Solana switches mainnet to Alpenglow consensus

Solana activated Alpenglow on its mainnet on October 21, replacing TowerBFT with a new system for validators to agree on transactions. The change targets finality — the point when a transaction can no longer be reversed — in about 150 milliseconds, down from about 12.8 seconds under TowerBFT, according to the Solana Foundation’s Alpenglow page.

The switch took effect in epoch 1064, which began at about 13:36 UTC. Solana kept using TowerBFT for 5,000 more slots, then Alpenglow took over at slot 459,653,000. The Foundation says 446 of the network’s 654 validators certified the preceding block.

How does Alpenglow change validator voting?

Alpenglow’s first phase, called Votor, lets validators send votes directly to each other and combine them into certificates. Under TowerBFT, validators sent votes as transactions, and a block became final after enough votes accumulated over 32 slots. The Foundation says Votor can finalize a block in one or two rounds of voting.

That removes vote transactions from blocks. Solana’s reported transaction counts may therefore change, even if user activity does not. The upgrade changes how the network agrees on and finalizes blocks; it does not change transaction execution, fees or the way users send transactions, the Foundation says.

Does the 150-millisecond target mean transactions are already that fast?

Not necessarily. The Foundation describes 150 milliseconds as Alpenglow’s target. Decrypt reported that Anza, the Solana development team, gave that figure when the upgrade went live. The available reports do not establish that every mainnet transaction now reaches finality in that time.

The handoff itself is confirmed: the Foundation says TowerBFT’s final block was slot 459,652,999, and Alpenglow consensus began on the next slot. Decrypt also reported the change at slot 459,653,000 in its report on Alpenglow going live.

What remains to come after the switch?

Alpenglow is planned in two phases. Votor is live; Rotor, which is intended to change how block data spreads across the network, is planned for a later release and has no schedule yet, according to the Foundation.

For users, the Foundation says no action is needed: wallets and apps work as before. Validator operators face specific requirements. The Foundation says they need a supported Agave-based client and at least 0.8 SOL above the vote account’s rent-exempt minimum to pay an admission fee each epoch. Validators that do not pay will not vote or produce blocks in the next epoch.

References

• Solana Foundation’s Alpenglow page — solana.com
• report on Alpenglow going live — decrypt.co