GenUI and A2UI: How Flutter Is Redefining AI-Driven User Interfaces

We’re moving beyond walls of text and chatbots. The next frontier of AI-powered apps is Generative UI (GenUI) — where AI constructs and responds with real-time, interactive interfaces instead of just markdown. Flutter is leading this shift through the A2UI protocol and GenUI SDK.

What Is A2UI?

A2UI (Agent-to-UI) is an open protocol from Google that standardizes how AI agents communicate with UI frameworks. It defines how agents send structured UI descriptions that frameworks interpret and render:

Agent → A2UI Protocol → Transport → Framework → Rendered UI

The protocol is framework-agnostic. It works with Flutter, React, SwiftUI, or any UI framework that implements a renderer.

A2UI Message Format

A2UI messages follow a structured format:

{
  "version": "0.9",
  "type": "ui_update",
  "surface_id": "main",
  "widget_tree": {
    "type": "Column",
    "children": [
      {
        "type": "Text",
        "data": "Hello, World!",
        "style": "headlineMedium"
      },
      {
        "type": "ElevatedButton",
        "label": "Click me",
        "onPressed": "action:handle_click"
      }
    ]
  }
}

This declarative format allows agents to describe UI dynamically while the rendering framework handles the actual pixel output.

Flutter GenUI SDK

The Flutter GenUI SDK uses A2UI as its underlying protocol. When you use GenUI, you’re using A2UI under the covers.

Key capabilities:

• Cross-platform: Same agent works on iOS, Android, web, and desktop.
• Native performance: Flutter widgets rendered natively on each platform.
• Brand consistency: UIs match your app’s design system.
• Server-driven UI: Agents control what’s shown without app updates.

Package downloads are up 500% since the beginning of 2026, showing strong ecosystem adoption.

Real-World Examples

Google Opal

Opal enables hundreds of thousands of people to build AI mini-apps using natural language. A2UI powers the dynamic, generative UI system that makes these apps possible.

Finnish It

Catagay Ulusoy’s Finnish language learning app doesn’t just create custom lesson plans — it dynamically composes the perfect UI for each lesson on the fly.

Hatcha

A social event planning app where hosts plan through a conversational interview while GenUI generates themed invites, tailored components, and planning modules.

A2UI Ecosystem

A2UI is being adopted across Google and partner organizations:

• Gemini Enterprise: Rich interactive UIs for business workflows.
• Google ADK: Agent Development Kit with built-in A2UI rendering.
• AG-UI / CopilotKit: Full-stack agentic framework with day-zero A2UI support.
• AG2: Multi-agent framework with native A2UI capabilities.

Client-Side Functions

GenUI v0.10.0 introduces client-side functions, allowing agents to direct the client to perform validation, derived values, and small tasks without a round trip. This reduces latency and improves responsiveness.

Getting Started

import 'package:genui/genui.dart';

// GenUI handles A2UI communication automatically
final genui = GenUI(
  surfaceId: 'main',
  agentUrl: 'https://your-agent-endpoint.com',
);

The A2UI protocol is at version 0.9.1, with v1.0 as a candidate. The ecosystem is maturing rapidly, with community renderers emerging for React, Angular, and other frameworks.

Sources:

• A2UI in the World
• GenUI Package
• What’s new in Flutter 3.44