Ethereum Glamsterdam Upgrade

Glamsterdam is an upcoming major hard fork of the Ethereum blockchain, designed to enhance its scalability, security, and sustainability. It is the Execution Layer (EL) network upgrade that follows the Fusaka upgrade and is targeted for mainnet activation in Q4 2026, although no specific mainnet date or epoch has been set. As of September 2026, Glamsterdam has progressed through multiple private developer test networks and is preparing for a public Sepolia testnet fork. The name "Glamsterdam" is derived from combining the star Gloas with Amsterdam, the city where a recent Devconnect event took place.^[1][11][12]

Overview

Glamsterdam represents a crucial phase in Ethereum's ongoing evolution, aiming to address persistent challenges such as network scalability and high transaction fees. Planned as the successor to the Fusaka upgrade, it is targeted for a Q4 2026 mainnet activation, with exact timing to be finalized after public testnet validation.^[11][5] The Ethereum Foundation has reorganized its research and development division into "Protocol," a leaner and more focused entity led by veterans like Tim Beiko and Ansgar Dietrichs. This reorganization prioritizes scaling the Layer 1 (L1), expanding blobspace, and improving user experience (UX), mandates that directly align with the expected priorities of Glamsterdam.^[2]

The development approach for Glamsterdam emphasizes stability and thorough testing, reflecting the iterative nature of blockchain development. By September 2026, the upgrade had passed through several dedicated private devnets and, under Meta‑EIP‑7773, the Sepolia testnet fork was assigned a fixed activation at epoch 353,024, slot 11,296,768 (October 6, 2026, 13:53:36 UTC), while activation parameters for the Hoodi testnet and mainnet remained unscheduled.^[17][11] In advance of this fork, node operators are required to update both their execution and consensus clients to Sepolia‑compatible releases.^[17] This commitment to staged testing is intended to ensure that new features are robust and well-integrated into the network's broader roadmap. The successful implementation of Glamsterdam is expected to significantly impact the entire Ethereum ecosystem, benefiting investors through enhanced network efficiency, developers through new functionalities and tools, and users through a more stable, secure, and cost-effective experience.^[2][3]

Naming Convention

Ethereum network upgrades traditionally derive their names from various sources, often combining a star name for the Consensus Layer (CL) upgrade with a city name for the Execution Layer (EL) upgrade. Historically, Devcon cities were used for naming upgrades. However, with Devcon becoming a biennial event, the use of Devconnect city names, such as Amsterdam, has been adopted for annual upgrades. For Glamsterdam, the name combines "Gloas," a G-star, with "Amsterdam," the city that hosted a recent Devconnect event. This naming convention is part of a Meta Ethereum Improvement Proposal (EIP-7773: Hardfork Meta - Amsterdam).^[1]

Development Roadmap

The Glamsterdam upgrade is positioned as the successor to the Fusaka upgrade, which is tentatively scheduled for mainnet deployment in early November 2025. Ethereum core developers have outlined a detailed roadmap for Glamsterdam, encompassing several critical phases from feature selection to mainnet activation. This structured approach aims to ensure a smooth and secure transition for the network.^[4][5]

Headliner Selection Phase

The initial phase involved the selection of "headliner" features to define Glamsterdam's primary focus. During the All Core Developers Consensus Call #162, Ethereum core developers officially selected EIP-7732, also known as enshrined Proposer-Builder Separation (ePBS), as the consensus layer headliner for the upgrade. This decision finalized the thematic direction of the upgrade, prioritizing protocol-level decentralization and censorship resistance over other candidates.^[4][7]

Proposal Deadline and Specification Freeze

To prevent scope creep and ensure timely progress, a strict deadline was set for finalizing headliner choices and submitting regular EIPs. This cut-off, set for August 21, 2025, allowed developers to merge, audit, and document all included EIPs before the network enters the rigorous testing phase. This disciplined approach is crucial for managing the complexity of a major blockchain upgrade. However, some developers have raised concerns that the intense focus on planning for Glamsterdam, which is not expected until 2026, might be diverting attention and resources from the upcoming Fusaka upgrade, potentially putting its Q4 2025 timeline at risk.^[4][8]

Testing and Audit Windows

The rollout process for Glamsterdam begins with the creation of dedicated client release branches that track the frozen specifications, followed by a sequence of private and public testnets. By September 2026, Ethereum client teams had iterated through multiple private devnets, culminating in a full dress rehearsal on Devnet-11 designed to exercise enshrined Proposer-Builder Separation (ePBS), block-level parallel execution, and state-cost repricing under stressed conditions.^[12][13]

On September 17, 2026, the Ethereum Foundation announced that the Glamsterdam upgrade is scheduled to activate on the Sepolia testnet at epoch 353,024, slot 11,296,768, corresponding to October 6, 2026, 13:53:36 UTC, as specified in Meta‑EIP‑7773.^[17] The same announcement stated that activation times for the Hoodi testnet and the Ethereum mainnet remain to be determined and will be communicated separately, so the Sepolia scheduling updates earlier, more generic plans but does not itself set a mainnet epoch or date.^[17] These public testnets are vital for identifying interoperability issues under realistic network conditions and for broader community participation, allowing dApp developers, node operators, and researchers to test their applications and infrastructure against the new changes. Ethereum.org and roadmap updates describe Glamsterdam as targeting a Q4 2026 mainnet activation, but as of September 2026 no specific mainnet date or epoch has been confirmed.^[11]

Developers have indicated a willingness to adjust this timeline in response to bugs, finality issues, or client divergences uncovered on devnets and testnets, mirroring the cautious approach taken with the Pectra and Fusaka upgrades.^[13][3] Formal security audits and community bug bounties are expected to focus on the period between public testnet activation and final mainnet scheduling, with the Ethereum Foundation announcement confirming bug bounty coverage around the Sepolia fork.^[11][17]

Key Features

Glamsterdam is expected to introduce several significant improvements to the Ethereum network, with much of its scope defined by mid‑2026 but still subject to final inclusion based on testing results. A primary focus of the upgrade is the transition from Merkle trees to Verkle trees, which is intended to enhance how Ethereum stores data and validates transactions, paving the way for greater scalability and efficiency. Verkle trees are a critical component of Ethereum's "The Verge" phase, which aims to make state access more efficient and enable stateless block verification.^[11]

Under Meta‑EIP‑7773, Glamsterdam’s Sepolia deployment tracks a set of EIPs scheduled for inclusion on that testnet, including enshrined proposer–builder separation (EIP‑7732), block-level access lists (EIP‑7928), pricing and state‑growth changes (EIP‑8037 and EIP‑8038), validator churn improvements (for example, EIP‑8061), and related execution

• and consensus-layer proposals.^[17] The announcement also notes that this scope may still change before mainnet activation and that activation parameters for the Hoodi testnet and mainnet are not yet finalized.^[17]

Other EIPs and features that are scheduled for inclusion or considered within the Glamsterdam scope include:

• EIP-7702 (Set EOA account code for one transaction) – Expected to give externally owned accounts a temporary code slot for a single transaction, enabling more flexible wallet designs while preserving the existing account model.^[10]
• EIP-7928 (Block-Level Access Lists, BALs) – A major execution-layer feature that lets block proposers publish block-level state access declarations, allowing clients to prefetch and schedule work more safely for parallel execution within a block.^[13][15]
• State-cost and gas repricing (for example, EIP‑8037 and EIP‑8038) – A set of proposals under the Glamsterdam umbrella that aim to limit long‑term state growth and rebalance gas costs for storage and hashing, with exact parameter choices and the final EIP set still subject to confirmation after testnet evaluation.^[13][11]
• Networking and execution support for BALs (such as EIP‑8159) – Expected changes to execution-layer gossip and validation rules so that block-level access lists can be propagated, verified, and used by clients without introducing unsafe assumptions or excessive complexity.^[13]
• Validator churn and exit scaling (for example, EIP‑8061) – Proposed adjustments so that validator entry, exit, and consolidation capacity scales more directly with total ETH staked, improving responsiveness of the validator set without compromising safety thresholds.^[13]
• EIP-7932 (Add BLOBBASEFEE opcode)
• EIP-7938 (BLOBHASH precompile)
• EIP-7940 (SSZ Withdrawal Root)
• EIP-7941 (SSZ Receipts Root)
• EIP-7942 (SSZ Transactions Root)
• EIP-7732 (ePBS - enshrined Proposer-Builder Separation): Selected as the consensus-layer headliner for Glamsterdam, this EIP is scheduled for inclusion in the upgrade but is not yet live on mainnet.^[7][11] It formally separates block proposers and builders and moves builder commitments and payments into the protocol, expanding the data propagation and validation window from roughly 2 seconds to around 9 seconds and enabling larger payloads and higher throughput, especially for blob data used by Layer‑2 rollups.^[16][15] ePBS introduces mechanisms such as a Payload Timeliness Committee (PTC) and dual-deadline attestation logic to enforce timely block delivery and strengthen liveness guarantees, while reducing reliance on external MEV relays and other centralized intermediaries in the block-building market.^[16][15] A key challenge this EIP addresses is the "free option problem," where builders can submit a block commitment but choose not to reveal the full block if market conditions become unfavorable, harming network liveness.
• EIP-7805 (FOCIL - Fork-Choice Enforced Inclusion Lists): Marked as 'Consider for Inclusion' (CFI) for the Glamsterdam upgrade, FOCIL is designed to introduce stronger user experience (UX) guarantees and enhance censorship resistance within the network.^[7]
• Gas optimizations and protocol-level efficiency: Glamsterdam is expected to focus on making Ethereum faster and cheaper to use, particularly for complex applications like Layer‑2 rollups and zero-knowledge (ZK) technology, through a combination of execution parallelism, blobspace expansion, and revised gas accounting.^[11][15]
• EIP-7907 (Contract Code Size Limits): Although deferred from the Fusaka upgrade to prioritize stability, a revised version of EIP-7907, which addresses contract code size limits and introduces gas metering changes, remains under consideration for future implementation in Glamsterdam or subsequent upgrades, highlighting developers' preference for extensive testing before deployment.^[3]
• Reduced Block Time: Ethereum core developer Barnabé Monnot has proposed reducing the block time from the current 12 seconds to 6 seconds. If eventually approved for a future hard fork, this change could significantly improve user experience and enhance the efficiency of decentralized finance (DeFi) applications, but by 2026 it was being discussed as a possible long‑term direction rather than a feature firmly scheduled for Glamsterdam.^[1][2][6]

Cryptographic approaches to mitigating the ePBS free option problem, such as threshold encryption and silent threshold encryption, continue to be explored by researchers and projects like Shutter, but these mechanisms are not part of the core Glamsterdam fork and remain separate research directions that could influence later upgrades.^[9]

Impact and Challenges

Glamsterdam is framed by many core developers and commentators as the most significant protocol-level restructuring since The Merge, because it combines enshrined Proposer-Builder Separation with block-level parallel execution via BALs and extensive gas and state-cost repricing.^[15][11] Devnet experiments targeting a ~200 million gas limit with BAL-enabled parallel execution suggest that, if similar conditions hold on mainnet, average transaction fees for many common operations could fall by roughly 70–80%, though these figures are projections from modeling and test environments rather than guarantees for production networks.^[12][15] The formal Sepolia schedule and associated bug bounty coverage signal that Glamsterdam has moved from design into full public testing, but successful Sepolia and later Hoodi rehearsals remain prerequisites before any mainnet date is confirmed.^[17]

At the same time, several risks and open questions remain as of September 2026. Researchers have highlighted potential builder-abuse vectors for ePBS on public testnets, including strategies that could exploit the longer timing window or attempt to game payload selection, and these behaviors are a focus of the upcoming Sepolia and Hoodi forks.^[14] Client teams also face tight timelines between releasing stable Glamsterdam-ready versions and activating them on Sepolia, increasing the importance of coordinated testing and rollback plans.^[13] More broadly, the absence of a fixed mainnet date despite the Q4 2026 target underlines developers’ willingness to delay activation if devnet or testnet results reveal unresolved issues.^[11]

For investors, successful upgrades can enhance network efficiency and utility, potentially strengthening the long-term value proposition of Ethereum (ETH), while setbacks or delays may briefly increase uncertainty but can also signal a preference for safety over speed. For developers, Glamsterdam’s new EIPs—including ePBS, BALs, and revised gas accounting—introduce new functionalities, tools, and optimizations that may require substantial code changes but open the door to more sophisticated, efficient, and secure decentralized applications. For users, the upgrade’s net effect is expected to be a more stable, secure, and potentially faster and cheaper network experience over time, with any short-term complexity during the transition balanced against long-term capacity gains.

Despite the anticipated benefits, coordinating a hard fork for a network as large and complex as Ethereum presents significant challenges. Thousands of contributors must ensure backward compatibility, maintain client diversity, and rigorously test every change. The decision to defer EIP-7907 from Fusaka and to treat elements of Glamsterdam’s scope as conditional on testnet results underscores this complexity and demonstrates developers' commitment to caution and thoroughness over rushed implementation. Another key challenge is ensuring that as Ethereum scales, it preserves its core ethos, including censorship resistance and privacy, which some developers have raised concerns about if not explicitly reaffirmed as strategic goals.

Tim Beiko, a project coordinator, stated, "Protocol is now a more united and leaner organization with more focused teams…ensuring the EF’s resources are allocated toward maximal impact." He also noted, "Ethereum stands at the edge of major breakthroughs…This may be our best shot at deploying not only our technology, but our values, at planetary scale." Ansgar Dietrichs added, "For Glamsterdam…we will have to find some ways to continue the blob scaling…there might be some EL-side scaling opportunities too." These statements highlight the strategic importance and ambitious goals of the Glamsterdam upgrade.^[2][3]