Solana Alpenglow Goes Live on Devnet TowerBFT Retired

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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.

What Went Live, and When

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.

Votor Is the Part That Shipped

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.

What “Solana Alpenglow” on Mainnet Really Means

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.

The Governance Vote Behind Alpenglow

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.

The 150ms Finality Target, in Context

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.

What Changes for Validators and Apps

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 Price and Market Reaction

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.

What to Watch Next

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.