Bridge USD₮0 EVM API Reference

Class	Description	Methods
Usdt0ProtocolEvm	Main class for bridging USD₮0 tokens across blockchains. Extends `BridgeProtocol` from `@tetherto/wdk-wallet/protocols`.	Constructor, Methods

Usdt0ProtocolEvm

The main class for bridging USD₮0 tokens across different blockchains using the LayerZero protocol. Extends BridgeProtocol from @tetherto/wdk-wallet/protocols.

Constructor

new Usdt0ProtocolEvm(account, config?)

Parameters:

account (WalletAccountEvm | WalletAccountEvmErc4337 | WalletAccountReadOnlyEvm | WalletAccountReadOnlyEvmErc4337): The wallet account to use for bridge operations
config (BridgeProtocolConfig, optional): Configuration object
- bridgeMaxFee (number | bigint, optional): Maximum total bridge cost in wei

Example:

import Usdt0ProtocolEvm from '@tetherto/wdk-protocol-bridge-usdt0-evm'
import { WalletAccountEvm } from '@tetherto/wdk-wallet-evm'

const account = new WalletAccountEvm(seedPhrase, "0'/0/0", {
  provider: 'https://eth.drpc.org'
})

const bridgeProtocol = new Usdt0ProtocolEvm(account, {
  bridgeMaxFee: 1000000000000000n // Maximum bridge fee in wei
})

Methods

Method	Description	Returns	Throws
`bridge(options, config?)`	Bridges tokens to another blockchain	`Promise<BridgeResult>`	If no provider or fee exceeds max
`quoteBridge(options, config?)`	Estimates the cost of a bridge operation	`Promise<Omit<BridgeResult, 'hash'>>`	If no provider

`bridge(options, config?)`

Bridges tokens to a different blockchain using the USD₮0 protocol.

Before calling bridge(), approve the token allowance for the source-chain bridge spender. If you pass oftContractAddress, use the same address as the approval spender.

Parameters:

options (BridgeOptions): Bridge operation options
- targetChain (string): Destination chain name
- recipient (string): Address that will receive the bridged tokens (EVM hex address, Solana base58 address, TON address, or TRON address)
- token (string): Token contract address on source chain
- amount (number | bigint): Amount to bridge in token base units
- oftContractAddress (string, optional): Custom OFT contract address to use instead of auto-resolving from the source chain
- dstEid (number, optional): Custom LayerZero destination endpoint ID override
config (Pick<EvmErc4337WalletConfig, 'paymasterToken'> & Pick<BridgeProtocolConfig, 'bridgeMaxFee'>, optional): Override configuration for ERC-4337 accounts
- paymasterToken ({ address: string }, optional): Paymaster token configuration for gas fees
- bridgeMaxFee (number | bigint, optional): Override maximum bridge fee

Returns: Promise<BridgeResult> - Bridge operation result

Throws:

Error if account is read-only
Error if no provider is configured
Error if bridge fee exceeds maximum allowed

Example:

// Standard EVM account
await account.approve({
  token: '0x...', // USDT contract address
  spender: '0x...', // OFT or bridge spender address
  amount: 1000000n
})

const result = await bridgeProtocol.bridge({
  targetChain: 'arbitrum',
  recipient: '0x...', // Recipient address
  token: '0x...', // ₮ contract address
  amount: 1000000n,
  oftContractAddress: '0x...' // Same address used as approval spender
})

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

// ERC-4337 account
await account.approve({
  token: '0x...', // USDT contract address
  spender: '0x...', // OFT or bridge spender address
  amount: 1000000n
})

const result2 = await bridgeProtocol.bridge({
  targetChain: 'arbitrum',
  recipient: '0x...', // Recipient address
  token: '0x...', // USDT contract address
  amount: 1000000n,
  oftContractAddress: '0x...' // Same address used as approval spender
}, {
  paymasterToken: { address: '0x...' }, // Paymaster token configuration
  bridgeMaxFee: 1000000000000000n
})

console.log('Bridge hash:', result2.hash) // Single hash for bundled operations
console.log('Total fee:', result2.fee)
console.log('Bridge fee:', result2.bridgeFee)

`quoteBridge(options, config?)`

Estimates the cost of a bridge operation without executing it.

Some providers estimate the same bridge transaction that bridge() sends. If that estimate fails because token allowance is missing, approve the source-chain bridge spender before calling quoteBridge().

Parameters:

options (BridgeOptions): Bridge operation options (same as bridge method)
config (Pick<EvmErc4337WalletConfig, 'paymasterToken'>, optional): Override configuration for ERC-4337 accounts
- paymasterToken ({ address: string }, optional): Paymaster token configuration for gas fees

Returns: Promise<Omit<BridgeResult, 'hash'>> - Bridge cost estimate

Throws: Error if no provider is configured

Example:

const quote = await bridgeProtocol.quoteBridge({
  targetChain: 'polygon',
  recipient: '0x...', // Recipient address
  token: '0x...', // USDT contract address
  amount: 1000000n
})

console.log('Estimated fee:', quote.fee, 'wei')
console.log('Bridge fee:', quote.bridgeFee, 'wei')

// Check if fees are acceptable
if (quote.fee + quote.bridgeFee > 1000000000000000n) {
  console.log('Bridge fees too high')
} else {
  // Proceed with bridge
  await account.approve({
    token: '0x...', // USDT contract address
    spender: '0x...', // OFT or bridge spender address
    amount: 1000000n
  })

  const result = await bridgeProtocol.bridge({
    targetChain: 'polygon',
    recipient: '0x...', // Recipient address
    token: '0x...', // USDT contract address
    amount: 1000000n,
    oftContractAddress: '0x...' // Same address used as approval spender
  })
}

Types

BridgeOptions

interface BridgeOptions {
  targetChain: string;              // Destination chain name
  recipient: string;                // Address that will receive bridged tokens
  token: string;                    // Token contract address on source chain
  amount: number | bigint;          // Amount to bridge in token base units
  oftContractAddress?: string;      // Optional custom OFT contract address
  dstEid?: number;                  // Optional destination endpoint ID override
}

BridgeResult

interface BridgeResult {
  hash: string;                     // Main bridge transaction hash
  fee: bigint;                      // Total gas cost in wei
  bridgeFee: bigint;                // Bridge protocol fee in wei
}

BridgeProtocolConfig

interface BridgeProtocolConfig {
  bridgeMaxFee?: number | bigint;    // Maximum total bridge cost in wei
}

EvmErc4337WalletConfig

interface EvmErc4337WalletConfig {
  paymasterToken?: {                // Token to use for paying gas fees
    address: string;
  };
}

Supported Chains

The bridge protocol supports the following chains:

Source Chains (EVM):

'ethereum' (Chain ID: 1)
'arbitrum' (Chain ID: 42161) - ERC-4337 support
'optimism' (Chain ID: 10)
'polygon' (Chain ID: 137)
'berachain' (Chain ID: 80094)
'ink' (Chain ID: 57073)
'plasma' (Chain ID: 9745)
'conflux' (Chain ID: 1030)
'corn' (Chain ID: 21000000)
'avalanche' (Chain ID: 43114)
'celo' (Chain ID: 42220)
'flare' (Chain ID: 14)
'hyperevm' (Chain ID: 999)
'mantle' (Chain ID: 5000)
'megaeth' (Chain ID: 4326)
'monad' (Chain ID: 143)
'morph' (Chain ID: 2818)
'rootstock' (Chain ID: 30)
'sei' (Chain ID: 1329)
'stable' (Chain ID: 988)
'unichain' (Chain ID: 130)
'xlayer' (Chain ID: 196)

Destination Chains:

EVM destinations: same as source-chain set above
'solana' (EID: 30168)
'ton' (EID: 30343)
'tron' (EID: 30420)

Error Handling

The bridge protocol throws specific errors for different failure cases:

try {
  await account.approve({
    token: '0x...', // USDT contract address
    spender: '0x...', // OFT or bridge spender address
    amount: 1000000n
  })

  const result = await bridgeProtocol.bridge({
    targetChain: 'arbitrum',
    recipient: '0x...', // Recipient address
    token: '0x...', // USDT contract address
    amount: 1000000n,
    oftContractAddress: '0x...' // Same address used as approval spender
  })
} catch (error) {
  if (error.message.includes('not supported')) {
    console.error('Chain or token not supported')
  }
  if (error.message.includes('Exceeded maximum fee')) {
    console.error('Bridge fee too high')
  }
  if (error.message.includes('must be connected to a provider')) {
    console.error('Wallet not connected to blockchain')
  }
  if (error.message.includes('requires the protocol to be initialized with a non read-only account')) {
    console.error('Cannot bridge with read-only account')
  }
  if (error.message.includes('cannot be equal to the source chain')) {
    console.error('Cannot bridge to the same chain')
  }
}

Usage Examples

Basic Bridge Operation

import Usdt0ProtocolEvm from '@tetherto/wdk-protocol-bridge-usdt0-evm'
import { WalletAccountEvm } from '@tetherto/wdk-wallet-evm'

async function bridgeTokens() {
  // Create wallet account
  const account = new WalletAccountEvm(seedPhrase, "0'/0/0", {
    provider: 'https://eth.drpc.org'
  })

  // Create bridge protocol
  const bridgeProtocol = new Usdt0ProtocolEvm(account, {
    bridgeMaxFee: 1000000000000000n
  })

  // Get quote first
  const quote = await bridgeProtocol.quoteBridge({
    targetChain: 'arbitrum',
    recipient: '0x...', // Recipient address
    token: '0x...', // USDT contract address
    amount: 1000000n
  })

  console.log('Bridge quote:', quote)

  // Execute bridge
  await account.approve({
    token: '0x...', // USDT contract address
    spender: '0x...', // OFT or bridge spender address
    amount: 1000000n
  })

  const result = await bridgeProtocol.bridge({
    targetChain: 'arbitrum',
    recipient: '0x...', // Recipient address
    token: '0x...', // USDT contract address
    amount: 1000000n,
    oftContractAddress: '0x...' // Same address used as approval spender
  })

  console.log('Bridge result:', result)

  return result
}

Multi-Chain Bridge

async function bridgeToMultipleChains(account, bridgeProtocol) {
  const chains = ['arbitrum', 'polygon', 'ethereum']
  const token = '0x...' // USDT contract address
  const amount = 1000000n
  const recipient = '0x...' // Recipient address

  const results = []

  for (const chain of chains) {
    try {
      // Get quote
      const quote = await bridgeProtocol.quoteBridge({
        targetChain: chain,
        recipient,
        token,
        amount
      })

      console.log(`Bridge to ${chain}:`, quote)

      // Execute bridge
      await account.approve({
        token,
        spender: '0x...', // OFT or bridge spender address for the source route
        amount
      })

      const result = await bridgeProtocol.bridge({
        targetChain: chain,
        recipient,
        token,
        amount,
        oftContractAddress: '0x...' // Same address used as approval spender
      })

      results.push({ chain, result })
      console.log(`Bridge to ${chain} successful:`, result.hash)

    } catch (error) {
      console.error(`Bridge to ${chain} failed:`, error.message)
    }
  }

  return results
}

ERC-4337 Gasless Bridge

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

async function gaslessBridge() {
  // Create ERC-4337 account
  const account = new WalletAccountEvmErc4337(seedPhrase, "0'/0/0", {
    chainId: 42161,
    provider: 'https://arb1.arbitrum.io/rpc',
    bundlerUrl: 'https://api.candide.dev/public/v3/arbitrum',
    entryPointAddress: '0x0000000071727De22E5E9d8BAf0edAc6f37da032',
    safeModulesVersion: '0.3.0',
    paymasterUrl: 'https://api.candide.dev/public/v3/arbitrum',
    paymasterAddress: '0x8b1f6cb5d062aa2ce8d581942bbb960420d875ba',
    paymasterToken: { address: '0x...' } // Paymaster token configuration
  })

  // Create bridge protocol
  const bridgeProtocol = new Usdt0ProtocolEvm(account, {
    bridgeMaxFee: 1000000000000000n
  })

  // Bridge with gasless transactions
  await account.approve({
    token: '0x...', // USDT contract address
    spender: '0x...', // OFT or bridge spender address
    amount: 1000000n
  })

  const result = await bridgeProtocol.bridge({
    targetChain: 'polygon',
    recipient: '0x...', // Recipient address
    token: '0x...', // USDT contract address
    amount: 1000000n,
    oftContractAddress: '0x...' // Same address used as approval spender
  }, {
    paymasterToken: { address: '0x...' } // Paymaster token configuration
  })

  console.log('Gasless bridge result:', result)
  return result
}

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Bridge USD₮0 EVM API Reference

Table of Contents

Usdt0ProtocolEvm

Constructor

Methods

`bridge(options, config?)`

`quoteBridge(options, config?)`

Types

BridgeOptions

BridgeResult

BridgeProtocolConfig

EvmErc4337WalletConfig

Supported Chains

Error Handling

Usage Examples

Basic Bridge Operation

Multi-Chain Bridge

ERC-4337 Gasless Bridge

Node.js Quickstart

WDK Bridge USD₮0 EVM Protocol Configuration

WDK Bridge USD₮0 EVM Protocol Usage

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