> ## Documentation Index
> Fetch the complete documentation index at: https://docs.makx.io/llms.txt
> Use this file to discover all available pages before exploring further.

# MakxYieldPadHook

> Contract reference for MakxYieldPadHook — the stateless Uniswap V4 hook that collects swap fees per pool.

## Overview

`MakxYieldPadHook` is a stateless Uniswap V4 hook attached to every pool created by MakxYieldPad. Its sole purpose is to intercept swaps and route the creator's hook fee to YieldPad.

It holds **no funds** and no rental state. All fee accounting is done in YieldPad via `recordHookFee()`.

***

## Immutables

| Variable      | Description                                            |
| ------------- | ------------------------------------------------------ |
| `poolManager` | Uniswap V4 PoolManager                                 |
| `yieldPad`    | MakxYieldPad — source of pool config, receiver of fees |

***

## Hook flags

```
BEFORE_SWAP                (0x80)
AFTER_SWAP                 (0x40)
BEFORE_SWAP_RETURNS_DELTA  (0x08)
AFTER_SWAP_RETURNS_DELTA   (0x04)

Required address suffix: 0xCC
```

The hook address must end in `0xCC` for the Uniswap V4 router to recognize and enforce the required flags.

***

## Fee architecture

Two independent fee layers per pool:

**LP fee** — Fixed per pool (`fee: 3000` = 0.3%), overridden on every swap via `OVERRIDE_FEE_FLAG`. Goes entirely to liquidity providers. Never changes for a given pool.

**Hook fee** — Flat bps set by the token creator (`hookFeeBps`). Applied to ETH on every swap. Routed to YieldPad and accrued in `launchFeeBalance`, claimable by the creator.

***

## `beforeSwap` — ETH → Token swaps

```solidity theme={null}
function beforeSwap(
    address,
    PoolKey calldata key,
    SwapParams calldata params,
    bytes calldata
) external returns (bytes4, BeforeSwapDelta, uint24)
```

Triggered on every swap. For `ETH → token` exact-input swaps (`zeroForOne = true`, `amountSpecified < 0`):

1. Reads `hookFeeBps` from YieldPad via `getPoolConfig(poolId)`.
2. Calculates `fee = -amountSpecified × hookFeeBps / 10_000`.
3. Returns a `BeforeSwapDelta` that reduces the ETH sent to the pool by `fee`.
4. Calls `poolManager.take(ETH, yieldPad, fee)` — transfers the fee directly to YieldPad.
5. Calls `yieldPad.recordHookFee(poolId, fee)` — YieldPad credits it to `launchFeeBalance`.

The pool only sees `ethIn - hookFee`. The LP fee applies to the reduced input.

***

## `afterSwap` — Token → ETH swaps

```solidity theme={null}
function afterSwap(
    address,
    PoolKey calldata key,
    SwapParams calldata params,
    BalanceDelta delta,
    bytes calldata
) external returns (bytes4, int128)
```

For `token → ETH` swaps (`zeroForOne = false`):

1. Reads `hookFeeBps` from YieldPad.
2. Calculates `fee = delta.amount0() × hookFeeBps / 10_000` (where `amount0` is positive ETH output).
3. Returns a negative `afterSwapDelta` reducing the ETH the swapper receives by `fee`.
4. Calls `poolManager.take(ETH, yieldPad, fee)`.
5. Calls `yieldPad.recordHookFee(poolId, fee)`.

***

## Pool currency convention

All Makx pools use:

* `currency0 = address(0)` (native ETH) — always sorted first
* `currency1 = ERC-20 token address`

ETH is always the "specified" or "output" side depending on swap direction. The hook always takes its fee from the ETH side.

***

## What the hook does NOT do

* Does not hold ETH or tokens.
* Does not track rental state or `prepaidUntil`.
* Does not restrict who can swap.
* Does not implement `beforeInitialize`, `afterInitialize`, `beforeAddLiquidity`, `afterAddLiquidity`, `beforeRemoveLiquidity`, `afterRemoveLiquidity`, `beforeDonate`, or `afterDonate` — all revert with `HookNotImplemented`.