Solana is set to activate its Alpenglow consensus upgrade on 21st October, 2026, retiring the TowerBFT voting system and targeting transaction finality of about 150 milliseconds.
What Happened?
- Solana’s Alpenglow upgrade replaces TowerBFT with Votor, a voting protocol that moves validator votes off the blockchain.
- Validators swap per-vote fees for a flat admission ticket, a change that cuts their voting bill by roughly 60%.
- Solana’s test network was wiped and restarted six times before a migration to the new system finally succeeded.
- Reported transactions per second may drop after the switch because vote transactions stop counting toward the total.
Votor moves validator voting off the chain
TowerBFT has every validator write its votes onto the ledger like any other transaction. A payment locks in only after enough of those votes pile up.
Votor gathers votes off-chain and compresses them with BLS signatures, a cryptographic method that folds many signatures into one compact proof. The resulting certificates can lock in a transaction in one or two rounds.
Estimates of today’s wait range from about six seconds to 12.8 seconds, the figure tied to TowerBFT’s deterministic finality. Testing points to some headroom below the 150-millisecond goal, with median finality on public testnet and devnet as low as 54 milliseconds.
The wait matters most in markets. Exchanges and payment apps hold off before treating a deposit as done, and prices can move before a trade settles. Ethereum, by comparison, needs roughly 13 minutes to reach full finality.
Alpenglow mode 🏔️ https://t.co/0VNnAbtPmr
— Solana (@solana) October 21, 2026
Robin Nordnes, founder and CEO of Raiku, which builds trading infrastructure on Solana, took a narrower view in an email to CoinDesk. He said:
The overhaul stays at the consensus layer. Solana’s execution layer and user interfaces are meant to stay the same, so wallets and apps shouldn’t need to change how they work. The design is built to keep the network running even if 20% of stake behaves maliciously and another 20% goes offline.
Dashboards will register the switch first. Reported TPS may dip after activation because TowerBFT counted vote transactions inside blocks, which padded Solana’s headline throughput figures. Once votes leave the chain, that padding goes away and more block space opens for user transactions.
Cheaper voting lands on a shrinking validator set
Validators currently burn about 2 SOL a day on vote fees, a cost that doubled after Solana cut slot times to roughly 200 milliseconds. Alpenglow replaces those fees with a Validator Admission Ticket (VAT) of 0.8 SOL per epoch, a period of about 24 hours. Operators also need Agave-based clients, typically version 4.3.2.
SIMD-0326, the Solana Improvement Document behind the change, won validator approval in September 2025 with 98.27% support. The year since went to testing, and not all of it went cleanly. Galaxy Digital, one of roughly 100 operators on the test network, said one migration attempt failed network-wide and had to be rolled back. A later migration cleared the way for launch.
The fee cut arrives as the validator count falls. Active validators dropped to 659 at the end of September from 696 three months earlier, according to Bitwise’s latest staking report. That count sits roughly 30% below a year ago, even with 69% of SOL’s supply staked.
Stake has concentrated, too. Solana Compass data shows the smallest group of validators controlling over a third of staked SOL shrank to 18 from 20 in a year. The ten largest validators’ share rose to 24.5% from 22.2%.
Bitwise attributed the decline to operating costs. A lower voting bill could ease that strain on smaller operators, though hardware, bandwidth and hosting expenses remain. Operators not yet on a compatible Agave client need one to take part once the switch completes.
The Bottom Line
Activation targets approximately 13:20 UTC. The switch begins with epoch 1064, runs through a 5,000-slot transition and lands at slot 459,653,000. The testnet failures never touched real funds, since that network was built to break. Mainnet has no such cushion.
