Oliver, Dropping insuring compatibility is a decision that we reluctantly took after we evaluated our resources and polled the community (http://www.jboss.com/index.html?module=bb&op=viewtopic&t=85729). Given the pace at which the code changes on the head, it is simply not feasible to maintain backward compatibility through all intermediate changes until 1.2.GA. Technically, it can done, the wire format has built-in support for it, but then we would have had to delay the delivery of 1.2, and since there are a lot of people who are waiting for clustering, we decided to temporarily drop the requirement. The framework for testing backward/forward compatibility exists (take a look at tests/smoke/build.xml) and it was integrated within the release procedure, it is just temporarily disabled now. We will be back at guaranteeing compatibility starting with 1.2.GA. We do apologize for any inconvenience this may caused you. If you have a support contract with us, and you already have production clients deployed, we could evaluate what it implies to restore server compatibility in your specific case, as part of a consulting engagement. If you are interested, we can continue this discussion off-line. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3976157#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...