BloomFeeHookV2

A trading tax hook. It takes a cut of every trade, charges more right after launch and keeps a price record.

• Takes a cut of every trade

  On top of the normal pool fee, it keeps a share of each trade. The fee builds up in the hook until it is collected.

  The code that does this (beforeSwap):

  function beforeSwap(address sender, PoolKey calldata key, SwapParams calldata params, bytes calldata)
      external onlyPoolManager returns (bytes4, BeforeSwapDelta, uint24)
  {
      PoolId id = key.toId();
      Terms memory t = terms[id];
      if (t.token == address(0)) revert InvalidPool();
      _observe(id);
      bool exactInput = params.amountSpecified < 0;
      bool specifiedIs0 = exactInput == params.zeroForOne;
      if (specifiedIs0 != t.quoteIs0) return (IHooks.beforeSwap.selector, BeforeSwapDeltaLibrary.ZERO_DELTA, 0);
      // Quote is the specified leg: exact-input buy or exact-output sell.
      uint256 extraBps = _extraBps(t);
      uint256 fee;
      if (exactInput) {
          uint256 gross = uint256(-params.amountSpecified);
          fee = _collect(t, sender, gross, Math.mulDiv(gross, extraBps, BPS));
      } else {
          uint256 net = uint256(params.amountSpecified);
          uint256 gross = _grossForNet(net, t.creatorBps, extraBps);
          fee = _collectFromNet(t, sender, gross, net);
      }
      return (IHooks.beforeSwap.selector, toBeforeSwapDelta(int128(int256(fee)), 0), 0);
  }

• Higher at launch

  The fee starts higher right after launch and comes down over time, which makes it costly for bots to buy first.

  The code that does this (extraBps):

  function _extraBps(Terms memory t) private view returns (uint256) {
      uint256 end = uint256(t.launchedAt) + LAUNCH_FEE_DURATION;
      if (block.timestamp >= end) return 0;
      // The launcher's own first buy, in the launch transaction, pays the normal fee only.
      if (block.number == t.launchBlock && tx.origin == t.launcher) return 0;
      uint256 normal = FeeMath.PLATFORM_BPS + t.creatorBps;
      if (normal >= LAUNCH_FEE_BPS) return 0;
      return (LAUNCH_FEE_BPS - normal) * (end - block.timestamp) / LAUNCH_FEE_DURATION;
  }

• Keeps a price record

  It records the pool’s price over time, so other apps can read a fair average price.

  The code that does this (beforeSwap):

  function beforeSwap(address sender, PoolKey calldata key, SwapParams calldata params, bytes calldata)
      external onlyPoolManager returns (bytes4, BeforeSwapDelta, uint24)
  {
      PoolId id = key.toId();
      Terms memory t = terms[id];
      if (t.token == address(0)) revert InvalidPool();
      _observe(id);
      bool exactInput = params.amountSpecified < 0;
      bool specifiedIs0 = exactInput == params.zeroForOne;
      if (specifiedIs0 != t.quoteIs0) return (IHooks.beforeSwap.selector, BeforeSwapDeltaLibrary.ZERO_DELTA, 0);
      // Quote is the specified leg: exact-input buy or exact-output sell.
      uint256 extraBps = _extraBps(t);
      uint256 fee;
      if (exactInput) {
          uint256 gross = uint256(-params.amountSpecified);
          fee = _collect(t, sender, gross, Math.mulDiv(gross, extraBps, BPS));
      } else {
          uint256 net = uint256(params.amountSpecified);
          uint256 gross = _grossForNet(net, t.creatorBps, extraBps);
          fee = _collectFromNet(t, sender, gross, net);
      }
      return (IHooks.beforeSwap.selector, toBeforeSwapDelta(int128(int256(fee)), 0), 0);
  }

• Only approved callers create pools

  New pools with this hook can only be created by approved callers, for example its own factory or launcher.

  The code that does this (beforeInitialize):

  function beforeInitialize(address sender, PoolKey calldata key, uint160)
      external onlyPoolManager returns (bytes4)
  {
      if (key.fee != 0 || key.tickSpacing != TICK_SPACING || address(key.hooks) != address(this)) revert InvalidPool();
      address c0 = Currency.unwrap(key.currency0);
      address c1 = Currency.unwrap(key.currency1);
      (address curve, address quote, address executor, bytes32 existing) = factory.launchRouting(c0);
      address token = c0;
      if (curve == address(0)) {
          (curve, quote, executor, existing) = factory.launchRouting(c1);
          token = c1;
      }
      if (curve == address(0) || quote != (token == c0 ? c1 : c0) || sender != executor || existing != bytes32(0)
          || IHookExecutorV2(executor).feeHook() != address(this) || address(keys[token].hooks) != address(0)
          || BondingCurve(curve).phase() != BondingCurve.Phase.PoolActive) revert InvalidPool();
      (, , address escrow, address platform, , address vault, , , , uint16 creatorBps,
          uint16 holderShareBps, uint16 buybackShareBps,) = BondingCurve(curve).settings();
      (address launcher,,,,,,) = factory.launches(token);
      PoolId id = key.toId();
      terms[id] = Terms(token, quote, curve, escrow, platform, vault, quote == c0, creatorBps, holderShareBps,
          buybackShareBps, launcher, uint64(block.timestamp), uint64(block.number));
      keys[token] = key;
      IERC20(quote).forceApprove(escrow, type(uint256).max);
      IERC20(quote).forceApprove(token, type(uint256).max);
      IERC20(quote).forceApprove(vault, type(uint256).max);
      Oracle storage o = oracles[id];
      o.lastUpdate = uint64(block.timestamp);
      o.observations[0] = Observation(uint64(block.timestamp), 0);
      o.count = 1;
      emit CanonicalPoolRegistered(token, id, quote);
      // …

Who controls it: Nobody. The hook has no admin functions, and the code cannot be changed.

Based on the hook’s published code.