How it works

One swap, from the router to the LPs. Nothing runs between swaps: no keeper, no oracle push.

1. 1

   A swap enters the PoolManager

   The pool's fee is dynamic, so the hook decides it.
2. 2

   The PoolManager calls beforeSwap

   The hook's only permissions are beforeInitialize and beforeSwap.
3. 3

   The hook reads the pool price

   The block's first swap pins the top-of-block price, so splitting one arb into many swaps doesn't make it cheaper.
4. 4

   It reads the perp market, same block

   Two gas-capped precompile calls: oracle at 0x…0807, mark at 0x…0806. A bad read never reverts.
5. 5

   It computes the fee

   Gap, premium and stress, in integer math. Every input is emitted in FeeComputed.
6. 6

   The fee goes to LPs

   Returned with the override flag 0x400000. The PoolManager charges it like any LP fee.

Why the same block matters#

HyperEVM and HyperCore share one consensus. The price the hook reads is the price the perp market has in that block, not a feed pushed later. The pool and the market are compared at the same moment.