Solana Activates Alpenglow, Targeting 150ms Finality

About 150 milliseconds is Solana’s target for transaction finality under Alpenglow, the consensus upgrade activated on mainnet on Oct. 21. For you, that means the network aims to make a transaction irreversible much sooner than under its previous system.

The Solana Foundation’s Alpenglow page says the upgrade replaced TowerBFT, Solana’s consensus protocol since 2020. Anza, Solana’s core engineering team, reported the mainnet handoff at slot 459,653,000.

What changes when a Solana transaction becomes final?

Finality is the point at which a transaction can no longer be reversed. Under TowerBFT, Solana’s finality took about 12.8 seconds; Alpenglow targets roughly 150 milliseconds, according to the Foundation.

That interval matters when an exchange credits a deposit or a merchant accepts a payment. Those businesses need to know when an asset has moved for good. The Block reported Anza’s account of the activation and said the upgrade condenses Solana’s previous two-step confirmation process into one.

The 150-millisecond figure describes the finality target, not how often Solana produces blocks. The Foundation says block times were reduced separately, from 400 milliseconds to 200 milliseconds in stages completed in October.

How does Alpenglow reach finality faster?

Validators now send votes directly to one another instead of recording votes as transactions in later blocks. They combine those votes into certificates, and a block becomes final after one or two rounds of voting, the Foundation says.

That replaces TowerBFT’s process, in which votes accumulated over 32 slots before a block became final. The protocol change affects how validators agree on blocks; the Foundation says transaction execution, fees, programs and the Solana Virtual Machine remain unchanged.

Anza implemented Alpenglow in Agave, its validator software. The upgrade underwent public testing that included red teaming, penetration testing, migration rehearsals and a security competition before mainnet activation, according to The Block.

What does the upgrade mean for users and builders?

For most users, the Foundation says, wallets and apps work as before and no action is needed. The change is beneath the transaction experience: settlement can reach finality sooner, while signing, sending and approving transactions remain the same.

Builders and infrastructure operators may need to review how they read and report blocks. Solana’s upgrade notes say validator votes no longer appear as transactions, so transaction counts and throughput dashboards that included vote traffic need a new baseline. The change can make those totals fall without showing a drop in user activity.

Some follow-on work remains separate from the live upgrade. The Foundation says Rotor, which is intended to change how block data spreads across the network, is planned for a later release and has no schedule. Alpenglow’s activation therefore delivers its new voting and finality system, while that data-propagation change remains ahead.

Sources

• Solana Foundation’s Alpenglow page — solana.com
• reported Anza’s account of the activation — theblock.co