Buyer: Node paid fetch

The Buyer calls the Seller, receives a 402 challenge, signs locally and resends through the native x402 fetch flow. It does not need the Seller's Facilitator API key. Keep the signing seed in application-owned secret storage; never embed it in browser JavaScript.

Buyer — Node · TypeScript

import { createBuyerFetch } from 'agentsmith-x402-sdk/buyer';

const secret = process.env.STELLAR_SECRET;
if (!secret) throw new Error('Set STELLAR_SECRET');

const paidFetch = createBuyerFetch({
  secret,
  network: 'stellar:testnet',
  schemes: ['exact'],
});
const response = await paidFetch('http://localhost:3000/price');
if (!response.ok) throw new Error(`Paid request failed: ${response.status}`);
const data = await response.json();

Approve a payment before signing

Add the following hook to createBuyerFetch to apply your own approval policy. Omit the hook for automatic agent signing. The approval function is supplied by your application.

Buyer — application approval · TypeScript

onBeforePaymentCreation: async ({ selectedRequirements }) => {
  const approved: boolean = await approvePayment(selectedRequirements); // your application policy/UI
  if (!approved) return { abort: true, reason: 'Payment declined' };
},