I tried deploying WELD 1.0 CR1 to Google App Engine and got the following stack trace. I suspect that this is probably due to the fact that AbstractConversationManager does not implement Serializable, hence when ServletConversationManager is serialized/deserialized with the HttpSession, none of the fields on AbstractConversationManager is restored. This meant that when cleanupConversation was invoked, the 'currentConversation' field was null.

com.sun.faces.lifecycle.Phase handleAfterPhase: JSF1053: (Listener: org.jboss.weld.jsf.WeldPhaseListener.afterPhase(), Phase ID: RENDER_RESPONSE 6, View ID: /home.xhtml) Exception thrown during phase-listener execution: java.lang.NullPointerException
com.sun.faces.lifecycle.Phase handleAfterPhase: org.jboss.weld.conversation.AbstractConversationManager.cleanupConversation(AbstractConversationManager.java:132)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
java.lang.reflect.Method.invoke(Method.java:40)
org.jboss.weld.bean.proxy.ClientProxyMethodHandler.invoke(ClientProxyMethodHandler.java:111)
org.jboss.weld.examples.numberguess.ServletConversationManager_$$javassist_1.cleanupConversation(ServletConversationManager$$_javassist_1.java)
org.jboss.weld.jsf.WeldPhaseListener.afterRenderResponse(WeldPhaseListener.java:128)
org.jboss.weld.jsf.WeldPhaseListener.afterPhase(WeldPhaseListener.java:99)
com.sun.faces.lifecycle.Phase.handleAfterPhase(Phase.java:175)
com.sun.faces.lifecycle.Phase.doPhase(Phase.java:114)
com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139)
javax.faces.webapp.FacesServlet.service(FacesServlet.java:266)
org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487)
org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1093)
com.google.apphosting.runtime.jetty.SaveSessionFilter.doFilter(SaveSessionFilter.java:35)
org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084)
com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084)
org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:360)
org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181)
org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:712)
org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405)
com.google.apphosting.runtime.jetty.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:238)
org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:139)
org.mortbay.jetty.Server.handle(Server.java:313)