
Solana Alpenglow is live on testnet and devnet. Explore its 150ms finality target, Votor rollout, and what remains before mainnet activation.
Author: Kritika Gupta
28th September 2026- Solana Alpenglow, the biggest change to Solana’s consensus in years, is now live on public devnet and testnet. Anza retired TowerBFT on both networks in late September. Mainnet, though, still runs the old consensus and carries no launch date.
High Signal Summary For A Quick Glance
Solana Armenia
@SuperteamAM
@solana alright, show us what’s under the hood 👀
The Alpenglow whiteboard session the world has been waiting for https://t.co/6Vden5AxG5
02:39 PM·Sep 28, 2026
Solanaboy
@okpebenbela
@solana the world was waiting for it to stop shitting itself, not a whiteboard
The Alpenglow whiteboard session the world has been waiting for https://t.co/6Vden5AxG5
02:38 PM·Sep 28, 2026
Erik
@ErikWeb3X
@solana I was waiting for it too, they say it's cool, new technology. We'll put it to the test.
The Alpenglow whiteboard session the world has been waiting for https://t.co/6Vden5AxG5
02:30 PM·Sep 28, 2026
High attention and emotional sentiment detected.
The rollout landed in two quick steps. Testnet switched over on Thursday 24 September, and devnet followed a day later. In both cases, the network formed an Alpenglow genesis block and shut off TowerBFT for good.
Anza completed the testnet handoff at slot 444,625,255 on 24 September. The devnet handoff then followed at slot 504,148,999 on 25 September. Solana Explorer now lists devnet consensus as Alpenglow from that genesis slot.
Each switch used the same countdown. First, a feature gate armed the upgrade. Then a 5,000-slot timer, roughly 17 minutes, ran down to the handoff. Finally the last TowerBFT block sealed, and Votor took over.
Alpenglow has two halves, and only one shipped so far. Votor handles voting and finality, and it is the piece now running on the test networks. Rotor, a planned replacement for block propagation, is held back for a later proposal.
So today’s clusters change how validators vote, not how blocks travel. Turbine still spreads shreds across the network. Execution on the SVM also stays the same, so most apps see no difference in how transactions run.
Under Votor, validators stop posting vote transactions on-chain. Instead, they send votes to each other and bundle them with BLS signatures into certificates. A block with strong notarization can then finalize in a single round.
One side effect is worth flagging early. Vote-transaction counts on explorers will fall once Alpenglow reaches mainnet, even if real usage holds steady. CoinDesk flagged this shift directly.
Solana Alpenglow rollout
Anza presents a new consensus design for Solana.
The proposal receives 98.27% Yes votes from participating stake.
Votor replaces TowerBFT on devnet. Mainnet-beta still runs TowerBFT.
Anza plans the migration after an observation period. No date has been announced.
Anza’s message stays consistent. The path runs testnet, then devnet, then mainnet-beta after an observation period. The @solana_devs primer on Monday said mainnet is “coming soon,” yet that is not a dated commitment.
The Solana Foundation upgrade page backs this up. Its status table reads testnet active, devnet active, and mainnet not activated. No epoch or calendar date appears anywhere on it.
One date keeps causing confusion, however. On 28 September, Agave v4.3 feature activations resume on mainnet-beta. That is a general schedule row, not an Alpenglow flip, and CoinDesk’s 26 September report said the same.
A mainnet switch also depends on more than Agave. Right now, Firedancer and Frankendancer are marked not supported for the Alpenglow feature gate. So multi-client readiness stays a real gate, not just a formality.
Solana consensus: before and after
Votor is live on testnet and devnet. Alpenglow is not active on mainnet-beta. The ~150 ms figure is a target, not a measured mainnet result.
Validators actually approved the change more than a year ago. SIMD-0326 passed on 2 September 2025, with 98.27% voting yes and 1.05% voting no. About 52% of stake took part, according to @SolanaStatus.
The proposal came out of Anza’s research group. ETH Zurich professor Roger Wattenhofer leads it, alongside former PhD students Quentin Kniep and Kobi Sliwinski. Meanwhile, Ashwin Sekar owns the Agave implementation on the feature-gate tracker.
Speed is the headline. Solana Alpenglow targets finality of about 100 to 150 milliseconds after a block spreads, with a median near 150. TowerBFT, by comparison, takes roughly 12.8 seconds.
That target still needs a caveat, though. The 150ms figure comes from simulations and smaller community clusters, not a load-matched mainnet test. CoinDesk described the speed as a target derived from simulations, and Anza frames it the same way.
The design also trades one kind of safety for another. Alpenglow tolerates 20% malicious stake plus another 20% offline, the so-called 20+20 model. That budget is lower on Byzantine faults than classic BFT, yet more forgiving of crashes.
Operators feel the cost change first. On-chain vote fees give way to a Validator Admission Ticket, burned each epoch. At 400ms slots, that ticket runs about 1.6 SOL per epoch.
Client choice matters here too. So far, the public Alpenglow clusters run Agave 4.3 only. Anza told Firedancer and Frankendancer operators to move to Agave before the gate, or their stake would not count.
Most apps, meanwhile, need little or no work. Wallets that send transactions and read balances should run unchanged. Indexers, Geyser plugins, and anything that parsed vote accounts must instead follow the Foundation’s migration checklist.
SOL rose across the switch week, but the cause stays unproven. On CoinGecko, SOL closed at $117.01 on 24 September, then $122.08 on devnet day. Trading volume also climbed to about $6.43 billion by 26 September.
Still, SOL was already rallying into testnet week, so the move reads as correlation at best. There was also no clean DeFi TVL spike tied to the devnet announcement. None of this is financial advice.
The real test comes later. Mainnet-beta activation waits on Anza’s observation period, and no one has said how long that lasts. For now, watch the feature-gate tracker and the Foundation status page for the flip.
Two open questions stand out. First, whether Solana Alpenglow holds its 150ms target under full mainnet load and MEV traffic. Second, when Firedancer ships a production Votor client. Until then, the switch stays on testnet and devnet.
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