x402 0.1.0

Unified package for the x402 protocol with support for multiple blockchains.

x402

x402 is the main client-side library for the x402 payment protocol in Dart. It provides a unified interface to handle "402 Payment Required" flows across multiple blockchain ecosystems, currently supporting EVM (Ethereum) and SVM (Solana).

This is the primary package intended for general use. You typically do not need to import x402_core, x402_evm, or x402_svm separately, as this package exports all necessary components.

Features

• Multi-Chain Support: Unified handling for EVM and SVM chains.
• Automated Handshake: Simplifies the negotiation between client signers and server requirements.
• Standardized Models: Consistent data structures for payment requirements and payloads.

Getting Started

Add the dependency to your pubspec.yaml:

dependencies:
  x402: ^0.1.0

Usage

There are two primary ways to interact with the protocol:

1. Using X402Client (Recommended)

The X402Client is a high-level wrapper around the standard http.Client. It automatically detects 402 responses, finds a compatible signer, and retries the request with the required payment proof.

final client = X402Client(
  signers: [evmSigner, svmSigner],
  onPaymentRequired: (req, resource, signer) async {
    // Optional: Ask for user confirmation or add condition
    return true; 
  },
);

final response = await client.get(Uri.parse('https://api.example.com/premium'));

2. Manual Handling

If you need granular control, you can perform the handshake manually by parsing the payment-required header and using a specific X402Signer to generate the signature.

final response = await client.get(uri);
if (response.statusCode == 402) {
  // Parse header, negotiate, sign, and retry manually
}

Take a look at the examples folder for complete implementations of both approaches.

Related Packages

• x402_core: Internal protocol definitions.
• x402_evm: EVM implementation details.
• x402_svm: SVM implementation details.