A2A Agent Runtime

@assistant-ui/react-a2a is a runtime adapter for the A2A (Agent-to-Agent) v1.0 protocol. Use it when your backend speaks A2A; the adapter handles the wire protocol so you can focus on the UI.

When to use it

Pick the A2A runtime when:

• You have an A2A v1.0 compatible agent server, or you are building one and want a reference client.
• You want streaming task state, artifacts, and the protocol's full state machine surfaced in the UI.
• You need multi-tenant or extension-aware A2A clients.

If your backend is not A2A-compliant, see picking a runtime for alternatives.

Architecture

@assistant-ui/react-a2a is layered on ExternalStoreRuntime (see architecture). Features that ship as runtime adapters (attachments, speech, feedback, history, threads) work the same way they do everywhere else; see adapters.

Requirements

• An A2A v1.0 compatible agent server.
• React 18 or 19.

A2UI surfaces and stored conversations

The runtime recognizes A2UI operation DataParts by an a2ui media type on the part or its metadata, or by the operation shape itself. It folds operations from status updates, agent messages, task snapshots, and artifacts into one surface state for the assistant message. Each renderable surface becomes a present tool call with id a2ui:<surfaceId>, so it renders through the same setup as A2UI over AG-UI. A deleted surface disappears, and the original DataPart is not rendered as JSON or sent back to the agent.

When you use a history adapter, the assistant message keeps the task data needed to restore what the user saw. Surface parts carry replayable operations in their tool artifact, and merged task artifacts live under metadata.custom.a2a.artifacts, with inline file bytes (raw) left out so a large file cannot push the message past a store's size limit; URLs, text, data, media types and file names are kept:

{
  metadata: {
    custom: {
      a2a: {
        artifacts: [{ artifactId: "report", parts: [{ text: "..." }] }],
      },
    },
  },
}

The Assistant Cloud history adapter has update, so a task paused for input_required or auth_required writes its assistant question to history. Other history adapters record the question only when they expose update; an append-only adapter stores only the settled assistant message.

Install

npm install @assistant-ui/react @assistant-ui/react-a2a

npx expo install @assistant-ui/react-native @assistant-ui/react-a2a

npm install @assistant-ui/react-ink @assistant-ui/react-a2a ink react

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