Glossary
Tower BFT
Solana's optimization of PBFT — validators progressively lock in deeper votes with exponentially increasing slashing weight, achieving fast finality without all-to-all rounds.
Tower BFT is Solana's consensus algorithm — a customized practical Byzantine Fault Tolerance variant. Each validator's vote on a block stacks on top of their previous vote. Switching vote requires unlocking a "tower" of stacked votes, with each level requiring exponentially longer slashing lockup.
The structure makes deep reorgs prohibitively expensive (a validator would forfeit weeks of stake) while keeping the active voting round fast. Combined with Proof of History, Tower BFT produces Solana's fast finality without the full all-to-all communication of classical BFT.