Ethereum's Glamsterdam and Solana's Alpenglow Head Into Public Testing

Ethereum's Glamsterdam upgrade is scheduled to activate on the Sepolia test network on Oct. 6 at about 8:53 a.m. CT, with mainnet targeted for the fourth quarter of 2026 but no date set, bringing enshrined proposer-builder separation and block-level access lists designed for more capacity and parallel processing. Solana's Alpenglow upgrade, which aims to cut finality from about 12.8 seconds to roughly 150 milliseconds in simulations, is now live on Solana's devnet and testnet, also with no mainnet date.

Ethereum Glamsterdam: The Timeline

Ethereum developers confirmed Oct. 6 as the date for Glamsterdam's first public test on Sepolia, one of Ethereum's test networks, where software runs with tokens that have no real value, CoinDesk reported. Glamsterdam is scheduled to activate at epoch 353024, according to CoinInsider. An epoch is a fixed unit of Ethereum time, 32 slots of 12 seconds each; on Sepolia's clock, that epoch begins at about 8:53 a.m. CT on Oct. 6.

Client teams, the groups that build the different software implementations that run Ethereum nodes, have until Sept. 29 to release Sepolia-ready versions. That leaves seven days before the fork, the moment the network switches to the new rules, half the 14 days Ethereum's normal process reserves for security reviews and bug-bounty testing. Developers accepted the shorter window because Sepolia is relatively centralized and easier to recover if something breaks.

The next public test, on the Hoodi test network, is tentatively planned for Oct. 27, with the final decision depending on Sepolia's results. Ethereum.org lists mainnet as expected in Q4 2026, "date not yet confirmed."

What Glamsterdam Changes

The name combines "Amsterdam," the execution-layer upgrade, and "Gloas," the consensus-layer upgrade. Ethereum.org says the upgrade focuses on scaling the main chain, or layer 1, by reorganizing how the network processes transactions and builds and verifies blocks. Two headline features stand out.

Enshrined Proposer-Builder Separation (ePBS)

Today, Ethereum blocks are usually assembled by specialized "builders" and chosen by validators, the staked computers that secure the network, acting as "proposers," but that hand-off happens outside the core protocol. It relies on trusted third-party software called relays. Ethereum.org says this setup forces a rush to broadcast and execute transactions in a tight window of about two seconds, which limits how much data the network can handle.

Enshrined proposer-builder separation, or ePBS (EIP-7732; an EIP is an Ethereum Improvement Proposal, the formal spec for a change), writes the proposer-builder hand-off, including trustless payment to builders, directly into Ethereum's rules. According to Ethereum.org, this expands the propagation window, the time available to spread block data across the network, from about 2 seconds to about 9 seconds, allowing much larger blocks without straining the network.

Block-Level Access Lists (BALs)

Ethereum currently processes transactions one by one, because it does not know in advance which accounts each transaction will touch. Ethereum.org compares it to a single-lane road.

Block-level access lists (EIP-7928) attach a map to each block showing which parts of Ethereum's database the transactions will read and change, along with their final results. With that map, nodes can load data in parallel and group non-overlapping transactions to process them at the same time. Because the list includes final results, new nodes can also sync faster without replaying every transaction.

Together with changes to how gas, Ethereum's unit of computational cost, is priced, CoinDesk reports the upgrade is intended to support a block gas limit of about 200 million, making room for more payments and trades per block. A large private rehearsal had already raised its gas limit toward 200 million without losing finality, the point at which transactions can no longer be reversed, though CoinInsider notes the 200 million figure remains a test parameter, not a confirmed mainnet limit.

The 'Any Teenager' Warning

ePBS introduces in-protocol auctions where builders bid to supply blocks. On mainnet, bids cost real ether. On Sepolia, test ether is free, which opens the door to a Sybil attack, a tactic in which one actor creates many fake identities to overwhelm a system.

"I can just spin up a thousand builders, rotate them, offer very high bids, and not produce payloads," Ethereum consensus developer Potuz said on a core developer call, as reported by CoinDesk. "Any teenager can do this."

An attacker could repeatedly win auctions and then withhold the transactions, leaving blocks empty and disrupting testing. The attack would not threaten mainnet funds. Developers said existing safeguards fall back to locally built blocks only after several payloads go missing, and clients also need a way to identify and reject individual builders so attackers cannot return under new identities. CoinDesk also noted that production builder software from the Titan and Ultrasound teams had not yet completed a Glamsterdam fork transition.

Solana Alpenglow: Chasing 150-Millisecond Finality

On Solana, the headline upgrade is Alpenglow. Finality is the point at which a transaction can no longer be reversed. Alpenglow targets roughly 150 milliseconds, compared with about 12.8 seconds under Solana's current system, CoinDesk reported.

Alpenglow is now active on both of Solana's public test networks. Anza, the company building Solana's core software, announced the devnet switch on Sept. 25, a day after the separate testnet completed its transition. Devnet is where developers test applications with valueless tokens; testnet is used mainly to stress-test network software and validator operations.

The upgrade changes how validators, the computers that check transactions, agree on the network's records. They will exchange votes directly instead of recording them as transactions inside blocks, and agreement can take one or two voting rounds.

That has a side effect: Solana transaction totals that include validator votes will shrink even if user activity stays the same. The Solana Foundation has told data providers to adjust comparisons. Applications that simply send transactions and read balances need no migration, according to the Foundation's guide.

The 150-millisecond figure is a target derived from simulations, not a result demonstrated under live-market conditions, and wallet processing and exchanges' own deposit checks can add delay. No mainnet launch date has been announced.

"I can just spin up a thousand builders, rotate them, offer very high bids, and not produce payloads," Ethereum consensus developer Potuz said on a core developer call. "Any teenager can do this."

Why It Matters

• Ethereum is scaling its base layer. ePBS and block-level access lists aim to fit far more activity into each block while keeping hardware requirements manageable.
• Testnets are where upgrades get stress-tested. The Sepolia Sybil warning shows why public tests matter, and why the shortened review window deserves attention.
• Solana is chasing near-instant settlement. Sub-second finality, if it holds up in production, could shorten waits for exchange deposits and merchant payments.
• Neither has a mainnet date. Both upgrades remain in testing, and timelines depend on what these test networks reveal.