it's the responsibility of an integrator to load the extensions and pass the set to the Weld Bootstrap API, either as a param of
org.jboss.weld.bootstrap.api.CDI11Bootstrap.startExtensions()or as a part of the deployment -
org.jboss.weld.bootstrap.spi.Deployment.getExtensions(). So it's probably not a Weld issue. You should check the Payara integration code. Also I'm not sure how HK2 is related (AFAIK it's used as an internal DI solution in Payara/GlassFish).
This was related to HK2 since with version 2.5.0 they gave up bundling hibernate validator as an OSGI'fied artifact and directly depend on the hibernate-validator artifacts instead. And the problem was with the hibernate-validator-cdi artifact since it was not OSGI'fied that is it was not containing import-export package definitions in its MANIFEST files. I filed a bug for that and hibernate guys fixed that.
Thanks for the response.