Stratus

What we built

Stratus: a three-primitive DeFi suite on IOPN testnet, plus a unified dApp that composes them.

• Lending: single-asset borrow/lend pool for native OPN. Fixed 5% APR via a Compound-style global borrowIndex. 75% LTV, 80% liquidation threshold, 50% close factor, 5% liquidator bonus.
• Swap: UniV2-style constant-product AMM for native OPN ↔ mUSDC. 0.30% fee, ERC20 LP token (OSP-LP), MINIMUM_LIQUIDITY locked on first mint, reentrancy-safe native transfers.
• Strategy: Leveraged LP composer that turns four cross-protocol calls into one guided flow. Deposit OPN as collateral, borrow OPN against it, pair the borrowed OPN with mUSDC, add liquidity to the OpenSwap pool. All orchestrated client-side, no router contract.

Why

DeFi on a new chain usually ships as isolated primitives that never talk to each other. Stratus ships the primitives and the composition layer in the same repo, so the value is more useful than the sum: a single panel turns four cross-protocol calls into one guided position open.

The brief also asked for something a builder community could actually fork. Each contract is small (one file, no proxies, no external deps beyond OpenZeppelin v5), verified on the IOPN explorer, and ships with full tests. The frontend lives in its own directory with bundled ABIs and env-var addresses, so it deploys standalone on Vercel with zero modifications, and the IOPN builder community gets a working reference for borrow/lend, AMM, and cross-protocol composition.

How it works

Lending: lazy linear interest accrual against a 1e18-scaled borrowIndex. Each user action touches accrueInterest first, then updates per-user principal at the new index. Health Factor = (collateral × LT) / debt, exposed via view function for the UI.

Swap: classic x * y = k with sqrt bootstrap and uint112 packed reserves. Native OPN handled via msg.value on swapExactOPNForToken / addLiquidity, with payable and explicit refund of dust. sync and skim included.

Strategy (Leveraged LP): client-side state machine drives four signed transactions in sequence. LTV slider clamps at 70%, five points below the protocol's 75% cap, so the user can never accidentally open at the edge. The panel previews resulting Health Factor, required mUSDC, and expected LP shares before the first signature. A per-step status list shows live progress (deposit, borrow, approve mUSDC, addLiquidity) with explorer links on each receipt.

dApp: three sidebar sections (Lending, Trade, Strategy) with eleven flat routes via hash-based navigation. Wallet connect through RainbowKit (MetaMask, OKX, WalletConnect). Disconnected users land on a hero screen with a Connect CTA. The History view reads events through the IOPN explorer API in a single HTTP call, no chunked eth_getLogs spam. Light theme, Lucide icons, mobile drawer.

Stack & status

Solidity 0.8.24, Hardhat, TypeScript, OpenZeppelin v5. Frontend on Next.js 14 (App Router), wagmi v2, viem v2, RainbowKit, TanStack Query, Tailwind. Tests: 73/73 passing, 100% lines on LendingPool, 98% on OpenSwapPair.

Verified on IOPN testnet (chainId 984):

• LendingPool: 0x55E64b4786966219fb1501094472D356046F864F
• OpenSwapPair: 0x4A5d5Ea0bE6ac98682D28526F02217e6Fc977B12
• MockUSDC: 0xFFff7761b5e662D26C7C51C9F80f1324F5e43c00