Solana activates Alpenglow, targeting 150ms finality

Solana activated Alpenglow on mainnet on Oct. 21, replacing the TowerBFT consensus system it had used since 2020 with a voting protocol designed to make transactions final in about 150 milliseconds. The Solana Foundation’s upgrade guide says the change affects how validators agree on blocks, while transaction execution, fees and wallets stay the same.

How does Alpenglow make transactions final faster?

Alpenglow changes how validators vote. Under TowerBFT, validators sent votes as blockchain transactions, and blocks became final after enough votes accumulated over 32 slots. The new protocol, called Votor, lets validators send votes directly to one another and combine them into certificates. A block can then become final after one or two voting rounds.

Finality is the point at which an application can treat a transaction as settled and no longer reversible. Solana Foundation gives the old time as about 12.8 seconds and the new target as roughly 150 milliseconds. CoinDesk’s report on the activation notes that the 150-millisecond figure is a target under normal network conditions, not a guaranteed wait for every user.

Think of it as replacing a pile of ballots that must build up across several rounds with validators exchanging and bundling their votes directly. Those certificates let the network settle a block sooner. The change is to consensus, the agreement process; Solana’s execution system still runs transactions and programs as before.

What changes for someone sending SOL or paying with a token?

Most users do not need to change anything: the Foundation says existing wallets and apps continue to work, and signing, sending and approving transactions are unchanged. Faster finality can let services treat a payment as settled sooner. An exchange may be able to credit a deposit earlier, or a merchant may get stronger settlement assurance before releasing goods.

The time a user sees on screen still depends on the app or service handling the transaction. CoinDesk reported that some computers receive finality information later than the validators that vote directly. So the protocol’s target does not mean every wallet will display every payment at exactly 150 milliseconds.

Why might Solana transaction charts show a sudden drop?

Validator votes no longer appear as transactions in blocks. That means dashboards counting those votes will show lower transaction totals after the switch, even if user payments and trades have not fallen. Anyone comparing activity before and after activation needs to separate validator votes from transactions initiated by users.

The upgrade also leaves block production timing distinct from finality: Solana’s Foundation says the 150-millisecond figure measures how long a transaction takes to become final, not how often blocks are produced. Alpenglow’s first phase, Votor, is live; a second phase called Rotor is planned to replace the network’s block-data propagation protocol, but the Foundation says it is not yet scheduled.

Sources and documents

• Solana Foundation’s upgrade guide — solana.com
• CoinDesk’s report on the activation — coindesk.com