add custom error handling for host mismatch; ensure TrustHosts runs

before TrustProxies

app/Exceptions/Handler.php

@@ -6,7 +6,10 @@ namespace App\Exceptions;
 
 use Illuminate\Foundation\Exceptions\Handler as ExceptionHandler;
 use Illuminate\Http\RedirectResponse;
+use Illuminate\Http\Request;
+use Symfony\Component\HttpFoundation\Exception\SuspiciousOperationException;
 use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\HttpKernel\Exception\BadRequestHttpException;
 use Throwable;
 
 class Handler extends ExceptionHandler
@@ -30,6 +33,29 @@ class Handler extends ExceptionHandler
         $this->reportable(function (Throwable $e): void {
             //
         });
+
+        // A request on an untrusted host (see App\Http\Middleware\TrustHosts)
+        // otherwise renders as a bare "Bad request." 400. Show a message that
+        // says how to fix it instead. The framework has already converted the
+        // SuspiciousOperationException into a BadRequestHttpException by the time
+        // renderables run, so we match that and inspect the original.
+        $this->renderable(function (BadRequestHttpException $e, Request $request): ?Response {
+            $previous = $e->getPrevious();
+
+            if (! $previous instanceof SuspiciousOperationException
+                || ! str_starts_with($previous->getMessage(), 'Untrusted Host')) {
+                return null; // any other bad request keeps the default response
+            }
+
+            $message = 'This hostname is not configured for this instance. '
+                .'Set APP_URL, or add the host to TRUSTED_HOSTS.';
+
+            if ($request->expectsJson()) {
+                return response()->json(['message' => $message], 400);
+            }
+
+            return response()->view('errors.untrusted-host', ['message' => $message], 400);
+        });
     }
 
     public function render($request, Throwable $e): Response|RedirectResponse

app/Http/Kernel.php

@@ -48,8 +48,8 @@ class Kernel extends HttpKernel
      */
     protected $middleware = [
         ForceHttps::class,
-        TrustProxies::class,
         TrustHosts::class,
+        TrustProxies::class,
         HandleCors::class,
         PreventRequestsDuringMaintenance::class,
         ValidatePostSize::class,