diff --git a/app/Http/Middleware/TrustHosts.php b/app/Http/Middleware/TrustHosts.php
index f0b9d67f2..5fca583d9 100644
--- a/app/Http/Middleware/TrustHosts.php
+++ b/app/Http/Middleware/TrustHosts.php
@@ -91,6 +91,13 @@ public function hosts(): array
         // Trust all subdomains of APP_URL as fallback
         $trustedHosts[] = $this->allSubdomainsOfApplicationUrl();
 
+        // Always trust loopback addresses so local access works even when FQDN is configured
+        foreach (['localhost', '127.0.0.1', '[::1]'] as $localHost) {
+            if (! in_array($localHost, $trustedHosts, true)) {
+                $trustedHosts[] = $localHost;
+            }
+        }
+
         return array_filter($trustedHosts);
     }
 }
diff --git a/resources/views/errors/419.blade.php b/resources/views/errors/419.blade.php
index 8569f4e22..70b5d7a92 100644
--- a/resources/views/errors/419.blade.php
+++ b/resources/views/errors/419.blade.php
@@ -5,7 +5,15 @@
         <h1 class="mt-4 font-bold tracking-tight dark:text-white">This page is definitely old, not like you!</h1>
         <p class="text-base leading-7 dark:text-neutral-300 text-black">Your session has expired. Please log in again to continue.
         </p>
-        <div class="flex items-center mt-10 gap-x-2">
+        <details class="mt-6 text-sm dark:text-neutral-400 text-neutral-600">
+            <summary class="cursor-pointer hover:dark:text-neutral-200 hover:text-neutral-800">Using a reverse proxy or Cloudflare Tunnel?</summary>
+            <ul class="mt-2 ml-4 list-disc space-y-1">
+                <li>Set your domain in <strong>Settings &rarr; FQDN</strong> to match the URL you use to access Coolify.</li>
+                <li>Cloudflare users: disable <strong>Browser Integrity Check</strong> and <strong>Under Attack Mode</strong> for your Coolify domain, as these can interrupt login sessions.</li>
+                <li>If you can still access Coolify via <code>localhost</code>, log in there first to configure your FQDN.</li>
+            </ul>
+        </details>
+        <div class="flex items-center mt-6 gap-x-2">
             <a href="/login">
                 <x-forms.button>Back to Login</x-forms.button>
             </a>
diff --git a/tests/Feature/TrustHostsMiddlewareTest.php b/tests/Feature/TrustHostsMiddlewareTest.php
index b745259fe..5c60b30d6 100644
--- a/tests/Feature/TrustHostsMiddlewareTest.php
+++ b/tests/Feature/TrustHostsMiddlewareTest.php
@@ -286,6 +286,56 @@
     expect($response->status())->not->toBe(400);
 });
 
+it('trusts localhost when FQDN is configured', function () {
+    InstanceSettings::updateOrCreate(
+        ['id' => 0],
+        ['fqdn' => 'https://coolify.example.com']
+    );
+
+    $middleware = new TrustHosts($this->app);
+    $hosts = $middleware->hosts();
+
+    expect($hosts)->toContain('localhost');
+});
+
+it('trusts 127.0.0.1 when FQDN is configured', function () {
+    InstanceSettings::updateOrCreate(
+        ['id' => 0],
+        ['fqdn' => 'https://coolify.example.com']
+    );
+
+    $middleware = new TrustHosts($this->app);
+    $hosts = $middleware->hosts();
+
+    expect($hosts)->toContain('127.0.0.1');
+});
+
+it('trusts IPv6 loopback when FQDN is configured', function () {
+    InstanceSettings::updateOrCreate(
+        ['id' => 0],
+        ['fqdn' => 'https://coolify.example.com']
+    );
+
+    $middleware = new TrustHosts($this->app);
+    $hosts = $middleware->hosts();
+
+    expect($hosts)->toContain('[::1]');
+});
+
+it('allows local access via localhost when FQDN is configured and request uses localhost host header', function () {
+    InstanceSettings::updateOrCreate(
+        ['id' => 0],
+        ['fqdn' => 'https://coolify.example.com']
+    );
+
+    $response = $this->get('/', [
+        'Host' => 'localhost',
+    ]);
+
+    // Should NOT be rejected as untrusted host (would be 400)
+    expect($response->status())->not->toBe(400);
+});
+
 it('skips host validation for webhook endpoints', function () {
     // All webhook routes are under /webhooks/* prefix (see RouteServiceProvider)
     // and use cryptographic signature validation instead of host validation