@hidayahhtaufik/x402-arc

x402 protocol primitives for Arc Network — types, EIP-712 helpers, EIP-3009 signer, x402 client, and Express middleware.

Part of Aureus Protocol. Used by:

• facilitator/ — TalosFacilitator service
• examples/seller — demo seller using createX402Middleware
• examples/buyer — demo agent using X402Client

Install

npm install @hidayahhtaufik/x402-arc

Quickstart

Network constants

import {
  ARC_CAIP2,
  USDC_TOKEN,
  USDC_EIP712_DOMAIN,
  arcTestnet,
} from "@hidayahhtaufik/x402-arc";

Buyer (agent paying x402 endpoints)

import { privateKeyToAccount } from "viem/accounts";
import { X402Client } from "@hidayahhtaufik/x402-arc/client";

const account = privateKeyToAccount(process.env.BUYER_PRIVATE_KEY as `0x${string}`);
const client = new X402Client(account);

const { data, settlement } = await client.payAndFetch("https://example.com/api/weather");
console.log("Got data:", data);
console.log("Tx hash:", settlement?.transaction);

Seller (Express middleware that gates a route)

import express from "express";
import { createX402Middleware } from "@hidayahhtaufik/x402-arc/server";

const app = express();

const x402 = createX402Middleware({
  facilitatorUrl: "https://x402.arc.auranode.xyz",
  payTo: "0xYourSellerAddress",
  priceUsdc: "0.01",
  description: "Live weather data — paid",
});

app.get("/api/weather", x402, (_req, res) => {
  res.json({ city: "Jakarta", temp_c: 28 });
});

Low-level signing

import { signEip3009Authorization } from "@hidayahhtaufik/x402-arc/client";
import { randomNonce } from "@hidayahhtaufik/x402-arc";

const signed = await signEip3009Authorization(account, {
  from: account.address,
  to: "0xRecipient",
  value: 10_000n,           // 0.01 USDC (6 decimals)
  validAfter: 0n,
  validBefore: 9_999_999_999n,
  nonce: randomNonce(),
});

Architecture

This package is path-agnostic — it does not assume any particular HTTP framework on the buyer side, and the Express middleware is the only framework-coupled module (Express is a peer dependency).

• @hidayahhtaufik/x402-arc — constants, types, EIP-712, EIP-3009 (no I/O)
• @hidayahhtaufik/x402-arc/client — buyer signer + x402 fetch client
• @hidayahhtaufik/x402-arc/server — facilitator HTTP client + Express middleware

Compatibility

• Node ≥ 20
• viem ≥ 2.21
• Optional: express ≥ 4.21 (only if you use the middleware)

License

MIT