Solana switched on its Alpenglow upgrade on October 21, 2026, replacing the way its validators agree that a transaction is final. Validators are the computers that run the network, and finality is the point where a transaction can no longer be reversed. The upgrade targets about 150 milliseconds, down from about 12.8 seconds.
Under the old system, TowerBFT, validators voted by sending transactions, and a block became final once enough votes had stacked up over 32 slots. Alpenglow has validators send votes directly to each other and bundle them into certificates, so a block is final after one or two rounds of voting. Transaction execution, programs and fees stay the same. Only the first phase, called Votor, is live, and the second phase, Rotor, will change how block data spreads across the network and has no release date yet (Solana Foundation, Alpenglow upgrade page).
The upgrade's feature gate switched on at the start of epoch 1064, but the network kept running TowerBFT for the first 5,000 slots, about 18 minutes (Solana Foundation). Alpenglow took control at slot 459,653,000, around 1:54 pm UTC according to the foundation's dashboard (Cointelegraph).
Early readings of finality have varied. The dashboard showed 6.6 seconds at press time, according to Cointelegraph, and a single reading of 202 milliseconds on October 21 and 22, according to Altcoin Buzz. Neither is a sustained average, so the 150-millisecond target has not yet been shown to hold on mainnet.
For users, nothing changes, and wallets and apps keep working as before. Vote transactions no longer appear in blocks, so reported transaction counts and transactions per second drop sharply without any fall in real activity (Solana Foundation). Block time was cut separately, from 400 milliseconds to 200 milliseconds in four stages that finished in October 2026. The 150 milliseconds measures finality, not how often blocks are produced (Genfinity).
Validators approved Alpenglow in September 2025, with more than 98% voting in favor (Unchained). Firedancer and Frankendancer clients are not supported during the migration. Each voting validator now pays 0.8 SOL per epoch from its vote account, in place of the roughly 1 SOL per epoch in vote fees under TowerBFT (Solana Foundation).
