Solana swaps out its consensus engine on Wednesday, aiming to cut finality from about 13 seconds to 150 milliseconds, with a switch Anza says happens in a single slot

Solana is due to change how it agrees on blocks on Wednesday, without stopping the network. Anza, the developer firm behind the Agave validator client, said on October 13 that Alpenglow goes live on Solana's mainnet-beta on October 21 at about 14:50 UTC, after test runs on testnet on September 24 and devnet on September 25, per its announcement and Solana Compass. Anza describes it as 18 months of work for a migration that happens in one slot, per Solana Compass.

Alpenglow replaces TowerBFT, the consensus protocol Solana has used since launch. Its voting component, Votor, finalises a block in one round if 80% of stake responds, or two rounds at 60%, whichever comes first, per Anza. Votes become signed messages passed between validators rather than transactions in blocks, which frees block space, and Proof of History no longer paces block production. Anza targets finality of about 150 milliseconds against about 12.8 seconds today, per Solana Compass, and says the network can keep running with 20% of stake malicious and another 20% offline at once.

The migration, specified in SIMD-0384, runs live: a feature gate activates at an epoch boundary, blocks carry only votes from 5,000 slots later, and once 82% of stake signs a genesis certificate, Votor takes over and user transactions resume, per Solana Compass. Wallets and most apps need no changes, but validators must run an Agave-based client on a release built on Agave 4.3.0; Firedancer and Frankendancer are not supported during the switch, and the Firedancer family of clients holds about 16% of stake among the top 500 validators, by Solana Compass's count. Rotor, the second half of the design, is not yet scheduled.