By default a Portlet Render Response will execute the full Faces Lifecycle before rendering the portlet content to be returned.

It's possible to disable this behavior by specifying the following context param in web.xml:

<context-param>
  <param-name>org.jboss.portletbridge.VIEW_PARAMETERS_DISABLED</param-name>
  <param-value>true</param-value>
</context-param>