A Request context should be available in @PostConstruct methods of EJB Singletons.
This is a completion of section 6.7.1 of the CDI 1.0 spec, which covers @Asynchronous and @Timeout EJB methods.
Probably the container should ensure that a new context is always created for the @PostConstruct invocation, to be coherent with section 4.8.3 of the EJB 3.1 spec, which specifies the transactional behavior of @Singleton @PostConstruct.