x402/express.mpp

Wraps the official x402 Express middleware so one route accepts MPP and x402 Credentials.

Requires @x402/core and @x402/express 2.22 or later, Express 5 or later, and viem 2.54 or later.

Usage

import { HTTPFacilitatorClient, type RoutesConfig, x402ResourceServer } from '@x402/core/server'
import { ExactEvmScheme } from '@x402/evm/exact/server'
import express from 'express'
import { mpp } from 'mppx/x402/express'
 
const facilitator = new HTTPFacilitatorClient({
  url: 'https://x402.org/facilitator',
})
const server = new x402ResourceServer(facilitator).register(
  'eip155:84532',
  new ExactEvmScheme(),
)
const routes = {
  'GET /api/data': {
    accepts: {
      network: 'eip155:84532',
      payTo: '0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266',
      price: '$0.01',
      scheme: 'exact',
    },
    description: 'Premium data access',
    mimeType: 'application/json',
  },
} satisfies RoutesConfig
 
const app = express()
app.use(mpp(routes, server, { 
  secretKey: process.env.MPP_SECRET_KEY!,
}))
app.get('/api/data', (_request, response) => {
  response.json({ data: 'premium content' })
})

The wrapper leaves x402 response buffering, hooks, handler cancellation, verification, and settlement with the official adapter. A request containing both an MPP Credential and an x402 payment signature returns 400.

Return type

type ReturnType = RequestHandler

Parameters

config

• Type: { paywallConfig?: PaywallConfig; realm?: string; secretKey: string }

MPP Challenge and optional x402 paywall settings. secretKey must contain at least 32 bytes.

routes

• Type: RoutesConfig

Existing x402 route configuration. The first extension-free EIP-3009 exact requirement with valid amount, asset, EVM network, name, recipient, and version fields also produces MPP Tempo and source-chain EVM Challenges.

server

• Type: x402ResourceServer

Existing x402 resource server used for requirement metadata, verification, and settlement.