@t402/wdk-gasless

Gasless USDT0 payments with Tether WDK and ERC-4337 Account Abstraction.

Features

• Gasless Payments: Send USDT0/USDC without paying gas fees
• ERC-4337 Integration: Uses Safe smart accounts with Account Abstraction
• Batch Payments: Execute multiple transfers in a single transaction
• Multi-Chain Support: Ethereum, Arbitrum, Base, Optimism, Ink, Berachain, Unichain
• Paymaster Sponsorship: Optional gas sponsorship via paymasters

Installation

npm install @t402/wdk-gasless
# or
pnpm add @t402/wdk-gasless

Peer Dependencies

npm install @tetherto/wdk @tetherto/wdk-wallet-evm

Quick Start

import { createWdkGaslessClient } from '@t402/wdk-gasless'
import { createPublicClient, http } from 'viem'
import { arbitrum } from 'viem/chains'

// Create a public client
const publicClient = createPublicClient({
  chain: arbitrum,
  transport: http(),
})

// Create the gasless client
const client = await createWdkGaslessClient({
  wdkAccount: myWdkAccount, // From @tetherto/wdk
  publicClient,
  chainId: 42161, // Arbitrum
  bundler: {
    bundlerUrl: 'https://api.pimlico.io/v2/arbitrum/rpc?apikey=YOUR_KEY',
    chainId: 42161,
  },
  paymaster: {
    address: '0x...',
    url: 'https://api.pimlico.io/v2/arbitrum/rpc?apikey=YOUR_KEY',
    type: 'sponsoring',
  },
})

// Execute a gasless payment
const result = await client.pay({
  to: '0xRecipientAddress...',
  amount: 1000000n, // 1 USDT0 (6 decimals)
})

// Wait for confirmation
const receipt = await result.wait()
console.log('Payment confirmed:', receipt.txHash)

API Reference

createWdkGaslessClient(config)

Creates a new gasless payment client.

interface CreateWdkGaslessClientConfig {
  wdkAccount: WdkAccount // WDK account from @tetherto/wdk
  publicClient: PublicClient // Viem public client
  chainId: number // Chain ID
  bundler: BundlerConfig // Bundler configuration
  paymaster?: PaymasterConfig // Optional paymaster for gas sponsorship
  saltNonce?: bigint // Salt for address generation (default: 0n)
}

WdkGaslessClient

pay(params): Promise<GaslessPaymentResult>

Execute a single gasless payment.

interface GaslessPaymentParams {
  to: Address // Recipient address
  amount: bigint // Amount in token decimals
  token?: 'USDT0' | 'USDC' | Address // Token (default: 'USDT0')
}

interface GaslessPaymentResult {
  userOpHash: Hex // UserOperation hash
  sender: Address // Smart account address
  sponsored: boolean // Whether gas was sponsored
  wait(): Promise<GaslessPaymentReceipt>
}

payBatch(params): Promise<GaslessPaymentResult>

Execute multiple payments in a single transaction.

interface BatchPaymentParams {
  payments: Array<{
    to: Address
    amount: bigint
    token?: 'USDT0' | 'USDC' | Address
  }>
}

canSponsor(params): Promise<SponsorshipInfo>

Check if a payment can be gas-sponsored.

interface SponsorshipInfo {
  canSponsor: boolean
  reason?: string
  estimatedGasCost?: bigint
}

getBalance(token?): Promise<bigint>

Get the token balance of the smart account.

getFormattedBalance(token?, decimals?): Promise<string>

Get the formatted token balance (human-readable).

getAccountAddress(): Promise<Address>

Get the smart account address.

isAccountDeployed(): Promise<boolean>

Check if the smart account is deployed on-chain.

Supported Chains

| Chain | Chain ID | USDT0 | USDC | | --------- | -------- | ----- | ---- | | Ethereum | 1 | ✅ | ✅ | | Arbitrum | 42161 | ✅ | ✅ | | Base | 8453 | ✅ | ✅ | | Optimism | 10 | ✅ | ✅ | | Ink | 57073 | ✅ | - | | Berachain | 80084 | ✅ | - | | Unichain | 130 | ✅ | - |

Constants

import {
  USDT0_ADDRESSES,
  USDC_ADDRESSES,
  CHAIN_IDS,
  getTokenAddress,
  getChainName,
} from '@t402/wdk-gasless'

// Get USDT0 address on Arbitrum
const usdt0 = USDT0_ADDRESSES.arbitrum
// '0xFd086bC7CD5C481DCC9C85ebE478A1C0b69FCbb9'

// Get chain name from ID
const chainName = getChainName(42161)
// 'arbitrum'

Smart Account Architecture

This package uses Safe smart accounts with ERC-4337 support:

• Safe Singleton: 0x29fcB43b46531BcA003ddC8FCB67FFE91900C762
• Safe 4337 Module: 0xa581c4A4DB7175302464fF3C06380BC3270b4037 (v0.3.0)
• Proxy Factory: 0x4e1DCf7AD4e460CfD30791CCC4F9c8a4f820ec67
• EntryPoint: 0x0000000071727De22E5E9d8BAf0edAc6f37da032 (v0.7)

Examples

Batch Payment

const result = await client.payBatch({
  payments: [
    { to: '0xAlice...', amount: 500000n }, // 0.5 USDT0
    { to: '0xBob...', amount: 300000n }, // 0.3 USDT0
    { to: '0xCharlie...', amount: 200000n }, // 0.2 USDT0
  ],
})

const receipt = await result.wait()
console.log(`Batch payment in tx: ${receipt.txHash}`)

Check Sponsorship

const sponsorship = await client.canSponsor({
  to: '0xRecipient...',
  amount: 1000000n,
})

if (sponsorship.canSponsor) {
  console.log('Payment will be free!')
} else {
  console.log(`Gas cost: ${sponsorship.estimatedGasCost} wei`)
}

Using USDC Instead

const result = await client.pay({
  to: '0xRecipient...',
  amount: 1000000n,
  token: 'USDC',
})

License

Apache-2.0