This past week, over 100 Ethereum core contributors convened in Longyearbyen, Svalbard, situated just over 78 degrees north of the Arctic Circle, for Soldøgn Interop. This intensive, week-long gathering was dedicated to the crucial task of refining and solidifying the upcoming Glamsterdam network upgrade, a pivotal step in scaling Ethereum’s capacity and efficiency. The event echoed the collaborative spirit of previous interop sessions, drawing inspiration from the successful formats of Amphora, Edelweiss, and Nyota, all designed to foster focused, multi-client progress on specific upgrade objectives.
The choice of Longyearbyen, Svalbard, as the venue was deliberate and imbued with symbolic significance. As one of the few locations globally where individuals can reside and work irrespective of nationality or visa requirements, it provided a unique and neutral ground for international collaboration. Furthermore, Svalbard’s association with long-term preservation, through the Global Seed Vault and the Arctic World Archive, resonated with Ethereum’s mission of building a robust and enduring decentralized future. The perpetual daylight during this period of the year, mirroring Ethereum’s own 24/7 uptime, served as a constant reminder of the project’s commitment to uninterrupted service and continuous development. This unique setting, far removed from typical urban conference venues, fostered an environment of deep concentration and collaborative problem-solving, enabling developers to work intensely under the midnight sun.
Soldøgn Interop built upon the foundational work laid during the previous year’s Berlinterop, but strategically returned to a single-track, highly focused format. This approach prioritizes deep dives into specific technical challenges, allowing for rapid iteration and consensus-building among diverse client teams. The primary objective for the week was to "harden Glamsterdam," ensuring its stability and preparing it for a significant increase in network throughput.
By the conclusion of the week on Friday, the participants had achieved three major milestones. Firstly, they established a consensus on a post-Glamsterdam gas limit floor of 200 million gas. This represents a substantial increase from current levels and is a critical enabler for enhanced network capacity. Secondly, stable implementations of proposer-builder separation (ePBS) were demonstrated, operating successfully with external builders, a key component for optimizing block production. Finally, the repricing numbers for EIP-8037, which addresses state creation costs, were finalized. Beyond these core achievements, considerable progress was also made on forward-looking features for the Hegotá upgrade, including advancements in Fully On-Chain Identity (FOCIL) and native account abstraction.
Harden Glamsterdam, Scale Ethereum
The overarching goal of the Soldøgn Interop was to solidify the Glamsterdam upgrade’s implementations and establish a clear target for a higher gas limit floor. The challenge of safely increasing the gas limit is multifaceted, addressing block construction mechanisms, client implementation headroom under load, and the scaling of state-creation costs in tandem with transaction throughput.
The practical outcome of the week was the operation of a stable multi-client Glamsterdam development network (devnet) running the latest ePBS specifications, along with finalized Block-Level Access Lists (BALs) and repricing strategies. Crucially, extensive benchmarking data was collected, providing a solid foundation for proposing and justifying the increased gas limit.
Much of the week was characterized by intense coding sessions, often extending into the early morning hours. These were interspersed with focused breakout sessions designed to align on critical design decisions and discuss long-term roadmap items. The collaborative synergy was amplified by the presence of infrastructure teams, including EthPandaOps, who provided the ethIQ performance monitoring tool and a dedicated Panda MCP server to support agentic workflows. The Protocol Support team established soldogn.xyz as the central hub for interop goals, schedules, and meeting notes, ensuring seamless information dissemination. The EF Digital Studio team documented the entire event, promising a forthcoming documentary that will offer a unique perspective on this significant development sprint.
ePBS: Enhancing Block Construction and Throughput
The implementation of ePBS (proposer-builder separation) represents a fundamental shift in how Ethereum blocks are constructed and validated. By introducing explicit deadlines for block construction, payload reveal, and attestations, ePBS fundamentally restructures the slot timeline. This provides the execution layer with significantly more time to finalize block payloads, thereby creating the necessary headroom to safely increase the gas limit.
The week commenced with an ambitious target: a four-Execution Layer (EL) to four-Consensus Layer (CL) Glamsterdam devnet by Monday evening. Initial attempts, as is often the case in such complex development sprints, surfaced a number of issues, prompting a shift in the target to Tuesday. By Tuesday, a 4×3 configuration was running stably enough to initiate rigorous stress testing.
The subsequent days evolved into a continuous ePBS hardening cycle: stress test, identify edge cases, implement fixes, and repeat. A breakout session on Tuesday morning significantly streamlined the Builder API specification, clarifying validator registration processes, the bid/header/commitments flow, the trust model for builder payments, and the implementation of circuit-breaker mechanisms. Mid-week debugging efforts zeroed in on cross-client edge cases, particularly concerning the invalidation of beacon requests by execution layer requests. A newly developed test suite uncovered a critical gap across all client implementations, which was subsequently addressed. By Thursday morning, CL teams reported stable ePBS operations, while EL-side bid pathways were still undergoing debugging. These EL issues were resolved through Thursday and into Friday. Two contentious points remained for the AllCoreDevs (ACD) discussions: whether a request signature should explicitly 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 functioning cohesively on glamsterdam-devnet-2, with the external builder pipeline tested end-to-end.
BAL Optimizations: The Execution Layer Counterpart
While ePBS addresses the consensus layer’s role in scaling, the execution layer’s contribution is equally vital, primarily through gas repricings and Block-Level Access Lists (BALs). BALs provide clients with upfront information about a block’s read and write sets. This crucial data enables parallel execution, batched I/O operations, and parallel state-root computation, all of which are instrumental in determining the maximum block size that clients can comfortably process.
The BAL track at Soldøgn operated on separate devnets, distinct from the Glamsterdam ePBS chains. This separation ensured that optimization benchmarks were not conflated with the challenges of stabilizing the consensus layer. Each optimization was implemented behind its own feature flag, allowing for isolated comparisons rather than evaluating them as a monolithic bundle. The BAL benchmark dashboard and leaderboard provided real-time visibility into each client’s worst-case performance across the test suite. By prioritizing the optimization of the slowest execution paths, the development teams aimed to elevate the gas limit floor uniformly, rather than benefiting only the most performant implementations.
Gas Repricings: Calibrating Costs for Higher Throughput
Glamsterdam incorporates several execution layer gas repricings, designed to align costs more accurately with resource utilization at higher throughput levels. At the core of these changes is EIP-8037, which increases the gas cost for creating new state. This measure is critical for preventing unbounded state growth, even with a significantly higher gas limit.
Leading into Soldøgn, the EIP-8037 specification featured dynamic per-state-byte pricing that was contingent on the block gas limit. This dynamic pricing model introduced significant complexity for testing, creating a combinatorial explosion of fuzz matrices for each gas limit band, and rendered benchmarking nearly intractable. Early in the week, the teams reached a consensus to abandon dynamic pricing in favor of a fixed cost_per_state_byte. Future repricing adjustments will be handled at fork boundaries, rather than within a single fork.
The accounting model itself underwent an iterative refinement process. An initial breakout session on Monday shifted state-gas accounting from mid-execution to the end of call frames. A subsequent session on Tuesday addressed account creation costs, code deposit costs, and CREATE-transaction reverts. Mid-week, edge cases related to reservoir refunds and refills necessitated a fundamental re-evaluation of the model. By Thursday, the accounting model had reverted to the opcode level, with the realization that the primary complexity resided within the reservoir model itself, rather than the computational aspects of accounting. By Friday, the specification had stabilized on bal-devnet-6, with the BAL track delivering the final repricing numbers.
This entire iterative process exemplifies the critical value of interop events: the ability to resolve complex specification, implementation, testing, debugging, and design issues in a matter of hours, rather than weeks of asynchronous communication. At their most effective, interop weeks can condense a month’s worth of development progress into a single day.
The convergence of these three critical threads—ePBS, BAL optimizations, and gas repricings—culminated in the week’s headline achievement: a credible 200 million gas limit floor for the post-Glamsterdam era. This substantial increase in network capacity is made possible by the synergistic interplay of these advancements: ePBS restructures the slot to allocate more time for execution, BAL optimizations provide clients with the necessary throughput headroom within that structure, and EIP-8037 ensures that the higher gas limit does not lead to uncontrolled state expansion.
Other Glamsterdam Threads: EIPs and Architectural Refinements
Beyond the core pillars of ePBS, BALs, and gas repricings, the Soldøgn Interop addressed numerous other aspects of the Glamsterdam upgrade through dedicated breakout sessions. Consensus layer (CL) teams finalized decisions on several smaller Glamsterdam EIPs. EIP-8061, which proposes an increase in exit and consolidation churn, was successfully integrated into glamsterdam-devnet-1. EIP-8080, aimed at facilitating exits via the consolidation queue, was ultimately declined for inclusion in Glamsterdam. EIP-8045, concerning the removal of slashed validator duties, was scoped down to apply only to 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 continued work on bounded gossip message sizes for attestations under progressive lists.
A critical sync session between EL and CL teams on Wednesday morning addressed EIP-8237. The decision was made to defer this EIP out of Glamsterdam, preserving optionality for a more comprehensive "top-up sync" architecture in a future fork. In its place, the participants agreed to draft an EIP that standardizes the sequencing of forkchoiceUpdated, newPayload, and getPayload calls. This new EIP will also specify a snap-sync initiation handshake and tighten consistency between the engine API surfaces for valid and invalid block states.
Hardening and testing remained a constant theme throughout the week. A dedicated session on Thursday focused on fork-choice compliance testing frameworks, the Diamond repository of reproducible CL edge-case scenarios, and buildoor, EthPandaOps’s external builder testing tool. buildoor was demonstrated mid-session, with attendees actively suggesting attack scenarios on the spot, showcasing the tool’s versatility and the collaborative effort in identifying vulnerabilities.
Beyond Glamsterdam: Looking Towards Hegotá and Future Forks
Several breakout sessions at Soldøgn cast a forward-looking gaze towards Hegotá and subsequent network upgrades. A proposal-agnostic session on native Account Abstraction initiated discussions on the requirements and constraints that any future design must satisfy. Feature set goals such as alternative signature schemes, aggregation, batching, recovery, gas sponsorship, flexible nonces, and keystore wallets were discussed alongside critical constraints including public mempool compatibility, statelessness, and Layer 2 Denial-of-Service (DoS) resistance.
A Thursday breakout session on FOCIL focused on implementation updates. Early prototypes were already functional, with multi-client interop and a dedicated FOCIL devnet identified as immediate next steps. Two significant design decisions were reached: disabling FOCIL during 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 Ethereum P2P track outlined plans for a QUIC-based replacement for libp2p. This proposed system would feature privacy-by-default functionality and slot-aware integration. Additionally, an erasure-coded broadcast prototype demonstrated approximately six times faster propagation than GossipSub on 2.4 MB payloads. The CL track also surfaced a strong sentiment towards eventually deprecating consolidations entirely. The proposed approach involves declaring a final fork that supports consolidations and then mandating an exit-then-redeposit process, which is viewed as a cleaner long-term solution for managing validator set state growth.
ACD Process: Refining Governance and Prioritization
On Wednesday afternoon, the two co-leads of the AllCoreDevs (ACD) process, Nixo and Ansgar, facilitated a session to gather input from core contributors on the ACD process itself. This session revisited the "headliner" construct for selecting features for hard forks, debated the merits of maintaining a "strawmap" (a preliminary roadmap), and formalized criteria for EIP Special Fork Inclusion (SFI). The consensus leaned towards retaining headliners but with greater flexibility regarding the rigidity between EIPs and overarching themes, accepting a "theme plus candidate EIP" as a viable pattern. The per-fork year assignments in the strawmap beyond 2026 were flagged as overly canonicalized and likely to be softened. A new four-point SFI definition was proposed, with the AllCoreDevs Signaling (ACDS) indicating readiness and the AllCoreDevs Execution (ACDE) and AllCoreDevs Consensus (ACDC) retaining the final decision-making authority. A new prioritization and ordering process, to be implemented after CFI decisions and reflected in the meta-EIP, will supersede the previous role of SFI in driving devnet inclusion, commencing with the Hegotá upgrade.
In terms of call coordination, Alex Stokes announced a three-month sabbatical commencing the following week. Pari will assume ACDC moderation responsibilities during this interim period, and Barnabas will fill in for ACDT. The updated leadership structure for ACD calls will see Nixo and Ansgar chairing ACDE, Pari as interim ACDC moderator, and Mario, Barnabas, and Danceratopz rotating ACDT moderation duties.
Everything Else: A Myriad of Progress
In addition to the major focus areas, the in-person nature of Soldøgn Interop facilitated progress on a wide array of other critical topics. Teams leveraged the time for significant advancements in test harnesses, compressing Hive feedback loops from hours to mere minutes. Improvements were made to engine API plumbing, including gossip deduplication, batched calls, and light-client-driven head discovery. Furthermore, difficult trade-offs regarding client diversity and numerous other ancillary topics were thoroughly explored and addressed. The complete list of session notes is publicly available at soldogn.xyz.
Next Steps: From Interop to Production
Following the intensive week in Svalbard, development teams are returning to their respective organizations to translate the prototypes developed during the interop into production-ready code. The coming weeks will be characterized by a dedicated focus on hardening client implementations against the new specifications, finalizing test coverage, and integrating the draft Pull Requests (PRs) from Soldøgn into the codebase.
As is customary, the final decisions on critical values, such as the 200 million gas limit target and precise repricing numbers, will be made and publicly communicated during AllCoreDevs (ACD) calls. These decisions are expected to be the primary focus of the upcoming ACD sessions.
The success of Soldøgn Interop is a testament to the dedication and collaborative spirit of the Ethereum core contributors who traveled to the remote location of 78 degrees North. Special recognition is due to EthPandaOps for their instrumental role in organizing and motivating the group daily, and to all who worked diligently under the midnight sun to achieve the ambitious daily goals. The presence of the Ethrex crew, participating in their first interop, further underscored the growing collaborative ecosystem. The week was remarkably productive, and the forthcoming short film promises to be a compelling record of this significant development sprint.
