (ask if unclear)

  • Framework and routing style.
  • Existing i18n state (none, partial, legacy).
  • Target locales (default: en-US + zh-CN).
  • Translation quality needs (AI vs professional vs manual).
  • Locale formats in use (JSON, YAML, PO, XLIFF).
  • Formality/cultural requirements (if any).

Workflow (Audit -> Fix -> Validate)

  1. Confirm scope and locale targets
  • Identify the i18n framework and locale locations.
  • Confirm locales; default to en-US + zh-CN when specified.
  1. Setup i18n baseline (if missing)
  • Choose a framework-appropriate library (e.g., React: react-i18next; Next.js: next-intl; Vue: vue-i18n).
  • Install packages and create the i18n entry/config file.
  • Wire the provider at the app root and load locale resources.
  • Add a language switcher and persistence (route/param/localStorage) as appropriate.
  • Establish locale file layout and key namespaces.
  • If routing is locale-aware, define the locale segment strategy early (subpath, subdomain, query param).
  • If metadata is user-facing, include translation for titles/descriptions.
  1. Audit key usage and locale parity
  • Run: 
    python scripts/i18n_audit.py --src <src-root> --locale <path/to/en-US.json> --locale <path/to/zh-CN.json>
  • Treat missing keys/parity gaps as blockers.
  • Manually verify dynamic keys (t(var)).
  1. Find raw user-facing strings
  • Search: 
    rg -n --glob '<src>/**/*.{ts,tsx,js,jsx}' "<[^>]+>[^<{]*[A-Za-z][^<{]*<"
rg -n --glob '<src>/**/*.{ts,tsx,js,jsx}' "aria-label=\"[^\"]+\"|title=\"[^\"]+\"|placeholder=\"[^\"]+\""
  • Localize accessibility labels.
  1. Replace strings with keys
  • Use t('namespace.key') for UI text.
  • For plurals use t('key', { count }) + _one/_other keys.
  • Use Intl/app formatters for time/date/number.
  1. Localize error handling (critical)
  • Map error codes to localized keys; show localized UI only.
  • Log raw error details only.
  • Provide localized fallback for unknown codes.
  1. Update locale files
  • Add missing keys in both locales.
  • Keep placeholders consistent; avoid renames unless requested.
  • Generate translations using the agreed method; preserve placeholders and plural rules.
  1. Validate
  • Re-run the audit until missing/parity issues are zero.
  • Validate JSON (e.g., python -m json.tool <file>).
  • Update tests asserting visible text.

Guardrails

  • Never expose raw error.message to UI; show localized strings only.
  • Do not add extra locales unless explicitly requested.
  • Prefer structured namespaces (e.g., errors.*, buttons.*, workspace.*).
  • Keep translations concise and consistent.
  • Some technical/brand terms should remain untranslated (e.g., product name, API, MCP, Bash).

Deliverables (expected outputs)

  • i18n config/provider wiring.
  • Locale files for each target language.
  • Replaced UI strings with stable keys.
  • Language switcher and persistence (if applicable).
  • Updated tests for visible text.

Architecture Guidance (keep concise)

  • Key structure: prefer nested namespaces by area (e.g., common.buttons.save, pricing.tier.pro).
  • File layout: one file per locale or per-locale namespaces; keep keys in sync across locales.
  • Placeholders: preserve {name}/{{name}} exactly; validate plurals by locale rules.
  • Formatting: use Intl/app helpers for date, time, number, and list formatting.
  • SEO/metadata: localize titles and descriptions if the app exposes them.
  • RTL: only needed for RTL locales; use logical CSS properties and test layout.
  • Non-web surfaces (Electron main-process dialogs, CLI prompts, native menus) need localization too.

Performance Notes (short)

  • Lazy-load locale bundles when the app supports it.
  • Split large locale files by namespace.

Failure Modes (watchlist)

  • Missing translations: fall back to default locale and log warnings.
  • RTL layout issues: verify logical CSS and test pages.
  • SEO missing: ensure alternates and metadata are localized when applicable.

Validation Checklist (short)

  • No missing keys and no raw UI strings.
  • Locale switching works and persists.
  • Plurals and formatting verified in both locales.
  • Fallback locale configured.

Resources

scripts/

  • scripts/i18n_audit.py: Extracts t('key') usage and compares against locale JSON files.