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:

ERC-4337 account on Arbitrum

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:

Usdt0ProtocolEvm with ERC-4337 account

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 protocol builds an ERC20 approval to the source-chain transaction-value helper and the helper bridge call, then submits both in one UserOperation.

Gasless bridge with paymasterToken

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)

The bundled approval and helper call produce one UserOperation hash. The protocol approves enough source token for the amount plus its helper-calculated bridge fee and tolerance.

In 1.0.0-beta.7, bridgeFee for this helper flow is in bridged-token base units. The account's fee is in native base units for native gas, paymaster-token base units for token-paid gas, or zero for sponsored gas. The protocol numerically adds those values when enforcing bridgeMaxFee. Do not interpret the sum as one currency or set an ERC-4337 cap until your integration has confirmed compatible units for its payment mode.

Paymaster policies, token addresses, and URLs are service-specific. Confirm supported tokens and networks with your bundler or paymaster provider before production use.

Next Steps

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

Bridge with ERC-4337

Prerequisites

Create a WalletAccountEvmErc4337 account

Run a gasless bridge with paymaster options

Next Steps

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