The RESTEasy client API allows for interface methods to be proxies. This is similar to the MicroProfile REST Client. Currently if a method has a default method, the method cannot be invoked due to the default method not being found in the map of invokers. The invokers are collected and proxied only if they have an HTTP method associated with them.

Invoking a default method results in a RuntimeException

java.lang.RuntimeException: RESTEASY004530: Could not find a method for: public default java.lang.String dev.resteasy.example.BasicResource.postBasic(java.lang.String)

This should simply just invoke the default method.