Alpenglow activates on Solana's public testnet, retiring TowerBFT there

Solana/Alpenglow consensus

Anza confirmed that Alpenglow, Solana's new consensus protocol, activated on the public testnet at slot 444,625,255 on 24 September, replacing the TowerBFT voting system there. Validators now exchange votes directly instead of posting them as on-chain transactions, aiming to cut the time until a block is final from about 12.8 seconds to about 150 milliseconds. Mainnet is not switched yet: only one validator client supports it so far.

• Finality rule: a block is final after one voting round with 80% of stake, or after two rounds with 60%.
• Fault model: tolerates 20% malicious stake plus 20% crashed stake, instead of TowerBFT's one-third rule.
• Slots stay about 400 ms; fees, transaction format and wallets are unchanged. Vote costs move from on-chain fees to admission tickets burned each epoch.
• Only Anza's Agave 4.3 client took part. Firedancer does not support the new voting yet, so this was a one-client test.
• Before mainnet: a second client, an observation period, and updates by indexers, bridges and exchanges that assume 32-slot finality. The ~150 ms is a design target.