rerune 0.10.0

OTA localization updates for Flutter apps with build_runner code generation.

rerune

OTA localization updates for Flutter apps.

ReRune layers server-provided translations on top of your generated AppLocalizations values, without changing how you call localization getters in widgets.

Remote Language Delivery

ReRune's core OTA value is remote language delivery: add a new supported language in the ReRune dashboard and make it available to already-installed apps without shipping a new app-store build just for that language.

After the SDK fetches or loads the dashboard language bundle from cache, the locale appears in ReRune.supportedLocales. Apps can let the device locale resolve to it automatically, or build a language picker from ReRune.supportedLocales so remote languages appear next to compiled app locales.

The app still ships the generated localization API and at least one compiled fallback locale. ReRune updates values for existing keys and expands the runtime locale list from dashboard data.

Requirements

• Flutter >=3.22.0
• Dart >=3.4.0

Install

dependencies:
  rerune: ^0.10.0

dev_dependencies:
  # Optional: needed only if you use the build_runner path below.
  build_runner: ^2.4.13

Standard Integration (Recommended)

1) Generate Flutter localizations

flutter gen-l10n

2) Generate ReRune localization config

Fast path (ReRune-only generation):

dart run rerune

Alternative (build_runner pipeline):

dart run build_runner build --delete-conflicting-outputs

Both commands generate identical *.rerune.g.dart artifacts. Parity is protected by dedicated drift-guard tests in CI.

With default Flutter l10n naming, ReRune generates:

• lib/.../app_localizations.rerune.g.dart
• reRuneAppLocalizationsConfig

No manual anchor class or annotation file is needed.

3) Wire ReRune.setup(...) in main()

import 'package:flutter/widgets.dart';
import 'package:rerune/rerune.dart';

import 'l10n/gen/app_localizations.rerune.g.dart';

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();

  await ReRune.setup(
    otaPublishId: 'your-ota-publish-id',
    localizations: reRuneAppLocalizationsConfig, // Generated by rerune/build_runner
    updatePolicy: const ReRuneUpdatePolicy(checkOnStart: true),
  );

  runApp(const MyApp());
}

4) Use ReRune delegates/locales in your app

MaterialApp(
  localizationsDelegates: ReRune.localizationsDelegates,
  supportedLocales: ReRune.supportedLocales,
)

Use ReRune.supportedLocales anywhere you need the current runtime locale list, including custom language pickers. The list starts with compiled app locales and expands with fetched or cached dashboard languages.

Runtime APIs

• Setup and load cached bundles: await ReRune.setup(...)
• Check manually: await ReRune.checkForUpdates()
• Listen to applied updates: ReRune.onFetchedTextsApplied.listen(...)
• Rebuild subtree on any localization revision: ReRuneBuilder(builder: ...)
• Listen to any localization revision: ReRune.localizationsRevisionListenable

Dashboard-Only Locale Additions

This is the remote-language delivery path for apps that want language expansion to be controlled from the dashboard. await ReRune.setup(...) loads cached manifest/ARB bundles before the first app frame, so a dashboard-only locale fetched during a previous run is available in ReRune.supportedLocales before MaterialApp resolves the device locale. If checkOnStart is enabled, the network refresh starts in the background after cached bundles are loaded; it does not block setup.

After a successful manifest/update fetch, ReRune.supportedLocales contains the app's compiled locales plus dashboard locales whose ARB bundle has been fetched or loaded from cache. The generated delegate uses the app's first compiled locale as the fallback base when Flutter's generated delegate cannot load a dashboard-only locale.

Missing-Key OTA Fallback

The backend manifest declares the project's source locale through main_language. When a key is missing from the requested OTA locale, ReRune resolves it in this order:

requested OTA locale variants
-> OTA main_language variants
-> bundled Flutter localization

For example, an es_MX request with main_language: "en" resolves through es_MX, es, and then OTA en before using the bundled Flutter value. Lookup is per key, so an available es_MX bundle that lacks one key does not prevent that key from falling back through es and en.

Placeholder, plural, and select messages use the locale of the OTA bundle that supplied the value. An English OTA fallback therefore uses English plural rules even when the active app locale is Spanish, Polish, or Arabic.

Manifests without main_language keep the previous behavior: requested OTA locale variants followed directly by the bundled Flutter localization.

Language Pickers

Build language pickers from ReRune.supportedLocales rather than from the compiled AppLocalizations.supportedLocales list. That gives consumers one source of truth for:

• locales bundled into the app at build time
• dashboard-only locales that were fetched in this run
• dashboard-only locales loaded from cache during startup

If a picker must update immediately after a same-run background fetch, rebuild it from ReRuneBuilder or listen to ReRune.localizationsRevisionListenable. Without that rebuild, the newly fetched language is available on the next app launch after await ReRune.setup(...) loads it from cache.

ReRune does not own the selected app locale. Keep that state in your app, for example with a small LocaleNotifier, Riverpod, Bloc, or your existing app settings model. Use ReRune.supportedLocales for picker options and pass your selected locale to MaterialApp.locale. Apps without a language picker can omit MaterialApp.locale entirely and keep Flutter's normal system-locale resolution.

class LocaleNotifier extends ValueNotifier<Locale?> {
  LocaleNotifier(super.value);
}

final LocaleNotifier localeNotifier = LocaleNotifier(null);

ReRuneBuilder(
  builder: (_) => ValueListenableBuilder<Locale?>(
    valueListenable: localeNotifier,
    builder: (_, locale, __) {
      return MaterialApp(
        locale: locale, // Optional: only for app-owned picker overrides.
        localizationsDelegates: ReRune.localizationsDelegates,
        supportedLocales: ReRune.supportedLocales,
      );
    },
  ),
)

Set the notifier from your picker. Setting it to null returns to Flutter's normal device-locale resolution.

DropdownButton<Locale?>(
  value: localeNotifier.value,
  hint: const Text('System default'),
  items: [
    const DropdownMenuItem<Locale?>(
      value: null,
      child: Text('System default'),
    ),
    ...ReRune.supportedLocales.map((locale) {
      return DropdownMenuItem<Locale?>(
        value: locale,
        child: Text(locale.toLanguageTag()),
      );
    }),
  ],
  onChanged: (locale) {
    localeNotifier.value = locale;
  },
)

Any non-null selected locale should come from ReRune.supportedLocales. A custom LocaleNotifier does not collide with ReRune because ReRune does not expose its own selected-locale setter. ReRune does not fetch unavailable languages from picker selection; dashboard-only languages appear in the list only after their ARB bundle is fetched or loaded from cache.

Startup Modes

Use awaited setup when you want deterministic second-run locale support without waiting on the network:

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();

  await ReRune.setup(
    otaPublishId: 'your-ota-publish-id',
    localizations: reRuneAppLocalizationsConfig,
  );

  runApp(const MyApp());
}

Use the builder when you also want the app to follow the device language immediately after a same-run background fetch:

ReRuneBuilder(
  builder: (_) => MaterialApp(
    localizationsDelegates: ReRune.localizationsDelegates,
    supportedLocales: ReRune.supportedLocales,
  ),
)

Limits:

• Without ReRuneBuilder or another rebuild trigger, a locale fetched during the current run is picked up by MaterialApp on the next launch after await ReRune.setup(...) loads it from cache.
• ReRune does not store the selected app locale. Apps with language pickers should keep that state themselves and pass it to MaterialApp.locale; null still means Flutter resolves the system language normally.
• New localization keys or changed placeholder signatures still require running flutter gen-l10n and dart run rerune, then shipping an app update.
• Platform/app-store language metadata and OS-level language listings are not changed by OTA localization.

Advanced And Custom Integrations

Custom Flutter l10n class/file names

If your app does not use app_localizations.dart / AppLocalizations, add a build.yaml in the app root:

targets:
  $default:
    builders:
      rerune|re_rune_localizations_overlay:
        generate_for:
          - lib/**/my_localizations.dart
        options:
          localizations_file_name: my_localizations.dart
          localizations_class_name: MyLocalizations

Then run:

flutter gen-l10n
dart run rerune

# or

dart run build_runner build --delete-conflicting-outputs

This generates my_localizations.rerune.g.dart and reRuneMyLocalizationsConfig.

Use it in startup:

import 'package:rerune/rerune.dart';

import 'l10n/gen/my_localizations.rerune.g.dart';

void main() {
  ReRune.setup(
    otaPublishId: 'your-ota-publish-id',
    localizations: reRuneMyLocalizationsConfig,
  );

  runApp(const MyApp());
}

Disable automatic startup fetch

ReRune.setup(
  otaPublishId: 'your-ota-publish-id',
  localizations: reRuneAppLocalizationsConfig, // Generated by rerune/build_runner
  updatePolicy: const ReRuneUpdatePolicy(checkOnStart: false),
);

Schedule periodic refresh in hours or days

ReRune.setup(
  otaPublishId: 'your-ota-publish-id',
  localizations: reRuneAppLocalizationsConfig,
  updatePolicy: const ReRuneUpdatePolicy(
    checkOnStart: true,
    periodicIntervalInHours: 2,
    periodicIntervalInDays: 3,
  ),
);

ReRuneUpdatePolicy only accepts whole-hour or whole-day periodic refresh intervals. If both fields are set, they are combined into a single refresh cadence. On web, if the combined interval exceeds the supported timer limit, ReRune clamps it to the maximum supported delay (24 days and 20 hours) instead of throwing.

Trigger updates from UI actions

final result = await ReRune.checkForUpdates();
if (result.hasErrors) {
  // show error state
}

Provide your own cache store

If you need custom storage behavior, implement ReRuneCacheStore and pass it to ReRune.setup(cacheStore: ...).

Troubleshooting

• Target of URI hasn't been generated: run flutter gen-l10n, then dart run rerune (or dart run build_runner build --delete-conflicting-outputs).
• Undefined name reRune...Config: generated .rerune.g.dart file is missing, stale, or imported from a wrong path.
• Changed l10n keys/signatures: rerun both generators.

License

This package is proprietary software.

• Copyright (c) 2026 BasalBit GmbH. All rights reserved.
• Commercial license terms: https://rerune.io/terms
• Issue tracker: https://rerune.io/issue-tracker