Solana schedules Alpenglow upgrade for 21 October, targeting 150 ms finality

Solana has set 21 October as the activation date for Alpenglow, the biggest change to how the network reaches agreement since it launched in 2020. The upgrade aims to make transactions final — impossible to reverse — in roughly 150 milliseconds.

What changes

Alpenglow replaces TowerBFT, the voting system validators use today. At the moment validators submit their votes as ordinary transactions recorded on-chain. Under Alpenglow they exchange votes directly and bundle enough approvals into a certificate that finalises a block after one or two rounds of voting.

The 150 ms figure is a target; the Solana Foundation notes real-world performance will depend on network conditions.

Why it matters

A Solana payment already looks successful almost instantly. Alpenglow is about a stronger guarantee arriving almost as fast — useful for a merchant waiting for certainty before handing over goods, or a bridge waiting before it releases funds on another chain.

Things to watch on the day

• Transaction counts may drop sharply. Because validator votes will no longer appear as transactions, headline TPS figures could fall even if real usage is unchanged.
• Validator costs change. Voting fees of roughly 1 SOL per epoch disappear, replaced by a flat admission fee of 0.8 SOL.
• Client software. Operators need software built on Agave 4.3.0; Firedancer and Frankendancer will not support the initial migration, so their operators must switch temporarily.

Timing

The switch is scheduled for epoch 1064, expected around 15:00 UTC on 21 October. The old voting system stays in place for the first 5,000 slots, with Alpenglow taking over roughly 18 minutes later, according to CoinDesk.