{
  from: "0xPayer...",
  to: "0xReceiver...",
  value: "1000000", // $1 USDC
  validAfter: "0",
  validBefore: "1699999999",
  nonce: "0x..."
}

{
  permitted: {
    token: "0xWETH...",
    amount: "500000000000000000" // 0.5 WETH
  },
  spender: "0xSwapCollector...",
  nonce: "0x...",
  deadline: "1699999999"
}

import { computePaymentNonce } from '@agentokratia/x402-escrow/client';

const nonce = computePaymentNonce({
  payer: "0xPayer...",
  receiver: "0xReceiver...",
  amount: "1000000",
  validBefore: 1699999999,
});

// These two calls result in only ONE on-chain transfer
await paidFetch(url); // First call: settles payment
await paidFetch(url); // Retry: returns cached result (if same signature)

{
  "success": true,
  "transaction": "0x...",
  "network": "eip155:8453"
}