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LayerZero

BOB Gateway's LayerZero integration enables seamless cross-chain swaps between Bitcoin and LayerZero-supported chains. All transactions route through BOB as an intermediary, leveraging LayerZero's Omnichain Fungible Token (OFT) protocol for secure cross-chain bridging.

High-Level Developer Overview​

How It Works​

The LayerZero Gateway Client routes all cross-chain transactions through BOB, acting as the hub for LayerZero connectivity:

Bitcoin → LayerZero Chain Flow​

  1. Bitcoin → BOB: User sends Bitcoin, receives wBTC on BOB via Gateway
  2. BOB → Target Chain: wBTC is bridged via LayerZero OFT to destination chain
  3. Strategy Execution: BOB strategy contract handles the LayerZero bridging automatically

LayerZero Chain → Bitcoin Flow​

  1. Origin Chain → BOB: User's tokens are bridged to BOB via LayerZero
  2. BOB Processing: Offramp composer creates Bitcoin withdrawal order
  3. BOB → Bitcoin: Standard Gateway offramp process completes the swap

Supported Chains​

The LayerZero integration supports 15+ major EVM chains including Ethereum, Base, Arbitrum, Avalanche, BSC, and more.

Get Quote​

Get a quote for cross-chain swaps via LayerZero:

import { LayerZeroGatewayClient, parseBtc } from '@gobob/bob-sdk';
import { bob } from 'viem/chains';

const client = new LayerZeroGatewayClient(bob.id);

// Bitcoin → Base example
const onrampQuote = await client.getQuote({
    fromChain: 'bitcoin',
    fromToken: 'BTC', 
    toChain: 'base',
    toToken: '0x0555E30da8f98308EdB960aa94C0Db47230d2B9c', // wBTC
    fromUserAddress: 'bc1q...', // Bitcoin address
    toUserAddress: '0x...', // EVM address on destination chain
    amount: parseBtc("0.1"), // BTC
    l0FeeBuffer: 500 // 5% LayerZero fee buffer (optional)
});

// Base → Bitcoin example
const offrampQuote = await client.getQuote({
    fromChain: 'base',
    fromToken: '0x0555E30da8f98308EdB960aa94C0Db47230d2b9c', // wBTC
    toChain: 'bitcoin',
    toToken: 'BTC',
    fromUserAddress: '0x...', // EVM address on origin chain
    toUserAddress: 'bc1q...', // Bitcoin address
    amount: 17000 // token amount in smallest unit
});

Execute Quote​

Execute the cross-chain swap:

import { createPublicClient, createWalletClient, http } from 'viem';
import { base } from 'viem/chains';

// Setup clients for the origin chain
const publicClient = createPublicClient({
    chain: base, // Origin chain
    transport: http()
});

const walletClient = createWalletClient({
    chain: base,
    transport: http(),
    account: yourAccount
});

// Execute the quote
const txHash = await client.executeQuote({
    quote,
    walletClient,
    publicClient,
    btcSigner // Only required for Bitcoin → EVM onramp
});

console.log('Transaction hash:', txHash);

Architecture & Smart Contracts​

BOB Hub Architecture​

All LayerZero operations route through BOB:

  • BOB Strategy Contract: 0x5Fd9B934c219663C7f4f432f39682be2dC42eDC7

    • Handles Bitcoin → LayerZero bridging
    • Swaps portion of wBTC to ETH for LayerZero fees
    • Executes LayerZero send() with proper parameters

  • Offramp Composer: 0xc05AA3D7BD9c61B8b94EaCC937d1F542c3E5b94a

    • Receives LayerZero → BOB transfers
    • Creates Gateway offramp orders for Bitcoin withdrawal

wBTC OFT Standard​

LayerZero uses standardized wBTC OFT contracts across supported chains:

  • Address: 0x0555e30da8f98308edb960aa94c0db47230d2b9c (most chains)
  • Exception: Optimism uses 0xc3f854b2970f8727d28527ece33176fac67fef48