{i18n.t('common.greeting', { name: 'World' })}
\n```\n\nThe call reads the reactive translation table and locale, so the text updates\nautomatically when either changes — no stores, no `$` prefix.\n\n## Using Different Parsers\n\n### ICU Message Format\n\n```javascript\nimport i18n from '@sveltekit-i18n/base';\nimport parser from '@sveltekit-i18n/parser-icu';\n\nconst config = {\n parser: parser({ onReport: null }),\n loaders: [/* ... */],\n};\n```\n\n```json\n{\n \"items\": \"You have {count, plural, =0 {no items} one {# item} other {# items}}.\"\n}\n```\n\n### Custom Parser\n\n```javascript\nimport i18n from '@sveltekit-i18n/base';\n\nconst customParser = () => ({\n parse: (value, params) => {\n // Your custom interpolation logic\n return value.replace(/\\{(\\w+)\\}/g, (_, key) => params[0]?.[key] ?? key);\n },\n});\n\nconst config = {\n parser: customParser(),\n loaders: [/* ... */],\n};\n```\n\nLearn more about [creating custom parsers](https://github.com/sveltekit-i18n/parsers#creating-custom-parsers).\n\n## Configuration Options\n\n### `parser` (required)\n\nMessage parser instance. See [Parsers](https://github.com/sveltekit-i18n/parsers).\n\n### `loaders`\n\nArray of loader configurations:\n\n```javascript\nloaders: [\n {\n locale: 'en', // Required: locale identifier\n key: 'common', // Required: translation namespace\n loader: async () => {}, // Required: async function returning translations\n routes: ['/about'], // Optional: load only for specific routes\n },\n]\n```\n\nBoth `loaders` and a loader's `routes` accept readonly arrays, so a whole-config `as const` is fine.\n\n### `translations`\n\nSynchronous translations loaded immediately:\n\n```javascript\ntranslations: {\n en: {\n 'app.name': 'My App',\n },\n}\n```\n\n### `initLocale`\n\nInitialize with a specific locale immediately:\n\n```javascript\ninitLocale: 'en'\n```\n\n### `fallbackLocale`\n\nFallback when translation is missing:\n\n```javascript\nfallbackLocale: 'en'\n```\n\n**Note:** This loads translations for both current locale and fallback locale, which may impact performance.\n\n### `fallbackValue`\n\nDefault return value when translation key is not found:\n\n```javascript\nfallbackValue: '...' // Default: returns the key itself\n```\n\n### `preprocess`\n\nTransform translations after loading:\n\n```javascript\npreprocess: 'full' // 'full' | 'preserveArrays' | 'none' | custom function\n```\n\n- `'full'` (default): Flattens all nested objects to dot notation\n- `'preserveArrays'`: Flattens objects but preserves arrays\n- `'none'`: No preprocessing\n- Custom function: `(input) => transformedOutput`\n\n### `schema`\n\nA map of translation key to the payload its message expects (`never` for a message that takes none). Supplying it types `t`/`l` — keys autocomplete, an unknown key is a type error, and the payload argument is checked. Only its type is read, so the value can stay empty at runtime:\n\n```typescript\ntype TranslationSchema = {\n 'common.greeting': { name: string };\n 'common.farewell': never;\n};\n\nconst i18n = new I18n({ ...config, schema: {} as TranslationSchema });\n```\n\nHand-write it for a small set of messages, or point the slot at a generated artifact. A schema whose keys are not a closed set is ignored, and keys stay plain strings. See [`schema`](./docs/README.md#schema) for the full rules.\n\n### `cache`\n\nTime in milliseconds the loaded translations stay fresh for. By default, loaded translations never expire — loaders run once per locale and key (a loader's `routes` only decide whether a load trigger considers it, not how often it runs).\n\nSet a finite value when your loaders fetch from a source that can change at runtime (e.g. a CMS):\n\n```javascript\ncache: 3600000 // Translations older than 1 hour refetch on the next load\n```\n\nSet to `0` to treat translations as always stale (refetch on every load trigger). You can also drop the loaded state manually at any time with [`invalidate()`](#methods).\n\n### `extensions`\n\nPipes the constructed instance through extension functions, left to right. Each extension receives the surface produced so far (the raw instance for the first one) and returns the surface handed on — `new I18n(config)` evaluates to the last extension's output:\n\n```javascript\nimport stores from '@sveltekit-i18n/extension-stores';\n\nconst { t, locale, loading } = new I18n({\n ...config,\n extensions: [stores],\n});\n```\n\nAn extension may augment the instance in place, or replace the surface entirely (like the store adapter above). Official extensions live in the [extensions](https://github.com/sveltekit-i18n/extensions) repository; a custom extension is just a function:\n\n```javascript\nconst withGreeting = (i18n) => Object.assign(i18n, {\n greet: (name) => i18n.t('common.greeting', { name }),\n});\n\nexport const i18n = new I18n({ ...config, extensions: [withGreeting] });\n\ni18n.greet('World');\n```\n\n**Notes:**\n- Applied at construction time only — a later `loadConfig()` call ignores this property.\n- When an extension returns a new object, the result is no longer `instanceof I18n`; the original instance stays reachable through whatever the extension exposes (the official extensions expose it as `instance`).\n\n### `log`\n\nLogging configuration:\n\n```javascript\nlog: {\n level: 'warn', // 'error' | 'warn' | 'debug'\n prefix: '[i18n]: ', // Log prefix\n logger: console, // Custom logger\n}\n```\n\n## API Reference\n\n### Reactive properties\n\n- `t(key, ...params)` – translate for the active locale (reactive function)\n- `l(locale, key, ...params)` – translate for an explicit locale\n- `locale` – the ACTIVE locale; assignment is a fire-and-forget `setLocale()`\n- `locales` – available locales\n- `loading` – `true` while any load is in flight\n- `initialized` – locale and route set, translations present\n- `translations` / `rawTranslations` – the (pre/post-preprocess) tables\n\n### Methods\n\nLoad-triggering methods return the promise of the matching load — concurrent duplicate triggers share one in-flight load (and its promise) instead of fetching twice.\n\n- `loadTranslations(locale, route?)` – load translations for locale and route; `route` defaults to the current one\n- `setLocale(locale)` – request a locale; loads once a route is known\n- `setRoute(route)` – update the current route\n- `loadConfig(config)` – (re)configure the instance\n- `addTranslations(translations)` – add synchronous translations\n- `snapshot()` – serialize the active locale (and the fallback) for the current route, shaped like `config.translations` so the receiving instance hydrates by passing it to `addTranslations()`\n- `invalidate(locale?)` – mark loaded translations stale (one locale, or all); loaders run again on the next load trigger, and a load still in flight for an invalidated locale settles with its data discarded\n- `destroy()` – detach a per-request or per-component instance: in-flight loads settle discarded, further load and mutation calls are ignored, reads keep working\n\n### Utilities\n\nTwo helpers the instance uses internally ship from a separate subpath, for code that has to match the library's own behavior:\n\n```javascript\nimport { sanitizeLocales, toDotNotation } from '@sveltekit-i18n/base/utils';\n```\n\n- `toDotNotation(input, preserveArrays?)` – the flattening behind [`preprocess`](#preprocess), for a custom `preprocess` that still wants dot notation\n- `sanitizeLocales(...locales)` – normalizes a locale from a URL, cookie or `Accept-Language` header the way the instance does, so it can be compared against `locale`\n\nFull API documentation: [docs/README.md](./docs/README.md)\n\n## Documentation\n\n- 📖 [Full API Documentation](./docs/README.md) – Complete reference\n- 📚 [Main Library Docs](https://github.com/sveltekit-i18n/lib/tree/master/docs/INDEX.md) – Guides, tutorials, and best practices\n- 🎨 [Parsers](https://github.com/sveltekit-i18n/parsers) – Available parsers and how to create your own\n- 💡 [Examples](https://github.com/sveltekit-i18n/lib/tree/master/examples) – Real-world usage examples\n\n## TypeScript Support\n\n```typescript\nimport { I18n, type Config } from '@sveltekit-i18n/base';\nimport parser from '@sveltekit-i18n/parser-curly';\n\n// The parser's params – the rest parameters of `t`/`l`. Annotate only when the\n// config lives on its own; `new I18n({ ... })` infers them.\ntype Params = [payload?: Record