What Is “Economic Finality” in the Context of PoS Consensus?

Economic finality is the point in a Proof-of-Stake blockchain's history after which a transaction is considered irreversible, not just probabilistically (like in PoW), but because reversing it would require an economically ruinous action by the attacker. In systems like Ethereum's PoS, this is achieved through "attesters" voting on checkpoints.

Once a block is finalized, reversing it would trigger a massive slashing event, destroying the attacker's staked capital. This makes the attack economically irrational and provides a strong guarantee of transaction immutability.