Economic finality

Casper FFG uses supermajority votes to justify and finalize checkpoints. Under normal assumptions, conflicting histories cannot both finalize without overlapping slashable votes. The guarantee is expressed as validator economic accountability.

A two-thirds supermajority threshold does not mean every conflict requires two-thirds malicious stake. The relevant safety result identifies at least one third of stake as responsible for incompatible votes.

This guarantee depends on the protocol, evidence availability and enforcement of penalties. It differs from proof-of-work probabilistic finality and the inactivity leak, which addresses missing participation and consensus progress.