LendProtocol

A decentralised lending protocol built on Ethereum. Deposit WETH as collateral, borrow USDC at 10% APR, and manage your position through a clean on-chain UI.

What it does

Action	Description
Deposit	Lock WETH as collateral, receive iCOL receipt tokens 1:1
Borrow	Borrow USDC up to 80% of collateral USD value
Repay	Pay back USDC debt (interest accrues per-second at 10% APR)
Withdraw	Reclaim WETH collateral (health factor must stay ≥ 1)
Supply	Provide USDC liquidity to the pool
Liquidate	Repay an undercollateralised position and claim collateral + 5% bonus

Prices are fed by Chainlink ETH/USD with a staleness check (3-hour timeout). The protocol freezes if the feed goes stale rather than acting on bad data.

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Tech stack

Contracts

• Solidity ^0.8.24
• Foundry (forge, cast, anvil)
• OpenZeppelin v5 (IERC20, ERC20Mock)
• Chainlink AggregatorV3Interface

Frontend

• Next.js 14 (App Router)
• wagmi v2 + viem
• RainbowKit
• Tailwind CSS v4

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Project structure

lending-protocol/
├── contracts/                  # Foundry project
│   ├── src/
│   │   ├── LendingPool.sol
│   │   ├── InterestToken.sol
│   │   ├── interfaces/
│   │   │   └── AggregatorV3Interface.sol
│   │   ├── libraries/
│   │   │   └── OracleLib.sol
│   │   └── mocks/
│   │       └── MockV3Aggregator.sol
│   ├── script/
│   │   ├── Deploy.s.sol
│   │   └── HelperConfig.s.sol
│   ├── test/
│   │   └── LendingPoolTest.t.sol
│   └── foundry.toml
└── frontend/                   # Next.js project
    ├── src/
    │   ├── app/
    │   │   └── page.tsx
    │   ├── components/
    │   │   ├── ActionPanel.tsx
    │   │   └── PositionCard.tsx
    │   ├── hooks/
    │   │   └── useLendingPool.ts
    │   ├── contracts/
    │   │   ├── abis.ts
    │   │   └── addresses.json
    │   └── lib/
    │       └── wagmi.ts
    └── package.json

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Local development

Prerequisites

• Foundry — curl -L https://foundry.paradigm.xyz | bash && foundryup
• Node.js v18+
• MetaMask browser extension

1. Clone and install

git clone https://github.com/Ab-hai/lending-protocol.git
cd lending-protocol

Install contract dependencies:

cd contracts
forge install

Install frontend dependencies:

cd frontend
npm install

2. Run a local chain

anvil

Leave this running. Anvil starts at http://127.0.0.1:8545 with 10 funded accounts. The default account 0xf39Fd6... is what MetaMask uses when you add the Anvil network.

3. Deploy contracts

cd contracts
forge script script/Deploy.s.sol --rpc-url http://127.0.0.1:8545 --broadcast

The script:

• Deploys LendingPool, InterestToken, mock WETH, mock USDC, and MockV3Aggregator
• Seeds the pool with 500,000 USDC liquidity
• Mints 100 WETH + 10,000 USDC to Anvil accounts #0 and #1 for testing

Copy the printed contract addresses into frontend/src/contracts/addresses.json:

{
  "lendingPool": "0x...",
  "iToken":      "0x...",
  "weth":        "0x...",
  "usdc":        "0x..."
}

4. Configure MetaMask for Anvil

Add a custom network in MetaMask:

Field	Value
Network name	Anvil Local
RPC URL	http://127.0.0.1:8545
Chain ID	31337
Currency symbol	ETH

Import a test account using one of the private keys printed by anvil on startup. Account #0's key is always:

0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80

⚠️ Never use this key for anything other than local testing.

5. Start the frontend

cd frontend
npm run dev

Open http://localhost:3000.

6. Run tests

cd contracts
forge test -vv

Run with gas report:

forge test --gas-report

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Testnet deployment (Sepolia)

1. Get testnet ETH

Use any Sepolia faucet:

• https://sepoliafaucet.com
• https://faucet.quicknode.com/ethereum/sepolia
• Alchemy or Infura dashboards (free tier)

You need at least 0.1 ETH to cover deployment gas.

2. Set environment variables

Create contracts/.env:

PRIVATE_KEY=0xyour_deployer_private_key
SEPOLIA_RPC_URL=https://eth-sepolia.g.alchemy.com/v2/your_api_key
ETHERSCAN_API_KEY=your_etherscan_api_key

Get a free RPC URL from Alchemy or Infura.
Get an Etherscan API key from etherscan.io/myapikey (used for contract verification).

Load the variables:

source contracts/.env

3. Deploy to Sepolia

cd contracts
forge script script/Deploy.s.sol \
  --rpc-url $SEPOLIA_RPC_URL \
  --broadcast \
  --verify \
  --etherscan-api-key $ETHERSCAN_API_KEY

--verify uploads the source code to Etherscan automatically. After a minute you'll be able to read and write the contract directly on Etherscan.

4. Update frontend addresses

The deploy script prints all addresses. Paste them into frontend/src/contracts/addresses.json.

The Sepolia Chainlink ETH/USD feed (0x694AA1769357215DE4FAC081bf1f309aDC325306) and token addresses are already hardcoded in HelperConfig.s.sol — no changes needed there.

---

Contract addresses (Sepolia)

Contract	Address
LendingPool	0x...
InterestToken (iCOL)	0x...
WETH (Sepolia)	0xdd13E55209Fd76AfE204dBda4007C227904f0a81
USDC (Aave Sepolia)	0x94a9D9AC8a22534E3FaCa9F4e7F2E2cf85d5E4C8
ETH/USD Price Feed	0x694AA1769357215DE4FAC081bf1f309aDC325306

Update the first two rows after your Sepolia deployment.

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Protocol parameters

Parameter	Value
Collateral asset	WETH
Borrow asset	USDC
Loan-to-value (LTV)	80%
Liquidation threshold	90%
Liquidation bonus	5%
Borrow APR	10% (linear, per-second)
Oracle staleness timeout	3 hours

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Security notes

This is a learning project and has not been audited. Do not use it with real funds on mainnet.

Known limitations:

• Interest model is linear (not compound) — real protocols use compound interest
• Single collateral asset only
• No governance or upgradability
• Liquidity providers earn no yield (interest goes to the protocol, not tracked)

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Acknowledgements

• Cyfrin Updraft — DeFi course structure and DSCEngine patterns
• Chainlink — Price feed infrastructure
• OpenZeppelin — ERC20 standards