Solana activates Alpenglow, targeting 150ms finality

Solana’s validators have used TowerBFT since the network launched in 2020; on Oct. 21, the network switched its mainnet consensus to Alpenglow, which targets roughly 150-millisecond finality. The Solana Foundation says that is down from about 12.8 seconds under TowerBFT.

The change brings Solana’s target for irreversible transaction settlement below a second, while leaving transaction execution and fees unchanged.

According to the Solana Foundation’s Alpenglow upgrade page, the upgrade activated at the start of epoch 1064, at approximately 13:36 UTC. The network continued using TowerBFT during a 5,000-slot transition window; Alpenglow consensus took over at slot 459,653,000. Anza, which developed the protocol, said in its mainnet announcement that the migration completed on the live network.

How does Alpenglow change validator voting?

Alpenglow’s first phase, Votor, replaces TowerBFT’s on-chain vote transactions with direct validator-to-validator votes that are aggregated into certificates. The Solana Foundation says those certificates allow a block to reach finality in one or two rounds of voting, replacing a process that accumulated votes over 32 slots.

Finality marks the point at which a transaction can no longer be reversed. The 150-millisecond figure is a target for that process, not a block-time measurement. Solana’s slot time was reduced separately, from 400 milliseconds to 200 milliseconds in stages completed in October, according to the Foundation.

What changes for applications and network data?

The upgrade changes consensus and how block information is reported, but not execution. The Foundation says the Solana Virtual Machine, transaction formats, programs and fee mechanics remain unchanged. Wallets and applications that only send transactions or read account state do not require a migration.

Infrastructure that consumes block or validator data does have changes to account for. Vote transactions no longer appear in blocks, and the Foundation says `confirmed` and `finalized` now describe the same state. Indexers and dashboards that counted vote transactions will need to reset their transaction baselines, since those votes have moved off-chain.

Is the full Alpenglow rollout complete?

Votor is live, but the second phase, Rotor, is still planned for a later release and has no scheduled date, according to the Foundation. Rotor is intended to replace Turbine, Solana’s block-data propagation protocol, with a single relay layer.

The mainnet activation therefore puts the new voting and finality system into operation while leaving that planned networking change for later. Anza said the upgrade went through public testing, migration rehearsals and security testing before validators adopted it on mainnet.

Sources

• Solana Foundation’s Alpenglow upgrade page — solana.com
• mainnet announcement — prnewswire.com