AG-UI and A2UI
Despite the naming similarities, AG-UI and A2UI serve very different and complementary roles in the agentic application stack.
AG-UI is the Agent–User Interaction protocol which connects your user-facing application to any agentic backend.
A2UI is a Declarative Generative UI spec, originated by Google, which agents can use to return UI widgets as part of their responses.
CopilotKit and AG-UI both fully support A2UI, as CopilotKit is a launch partner with Google of the official A2UI release.
This page explains how AG-UI and A2UI work together to enable powerful agent-user interactions.
The A2UI Composer - powered by CopilotKit
Generative UI Specifications
Types of Generative UI
| Static | UI is chosen from a fixed set of hand‑built components. |
| Open‑Ended | Arbitrary UI (HTML, iframes, free‑form content) is passed between agent and frontend. |
| Declarative | A structured UI specification (cards, lists, forms, widgets) is used between agent and frontend. |
Several recently released specs have enabled agents to return generative UI, increasing the power and flexibility of the Agent↔User conversation.
A2UI, MCP-UI, and Open-JSON-UI are all Generative UI specifications. Generative UIs allow agents to respond to users not only with text but also with dynamic UI components.
CopilotKit and AG-UI both fully support A2UI, as CopilotKit is a launch partner with Google of the official A2UI release.
You can learn more about the different types of Generative UI and their specifications on our Generative UI page.
| Specification | Origin / Maintainer | Purpose |
|---|---|---|
| A2UI | A declarative, LLM-friendly Generative UI spec. JSONL-based and streaming, designed for platform-agnostic rendering. | |
| Open-JSON-UI | OpenAI | An open standardization of OpenAI's internal declarative Generative UI schema. |
| MCP-UI | Microsoft + Shopify | A fully open, iframe-based Generative UI standard extending MCP for user-facing experiences. |
AG-UI: The Agent-User Interaction Protocol
AG-UI is not a generative UI specification — it is the Agent-User Interaction protocol that provides the bi-directional runtime connection between your user-facing application and any agentic backend.
AG-UI natively supports all of the above generative UI specs (including A2UI) and allows developers to define their own custom generative UI standards as well.
AG-UI Protocol
- •Provides the runtime connection between agentic backend and user-facing app
- •Handles bi-directional communication and state synchronization
- •Focuses on how agents and applications communicate
How They Work Together
AG-UI and generative UI specifications are complementary technologies that work together seamlessly:
- Agents generate UI using a generative UI spec like A2UI, describing the components they want to create.
- AG-UI transports that specification from the agent to the application over the bi-directional runtime connection.
- The application renders the UI components according to the spec, creating the dynamic interface.
- User interactions flow back through AG-UI to the agent, enabling real-time collaboration.
This combination gives developers the flexibility to choose their preferred generative UI format while providing a robust, standardized way to connect agents with user-facing applications.
Ready to Get Started?
Learn more about CopilotKit's launch day support for A2UI, or try it out using our A2A, A2UI and CopilotKit quickstart.
