ArcLend

Aave-inspired DeFi lending & borrowing protocol on Arc Testnet — the stablecoin-native EVM L1 by Circle.

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Overview

ArcLend lets users:

• Supply USDC, EURC, or mARC to earn yield from borrowers
• Borrow against supplied collateral (up to the asset's LTV ratio)
• Repay debt and withdraw collateral at any time
• Liquidate undercollateralised positions (health factor < 1.0)
• Claim free testnet tokens from the built-in faucet
• Collect protocol fees (owner only) via the Admin dashboard
  • Earn composable yield via ERC-4626 vaults (alvUSDC / alvEURC) whose shares are transferable into any ERC-4626-aware protocol
  • Supply gasless — sign an EIP-3009 authorization off-chain and let a relayer pay the gas (zero-gas deposits)

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Live Contracts — Arc Testnet (Chain ID 5042002)

Contract	Address
LendingPool	0x7e6Ab8b26223e3f622E25f44c1840e6BD85e3de2
MockPriceOracle	0xc0Fe330c98Da23f5180d8Ee8B84b89422493B0Ac
Mock USDC	0xd36a5F89D1b67B6a925cbb06225eF5b17e17b855
Mock EURC	0xC38B3acb381E9B8Dd90266022Cca0AB9afc935c5
Mock mARC	0x844F39119e5f6CB8b727E538634a05F098cF842B

Integration Layer — deployed on top of the live pool (no core redeploy)

| Contract | Address |
|---|---|
| ArcLendGaslessRouter | `0xFE338289BA0f113933853759baD76B251932341a` |
| alvUSDC vault (ERC-4626) | `0x363C4eE3CfD814D3CC3bc72aCe4259453cF651EB` |
| alvEURC vault (ERC-4626) | `0xf9A7CD2c92CB6957ECeFffE2881c5Bd163a2CAeD` |

Block explorer: [testnet.arcscan.app](https://testnet.arcscan.app)

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Arc Testnet Details

Parameter	Value
Network Name	Arc Testnet
Chain ID	5042002
RPC URL	https://rpc.testnet.arc.network
Block Explorer	https://testnet.arcscan.app
Native Gas Token	USDC
Faucet	https://faucet.circle.com

Add this network to MetaMask manually or click Switch Network in the dApp — it will prompt MetaMask to add it automatically.

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Supported Assets

Asset	Symbol	Decimals	LTV	Liq. Threshold	Reserve Factor
USD Coin	USDC	6	85%	90%	10%
Euro Coin	EURC	6	85%	90%	10%
Mock ARC	mARC	18	60%	65%	20%

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Protocol Economics

Interest Rate Model (Jump Rate)

Each market uses a two-slope interest rate model with a kink at optimal utilization:

Utilization ≤ Optimal:  BorrowRate = BaseRate + Slope × Utilization
Utilization > Optimal:  BorrowRate = BaseRate + Slope × Optimal + ExcessSlope × (Util - Optimal)

Parameter	USDC / EURC	mARC
Base Rate	2%	3%
Slope	8%	10%
Optimal Utilization	80%	70%
Excess Slope	100%	150%

Supply APY = BorrowRate × Utilization × (1 − ReserveFactor)

Protocol Fees

A configurable protocol fee (default 0.30%, capped at 2%) is deducted from every supply, borrow, and withdraw. Fees accumulate in protocolReserves per market and can be collected by the contract owner at any time via the Admin page.

Health Factor & Liquidation

HealthFactor = Σ(CollateralUSD × LiquidationThreshold) / TotalDebtUSD

• HealthFactor < 1.0 → position is liquidatable
• Liquidators may repay up to 50% of debt per call and receive collateral + bonus

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Getting Started

Prerequisites

• Node.js 20+
• pnpm (npm install -g pnpm)
• MetaMask browser extension
• Testnet USDC for gas from faucet.circle.com

Run Locally

# Clone
git clone https://github.com/osr21/arclend.git
cd arclend

# Install all workspace dependencies
pnpm install

# Start the frontend dApp (http://localhost:24455)
pnpm --filter @workspace/arc-lend run dev

# (Optional) Start the API server
pnpm --filter @workspace/api-server run dev

Open your browser, connect MetaMask to Arc Testnet, and use the Faucet page to claim testnet tokens.

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Smart Contracts

Compile

cd contracts
npm install
npm run compile

Deploy to Arc Testnet

# Set your deployer private key
export PRIVATE_KEY=0x...

cd contracts
npm run deploy:testnet

After deployment, copy the printed addresses and set them as environment variables in the frontend:

VITE_LENDING_POOL_ADDRESS=0x...
VITE_ORACLE_ADDRESS=0x...
VITE_USDC_ADDRESS=0x...
VITE_EURC_ADDRESS=0x...
VITE_MARC_ADDRESS=0x...

Deploy to Local Hardhat Node

# Terminal 1 — start local node
cd contracts && npx hardhat node

# Terminal 2 — deploy
cd contracts && npm run deploy:local

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Project Structure

arclend/
├── artifacts/
│   ├── arc-lend/              # React + Vite frontend dApp
│   │   ├── src/
│   │   │   ├── abi/           # Contract ABIs (LendingPool, MockERC20, MockPriceOracle)
│   │   │   ├── components/    # UI components (Header, ActionModal, WalletMenu…)
│   │   │   ├── hooks/         # useWallet, useMarkets, useUserData
│   │   │   ├── lib/           # web3.ts, contracts.ts, constants.ts
│   │   │   └── pages/         # Dashboard, Markets, Portfolio, Vaults, Faucet, Admin
│   └── api-server/            # Express 5 API server (future backend features)
├── contracts/
│   ├── src/
│   │   ├── LendingPool.sol    # Core protocol
│   │   ├── MockERC20.sol      # Mintable test token with faucet
│   │   ├── MockPriceOracle.sol
  │   │   ├── ArcLendVault.sol   # ERC-4626 vault wrapper (composable shares)
  │   │   └── ArcLendGaslessRouter.sol  # EIP-3009 gasless supply relayer target
│   ├── scripts/deploy.js      # Hardhat deployment script
│   └── hardhat.config.js
└── lib/                       # Shared TypeScript libraries

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Tech Stack

Layer	Technology
Frontend	React 19, Vite, Tailwind CSS v4, shadcn/ui, Framer Motion
Web3	ethers.js v6 (no wagmi — direct ethers)
Routing	wouter
Contracts	Solidity 0.8.24, Hardhat, OpenZeppelin
Monorepo	pnpm workspaces, TypeScript 5.9
API	Express 5, PostgreSQL, Drizzle ORM

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Pages

Page	Path	Description
Dashboard	/	Protocol TVL, total supplied/borrowed, user portfolio summary
Markets	/markets	Per-asset supply APY, borrow APY, utilization, LTV — supply/borrow actions
Portfolio	/portfolio	User positions, health factor, earned interest, wallet balances
Faucet	/faucet	One-click testnet token minting for USDC, EURC, mARC
Admin	/admin	Owner-only: fee configuration, fee collector address, reserve collection

| Vaults | `/vaults` | ERC-4626 vaults (alvUSDC / alvEURC) — deposit/withdraw, share price, gasless deposit via EIP-3009 |

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Admin & Fee Management

The Admin page at /admin is only visible to the contract owner (the wallet that deployed the contracts). It allows:

• Viewing the current protocol fee (default 0.30%)
• Updating the fee (0–200 bps, enforced on-chain)
• Changing the fee collector address
• Viewing and collecting accumulated protocol reserves per market

Owner verification is done on-chain — the page reads owner() directly from the LendingPool contract and compares it to the connected wallet.

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Security Notes

• All state-changing functions use OpenZeppelin ReentrancyGuard
• Token transfers use OpenZeppelin SafeERC20
• Owner functions protected by OpenZeppelin Ownable
• Protocol fee is hard-capped at 2% in the contract (MAX_PROTOCOL_FEE = 200)
• Health factor is checked before every borrow and withdrawal
• Oracle is a mock (centralised) — suitable for testnet only

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License

MIT — see LICENSE