diff --git a/llama_stack/distribution/server/auth.py b/llama_stack/distribution/server/auth.py
index 12e342c92..52e6a013c 100644
--- a/llama_stack/distribution/server/auth.py
+++ b/llama_stack/distribution/server/auth.py
@@ -172,8 +172,10 @@ class AuthenticationMiddleware:
                         if auth_response.access_attributes:
                             user_attributes = auth_response.access_attributes.model_dump(exclude_none=True)
                         else:
-                            logger.warning("Authentication response did not contain any attributes")
-                            user_attributes = {}
+                            logger.warning("No access attributes, setting namespace to api_key by default")
+                            user_attributes = {
+                                "namespaces": [api_key],
+                            }
 
                         scope["user_attributes"] = user_attributes
                         logger.debug(f"Authentication successful: {len(user_attributes)} attributes")
diff --git a/tests/unit/server/test_auth.py b/tests/unit/server/test_auth.py
index b078448a2..5e93719d2 100644
--- a/tests/unit/server/test_auth.py
+++ b/tests/unit/server/test_auth.py
@@ -201,4 +201,6 @@ async def test_auth_middleware_no_attributes(mock_middleware, mock_scope):
         await middleware(mock_scope, mock_receive, mock_send)
 
         assert "user_attributes" in mock_scope
-        assert mock_scope["user_attributes"] == {}
+        attributes = mock_scope["user_attributes"]
+        assert "namespaces" in attributes
+        assert attributes["namespaces"] == ["test-api-key"]