Alpenglow Is Live on Solana Testnet as Anza Retires TowerBFT and Votor Takes

Alpenglow, the consensus rewrite for Solana, is now running on the network's testnet. Anza confirmed at 18:12 UTC on 24 September 2026 that the handoff completed at slot 444625255: the Alpenglow genesis block formed, TowerBFT was retired, and testnet now finalizes blocks with Votor, with validator votes moved entirely off-chain.

Anza's guidance on what comes next is short: "Devnet is next. Mainnet-beta after our observation period." No mainnet date has been announced. When we reported on 22 September that Alpenglow was heading to testnet this week, the switch was still a scheduled event. It has now happened, on the day Anza planned.

How the TowerBFT-to-Votor handoff worked on Solana testnet

The Alpenglow migration ran as a countdown measured in slots. Anza posted at 17:50 UTC that the Alpenglow feature gate was active on testnet and that a 5,000-slot countdown, about 17 minutes, was running. At the boundary, validators confirmed a final TowerBFT block with 82% of stake behind it, and Votor took over from there. The first block produced under the new rules, which Anza calls the Alpenglow genesis block, is on Solana Explorer.

Triton One had identified the feature gate as SIMD-0326 in a guide for data consumers the day before, noting it would activate at epoch 1042. Only validators running Agave 4.3, Anza's validator client, took part. CoinDesk reported that Firedancer and Frankendancer, the clients built by Jump Crypto, do not yet support Alpenglow.

Roger Wattenhofer, one of the three authors of the Alpenglow proposal Anza published on 19 May 2025, confirmed the switch about 18 minutes after the handoff: "We just had a successful Alpenswitch on Testnet."

What moving Solana validator votes off-chain changes

Under TowerBFT, Solana validators record their votes on the chain itself, and a block becomes final once enough votes accumulate across 32 slots, according to CoinDesk. Votor has validators send votes directly to one another and finalize a block after one or two rounds. On testnet, that means vote transactions no longer take up space in blocks.

On mainnet-beta, where TowerBFT still runs, votes are most of the traffic. Solana Compass network data for 23 September shows an average of about 2,523 vote transactions per second against about 1,912 non-vote transactions per second, so votes made up roughly 57% of everything the chain processed that day. Alpenglow is designed to take that vote traffic off-chain once it reaches mainnet-beta.

The design target for Alpenglow is finality in about 150 milliseconds, down from roughly 12.8 seconds today, per the same CoinDesk report. Testnet's observation period is where that target meets a public network of independent operators, and the first real numbers will come from there. We covered what Alpenglow changes for validator costs and finality when Anza's smaller test cluster produced its first results in August.

What changes for Solana RPC providers and data consumers

For most applications, the Alpenglow switch asks for nothing new. Triton One said that anyone already on Agave 4.3 with maxSupportedTransactionVersion set to 1 needs no further changes, and that every existing Dragon's Mouth stream, Triton One's real-time data feed, carries the same bytes at the same cadence.

Two things do change on the data side, per Triton One. Dragon's Mouth gains a blockFooter filter, and vote accounts now carry a BLS public key, which applications can read with getAccountInfo using jsonParsed encoding, with no new RPC method needed. Triton One advised teams that have not yet worked through Agave v4.3's breaking changes for RPC providers to start there, since testnet validators had to be on v4.3 before the switch or fork off.

Solana devnet next, mainnet-beta after Anza's observation period

Anza has not published a devnet date for Alpenglow or said how long the testnet observation period will last. The separate Agave v4.4 release schedule lists devnet feature activations resuming on 7 October and mainnet-beta feature activations resuming from 9 November, but it does not name Alpenglow among them.

Others are reading the timeline more aggressively. Jito Labs CEO Lucas Bruder, who posts as buffalu, wrote that Alpenglow, "a complete consensus rewrite for solana, went from whitepaper to testnet in ~1.5 years? and to mainnet within the next few weeks? on a ~$75B network? no one ships like solana." The whitepaper-to-testnet span checks out against Anza's May 2025 publication date. The mainnet timing is his view; Anza's own statement stops at the observation period.

Solana has now swapped out the rules its validators use to agree on finality on a public test network, using nothing more than a feature gate and a slot countdown. Anza has tied mainnet-beta to what it sees during the observation period, so testnet finality over the coming weeks is the number to watch.