The Ethereum network is poised for a significant evolution with the upcoming Glamsterdam upgrade, a pivotal event scheduled to activate on the Sepolia testnet on October 6, 2026. Building upon the foundational improvements introduced by the Fusaka upgrade, Glamsterdam represents a substantial advancement in Ethereum’s Layer 1 scaling roadmap. Its core innovations—enshrined proposer-builder separation (ePBS), block-level access lists (BALs), and refined gas pricing mechanisms—are meticulously designed to enhance transaction throughput, optimize resource utilization, and bolster the network’s overall efficiency and robustness.
The Glamsterdam network upgrade is slated to go live on the Sepolia testnet at epoch 353,024, slot 11,296,768, which corresponds to October 6, 2026, at 13:53:36 UTC. This carefully chosen activation point allows developers, node operators, and the broader ecosystem to rigorously test and prepare for the mainnet deployment. While the specific activation dates for the Hoodi and mainnet environments are yet to be determined, the Sepolia testnet serves as a crucial proving ground. Node operators are strongly advised to update both their execution layer and consensus layer clients to compatible versions well in advance of the Sepolia activation to ensure seamless integration and prevent network disruption.
Glamsterdam: A Harmonious Fusion of Amsterdam and Gloas
The Glamsterdam upgrade is a synergistic combination of the Amsterdam execution layer upgrade and the Gloas consensus layer upgrade. This integration aims to deliver a more performant and scalable Ethereum by introducing two headline features: enshrined proposer-builder separation (ePBS) and block-level access lists (BALs). These innovations fundamentally alter how blocks are produced and validated, paving the way for increased L1 throughput.
Enshrined Proposer-Builder Separation (ePBS): Revolutionizing Block Production
At the heart of Glamsterdam’s scaling strategy is enshrined proposer-builder separation (ePBS), formalized by EIP-7732. This crucial development integrates the separation of block proposers and builders directly into Ethereum’s consensus protocol. Previously, a complex ecosystem of middleware facilitated communication and payment between proposers and builders. ePBS streamlines this process by allowing a proposer to include a builder’s commitment to an execution payload within the consensus layer. Subsequently, the builder reveals this payload, and the protocol itself handles the payment to the proposer. This direct integration significantly reduces reliance on trusted third-party intermediaries, enhancing security and decentralization.
Beyond simplifying the proposer-builder dynamic, ePBS introduces a critical separation between consensus validation and execution validation. This architectural shift provides validators with more time to thoroughly validate execution payloads. A dedicated "payload timeliness committee" will now attest to whether a builder has revealed its payload and if the corresponding blob data was made available on time. This enhanced validation process is vital for maintaining network integrity and performance. Consequently, validator operators and teams managing builder infrastructure must familiarize themselves with these new responsibilities and interface changes in preparation for the upgrade.
Block-Level Access Lists (BALs): Enhancing Validation Efficiency
Complementing ePBS, block-level access lists (BALs), introduced by EIP-7928, represent another significant stride towards scalability. BALs enforce the recording of all accounts and storage locations accessed during the execution of a block, along with any post-transaction state changes. This detailed ledgering provides a more granular understanding of block execution.
The implications of BALs are far-reaching. They empower clients to read state from disk in parallel, thereby accelerating transaction validation. This parallelization capability is crucial for handling the increased transaction volume that Ethereum aims to support. Furthermore, BALs facilitate parallel transaction validation and enable more efficient computation of state roots. The combined impact of ePBS and BALs creates a robust foundation for scaling Ethereum’s execution capacity while ensuring that block validation remains practical and accessible for node operators, a key tenet of Ethereum’s decentralized ethos.
Gas Pricing and State Growth: A More Accurate Resource Model
Glamsterdam also introduces significant adjustments to gas accounting, aiming to more accurately reflect the true cost of resource utilization on the network. EIP-8037 revises and increases the cost associated with creating new state, ensuring that state growth is adequately compensated. Simultaneously, EIP-8038 modifies state-access costs, aligning them more closely with the computational and storage resources required.
These repricing mechanisms extend to intrinsic transaction gas, calldata, access lists, and the overall block gas accounting. The goal is to create a more economically sound environment where resource consumption directly correlates with the gas fees incurred. Application developers are strongly encouraged to test their smart contracts and gas estimation mechanisms against these new rules. Contracts that rely on fixed gas stipends, hardcoded gas limits, or assumptions about remaining gas may require modifications to function correctly post-upgrade. A comprehensive "Glamsterdam Repricing Impact Guide" has been made available to assist developers in identifying affected contracts and conducting thorough testing.
Developer and Validator Enhancements: Broadening the Ecosystem’s Capabilities
Beyond the core scaling features, Glamsterdam incorporates a suite of improvements designed to benefit developers and validators alike. These include the introduction of ETH transfer logs for enhanced transaction tracing, a slot-number opcode for more precise block timing information, an increased maximum contract size to accommodate more complex applications, and a deterministic factory contract for predictable contract deployment. New stack-manipulation instructions are also included to offer developers greater flexibility in smart contract development.
On the consensus layer front, Glamsterdam introduces forward-compatible data structures, ensuring a smoother transition for future upgrades. It also implements a crucial change to exclude slashed validators from participating in block proposal, thereby strengthening network security. Additionally, the upgrade increases exit and consolidation churn, improving the efficiency of validator management and network participation.
The complete list of scheduled Ethereum Improvement Proposals (EIPs) for Glamsterdam, tracked by EIP-7773, includes a comprehensive set of technical specifications designed to enhance the network’s capabilities. Supporting networking and informational EIPs are also integrated to ensure broad ecosystem compatibility and smooth adoption.
Security and Bug Bounty Program
With the introduction of significant protocol changes, the Ethereum Bug Bounty Program has been activated for Glamsterdam specifications and associated EIPs. Client implementations become eligible for the program as soon as their releases are officially listed as supporting the Sepolia activation. This initiative underscores Ethereum’s commitment to security and incentivizes the community to identify and report potential vulnerabilities, further fortifying the network. Participants are encouraged to review the program’s details, including reward multipliers and reporting requirements, to contribute to the network’s safety.
Activation Schedule and Client Releases
The agreed-upon deployment schedule for Glamsterdam mandates explicit opt-in from node operators. Client developers have meticulously coordinated the protocol changes, and validators and non-staking nodes are responsible for updating their software. A node that does not support the new rules will be unable to follow the upgraded network after activation, highlighting the critical importance of timely updates.
The activation on the Sepolia testnet is confirmed for October 6, 2026, at 13:53:36 UTC. This date marks a significant milestone, allowing for extensive testing before any mainnet deployment. Compatible client releases for Sepolia are being made available and will be continuously updated in dedicated tables. It is imperative for all node operators, especially validators, to consult these release tables and ensure they are using versions that explicitly confirm support for the Glamsterdam activation on Sepolia. For validators, this means updating both their consensus layer beacon node and validator client.
For those operating nodes on the Sepolia testnet, updating both execution and consensus layer clients is paramount. The client release tables provide a centralized resource for tracking compatible versions. Operators using external block-building infrastructure are also urged to review the specific upgrade instructions provided by their respective tooling providers.
Developer and Tooling Implications
Application and tooling developers are strongly advised to engage with the EIPs scheduled for Glamsterdam. Post-activation testing on Sepolia is crucial to identify any impacts on their projects. Developers should pay close attention to changes in gas accounting, log formats, new opcodes, and client interfaces. The repricing impact guide offers specific guidance for identifying contracts that may be sensitive to fixed gas assumptions and provides strategies for updating gas estimation mechanisms.
The naming convention for Ethereum network upgrades—execution layer upgrades named after Devcon or Devconnect host cities and consensus layer upgrades after star names—explains the origin of "Glamsterdam." It signifies the combination of the Gloas consensus layer upgrade and the Amsterdam execution layer upgrade, referencing Amsterdam, the host city of Devconnect in 2022. This naming practice reflects the collaborative and community-driven nature of Ethereum’s development.
In conclusion, the Glamsterdam upgrade represents a significant leap forward for Ethereum, addressing critical scaling challenges and enhancing network efficiency. By integrating advanced features like ePBS and BALs, and refining gas pricing, Ethereum is moving closer to its vision of a highly scalable, robust, and decentralized future. The successful activation on Sepolia will pave the way for future mainnet upgrades, further solidifying Ethereum’s position as a leading platform for decentralized applications and innovation.
