Changing one screen in a mobile app takes longer than it should. You make the change, wait for app review, then wait again for users to update. Some never will. Meanwhile the web team has shipped three times before lunch.

Server-driven UI flips this. The server describes the screen, and the app renders it with real native widgets, so new flows, A/B tests and layout fixes go live without a release. It's also the idea underneath generative UI: when an AI agent builds a screen, it's using the same pattern.

I maintain Stac, an open-source server-driven UI framework for Flutter. In this talk, I'll cover:

- Building a server-driven screen with Stac, from JSON to native widgets
- Keeping six-month-old app versions working when the server changes
- Actions, state and navigation that survive a round trip to the server
- Testing and performance when your UI arrives over the network
- When server-driven UI is the wrong tool for the job