Fix: Correcting Language Line fallback resolver

docs/localization.md

@@ -178,6 +178,24 @@ namespaced groups so nothing collides. `__()` resolves the translation for whate
 `App::getLocale()` currently is, which `LocaleMiddleware` already sets per-request (see
 "Behavior" above) — no extra wiring needed between the two systems.
 
+### Fallback locale follows the store's default language, not `config('app.fallback_locale')`
+
+`spatie/laravel-translation-loader`'s stock `LanguageLine::getTranslation()` falls back to
+`config('app.fallback_locale')` — a static `.env` value — when a key has no text for the current
+locale. That's a second, disconnected "default language" concept: an admin changing the default
+language via the Filament **Languages** resource has no effect on it, so an untranslated label
+could silently fall back to the wrong language.
+
+`Modules\Core\Localization\Models\LanguageLine` overrides `getTranslation()` to fall back to
+`LanguageCache::defaultLocale()` instead — the same `languages.default` flag `LocaleMiddleware`
+already treats as the single source of truth. It's swapped in via
+`config('translation-loader.model')` (the package's own documented extension point for
+"any model that extends `LanguageLine`"), set in `LocalizationServiceProvider::register()` so it
+wins regardless of provider boot order (Laravel's `mergeConfigFrom()` only fills in config keys
+not already set, so an explicit `register()`-time set always beats the package's own default).
+No consuming app configuration needed — this is automatic once `LocalizationServiceProvider` is
+registered.
+
 ### Seeding
 
 A starter set of common e-shop labels (`nav.*`, `cart.*`, `product.*`, `auth.*`, `search.*`,

src/Localization/Models/LanguageLine.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace Modules\Core\Localization\Models;
+
+use Modules\Core\Localization\Services\LanguageCache;
+use Spatie\TranslationLoader\LanguageLine as BaseLanguageLine;
+
+/**
+ * Overrides the base package's locale fallback (config('app.fallback_locale'), a
+ * static .env value) with the store's actual default language — Lunar's
+ * `languages.default` flag, the same source LocaleMiddleware/LanguageCache already
+ * treat as the single source of truth for "this store's default language".
+ *
+ * Without this, changing the default language via the Filament Languages resource
+ * has no effect on which locale an untranslated storefront label falls back to —
+ * two disconnected "default locale" concepts silently drifting apart. Swapped in
+ * via config('translation-loader.model') (see LocalizationServiceProvider), the
+ * package's own documented extension point for this.
+ */
+class LanguageLine extends BaseLanguageLine
+{
+    public function getTranslation(string $locale): ?string
+    {
+        if (isset($this->text[$locale])) {
+            return $this->text[$locale];
+        }
+
+        $fallback = app(LanguageCache::class)->defaultLocale();
+
+        return $fallback !== null ? ($this->text[$fallback] ?? null) : null;
+    }
+}

src/Providers/LocalizationServiceProvider.php

@@ -16,10 +16,21 @@ use Modules\Core\Localization\Listeners\FlushTranslationCache;
 use Modules\Core\Localization\Listeners\LogTranslationActivity;
 use Modules\Core\Localization\Listeners\MigrateTranslationsForRenamedLanguage;
 use Modules\Core\Localization\Middleware\LocaleMiddleware;
+use Modules\Core\Localization\Models\LanguageLine;
 use Modules\Core\Localization\Observers\LanguageCacheObserver;
 
 class LocalizationServiceProvider extends ServiceProvider
 {
+    public function register(): void
+    {
+        // Must run before Spatie\TranslationLoader\TranslationServiceProvider's
+        // register() merges its own config defaults - mergeConfigFrom() only fills
+        // in keys not already set, so setting this here (regardless of provider
+        // boot order) makes it win over the package's default
+        // Spatie\TranslationLoader\LanguageLine::class.
+        config(['translation-loader.model' => LanguageLine::class]);
+    }
+
     public function boot(): void
     {
         $this->app['router']->aliasMiddleware('locale', LocaleMiddleware::class);