Cross-boundary communication between desktop and web

We have a desktop product that customers actively use, and we want to migrate toward a SaaS offering. In practice, that means we need backwards compatibility while we ship new features. During that transition you often end up in a "hybrid" state: a desktop shell still exists, but more and more UI and logic moves into web technology (for example hosted inside WebView2). That hybrid state introduces a core challenge: how do you preserve everyday interactions across boundaries? Drag & drop, keyboard copy/paste, focus, selection, and other "it just works" behaviors tend to break the moment parts of the UI live in different browsing contexts (iframes/windows) or even in a host process. Demo repo (reference implementation): https://github.com/EelcoLos/iframe-dnd-demo Live demo: https://eelcolos.github.io/iframe-dnd-demo/ A pragmatic way to do incremental delivery is to introduce new modules behind explicit boundaries : embed legacy/new pieces via IFrame split experiences into separate window