Solana moved its mainnet onto the Alpenglow consensus protocol on Wednesday, retiring TowerBFT, the voting system the network had used since 2020. “Alpenglow is now live on Solana mainnet,” the official Solana account posted at 13:59 UTC. Anza, the developer that built the protocol, had declared it live five minutes earlier.
The chain itself records the switch. Unchained’s queries of Solana’s public mainnet RPC show the final TowerBFT-era block, slot 459,652,999, stamped at about 13:54:00 UTC, and the network’s Alpenglow genesis certificate points to that block. Eight slots then passed with no block before slot 459,653,008 arrived at 13:54:03 UTC. Block heights continued in sequence, with no sign of a rollback.
That timing beat Anza’s own estimates. The team first set the switch for about 14:50 UTC, the date Unchained reported on Oct. 14, and, according to Solana Compass, later pulled its projection forward to around 14:00 UTC.
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The 150 Millisecond Claim
Both announcements put a number on the change. Anza wrote that finality was “reduced from 12.8 seconds to 150 milliseconds,” and the Solana account said the same.
The 12.8-second figure reflects Solana’s earlier 400 millisecond slots, and the Solana Foundation says slot times have since been cut to 200 milliseconds. Galaxy, which runs Solana validators, wrote in a pre-launch explainer that finality had come down to roughly 6 seconds under the shorter slots.
What Changes for Validators
Under Alpenglow, validators no longer submit votes as transactions. Votes now travel between nodes as BLS-signed messages that are aggregated into certificates, freeing blockspace for users. A block can be finalized in one round if 80% of stake votes for it, or in two rounds at 60%.
The design is meant to keep working with up to 20% of stake acting maliciously and another 20% offline. In place of per-vote fees, each voting validator now pays a flat 0.8 SOL per epoch. Galaxy has noted that vote transactions made up roughly three quarters of Solana’s traffic, and the Solana Foundation expects reported transaction counts and TPS to drop sharply.
Wednesday’s switch covers Votor, the voting half of the design. Rotor, which would replace Turbine’s block propagation, is slated for a later phase with no date set.
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