Solana Sets a Date for Its Next Major Upgrade

Solana has locked in October 21 for Alpenglow, a full replacement of the system its validators use to reach consensus. The switch is tied to epoch 1064, which the Solana Foundation expects to begin around 15:00 UTC that Wednesday.

Alpenglow retires TowerBFT, the current system the network uses, and aims to make transactions final in roughly 150 milliseconds. Finality is the moment a transaction becomes irreversible, and under TowerBFT that currently takes about 12.8 seconds.

On Solana today, a payment is confirmed pretty quickly, but that’s not a guarantee. Until TowerBFT runs out its 13 second clock, the block could in theory still be dropped.

That small doubt is why anyone handling real money tends to wait out the full window. With finality at around 150ms, the irreversible answer arrives almost as fast as the optimistic one, which is what a checkout counter taking SOL or a DeFI application, or a trading desk settling a position actually needs.

TowerBFT works by having validators post their votes as on-chain transactions, and a block only counts as final once 32 slots’ worth of those votes pile up. Votor, the voting protocol shipping with Alpenglow, takes votes off the chain, so validators message each other directly, package the votes into certificates, and can lock in a block after a single round of voting, or two at most.

When 80% or more of stake backs a block in the first round, it finalizes on the spot. If support lands between 60% and 80%, a second round with 60% thresholds decides whether the block is finalized or skipped, and the Foundation says the design tolerates 20% malicious stake plus another 20% offline.

Ordinary users don’t need to do anything, and wallets and apps should behave as they do now. The Solana Virtual Machine, transaction formats, programs, and fees are left alone, while for developers the “confirmed” and “finalized” commitment levels become one and the same.

Each vote account also needs 0.8 SOL on top of its rent-exempt balance to pay the new Validator Admission Ticket, a per-epoch fee of the same size that gets burned. It replaces the roughly 1 SOL per epoch validators spent on vote transaction fees under TowerBFT, and a validator that can’t cover it sits out voting and block production for the following epoch.

The feature gate turns on as epoch 1064 begins, yet TowerBFT stays in charge for another 5,000 slots, roughly 18 minutes, before Alpenglow takes control at slot 459,653,000. This assures stability and prevents any issues during transition.

Validators approved Alpenglow in September 2025, when the SIMD-0326 proposal passed with 98.27% of votes cast in favor. In May, Anza Lead Economist Max Resnick told Decrypt the team was looking at a late Q3 or early Q4 mainnet activation, so everything is going according to schedule.

October 21 delivers only Votor, the first half of Alpenglow. Rotor, a replacement for Turbine, the system Solana uses to broadcast block data between validators, comes later and still has no date.