A Sandwich-Resistant AMM | Umbra Research

Umbra Research introduces the sandwich-resistant AMM (sr-AMM), an application-layer design that makes atomic sandwich attacks unprofitable on constant-product AMMs. The design enforces an invariant that no swap fills at a price better than the price at the start of the slot window. Within a window, buys raise the offer along the xy=k curve while the bid price stays fixed and gains liquidity, and the state resets to the xy=k state at each window's start. The article notes that sandwiching remains possible at slot window boundaries and through just-in-time liquidity, and it suggests a liquidity activation period as a possible mitigation for the latter.