Ethereum developers have scheduled the network's next major upgrade, Glamsterdam, to activate on the Sepolia testnet on Oct. 6, according to an announcement from the Ethereum Foundation. Sepolia node operators must update both their execution-layer and consensus-layer clients before the activation, the foundation said Monday — a dual-client requirement that follows from Ethereum's split architecture, in which separate software handles transaction execution and consensus.

The upgrade is set to bring proposer-builder separation, block-level access lists and a revised gas pricing model, although its mainnet activation date remains unset. The Oct. 6 activation gives node operators and application developers a public testnet run of those changes ahead of any mainnet activation.

What Glamsterdam changes

One of Glamsterdam's core features is enshrined proposer-builder separation. The change will move the handoff between specialized block builders and validators directly into Ethereum's protocol, reducing reliance on outside middleware.

The upgrade will also introduce block-level access lists, which record the accounts and storage locations used during each block. That extends an access-list mechanism Ethereum has offered at the individual transaction level since the 2021 Berlin upgrade, but applies it across entire blocks. In addition, gas pricing will be adjusted to better reflect the actual cost of creating and accessing data on Ethereum. Contracts that rely on fixed gas stipends or hardcoded gas limits may require changes to remain compatible, the foundation said, giving smart-contract teams a defined window on Sepolia to verify compatibility before a mainnet fork is scheduled.

Mainnet timing remains open

While the Sepolia activation date is now set, developers have not announced when Glamsterdam will roll out on Hoodi, the validator-focused testnet, or on Ethereum mainnet. In recent Ethereum hard forks, mainnet activation has typically followed successful runs across the public testnets, so a Hoodi date and the rollout of updated Sepolia clients are the near-term markers for tracking Glamsterdam's progress.

Hegotá on the horizon

Developers are targeting 2027 for Hegotá, the upgrade expected to follow Glamsterdam. Ethereum co-founder Vitalik Buterin said Sunday that Hegotá could be the network's last "normal" fork before development shifts toward recursive STARKs, automated formal verification, optimized consensus and quantum-safe cryptography. The sequence sketches a two-stage roadmap: Glamsterdam changing how blocks are proposed and priced, with Há pointing the protocol toward longer-horizon cryptographic research.

In related coverage, Ethereum institutional signals have backed Ethlabs' motion to reduce Ethereum block times.