...

public class CustomService2
{
    @Inject
    @Users
    protected EntityManager entityManager;

    @Transactional(Users.class)
    public void update(CustomEntity2 entity)
    {
        this.entityManager.merge(entity);
    }
}

...

Extended Persistence Contexts

MyFaces Orchestra provides a feature which allows keeping an EntityManager across multiple requests. That means it isn't required to call EntityManager#merge to add detached entities to the context. However, several application architectures don't allow such an approach (due to different reasons like scalability). Seam3 still does that. In theory that sounds nice and it works pretty well for small to medium sized projects esp. if an application doesn't rely on session replication in clusters. That also means that such an approach restricts your target environment from the very beginning. One of the base problems is that an EntityManager isn't serializable. Beans which are scoped in a normalscoped CDI context have to be serializable. So by default it isn't allowed by CDI to provide a producer-method which exposes e.g. a conversation scoped EntityManager as it is. We don't recommend to use this approach and therefore it isn't available out-of-the-box. However, if you really need this approach to avoid calling #merge for your detached entities, it's pretty simple to add this functionality.

@Inject
protected EntityManager entityManager;

As you see the usage is the same. You don't have to use ExtendedEntityManager at your injection point. It's just needed in the producer-method:

public class EntityManagerProducer
{
    @PersistenceContext(unitName = "demoPU")
    private EntityManager entityManager;

    @Produces
    @Default
    @ConversationScoped
    public ExtendedEntityManager create()
    {
        return new ExtendedEntityManager(this.entityManager);
    }

    public void dispose(@Disposes @Default ExtendedEntityManager entityManager)
    {
        if(entityManager.isOpen())
        {
            entityManager.close();
        }
    }
}

@Typed()
class ExtendedEntityManager implements EntityManager, Serializable
{
    private static final long serialVersionUID = 3770954229283539616L;

    private transient EntityManager wrapped;

    protected ExtendedEntityManager()
    {
    }

    public ExtendedEntityManager(EntityManager wrapped)
    {
        this.wrapped = wrapped;
        this.persistenceUnitName = persistenceUnitName;
    }

    /*
     * generated
     */
     //delegate all calls to this.wrapped - most IDEs allow to generate it

This approach just works if it doesn't come to serialization of this wrapper e.g. in case of session-replication.
If those beans get serialized, you have to overcome this restriction by storing the persistence-unit-name and recreate the EntityManager via Persistence.createEntityManagerFactory(this.persistenceUnitName).createEntityManager(); btw. sync it with the database before closing it on serialization. Furthermore, you have to intercept some methods of the EntityManager to merge detached entities automatically if those entities get serialized as well. However, as mentioned before we don't recommend such an approach.