cashapi-middleware

Production-ready Express middleware for x402 (Payment Required) on Bitcoin Cash (BCH).

Gated your AI models and APIs with instant 0-conf BCH payments.

Features

• x402 v2 Compliant: Implements the standard WWW-Authenticate and Authorization headers.
• Real-Time Validation: Uses mainnet-js for robust on-chain 0-conf verification.
• Dynamic Pricing: Support for reputation-based pricing and discounts.
• Built-in Discovery: Automatically serves /.well-known/402.json manifest.
• Replay Protection: Prevents double-submission of TXIDs.

Installation

npm install cashapi-middleware

Quick Start (Express)

import express from 'express';
import { cashapiMiddleware } from 'cashapi-middleware';

const app = express();

// Protect your AI route
app.post('/api/ai-chat', cashapiMiddleware({
  address: 'bitcoincash:qpm2qavt7wjq73p8u0tmsv55p57m9au48pgshqv6a2',
  priceSats: 1000,
  network: 'mainnet', // Use 'chipnet' for testing
  discovery: {
    enabled: true,
    name: "My AI Service"
  }
}), (req, res) => {
  // This code only runs IF payment is verified on-chain
  const txId = req.cashapi.txId;
  res.json({ result: "AI content unlocked!", payment: txId });
});

app.listen(3000);

How It Works (x402 Protocol)

1. Request: Client requests /api/ai-chat.
2. Challenge: Middleware responds with 402 Payment Required and a WWW-Authenticate challenge containing the address and price.
3. Payment: Client (using the CashApi SDK) broadcasts a BCH transaction.
4. Retry: Client retries the request with Authorization: x402 <token>:<txid>.
5. Verified: Middleware verifies the TXID on-chain. If valid, it passes control to your route handler.

License

MIT