Solana’s Alpenglow consensus upgrade moves to public testnet

Solana’s Alpenglow consensus upgrade is moving to public testnet, where developers can test Votor, the new voting protocol designed to cut block finality from about 12.8 seconds to a target of roughly 150 milliseconds. CoinDesk reported on Sept. 23 that the testnet migration was under way, although Anza’s tracker still listed the switch as pending early that day.

What changes in Alpenglow’s consensus process?

Alpenglow replaces TowerBFT’s on-chain voting process with Votor, which sends votes directly between validators and bundles them into certificates. Under TowerBFT, validators record votes as transactions, and blocks become final after votes accumulate across 32 slots. The Solana Foundation’s Alpenglow proposal defines two paths to finality: one round if a certificate represents votes from 80% of stake, or two rounds with 60% thresholds.

The 150-millisecond figure is a target, not a fixed guarantee. Solana’s upgrade documentation describes it as an expected finality time that varies with stake distribution and whether a block finalizes in one round or two. Finality is the point at which a block can no longer be reversed under the protocol.

What will validators test on public testnet?

The test checks whether the wider group of computers and services already running Solana can migrate to Alpenglow together. CoinDesk reported that the upgrade had spent more than four months on a smaller network built for testing before its move to the public test network.

Validators joining the initial test need Agave 4.3, Solana’s main validator software, maintained by Anza. Anza recommended that version to mainnet validators on Sept. 21 after an initial rollout to operators representing 10% and then 25% of the SOL securing the network. The first testnet migration does not support Firedancer or Frankendancer, alternative validator software built by Jump Crypto.

Does the test mean Alpenglow is launching on mainnet?

No mainnet launch date is confirmed. CoinDesk reported that Sept. 28 was listed as a tentative date for enabling features included in Agave 4.3 on mainnet, but that date was not an Alpenglow launch date. The testnet switch itself was still pending on Anza’s tracker at the time of the report.

Alpenglow changes how validators agree on blocks and reach finality. It does not change transaction execution, wallets or how users send funds, according to CoinDesk. Solana’s upgrade documentation says Votor is the first phase; Rotor, a planned replacement for the Turbine block-propagation protocol, is scheduled for a later release after Votor is adopted.