Solana Alpenglow Upgrade Set for October 21 Mainnet Launch

TLDR

• Solana’s Alpenglow upgrade goes live on mainnet on October 21, starting with epoch 1064.
• The upgrade replaces TowerBFT and targets transaction finality of about 150 milliseconds, down from 12.8 seconds.
• Vote transactions will leave blocks, so headline transaction counts and TPS figures will drop sharply.
• Validators must pay a new 0.8 SOL per-epoch fee that gets burned.
• Regular users do not need to take any action, and fees and apps stay the same.

Solana has set October 21 as the date for Alpenglow, an upgrade that replaces the system its validators use to agree on transactions. The change is tied to epoch 1064, which the Solana Foundation expects to start around 15:00 UTC that Wednesday.

Developer firm Anza said on October 13 that the upgrade took 18 months of work. The switch itself will happen in a single slot.

How Alpenglow Changes Solana’s Voting

Alpenglow retires TowerBFT, the network’s current consensus system. It aims to make transactions final in about 150 milliseconds, down from roughly 12.8 seconds today.

Finality is the moment a transaction can no longer be reversed. Solana confirms payments quickly now, but a block could in theory still be dropped until the full window passes.

For that reason, anyone handling real money often waits for full finality. Faster finality is aimed at uses like stores accepting SOL, DeFi apps and trading desks.

Under TowerBFT, validators post their votes as on-chain transactions. A block becomes final only after 32 slots of those votes build up.

Votor, the new voting protocol, moves votes off the chain. Validators message each other directly, bundle votes into certificates and can finalize a block in one or two rounds.

If 80% or more of stake backs a block in the first round, it is finalized right away. If support lands between 60% and 80%, a second round with a 60% threshold decides the outcome.

The Foundation says the design can handle 20% malicious stake plus another 20% offline.

Vote transactions will also leave blocks. Because of this, Solana’s headline transaction counts and TPS figures will drop sharply, even though real activity will not change.

What Users and Validators Need to Know

Regular users do not need to do anything. Wallets, apps, transaction formats, programs and fees stay the same.

For developers, the “confirmed” and “finalized” commitment levels will become the same thing.

Validators face a new cost. Each vote account needs 0.8 SOL on top of its rent-exempt balance to pay a Validator Admission Ticket, a per-epoch fee that gets burned.

This replaces the roughly 1 SOL per epoch validators spent on vote fees under TowerBFT. A validator that cannot pay will sit out voting and block production for the next epoch.

The rollout includes a short buffer. TowerBFT stays in charge for about 5,000 slots, or roughly 18 minutes, before Alpenglow takes over at slot 459,653,000.

Validators approved Alpenglow in September 2025, when the SIMD-0326 proposal passed with 98.27% of votes in favor. In May, Anza lead economist Max Resnick said the team was aiming for a late third quarter or early fourth quarter launch.

SOL was trading at $102.90 at the time of reporting, down about 10% over 24 hours.

The October 21 launch covers only Votor, the first half of Alpenglow. Rotor, which will replace the Turbine system used to share block data between validators, will come later and has no date yet.

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