Solana targets 150-millisecond transaction finality with Alpenglow activation
Key Facts
The Solana network is preparing to activate the Alpenglow upgrade on October 21, 2026, targeting a reduction in transaction finality time from about 12.8 seconds to 150 milliseconds, according to the Solana Foundation. Anza's documentation describes this as a target under normal network conditions, rather than a guaranteed deadline for every user interaction. The change concerns transaction finality, meaning a transaction is recorded permanently in the ledger and cannot be reversed. Under the new system, the "confirmed" and "finalized" transaction states become equivalent, according to Anza's commitment-level documentation. The upgrade focuses on consensus among validators, while transaction execution and fees remain unchanged, according to the foundation.
The change involves validators sending their votes directly to one another instead of including them as transactions within blocks, according to the Solana Foundation's explanation. Anza says the protocol replaces reliance on message exchange through a gossip mechanism between nodes with a faster direct communication method. With vote transactions removed from blocks, the total number of recorded transactions will decline even without a drop in underlying network activity. Explaining the transition's impact, the foundation said: "Transaction counts and transactions-per-second rates fall sharply." This change requires historical comparisons of activity indicators to be recalibrated, because totals before activation include vote transactions that will no longer count toward block totals afterward.
Alpenglow's rules cap the consensus set at 2,000 eligible validators, prioritizing those with the largest stakes, according to Anza's documentation. The protocol is designed to maintain consensus with 20% malicious stake and another 20% offline stake simultaneously, according to the Solana Foundation. On participation costs, the new mechanism imposes a validator admission ticket of 0.8 SOL per epoch. The ticket amount is burned from the vote account, according to Anza's operating guide. That compares with a cost of about 1 SOL per epoch that validators incurred for vote transactions under the previous consensus system, according to the foundation.
The planned activation follows a development process in which Anza presented the protocol in a blog post dated May 19, 2025. As part of security testing, the company allocated prizes of up to 50,000 SOL for a bug-finding competition, according to its official repository. The vulnerability submission window opened on August 5, 2026, at 16:00 UTC. The window closed on August 19, 2026, at 16:00 UTC. The mainnet step was preceded by Alpenglow's deployment on the development network at epoch 1167, at 19:30 UTC on September 25, 2026, according to the upgrade schedule published by the Solana Foundation.
Ahead of the transition, the foundation requires validators to use version 4.3.2 of the Agave client or one of the two clients built on it, Jito Solana and Harmonic Salsa. The transition does not support the Firedancer and Frankendancer clients, according to the upgrade instructions. The vote account must hold a sufficient balance for the admission ticket above the rent-exempt minimum, or the validator will lose eligibility to vote and produce blocks in the next epoch, according to Anza. The foundation also asks block-stream consumers to prepare for the possibility of multiple bank states within the same slot. Readiness requirements include handling the new bank identifier field in those streams.
The foundation has designated epoch 1064 for the start of mainnet activation, at about 13:20 UTC. The epoch's start time remains an estimate and may change depending on network slot timing. In subsequent development, the Rotor component follows the Votor component, according to the upgrade roadmap published by the Solana Foundation. Rotor aims to replace the Turbine block propagation mechanism with a single relay layer. The foundation has not set a launch date for that subsequent step.