Solana sets Oct. 21 for Alpenglow upgrade targeting 150-millisecond finality
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Summary
Solana has scheduled its Alpenglow upgrade for October 21, 2026, aiming to achieve transaction finality in about 150 milliseconds by replacing the existing TowerBFT voting system with an off-chain voting mechanism. This change will allow validators to exchange votes directly and finalize blocks more quickly but may cause a sharp drop in Solana’s reported transaction count as validator votes will no longer appear on-chain. Validators must upgrade to software based on Agave 4.3.0, and Firedancer and Frankendancer operators will need to switch software during the migration.
Why it matters
The upgrade aims to provide a stronger guarantee that Solana transactions cannot be undone shortly after appearing successful, which could enable merchants and cross-chain bridges to act faster when accepting payments or releasing funds. The reduction in on-chain validator vote transactions may distort transaction metrics without representing a decline in user activity.
Key context
Currently, Solana validators submit their votes as transactions recorded on the blockchain, incurring voting fees. Alpenglow will replace that process with off-chain votes combined into certificates finalizing blocks after one or two voting rounds, removing vote transactions from the blockchain and replacing previous voting charges with a flat admission fee. The migration is planned for epoch 1064 and will switch to Alpenglow roughly 18 minutes after the epoch begins.
Key numbers and entities
Solana Foundation, TowerBFT, Alpenglow, Agave 4.3.0, Firedancer, Frankendancer. Target transaction finality time of approximately 150 milliseconds. Validators’ current voting charges are about 1 SOL per epoch, replaced with a 0.8 SOL flat admission fee after the upgrade. Migration schedule set for epoch 1064, starting around 15:00 UTC on October 21, 2026.
What remains unclear
The source does not specify the exact expected network conditions affecting the 150-millisecond finality target or the long-term effects of the transaction count reduction on network usage reporting. It also does not provide details on how Firedancer and Frankendancer validators will manage the temporary software switch beyond the initial migration.