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Ethereum Glamsterdam Upgrade
Glamsterdam is the next major hard fork of the Ethereum blockchain, positioned as the Execution Layer (EL) upgrade following Fusaka and, as of October 2026, still an upcoming upgrade expected on mainnet in Q4 2026, with the exact date not yet confirmed and no specific mainnet epoch or timestamp scheduled.[10] Ethereum core developers and commentators describe Glamsterdam as the most extensive protocol overhaul since The Merge, because it reorganizes how blocks are created and verified to advance the “Scale L1” and “Scale Blobs” roadmap goals.[17][10] A key milestone on this path was the Sepolia testnet fork on October 6, 2026, which activated and finalized successfully after a last‑minute client fix and did not itself set a mainnet activation time.[16][18][19][20] The name "Glamsterdam" combines "Gloas," a star, with "Amsterdam," a Devconnect host city.[1]
Technically, Glamsterdam centers on enshrined Proposer‑Builder Separation (ePBS), block‑level access lists (BALs), and extensive gas repricing that differentiates long‑term state growth from short‑term computation, while testing substantially higher gas limits—around 200 million per block—on Sepolia as part of public testnet validation.[16][18] These changes aim to scale the Layer 1 base chain and blob throughput for rollups, enabling higher parallelization and lower transaction costs while keeping bandwidth and hardware requirements sustainable for home node operators.[10]
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 expected on mainnet in Q4 2026, with the exact date not yet confirmed; this target is not a fixed or scheduled mainnet date, and as of October 2026 no specific mainnet epoch or timestamp has been set.[10][19] 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.[16][10] The Sepolia upgrade activated and finalized successfully on that schedule, serving as a major public rehearsal of Glamsterdam’s scope, but did not itself define Hoodi or mainnet activation dates.[19][20] In advance of this fork, node operators were required to update both their execution and consensus clients to Sepolia‑compatible releases.[16] 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.[11][12]
On September 17, 2026, the Ethereum Foundation announced that the Glamsterdam upgrade was 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.[16] The Sepolia fork occurred as planned, finalized successfully, and raised Sepolia’s target gas limit from roughly 60 million to around 200 million gas per block as a capacity stress test for Glamsterdam’s new mechanisms.[18][19][20] Activation times for the Hoodi testnet and the Ethereum mainnet remain to be determined and will be communicated separately, so the completed Sepolia rehearsal refines earlier, more generic plans but does not itself set a mainnet epoch or date.[16] 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 October 2026 no specific mainnet date or epoch has been confirmed and the target remains subject to change based on testnet outcomes.[10]
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.[12][3] Formal security audits and community bug bounties 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.[10][16] With Sepolia completed, developers describe the remaining Hoodi rehearsal and any follow‑up testing as among the last major milestones before a mainnet activation decision.[19]
Key Features
Glamsterdam is expected to introduce several significant improvements to the Ethereum network, with much of its scope defined under Meta‑EIP‑7773 but still subject to final inclusion based on testing results.[10] At a high level, the upgrade focuses on enshrined Proposer‑Builder Separation (ePBS), block‑level access lists (BALs), and extensive gas repricing and accounting changes that better distinguish long‑term state growth from short‑term computation.[16] Together, these changes are intended to increase Layer‑1 and blob throughput for rollups while keeping full node requirements within reach of non‑specialized hardware.[10]
Under Meta‑EIP‑7773, Glamsterdam’s Sepolia deployment tracks a set of EIPs scheduled for inclusion on that testnet, including ePBS (EIP‑7732), BALs (EIP‑7928), gas repricing for storage and hashing (such as EIP‑8037 and EIP‑8038), resource‑based intrinsic gas via EIP‑2780, ETH transfer logs (EIP‑7708), a deterministic factory predeploy (EIP‑7997), a SLOTNUM opcode and related execution changes, increased contract size limits, validator exit and churn tuning, exclusion of recently slashed proposers from block production, and supporting networking EIPs required to propagate BALs and ePBS data.[16][10] The announced scope may still evolve before mainnet activation, and some proposals, such as EIP‑7805 (FOCIL) or revisions to contract code size rules, are treated as “consider for inclusion” rather than guaranteed components of the Glamsterdam fork.[3][10]
Within this scope, EIP‑7732 (ePBS) remains the consensus‑layer headliner for Glamsterdam and is scheduled for inclusion in the upgrade but is not yet live on mainnet.[7][10] It formally separates block proposers and builders and moves builder commitments and payments into the protocol, lengthening the data propagation and validation window and enabling larger payloads and higher throughput, especially for blob data used by Layer‑2 rollups.[15][14] 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.[15][14] 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.
Glamsterdam’s execution‑layer changes, including BALs, revised gas accounting, and resource‑based intrinsic gas, are designed to encourage more efficient use of persistent state and to prepare Ethereum for higher parallelism and greater blob usage in subsequent roadmap phases.[16][10] 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] Longer‑term ideas such as Verkle trees under “The Verge” roadmap and proposals to shorten block times to 6 seconds are discussed in the broader Ethereum roadmap but are not scheduled components of the Glamsterdam hard fork as defined in EIP‑7773.[10][6]
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.[14][10] Devnet experiments and the Sepolia testnet fork, which raised Sepolia’s gas limit from around 60 million to about 200 million gas per block with BAL-enabled 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 testnet environments rather than guarantees for production networks.[11][18][19] The formal Sepolia schedule and its successful completion under bug bounty coverage signal that Glamsterdam has moved from design into full public testing, but successful Hoodi rehearsals and any follow‑up tests remain prerequisites before any mainnet date is confirmed.[16]
At the same time, several risks and open questions remain as of October 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 completed Sepolia fork and the upcoming Hoodi tests.[13] Client teams also face tight timelines between releasing stable Glamsterdam-ready versions and activating them on each testnet, increasing the importance of coordinated testing and rollback plans.[12] 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.[10]
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]
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