Solana’s Alpenglow Upgrade Targets 150-Millisecond Finality Oct. 21

Solana’s Alpenglow consensus upgrade is scheduled to start its mainnet rollout Wednesday, Oct. 21, replacing TowerBFT with Votor and aiming to reduce transaction finality from about 12.8 seconds to roughly 150 milliseconds.

Finality is the point at which a transaction is treated as irreversible. A shorter finality interval would mean less time between a transaction being confirmed and reaching that point. The rollout follows the Oct. 21 mainnet schedule.

The handoff is staged within epoch 1064. TowerBFT will remain active for the epoch’s first 5,000 slots, a period of about 18 minutes, before Alpenglow takes over at slot 459,653,000. The 150-millisecond figure is a target, not a fixed result; actual finality will vary with stake distribution and network conditions.

Votor changes how validators reach agreement. Under TowerBFT, their votes are recorded as on-chain transactions. With Votor, validators will send votes directly to one another and combine them into certificates. A block can finalize in one round when at least 80% of stake supports it; if that threshold is missed, a second round uses a 60% threshold.

Moving validator votes out of blocks is expected to sharply lower reported transaction counts and transactions-per-second figures. That accounting change is not expected to correspond to a drop in user activity.

Users do not need to take action. Transaction formats, programs, fees and the Solana Virtual Machine (SVM) will remain unchanged. Validator operators must use an Agave-based client built on Agave 4.3.0 and keep at least 0.8 SOL above the rent-exempt minimum in the vote account for a Validator Admission Ticket. The ticket’s 0.8 SOL charge is per epoch and is burned.

The Oct. 21 rollout covers Votor. Rotor, a later component intended to replace Turbine’s block-data distribution system, is planned for a future release without a listed schedule.