Solana Schedules Next Major Upgrade

Solana Sets October 21 for Alpenglow Upgrade, Promising Near-Instant Transaction Finality

Solana has scheduled October 21 for the rollout of Alpenglow, a comprehensive system upgrade designed to replace the current consensus mechanism used by its validators. The transition is slated to coincide with the start of epoch 1064, which the Solana Foundation anticipates will commence around 3:00 PM UTC on that Wednesday.

Alpenglow will supersede TowerBFT, the existing consensus system, with the ambitious goal of achieving transaction finality in approximately 150 milliseconds. Transaction finality signifies the point at which a transaction becomes irreversible. Under the current TowerBFT system, this process takes around 12.8 seconds.

While payments on Solana are currently confirmed with considerable speed, this confirmation does not guarantee irreversibility. Until TowerBFT completes its 13-second cycle, there remains a theoretical possibility that a block could be discarded. This lingering uncertainty compels entities handling significant financial transactions to await the full confirmation window. With finality reduced to about 150 milliseconds, the irreversible confirmation will arrive almost as swiftly as the initial optimistic one, a crucial improvement for applications like checkout systems accepting SOL, decentralized finance (DeFi) platforms, and trading desks settling positions.

TowerBFT operates by having validators submit their votes as on-chain transactions. A block is only considered final once votes from 32 slots have accumulated. Votor, the voting protocol integrated with Alpenglow, shifts vote processing off-chain. This allows validators to communicate directly, bundle votes into certificates, and achieve block finality after a single round of voting, or at most two.

If 80% or more of the staked assets back a block in the initial round, it is finalized immediately. Should support fall between 60% and 80%, a second round with a 60% threshold determines whether the block is finalized or skipped. The Solana Foundation states that this design can tolerate up to 20% malicious stake and an additional 20% of offline stake.

Alpenglow Mainnet Activation

Alpenglow is set to go live on the mainnet-beta on Wednesday, October 21, at approximately 2:50 PM UTC. This upgrade represents 18 months of development for a migration that will occur within a single slot, drastically reducing finality from seconds to around 150 milliseconds.

Ordinary users will not need to take any action, and wallets and applications are expected to function as they do currently. The Solana Virtual Machine, transaction formats, programs, and fees will remain unchanged. For developers, the distinction between “confirmed” and “finalized” commitment levels will effectively disappear.

Each vote account will require an additional 0.8 SOL, beyond its rent-exempt balance, to cover the new Validator Admission Ticket. This is a per-epoch fee of the same amount that will be burned. It replaces the approximately 1 SOL per epoch that validators previously spent on vote transaction fees under TowerBFT. Validators unable to cover this fee will be excluded from voting and block production for the subsequent epoch.

The feature gate for Alpenglow will activate at the beginning of epoch 1064. However, TowerBFT will continue to manage consensus for an additional 5,000 slots, approximately 18 minutes, before Alpenglow assumes full control at slot 459,653,000. This staggered approach is designed to ensure stability and mitigate any potential issues during the transition.

Validators approved Alpenglow in September 2025, with the SIMD-0326 proposal passing with 98.27% of the votes cast in favor. In May, Anza Lead Economist Max Resnick indicated to Decrypt that the team was targeting a late Q3 or early Q4 mainnet activation, suggesting the current timeline is proceeding as planned.

The October 21 deployment will introduce Votor, the first component of Alpenglow. Rotor, which will replace Turbine—Solana’s system for broadcasting block data among validators—is slated for a later release, with no specific date yet announced.