flutter-internationalization
Add, fix, audit, and maintain Flutter internationalization with gen-l10n, ARB files, AppLocalizations, flutterlocalizations, intl formatting, plural/select messages, RTL support, locale-specific number/date formatting, and localization build errors. Use when asked to add l10n or i18n, translate Flutter UI text, configure l10n.yaml, manage ARB translations, migrate away from package:fluttergen imports, or troubleshoot generated localization code.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/madteacher/mad-agents-skills --skill flutter-internationalization- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads flutter-internationalization automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
Flutter Internationalization
You are a Flutter localization implementer. Make localized apps build, generate, and read naturally across target locales.
Principle 0
Generated localization code must match the current Flutter project and SDK. Do
not copy stale package:flutter_gen imports or enable synthetic-package; use
source-generated AppLocalizations imports unless the project proves it is on an
older pinned Flutter workflow.
Decision Guide
- Use
gen-l10nfor new work, most migrations, ARB management, plural/select messages, generatedAppLocalizations, and Material/Cupertino apps. - Use legacy
intl_translationonly when the project already usesIntl.message()plus generatedmessages_all.dart, or the user explicitly asks to keep that workflow. Confirmintl_translationis a dependency before running its generators. - Use custom map-based localizations only for tiny prototypes or existing code that intentionally avoids code generation. Name this limitation in the final response.
- If the project has an existing localization setup, follow its paths, class names, locale list, and generation style before introducing defaults.
Workflow
- Inspect
pubspec.yaml,l10n.yaml, existing*.arbfiles, generated imports,MaterialApp/CupertinoAppsetup, and current translation usage. - Identify the requested change: bootstrap l10n, add a locale, replace hardcoded UI text, add placeholders/plurals/selects, format values, fix generation, or migrate stale imports/config.
- Use the decision guide to choose
gen-l10n, legacyintl_translation, or a custom fallback. Prefer the smallest change that fits the existing project. - Read only the routed references needed for the task.
- Make the localization change:
- add
flutter_localizationsandintl:anywhen missing; - set
flutter: generate: true; - create or update
l10n.yaml; - create or update ARB files with descriptions and placeholder metadata;
- wire
AppLocalizationsintoMaterialApporCupertinoApp; - replace hardcoded UI strings with generated getters or methods.
- add
- Generate and validate with
flutter gen-l10n. Then run the narrowest relevant project check, usuallyflutter analyzeor affected tests. - Report changed files, generated behavior, validation run, and any locales or translation gaps that remain.
Resource Routing
| Task | Read or use | Why |
|---|---|---|
Configure or debug l10n.yaml, generated output paths, nullable getters, deferred loading, or untranslated tracking | references/l10n-config.md | Current gen-l10n options and safe defaults |
| Create or repair ARB messages, placeholders, plurals, selects, escaping, or metadata | references/arb-format.md | ARB schema patterns and translator context rules |
| Add number, currency, percent, or date/time formatting | references/number-date-formats.md | Supported NumberFormat and DateFormat values |
| Bootstrap a new gen-l10n setup or run a smoke fixture | assets/l10n.yaml, assets/app_en.arb | Reusable minimal templates |
gen-l10n Contract
For new gen-l10n setup, the minimum current configuration is:
flutter:
generate: true
arb-dir: lib/l10n
template-arb-file: app_en.arb
output-localization-file: app_localizations.dart
Use source imports that match the generated location, commonly:
import 'l10n/app_localizations.dart';
Prefer generated lists when possible:
localizationsDelegates: AppLocalizations.localizationsDelegates,
supportedLocales: AppLocalizations.supportedLocales,
If generated files are written to a custom output-dir, update imports to that
directory. Do not import package:flutter_gen/gen_l10n/app_localizations.dart
unless the local project is intentionally pinned to an older Flutter workflow.
Legacy Intl Fallback
When preserving Intl.message():
- require
intl_translationin dev dependencies before extraction/generation; - keep generated files and imports consistent with the existing project;
- run extraction before generation;
- on Windows or shells without wildcard expansion, list ARB files explicitly.
Typical commands:
dart run intl_translation:extract_to_arb --output-dir=lib/l10n lib/main.dart
dart run intl_translation:generate_from_arb --output-dir=lib/l10n --no-use-deferred-loading lib/main.dart lib/l10n/intl_*.arb
If this workflow is not already present, explain why gen-l10n is the safer
default.
Constraints
- Do not invent translations. If target-language text is not supplied, add clear placeholder translations only when the user approved that, or report the missing translations.
- Do not concatenate localized strings. Use placeholders, plural, or select messages.
- Do not manually format numbers, currency, percentages, dates, or times when gen-l10n placeholder formatting can do it.
- Do not add
synthetic-package: true; current Flutter marks synthetic package generation as deprecated and unavailable. - Set
nullable-getter: falseonly when the project accepts non-null generated getter behavior. Otherwise keep the project default and use the required null handling in code. - Keep translator-facing descriptions and examples in the template ARB file.
- For RTL locales, check text direction, layout assumptions, mirrored icons, and locale-specific widgets.
Validation
Always validate a completed localization change:
flutter gen-l10nsucceeds with the project'sl10n.yaml;- generated import paths compile;
- every new ARB key exists in the template file and needed locale files;
- placeholders in translated ARB values match template metadata;
- plural/select messages include
other; - number/date placeholders use supported formats from
references/number-date-formats.md; - relevant
flutter analyzeor tests pass, or blockers are reported.
For skill maintenance, also check YAML frontmatter, local markdown links, JSON
validity for ARB assets, YAML validity for l10n.yaml, resource routing, and
layer coherence between SKILL.md, references, and assets.
FAQ
What does the flutter-internationalization skill do?
Add, fix, audit, and maintain Flutter internationalization with gen-l10n, ARB files, AppLocalizations, flutterlocalizations, intl formatting, plural/select messages, RTL support, locale-specific number/date formatting, and localization build errors. Use when asked to add l10n or i18n, translate Flutter UI text, configure l10n.yaml, manage ARB translations, migrate away from package:fluttergen imports, or troubleshoot generated localization code.
How do I install flutter-internationalization?
Run npx skills add https://github.com/madteacher/mad-agents-skills --skill flutter-internationalization in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/flutter-internationalization/ (personal) or .claude/skills/flutter-internationalization/ (project).
Which AI agents can use flutter-internationalization?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is flutter-internationalization safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains flutter-internationalization?
It is published by madteacher in madteacher/mad-agents-skills. It has 537 recorded installs.
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