After all there is something weird happening that isn't my fault ;) I thing there is some problem with the method executeAction in org.jbpm.graph.def.GraphElement when an exception is thrown. If you trace the execution you will see that the exception arriving to the code doing the signals has the field messageDetail empty which means that somehow the method executeAction is clearing it. The only to reach the exception message generated in the action exception is doing: e.getCause().getMessage(); I think this is a bug! View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4002340#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...