Flash loan funded Cross-Chain Arbitrage Scanner

A production-grade TypeScript bot that monitors the WETH/LINK price across three DEXs on three different EVM chains simultaneously. When a profitable spread is found (after deducting real on-chain gas and bridging costs), it optionally executes an Aave V3 flash-loan-funded trade via a custom Solidity smart contract.

Architecture

src/
├── index.ts          Main polling loop — orchestrates everything
├── config.ts         All contract addresses, ABIs, and bot settings
├── types.ts          TypeScript interfaces (PriceQuote, ArbitrageOpportunity …)
├── scanner.ts        Fetches live quotes from Uniswap V3, Camelot V3, Aerodrome
├── priceFeed.ts      Fetches ETH/USD + LINK/USD from CoinGecko (with caching)
├── gasEstimator.ts   Queries on-chain gas prices, converts to real USD cost
├── executor.ts       Signs and sends the flash loan transaction to the contract
├── alerts.ts         Sends Telegram notifications on profitable opportunities
└── logger.ts         Colorized terminal + file logging (logs/ directory)

contracts/
└── FlashLoanArb.sol  Aave V3 flash loan contract (deploy on Ethereum mainnet)

logs/
├── arb-scanner.log   Full plain-text log of every scan
└── opportunities.json  JSON log of every profitable opportunity detected

Supported DEXs

DEX	Chain	Protocol
Uniswap V3	Ethereum	Concentrated liquidity (0.3% fee tier)
Camelot V3	Arbitrum	Algebra dynamic-fee AMM
Aerodrome	Base	Solidly volatile AMM

Prerequisites

• Node.js 18+
• RPC URLs for Ethereum, Arbitrum, and Base (free tier at Alchemy)
• (Optional) A deployed FlashLoanArb.sol contract and a funded wallet for live mode

Quick Start

# 1. Install dependencies
npm install

# 2. Copy and configure environment variables
cp .env.example .env
#    → Add your RPC URLs (required)
#    → Add PRIVATE_KEY + ARB_CONTRACT_ADDRESS only if running LIVE

# 3. Start in safe dry-run mode (scans only, no real transactions)
npm run start:dry

# 4. Or start live (requires contract deployed + wallet funded)
npm start

How It Works

1. Price Scanning — Every 12 seconds the bot queries the on-chain quoter/router contracts for all three DEXs simultaneously using ethers.js.
2. Gas Estimation — getFeeData() is called on each chain provider. The result is multiplied by estimated gas units and the live ETH/USD price from CoinGecko.
3. Spread Calculation — The bot checks every pair of DEXs (6 combinations). For each pair it calculates:

   Net Profit = (sell_LINK - buy_LINK) × LINK_USD - gas_buy - gas_sell - bridge_fee
   

4. Threshold Check — If Net Profit > MIN_PROFIT_USD, the opportunity is logged and an alert is sent via Telegram.
5. Execution — If DRY_RUN=false and ARB_CONTRACT_ADDRESS is set, the bot calls requestFlashLoanArb() on the deployed Solidity contract.

Smart Contract (FlashLoanArb.sol)

The contract uses Aave V3 Simple Flash Loans (no Aave collateral required):

requestFlashLoanArb()
    └── aavePool.flashLoanSimple()
            └── executeOperation() [Aave callback]
                    ├── buy LINK on cheapest router  (exactInputSingle)
                    ├── sell LINK on expensive router (exactInputSingle)
                    ├── repay Aave principal + 0.05% premium
                    └── keep the profit in the contract

Deploy with Remix

1. Open remix.ethereum.org
2. Paste contracts/FlashLoanArb.sol
3. Compile with Solidity 0.8.20
4. Deploy on Ethereum mainnet with MetaMask
5. Copy the deployed address into .env as ARB_CONTRACT_ADDRESS

Configuration Reference

Variable	Default	Description
ETH_RPC_URL	Public Ankr	Ethereum JSON-RPC endpoint
ARB_RPC_URL	Public Arb	Arbitrum JSON-RPC endpoint
BASE_RPC_URL	Public Base	Base JSON-RPC endpoint
DRY_RUN	true	Scan only — no transactions sent
MIN_PROFIT_USD	30	Minimum net profit to trigger execution
PRIVATE_KEY	—	Wallet private key (live mode only)
ARB_CONTRACT_ADDRESS	—	Deployed FlashLoanArb.sol address
TELEGRAM_BOT_TOKEN	—	Optional Telegram bot token
TELEGRAM_CHAT_ID	—	Optional Telegram chat ID

Terminal Output Example

  ╔══════════════════════════════════════╗
  ║   Cross-Chain Arbitrage Scanner      ║
  ║   Uniswap · Camelot · Aerodrome      ║
  ╚══════════════════════════════════════╝

[2024-04-18T10:00:00.000Z] INFO   Mode: DRY RUN
[2024-04-18T10:00:00.000Z] INFO   Min profit: $30
──────────────────────────────────────────────────────────────────────
[2024-04-18T10:00:01.000Z] INFO   Market prices refreshed — ETH $3121.00  LINK $18.4200
[2024-04-18T10:00:02.000Z] INFO   Gas costs — ETH $14.87  ARB $0.021  BASE $0.004
[2024-04-18T10:00:04.000Z] PRICES  Uniswap=185.1023 LINK  Camelot=184.2001 LINK  Aerodrome=186.5042 LINK

  Buy  ▶  Camelot V3 (Arbitrum) — 184.2001 LINK
  Sell ▶  Aerodrome (Base)      — 186.5042 LINK
  Spread  2.3041 LINK  ($42.43)
  Gas+Bridge  -$10.22  (cross-chain)
  Net Profit  ($32.21)

[2024-04-18T10:00:04.000Z]  ARB   PROFITABLE ARB FOUND! $32.21 net — executing...
[2024-04-18T10:00:04.000Z]  ARB   [DRY-RUN] Would execute arb. Est. profit $32.21

Important Notes

• Cross-chain flash loans are not atomically possible. The scanner detects cross-chain spreads, but the executor currently only sends same-chain flash loan transactions. For cross-chain execution, pre-funded capital on each chain is required.
• Use Alchemy or Infura RPC URLs — public endpoints have aggressive rate limits that will cause missed scan ticks.
• Always run in DRY_RUN=true mode first to verify the spread logic before going live.

Disclaimer

This software is for educational purposes only. Arbitrage is highly competitive. On-chain transactions can fail or be front-run. Never invest more than you can afford to lose.