Flutter made UI feel simple to reason about: compose widgets, connect state, render the app. Generated UI changes that model. As interfaces become more dynamic and generated on demand, the question shifts from “how do I build this screen?” to “what can external systems ask my app to show, bind, and do?” This session walks through a boundary architecture for generated UI in Flutter. The contract is more than a component schema: it defines the vocabulary of app surfaces, state bindings, action intents, interaction flows, and capabilities that external systems can use. We’ll follow how a request from a server, schema, agent, or tool becomes a resolved render model and then ordinary Flutter widgets. You’ll leave with a practical model for keeping state, actions, and behavior app-owned while still letting external systems request UI on demand. A schema asks. An agent asks. A tool asks. The contract decides. Flutter renders.