---
name: defi-protocol-templates
description: "Implement DeFi protocols with educational templates for staking, AMMs, governance, and lending systems. Use when building decentralized finance applications or smart contract protocols."
risk: critical
source: community
date_added: "2026-02-27"
---
## Supporting material availability

This catalog copy contains the inline guidance below, but does not include the following supporting paths. They are external prerequisites, not bundled files:

- `<support-root>/references/staking.md`
- `<support-root>/references/liquidity-pools.md`
- `<support-root>/references/governance-tokens.md`
- `<support-root>/references/lending-protocols.md`
- `<support-root>/references/flash-loans.md`
- `<support-root>/assets/staking-contract.sol`
- `<support-root>/assets/amm-contract.sol`
- `<support-root>/assets/governance-token.sol`
- `<support-root>/assets/lending-protocol.sol`

Ask for the original supporting material or an existing installation before using a step that depends on these paths; this catalog does not identify a verified download source for them. Resolve each path relative to that installation, inspect its contents, and verify any applicable license and execution prerequisites. Do not run a command or claim a referenced procedure was followed until its required file exists. Do not fabricate the missing scripts or treat an unrelated file with the same name as equivalent. Independent steps fully documented here can proceed within the user’s authorized scope; report any dependent step as unavailable.


# DeFi Protocol Templates

Educational examples for common DeFi protocols including staking, AMMs, governance, lending, and flash loans.

## Do not use this skill when

- The task is unrelated to defi protocol templates
- You need a different domain or tool outside this scope

## Instructions

- Clarify goals, constraints, and required inputs.
- Apply relevant best practices and validate outcomes.
- Provide actionable steps and verification.

## Use this skill when

- Building staking platforms with reward distribution
- Implementing AMM (Automated Market Maker) protocols
- Creating governance token systems
- Developing lending/borrowing protocols
- Integrating flash loan functionality
- Launching yield farming platforms

These inline contracts are incomplete teaching examples, not audited/funded protocols. They use OpenZeppelin4.x import/inheritance APIs; pin a reviewed compatible version rather than installing5.x blindly. Never deploy with user funds. Staking’s fixed unbounded reward rate has no funding/period management; AMM lacks production-grade reserve/oracle/LP safeguards; governor has no quorum/timelock/action payload; flash loans require a receiver-specific trusted callback. Compile, property/fuzz-test accounting/reentrancy/rounding and obtain independent review before designing a deployment. Token units/decimals differ and fee-on-transfer/rebasing tokens are unsupported.

## Staking Contract

```solidity
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
contract StakingRewards is ReentrancyGuard, Ownable {
    using SafeERC20 for IERC20;
    IERC20 public stakingToken;
    IERC20 public rewardsToken;
    uint256 public rewardRate = 100; // Rewards per second
    uint256 public lastUpdateTime;
    uint256 public rewardPerTokenStored;
    mapping(address => uint256) public userRewardPerTokenPaid;
    mapping(address => uint256) public rewards;
    mapping(address => uint256) public balances;
    uint256 private _totalSupply;
    event Staked(address indexed user, uint256 amount);
    event Withdrawn(address indexed user, uint256 amount);
    event RewardPaid(address indexed user, uint256 reward);
    constructor(address _stakingToken, address _rewardsToken) {
        stakingToken = IERC20(_stakingToken);
        rewardsToken = IERC20(_rewardsToken);
    }
    modifier updateReward(address account) {
        rewardPerTokenStored = rewardPerToken();
        lastUpdateTime = block.timestamp;
        if (account != address(0)) {
            rewards[account] = earned(account);
            userRewardPerTokenPaid[account] = rewardPerTokenStored;
        }
        _;
    }
    function rewardPerToken() public view returns (uint256) {
        if (_totalSupply == 0) {
            return rewardPerTokenStored;
        }
        return rewardPerTokenStored +
            ((block.timestamp - lastUpdateTime) * rewardRate * 1e18) / _totalSupply;
    }
    function earned(address account) public view returns (uint256) {
        return (balances[account] *
            (rewardPerToken() - userRewardPerTokenPaid[account])) / 1e18 +
            rewards[account];
    }
    function stake(uint256 amount) external nonReentrant updateReward(msg.sender) {
        require(amount > 0, "Cannot stake 0");
        _totalSupply += amount;
        balances[msg.sender] += amount;
        stakingToken.safeTransferFrom(msg.sender, address(this), amount);
        emit Staked(msg.sender, amount);
    }
    function withdraw(uint256 amount) public nonReentrant updateReward(msg.sender) {
        require(amount > 0, "Cannot withdraw 0");
        _totalSupply -= amount;
        balances[msg.sender] -= amount;
        stakingToken.safeTransfer(msg.sender, amount);
        emit Withdrawn(msg.sender, amount);
    }
    function getReward() public nonReentrant updateReward(msg.sender) {
        uint256 reward = rewards[msg.sender];
        if (reward > 0) {
            rewards[msg.sender] = 0;
            rewardsToken.safeTransfer(msg.sender, reward);
            emit RewardPaid(msg.sender, reward);
        }
    }
    function exit() external {
        withdraw(balances[msg.sender]);
        getReward();
    }
}
```

## AMM (Automated Market Maker)

```solidity
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
contract SimpleAMM is ReentrancyGuard {
    using SafeERC20 for IERC20;
    IERC20 public token0;
    IERC20 public token1;
    uint256 public reserve0;
    uint256 public reserve1;
    uint256 public totalSupply;
    mapping(address => uint256) public balanceOf;

    event Mint(address indexed to, uint256 amount);
    event Burn(address indexed from, uint256 amount);
    event Swap(address indexed trader, uint256 amount0In, uint256 amount1In, uint256 amount0Out, uint256 amount1Out);

    constructor(address _token0, address _token1) {
        token0 = IERC20(_token0);
        token1 = IERC20(_token1);
    }

    function addLiquidity(uint256 amount0, uint256 amount1) external nonReentrant returns (uint256 shares) {
        token0.safeTransferFrom(msg.sender, address(this), amount0);
        token1.safeTransferFrom(msg.sender, address(this), amount1);

        if (totalSupply == 0) {
            shares = sqrt(amount0 * amount1);
        } else {
            shares = min(
                (amount0 * totalSupply) / reserve0,
                (amount1 * totalSupply) / reserve1
            );
        }

        require(shares > 0, "Shares = 0");
        _mint(msg.sender, shares);
        _update(
            token0.balanceOf(address(this)),
            token1.balanceOf(address(this))
        );

        emit Mint(msg.sender, shares);
    }

    function removeLiquidity(uint256 shares) external nonReentrant returns (uint256 amount0, uint256 amount1) {
        uint256 bal0 = token0.balanceOf(address(this));
        uint256 bal1 = token1.balanceOf(address(this));

        amount0 = (shares * bal0) / totalSupply;
        amount1 = (shares * bal1) / totalSupply;

        require(amount0 > 0 && amount1 > 0, "Amount0 or amount1 = 0");

        _burn(msg.sender, shares);
        _update(bal0 - amount0, bal1 - amount1);

        token0.safeTransfer(msg.sender, amount0);
        token1.safeTransfer(msg.sender, amount1);

        emit Burn(msg.sender, shares);
    }

    function swap(address tokenIn, uint256 amountIn, uint256 minAmountOut, uint256 deadline) external nonReentrant returns (uint256 amountOut) {
        require(block.timestamp <= deadline && amountIn > 0, "Expired or zero input");
        require(tokenIn == address(token0) || tokenIn == address(token1), "Invalid token");

        bool isToken0 = tokenIn == address(token0);
        (IERC20 tokenIn_, IERC20 tokenOut, uint256 resIn, uint256 resOut) = isToken0
            ? (token0, token1, reserve0, reserve1)
            : (token1, token0, reserve1, reserve0);

        tokenIn_.safeTransferFrom(msg.sender, address(this), amountIn);

        // 0.3% fee
        uint256 amountInWithFee = (amountIn * 997) / 1000;
        amountOut = (resOut * amountInWithFee) / (resIn + amountInWithFee);

        require(amountOut >= minAmountOut && amountOut > 0, "Slippage or zero output");
        tokenOut.safeTransfer(msg.sender, amountOut);

        _update(
            token0.balanceOf(address(this)),
            token1.balanceOf(address(this))
        );

        emit Swap(msg.sender, isToken0 ? amountIn : 0, isToken0 ? 0 : amountIn, isToken0 ? 0 : amountOut, isToken0 ? amountOut : 0);
    }

    function _mint(address to, uint256 amount) private {
        balanceOf[to] += amount;
        totalSupply += amount;
    }

    function _burn(address from, uint256 amount) private {
        balanceOf[from] -= amount;
        totalSupply -= amount;
    }

    function _update(uint256 res0, uint256 res1) private {
        reserve0 = res0;
        reserve1 = res1;
    }

    function sqrt(uint256 y) private pure returns (uint256 z) {
        if (y > 3) {
            z = y;
            uint256 x = y / 2 + 1;
            while (x < z) {
                z = x;
                x = (y / x + x) / 2;
            }
        } else if (y != 0) {
            z = 1;
        }
    }

    function min(uint256 x, uint256 y) private pure returns (uint256) {
        return x <= y ? x : y;
    }
}
```

## Governance Token

```solidity
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Votes.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

contract GovernanceToken is ERC20Votes, Ownable {
    constructor() ERC20("Governance Token", "GOV") ERC20Permit("Governance Token") {
        _mint(msg.sender, 1000000 * 10**decimals());
    }

    function _afterTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal override(ERC20Votes) {
        super._afterTokenTransfer(from, to, amount);
    }

    function _mint(address to, uint256 amount) internal override(ERC20Votes) {
        super._mint(to, amount);
    }

    function _burn(address account, uint256 amount) internal override(ERC20Votes) {
        super._burn(account, amount);
    }
}

contract Governor is Ownable {
    GovernanceToken public governanceToken;

    struct Proposal {
        uint256 id;
        address proposer;
        string description;
        uint256 forVotes;
        uint256 againstVotes;
        uint256 startBlock;
        uint256 endBlock;
        bool executed;
        mapping(address => bool) hasVoted;
    }

    uint256 public proposalCount;
    mapping(uint256 => Proposal) public proposals;

    uint256 public votingPeriod = 17280; // ~3 days in blocks
    uint256 public proposalThreshold = 100000 * 10**18;

    event ProposalCreated(uint256 indexed proposalId, address proposer, string description);
    event VoteCast(address indexed voter, uint256 indexed proposalId, bool support, uint256 weight);
    event ProposalExecuted(uint256 indexed proposalId);

    constructor(address _governanceToken) {
        governanceToken = GovernanceToken(_governanceToken);
    }

    function propose(string memory description) external returns (uint256) {
        require(
            governanceToken.getPastVotes(msg.sender, block.number - 1) >= proposalThreshold,
            "Proposer votes below threshold"
        );

        proposalCount++;
        Proposal storage newProposal = proposals[proposalCount];
        newProposal.id = proposalCount;
        newProposal.proposer = msg.sender;
        newProposal.description = description;
        newProposal.startBlock = block.number;
        newProposal.endBlock = block.number + votingPeriod;

        emit ProposalCreated(proposalCount, msg.sender, description);
        return proposalCount;
    }

    function vote(uint256 proposalId, bool support) external {
        Proposal storage proposal = proposals[proposalId];
        require(proposalId > 0 && proposalId <= proposalCount, "Unknown proposal");
        require(block.number > proposal.startBlock, "Snapshot not yet historical");
        require(block.number <= proposal.endBlock, "Voting ended");
        require(!proposal.hasVoted[msg.sender], "Already voted");

        uint256 weight = governanceToken.getPastVotes(msg.sender, proposal.startBlock);
        require(weight > 0, "No voting power");

        proposal.hasVoted[msg.sender] = true;

        if (support) {
            proposal.forVotes += weight;
        } else {
            proposal.againstVotes += weight;
        }

        emit VoteCast(msg.sender, proposalId, support, weight);
    }

    function execute(uint256 proposalId) external {
        Proposal storage proposal = proposals[proposalId];
        require(block.number > proposal.endBlock, "Voting not ended");
        require(!proposal.executed, "Already executed");
        require(proposal.forVotes > proposal.againstVotes, "Proposal failed");

        revert("Teaching stub: no action execution/quorum/timelock implemented");
    }
}
```

## Flash Loan

```solidity
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";

interface IFlashLoanReceiver {
    function executeOperation(
        address asset,
        uint256 amount,
        uint256 fee,
        bytes calldata params
    ) external returns (bool);
}

import "@openzeppelin/contracts/security/ReentrancyGuard.sol";

contract FlashLoanProvider is ReentrancyGuard {
    using SafeERC20 for IERC20;
    IERC20 public token;
    uint256 public feePercentage = 9; // 0.09% fee

    event FlashLoan(address indexed borrower, uint256 amount, uint256 fee);

    constructor(address _token) {
        token = IERC20(_token);
    }

    function flashLoan(
        address receiver,
        uint256 amount,
        bytes calldata params
    ) external nonReentrant {
        uint256 balanceBefore = token.balanceOf(address(this));
        require(balanceBefore >= amount, "Insufficient liquidity");

        uint256 fee = (amount * feePercentage) / 10000;

        // Send tokens to receiver
        token.safeTransfer(receiver, amount);

        // Execute callback
        require(
            IFlashLoanReceiver(receiver).executeOperation(
                address(token),
                amount,
                fee,
                params
            ),
            "Flash loan failed"
        );

        // Verify repayment
        uint256 balanceAfter = token.balanceOf(address(this));
        require(balanceAfter >= balanceBefore + fee, "Flash loan not repaid");

        emit FlashLoan(receiver, amount, fee);
    }
}

// Example flash loan receiver
contract FlashLoanReceiver is IFlashLoanReceiver {
    using SafeERC20 for IERC20;
    address public immutable provider;
    constructor(address trustedProvider) { provider = trustedProvider; }
    function executeOperation(
        address asset,
        uint256 amount,
        uint256 fee,
        bytes calldata params
    ) external override returns (bool) {
        require(msg.sender == provider, "Untrusted lender");
        // Decode params and execute arbitrage, liquidation, etc.
        // ...

        // This lender checks its final balance; approval alone does not repay.
        IERC20(asset).safeTransfer(provider, amount + fee);

        return true;
    }
}
```

## Resources

- **references/staking.md**: Staking mechanics and reward distribution
- **references/liquidity-pools.md**: AMM mathematics and pricing
- **references/governance-tokens.md**: Governance and voting systems
- **references/lending-protocols.md**: Lending/borrowing implementation
- **references/flash-loans.md**: Flash loan security and use cases
- **assets/staking-contract.sol**: Production staking template
- **assets/amm-contract.sol**: Full AMM implementation
- **assets/governance-token.sol**: Governance system
- **assets/lending-protocol.sol**: Lending platform template

## Best Practices

1. **Use Established Libraries**: OpenZeppelin, Solmate
2. **Test Thoroughly**: Unit tests, integration tests, fuzzing
3. **Audit Before Launch**: Professional security audits
4. **Start Simple**: MVP first, add features incrementally
5. **Monitor**: Track contract health and user activity
6. **Upgradability**: Consider proxy patterns for upgrades
7. **Emergency Controls**: Pause mechanisms for critical issues

## Common DeFi Patterns

- **Time-Weighted Average Price (TWAP)**: Price oracle resistance
- **Liquidity Mining**: Incentivize liquidity provision
- **Vesting**: Lock tokens with gradual release
- **Multisig**: Require multiple signatures for critical operations
- **Timelocks**: Delay execution of governance decisions

## Limitations
- Use this skill only when the task clearly matches the scope described above.
- Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
- Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.