Glossary
Pre-Confirmation
A signed commitment from a future Ethereum block proposer that they will include a specific transaction — gives users L1-grade UX latency before the slot.
A pre-confirmation ("preconf") is a binding promise from the upcoming slot's proposer to include a given transaction in their block. If the proposer breaks the promise, they are slashed.
The mechanic gives Ethereum L1 the sub-second UX of a Layer-2 without changing the protocol. Multiple designs are in flight (Bolt, Commit-Boost, MEV-Boost relays); they generally rely on restaked stake for the slashing collateral.