Solana Activates Alpenglow Upgrade on Mainnet, Ethereum Schedules Glamsterdam for Hoodi Testnet

Solana's Alpenglow upgrade is scheduled to activate on mainnet on Oct. 21, 2026, marking the largest change to the network's core protocol since launch [3, 4]. Meanwhile, the Ethereum Foundation announced that the Glamsterdam upgrade will activate on the Hoodi testnet on Oct. 26, 2026, following its deployment on Sepolia earlier this month ¹. Both upgrades aim to fundamentally alter how their respective networks process and validate blocks.

Solana's Alpenglow Replaces TowerBFT

Alpenglow replaces Solana's existing TowerBFT consensus mechanism with a new voting protocol called Votor [4, 5]. Under the new system, validators will exchange votes directly rather than submitting them as onchain transactions, aggregating them into compact certificates [3, 4]. This change is designed to reduce finality from roughly 12.8 seconds to approximately 150 milliseconds [3, 4].

The upgrade also alters the economic model for validators. The per-vote fee, which cost operators roughly 2 $SOL per day at the recent 200ms slot time, is replaced by a flat Validator Admission Ticket (VAT) of 0.8 SOL per epoch ³. Validators must hold at least 0.8 SOL above the rent-exempt minimum in their vote accounts before epoch 1064 begins on Oct. 21, or they will be excluded from consensus for the following epoch ⁴.

Alpenglow increases the network's fault tolerance, allowing it to tolerate up to 40% of stake being offline or misbehaving, compared to 33% under TowerBFT, though the share of actively malicious stake tolerated drops to 20% [3, 5]. The migration will run on an Agave-based client, as Firedancer is not supported during the transition [3, 4].

Ethereum Advances Glamsterdam on Testnets

The Glamsterdam network upgrade, which combines the Amsterdam execution layer upgrade with the Gloas consensus layer upgrade, activated on the Sepolia testnet on Oct. 6, 2026 [1, 2, 7]. It is now scheduled for the Hoodi testnet at epoch 132,352 (Oct. 26, 2026, 17:42:48 UTC) ¹.

Glamsterdam's headline features include enshrined proposer-builder separation (ePBS) and block-level access lists (BALs) [1, 2, 7]. ePBS integrates the separation between block proposers and builders directly into the consensus protocol, reducing reliance on trusted middleware [1, 2]. BALs allow clients to read state from disk and validate transactions in parallel, improving efficiency [1, 2].

At the activation epoch, Hoodi's gas limit will be raised to 200M, matching the increase implemented on Sepolia [1, 8]. The upgrade also adjusts gas pricing to better reflect state growth, with changes to state creation and access costs [1, 2]. Mainnet activation dates for Glamsterdam have not yet been announced [1, 2].

Implications for Developers and Operators

For Solana developers, transaction execution remains unchanged, but they must adapt to the new finality timelines and the potential for multiple candidate blocks per slot ⁴. Streaming interfaces like Geyser now tag events by bank ID, and the confirmed and finalized commitment levels will become synonymous ⁴.

Ethereum application developers are advised to test their contracts on the upgraded testnets, particularly assessing the impact of new gas accounting rules on contracts that rely on fixed gas stipends or hardcoded limits [1, 2]. Node operators on both networks face mandatory software updates to support the new consensus rules [1, 4].