Christopher,
Most of our product developed in Agentry uses the Java Backend for authentication or SQL Authentication. In theory during the Server authentication, the system (Thru Server authentication and class) has to return true for the Agentry Server to accept the connection.
By stating HTTP-XML as your Backend Connection and making it the primary authentication criteria, there may be a need wherein the Agentry server and authentication classes needs to receive a true or return for your system. If you are using AD then there may be libraries that needs to created to use the Agentry server classes for your authentication. For example, in our Work Manager product, our product team had to create special jar files that utilize the authentication libraries (Agentry server.class and others) to make things work.
I think something to that regards may need to be done. I have no example of this type of pure connectivity (HTTPXML) from any of our out of the box but one of our partners who have pure HTTPXML backend was able to get it to work but I did not have the chance to look at their application libraries in detail. They may have worked with the Agentry server libraries (i.e. server.class and others) or something else. Not sure if they are online and they can comment on their project.
Regards,
Mark Pe
SAP Platinum Support Engineer