ImpactFeeV4
Uniswap V4 Hook for automated public goods
Demo
About
The problem it solves Trading generates massive value, but profits rarely flow to public goods. Impact Fee Hook solves this by **automatically converting 0.10% of every Uniswap V4 swap into yield-generating donations** for social impact projects. **Benefits:** - **For Traders**: Minimal fee (0.10%) that goes directly to charity, not middlemen - **For Public Goods**: Sustainable passive income from DeFi trading volume - **For Protocols**: Easy integration - just attach the hook to any pool - **For Society**: Transforms financial activity into automatic philanthropy No user action required. Trade → donate. Simple.
How it's made
Challenges we ran into **Problem**: `octant-v2-core` v0.1.2 didn't include `ITokenizedStrategy.sol` interface that `BaseStrategy` imports. Build failed. **Solution**: Created a shim interface with all 15+ required function signatures by iteratively compiling and adding missing methods. Also copied `errors.sol` from the core repo. Updated `remappings.txt` to resolve imports properly. **Problem**: Initial design sent vault shares to the hook contract itself, making them inaccessible to the actual donation address. **Solution**: Added `donationReceiver` immutable parameter to hook constructor. Modified `unlockCallback` to use `feeSink.deposit(feeAmount, donationReceiver)` instead of `address(this)`. Now shares go directly to charity. **Problem**: Uniswap V4 requires hooks to have addresses that match their permission flags. Can't just deploy and hope. **Solution**: Used HookMiner with CREATE2 salt mining to generate deterministic addresses with correct flag bits (`beforeSwap + beforeSwapReturnsDelta`). Deployed successfully on first try.