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Solana activates Alpenglow, targeting 150ms transaction finality

Solana activated Alpenglow on Oct. 21, replacing TowerBFT and targeting 150ms finality, which could let wallets and merchants treat payments as settled sooner.

The ChainBrief Editors

Solana activates Alpenglow, targeting 150ms transaction finality

Solana has relied on TowerBFT consensus since its 2020 launch; on Oct. 21, it activated Alpenglow, a replacement designed to make transactions final much sooner.

If its target holds, exchanges, wallets and merchants can treat transfers as settled with far less delay.

The Solana Foundation’s Alpenglow upgrade page says the change took effect in epoch 1064, with Alpenglow consensus starting at slot 459,653,000. The protocol targets about 150 milliseconds for finality, down from roughly 12.8 seconds under TowerBFT. That is a target stated by the Foundation, not an independently verified measurement of post-upgrade transaction times.

How does Alpenglow change transaction finality?

Alpenglow changes how validators agree on blocks. Under TowerBFT, validators submitted votes as on-chain transactions, and enough votes had to accumulate over 32 slots before a block became final. With Alpenglow’s Votor protocol, validators send votes directly to one another and aggregate them into certificates; the Foundation says a block can become final after one or two rounds of voting.

That shortens the wait for a transaction to become irreversible, the point at which an exchange can credit a deposit or a merchant can treat a payment as settled. CoinDesk’s report on the upgrade describes the change as moving validator voting off-chain and bundling votes into certificates. Faster finality may make those interactions feel more immediate; it does not change the transaction itself.

What changes for Solana users and applications?

For people signing and sending transactions, the Foundation says wallets and apps continue to work as before: transaction execution, the SVM, transaction formats and fees are unchanged. The intended user benefit is a shorter interval before a transfer is final, which could support near-immediate confirmations at a point of sale or faster exchange deposit handling.

For infrastructure providers, the change is more direct. Vote transactions no longer appear in blocks, so transaction counts that included them will fall even if user activity does not. Services that stream or index Solana data also need to account for changes to block production and finality; the Foundation says Geyser events now include a bank identifier, and `confirmed` and `finalized` describe the same state.

What does the upgrade require from validators?

Validators must run an Agave-based client at version 4.3.2, such as Agave, Jito-Solana or Harmonic Salsa, and keep at least 0.8 SOL above the rent-exempt minimum in their vote account for the Validator Admission Ticket fee. The Foundation says validators that do not pay the fee will not vote or produce blocks in the following epoch. Alpenglow’s first phase, Votor, is live; Rotor, a planned replacement for the Turbine block-propagation protocol, has no scheduled release.

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