x402 Client SDK

Client-side SDK for making SOL payments in response to HTTP 402 errors.

Features

• Parse 402 payment requirements
• Make SOL payments automatically
• Return transaction signatures
• Check balances
• Devnet & Mainnet support

Installation

npm install x402-client-sdk

Quick Start

import { SolanaX402Client } from 'x402-client-sdk';
import { Keypair } from '@solana/web3.js';

const client = new SolanaX402Client({ network: 'devnet' });
const payer = Keypair.fromSecretKey(/* your key */);

// Automatic payment on 402
try {
  const response = await fetch('https://api.example.com/premium');
} catch (error) {
  if (error.status === 402) {
    // Parse and pay in one step
    const result = await client.payFor402Response(payer, error.data);
    
    // Retry with signature
    const retry = await fetch(url, {
      headers: { 'X-Payment': result.signature }
    });
  }
}

API

Constructor

new SolanaX402Client({
  network: 'devnet' | 'mainnet-beta',
  rpcUrl?: string
})

Methods

| Method | Description | Returns | |--------|-------------|---------| | parsePaymentRequirements(requirements) | Parse 402 response | ParsedPaymentRequest | | executePayment(payer, request) | Send payment | Promise<PaymentResult> | | payFor402Response(payer, requirements) | Parse + Pay (recommended) | Promise<PaymentResult> | | checkBalance(address) | Check SOL balance | Promise<number> |

Static Helpers

// Create keypair from base58 key
SolanaX402Client.keypairFromSecretKey(key)

// Generate new keypair
SolanaX402Client.generateKeypair()

Axios Integration

import axios from 'axios';

axios.interceptors.response.use(
  response => response,
  async error => {
    if (error.response?.status === 402) {
      const result = await client.payFor402Response(
        payer,
        error.response.data
      );
      
      error.config.headers['X-Payment'] = result.signature;
      return axios.request(error.config);
    }
    throw error;
  }
);

Wallet Management

// From file
const keypair = Keypair.fromSecretKey(
  new Uint8Array(JSON.parse(fs.readFileSync('wallet.json')))
);

// From base58
const keypair = SolanaX402Client.keypairFromSecretKey('YOUR_KEY');

// Generate new
const keypair = SolanaX402Client.generateKeypair();

Networks

Devnet:

solana airdrop 2 YOUR_ADDRESS --url devnet

Mainnet: Purchase SOL from exchange

Troubleshooting

| Error | Solution | |-------|----------| | Insufficient balance | Get more SOL (airdrop or purchase) | | Transaction failed | Check network and balance | | No payment option | Verify network matches server |

License

MIT

Contributing

Issues and PRs welcome!

Support

• GitHub Issues

Made with love for Solana