| name | localization-toolkit |
| description | 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)
- Confirm scope and locale targets
- Identify the i18n framework and locale locations.
- Confirm locales; default to en-US + zh-CN when specified.
- 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.
- Audit key usage and locale parity
- 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.
- 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.
- 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.
- 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.
- 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.
