@x402/evm

EVM (Ethereum Virtual Machine) implementation of the x402 payment protocol using the Exact payment scheme with EIP-3009 TransferWithAuthorization.

Installation

npm install @x402/evm

Overview

This package provides three main components for handling x402 payments on EVM-compatible blockchains:

• Client - For applications that need to make payments (have wallets/signers)
• Facilitator - For payment processors that verify and execute on-chain transactions
• Service - For resource servers that accept payments and build payment requirements

Package Exports

Main Package (@x402/evm)

V2 Protocol Support - Modern x402 protocol with CAIP-2 network identifiers

Client:

• ExactEvmClient - V2 client implementation using EIP-3009
• toClientEvmSigner(account) - Converts viem accounts to x402 signers
• ClientEvmSigner - TypeScript type for client signers

Facilitator:

• ExactEvmFacilitator - V2 facilitator for payment verification and settlement
• toFacilitatorEvmSigner(wallet) - Converts viem wallets to facilitator signers
• FacilitatorEvmSigner - TypeScript type for facilitator signers

Service:

• ExactEvmServer - V2 service for building payment requirements

V1 Package (@x402/evm/v1)

V1 Protocol Support - Legacy x402 protocol with simple network names

Exports:

• ExactEvmClientV1 - V1 client implementation
• ExactEvmFacilitatorV1 - V1 facilitator implementation
• NETWORKS - Array of all supported V1 network names

Supported V1 Networks:

[
  "abstract", "abstract-testnet",
  "base-sepolia", "base",
  "avalanche-fuji", "avalanche",
  "iotex", "sei", "sei-testnet",
  "polygon", "polygon-amoy",
  "peaq", "story", "educhain",
  "skale-base-sepolia"
]

Version Differences

V2 (Main Package)

• Network format: CAIP-2 (eip155:8453)
• Wildcard support: Yes (eip155:*)
• Payload structure: Partial (core wraps with metadata)
• Extensions: Full support
• Validity window: 1 hour (default)

V1 (V1 Package)

• Network format: Simple names (base-sepolia)
• Wildcard support: No (fixed list)
• Payload structure: Complete
• Extensions: Limited
• Validity window: 10 minutes with buffer

Usage Patterns

1. Direct Registration (Full Control)

import { x402Client } from "@x402/core/client";
import { ExactEvmClient } from "@x402/evm";
import { ExactEvmClientV1 } from "@x402/evm/v1";

const client = new x402Client()
  .register("eip155:*", new ExactEvmClient(signer))
  .registerSchemeV1("base-sepolia", new ExactEvmClientV1(signer))
  .registerSchemeV1("base", new ExactEvmClientV1(signer));

Extension RPC Configuration (Optional)

ExactEvmClient only requires signer support for address + signTypedData. Permit2 extension enrichment (EIP-2612 / ERC-20 approval gas sponsoring) can optionally use explicit RPC config when signer read/fee helpers are unavailable.

No chain-default RPC fallback is applied by the SDK.

// Per-network explicit registration
const client = new x402Client()
  .register("eip155:137", new ExactEvmClient(signer, { rpcUrl: polygonRpcUrl }))
  .register("eip155:8453", new ExactEvmClient(signer, { rpcUrl: baseRpcUrl }));

// Wildcard registration with chain-id keyed config map
const wildcardClient = new x402Client().register(
  "eip155:*",
  new ExactEvmClient(signer, {
    137: { rpcUrl: polygonRpcUrl },
    8453: { rpcUrl: baseRpcUrl },
  }),
);

2. Using Config (Flexible)

import { x402Client } from "@x402/core/client";
import { ExactEvmClient } from "@x402/evm";

const client = x402Client.fromConfig({
  schemes: [
    { network: "eip155:*", client: new ExactEvmClient(signer) },
    { network: "base-sepolia", client: new ExactEvmClientV1(signer), x402Version: 1 }
  ],
  policies: [myCustomPolicy]
});

Supported Networks

V2 Networks (via CAIP-2):

• eip155:1 - Ethereum Mainnet
• eip155:8453 - Base Mainnet
• eip155:84532 - Base Sepolia
• eip155:* - Wildcard (matches all EVM chains)
• Any eip155:<chainId> network

V1 Networks (simple names): See NETWORKS constant in @x402/evm/v1

Asset Support

Supports two asset transfer methods:

• EIP-3009: Tokens with native transferWithAuthorization() (e.g., USDC, EURC) — simplest, truly gasless
• Permit2: Any ERC-20 token — universal fallback, requires one-time approval

See DEFAULT_ASSET.md for the current list of configured chains and how to add new ones.

Development

# Build
npm run build

# Test
npm run test

# Integration tests
npm run test:integration

# Lint & Format
npm run lint
npm run format

Related Packages

• @x402/core - Core protocol types and client
• @x402/fetch - HTTP wrapper with automatic payment handling
• @x402/svm - Solana/SVM implementation
• @x402/stellar - Stellar implementation