Fix: Correcting Language Line fallback resolver

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);