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Solana activates Alpenglow, targeting 150ms finality

Solana activated Alpenglow on Oct. 21, replacing TowerBFT with a system targeting 150-millisecond finality as validator votes move off-chain.

Uruguay Can Editorial

Solana activates Alpenglow, targeting 150ms finality

Solana had relied on TowerBFT since its 2020 launch until Wednesday, Oct. 21, when it switched to Alpenglow, a consensus upgrade designed to bring transaction finality down from 12.8 seconds to about 150 milliseconds. The Block reported, citing Anza, that the new protocol took over on mainnet-beta at slot 459,653,000, at approximately 14:00 UTC.

Finality is the point at which a transaction can no longer be reversed. According to the Solana Foundation’s Alpenglow page, the new system moves validator votes off-chain: validators send votes directly to each other, bundle them into certificates and finalize a block in one or two voting rounds. Under TowerBFT, votes were transactions on the blockchain and finality took about 12.8 seconds. The 150-millisecond figure is Alpenglow’s target, not a change to how often blocks are produced.

What changes for Solana users and apps?

Transactions can become irreversible much sooner, which matters when an exchange credits a deposit or a merchant accepts a payment. The upgrade changes consensus, the process validators use to agree on transactions; it does not change transaction execution, programs or fees. For you, wallets and apps continue to work as before, while infrastructure that reads block and voting data may need to account for the new format.

What do validators need to keep participating?

Solana’s upgrade guidance lists two requirements for validators that want to keep voting and producing blocks:

  1. Run version 4.3.2 of an Agave-based client, such as Agave, Jito-Solana or Harmonic Salsa.
  2. Keep at least 0.8 SOL above the vote account’s rent-exempt minimum to pay the Validator Admission Ticket each epoch.

The handoff followed a 5,000-slot transition: TowerBFT continued through slot 459,652,999, then Alpenglow took over at the next slot. The Foundation says Rotor, a separate change to how block data spreads across the network, is planned for a later release and has no scheduled date.

Sources