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Solana's Alpenglow consensus is scheduled to switch on mainnet on October 21
Anza has set Wednesday, October 21, 2026 as the date Alpenglow replaces TowerBFT on Solana's mainnet-beta, announced on X this week. Anza says the change cuts finality from about 12.8 seconds to about 150 milliseconds and raises the share of stake the network can tolerate misbehaving.
- The switch happens at a feature-gate epoch boundary, with a 5,000-slot countdown in which blocks carry only validator votes, so they can be rolled back.
- Anza expects the handoff itself to take hundreds of milliseconds, so the switch is not literally instant.
- Fault tolerance rises to 40% of stake offline or misbehaving, versus under 33% adversarial stake for TowerBFT; these are Anza's claims, not independently verified.
- Validator votes move off-chain as BLS-signed messages combined into one certificate, which Anza says frees block space.
- Testing included a bug bounty of over 25,000 SOL, work from 115 security researchers, a 1,500-node simulation and nine at-scale migrations.