Whitechain + facilitator

Network

	Whitechain Sepolia (current)
CAIP-2	`eip155:1874`
Chain ID	`1874`
RPC	`https://rpc.testnet.whitechain.io`
Explorer	explorer.testnet.whitechain.io
Native token	WBT (not needed by payers)
Faucet (WBT)	faucet.testnet.whitechain.io

Mainnet (eip155:1875) is planned. Networks are defined in lib/chains.ts, and the server's network is set with X402_NETWORK.

Asset


Token	Tether USD (USDT)
Address	`0xcedfB56113143d55b2358b8CFbB0dEB5Ad2f55a7`
Decimals	`6` (`10000` = 0.01 USDT)
EIP-712 domain	`{ name: "Tether USD", version: "1" }`
Transfer method	EIP-3009 `transferWithAuthorization`

The domain goes in extra on every route, and your client needs it to sign:

price: {
  asset: "0xcedfB56113143d55b2358b8CFbB0dEB5Ad2f55a7", // Whitechain Sepolia USDT
  amount: "10000",
  extra: { name: "Tether USD", version: "1" },
}

Facilitator

https://whitechain.007575.xyz verifies and settles payments. GET /supported reports:

json

{
  "kinds": [{ "x402Version": 2, "scheme": "exact", "network": "eip155:1874" }],
  "signers": { "eip155:1874": ["0x79DD6ca37394Abfd0A6cBF1Cb5F35d2D548e2d85"] }
}

Its signer submits transferWithAuthorization and pays the WBT gas, so payers only ever sign.

Getting test funds

WBT (optional, only for sending your own transactions): faucet.testnet.whitechain.io.
USDT: the test token's mint is owner-restricted, so it can't be self-minted. Ask the facilitator or token operator for a test allocation, or have someone who holds test USDT transfer some to you. 1 USDT covers 100 searches.

Add the network to MetaMask manually (Settings → Networks → Add) with the values above, or just press Switch network in the playground.