Protocol Security & Auditing — Key concepts

Checks-Effects-InteractionsUpdate state before external calls to block reentrancy drains.

function withdraw(uint256 amount) external nonReentrant {
    uint256 bal = deposits[msg.sender];
    require(amount <= bal, "exceeds");
    deposits[msg.sender] = bal - amount; // effects
    token.transfer(msg.sender, amount);  // interaction
}

AuthEvery state-changing path should have clear owner/role checks and events.

Bundle CEI + nonReentrant + auth and caps as your first line; invariants and events make it observable and testable.