What do you want to achive with NOT_SUPPORTED as a default? If you want to simply prevent flushing of the persistence context, a much better approach is a Seam-managed PC with FlushModeType.MANUAL. The EJB3 spec mixes these concerns together and ties flushing to transactions. This is a major issue with the spec that hopefully will be fixed in the next revision.
Yes, I want to prevent flushing of the persistence context. I will give Seam-managed PC a try.
But this raises another question. I am leaning towards keeping all entities objects contained in sfsbs rather than outjecting them into the conversation scope. If the sfsb is passivated, will the entity be detached from the seam-managed PC?