Ethereum has scheduled the Glamsterdam upgrade on Sepolia for October 6.

Ethereum developers have scheduled the network’s next major upgrade, Glamsterdam, to activate on the Sepolia testnet on Oct. 6, giving node operators, client maintainers and application developers a dated target for testing the changes before any broader rollout. The Ethereum Foundation said Monday that Sepolia node operators must update both their execution-layer and consensus-layer clients before the activation.

Node Operators Must Update Clients Before Sepolia Activation

The activation date turns Glamsterdam from a roadmap item into a concrete testnet event. Sepolia is used to exercise protocol changes before they reach validator-focused or mainnet environments. The instruction to update both execution-layer and consensus-layer clients matters because Ethereum nodes run two coordinated parts: the execution layer processes transactions and state, while the consensus layer handles validator coordination and finality. If operators on Sepolia do not update both layers in time, they may fail to follow the new protocol rules or be unable to participate in the testnet transition.

For readers who run Ethereum nodes, the near-term task is straightforward: check client software, apply updates before Oct. 6, and monitor Sepolia behavior around the activation. For developers building on Ethereum, the testnet event is also a chance to see how applications respond to the new protocol rules in a lower-risk environment.

Enshrined Block Building and Access Lists Reshape Protocol Behavior

One of Glamsterdam’s changes is enshrined proposer-builder separation. The upgrade will move the handoff between specialized block builders and validators into Ethereum’s protocol, reducing reliance on outside middleware. In practice, this means a part of the block-production process that currently depends on external coordination may become a native protocol function. That can make the testnet upgrade a useful observation point for how Ethereum handles block construction, validator participation and the builder-to-proposer pipeline.

Glamsterdam will also introduce block-level access lists, which record the accounts and storage locations used during each block. This is a protocol-level record of which parts of the state are touched during block execution. The change is likely to matter most to client developers, protocol researchers and applications that need to understand or optimize data access patterns, rather than to casual users.

Gas Pricing Changes May Force Smart Contract Adjustments

The upgrade will also change gas pricing to better reflect the cost of creating and accessing data on Ethereum. Gas pricing is the mechanism used to charge for computational and storage resources on the network. If the model more closely mirrors the real cost of data creation and access, some contracts may need to adapt.

The Ethereum Foundation said contracts that rely on fixed gas stipends or hardcoded gas limits may require changes. That warning is relevant to developers who build applications that assume certain gas behavior, such as contracts that pass a fixed amount of gas to another call or that set strict limits on internal operations. Before Glamsterdam moves beyond Sepolia, developers can use the testnet to identify whether their contracts still behave as expected under the new pricing rules.

Hoodi and Mainnet Dates Remain Unset While Hegotá Points to 2027

Developers have not set dates for Glamsterdam’s rollout on the validator-focused testnet Hoodi or on mainnet. That leaves the Sepolia activation as the first scheduled public checkpoint for the upgrade, while later phases remain to be announced. For validators, the absence of a Hoodi date means the next major operational milestone after Sepolia is still open-ended.

The roadmap also extends beyond Glamsterdam. 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.

That framing suggests Glamsterdam and Hegotá are not just routine maintenance releases. Glamsterdam’s testnet date gives the ecosystem an immediate place to validate protocol changes, while the longer-term direction points to a deeper technical transition involving advanced proof systems, formal verification, consensus efficiency and post-quantum security.

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