This article details a practical technique that safely reconciles the production stability and integrity of the HathiTrust Digital Library (HTDL) with the riskier and potentially disruptive experimental functionalities created by the HathiTrust Research Center. Web systems produced by HTRC are necessarily more speculative and, understandably, operate on equipment outside of the HTDL production environment. The key to our approach that brings these two parts closer together is to exploit user-scripting: a web browser add-in technique that allows users to introduce bespoke Javascript code that alters the behavior of specific website(s). We demonstrate how it can be used to provide a mashup of three web sites: HTDL and two web-based offerings operated independently by HTRC. The end result is that the user interacts with the HTDL as usual, and at strategic locations in the interface additionally functionality drawn from the research systems-which takes account of the user's current context-is seamlessly blended in.