Alpenglow, the consensus protocol built to replace Solana’s TowerBFT, will switch on for mainnet-beta on Wednesday, Oct. 21, Solana software developer Anza said on X on Tuesday. Anza put the go-live at about 14:50 UTC.
“18 months of work for a migration that happens in one slot,” the company wrote, adding that finality would fall “from seconds to ~150ms.”
The mainnet date comes after Alpenglow took over consensus on Solana’s testnet on Sept. 24 and on devnet a day later. Anza’s Alpenglow page says the team picked the mainnet date only after a period of watching those earlier networks, and that operators rehearsed the migration numerous times over the last five months.
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How the Handoff Works
According to Anza’s page, the process begins when a feature gate, SIMD-0384, turns on at an epoch boundary. That starts a 5,000-slot countdown during which blocks hold nothing but validator votes, so they can be rolled back without losing any user transactions. When the countdown ends, validators certify an Alpenglow genesis block backed by 82% of stake, pass consensus to the new voting component, Votor, and resume processing user transactions. Anza expects that step to take hundreds of milliseconds, after which TowerBFT is retired.
Under Alpenglow, validator votes move off the chain as BLS-signed messages that are combined into a single certificate, which Anza says frees up block space. The page says the network can keep running with up to 40% of stake offline or misbehaving, split evenly between the two, compared with TowerBFT’s tolerance of under 33% adversarial stake.
Anza’s page lists a bug bounty of more than 25,000 SOL, work from 115 security researchers, a simulation across 1,500 nodes and nine at-scale migrations as part of the testing.
The Road to Mainnet
Solana validators approved Alpenglow in September 2025, with more than 98% voting in favor. In May, Anza opened it to a community test cluster, and Solana co-founder Anatoly Yakovenko said at the time that mainnet activation could come the following quarter if testing went smoothly. TowerBFT finality runs about 12.8 seconds.
Anza’s page names Rotor, a replacement for the tree that Solana uses to spread block data across the network, along with faster handoffs between block leaders, as later work.
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