Resteasy considers all javax.ws.rs.ext.ContextResolver classes are builtin. ResteasyProviderFactory hardcodes true for the builtin parameter and does not propagate the isBuiltin input parameter.

Because of this, it is impossible to override default context resolvers by user-defined ones.

https://github.com/resteasy/Resteasy/blob/cfeb425cc6339ba575bf32e239c72998d671c4f9/resteasy-jaxrs/src/main/java/org/jboss/resteasy/spi/ResteasyProviderFactory.java#L1337