| name | i18n-translations |
| description | How i18n translations work in the Boilerplate repo. Use when adding or editing translation keys, adding locales, or generating translations so you can do it reliably. |
| version | 1.1.0 |
i18n in Boilerplate
Use this skill whenever you add or change user-facing strings, add a locale, or generate translations. It ensures key parity, correct file layout, and the right commands.
Three-tier layout (per app or package)
Each app with i18n (apps/web, apps/management-web) and the backend package (packages/helpers-i18n) have:
i18n/originals/ — Source of truth. en-US.json is maintained by hand. Other locale files (e.g. es.json) must have the exact same key structure as en-US.json (values can be translated or placeholder).i18n/overrides/ — Human corrections for non–en-US locales. Same keys as originals; non-empty override values win over originals at compile time. Committed.i18n/compiled/ — Merged output (originals + overrides). Generated only; do not commit (in .gitignore). Used at runtime.
Commands (run from repo root)
npm run i18n:sync — Sync originals from en-US for web, management-web, and helpers-i18n: add any keys present in en-US but missing in other locales’ originals with empty string (do not put English into es or other locale files; those must be in the target language, e.g. Spanish for es). Run after adding keys to en-US so key parity is achieved; then translate empty keys to the locale language. The compile step does not sync from en-US; sync is done by this script or by the i18n workflow.npm run i18n:compile — For web, management-web, and helpers-i18n: sync override file structure from each locale’s originals (new keys get empty string in overrides), then merge originals + overrides into compiled. Run after changing originals or overrides.npm run i18n:validate — Check that all locale files (originals + overrides) have the same keys and key order as en-US; en-US originals must have no empty values; non–en-US originals may have empty (pending translation). Overrides match structure. Validates web, management-web, and helpers-i18n. Run in CI and locally before committing i18n changes.
Adding or changing keys
- Edit
i18n/originals/en-US.json in the app (or in each app/package that has the key). Use nested keys and namespaces (e.g. auth.login.title, common.loading, ui.auth.login.email). Do not leave empty values in en-US.
- Other locales: Run
npm run i18n:sync then npm run i18n:compile so originals and overrides for other locales get the new keys (sync adds missing keys with empty string; do not put English in es or other locale files—translate to the target language, e.g. Spanish for es). Alternatively, merge to the mainline branch and let the i18n workflow run sync + compile + validate; then add translations for any new empty keys.
- Run
npm run i18n:validate to confirm (same keys and key order as en-US; only en-US must have no empty).
- In code:
useTranslations('auth') then t('login.title'), or useTranslations('ui') then t('auth.login.email') for UI package keys.
Key conventions
- Namespaces:
auth, common, dashboard, settings, errors, ui (see below).
- UI package: Components in
@boilerplate/ui that render their own text use the ui namespace. Each app must include a full ui object in its i18n/originals/en-US.json (and other locales). Required keys are listed in packages/ui/I18N-KEYS.md. When adding or changing UI strings, update that file and add the key to each app’s originals (and other locales).
Generating translations (other locales)
There is no built-in auto-translate. Translations for non–en-US locales can be generated with an LLM of your choosing (e.g. Cursor chat): provide en-US.json (or the relevant namespace) and ask for a translation that preserves the exact JSON key structure and only changes string values. Then:
- Write the result to the correct
i18n/originals/<locale>.json (or use overrides for corrections).
- Run
npm run i18n:compile and npm run i18n:validate to ensure key parity and compile.
Non–en-US originals must be in the target language
Do not put English text into non–en-US originals (e.g. es.json). Spanish originals must be in Spanish; other locales in their language. The sync script adds missing keys with empty string so they can be filled with the correct translation. When adding or editing translations, use the target language for that locale.
Validation rules (what i18n:validate enforces)
en-US.json exists in originals and has no empty or undefined values.- Non–en-US files in
originals/ may have empty values (pending translation); only en-US is required to have no empty.
- Every file in
originals/ and overrides/ has exactly the same keys as en-US (no missing, no extra) and in the same key order (depth-first) as en-US.
Locale list and environment variables
Locale list and default are defined once in packages/helpers/src/locale/constants.ts (ALL_AVAILABLE_LOCALES, DEFAULT_LOCALE, Locale). Web and management-web import from @boilerplate/helpers; backend (helpers-i18n) re-exports from helpers. Runtime behavior is filtered by env vars DEFAULT_LOCALE and SUPPORTED_LOCALES.
Sync points (all locations to update when adding a locale or changing default/supported)
| Purpose | File |
|---|
| Locale constants (single source of truth) | packages/helpers/src/locale/constants.ts — ALL_AVAILABLE_LOCALES, DEFAULT_LOCALE. Web, management-web, and helpers-i18n use these via @boilerplate/helpers. |
| Web: env var documentation | apps/web/sidecar/.env.example — DEFAULT_LOCALE, SUPPORTED_LOCALES |
| Management-web: env var documentation | apps/management-web/sidecar/.env.example — DEFAULT_LOCALE, SUPPORTED_LOCALES |
DEFAULT_LOCALE (env) — Overrides the default locale (e.g. en-US). Must be one of the values in that app’s ALL_AVAILABLE_LOCALES.SUPPORTED_LOCALES (env) — Unset or all-available: use the full hardcoded list. Comma-delimited (e.g. en-US,es): only those locales are active; values must be in ALL_AVAILABLE_LOCALES.
When you add a new locale (e.g. fr): add the locale to packages/helpers/src/locale/constants.ts (ALL_AVAILABLE_LOCALES). Then add originals/fr.json and (after compile) overrides/fr.json for each app and for packages/helpers-i18n, and run compile and validate. Web and management-web read the list from @boilerplate/helpers; no need to edit their request.ts. Ensure the sidecar .env.example files (apps/web/sidecar/.env.example, apps/management-web/sidecar/.env.example)
document DEFAULT_LOCALE and SUPPORTED_LOCALES if you rely on them; app .env.example files
contain only RUNTIME_CONFIG_URL.
Where things live
| Item | Location |
|---|
| App originals | apps/<app>/i18n/originals/ (e.g. en-US.json, es.json) |
| App overrides | apps/<app>/i18n/overrides/ (e.g. es.json) |
| App compiled | apps/<app>/i18n/compiled/ (generated; do not edit) |
| App locale list / request config | Apps import ALL_AVAILABLE_LOCALES from @boilerplate/helpers; request.ts (or app i18n config) uses that for locale list. |
| Backend i18n (API / management-api) | packages/helpers-i18n/ — same originals/overrides/compiled; resolveLocale(), getPasswordValidationMessages(), email content helpers. User-facing messages only (password validation, email body). |
| Locale constants (all apps + backend) | packages/helpers/src/locale/constants.ts; import from @boilerplate/helpers everywhere. |
| UI keys reference | packages/ui/I18N-KEYS.md |
| Full doc | docs/localization/I18N.md |
i18n workflow (Podverse-style)
When en-US changes are pushed to develop, .github/workflows/i18n.yml runs: sync originals from en-US (add missing keys with en-US value), compile (sync overrides from each locale’s originals, merge to compiled), validate, then commit and push originals + overrides if changed (message: chore: sync i18n keys from en-US [skip ci]). No LLM; key parity is achieved by the sync script. Locally you can run npm run i18n:sync then npm run i18n:compile to get the same result before pushing.
Quick checklist when you add or change strings
When adding a new locale (e.g. fr): add the locale to packages/helpers/src/locale/constants.ts (ALL_AVAILABLE_LOCALES). Web and management-web import from @boilerplate/helpers; helpers-i18n re-exports from helpers. Then add originals/overrides for the new locale in each app and in helpers-i18n (see Sync points above).
