CDI BeanManager (WeldBeanManagerServiceProcessor) needs to be created during Phase.FIRST_MODULE_USE for applications that have JPA classes that are rewritten/enhanced during deployment

The JPA deployment subsystem, needs to pass a (deployment) CDI bean manager instance into the persistence provider, when creating the (container) entity manager factory.

If JPA detects that classfile enhancing might be needed for the persistence units classes, the entity manager factory is created during the Phase.FIRST_MODULE_USE phase (so that JPA transformers can be registered before any deployer accesses the deployment classloader).

If JPA classfile rewriting is not needed, the entity manager factory is created during the Phase.INSTALL phase.