Solana Activates Alpenglow Upgrade on Mainnet-Beta, Cutting Finality to 150ms

Solana activated its Alpenglow consensus protocol on mainnet-beta on Wednesday at slot 459,653,000 around 14:00 UTC, cutting the time required for a transaction to become irreversible from about 12.8 seconds to roughly 150 milliseconds, according to core engineering team Anza. The upgrade retired TowerBFT, the consensus system Solana had used since March 2020, after validators approved proposal SIMD-0236 with a 98% vote in September 2025. Under Alpenglow, validators transmit stake-weighted votes directly to one another rather than writing them into subsequent blocks, reaching immediate finality with 80% stake approval or across two voting rounds requiring 60% of stake each. The protocol is designed to keep operating with less than 20% of stake acting maliciously and another 20% offline, while automatically lengthening block times if 10 seconds pass without a finalized block. Developers at Jump Crypto's Firedancer team have proposed removing Solana's cap of 60 million compute units per block following Alpenglow's rollout so blocks can scale with the fastest validators, while Anza also has uncommitted plans for Rotor data propagation updates and a post-quantum design called Quantumglow. "This is the largest, most ambitious blockchain upgrade since 'The Merge' and Anza took it from a white paper to running on mainnet in under 18 months." — Brennan Watt, CEO of Anza.