Yeah, I don't mind that so much; just the way it is. But, the interface that exposes the new invocation model is going to have to extend the interface that uses the old model, which is ugly. Otherwise we break older clients. The LoadBalancePolicy is an instance field in the 4.x EJB3 StatefulClusteredProxy and StatelessClusteredProxy; change the type of the field and serialization will break. Hmm; will it? If the policy actually serialized with the proxy implements the old interface, will old clients be able to deserialize it? I'll have to test. Unfortunately the proxies don't implement Externalizable; if they did for sure it would work. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4092154#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...