Ethereum will activate the Glamsterdam upgrade on the Sepolia testnet on Oct. 6, targeting block production, state growth and execution limits while laying the groundwork for higher layer-1 capacity, the Ethereum Foundation said in a blog post.

The deployment combines the Gloas consensus-layer upgrade with the Amsterdam execution-layer upgrade. It represents the next major step in the network's L1 scaling roadmap following Fusaka. Activation dates for the validator-focused public testnet Hoodi and for mainnet remain undetermined, according to the Foundation.

Parithosh Jayanthi, a core developer at the Ethereum Foundation, told CoinDesk that the fork would likely be Ethereum's largest since the Merge. He said the upgrade could change key assumptions about how the network operates and set the stage for further scaling.

Glamsterdam follows years of engineering work aimed at making Ethereum's base layer faster without sacrificing decentralization. The upgrade addresses structural constraints that have become more visible as network usage has grown.

Higher transaction demand has exposed the limits of sequential execution, while reliance on specialized block builders has raised concerns around block-production centralization and maximal extractable value (MEV). At the same time, simply raising Ethereum's gas limit would accelerate state growth and increase the hardware burden on validators — a trade-off the upgrade is designed to manage rather than ignore.

Two headline features anchor the release. The first is enshrined proposer-builder separation, which moves proposer-builder interactions into the Ethereum consensus protocol itself, reducing dependence on external infrastructure and the centralization pressures it creates. The second is block-level access lists, which allow clients to process state reads and validation more efficiently, improving parallelism in execution.

Glamsterdam will also revise gas accounting and pricing so that fees better reflect the actual costs of execution and state growth — a change with direct operational consequences for validators, rollup operators and application developers who optimize around gas economics.

The operational stakes are significant. Enshrining proposer-builder separation alters the mechanics of block construction across the network, while block-level access lists change how execution clients schedule and validate transactions. Both shifts will require coordinated client software updates ahead of mainnet activation, and the Sepolia deployment serves as the first live test of that coordination at scale.

Over the longer term, the Ethereum roadmap points toward statelessness and Verkle trees — a structural change to how Ethereum stores state that would sharply reduce validator storage requirements — alongside stronger privacy capabilities and continued improvements to rollup data availability and interoperability.

The upgrade arrives amid a broader market rally, with ETH up 14% over the past two weeks alongside other risk assets. The Ethereum Foundation cautions, however, that rising Treasury yields are creating a tougher macro backdrop and could keep price gains volatile.

With Sepolia activation set for Oct. 6, attention now shifts to whether client teams and validators complete the necessary software rollouts on schedule, and to the Foundation's subsequent announcements of Hoodi and mainnet fork dates — the milestones that will determine when Glamsterdam's capacity and block-production changes reach production traffic.