Alpenglow Is Live on Solana Devnet as Anza Retires TowerBFT at Slot 504148999

Alpenglow, the new consensus protocol for Solana, is now running on devnet. Anza confirmed at 20:01 UTC on 25 September 2026 that the devnet handoff completed at slot 504148999: the Alpenglow genesis block formed and TowerBFT, the consensus mechanism still running on Solana mainnet-beta, is retired on that cluster. Anza linked the devnet genesis block on Solana Explorer.

Devnet is the public network where app developers deploy and test programs before mainnet, and Anza addressed its announcement to them directly: "test your programs and integrations now during our observation period leading up to mainnet-beta migration." No mainnet-beta date has been announced.

How the Alpenglow handoff ran on Solana devnet

The devnet switch followed the same script as testnet, one day later. Anza posted at 16:51 UTC that the Alpenglow feature gate would flip at epoch 1167, around 19:40 UTC, starting a 5,000-slot countdown, with Alpenglow taking over about 17 minutes later. The confirmation followed at 20:01 UTC.

On testnet, Anza reported the same handoff at slot 444625255 at 18:12 UTC on 24 September, adding: "Devnet is next. Mainnet-beta after our observation period." We covered that switch when Alpenglow went live on Solana testnet. Devnet arrived roughly 26 hours later, in the order Anza set out when Agave v4.3 reached general adoption: testnet, then devnet, then mainnet-beta.

The first phase of Alpenglow replaces TowerBFT with Votor. Under TowerBFT, the validators that run the network post their votes as transactions inside blocks. Votor has them exchange votes directly and collects the results into certificates. The Solana Foundation's Alpenglow migration guide puts TowerBFT finality at "about 12.8 seconds" and Alpenglow's target at "roughly 150 milliseconds." Devnet is where most application teams will first run their own code against that target.

What app developers should test on Alpenglow devnet

For most Solana programs, the switch changes nothing at the execution layer. The migration guide states: "Sending transactions and running onchain programs are not affected. Alpenglow changes consensus, not execution; the SVM, transaction formats, and fee mechanics are untouched."

The integrations around those programs are where the guide lists real changes, and devnet now runs all of them:

• Commitment levels converge. Under Alpenglow, "confirmed and finalized become the same thing," and the guide advises pointing new code at finalized, since confirmed will be deprecated and removed in a later release.
• Votes leave blocks. Transaction counts and TPS fall sharply, and the guide warns that every dashboard, benchmark and alert threshold whose baseline included votes needs re-baselining.
• A slot can carry more than one candidate block. Streaming and Geyser consumers should key buffers on (slot, bank_id) instead of slot alone; the guide references Yellowstone gRPC release candidate v16.0.0-rc10+solana.4.3.0.
• Proof of History ticks leave the shred stream, and the block leader now sets the Clock timestamp directly within a bounded range, replacing the stake-weighted median of validator votes.

Teams can check which regime a cluster is running with the getAgGenesisCert RPC method, which returns null under TowerBFT and a certificate once Alpenglow is active, or with the solana alpenglow-genesis-info CLI command.

Why Solana TPS charts will drop when votes leave blocks

The vote change is easy to misread as a collapse in activity once it reaches mainnet-beta, where TowerBFT still runs and vote transactions still share every block with user activity. Solana Compass network data for 18 to 24 September 2026 shows mainnet-beta processing 217.1 million vote transactions on 24 September against 168.8 million non-vote transactions, so votes were about 56% of the day's transaction count. Across the seven days, the vote share ranged between 54% and 59%.

When Alpenglow reaches mainnet-beta, headline transaction counts that include votes would fall by roughly that share with no change in user activity. Devnet already runs under that accounting, which makes it the place to fix analytics pipelines and alert thresholds first.

When Alpenglow reaches Solana mainnet-beta

Anza has not given a mainnet-beta date. Its devnet post ties the migration to an "observation period" and says nothing about its length. The separate Agave v4.4 release schedule lists mainnet-beta feature activations resuming on 9 November 2026, but the page does not mention Alpenglow.

With both public test clusters now running Votor, the remaining step is the network that carries real value. For teams building on Solana, the practical deadline is set by that observation period: anything that reads commitment levels, counts transactions or streams slot data can be tested against Alpenglow on devnet today, before mainnet-beta changes the same assumptions.