diff --git a/app/apps/api/tests/test_demo_mode.py b/app/apps/api/tests/test_demo_mode.py
new file mode 100644
index 0000000..e25e232
--- /dev/null
+++ b/app/apps/api/tests/test_demo_mode.py
@@ -0,0 +1,155 @@
+from datetime import timedelta
+
+from django.contrib.auth import get_user_model
+from django.test import TestCase, override_settings
+from django.urls import reverse
+from django.utils import timezone
+from oauth2_provider.models import get_access_token_model, get_application_model
+
+from apps.users.models import APIToken
+
+User = get_user_model()
+Application = get_application_model()
+AccessToken = get_access_token_model()
+
+
+@override_settings(DEMO=True)
+class DemoModeAPITests(TestCase):
+    """The DEMO-mode gate (apps.api.permissions.NotInDemoMode) must reject
+    API access regardless of the authentication method used, including the
+    PAT and OAuth2 backends introduced for MCP integrations."""
+
+    def setUp(self):
+        self.user = User.objects.create_user(
+            email="demo@example.com",
+            password="test-password",
+        )
+
+    def test_pat_cannot_access_api_in_demo_mode(self):
+        _token, raw_token = APIToken.objects.create_token(
+            user=self.user, name="n8n"
+        )
+
+        response = self.client.get(
+            "/api/accounts/",
+            HTTP_AUTHORIZATION=f"Token {raw_token}",
+        )
+
+        self.assertEqual(response.status_code, 403)
+
+    def test_oauth_access_token_cannot_access_api_in_demo_mode(self):
+        app = Application.objects.create(
+            name="Test Client",
+            client_type=Application.CLIENT_CONFIDENTIAL,
+            authorization_grant_type=Application.GRANT_AUTHORIZATION_CODE,
+            redirect_uris="http://127.0.0.1:8765/callback",
+            client_secret="secret",
+        )
+        access_token = AccessToken.objects.create(
+            user=self.user,
+            scope="mcp",
+            expires=timezone.now() + timedelta(hours=1),
+            token="demo-oauth-access-token-xyz",
+            application=app,
+        )
+
+        response = self.client.get(
+            "/api/accounts/",
+            HTTP_AUTHORIZATION=f"Bearer {access_token.token}",
+        )
+
+        self.assertEqual(response.status_code, 403)
+
+    def test_superuser_pat_can_access_api_in_demo_mode(self):
+        admin = User.objects.create_superuser(
+            email="admin@example.com",
+            password="test-password",
+        )
+        _token, raw_token = APIToken.objects.create_token(
+            user=admin, name="admin"
+        )
+
+        response = self.client.get(
+            "/api/accounts/",
+            HTTP_AUTHORIZATION=f"Token {raw_token}",
+        )
+
+        # NotInDemoMode grants superusers access in DEMO mode; the request is
+        # authenticated by the PAT, so the API responds normally (never 403).
+        self.assertNotEqual(response.status_code, 403)
+
+
+@override_settings(DEMO=True)
+class DemoModeOAuthEndpointTests(TestCase):
+    """OAuth2 issuance and discovery endpoints must be disabled in DEMO mode
+    so demo tenants cannot obtain (or even discover) credentials."""
+
+    def setUp(self):
+        self.user = User.objects.create_user(
+            email="demo@example.com",
+            password="test-password",
+        )
+
+    def test_oauth_authorize_rejects_non_superuser_in_demo_mode(self):
+        self.client.force_login(self.user)
+
+        response = self.client.get(reverse("oauth2_provider:authorize"))
+
+        self.assertEqual(response.status_code, 403)
+
+    def test_oauth_token_rejects_non_superuser_in_demo_mode(self):
+        self.client.force_login(self.user)
+
+        response = self.client.post(reverse("oauth2_provider:token"))
+
+        self.assertEqual(response.status_code, 403)
+
+    def test_oauth_authorization_server_metadata_rejects_in_demo_mode(self):
+        response = self.client.get(reverse("oauth-authorization-server-metadata"))
+
+        self.assertEqual(response.status_code, 403)
+
+    def test_oauth_dynamic_client_registration_rejects_in_demo_mode(self):
+        response = self.client.post(
+            reverse("oauth-dynamic-client-registration"),
+            data="{}",
+            content_type="application/json",
+        )
+
+        self.assertEqual(response.status_code, 403)
+
+
+@override_settings(DEMO=True)
+class DemoModeAPITokenViewsTests(TestCase):
+    """The PAT management UI must be disabled in DEMO mode just like the
+    other mutating user views."""
+
+    def setUp(self):
+        self.user = User.objects.create_user(
+            email="demo@example.com",
+            password="test-password",
+        )
+        self.client.force_login(self.user)
+        self.htmx_headers = {"HTTP_HX_REQUEST": "true"}
+
+    def test_cannot_create_api_token_from_ui_in_demo_mode(self):
+        response = self.client.post(
+            reverse("user_api_token_add"),
+            {"name": "n8n", "expires_in_days": "30"},
+            **self.htmx_headers,
+        )
+
+        self.assertEqual(response.status_code, 403)
+        self.assertEqual(APIToken.objects.count(), 0)
+
+    def test_cannot_revoke_api_token_from_ui_in_demo_mode(self):
+        token, _ = APIToken.objects.create_token(user=self.user, name="n8n")
+
+        response = self.client.delete(
+            reverse("user_api_token_revoke", kwargs={"token_id": token.id}),
+            **self.htmx_headers,
+        )
+
+        self.assertEqual(response.status_code, 403)
+        token.refresh_from_db()
+        self.assertIsNone(token.revoked_at)
\ No newline at end of file
diff --git a/app/templates/layouts/base.html b/app/templates/layouts/base.html
index fbb5c13..8b8368d 100644
--- a/app/templates/layouts/base.html
+++ b/app/templates/layouts/base.html
@@ -34,8 +34,7 @@
       {% if demo_mode %}
       <div class="px-3 m-0" id="demo-mode-alert" hx-preserve>
         <div class="alert alert-warning my-3 relative" role="alert">
-          <strong>{% trans "This is a demo!" %}</strong> {% trans "Any data you add here will be wiped in 24hrs or less"
-          %}
+          <strong>{% trans "This is a demo!" %}</strong>{% trans "Any data you add here will be wiped in 24hrs or less" %}
           <button type="button" class="btn btn-sm btn-ghost absolute right-2 top-1/2 -translate-y-1/2"
             onclick="this.parentElement.style.display='none'" aria-label="Close">✕</button>
         </div>
@@ -54,4 +53,4 @@
   {% endblock extra_js_body %}
 </body>
 
-</html>
\ No newline at end of file
+</html>