diff --git a/app/Http/Middleware/SetLocale.php b/app/Http/Middleware/SetLocale.php
index 2242bbf..131df53 100644
--- a/app/Http/Middleware/SetLocale.php
+++ b/app/Http/Middleware/SetLocale.php
@@ -18,14 +18,30 @@ class SetLocale
 
     public function handle(Request $request, Closure $next): Response
     {
-        $locale = $request->user()?->locale
-            ?? $request->session()->get('locale')
-            ?? config('app.locale');
+        self::apply($request);
+
+        return $next($request);
+    }
+
+    /**
+     * Resolve + set the active locale: signed-in user's preference, then the session
+     * choice, then the app default. Safe to call before the session is started — e.g.
+     * from the exception handler for errors thrown before this middleware (CSRF 419,
+     * unmatched-route 404, maintenance 503) — a missing session is simply skipped, so
+     * those custom error pages still honour the user's language where it is known.
+     */
+    public static function apply(Request $request): void
+    {
+        $locale = config('app.locale');
+
+        if ($request->hasSession()) {
+            $locale = $request->user()?->locale
+                ?? $request->session()->get('locale')
+                ?? $locale;
+        }
 
         if (in_array($locale, self::SUPPORTED, true)) {
             app()->setLocale($locale);
         }
-
-        return $next($request);
     }
 }
diff --git a/bootstrap/app.php b/bootstrap/app.php
index f56377f..912fa3f 100644
--- a/bootstrap/app.php
+++ b/bootstrap/app.php
@@ -42,4 +42,15 @@ return Application::configure(basePath: dirname(__DIR__))
         $exceptions->shouldRenderJsonWhen(
             fn (Request $request) => $request->is('api/*'),
         );
+
+        // Errors thrown BEFORE the web-group SetLocale middleware (CSRF 419, an
+        // unmatched-route 404, maintenance 503) would render the custom error page in
+        // the default locale. Resolve the user's language first so those pages honour
+        // it too (R16); returning null falls through to the normal renderer (the
+        // resources/views/errors/* views).
+        $exceptions->render(function (Throwable $e, Request $request) {
+            SetLocale::apply($request);
+
+            return null;
+        });
     })->create();