Google Releases A2UI 1.0, a Stable Protocol for Agent-Built Interfaces

What happened

A2UI separates interface description from rendering: the agent describes a form, chart or confirmation step in structured messages, and the receiving app draws it with its own native components without executing agent-supplied HTML or JavaScript. Version 1.0 adds bidirectional function calls, so the interface and the agent can request functions from each other and return structured results or errors; a single interface can also combine components from multiple catalogs.

Renderers cover web, mobile and desktop: React, Angular and Lit on the web, Flutter on mobile, web and desktop, and SwiftUI on iOS; Jetpack Compose on Android currently supports 0.9.1, with 1.0 support coming later. Agent SDKs are available for Python, TypeScript and Dart. Google said Atlassian, Alation, Bloomberg and ByteDance are already building with it; ByteDance's Lynx renderer supports 0.9 and is being adapted, and Gemini's current A2UI integration supports 0.9.1, with the upgrade in progress.

The A2UI protocol and libraries are open source under the Apache 2.0 license, maintained under the a2ui-project organization; messages can travel over the A2A protocol and AG-UI, and can also run inside MCP Apps. Google announced version 1.0 on its developers blog on Nov 11, calling it the first stable version.

Key facts

1. Release: Version 1.0 released Nov 11, the first stable version; the protocol and libraries are open source under Apache 2.0
2. Mechanism: Agents describe interfaces in structured messages; apps render them with their own native components and do not execute agent-supplied HTML or JavaScript
3. New in 1.0: Bidirectional function calls; a single interface can combine components from multiple catalogs
4. Renderers: React, Angular and Lit on the web; Flutter; SwiftUI; Jetpack Compose at 0.9.1, with 1.0 support coming later
5. Adoption: Atlassian, Alation, Bloomberg and ByteDance are already building with it; Gemini's integration is currently at 0.9.1
6. Transport: Messages travel over A2A and AG-UI, and can run inside MCP Apps