The Ethereum Foundation has scheduled the Glamsterdam upgrade for the Sepolia testnet on October 6, 2026, at 13:53:36 UTC. The upgrade will combine the Amsterdam execution-layer changes with the Gloas consensus-layer changes and is designed to improve Ethereum’s Layer 1 scaling.
The Foundation said Glamsterdam will introduce major changes including enshrined proposer-builder separation (ePBS) and block-level access lists (BALs), while also changing gas accounting. The announcement applies only to Sepolia; Hoodi and Ethereum mainnet dates remain undecided.
The activation is scheduled for epoch 353,024 and slot 11,296,768. The Ethereum Foundation described the announcement as the first formal schedule for Glamsterdam on a network, following months of work on the upgrade.
Glamsterdam is the next major step after the Fusaka upgrade. Its name combines Amsterdam, the execution-layer upgrade, and Gloas, the corresponding consensus-layer upgrade. The broader aim is to make Ethereum process and validate transactions more efficiently while preparing the network for higher throughput.
Glamsterdam is coming, and it is bringing blocks built without trusted relays (and a lot more)!
The Sepolia testnet upgrade has been scheduled for 6 October of this year. Hoodi and mainnet dates will be announced separately. Activation table, client releases, and info on the bug…
— stokes (@ralexstokes) September 28, 2026
One of the most important changes is EIP-7732, which introduces enshrined proposer-builder separation. Under this system, the proposer includes a builder’s commitment to an execution payload, while the builder reveals the payload later. A payload timeliness committee will check whether the payload and related blob data were delivered on time. Separating consensus validation from execution validation should give validators more time to perform their checks.
Another major change is EIP-7928, or block-level access lists. These lists will record the accounts and storage locations accessed during a block, along with relevant state changes. This could allow clients to read state from disk and validate transactions in parallel instead of relying as heavily on sequential processing.
Glamsterdam also changes Ethereum’s gas accounting. EIP-8037 will increase and separately measure the cost of creating state, while EIP-8038 updates the pricing of state access. Other changes affect transaction gas, calldata, access lists and block gas accounting.
The changes are particularly relevant for developers. The Foundation has warned that contracts relying on fixed gas stipends, hardcoded gas limits or assumptions about how much gas remains available could behave differently after the upgrade. Developers are therefore expected to test their applications on Sepolia.
For node operators, the October 6 date is important. Sepolia operators will need to update both their execution-layer and consensus-layer clients before the scheduled activation. The Foundation has listed several supported client versions, including Besu 26.9.0, Erigon 3.7.0, go-ethereum 1.17.6, Nethermind 2.0.0 and Reth 2.7.0 on the execution side. Listed consensus clients include Lodestar 1.49.0, Prysm 7.2.0 and Teku 26.9.1.
Source: ethereum.org
The client list is still incomplete, with some entries yet to be added. The Foundation has advised operators to use only versions whose release notes specifically confirm Glamsterdam support on Sepolia.
For ordinary ETH holders and Ethereum mainnet users, there is currently nothing to do. The October 6 activation applies only to Sepolia. Separate announcements will be needed before Hoodi or mainnet activation dates are confirmed.
The scheduled Sepolia fork gives developers and infrastructure providers an important testing window before Glamsterdam eventually reaches the main Ethereum network. With the mainnet date still open, the focus now shifts to testing whether the upgrade’s proposed scaling and validation improvements work as intended under real testnet conditions.
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