Bridge with ERC-4337

This guide covers prerequisites, how to create an ERC-4337 account, and how to call the bridge with paymaster configuration.

Prerequisites

• @tetherto/wdk-wallet-evm-erc-4337 installed alongside @tetherto/wdk-protocol-bridge-usdt0-evm.
• Bundler and paymaster endpoints for your chain (example uses Arbitrum public URLs from the API reference).
• An ERC-4337 source chain with a configured transaction-value helper: Ethereum, Arbitrum, Plasma, or Polygon.

Create a WalletAccountEvmErc4337 account

You can construct an ERC-4337 signing account using new WalletAccountEvmErc4337(seed, path, config) with chain, provider, bundler, and paymaster settings:

import { WalletAccountEvmErc4337 } from '@tetherto/wdk-wallet-evm-erc-4337'

const seedPhrase = 'abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about'

const account = new WalletAccountEvmErc4337(seedPhrase, "0'/0/0", {
  chainId: 42161,
  provider: 'https://arb1.arbitrum.io/rpc',
  bundlerUrl: 'https://api.candide.dev/public/v3/42161',
  safeModulesVersion: '0.3.0',
  paymasterUrl: 'https://api.candide.dev/public/v3/42161',
  paymasterAddress: '0x8b1f6cb5d062aa2ce8d581942bbb960420d875ba',
  paymasterToken: { address: '0xFd086bC7CD5C481DCC9C85ebE478A1C0b69FCbb9' }
})

You can wrap that account with the new Usdt0ProtocolEvm(account, config?) constructor:

import Usdt0ProtocolEvm from '@tetherto/wdk-protocol-bridge-usdt0-evm'

const bridgeProtocol = new Usdt0ProtocolEvm(account)

Run a gasless bridge with paymaster options

You can execute bridge() with a second argument that includes paymasterToken and an optional bridgeMaxFee override. Do not submit a separate account.approve() call for this flow. The normal ERC-4337 batch is an ERC20 approval to the source-chain transaction-value helper followed by the helper bridge call, submitted in one UserOperation. On Ethereum mainnet, when the resolved token is USD₮ at 0xdAC17F958D2ee523a2206206994597C13D831ec7, the protocol queries the same ERC-4337 account's allowance for that token and helper spender. If the current allowance and computed approveAmount are both greater than zero, it prepends approve(spender, 0), then approve(spender, approveAmount), then the helper bridge call. quoteBridge() uses the same ordering for a WalletAccountReadOnlyEvmErc4337. Standard EVM accounts and every other chain/token path are unchanged.

const USDT_TOKEN_ADDRESS = process.env.USDT_SOURCE_TOKEN_ADDRESS
const USDT0_OFT_ADDRESS = process.env.USDT0_OFT_ADDRESS
const amount = 1000000n
const paymasterToken = { address: '0xFd086bC7CD5C481DCC9C85ebE478A1C0b69FCbb9' }

const result = await bridgeProtocol.bridge(
  {
    targetChain: 'polygon',
    recipient: '0x742d35Cc6634C0532925a3b8D4C9db96C4b4d8b6',
    token: USDT_TOKEN_ADDRESS,
    amount,
    oftContractAddress: USDT0_OFT_ADDRESS
  },
  {
    paymasterToken
  }
)

console.log('Bridge hash:', result.hash)
console.log('Account fee:', result.fee)
console.log('Bridge fee:', result.bridgeFee)

Next Steps

Bridge to non-EVM chains in Bridge cross-ecosystem. For failure modes and cleanup, read Handle errors.