@x402janus/middleware

Express + Next.js middleware for pre-transaction wallet security scanning with x402janus.

• ✅ x402 micropayment flow (EIP-3009 TransferWithAuthorization)
• ✅ No API keys / no bearer tokens
• ✅ Risk policy controls (block / warn / log)
• ✅ Direct scan utility for custom integration

Install

npm install @x402janus/middleware

Usage

Express

import express from 'express';
import { withJanusScan } from '@x402janus/middleware';

const app = express();
app.use(express.json());

app.use('/trade', withJanusScan({
  tier: 'quick',
  onRisk: 'block',
  riskThreshold: 50
}));

Next.js Route Handler

import { withJanusScan } from '@x402janus/middleware/nextjs';

async function handler(req: Request) {
  return Response.json({ ok: true });
}

export const POST = withJanusScan(handler, {
  tier: 'quick',
  onRisk: 'block'
});

Direct scan

import { scanWallet } from '@x402janus/middleware';

const result = await scanWallet('0x000000000000000000000000000000000000dEaD', {
  tier: 'standard',
  privateKey: process.env.JANUS_PRIVATE_KEY
});

Config

interface JanusMiddlewareConfig {
  tier: 'free' | 'quick' | 'standard' | 'deep';
  privateKey?: string;
  onRisk?: 'block' | 'warn' | 'log';
  riskThreshold?: number;
  apiUrl?: string; // default: https://x402janus.com
  extractAddress?: (req: any) => string | null;
  timeoutMs?: number; // optional override
}

Default private key lookup for paid tiers:

1. privateKey (config)
2. ETH_PRIVATE_KEY
3. JANUS_PRIVATE_KEY

x402 flow

1. GET /api/guardian/scan/{address}?tier={tier}
2. Receive 402 with payment requirements
3. Build EIP-3009 TransferWithAuthorization (USDC on Base)
4. Sign with caller private key
5. Retry request with X-PAYMENT: <signed payload>
6. Receive scan JSON

Security

• Private key is never logged.
• Address is validated before request.
• HTTPS is enforced for API endpoint.
• Timeout defaults:
  • quick: 10s
  • standard: 30s
  • deep: 120s

Development

npm test
npm run build