A2a Simulator

A2A Simulator

Part of the [AgentDM](https://agentdm.ai) project.

A Client-Server simulator for the [Google A2A (Agent-to-Agent)](https://github.com/a2aproject/A2A) protocol. Each instance runs as both an A2A server and client simultaneously, letting you test bidirectional agent communication from a single tool.

Inspired by the [A2A Inspector](https://github.com/a2aproject/a2a-inspector), which provides a client-only view of A2A interactions. This project goes further by embedding a full A2A server alongside the client, so you can observe and control both sides of a conversation. Run two instances side by side and watch messages flow in both directions.


What It Does

The simulator gives you a chat-like UI where you act as the human behind an A2A agent. You can connect to a remote agent, send messages, and see streaming responses in real time. At the same time, your instance is hosting its own A2A endpoints, so other agents (or a second simulator instance) can connect to you.

This makes it possible to debug the full lifecycle of A2A task exchanges: message sending, streaming status updates, `input-required` round trips, artifact attachments, task cancellation, and resubscription.

Every message includes a "View raw" link that opens the underlying JSON-RPC request and response, so you can inspect exactly what's going over the wire.

Quick Start

npm install

Running Two Instances

Open two terminals:

# Terminal 1
npm run dev -- --port 3000 --name "Agent Alpha"

# Terminal 2
npm run dev -- --port 3001 --name "Agent Beta"

Open `http://localhost:5173` (Vite dev server proxies to port 3000 by default). In the connection panel, enter `http://localhost:3001` and click Connect. You're now Agent Alpha talking to Agent Beta.

To see Agent Beta's perspective, open its Vite dev server on a different port or build and serve both instances.

VS