Solana schedules Alpenglow mainnet activation for Oct. 21

Solana plans to activate Alpenglow on mainnet on Oct. 21, replacing its TowerBFT consensus system with one targeting transaction finality in about 150 milliseconds, according to the Solana Foundation’s upgrade page. The target compares with about 12.8 seconds under TowerBFT, the Foundation says.

When will Alpenglow take over on mainnet?

The upgrade is scheduled for epoch 1064, expected to start at about 15:00 UTC on Oct. 21, 2026, the Foundation says. CoinDesk reports that Solana will continue using TowerBFT for the epoch’s first 5,000 slots, with Alpenglow consensus taking over roughly 18 minutes after the epoch begins.

How does the new consensus system work?

Under TowerBFT, validators record votes as transactions on Solana. The Foundation says Alpenglow will have validators send votes directly to one another and combine approvals into certificates, allowing a block to become final after one or two voting rounds.

The 150-millisecond figure is a target, not a guaranteed result: the Foundation says actual finality depends on network conditions. It also says the change affects consensus, while transaction execution, programs and fees stay the same.

What changes for validator operators?

The Foundation says validators must run an Agave-based client built on version 4.3.0 before the epoch begins. Firedancer and Frankendancer will not support the migration, so operators using either client must switch for the rollout.

Operators must also keep at least 0.8 SOL above the rent-exempt minimum in their vote account to pay the Validator Admission Ticket fee, according to the Foundation. Alpenglow removes vote transactions from blocks, so transaction counts that include those votes may fall after activation even if user activity does not, CoinDesk reports.

Sources

• Solana Foundation’s upgrade page — solana.com