Solana has completed its most significant consensus upgrade since the network's launch in 2020. The Alpenglow upgrade, which went live on Wednesday, drastically reduces the time it takes for a transaction to become irreversible, cutting it from about 12.8 seconds to roughly 150 milliseconds. Validators retired the previous consensus protocol, TowerBFT, and switched to Alpenglow at slot 459,653,000 around 14:00 UTC, while maintaining the existing ledger.
Alpenglow simplifies the finality process, combining conditional confirmation and full finality into a single step. Under the new protocol, validators send votes directly to each other, weighted by stake. 'If you have 80% of the votes say yes, then it's immediately done,' said Roger Wattenhofer, Anza's head of research. The upgrade is designed to function even if up to 20% of stake acts maliciously or is offline.
The upgrade has been in development since May 2025, undergoing extensive testing, including public trials, security competitions, and rehearsals. Anza CEO Brennan Watt described it as 'the largest, most ambitious blockchain upgrade since 'The Merge,'' referring to Ethereum's 2022 switch to proof of stake. More upgrades are planned, including Rotor and Quantumglow, though no specific dates have been set.
Critics have raised concerns about potential centralization risks. Developers at Jump Crypto's Firedancer team proposed removing Solana's cap of 60 million compute units per block, which could favor well-funded operators. Despite this, the upgrade was approved by 98% of validators in September 2025, with the mainnet activation confirmed on October 13.