Solana Alpenglow cuts finality from 12.8 seconds to 150ms

Solana replaces TowerBFT, the consensus it has run since launch, with Alpenglow today. The headline change is finality: the time before a transaction can no longer be reversed falls from 12.8 seconds to roughly 150 milliseconds, which is 85 times faster. Wallets and applications keep working, and holders need to do nothing at all.

“Wallets and applications keep working as usual. Holders have nothing to do.”

— Solana Foundation, Guidance to holders ahead of the switch

How the handover works

The handover is not a switch someone flips. The feature gate opens when epoch 1064 begins, TowerBFT stays in charge for another 5,000 slots, and Alpenglow takes control at slot 459,653,000. Anza published a target of about 14:50 UTC, and a slot number is a position in a queue rather than a time on a clock.

We measured the slots

So we measured the queue instead of trusting the clock. Over 75 seconds on the public mainnet RPC the network produced 346 slots, which is 0.217 seconds a slot. At that rate the 5,000-slot buffer works out to 18.1 minutes, which matches the roughly 18 minutes Anza quoted, so the measurement and the published figure agree.

Run it forward from the same reading. Epoch 1064 starts about 194 minutes after we measured, near 13:37 UTC, and slot 459,653,000 arrives around 13:55. Both numbers move if the network speeds up or slows down, which is exactly why different sources are quoting times an hour apart for the same event.

Half an upgrade, not all of it

One thing is being overstated elsewhere, and it matters. Today delivers Votor, the half of Alpenglow that changes how validators exchange votes. Rotor, the half that changes how new blocks are spread across the network, has no activation date. The upgrade arriving today is one of two parts, not the whole design.

For scale, Ethereum finalises in about 13 minutes, so 150 milliseconds is roughly 5,000 times quicker on that comparison. Speed is not the only thing a consensus has to do, though. The month already showed what happens when a chain has to stop: Qubic halted its own network to freeze stolen funds, and the ability to stop is a property of consensus too.

What settles today is narrow and watchable. Whether the handover completes at the slot without a restart, whether finality measured on-chain actually lands near 150 milliseconds rather than near a second, and whether Rotor gets a date. Solana funds took a record week in September on the promise of this kind of performance, so the number will be read as a product claim, not just an engineering one.

Informational material, not investment advice. Slot timing was measured on the public mainnet RPC on the morning of 21 October 2026, and the clock time of a slot-based event drifts with network speed.