EVM Chains

Detailed guide for EVM (Ethereum Virtual Machine) compatible chains.

Supported EVM Chains

T402 supports all major EVM chains through the @t402/evm package.

Mainnet Chains

Chain	Network ID	USDT0 Address	Gasless
Ethereum	`eip155:1`	`0x6C96dE32CEa08842dcc4058c14d3aaAD7Fa41dee`	✅
Arbitrum	`eip155:42161`	`0xFd086bC7CD5C481DCC9C85ebE478A1C0b69FCbb9`	✅
Base	`eip155:8453`	`0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`	✅
Optimism	`eip155:10`	`0x94b008aA00579c1307B0EF2c499aD98a8ce58e58`	✅
Ink	`eip155:57073`	`0x0200C29006150606B650577BBE7B6248F58470c1`	✅
Berachain	`eip155:80094`	`0x779Ded0c9e1022225f8E0630b35a9b54bE713736`	✅
Unichain	`eip155:130`	`0x9151434b16b9763660705744891fA906F660EcC5`	✅

Layer 2 Benefits

Benefit	Description
Lower gas	~100x cheaper than Ethereum mainnet
Faster finality	Seconds vs minutes
Same security	Secured by Ethereum
Same addresses	Use same wallet across L2s

Integration

Server Setup

import { t402ResourceServer, createFacilitatorClient } from '@t402/core/server';
import { registerExactEvmScheme } from '@t402/evm/exact/server';
 
const facilitator = createFacilitatorClient({
  url: 'https://facilitator.t402.io',
});
 
const server = new t402ResourceServer(facilitator);
registerExactEvmScheme(server, {});
 
// Configure routes
const routes = {
  '/api/premium/*': {
    accepts: [
      { scheme: 'exact', network: 'eip155:8453', payTo: '0x...', price: '$0.01' },
      { scheme: 'exact', network: 'eip155:42161', payTo: '0x...', price: '$0.01' },
    ],
  },
};

Client Setup

import { t402Client } from '@t402/core/client';
import { ExactEvmScheme } from '@t402/evm/exact/client';
import { createWalletClient, custom } from 'viem';
import { base } from 'viem/chains';
 
// Create viem wallet client
const walletClient = createWalletClient({
  chain: base,
  transport: custom(window.ethereum),
});
 
// Create T402 client
const client = new t402Client();
client.register('eip155:*', new ExactEvmScheme(walletClient));

import { t402Client } from '@t402/core/client';
import { ExactEvmScheme } from '@t402/evm/exact/client';
import { ethers } from 'ethers';
 
// Create ethers signer
const provider = new ethers.BrowserProvider(window.ethereum);
const signer = await provider.getSigner();
 
// Create T402 client
const client = new t402Client();
client.register('eip155:*', new ExactEvmScheme(signer));

import { t402Client } from '@t402/core/client';
import { ExactEvmScheme } from '@t402/evm/exact/client';
import Web3 from 'web3';
 
// Create web3 instance
const web3 = new Web3(window.ethereum);
const accounts = await web3.eth.getAccounts();
 
// Create T402 client with web3 adapter
const client = new t402Client();
client.register('eip155:*', new ExactEvmScheme({
  address: accounts[0],
  signTypedData: (data) => web3.eth.signTypedData(accounts[0], data),
}));

EIP-3009 (TransferWithAuthorization)

T402 uses EIP-3009 for gasless token transfers.

How It Works

User signs an off-chain authorization message
Facilitator executes the transferWithAuthorization on-chain
User pays no gas - facilitator covers gas costs

Authorization Structure

interface TransferWithAuthorization {
  from: string;        // Payer address
  to: string;          // Recipient address
  value: bigint;       // Amount in smallest unit
  validAfter: bigint;  // Unix timestamp (usually 0)
  validBefore: bigint; // Deadline timestamp
  nonce: bytes32;      // Random nonce
}

Signature Verification

The EIP-712 typed data structure:

const domain = {
  name: 'USD0',
  version: '1',
  chainId: 8453,
  verifyingContract: '0x...',
};
 
const types = {
  TransferWithAuthorization: [
    { name: 'from', type: 'address' },
    { name: 'to', type: 'address' },
    { name: 'value', type: 'uint256' },
    { name: 'validAfter', type: 'uint256' },
    { name: 'validBefore', type: 'uint256' },
    { name: 'nonce', type: 'bytes32' },
  ],
};

Gas Estimation

Average Costs by Chain

Chain	Transfer Cost	Settlement Cost
Ethereum	~$5-50	~$10-100
Arbitrum	~$0.01-0.10	~$0.02-0.20
Base	~$0.001-0.01	~$0.002-0.02
Optimism	~$0.01-0.10	~$0.02-0.20

Gas costs vary with network congestion. L2s are generally 100x cheaper than Ethereum mainnet.

Programmatic Estimation

import { estimateGas } from '@t402/evm';
 
const estimate = await estimateGas({
  network: 'eip155:8453',
  operation: 'transferWithAuthorization',
  rpcUrl: 'https://mainnet.base.org',
});
 
console.log(`Estimated gas: ${estimate.gasLimit}`);
console.log(`Estimated cost: $${estimate.costUsd}`);

Multi-Chain Support

Same Address Across Chains

EVM addresses work across all EVM chains:

const payToAddress = '0x742d35Cc6634C0532925a3b844Bc9e7595f5b1A1';
 
const routes = {
  '/api/premium/*': {
    accepts: [
      { scheme: 'exact', network: 'eip155:1', payTo: payToAddress, price: '$0.01' },
      { scheme: 'exact', network: 'eip155:8453', payTo: payToAddress, price: '$0.01' },
      { scheme: 'exact', network: 'eip155:42161', payTo: payToAddress, price: '$0.01' },
    ],
  },
};

User Network Selection

Let users choose their preferred chain:

import { getNetworkDisplayName, getChainConfig } from '@t402/evm';
 
const supportedNetworks = [
  'eip155:8453',   // Base
  'eip155:42161',  // Arbitrum
  'eip155:10',     // Optimism
];
 
// Display network options to user
supportedNetworks.forEach(network => {
  const config = getChainConfig(network);
  console.log(`${getNetworkDisplayName(network)}: ~$${config.avgGasCost}`);
});

Wallet Integration

MetaMask

// Request account access
await window.ethereum.request({ method: 'eth_requestAccounts' });
 
// Get current chain
const chainId = await window.ethereum.request({ method: 'eth_chainId' });
 
// Switch to Base
await window.ethereum.request({
  method: 'wallet_switchEthereumChain',
  params: [{ chainId: '0x2105' }], // Base = 8453 = 0x2105
});

WalletConnect

import { createWalletClient } from 'viem';
import { WalletConnectConnector } from '@wagmi/connectors/walletConnect';
 
const connector = new WalletConnectConnector({
  options: {
    projectId: 'your-project-id',
    chains: [base, arbitrum, optimism],
  },
});
 
await connector.connect();
const walletClient = await connector.getWalletClient();

Safe Multi-Sig

import { createMultisigClient } from '@t402/wdk-multisig';
 
const multisigClient = await createMultisigClient({
  safeAddress: '0xYourSafeAddress',
  chainId: 8453,
  owners: ['0xOwner1', '0xOwner2', '0xOwner3'],
  threshold: 2,
});

RPC Endpoints

Recommended Providers

Chain	Public RPC	Paid Options
Ethereum	`https://eth.llamarpc.com`	Alchemy, Infura
Arbitrum	`https://arb1.arbitrum.io/rpc`	Alchemy, QuickNode
Base	`https://mainnet.base.org`	Alchemy, QuickNode
Optimism	`https://mainnet.optimism.io`	Alchemy, QuickNode

Configuration

const rpcConfig = {
  'eip155:1': process.env.ETH_RPC_URL || 'https://eth.llamarpc.com',
  'eip155:8453': process.env.BASE_RPC_URL || 'https://mainnet.base.org',
  'eip155:42161': process.env.ARB_RPC_URL || 'https://arb1.arbitrum.io/rpc',
};

Troubleshooting

Common Issues

Issue	Cause	Solution
”Invalid signature”	Wrong chain ID	Verify network matches
”Insufficient funds”	No USDT balance	Fund wallet with USDT
”Nonce already used”	Replay attempt	Generate new nonce
”Deadline passed”	Authorization expired	Sign new authorization

Debugging

import { verifySignature, decodePayment } from '@t402/evm';
 
// Decode payment header
const payment = decodePayment(xPaymentHeader);
console.log('Payment details:', payment);
 
// Verify signature locally
const isValid = await verifySignature({
  message: payment.message,
  signature: payment.signature,
  expectedSigner: payment.from,
});
console.log('Signature valid:', isValid);

Gasless Payments - ERC-4337 integration
Multi-Sig Setup - Safe integration
Testnets - Testing on testnets

Comparison Matrix Non-EVM Chains