x402-facilitator

x402-facilitator is a Go-based middleware that settles on-chain payments authorized via the x402 protocol.

Prerequisites

• Golang 1.24 or later
• Docker
• Docker Compose

Supported schemes × networks

x402 v2 treats the payment scheme (the on-chain protocol used to move funds) and the network (which chain that protocol runs on) as two independent axes. This facilitator currently supports:

Networks are specified in CAIP-2 format (e.g. eip155:84532 for Base Sepolia, eip155:8453 for Base mainnet, eip155:42161 for Arbitrum One). The exact scheme supports both EIP-3009 transferWithAuthorization and Permit2 PermitWitnessTransferFrom payloads on EVM chains; see the --method flag on x402-client to pick between them.

How to run

Build binary

make build

Run x402-facilitator

1. Run with docker compose

docker compose up

2. Configuration

x402-facilitator is configured via config.toml.

# Port for HTTP server (default: 9090)
port = 9090

# Payment protocol scheme. Currently only "exact" is supported; the
# value is the x402 v2 scheme identifier, not a chain name.
scheme = "exact"

# Network in CAIP-2 format. Examples:
#   eip155:84532  — Base Sepolia
#   eip155:8453   — Base mainnet
#   eip155:42161  — Arbitrum One
network = "eip155:84532"

# RPC endpoint the facilitator uses to verify and broadcast
# transactions on the configured network.
url = "https://sepolia.base.org"

# Private key of the facilitator's fee payer (hex, no 0x prefix).
# Leave empty in the repo; inject via your deployment's secret
# management.
privateKey = ""

3. Api Specification

After starting the service, open your browser to:

/swagger/index.html

Run x402-client

Usage:
  x402-client [flags]

Flags:
  -A, --amount string    Amount to send
  -F, --from string      Sender address
  -h, --help             help for x402-client
  -m, --method string    Payment method (eip3009 or permit2) (default "eip3009")
  -n, --network string   CAIP-2 network to pay on (default "eip155:84532")
  -P, --privkey string   Sender private key
  -s, --scheme string    Payment scheme to use (default "exact")
  -T, --to string        Recipient address
  -t, --token string     token contract for sending (default "USDC")
  -u, --url string       Base URL of the facilitator server (default "http://localhost:9090")

Example:
  x402-client -n eip155:84532 -s exact -t USDC -F {0xYourSenderAddress} -T {0xRecipientAddress} -P {YourPrivateKey} -A 1000

Contributing

We welcome any contributions! Feel free to open issues or submit pull requests at any time.