Solana schedules Alpenglow for Oct. 21, targeting 150ms finality

Solana plans to activate Alpenglow on Oct. 21, replacing its current consensus system with direct validator voting and targeting transaction finality in about 150 milliseconds. The Solana Foundation’s Alpenglow page says the upgrade will begin in epoch 1064, at approximately 15:00 UTC.

Finality is the point at which a transaction can no longer be reversed. Solana’s current system, TowerBFT, takes about 12.8 seconds to reach it, according to the Foundation. The 150-millisecond figure is a target; actual performance depends on network conditions.

How will Alpenglow change validator voting?

Today, validators record their votes as on-chain transactions. TowerBFT builds up enough votes over 32 slots before a block is final. Alpenglow’s first phase, Votor, changes that sequence: validators send votes directly to each other, then combine them into certificates. A block can become final after one or two rounds of voting, the Foundation says.

Think of the certificate as a signed receipt showing that enough validators agreed. The receipt summarizes their votes, instead of requiring each vote to be recorded as a separate transaction in a block. The CoinDesk report on the schedule also describes the change as moving validator votes off-chain.

The upgrade changes consensus, which governs how validators agree on transaction order and finality. It does not change execution: the Foundation says the Solana Virtual Machine, transactions, programs and fees stay the same.

When does the switch happen, and what will users see?

The feature gate is scheduled to activate at the start of epoch 1064 on Oct. 21. The network will keep using TowerBFT for the first 5,000 slots of that epoch, about 18 minutes, before Alpenglow takes over. The Foundation gives the epoch start time as an estimate and says the epoch itself is the key marker.

For most users, wallets and apps are expected to keep working as they do now. But transaction totals may look different: validator votes will no longer appear as transactions in blocks. A lower headline transaction count after activation would therefore not, by itself, show that users had become less active.

Validator operators have preparation requirements. Before the epoch begins, they must run a client based on Agave 4.3.0; the Foundation lists Agave, Jito-Solana and Harmonic Salsa as supported for the migration. Firedancer and Frankendancer are not supported during the switch. Operators also need at least 0.8 SOL above the rent-exempt minimum in their vote account for the Validator Admission Ticket fee. Alpenglow’s target is faster settlement; the source material does not establish that every transaction will be final in exactly 150 milliseconds.

Sources

• Solana Foundation’s Alpenglow page — solana.com
• CoinDesk report on the schedule — coindesk.com