fix: language switcher stuck in French on store dashboard

Three compounding bugs prevented language switching on the store dashboard:
- Cookie missing path="/", scoping it to the API endpoint path only
- STORE frontend resolution chain ignored the cookie entirely
- Store header used inline x-data with wrong language names instead of shared languageSelector()

Also updates architecture doc with correct per-frontend resolution priorities,
cookie name, API endpoint path, and file references.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/templates/store/partials/header.html

@@ -37,33 +37,7 @@
             </li>
 
             <!-- Language selector -->
-            <li class="relative" x-data="{
-                isLangOpen: false,
-                currentLang: '{{ request.state.language|default("fr") }}',
-                languages: ['en', 'fr', 'de', 'lb'],
-                languageNames: { 'en': 'English', 'fr': 'Francais', 'de': 'Deutsch', 'lb': 'Letzebuerg' },
-                languageFlags: { 'en': 'gb', 'fr': 'fr', 'de': 'de', 'lb': 'lu' },
-                async setLanguage(lang) {
-                    if (lang === this.currentLang) {
-                        this.isLangOpen = false;
-                        return;
-                    }
-                    try {
-                        const response = await fetch('/api/v1/platform/language/set', {
-                            method: 'POST',
-                            headers: { 'Content-Type': 'application/json' },
-                            body: JSON.stringify({ language: lang })
-                        });
-                        if (response.ok) {
-                            this.currentLang = lang;
-                            window.location.reload();
-                        }
-                    } catch (error) {
-                        console.error('Failed to set language:', error);
-                    }
-                    this.isLangOpen = false;
-                }
-            }">
+            <li class="relative" x-data="languageSelector('{{ request.state.language|default('fr') }}')">
                 <button
                     @click="isLangOpen = !isLangOpen"
                     @click.outside="isLangOpen = false"
@@ -179,4 +153,4 @@
             </li>
         </ul>
     </div>
-</header>
+</header>

app/utils/i18n.py

@@ -351,15 +351,20 @@ def get_jinja2_globals(language: str = None) -> dict:
 def resolve_store_dashboard_language(
     user_preferred: str | None,
     store_dashboard: str | None,
+    cookie_language: str | None = None,
 ) -> str:
     """
     Resolve language for store dashboard.
 
     Priority:
-    1. User's preferred_language (if set)
-    2. Store's dashboard_language
-    3. System default (fr)
+    1. Cookie (explicit UI action via language switcher)
+    2. User's preferred_language (DB preference from profile settings)
+    3. Store's dashboard_language
+    4. System default (fr)
     """
+    if cookie_language and cookie_language in SUPPORTED_LANGUAGES:
+        return cookie_language
+
     if user_preferred and user_preferred in SUPPORTED_LANGUAGES:
         return user_preferred
 

docs/architecture/language-i18n.md

@@ -44,18 +44,20 @@ language = "lux"      # ❌ Use "lb"
 
 ## Language Context Flow
 
-### Resolution Priority
+### Resolution Priority (per Frontend Type)
 
-Language is resolved in this order (highest to lowest priority):
+Language resolution varies by frontend type. Each chain is evaluated top-to-bottom, first match wins:
 
-1. **URL parameter** (`?lang=fr`)
-2. **Cookie** (`orion_language`)
-3. **User preference** (database: `preferred_language`)
-4. **Store default** (database: `storefront_language` or `dashboard_language`)
-5. **Accept-Language header** (browser)
-6. **Platform default** (`fr`)
+| Frontend | Priority (highest → lowest) |
+|----------|----------------------------|
+| **ADMIN** | User `preferred_language` → `"en"` |
+| **STORE** | Cookie (`lang`) → User `preferred_language` → Store `dashboard_language` → `"fr"` |
+| **STOREFRONT** | Customer `preferred_language` → Cookie (`lang`) → Store `storefront_language` → Browser `Accept-Language` → `"fr"` |
+| **PLATFORM** | Cookie (`lang`) → Browser `Accept-Language` → `"fr"` |
 
-### Store Dashboard vs Storefront
+The **cookie** (`lang`) is set by the language switcher UI via `POST /api/v1/platform/language/set` and represents the user's most recent explicit language choice. It takes priority over database preferences because it reflects an immediate UI action.
+
+### Database Fields
 
 | Context | Language Source | Database Field |
 |---------|-----------------|----------------|
@@ -210,7 +212,7 @@ function languageSelector(currentLang, enabledLanguages) {
                 return;
             }
             try {
-                const response = await fetch('/api/v1/language/set', {
+                const response = await fetch('/api/v1/platform/language/set', {
                     method: 'POST',
                     headers: { 'Content-Type': 'application/json' },
                     body: JSON.stringify({ language: lang })
@@ -270,11 +272,12 @@ async def set_language(request: LanguageSetRequest, response: Response):
         raise HTTPException(status_code=400, detail="Unsupported language")
 
     response.set_cookie(
-        key="orion_language",
+        key="lang",
         value=request.language,
         max_age=365 * 24 * 60 * 60,  # 1 year
-        httponly=True,
-        samesite="lax"
+        httponly=False,  # Accessible to JavaScript
+        samesite="lax",
+        path="/",  # Must be site-wide
     )
     return {"success": True, "language": request.language}
 ```
@@ -379,16 +382,16 @@ languageFlags: {
 
 ```javascript
 // ✅ GOOD: Correct endpoint
-fetch('/api/v1/language/set', {
+fetch('/api/v1/platform/language/set', {
     method: 'POST',
     headers: { 'Content-Type': 'application/json' },
     body: JSON.stringify({ language: lang })
 });
 
 // ❌ BAD: Wrong endpoint or method
-fetch('/api/language/set', ...);     // ❌ Missing /v1
-fetch('/api/v1/language', ...);      // ❌ Missing /set
-fetch('/api/v1/language/set', { method: 'GET' });  // ❌ Should be POST
+fetch('/api/v1/language/set', ...);     // ❌ Missing /platform
+fetch('/api/v1/platform/language', ...);      // ❌ Missing /set
+fetch('/api/v1/platform/language/set', { method: 'GET' });  // ❌ Should be POST
 ```
 
 ---
@@ -467,7 +470,7 @@ static/locales/
 - [ ] Provides default values for both parameters
 - [ ] Uses native language names (Français, Deutsch, Lëtzebuergesch)
 - [ ] Uses correct flag codes (en→gb, fr→fr, de→de, lb→lu)
-- [ ] Calls `/api/v1/language/set` with POST method
+- [ ] Calls `/api/v1/platform/language/set` with POST method
 - [ ] Reloads page after successful language change
 - [ ] Hides selector if only one language enabled (storefront)
 - [ ] Shows all languages (store dashboard)
@@ -491,7 +494,7 @@ static/locales/
 | `static/store/js/init-alpine.js` | JS | `languageSelector()` function |
 | `app/templates/shop/base.html` | Template | Storefront language selector |
 | `app/templates/store/partials/header.html` | Template | Dashboard language selector |
-| `app/api/v1/shared/language.py` | API | Language endpoints |
+| `app/modules/core/routes/api/platform.py` | API | Language endpoints (`/api/v1/platform/language/*`) |
 | `middleware/language.py` | Middleware | Language detection |
 | `static/locales/*.json` | JSON | Translation files |
 

middleware/language.py

@@ -73,6 +73,7 @@ class LanguageMiddleware(BaseHTTPMiddleware):
             language = resolve_store_dashboard_language(
                 user_preferred=user_preferred,
                 store_dashboard=store_dashboard,
+                cookie_language=cookie_language,
             )
 
         elif frontend_type == FrontendType.STOREFRONT:
@@ -170,6 +171,7 @@ def set_language_cookie(response: Response, language: str) -> Response:
             max_age=60 * 60 * 24 * 365,  # 1 year
             httponly=False,  # Accessible to JavaScript
             samesite="lax",
+            path="/",
         )
     return response
 
@@ -184,5 +186,5 @@ def delete_language_cookie(response: Response) -> Response:
     Returns:
         Modified response with cookie deleted
     """
-    response.delete_cookie(key=LANGUAGE_COOKIE_NAME)
+    response.delete_cookie(key=LANGUAGE_COOKIE_NAME, path="/")
     return response