Solana sets October 21 for Alpenglow activation, targeting transaction finality in 150 milliseconds
Key Facts
The Solana Foundation has set October 21, 2026, to begin activating the Alpenglow upgrade on mainnet, aiming to accelerate transaction finality by changing the consensus mechanism. The foundation said activation is scheduled for the start of epoch 1064, estimated to begin at around 13:20 UTC. When unveiling the design, Anza set a target of about 150 milliseconds for median finality time, compared with about 12.8 seconds under Tower BFT. The latency estimates were based on simulations using the mainnet stake distribution and excluding computational overhead. The upgrade changes how validators agree on blocks, while the mechanism for executing programs and transactions remains unchanged, according to the foundation.
Under the new consensus mechanism, the "confirmed" and "finalized" transaction states become equivalent, according to Anza's documentation on commitment levels. The documentation ties block finality to a finalization vote from more than 60% of stake, or a notarization vote from more than 80%. The design thus allows finality through either voting path, subject to its respective threshold. Anza says the protocol tolerates up to 20% adversarial stake, alongside 20% unresponsive stake. The planned transition follows the company's publication of the original design white paper on May 19, 2025, as part of a development process that began the previous year.
The transition will also change the transaction counts displayed on network dashboards, as validator vote transactions are removed from blocks. The Solana Foundation warned that the displayed count will fall sharply without a decline in actual activity, requiring those dashboards to adjust their comparison baselines. For the transmission of finality information, Anza allows nodes outside the admitted validator set to receive Votor messages directly through a partnership with an admitted validator. The company said "the additional delay is primarily the network communication time between partner nodes." These nodes can also learn of finality upon receiving a subsequent block carrying the certificate, but information arriving through this path is delayed compared with receiving consensus messages directly.
For validator operations, Anza sets the admission ticket fee at 0.8 SOL per epoch, according to its vote account guide. The fee is burned from each admitted validator's vote account once per epoch. In a separate update ahead of Alpenglow, Solana reduced slot time from 400 to 200 milliseconds, according to the Solana Foundation. The final step in that reduction took effect at the start of epoch 1053 on October 9, 2026. That initiative concerns slot times, while Alpenglow targets transaction finality time through the consensus mechanism.
The reduction in slot times also shortened the expiration window for the blockhash used in transactions to 30 seconds, from 60 seconds previously, according to the Solana Foundation's update page. This reduces the time available to complete transaction signing before the blockhash expires. The scope of the planned Alpenglow activation focuses on consensus, with the foundation summarizing the status of transaction execution by saying: "Execution is untouched." The Rotor phase, intended to replace the Turbine mechanism for propagating block data, has no set date so far. The network's upgrade path thus spans separate changes to slot times, consensus and block data propagation, each with its stated scope.
Ahead of the planned activation on October 21, the Solana Foundation is asking validators to update their client software in preparation for the transition. The foundation specified version 4.3.2 of Agave, Jito-Solana or Harmonic Salsa among the readiness requirements. This includes operators of Firedancer and Frankendancer, who must switch to one of the specified alternatives before the activation epoch begins, according to the foundation's instructions. Operational preparations also involve the vote account from which the validator admission fee is periodically deducted. Anza warned in its guide to these accounts that "commission income is not guaranteed to cover the validator admission ticket fee."