How Do “Finality Gadgets” in PoS Systems Serve a Similar Function to Checkpoints?

Finality gadgets in Proof-of-Stake (PoS) systems serve a similar function to checkpoints by providing an explicit, deterministic mechanism to finalize blocks. They typically use a supermajority (e.g.

2/3rds) of validators to attest that a block is irreversible. Unlike the probabilistic finality of PoW checkpoints, which are often developer-set, the finality gadget is a built-in protocol feature that ensures that once a block is finalized, it cannot be reverted without the slashing of a massive amount of staked capital, providing a strong, cryptographically-enforced guarantee of finality.