A2UI: Agent-to-User Interface

A2UI is an open-source project, complete with a format optimized for representing updateable agent-generated UIs and an initial set of renderers, that allows agents to generate or populate rich user interfaces.

A gallery of A2UI rendered cards, showing a variety of UI compositions that A2UI can achieve.

⚠️ Status: Early Stage Public Preview

Note: A2UI is currently in v0.8 (Public Preview). The specification and implementations are functional but are still evolving. We are opening the project to foster collaboration, gather feedback, and solicit contributions (e.g., on client renderers). Expect changes.

Summary

Generative AI excels at creating text and code, but agents can struggle to present rich, interactive interfaces to users, especially when those agents are remote or running across trust boundaries.

A2UI is an open standard and set of libraries that allows agents to "speak UI." Agents send a declarative JSON format describing the intent of the UI. The client application then renders this using its own native component library (Flutter, Angular, Lit, etc.).

This approach ensures that agent-generated UIs are safe like data, but expressive like code.

High-Level Philosophy

A2UI was designed to address the specific challenges of interoperable, cross-platform, generative or template-based UI responses from agents.

The project's core philosophies:

• Security first: Running arbitrary code generated by an LLM may present a security risk. A2UI is a declarative data format, not executable code. Your client application maintains a "catalog" of trusted, pre-approved UI components (e.g., Card, Button, TextField), and the agent can only request to render components from that catalog.
• LLM-friendly and incrementally updateable: The UI is represented as a flat list of components with ID references which is easy for LLMs to generate incrementally, allowing for progressive rendering and a responsive user experience. An agent can efficiently make incremental changes to the UI based on new user requests as the conversation progresses.
• Framework-agnostic and portable: A2UI separates the UI structure from the UI implementation. The agent sends a description of the component tree and its associated data model. Your client application is responsible for mapping these abstract descriptions to its native widgets—be it web components, Flutter widgets, React components, SwiftUI views or something else entirely. The same A2UI JSON payload from an agent can be rendered on multiple different clients built on top of different frameworks.
• Flexibility: A2UI also features an open registry pattern that allows developers to map server-side types to custom client implementations, from native mobile widgets to React components. By registering a "Smart Wrapper," you can connect any existing UI component—including secure iframe containers for legacy content—to A2UI's data binding and event system. Crucially, this places security firmly in the developer's hands, enabling them to enforce strict sandboxing policies and "trust ladders" directly within their custom component logic rather than relying solely on the core system.

Use Cases

Some of the use cases include:

• Dynamic Data Collection: An agent generates a bespoke form (date pickers, sliders, inputs) based on the specific context of a conversation (e.g., booking a specialized reservation).
• Remote Sub-Agents: An orchestrator agent delegates a task to a remote specialized agent (e.g., a travel booking agent) which returns a UI payload to be rendered inside the main chat window.
• Adaptive Workflows: Enterprise agents that generate approval dashboards or data visualizations on the fly based on the user's query.

Architecture

The A2UI flow disconnects the generation of UI from the execution of UI:

1. Generation: An Agent (using Gemini or another LLM) generates or uses a pre-generated A2UI Response, a JSON payload describing the composition of UI components and their properties.
2. Transport: This message is sent to the client application (via A2A, AG UI, etc.).
3. Resolution: The Client's A2UI Renderer parses the JSON.
4. Rendering: The Renderer maps the abstract components (e.g., type: 'text-field') to the concrete implementation in the client's codebase.

Dependencies

A2UI is designed to be a lightweight format, but it fits into a larger ecosystem:

• Transports: Compatible with A2A Protocol and AG UI.
• LLMs: Can be generated by any model capable of generating JSON output.
• Host Frameworks: Requires a host application built in a supported framework (currently: Web or Flutter).

Getting Started

The best way to understand A2UI is to run the samples.

Prerequisites

• Node.js (for web clients)
• Python (for agent samples)
• A valid Gemini API Key is required for the samples.

Running the Restaurant Finder Demo

1. Clone the repository:

   git clone https://github.com/google/A2UI.git
   cd A2UI

2. Set your API Key:

   export GEMINI_API_KEY="your_gemini_api_key"

3. Run the Agent (Backend):

   cd samples/agent/adk/restaurant_finder
   uv run .

4. Run the Client (Frontend): Open a new terminal window:

   cd samples/client/lit/shell
   npm install
   npm run dev

For Flutter developers, check out the GenUI SDK, which uses A2UI under the hood.

CopilotKit has a public A2UI Widget Builder to try out as well.

Roadmap

We hope to work with the community on the following:

• Spec Stabilization: Moving towards a v1.0 specification.
• More Renderers: Adding official support for React, Jetpack Compose, iOS (SwiftUI), and more.
• Additional Transports: Support for REST and more.
• Additional Agent Frameworks: Genkit, LangGraph, and more.

Contribute

A2UI is an Apache 2.0 licensed project. We believe the future of UI is agentic, and we want to work with you to help build it.

See CONTRIBUTING.md for details on how to get started.