Flutter Just Stopped Shipping Fixed UIs. Inside GenUI and the A2UI Protocol

For most of Flutter's life, the deal has been simple. You write a widget tree, you ship it, and the only thing that changes at runtime is data. The structure of the screen stays frozen the moment you hit build. That assumption just broke. At Google I/O 2026, the Flutter team introduced Flutter GenUI , built on an open protocol called A2UI (Agent-to-UI) . On paper it reads like a minor SDK addition. In practice it changes what "building a Flutter app" means. I wanted to write it up because it's…