Solana Activates Alpenglow, Retiring Its TowerBFT Consensus Protocol

Solana’s Alpenglow consensus system took control of mainnet on Wednesday, Oct. 21, ending TowerBFT’s role after more than six years and changing how validators confirm blocks.

The switch happened at slot 459,653,000 around 10 a.m. ET (14:00 UTC), following a 5,000-slot transition. TowerBFT had served as Solana’s consensus protocol since the network launched in March 2020.

Alpenglow changes how validators vote: they send votes directly to one another and bundle them into certificates, rather than putting votes in on-chain transactions processed in later blocks. Its active Votor phase handles consensus. Rotor, a separate planned change to block-data delivery, has no release date.

The protocol’s stated finality target is about 150 milliseconds. Finality means a transaction can no longer be reversed. That figure is a target, not a confirmed measure of live performance. TowerBFT’s historical finality was about 12.8 seconds, though separate slot-time reductions had brought its more recent pace to about six seconds before Alpenglow went live.