Why does switching to a private mempool still leave me open to sandwich attacks?

Private and encrypted mempools now route more than half of Ethereum transactions, but encrypting a transaction does not hide everything a searcher needs. The trading pair, the direction of a swap, and a coarse size range can be inferred from surrounding chain state and timing metadata even when the transaction bytes are fully encrypted. A paper accepted at NeurIPS 2026 derives exact leakage thresholds at which this partial information remains sufficient to run a profitable sandwich attack against users who believe they are protected. The result is a false safety assumption: users opt into private relays and stop worrying, while searchers adapt their strategies to the residual signal that leaks through. There is no production tooling today that lets a user measure how much information their transaction leaks before they submit it, so the protection is unauditable.