This paper is about client-specific customization of systems that implement an on-line Internet service in the presence of simultaneous client-specific views. The problem is that each client must be able to customize the running system for use in its own context, without impacting the service behavior that is delivered to other clients. To solve this, we propose to customize the system on a per client request basis, where the system itself consists of a stable core and several extensions that are injected into the core as needed. However, this approach brings on its own several consistency management problems that must be dealt with in order to make the approach viable. We give an overview of these problems and present a management architecture that deals with these problems.