Simply merging the maps probably isn't the correct solution, since the jsf resource's url could include the conversation id. In this case, Weld would create a new conversation with the same id. It shouldn't do that, of course.

Creating the session also isn't correct, since Weld should be transparent to the app (it should change the behavior - i.e. should not create sessions).

The right thing to do is make sure that immediately when the session is created, the conversation map (and conversation id generator) are stored in the session.