Q402 Developer Docs

// From the dashboard
// 1. Connect your wallet
// 2. Click "Authenticate Wallet"
// 3. Sign the challenge message
// 4. Copy the current trial API key to your backend only

<script src="https://q402.io/q402-sdk.js"></script>

const q402 = new Q402Client({
  chain: "bnb", // "bnb" | "eth" | "xlayer"
});

const prepared = await q402.preparePayment({
  to: recipientAddress,
  amount: "50",
  token: "USDC",
});
// Send "prepared" to your backend. Do not store your API key in the browser.

// POST to Q402 relay — Q402 handles the rest
const res = await fetch("https://q402.io/api/relay", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    apiKey: process.env.Q402_API_KEY,
    ...prepared,
  }),
});
const data = await res.json();
// { success: true, txHash: "0xabc123...", chain: "bnb", blockNumber: "38482910" }

// POST /api/auth/challenge
{
  "address": "0xYourWallet..."
}

// Response
{
  "message": "Sign this message to start your Q402 free trial. ...",
  "expiresIn": 600
}

// POST /api/keys/provision
{
  "address": "0xYourWallet...",
  "signature": "0xSignedChallenge..."
}

// Response
{
  "apiKey": "q402_live_YOUR_API_KEY",
  "plan": "trial",
  "isNew": true
}

// POST /api/relay
{
  "apiKey": "q402_live_YOUR_API_KEY",
  "chain":  "bnb",
  "token":  "USDC",
  ...
}

// POST /api/gas-tank/verify-deposit
{
  "apiKey": "q402_live_YOUR_API_KEY",
  "chain": "bnb",
  "txHash": "0xDepositTransactionHash..."
}

// Contract addresses per chain
const CONTRACTS = {
  bnb:    "0x2Eb0c999Ac01098Da44763Aa7E87479d905ecdC7",
  eth:    "0x2Eb0c999Ac01098Da44763Aa7E87479d905ecdC7",
  xlayer: "0xf3eDaCAa8A247B8B8F898FAFA5AEd8E161ADc72a",
};

// SignatureBasedExecutorV2 uses a fixed domain across live chains
const domain = {
  name:              "SignatureBasedExecutorV2",
  version:           "2",
  chainId:           56,              // 1=ETH, 56=BNB, 196=X Layer
  verifyingContract: CONTRACTS.bnb,
};

const types = {
  TransferAuthorization: [
    { name: "owner",       type: "address" },
    { name: "facilitator", type: "address" },
    { name: "token",       type: "address" },
    { name: "recipient",   type: "address" },
    { name: "amount",      type: "uint256" },
    { name: "nonce",       type: "uint256" },
    { name: "deadline",    type: "uint256" },
  ],
};

const signature = await signer.signTypedData(domain, types, {
  owner:       userAddress,
  facilitator: relayInfo.facilitator,
  token:       usdcAddress,
  recipient:   recipientAddress,
  amount:      ethers.parseUnits("50", 6),
  nonce:       currentNonce,
  deadline:    Math.floor(Date.now() / 1000) + 3600,
});