@facilitator/server

Unified x402 facilitator server supporting both EIP-7702 (any ERC-20 like USDT + native ETH) and ERC-3009 (USDC) payment mechanisms.

Installation

``bash
npm install -g @facilitator/server
`

Usage

$3

Run the server with support for multiple chains and fallback RPCs:

`bash
npx @facilitator/server \
--relayer-key 0x... \
--chain 1=https://,https:// \
--chain 137=https://polygon-rpc.com
`

Format: --chain =,,...

$3

`bash
npx @facilitator/server \
--relayer-key 0x... \
--rpc-url https://mainnet.infura.io/v3/...
`

The chain ID is auto-detected from the RPC endpoint.

$3

| Option | Default | Description |
| -------------------- | ----------- | --------------------------------------------------------------------------- |
| --port | 8080 | Server port |
| --host | 0.0.0.0 | Server host |
| --relayer-key | required | Private key (hex) — pays gas |
| --chain | optional | Config per chain: id=url1,url2. Can be used multiple times. |
| --delegate-address | auto-detect | Deployed Delegate.sol address (overrides known preset for all chains) |
| --rpc-url | optional | Legacy: Single EVM JSON-RPC endpoint (auto-detects chain ID) |

$3

| Endpoint | Method | Description |
| -------------- | ------ | ------------------------------------------------- |
| /verify | POST | Verify payment signatures and balance (read-only) |
| /settle | POST | Verify + submit on-chain transaction |
| /supported | GET | Supported schemes, networks, signers |
| /healthcheck | GET | { status: "ok" } |
| /info | GET | Relayer ETH balance |

Supported Mechanisms

| Mechanism | Scheme | Token Support | How It Works |
| --------- | --------- | ---------------------------------------------- | ------------------------- |
| EIP-7702 | eip7702 | Any ERC-20 (USDT, DAI) + native ETH | Account-level delegation |
| ERC-3009 | exact | Tokens with transferWithAuthorization (USDC) | Token-level authorization |

Dependencies

- @facilitator/eip7702 — EIP-7702 mechanism implementation
- @x402/core — Protocol types and facilitator interface
- @x402/evm — ERC-3009 / Permit2 mechanism implementation
- viem` — Ethereum client

License

MIT