Q402 Developer Docs

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

// Initialize once with your API key + chain
const q402 = new Q402Client({
  apiKey: "q402_live_YOUR_KEY",
  chain:  "bnb",   // "bnb" | "avax" | "eth" | "xlayer" | "stable" | "mantle" | "injective"
});
// Note: when chain is "injective", only token: "USDT" is supported.
// Native USDC via Circle CCTP is announced for Q2 2026.

// Wallet popup appears — user signs, Q402 relays on-chain
// amount MUST be a human-readable decimal STRING (e.g. "50.00", "0.123456").
// Never pass a JS Number — IEEE-754 loses precision on 18-decimal tokens.
// Inputs exceeding the token's decimals or non-decimal strings throw.
const result = await q402.pay({
  to:     recipientAddress,
  amount: "50.00",
  token:  "USDC",
});
// result → { success: true, txHash: "0xabc...", tokenAmount: "50", chain: "bnb" }

const q402 = new Q402Client({
  apiKey: "q402_live_YOUR_KEY",
  chain:  "injective",
});

const result = await q402.pay({
  to:     recipientAddress,
  amount: "50.00",
  token:  "USDT",   // required — USDC not yet supported on Injective
});

// Full result shape:
// {
//   success:       true,
//   txHash:        "0xdef456...",
//   chain:         "bnb",
//   blockNumber:   "38482910",
//   tokenAmount:   "50",
//   token:         "USDC",
//   gasCostNative: 0.000021,
//   method:        "eip7702",
// }
console.log("Paid! TX:", result.txHash);

# Claude Code CLI
claude mcp add q402 -- npx -y @quackai/q402-mcp

# Or paste this into claude_desktop_config.json:
# (macOS:   ~/Library/Application Support/Claude/claude_desktop_config.json)
# (Windows: %APPDATA%\Claude\claude_desktop_config.json)
{
  "mcpServers": {
    "q402": {
      "command": "npx",
      "args": ["-y", "@quackai/q402-mcp"]
    }
  }
}

Q402_API_KEY=q402_live_...      # live-tier key from /dashboard
Q402_PRIVATE_KEY=0xabc...       # signer for the payer EOA
Q402_ENABLE_REAL_PAYMENTS=1     # explicit opt-in

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

// Implementation contract per chain
const CONTRACTS = {
  avax:   "0x96a8C74d95A35D0c14Ec60364c78ba6De99E9A4c", // Q402 Avalanche (chainId: 43114)
  bnb:    "0x6cF4aD62C208b6494a55a1494D497713ba013dFa", // Q402 BNB Chain (chainId: 56)
  eth:    "0x8E67a64989CFcb0C40556b13ea302709CCFD6AaD", // Q402 Ethereum  (chainId: 1)
  xlayer: "0x8D854436ab0426F5BC6Cc70865C90576AD523E73", // Q402 X Layer   (chainId: 196)
  stable: "0x2fb2B2D110b6c5664e701666B3741240242bf350", // Q402 Stable    (chainId: 988)
  mantle: "0x2fb2B2D110b6c5664e701666B3741240242bf350", // Q402 Mantle    (chainId: 5000)
  injective: "0x2fb2B2D110b6c5664e701666B3741240242bf350", // Q402 Injective (chainId: 1776)
};

// EIP-712 domain name — must match contract NAME constant exactly
const DOMAIN_NAMES = {
  avax:      "Q402 Avalanche",
  bnb:       "Q402 BNB Chain",
  eth:       "Q402 Ethereum",
  xlayer:    "Q402 X Layer",
  stable:    "Q402 Stable",
  mantle:    "Q402 Mantle",
  injective: "Q402 Injective",
};

// verifyingContract:
//   ALL chains → user's own EOA  (address(this) under EIP-7702 delegation)

// Every deployed Q402 impl contract uses the same EIP-712 typed struct:
const types = {
  TransferAuthorization: [
    { name: "owner",       type: "address" }, // token sender (user's EOA)
    { name: "facilitator", type: "address" }, // gas sponsor (Q402 relayer)
    { name: "token",       type: "address" }, // ERC-20 contract (USDC / USDT / USDT0)
    { name: "recipient",   type: "address" }, // payment destination
    { name: "amount",      type: "uint256" }, // atomic units
    { name: "nonce",       type: "uint256" }, // random uint256, replay protection
    { name: "deadline",    type: "uint256" }, // unix timestamp
  ],
};

// verifyingContract is ALWAYS the user's own EOA — the contract computes its
// domain separator with address(this), which equals the user EOA under EIP-7702.

// Fetch facilitator address first (required for all chains)
const { facilitator } = await fetch("https://q402.quackai.ai/api/relay/info").then(r => r.json());

const domain = {
  name:              DOMAIN_NAMES[chain],
  version:           "1",
  chainId:           chainId,
  verifyingContract: userAddress,  // user's own EOA — same for all chains under EIP-7702
};

const nonce = ethers.toBigInt(ethers.randomBytes(32)); // random uint256

const signature = await signer.signTypedData(domain, types, {
  owner:       userAddress,
  facilitator,
  token:       tokenAddress,
  recipient:   recipientAddress,
  amount:      ethers.parseUnits("50", decimals), // 6 decimals on most chains; 18 only for Stable chain's USDT0
  nonce,
  deadline:    BigInt(Math.floor(Date.now() / 1000) + 600),
});