So the plan is now to update public interfaces in trunk so that 3.x will be API compatible with 2.x (which means in can be used in AS 5). Now the 1.x compat thing is a somewhat different kettle of fish - and I'm still exploring solutions. Have you considered using JarJar to move the package names of org.jboss.cache to org.jboss.cache.2 so it doesn't clash with jars shipped in AS 4.x? If this works successfully, we should use this as the recommended pattern as it would then allow AS 4 to use JBC 1.x internally, and 2.x or 3.x code in your apps. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4172141#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...