Solana begins testing Alpenglow upgrade to reduce transaction finality to 150 milliseconds

Solana has commenced public testnet testing for its Alpenglow consensus upgrade, which is designed to reduce transaction finality times from 13 seconds to approximately 150 milliseconds. Developed by Anza, the upgrade replaces the TowerBFT consensus system with the Votor voting protocol, allowing validators to finalize blocks in just one or two direct voting rounds. The migration currently requires Agave 4.3 software and does not yet support Jump Crypto's Firedancer client. A tentative mainnet feature activation is scheduled for September 28, 2026, though a final Alpenglow launch date is not yet confirmed.

Consensus Upgrade and Finality Speed

• ▪The Votor protocol allows validators to reach agreement on a block after one or two voting rounds, removing the longer sequence of onchain consensus votes required under TowerBFT.
• ▪The Alpenglow upgrade replaces Solana's TowerBFT consensus system with a voting protocol called Votor, which allows validators to exchange votes directly.
• ▪Anza estimated the Solana Alpenglow upgrade's median transaction finality at around 150 milliseconds, down from approximately 13 seconds, with earlier simulations reaching as low as 100 milliseconds under favorable conditions.
• ▪The Solana Alpenglow upgrade is the largest consensus change in the history of the Solana network, according to developer company Anza.

Testnet Migration and Timeline

• ▪The Solana public test network uses tokens with no monetary value, allowing developers to test the Alpenglow migration and investigate problems without risking user funds.
• ▪Anza first moved the Solana Alpenglow upgrade into community validator testing in May 2026.
• ▪The Alpenglow testnet activation was still listed as pending on Anza's feature gate tracker early on Wednesday, September 23, 2026.
• ▪The Solana Alpenglow upgrade spent more than four months operating on a smaller community validator cluster before moving to Solana's established public test network

Agave 4.3 Software Deployment

• ▪Validators participating in the Alpenglow testnet migration must run Anza's Agave 4.3, as Jump Crypto's Firedancer and Frankendancer clients do not yet support the test, making the initial migration entirely dependent on Agave.
• ▪Anza recommended Agave 4.3 to all mainnet validators on September 21, 2026, after first rolling out Agave 4.3 to operators representing 10% and then 25% of the secured SOL stake
• ▪September 28, 2026, is listed in Anza's schedule as a tentative date for mainnet feature activation of Agave 4.3, but it is not a confirmed launch date for Alpenglow.
• ▪In August 2026, developers expected the Solana Alpenglow upgrade's 150-millisecond finality target to arrive through the Agave 4.3 software branch.