@t402/wdk-gasless

Gasless USDT0 payments with the 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 | 80094 | ✅ | - | | 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',
})

Related Packages

• @t402/core - Core protocol types and client
• @t402/wdk - the WDK integration
• @t402/wdk-bridge - Cross-chain LayerZero bridging
• @t402/wdk-multisig - Safe multi-sig wallets
• @t402/evm - EVM mechanism implementation

License

Apache-2.0

Trademark Notice

T402 is an independent open-source project. It is not affiliated with, endorsed by, sponsored by, or in any way officially connected with Tether Operations Limited, Tether Holdings, or any of their affiliates.

"Tether", "USDT", "USDT0", "USDC", and other token names and trademarks referenced are the property of their respective owners and are used nominatively to describe token interoperability or to reference public open-source products (Apache 2.0). Compatibility with Tether's open-source WDK is at the user's option and does not represent a formal partnership.