beforeSwap returns dynamic fee

.forge-snapshots/add liquidity to already existing position with salt.snap

@@ -1 +1 @@
-151132
+151126

.forge-snapshots/addLiquidity CA fee.snap

@@ -1 +1 @@
-329498
+329492

.forge-snapshots/addLiquidity with empty hook.snap

@@ -1 +1 @@
-284133
+284127

.forge-snapshots/addLiquidity with native token.snap

@@ -1 +1 @@
-141308
+141302

.forge-snapshots/addLiquidity.snap

@@ -1 +1 @@
-151108
+151102

.forge-snapshots/create new liquidity to a position with salt.snap

@@ -1 +1 @@
-299660
+299654

.forge-snapshots/donate gas with 1 token.snap

@@ -1 +1 @@
-108741
+108735

.forge-snapshots/donate gas with 2 tokens.snap

@@ -1 +1 @@
-149236
+149230

.forge-snapshots/initialize.snap

@@ -1 +1 @@
-62245
+62239

.forge-snapshots/poolManager bytecode size.snap

@@ -1 +1 @@
-23579
+23804

.forge-snapshots/removeLiquidity CA fee.snap

@@ -1 +1 @@
-185071
+185065

.forge-snapshots/removeLiquidity with empty hook.snap

@@ -1 +1 @@
-121089
+121083

.forge-snapshots/removeLiquidity with native token.snap

@@ -1 +1 @@
-117864
+117858

.forge-snapshots/removeLiquidity.snap

@@ -1 +1 @@
-121077
+121071

.forge-snapshots/simple swap with native.snap

@@ -1 +1 @@
-117512
+117648

.forge-snapshots/simple swap.snap

@@ -1 +1 @@
-132708
+132844

.forge-snapshots/swap CA custom curve + swap noop.snap

@@ -1 +1 @@
-135905
+136267

.forge-snapshots/swap CA fee on unspecified.snap

@@ -1 +1 @@
-185063
+185199

.forge-snapshots/swap against liquidity with native token.snap

@@ -1 +1 @@
-114007
+114143

.forge-snapshots/swap against liquidity.snap

@@ -1 +1 @@
-125385
+125521

.forge-snapshots/swap burn 6909 for input.snap

@@ -1 +1 @@
-137390
+137525

.forge-snapshots/swap burn native 6909 for input.snap

@@ -1 +1 @@
-126490
+126626

.forge-snapshots/swap mint native output as 6909.snap

@@ -1 +1 @@
-148525
+148660

.forge-snapshots/swap mint output as 6909.snap

@@ -1 +1 @@
-165420
+165556

.forge-snapshots/swap skips hook call if hook is caller.snap

@@ -1 +1 @@
-225039
+225746

.forge-snapshots/swap with dynamic fee.snap

@@ -1 +1 @@
-149687
+149823

.forge-snapshots/swap with hooks.snap

@@ -1 +1 @@
-125397
+125533

.forge-snapshots/swap with lp fee and protocol fee.snap

@@ -1 +1 @@
-181949
+182500

.forge-snapshots/swap with return dynamic fee.snap

@@ -0,0 +1 @@
+157979

.forge-snapshots/update dynamic fee in before swap.snap

@@ -1 +1 @@
-160240
+160797

src/PoolManager.sol

@@ -271,19 +271,25 @@ contract PoolManager is IPoolManager, ProtocolFees, NoDelegateCall, ERC6909Claim
         PoolId id = key.toId();
         _checkPoolInitialized(id);
 
-        (int256 amountToSwap, BeforeSwapDelta beforeSwapDelta) = key.hooks.beforeSwap(key, params, hookData);
-
-        // execute swap, account protocol fees, and emit swap event
-        swapDelta = _swap(
-            id,
-            Pool.SwapParams({
-                tickSpacing: key.tickSpacing,
-                zeroForOne: params.zeroForOne,
-                amountSpecified: amountToSwap,
-                sqrtPriceLimitX96: params.sqrtPriceLimitX96
-            }),
-            params.zeroForOne ? key.currency0 : key.currency1 // input token
-        );
+        BeforeSwapDelta beforeSwapDelta;
+        {
+            int256 amountToSwap;
+            uint24 fee;
+            (amountToSwap, beforeSwapDelta, fee) = key.hooks.beforeSwap(key, params, hookData);
+
+            // execute swap, account protocol fees, and emit swap event
+            swapDelta = _swap(
+                id,
+                Pool.SwapParams({
+                    tickSpacing: key.tickSpacing,
+                    zeroForOne: params.zeroForOne,
+                    amountSpecified: amountToSwap,
+                    sqrtPriceLimitX96: params.sqrtPriceLimitX96,
+                    fee: fee
+                }),
+                params.zeroForOne ? key.currency0 : key.currency1 // input token
+            );
+        }
 
         BalanceDelta hookDelta;
         (swapDelta, hookDelta) = key.hooks.afterSwap(key, params, swapDelta, hookData, beforeSwapDelta);

src/interfaces/IHooks.sol

@@ -99,12 +99,13 @@ interface IHooks {
     /// @param hookData Arbitrary data handed into the PoolManager by the swapper to be be passed on to the hook
     /// @return bytes4 The function selector for the hook
     /// @return BeforeSwapDelta The hook's delta in specified and unspecified currencies. Positive: the hook is owed/took currency, negative: the hook owes/sent currency
+    /// @return uint24 An optional swap fee, only used if the Pool has a dynamic fee and the value is less than of equal to LPFeeLibrary.MAX_LP_FEE
     function beforeSwap(
         address sender,
         PoolKey calldata key,
         IPoolManager.SwapParams calldata params,
         bytes calldata hookData
-    ) external returns (bytes4, BeforeSwapDelta);
+    ) external returns (bytes4, BeforeSwapDelta, uint24);
 
     /// @notice The hook called after a swap
     /// @param sender The initial msg.sender for the swap call

src/libraries/Hooks.sol

@@ -148,6 +148,25 @@ library Hooks {
         (, delta) = abi.decode(result, (bytes4, int256));
     }
 
+    /// @notice performs a hook call using the given calldata on the given hook
+    /// @return delta The delta returned by the hook
+    /// @return fee The fee returned by the hook
+    function callHookWithReturnDeltaAndFee(IHooks self, bytes memory data, bool parseReturn, bool parseFee)
+        internal
+        returns (int256 delta, uint24 fee)
+    {
+        bytes memory result = callHook(self, data);
+        (, delta, fee) = abi.decode(result, (bytes4, int256, uint24));
+
+        if (!parseReturn) {
+            delta = 0;
+        }
+
+        if (!parseFee) {
+            fee = type(uint24).max;
+        }
+    }
+
     /// @notice modifier to prevent calling a hook if they initiated the action
     modifier noSelfCall(IHooks self) {
         if (msg.sender != address(self)) {
@@ -236,20 +255,23 @@ library Hooks {
     /// @notice calls beforeSwap hook if permissioned and validates return value
     function beforeSwap(IHooks self, PoolKey memory key, IPoolManager.SwapParams memory params, bytes calldata hookData)
         internal
-        returns (int256 amountToSwap, BeforeSwapDelta hookReturn)
+        returns (int256 amountToSwap, BeforeSwapDelta hookReturn, uint24 lpFee)
     {
         amountToSwap = params.amountSpecified;
-        if (msg.sender == address(self)) return (amountToSwap, BeforeSwapDeltaLibrary.ZERO_DELTA);
+        lpFee = type(uint24).max;
+        if (msg.sender == address(self)) return (amountToSwap, BeforeSwapDeltaLibrary.ZERO_DELTA, type(uint24).max);
 
         if (self.hasPermission(BEFORE_SWAP_FLAG)) {
             bool canReturnDelta = self.hasPermission(BEFORE_SWAP_RETURNS_DELTA_FLAG);
-            hookReturn = BeforeSwapDelta.wrap(
-                self.callHookWithReturnDelta(
-                    abi.encodeWithSelector(IHooks.beforeSwap.selector, msg.sender, key, params, hookData),
-                    canReturnDelta
-                )
+            int256 result;
+            (result, lpFee) = self.callHookWithReturnDeltaAndFee(
+                abi.encodeWithSelector(IHooks.beforeSwap.selector, msg.sender, key, params, hookData),
+                canReturnDelta,
+                key.fee.isDynamicFee()
             );
 
+            hookReturn = BeforeSwapDelta.wrap(result);
+
             // skip this logic for the case where the hook return is 0
             if (canReturnDelta) {
                 // any return in unspecified is passed to the afterSwap hook for handling

src/libraries/Pool.sol

@@ -295,6 +295,7 @@ library Pool {
         bool zeroForOne;
         int256 amountSpecified;
         uint160 sqrtPriceLimitX96;
+        uint24 fee;
     }
 
     /// @notice Executes a swap against the state, and returns the amount deltas of the pool
@@ -319,8 +320,8 @@ library Pool {
         state.feeGrowthGlobalX128 = zeroForOne ? self.feeGrowthGlobal0X128 : self.feeGrowthGlobal1X128;
         state.liquidity = cache.liquidityStart;
 
-        swapFee =
-            cache.protocolFee == 0 ? slot0Start.lpFee : uint24(cache.protocolFee).calculateSwapFee(slot0Start.lpFee);
+        uint24 _lpFee = params.fee <= LPFeeLibrary.MAX_LP_FEE ? params.fee : slot0Start.lpFee;
+        swapFee = cache.protocolFee == 0 ? _lpFee : uint24(cache.protocolFee).calculateSwapFee(_lpFee);
 
         if (!exactInput && (swapFee == LPFeeLibrary.MAX_LP_FEE)) {
             revert InvalidFeeForExactOut();

src/test/BaseTestHooks.sol

@@ -72,7 +72,7 @@ contract BaseTestHooks is IHooks {
         PoolKey calldata, /* key **/
         IPoolManager.SwapParams calldata, /* params **/
         bytes calldata /* hookData **/
-    ) external virtual returns (bytes4, BeforeSwapDelta) {
+    ) external virtual returns (bytes4, BeforeSwapDelta, uint24) {
         revert HookNotImplemented();
     }
 

src/test/CustomCurveHook.sol

@@ -37,7 +37,7 @@ contract CustomCurveHook is BaseTestHooks {
         PoolKey calldata key,
         IPoolManager.SwapParams calldata params,
         bytes calldata /* hookData **/
-    ) external override onlyPoolManager returns (bytes4, BeforeSwapDelta) {
+    ) external override onlyPoolManager returns (bytes4, BeforeSwapDelta, uint24) {
         (Currency inputCurrency, Currency outputCurrency, uint256 amount) = _getInputOutputAndAmount(key, params);
 
         // this "custom curve" is a line, 1-1
@@ -47,7 +47,7 @@ contract CustomCurveHook is BaseTestHooks {
 
         // return -amountSpecified as specified to no-op the concentrated liquidity swap
         BeforeSwapDelta hookDelta = toBeforeSwapDelta(int128(-params.amountSpecified), int128(params.amountSpecified));
-        return (IHooks.beforeSwap.selector, hookDelta);
+        return (IHooks.beforeSwap.selector, hookDelta, 0);
     }
 
     function afterAddLiquidity(

src/test/DeltaReturningHook.sol

@@ -51,15 +51,15 @@ contract DeltaReturningHook is BaseTestHooks {
         PoolKey calldata key,
         IPoolManager.SwapParams calldata params,
         bytes calldata /* hookData **/
-    ) external override onlyPoolManager returns (bytes4, BeforeSwapDelta) {
+    ) external override onlyPoolManager returns (bytes4, BeforeSwapDelta, uint24) {
         (Currency specifiedCurrency, Currency unspecifiedCurrency) = _sortCurrencies(key, params);
 
         if (deltaSpecified != 0) _settleOrTake(specifiedCurrency, deltaSpecified);
         if (deltaUnspecifiedBeforeSwap != 0) _settleOrTake(unspecifiedCurrency, deltaUnspecifiedBeforeSwap);
 
         BeforeSwapDelta beforeSwapDelta = toBeforeSwapDelta(deltaSpecified, deltaUnspecifiedBeforeSwap);
 
-        return (IHooks.beforeSwap.selector, beforeSwapDelta);
+        return (IHooks.beforeSwap.selector, beforeSwapDelta, 0);
     }
 
     function afterSwap(

src/test/DynamicFeesTestHook.sol

@@ -31,10 +31,10 @@ contract DynamicFeesTestHook is BaseTestHooks {
     function beforeSwap(address, PoolKey calldata key, IPoolManager.SwapParams calldata, bytes calldata)
         external
         override
-        returns (bytes4, BeforeSwapDelta)
+        returns (bytes4, BeforeSwapDelta, uint24)
     {
         manager.updateDynamicLPFee(key, fee);
-        return (IHooks.beforeSwap.selector, BeforeSwapDeltaLibrary.ZERO_DELTA);
+        return (IHooks.beforeSwap.selector, BeforeSwapDeltaLibrary.ZERO_DELTA, type(uint24).max);
     }
 
     function forcePoolFeeUpdate(PoolKey calldata _key, uint24 _fee) external {

src/test/DynamicReturnFeeTestHook.sol

@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.24;
+
+import {BaseTestHooks} from "./BaseTestHooks.sol";
+import {PoolKey} from "../types/PoolKey.sol";
+import {IPoolManager} from "../interfaces/IPoolManager.sol";
+import {IHooks} from "../interfaces/IHooks.sol";
+import {BeforeSwapDelta, BeforeSwapDeltaLibrary} from "../types/BeforeSwapDelta.sol";
+
+contract DynamicReturnFeeTestHook is BaseTestHooks {
+    uint24 internal fee;
+    IPoolManager manager;
+
+    function setManager(IPoolManager _manager) external {
+        manager = _manager;
+    }
+
+    function setFee(uint24 _fee) external {
+        fee = _fee;
+    }
+
+    function beforeSwap(address, PoolKey calldata, IPoolManager.SwapParams calldata, bytes calldata)
+        external
+        override
+        returns (bytes4, BeforeSwapDelta, uint24)
+    {
+        return (IHooks.beforeSwap.selector, BeforeSwapDeltaLibrary.ZERO_DELTA, fee);
+    }
+}

src/test/EmptyTestHooks.sol

@@ -92,9 +92,9 @@ contract EmptyTestHooks is IHooks {
         external
         pure
         override
-        returns (bytes4, BeforeSwapDelta)
+        returns (bytes4, BeforeSwapDelta, uint24)
     {
-        return (IHooks.beforeSwap.selector, BeforeSwapDeltaLibrary.ZERO_DELTA);
+        return (IHooks.beforeSwap.selector, BeforeSwapDeltaLibrary.ZERO_DELTA, 0);
     }
 
     function afterSwap(address, PoolKey calldata, IPoolManager.SwapParams calldata, BalanceDelta, bytes calldata)

src/test/MockHooks.sol

@@ -97,12 +97,15 @@ contract MockHooks is IHooks {
     function beforeSwap(address, PoolKey calldata, IPoolManager.SwapParams calldata, bytes calldata hookData)
         external
         override
-        returns (bytes4, BeforeSwapDelta)
+        returns (bytes4, BeforeSwapDelta, uint24)
     {
         beforeSwapData = hookData;
         bytes4 selector = MockHooks.beforeSwap.selector;
-        return
-            (returnValues[selector] == bytes4(0) ? selector : returnValues[selector], BeforeSwapDeltaLibrary.ZERO_DELTA);
+        return (
+            returnValues[selector] == bytes4(0) ? selector : returnValues[selector],
+            BeforeSwapDeltaLibrary.ZERO_DELTA,
+            0
+        );
     }
 
     function afterSwap(