Merging user interface (UI) object trees comprising UI trees from different technologies (e.g., host and one or more guest technologies) can involve registering guest technologies with a technology adapter layer, for example, used to manage UI tree merging. Further, identifying whether a UI object can be switched from a first technology to a second technology can comprise using a host technology provider to identify if a UI object can be switched, when navigating down the UI tree. When navigating up the UI tree, information stored by the technology adapter layer can be used to identify if a UI object can be switched. Additionally, identifying the second technology can comprise having the technology adapter layer request technology switching capability information from registered technologies for the UI object when navigating down the UI tree. When navigating up the UI tree, information stored by the technology adapter layer can be used to identify the second technology. Also, converting the UI object from the first technology to the second technology in the UI tree can be performed using a COM-based conversion.