The following code:

@Specializes
public class User2 extends User {}

results in this exception in the SE extension. User is definitely recognized as a bean.

Exception in thread "main" org.jboss.weld.DefinitionException: WELD-000047 Specializing bean must extend another bean\: org.jboss.weld.bean-se-module-ManagedBean-class setest.User2
at org.jboss.weld.bean.ManagedBean.specialize(ManagedBean.java:431)
at org.jboss.weld.bean.AbstractBean.initialize(AbstractBean.java:140)
at org.jboss.weld.bean.AbstractClassBean.initialize(AbstractClassBean.java:146)
at org.jboss.weld.bean.ManagedBean.initialize(ManagedBean.java:199)
at org.jboss.weld.bootstrap.AbstractBeanDeployer.deploy(AbstractBeanDeployer.java:111)
at org.jboss.weld.bootstrap.BeanDeployment.deployBeans(BeanDeployment.java:151)
at org.jboss.weld.bootstrap.WeldBootstrap.deployBeans(WeldBootstrap.java:367)
at org.jboss.weld.environment.se.StartMain.go(StartMain.java:73)
at org.jboss.weld.environment.se.StartMain.main(StartMain.java:89)