Solana Sets October 21 for Alpenglow Activation, Targeting Transaction Finality in 150 Milliseconds
Key Facts
The Solana Foundation has set October 21, 2026, for activation of the Alpenglow upgrade on mainnet, aiming to accelerate the time it takes transactions to become final on the ledger. Protocol developer Anza is targeting median finality of about 150 milliseconds in a change to the network's consensus system. That compares with about 6 seconds before the transition, according to Galaxy's estimate at the current slot time of 200 milliseconds. The upgrade also removes validator voting transactions from blocks, according to the Solana Foundation. The "confirmed" and "finalized" commitment states become equivalent under the new system, according to Anza's documentation, changing the transaction confirmation states used on the network.
The consensus change follows the implementation of the final step in reducing slot times on October 9, 2026, at the start of epoch 1053, according to the Solana Foundation. When presenting the Alpenglow design, Anza calculated latency using a simulation of mainnet's stake distribution at the time. The company excluded computational overhead from that simulation, leaving the target time tied to the basis used to calculate it in the design. Anza designed the protocol's resilience model to tolerate adversarial stake of up to 20% of total stake. The model also tolerates 20% of stake being unresponsive, according to the company's presentation of the protocol and its resilience conditions.
For wallet and application users, the Solana Foundation said the transition requires no action, while Galaxy confirmed that the way staking rewards are earned will remain unchanged. Describing the upgrade's impact on staking, Galaxy said: "Nothing changes in how stake earns rewards." For network operators, the foundation said the Firedancer and Frankendancer clients are not supported during the migration to Alpenglow. Jito's transition plan includes placing all mainnet "BAM" nodes in maintenance mode. Jito said transaction bundles from the block engine will continue to operate as usual during the maintenance period.
Validator operations under Alpenglow include an admission ticket costing 0.8 SOL per epoch, according to Anza's vote account guide. The company's documentation caps the admission set at 2,000 eligible validators, giving priority to those with the most stake. The admission system thus combines a recurring ticket with a ranking of eligible validators by stake size, within the set's specified cap. Ahead of the transition date, aggregate signing keys were activated on mainnet on July 8, 2026, according to the Solana Foundation. The validator admission ticket gate was also activated on July 22, 2026, as part of preparations ahead of the new consensus system's activation date.
Tests before the mainnet date included a setback in the transition process, with Galaxy saying it witnessed a failed attempt on testnet. That attempt was followed by a rollback to the previous system, according to the company's account of its experience with the consensus change. The previous release plan called for extensive testing of Alpenglow in Agave 4.2, without activating it on mainnet in that release. The Solana Foundation linked those tests to paving the way for expected activation in Agave 4.3, according to the previous release plan. The replacement of the "Turbine" block propagation mechanism with the "Rotor" upgrade is scheduled for a later phase, so the initial transition does not include replacing the data propagation layer.
Under the announced October 21 schedule, activation epoch 1064 begins at about 13:20 UTC, but the actual switch to the new consensus system does not occur immediately at its start. The network continues running "Tower BFT" for the first 5,000 slots of the epoch before switching to Alpenglow, according to the Solana Foundation. At the start of the same epoch, the first validator admission ticket is collected, according to Anza's guide. That collection covers admission for epoch 1065, meaning admission is funded ahead of the epoch to which the ticket applies. After activation, Jito plans to bring "BAM" nodes back into service gradually, according to its announced plan to resume their operation on mainnet.