Ethereum Schedules Glamsterdam Upgrade for Sepolia Testnet on October 6

The Ethereum Foundation has scheduled the activation of the Glamsterdam network upgrade on the Sepolia testnet for October 6, 2026 ¹. This milestone represents a major step forward in the network's Layer 1 scaling roadmap, following the previous Fusaka upgrade ¹. Glamsterdam integrates two distinct protocol updates: the Amsterdam execution layer upgrade and the Gloas consensus layer upgrade ¹.

By combining these two layers, the upgrade introduces structural changes to how the blockchain processes transactions and validates blocks ¹. At the time of writing, $ETH is trading at $2,728, up 1.7% over the past 24 hours, amid broader market stability. The transition on Sepolia will occur at epoch 353,024, slot 11,296,768, which is projected to take place at 13:53:36 UTC on October 6, 2026 ¹. Node operators must update both their execution and consensus layer clients before this activation to avoid being split from the network ¹.

Enshrined Proposer-Builder Separation and Block-Level Access Lists

The core architectural shift in Glamsterdam is the introduction of enshrined proposer-builder separation (ePBS) via EIP-7732 ¹. Currently, the division of labor between block proposers and block builders relies on external, trusted middleware ¹. EIP-7732 integrates this separation directly into Ethereum's consensus protocol ¹. Under this new design, a proposer commits to a builder's execution payload, and the builder subsequently reveals the payload data ¹.

The protocol itself manages the payment to the proposer, eliminating the need for third-party relayers ¹. Furthermore, ePBS separates consensus validation from execution validation ¹. This separation provides validators with additional time to verify execution payloads ¹. A newly established payload timeliness committee will attest to whether the builder revealed its payload and if the corresponding blob data was available on time ¹.

Complementing ePBS is EIP-7928, which introduces enforced block-level access lists (BALs) ¹. These lists record the specific accounts and storage locations accessed during a block, alongside post-transaction state changes ¹. By standardizing this data, BALs allow client software to read state from disk in parallel, validate transactions concurrently, and compute state roots with greater efficiency ¹. Together, ePBS and BALs establish a technical foundation designed to scale execution capacity while keeping block validation practical for standard node operators ¹.

Gas Accounting and State Growth Adjustments

Beyond structural validation changes, Glamsterdam implements significant adjustments to Ethereum's gas pricing model to better reflect the actual resource costs of execution and state growth ¹. EIP-8037 increases and separately meters the cost associated with creating new state, while EIP-8038 updates state-access costs ¹. Additional modifications target intrinsic transaction gas, calldata floor costs, access lists, and block gas accounting ¹.

These changes mean that application developers must thoroughly test their smart contracts and gas estimation algorithms against the new rules ¹. Contracts that rely on fixed gas stipends, hardcoded gas limits, or specific assumptions about remaining gas may fail or behave unexpectedly after the upgrade ¹. The Ethereum Foundation has advised developers to consult the Glamsterdam repricing impact guide to search for affected contracts and access testing guidance ¹.

Furthermore, client implementations introduce specific operational parameters ¹. For instance, the Prysm 7.2.0 client supports the Sepolia fork but defaults to a 60 million gas limit after activation ¹. Validators who wish to propose blocks with a 200 million gas limit must explicitly configure their software using version 2 proposer settings or the keymanager API, as the traditional command-line flag for suggested gas limits will have no effect after the Gloas consensus upgrade ¹.

Developer and Validator Improvements

Glamsterdam incorporates a wide array of developer-facing improvements and consensus-level refinements ¹. Among the scheduled changes is EIP-7708, which forces ETH transfers to emit a log, and EIP-7843, which introduces a slot-number opcode ¹. The upgrade also increases the maximum contract size via EIP-7954 and introduces a deterministic factory contract through EIP-7997 ¹. New stack-manipulation instructions are also added to the execution environment ¹.

On the consensus side, the upgrade introduces forward-compatible data structures via EIP-7688 ¹. It also implements EIP-8045, which excludes slashed validators from proposing blocks, and EIP-8061, which increases exit and consolidation churn ¹. These changes aim to improve the security and efficiency of the validator set ¹.

To ensure the security of these new specifications, the Ethereum Bug Bounty Program has been activated for all Glamsterdam specifications and EIPs ¹. Client implementations will become eligible for bounties as soon as their respective releases are confirmed and added to the official release tables ¹.

Implications for the Ethereum Roadmap

The Sepolia deployment serves as the critical testing ground for these highly complex protocol changes ¹. By moving ePBS and block-level access lists into a live testnet environment, core developers can monitor how different client implementations interact under real-world conditions ¹. This is particularly important given the diverse set of execution and consensus clients, including Grandine, Lighthouse, Lodestar, Nimbus, Prysm, Teku, Besu, Erigon, Geth, Nethermind, and Reth ¹.

If the Sepolia activation on October 6 is successful, it will pave the way for subsequent deployments on other testnets, such as Hoodi, before an eventual mainnet release date is decided ¹. For more context on the preparation for this upgrade, readers can refer to the Ethereum Foundation Sets Oct. 6 for Glamsterdam Upgrade on Sepolia announcement.

What to Watch

In the immediate term, node operators running Sepolia nodes must update both their execution and consensus layer clients to compatible versions before the October 6 deadline ¹. Stakers on Sepolia must also review their client-specific upgrade instructions to prepare for the new ePBS duties and any changes required for builder or validator tooling ¹.

For the broader Ethereum community, the key metrics to watch post-activation will be the stability of block production under the new ePBS rules, the efficiency of parallel state reading enabled by BALs, and the impact of the gas repricing on existing decentralized applications ¹. Mainnet users and ETH holders do not need to take any action, as a separate announcement will detail the mainnet activation schedule once client teams reach a consensus ¹.