YieldGarden — Stake SEED tokens, earn ETH rewards per second

Stake any amount of SEED tokens. The longer you hold, the more ETH you earn — rewards accrue every second, proportional to your stake.

🔗 Live demo: https://yield-garden-b7.netlify.app 📜 Contracts (Sepolia): SeedToken · YieldGarden

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What it does

• Users stake SEED tokens (any amount) into the garden.
• ETH rewards accrue every second, proportional to the staked amount and time.
• Users can check pending rewards without spending gas via pendingRewards().
• Users can claim rewards at any time without unstaking.
• Or they can unstake and receive tokens + accumulated rewards in one transaction.
• The owner funds the reward pool by sending ETH to the contract and can update the reward rate.

How it works

flowchart LR
    Owner -->|fund ETH pool| Garden[YieldGarden.sol]
    Owner -->|setRewardRate| Garden
    User -->|approve + stake SEED| Garden
    Garden -->|tracks amount + timestamp| State[(StakeInfo)]
    User -->|pendingRewards view| Garden
    Garden -->|returns accrued ETH| User
    User -->|claimRewards| Garden
    Garden -->|CEI → sends ETH| User
    User -->|unstake| Garden
    Garden -->|returns SEED + rewards| User

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Tech stack

Layer	Tech
Smart contracts	Solidity 0.8.24 (SeedToken + YieldGarden)
Standards	OpenZeppelin ERC20, Ownable
Dev / testing	Foundry (forge, anvil) + fuzz testing
Frontend	Next.js + wagmi + viem + RainbowKit
Network	Ethereum Sepolia testnet

Key design decisions

Rate expressed as wei per whole token per second The rate divides by 1e18 so the owner can set human-readable values (e.g., 1 = 1 wei reward per 1 SEED per second). This avoids the scale mismatch between ERC20 token units (18 decimals) and ETH wei.

pendingRewards() view function Users can preview exactly how much ETH they've earned before deciding to claim or unstake. Same UX pattern as DeFi vaults (ERC-4626 previewWithdraw).

stakedAt reset on claim (checkpoint model) Instead of tracking cumulative debt, we reset the stakedAt timestamp to block.timestamp on each claim. Simple, gas-efficient, and avoids integer overflow in long-running staking positions.

CEI pattern throughout State is cleared before all ETH transfers in both claimRewards and unstake — a malicious receiver cannot re-enter and double-claim rewards.

Testing ⭐

forge test -vvv

20 tests covering:

• ✅ Stake records amount and timestamp
• ✅ Reverts: zero amount, already staking
• ✅ pendingRewards returns 0 before staking
• ✅ Rewards accrue linearly over time
• ✅ Rewards proportional to staked amount
• ✅ claimRewards sends correct ETH
• ✅ claimRewards resets accrual checkpoint
• ✅ Reverts: no rewards yet, not staking, insufficient pool
• ✅ unstake returns tokens and pays pending rewards
• ✅ unstake clears state correctly
• ✅ Owner can update reward rate
• ✅ Non-owner cannot update rate
• ✅ Fuzz: 1000 random time durations — rewards always linear

Run locally

forge build
forge test -vvv

cp .env.example .env
# fill in SEPOLIA_RPC_URL and PRIVATE_KEY
source .env && forge script script/Deploy.s.sol \
  --rpc-url $SEPOLIA_RPC_URL --private-key $PRIVATE_KEY --broadcast

What I learned

The hardest part was the decimal mismatch: ERC20 tokens have 18 decimals, so staking 100 tokens means 100e18 units. Without dividing by 1e18 in the reward formula, the math overflows and the reward pool drains instantly. This is a real bug in production protocols — most DeFi staking contracts normalize amounts before computing rates. The stakedAt checkpoint model also taught me that you don't always need complex debt accounting — resetting a timestamp is often enough to track incremental claims.

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Contact

Armando Ochoa · Smart Contract Developer 📧 armaochoa99@gmail.com · Open to Web3 opportunities.

Built as part of my blockchain developer journey.