soulink402

One-call x402 Express middleware. Turn any route into a paid API.

Install

npm install soulink402

Quick Start

import express from 'express'
import { x402 } from 'soulink402'

const app = express()

app.use(await x402({
  payTo: '0xYourWalletAddress',
  network: 'base',
  routes: {
    'POST /api/register': {
      price: '1',
      description: 'Register an agent',
    },
    'GET /api/premium': {
      price: '0.5',
      description: 'Premium content',
    },
  },
}))

API

x402(config): Promise<ExpressMiddleware>

Creates Express middleware that enforces x402 payments on matched routes.

| Field | Type | Description | |-------|------|-------------| | payTo | string | Wallet address to receive payments | | network | 'base' \| 'base-sepolia' \| NetworkId | Target blockchain network | | routes | Record<string, SimpleRouteConfig> | Route pattern to payment config map |

SimpleRouteConfig

| Field | Type | Description | |-------|------|-------------| | price | string \| (ctx) => string | USDC price (static or dynamic) | | description | string | Human-readable route description |

buildRoutes(config): RoutesConfig

Transforms X402Config into the low-level RoutesConfig format used by @x402/express. Useful if you need the route config without the middleware.

resolveNetwork(name): NetworkId

Resolves a friendly network name to a CAIP-2 identifier.

Networks

| Name | CAIP-2 ID | |------|-----------| | base | eip155:8453 | | base-sepolia | eip155:84532 |

Raw CAIP-2 strings (e.g. eip155:1) pass through unchanged.

Dynamic Pricing

Price can be a function that receives the HTTP request context:

app.use(await x402({
  payTo: '0x...',
  network: 'base',
  routes: {
    'POST /api/register': {
      price: (context) => {
        const body = context.adapter.getBody?.() as { tier?: string }
        return body?.tier === 'premium' ? '10' : '1'
      },
      description: 'Register with tiered pricing',
    },
  },
}))

What it replaces

Before (25 lines of ceremony):

import { paymentMiddlewareFromHTTPServer, x402HTTPResourceServer, x402ResourceServer } from '@x402/express'
import { HTTPFacilitatorClient } from '@x402/core/http'
import { ExactEvmScheme } from '@x402/evm/exact/server'
import { facilitator } from '@coinbase/x402'

const client = new HTTPFacilitatorClient(facilitator)
const routes = { 'POST /api/register': { accepts: { scheme: 'exact', network: 'eip155:8453', payTo: '0x...', price: '1' }, description: '...' } }
const server = new x402ResourceServer(client).register('eip155:8453', new ExactEvmScheme())
const http = new x402HTTPResourceServer(server, routes)
app.use(paymentMiddlewareFromHTTPServer(http))

After (6 lines):

import { x402 } from 'soulink402'

app.use(await x402({
  payTo: '0x...',
  network: 'base',
  routes: { 'POST /api/register': { price: '1', description: '...' } },
}))

License

MIT