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Solana activates Alpenglow, targeting 150ms finality

Solana activated Alpenglow on Oct. 21, replacing TowerBFT with a new validator voting system that targets 150ms finality, about 99% faster than before.

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Solana activates Alpenglow, targeting 150ms finality

Solana activated Alpenglow on mainnet on Oct. 21, replacing its TowerBFT consensus system with a protocol that targets 150-millisecond finality, about 99% faster than the old 12.8-second measure. The Solana Foundation’s upgrade page says the change affects how validators agree that transactions can no longer be reversed.

The 150ms figure is a target, not a confirmed live-network measurement. For you, the change could mean faster certainty when an exchange credits a deposit or a merchant accepts a payment, while transaction execution, programs and fees stay the same.

When did Alpenglow take over from TowerBFT?

Alpenglow activated in epoch 1064, which began at about 13:36 UTC on Oct. 21, according to Solana. TowerBFT continued for a 5,000-slot transition window; Alpenglow consensus took over at slot 459,653,000, around 14:00 UTC.

The Block’s report, citing a statement from Solana engineering firm Anza, also confirms the mainnet handoff and retirement of TowerBFT, which Solana had used since its 2020 launch. The Foundation says 446 of the network’s 654 validators signed the certificate for the final TowerBFT block.

How does the new system aim to cut finality?

Under TowerBFT, validators cast votes as transactions, and a block became final after enough votes accumulated over 32 slots. Alpenglow’s first phase, Votor, sends votes directly between validators and combines them into certificates, so a block can become final after one or two rounds of voting.

That moves validator voting out of the transaction stream. It changes how the network reaches agreement, not how applications execute transactions. Solana says wallets and apps continue to work as before, though systems that count vote transactions or rely on differences between “confirmed” and “finalized” statuses may need to adjust.

What should you watch after the launch?

Watch measured finality on mainnet to see whether it approaches the 150ms target; the target alone does not establish real-world performance. Also watch for the next Alpenglow phase: Rotor is planned to replace Turbine, which spreads block data across the network, but Solana says it has no release date yet.

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