This past week, a dedicated cohort of over 100 Ethereum core contributors journeyed to Longyearbyen, Svalbard, situated above the Arctic Circle, for the Soldægn Interop. This intensive, week-long event was meticulously designed to accelerate progress on the critical Glamsterdam network upgrade, a pivotal step in enhancing Ethereum’s scalability and efficiency. The gathering echoed the focused, single-track format previously employed for significant upgrades like Amphora, Edelweiss, and Nyota, emphasizing collaborative, multi-client development towards a specific set of objectives.
The Soldægn Interop’s primary objective was to solidify the groundwork for Glamsterdam, specifically aiming to "harden" its implementations and establish a clear target for a post-upgrade gas limit floor. By the conclusion of the week, the core developers achieved three significant milestones: an agreement on a post-Glamsterdam gas limit floor of 200 million, the stable operation of external builder integrations for Proposer-Builder Separation (ePBS), and the finalization of repricing numbers for Ethereum Improvement Proposal (EIP)-8037. Beyond these core achievements, substantial advancements were also made on future features, including Hegemone’s FOCIL (Fast Object Channel for Interoperable Layer) and native account abstraction, alongside discussions on a wide array of other crucial development topics.
The Strategic Choice of Svalbard: A Nexus of Isolation and Preservation
The selection of Longyearbyen, Svalbard, as the venue for Soldægn Interop was deliberate and multi-faceted. This remote archipelago offers a unique environment characterized by minimal external distractions, fostering an atmosphere conducive to deep, focused work. Crucially, Svalbard is one of the few locations globally where individuals can reside and work without visa requirements, facilitating the participation of a diverse international group of developers.
Beyond its logistical advantages, Svalbard holds symbolic significance for the blockchain community. It is home to the Global Seed Vault and the Arctic World Archive, two vital cold-storage facilities tunneled into the permafrost. These archives serve as humanity’s long-term repository for critical data, preserving backups of crops, cultural artifacts, and, notably, source code – including a snapshot of Ethereum’s code. This parallel between preserving humanity’s digital heritage and securing Ethereum’s future scalability underscores the profound nature of the work undertaken during the interop. Furthermore, the perpetual daylight during the Arctic summer, from late April to August, provided an extended operational window, mirroring Ethereum’s own commitment to 24/7 uptime, a characteristic celebrated by the core developers who maximized every hour of daylight for their coding sessions.
Harden Glamsterdam, Scale Ethereum: The Core Mandate
The overarching goal of the Soldægn Interop was to prepare the network for the Glamsterdam upgrade, a crucial step in Ethereum’s ongoing scaling roadmap. This involved not only refining existing implementations but also deriving a robust target for the gas limit floor, a fundamental parameter that dictates transaction throughput. Safely increasing the gas limit is a complex, multi-dimensional challenge that Glamsterdam is designed to address by optimizing several key areas: the mechanisms for block construction and proposal, the headroom available for client implementations under heavy load, and the scaling efficiency of state-creation costs in conjunction with increased throughput.
In practical terms, the week’s efforts culminated in a stable, multi-client Glamsterdam development network (devnet) running the latest iterations of ePBS, along with finalized specifications for repricing and block access lists. This comprehensive setup provided essential benchmarking data to support a credible proposal for an increased gas limit. The intense development process involved extensive periods of focused coding, often extending into the early morning hours, interspersed with critical breakout sessions dedicated to aligning on design decisions and discussing the long-term roadmap.
Supporting this intensive development were three Ethereum Foundation (EF) teams. EthPandaOps provided crucial infrastructure, including the ethIQ performance analysis tool and a panda MCP server to facilitate agentic workflows. The Protocol Support team established soldogn.xyz as the central hub for interop goals, schedules, and notes, serving as the single source of truth for all participants. The EF Digital Studio team documented the entire week, promising the release of the first-ever interop documentary, offering a unique insight into the collaborative spirit and technical rigor of these crucial development sprints.
ePBS: Restructuring Slots for Enhanced Throughput
A cornerstone of the Glamsterdam upgrade is the refinement of Proposer-Builder Separation (ePBS). This enhancement aims to optimize the relationship between block proposers and builders by introducing explicit deadlines for block construction, payload revelation, and attestations. By clearly delineating these time windows, ePBS increases the available time for execution, thereby creating more headroom for a higher gas limit.
The week commenced with an ambitious target: a four-layer execution (EL) and four-layer consensus (CL) Glamsterdam devnet operational by Monday evening. Initial testing revealed a number of issues, necessitating a revised target for Tuesday, when a 4×3 configuration successfully ran, allowing stress testing to commence. The subsequent days were dedicated to an intensive ePBS hardening cycle: stress testing, identifying edge cases, implementing fixes, and repeating the process.
A breakout session on Tuesday morning significantly streamlined the Builder API specification, clarifying validator registration, the bid/header/commitments flow, the trust model for builder payments, and circuit-breaker mechanisms. Mid-week debugging efforts focused on cross-client edge cases, particularly concerning the invalidation of beacon requests by execution requests. A new test suite identified discrepancies across all client implementations in this area. By Thursday morning, CL teams reported stable ePBS operations, while EL-side bid pathways were still undergoing debugging, with resolutions achieved through Thursday and into Friday. Two contentious points remain for the All-Core-Devs (ACD) discussions: whether a request signature should commit to the receiving builder, and how to ensure the resilience of a 1 ETH-staked-builder design against peer-to-peer Sybil-based liveness attacks. By Friday, nearly all clients were successfully running on glamsterdam-devnet-2, with the external builder pipeline tested end-to-end.
BAL Optimizations: Execution Layer Enhancements for Scalability
Complementing the consensus-layer advancements of ePBS, the execution layer (EL) enhancements for Glamsterdam primarily revolve around gas repricing and Block-Level Access Lists (BALs), as detailed in EIP-7928. BALs provide clients with upfront information about a block’s read and write sets, enabling crucial optimizations such as parallel execution, batched I/O operations, and parallel state-root computation. These improvements directly contribute to a client’s capacity to handle larger blocks efficiently.
The BAL track at Soldægn operated on separate devnets, distinct from the Glamsterdam ePBS chains, ensuring that optimization benchmarks were not conflated with consensus-layer stabilization efforts. Each optimization was implemented with its own feature flag, allowing for isolated comparative analysis rather than a bundled approach. The BAL benchmark dashboard and leaderboard, accessible at nerolation.github.io/bal-dashboard/, highlighted each client’s worst-case performance across the test suite. By focusing on improving the slowest execution paths, the development teams aimed to collectively raise the gas limit floor across all implementations, rather than solely benefiting the most performant ones.
Gas Repricings: Calibrating Costs for Higher Throughput
A critical component of the Glamsterdam upgrade involves gas repricing initiatives designed to align transaction costs more accurately with resource utilization at higher throughput levels. At the heart of these efforts is EIP-8037, which increases the gas cost for creating new state. This measure is vital to prevent an unbounded increase in state growth that could otherwise accompany a higher gas limit.
Heading into the Soldægn Interop, the EIP-8037 specification featured dynamic per-state-byte pricing tied to the block gas limit. This dynamic approach presented significant challenges for testing, leading to combinatorial complexity and making benchmarking nearly intractable. Early in the week, the development teams reached a consensus to move away from dynamic pricing in favor of a fixed cost_per_state_byte. Future repricing adjustments will be managed at fork boundaries rather than within a given fork.
The accounting model itself underwent a more iterative development process. An initial breakout session on Monday shifted state-gas accounting from mid-execution to the end of call frames. A follow-up session on Tuesday addressed account creation costs, code deposit costs, and CREATE transaction reverts. By Wednesday, discussions centered on edge cases related to reservoir refunding and refilling, prompting a reevaluation of the model. A breakout session on Thursday reverted the accounting to the opcode level, recognizing that the primary complexity resided within the reservoir model rather than the accounting computation itself. By Friday, the specification had stabilized on bal-devnet-6, with the BAL track delivering the finalized repricing numbers. This week-long process exemplifies the power of interop events, enabling the resolution of complex specification, implementation, testing, debugging, and design issues within hours rather than weeks, effectively compressing asynchronous progress into daily achievements.
The convergence of these three critical threads—ePBS, BAL optimizations, and EIP-8037 repricings—culminated in the week’s headline achievement: a credible 200 million gas limit floor for the post-Glamsterdam era. This substantial increase is made possible by ePBS structuring the slot to allocate more time for execution, BAL optimizations providing clients with the necessary throughput headroom within that structure, and EIP-8037 ensuring that the higher gas limit does not lead to unsustainable state growth.
Broader Glamsterdam Scope and Future Considerations
Beyond the core advancements in ePBS, BALs, and gas repricings, the Soldægn Interop also addressed a range of other important Glamsterdam-related topics. Several smaller EIPs were finalized. EIP-8061, which increases exit and consolidation churn, was successfully integrated into glamsterdam-devnet-1. EIP-8080, proposing exits via the consolidation queue, was ultimately declined for inclusion in this upgrade. EIP-8045, concerning the removal of slashed validator duties, was scoped down to only affect proposer duties within the look-ahead window. EIP-7688, focusing on SSZ stable containers, remains within the Glamsterdam scope but was held out of glamsterdam-devnet-1 to allow for further work on bounded gossip message sizes for attestations under progressive lists.
A significant architectural breakout session on Wednesday morning between EL and CL teams resulted in the decision to defer EIP-8237 out of Glamsterdam. This strategic move preserves optionality for a more advanced "top-up sync" architecture in a future fork. In its place, the teams agreed to draft an EIP that standardizes the sequencing of forkchoiceUpdated, newPayload, and getPayload calls, defines a snap-sync initiation handshake, and tightens consistency between the engine API surfaces.
Hardening implementations and improving testing frameworks were also central themes. A session on Thursday explored fork-choice compliance testing frameworks, the Diamond repository of reproducible CL edge-case scenarios, and a demonstration of PandaOps’s buildoor external-builder testing tool. The latter showcased the tool’s ability to handle a continuous stream of attack scenarios suggested by attendees in real-time.
Looking Beyond Glamsterdam: Hegemone and Future Forks
Several dedicated breakout sessions at Soldægn focused on the future, specifically Hegemone and subsequent network upgrades. A deliberately proposal-agnostic session on native Account Abstraction initiated discussions on the essential requirements and constraints for any future design. Key feature goals such as alternative signature schemes, aggregation, batching, recovery, gas sponsorship, flexible nonces, and keystore wallets were considered alongside critical constraints like public-mempool compatibility, statelessness, and Layer 2 Denial-of-Service resistance.
A breakout session on Thursday specifically addressed FOCIL, focusing on implementation updates. Early prototypes were already functional, with multi-client interop and a dedicated FOCIL devnet identified as immediate next steps. Two notable design decisions were made: disabling FOCIL during periods of two-epoch non-finality (mirroring proposer-boost circuit-breaker behavior) and adopting an index-based bookmark approach for compatibility with frame transactions and EIP-7702.
Further down the roadmap, a long-running ETH P2P track explored the potential for a QUIC-based replacement for libp2p, emphasizing privacy-by-default and slot-aware integration. Additionally, an erasure-coded broadcast prototype demonstrated significantly faster propagation (~6x) than GossipSub on 2.4 MB payloads. The CL track also revealed a strong consensus toward eventually deprecating consolidations entirely. This would involve designating a final fork that supports them, followed by a mandatory exit-then-redeposit process, offering a cleaner long-term solution to validator-set state growth.
Refining the All-Core-Devs Process
A significant session on Wednesday afternoon, led by ACDE co-leads Nixo and Ansgar, focused on gathering core contributor input regarding the All-Core-Devs (ACD) process. The discussion revisited the "headliner" construct, debated the merits of maintaining a "strawmap," and formalized the criteria for EIP Specification Finalization (SFI). The general sentiment favored retaining headliners but with greater flexibility regarding the rigidity of EIP-versus-theme alignment, accepting a "theme plus candidate EIP" model. The per-fork year assignments on the strawmap beyond 2026 were flagged as potentially over-canonicalized and likely to be softened. A new four-point SFI definition was proposed, with ACD Technical (ACDT) signaling readiness and ACD Execution (ACDE) and ACD Coordination (ACDC) retaining final decision-making authority. A new prioritization-ordering process, to be implemented after CFI decisions and reflected in a meta-EIP, will replace SFI’s previous role in driving devnet inclusion, commencing with the Hegemone upgrade.
In terms of call coordination, Alex Stokes announced a three-month sabbatical commencing the following week. Pari will assume ACDC moderation duties during this interim period, and Barnabas will cover ACDT responsibilities. The updated leadership structure sees Nixo and Ansgar chairing ACDE, Pari as interim ACDC moderator, and Mario, Barnabas, and Danceratopz rotating ACDT moderation roles.
Conclusion and Next Steps
The Soldægn Interop proved to be an exceptionally productive gathering, compressing months of asynchronous development into a single, intensive week. The core contributors successfully achieved their primary objectives, laying crucial groundwork for the Glamsterdam upgrade and setting a clear path towards a significantly more scalable Ethereum. The key takeaway is the agreement on a 200 million gas limit floor, a substantial increase enabled by the synergistic advancements in ePBS, BAL optimizations, and EIP-8037.
Moving forward, development teams will focus on translating the prototypes developed during the interop into production-ready code. The coming weeks will see intense effort dedicated to hardening client implementations against the new specifications, finalizing test coverage, and merging the code developed at Soldægn. Final decisions on critical values, such as the 200M gas limit target and specific repricing numbers, will be formally communicated and discussed publicly during AllCoreDevs calls, anticipated to be major topics in the immediate future.
The success of Soldægn Interop is a testament to the dedication and collaborative spirit of the Ethereum core development community. The unique, focused environment of Svalbard, combined with the relentless effort of the developers, has significantly propelled Ethereum’s scalability roadmap forward, bringing the network closer to realizing its full potential. The forthcoming documentary promises to offer a compelling narrative of this crucial event, highlighting the innovation and teamwork that define Ethereum’s evolution.
