For the record, my last post was wrong about app thread carrying a message back up the stack if loopback=true. Rather, it creates a task and hands it off to the transport protocol's thread pool. So, the app TCCL can leak to the transport protocol thread pool as well. Removing the multiplexer still left that problem. I'm fixing this for the AS by having the AS channel factory inject specialized thread pools into the channel that properly control the TCCL on pool threads, like what I did for JBCOMMON-41. http://jira.jboss.com/jira/browse/JBAS-5414 View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4143651#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...