Auth/API SDK Java


I am building OKTA Auth on top of the quite closed framework. I am forced to use purely API to achieve what client wants. I wanted to use SDKs because they are wrapping both Authentication API and Session API nicely. The problem is that auth-java-sdk is not compatible with latest version of java-sdk. It works only with 8.2.5 or older where the Error class is present but 8.2.5 does not have yet Session API fully functional. Do you have any ideas how to make them compatible or any workound? I need to also mentioned that I have to use .jars, maven is not an option.