Cross-Chain Bridge

Transfer USDT0 between chains using LayerZero OFT standard.

Overview

USDT0 is an Omnichain Fungible Token (OFT) that can be bridged between supported chains via LayerZero. T402 provides easy-to-use bridging interfaces for both manual and automatic chain selection.

How It Works

Source Chain                LayerZero                Destination Chain
┌──────────┐               ┌──────────┐              ┌──────────┐
│  USDT0   │──────────────▶│   DVN    │─────────────▶│  USDT0   │
│   OFT    │   send()      │ Network  │   receive()  │   OFT    │
└──────────┘               └──────────┘              └──────────┘

User calls send() on source chain OFT contract
LayerZero Decentralized Verifier Network (DVN) relays message
Destination chain OFT mints equivalent USDT0
User receives USDT0 on destination chain

Quick Start

Using @t402/evm (Direct)

import { Usdt0Bridge, LayerZeroScanClient } from '@t402/evm'
 
// Create bridge client
const bridge = new Usdt0Bridge(signer, 'arbitrum')
 
// Get quote
const quote = await bridge.quote({
  fromChain: 'arbitrum',
  toChain: 'ethereum',
  amount: 100_000000n, // 100 USDT0
  recipient: '0x...'
})
 
console.log('Fee:', quote.nativeFee, 'wei')
 
// Execute bridge
const result = await bridge.send({
  fromChain: 'arbitrum',
  toChain: 'ethereum',
  amount: 100_000000n,
  recipient: '0x...'
})
 
console.log('TX:', result.txHash)
console.log('Message GUID:', result.messageGuid)
 
// Track delivery
const scanClient = new LayerZeroScanClient()
const message = await scanClient.waitForDelivery(result.messageGuid, {
  onStatusChange: (status) => console.log('Status:', status)
})
 
console.log('Delivered! Dest TX:', message.dstTxHash)

Using @t402/wdk-bridge (WDK Integration)

import { WdkBridgeClient } from '@t402/wdk-bridge'
 
// Create client with multiple WDK accounts
const bridge = new WdkBridgeClient({
  accounts: {
    ethereum: ethereumAccount,
    arbitrum: arbitrumAccount
  },
  defaultStrategy: 'cheapest'
})
 
// Auto-select best source chain
const result = await bridge.autoBridge({
  toChain: 'ethereum',
  amount: 100_000000n,
  recipient: '0x...'
})
 
console.log('Bridging from:', result.fromChain)
 
// Wait for delivery
const delivery = await result.waitForDelivery()
console.log('Done!', delivery.dstTxHash)

Supported Routes

From	To	Fee (approx)	Time
Ethereum	Arbitrum	~$2-5	~3 min
Arbitrum	Ethereum	~$2-5	~15 min
Arbitrum	Ink	~$1-3	~5 min
Any L2	Any L2	~$1-3	~5 min

LayerZero Scan

Track messages using the LayerZero Scan API:

import { LayerZeroScanClient } from '@t402/evm'
 
const client = new LayerZeroScanClient()
 
// Get message status
const message = await client.getMessage(messageGuid)
console.log('Status:', message.status)
// INFLIGHT | CONFIRMING | DELIVERED | FAILED | BLOCKED
 
// Get messages by wallet
const messages = await client.getMessagesByWallet('0x...', 10)

Message Statuses

Status	Description
`INFLIGHT`	Message sent, in transit
`CONFIRMING`	Awaiting DVN confirmations
`DELIVERED`	Successfully delivered
`FAILED`	Delivery failed
`BLOCKED`	Blocked by DVN security

Route Selection Strategies

When using @t402/wdk-bridge:

Cheapest (Default)

Select route with lowest native fee:

const bridge = new WdkBridgeClient({
  accounts: { ... },
  defaultStrategy: 'cheapest'
})

Fastest

Select route with fastest estimated delivery:

const bridge = new WdkBridgeClient({
  accounts: { ... },
  defaultStrategy: 'fastest'
})

Preferred

Use specific source chain if available:

const result = await bridge.autoBridge({
  toChain: 'ethereum',
  amount: 100_000000n,
  recipient: '0x...',
  preferredSourceChain: 'arbitrum'
})

Fee Estimation

// Get quote without executing
const quote = await bridge.quote({
  fromChain: 'arbitrum',
  toChain: 'ethereum',
  amount: 100_000000n,
  recipient: '0x...'
})
 
console.log('Native fee:', quote.nativeFee, 'wei')
console.log('Amount to receive:', quote.minAmountToReceive)
console.log('Estimated time:', quote.estimatedTime, 'seconds')

Slippage Protection

Set maximum slippage tolerance:

const result = await bridge.send({
  fromChain: 'arbitrum',
  toChain: 'ethereum',
  amount: 100_000000n,
  recipient: '0x...',
  slippageTolerance: 0.5 // 0.5%
})

USDT0 Contract Addresses

Chain	Address
Ethereum	`0x6C96dE32CEa08842dcc4058c14d3aaAD7Fa41dee`
Arbitrum	`0xFd086bC7CD5C481DCC9C85ebE478A1C0b69FCbb9`
Ink	`0x0200C29006150606B650577BBE7B6248F58470c1`
Berachain	`0x779Ded0c9e1022225f8E0630b35a9b54bE713736`
Unichain	`0x588ce4F028D8e7B53B687865d6A67b3A54C75518`

LayerZero Endpoint IDs

Chain	Endpoint ID
Ethereum	30101
Arbitrum	30110
Ink	30291
Berachain	30362
Unichain	30320

Error Handling

import { BridgeError, InsufficientBalanceError } from '@t402/evm'
 
try {
  await bridge.send({ ... })
} catch (error) {
  if (error instanceof InsufficientBalanceError) {
    console.log('Need more USDT0:', error.required)
  } else if (error instanceof BridgeError) {
    console.log('Bridge failed:', error.message)
  }
}

Best Practices

Always get a quote first to show users the fee
Set appropriate slippage for volatile periods
Monitor delivery with LayerZero Scan
Handle stuck messages with manual retry
Keep native tokens for gas on source chain

Gasless Payments MCP Integration