x402 EIP-7702 Demo

Interactive demo showing the x402 payment protocol with EIP-7702 gasless transfers. Includes autonomous buyer/seller agents and a real-time web visualization.

Quick Start

curl -L https://foundry.paradigm.xyz | bash

npx @facilitator/demo

Note: You can also use bunx, yarn dlx, or pnpm dlx if you prefer.

This starts Anvil, deploys contracts, funds accounts, starts agents and web UI, then prints a command to run the facilitator:

npx @facilitator/server --relayer-key 0x... --delegate-address 0x... --rpc-url http://127.0.0.1:8545

Run that in a new terminal, then open http://localhost:3030 and click INITIATE.

Topology

+------------------+              +------------------+
|  BUYER AGENT     |              |  SELLER AGENT    |
|  :4000           |---- x402 --->|  :4001           |
|  (1000 USDT)     |              |  (weather API)   |
+------------------+              +--------+---------+
                                           |
                                  +--------v---------+
                                  |  FACILITATOR     |
                                  |  :8080           |
                                  +--------+---------+
                                           |
                                  +--------v---------+
                                  |  ANVIL           |
                                  |  :8545           |
                                  +------------------+

                                  +------------------+
                                  |  WEB UI          |
                                  |  :3030           |
                                  +------------------+

| Service | Port | Description | | ------------ | ---- | -------------------------------------- | | Anvil | 8545 | Local EVM chain (chain ID 31337) | | Buyer Agent | 4000 | Autonomous consumer with ERC-20 tokens | | Seller Agent | 4001 | Weather data provider (1 USDT/request) | | Facilitator | 8080 | Payment verification and settlement | | Web UI | 3030 | Real-time protocol visualization |

Web UI

The web UI shows each step of the x402 protocol:

1. REQUEST -- Buyer sends GET /weather to Seller
2. 402 RESPONSE -- Seller responds with payment requirements
3. SIGN -- Buyer signs EIP-712 intent + EIP-7702 authorization
4. RETRY -- Buyer resends with PAYMENT-SIGNATURE header
5. VERIFY + SETTLE -- Facilitator verifies and submits Type 4 tx
6. DELIVER -- Seller delivers weather data with tx receipt

Features:

• Auto/Step mode toggle for pacing
• Real-time balance tracking
• Signature and settlement detail panels
• SSE-based log streaming

License

MIT