The fee isdecided afteryour trade
Your swap posts a small refundable bond. Fifteen seconds later the pool checks what the price actually did. Retail gets it back. Arbitrage pays for the harm it caused.
The bond is held, not charged
Twenty-five basis points of your output is withheld inside the pool as an ERC-6909 claim. No transfer, no approval, no second transaction. If your trade turns out to be benign, all of it comes back.
θ is measured before you arrive
The threshold breathes with volatility, so a violent tape doesn't confiscate honest flow. It is computed from the two minutes before your swap landed — a window that had already closed, which is the only way you cannot move the bar you are judged against.
The window closes, and the pool looks back
Markout is the distance the price kept travelling in your direction after you left. Below θ, the bond is refunded in full. Above it, you forfeit in proportion to how far past you went — and it streams to the liquidity providers you took it from.
Measured on real flow, not simulated agents
Seven days of Unichain mainnet ETH/USDC, re-priced through the exact on-chain logic. Benign flow paid the 5.00 bps headline. Informed flow paid 12.32.