Solana activates Alpenglow, replacing its consensus system

Solana activated Alpenglow on mainnet Wednesday, Oct. 21, replacing TowerBFT with a new consensus protocol that targets transaction finality in about 150 milliseconds, down from 12.8 seconds. The handoff took place at slot 459,653,000, according to The Block’s report on the launch, which cited Solana engineering firm Anza.

The change retires the voting system Solana used since its 2020 launch. The 150-millisecond figure is a target from Anza and the Solana Foundation, rather than an independently measured mainnet result.

How does Alpenglow change transaction finality?

Alpenglow’s Votor protocol changes how validators agree on blocks. Under TowerBFT, validators sent votes as on-chain transactions; with Votor, they send votes directly to one another and bundle them into certificates, allowing blocks to become final in one or two voting rounds, according to the Solana Foundation’s Alpenglow documentation.

The vote transactions no longer appear in blocks. That changes reported transaction totals, while the Foundation says execution, fees, programs and user transactions remain the same.

What changes for validators and developers?

Validators needed an Agave-based client on version 4.3.2 and at least 0.8 SOL in their vote account to keep voting and producing blocks, the Foundation says. Its documentation lists Agave, Jito-Solana and Harmonic Salsa as supported clients for the migration.

Developers who stream or count block data may need to adjust: the Foundation says data streams now identify banks within slots, and vote transactions have left blocks. Wallets and apps otherwise work as before, it says.

Alpenglow is live on mainnet; the Foundation says Rotor, a separate change to how block data spreads across the network, is planned for a later release but has no schedule.

Source material

• The Block’s report on the launch — theblock.co
• Solana Foundation’s Alpenglow documentation — solana.com