Solana’s consensus rewrite Alpenglow has moved from closed rehearsal environments onto the network’s public test clusters, but core developers are explicitly cautioning that no mainnet activation date has been set. Anza, the maintainer of the Agave validator client, confirmed that Alpenglow completed its testnet handoff on September 24, 2026 at slot 444,625,255, and its devnet migration on September 25 at slot 504,148,999. In both cases, an Alpenglow genesis block formed, TowerBFT was retired, and the new Votor system began finalizing blocks with validator votes moving off-chain.
The cutover followed a predefined sequence: a feature gate opens at an epoch boundary, a 5,000-slot countdown lasting roughly 17 minutes runs, and at the boundary validators confirm a final TowerBFT block with 82 percent of stake before Votor takes over. Anza said devnet would be next, followed by mainnet-beta only after an observation period. The upgrade targets dramatically faster finality: roughly 100 milliseconds when a large stake share agrees in one round, or about 150 milliseconds if another round is needed, compared with roughly 12.8 seconds under TowerBFT. Solana Foundation engineer Ilan Gitter reported a clean testnet handoff with more than 25,000 transactions per second and 150-millisecond finality, while co-founder Anatoly Yakovenko responded with “You are not ready for this.”
Despite speculation pointing to a September 28 mainnet launch, the upgrade did not go live on that date. Roger Wattenhofer, head of research at Anza, pushed back on the idea of moving a major consensus overhaul into production after only days of testing, writing: “Why would we test a protocol for only a few days before activating it?” and concluding: “There is no Alpenrush.” Yakovenko reinforced the message on September 27 with a one-word post: “decel.”
The September 28 date appears to have originated from the Agave v4.3 validator client release schedule, which marked that day as the resumption of mainnet-beta feature activation — not as an Alpenglow launch date. Solana Explorer continued to list SIMD-0326: Alpenglow among upcoming features on September 29, with testing active on devnet. Anza’s v4.4 schedule reportedly lists November 9 as another tentative feature-activation window, but that also is not a confirmed Alpenglow mainnet date. Alternative clients Firedancer and Frankendancer still lacked Votor support at the time of the public migrations, and the later Rotor component remains scheduled separately. For now, validators and application teams are in an observation phase to test certificate behavior, client diversity, and whether “confirmed” and “finalized” can safely collapse into one state before any mainnet-beta transition.
