Skip to main content
Merkle Street

Protocols, markets, policy, people

Solana sets Oct. 21 for Alpenglow consensus switch

Solana scheduled Alpenglow for Oct. 21, targeting 150-millisecond finality by changing how validators certify blocks, a shift that could speed payment guarantees.

Merkle Street Newsroom#338dba2 min read

Solana sets Oct. 21 for Alpenglow consensus switch

Solana has scheduled its Alpenglow consensus upgrade for Oct. 21, targeting transaction finality in about 150 milliseconds by changing how validators agree on blocks. Finality is the point when a transaction can no longer be reversed. The Solana Foundation’s Alpenglow upgrade page says the change is planned for the start of epoch 1064, at approximately 15:00 UTC.

How will Alpenglow make a block final?

Today, Solana validators send votes as transactions recorded on the blockchain. Under TowerBFT, a block becomes final after enough votes accumulate over 32 slots. Alpenglow replaces TowerBFT with Votor, which lets validators send votes directly to one another and combine approvals into certificates. A block can then become final after one or two rounds of voting, according to the Foundation.

Think of the certificate as a signed receipt that gathers the validators’ approvals in one place. The upgrade targets roughly 150 milliseconds for finality, down from about 12.8 seconds today. That is a target, not a guarantee: actual performance will depend on network conditions, CoinDesk reported.

A payment can appear successful before it reaches finality. The shorter wait could let a merchant accept a payment, or a bridge release funds on another blockchain, sooner because each can act on a stronger guarantee that the transaction will not be undone. Alpenglow changes how validators agree on blocks; transaction execution, programs and fees stay the same.

Why could Solana’s transaction count fall?

Validator votes will no longer appear as transactions in blocks. That means Solana’s reported transaction count could drop sharply at activation even if people keep trading and making payments at the same pace, CoinDesk reported. The count will include fewer vote transactions, not necessarily fewer user actions.

What happens on Oct. 21?

The switch is scheduled for epoch 1064, which the Foundation expects to begin around 15:00 UTC on Oct. 21. Solana will continue using TowerBFT for the first 5,000 slots of that epoch, about 18 minutes, before Alpenglow takes over.

Validators must be ready before the epoch begins. The Foundation says they need to run a client built on Agave 4.3.0, such as Agave, Jito-Solana or Harmonic Salsa. Firedancer and Frankendancer will not support the initial migration, so operators using either must switch clients temporarily. For users sending transactions or running applications, the Foundation says no action is needed.

Source material