This past week, just over 100 Ethereum core contributors gathered above the Arctic Circle — in Longyearbyen, Svalbard — for the Soldøgn Interop: a week of intense work on the Glamsterdam network upgrade. This pivotal event, steeped in the tradition of previous intensive development gatherings like Berlinterop, Amphora, Edelweiss, and Nyota, focused on a singular, ambitious objective: the hardening of the Glamsterdam network upgrade. The summit culminated in significant breakthroughs, most notably the alignment on a post-Glamsterdam gas limit floor of 200 million, stable execution-layer proposer-builder separation (ePBS) implementations, and the finalization of EIP-8037 repricing numbers.
The choice of Longyearbyen, Svalbard, as the venue for Soldøgn was deliberate and symbolic. This remote Norwegian archipelago offers a unique environment, notably being one of the few places on Earth where individuals of any nationality can reside and work without requiring a visa. Beyond its accessibility, Svalbard is home to the Global Seed Vault and the Arctic World Archive, subterranean facilities dedicated to preserving humanity’s most vital data and cultural heritage. These institutions, tunneling deep into the permafrost, safeguard backups of crops, literature, films, manuscripts, and even source code, including a snapshot of Ethereum’s own codebase, for potential future generations. Furthermore, the perpetual daylight during the Arctic summer, from late April through August, provided a fitting backdrop for developers working around the clock, mirroring Ethereum’s own 24/7 operational uptime. This extended period of continuous activity, where the sun never sets, fostered an environment of relentless focus and accelerated progress.
Harden Glamsterdam, Scale Ethereum
The primary objective of the Soldøgn Interop was to consolidate and stabilize the Glamsterdam network upgrade, with a specific focus on increasing Ethereum’s transaction throughput. Raising the gas limit, a critical metric for network capacity, is a complex, multi-faceted challenge. Glamsterdam addresses several key areas contributing to this complexity: the methodologies by which blocks are constructed and proposed, the available headroom for client implementations under significant load, and the scaling mechanisms for state creation costs as throughput increases.
The week’s intensive efforts translated into tangible outcomes by Friday. A stable, multi-client Glamsterdam development network (devnet) was established, running the latest ePBS protocols, alongside updated block access list (BAL) specifications. Crucially, this environment generated comprehensive benchmarking data, providing a solid foundation for proposing a credible increase to the gas limit. The majority of the week was dedicated to deep coding sessions, often extending into the early hours of the morning, interspersed with focused breakout sessions to achieve consensus on design decisions and to strategize on the longer-term roadmap.
Supporting this concentrated development effort were three Ethereum Foundation (EF) teams. EthPandaOps provided essential infrastructure, deploying ethIQ for performance analysis and a Panda MCP server to facilitate agentic workflows. The Protocol Support team established soldogn.xyz as the central repository for interop goals, schedules, and meeting notes, ensuring a single source of truth for all participants. The EF Digital Studio team documented the entire week, promising a forthcoming documentary that will capture the unique collaborative spirit and technical achievements of the summit.
ePBS: Enhancing Block Construction and Throughput
Execution-layer proposer-builder separation (ePBS) represents a significant architectural shift in Ethereum’s block production. Beyond refining the relationship between proposers and builders, ePBS introduces explicit deadlines for various stages of block construction, including payload reveal and attestation submission. This procedural clarity allocates more time for the execution layer to process transactions, thereby increasing the potential headroom for raising the gas limit.
The week commenced with an ambitious target: establishing a four-execution-layer (EL) and four-consensus-layer (CL) Glamsterdam devnet by Monday evening. Initial challenges encountered during this phase necessitated a revised target of Tuesday, by which time a 4×3 configuration was sufficiently stable to initiate stress testing. This marked the beginning of an intensive ePBS hardening cycle, characterized by a pattern of stress testing, identification of edge cases, implementation of fixes, and repetition.
A key breakout session on Tuesday morning significantly streamlined the Builder API specifications. This encompassed validator registration, the flow of bids, headers, and commitments, the trust model for builder payments, and the implementation of circuit-breaker mechanisms. Mid-week debugging efforts focused on cross-client edge cases, particularly concerning the invalidation of beacon requests by execution-layer requests. A newly developed test suite revealed a persistent gap across all client implementations in this area. By Thursday morning, CL teams reported stable ePBS integration, while EL-side bid pathways continued to undergo debugging, with resolutions achieved by Friday. Two contentious issues remain for the All-Core-Devs (ACD) working group: whether a request signature should explicitly commit to the receiving builder, and how to maintain the resilience of a 1 ETH-staked-builder design against peer-to-peer Sybil-based liveness attacks. Despite these remaining questions, by Friday, nearly all participating clients were operating cohesively on the glamsterdam-devnet-2, with the external builder pipeline tested end-to-end.
BAL Optimizations: The Execution Layer’s Scaling Solution
While ePBS addresses the consensus layer’s contribution to Glamsterdam’s scaling strategy, the execution layer’s advancements are primarily driven by gas repricings and Block-Level Access Lists (BALs). BALs provide clients with upfront visibility into a block’s read and write sets, enabling critical optimizations such as parallel execution, batched input/output operations, and parallel state-root computation. These improvements 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, ensuring that optimization benchmarks were not influenced by the complexities of consensus-layer stabilization. Each optimization was implemented with its own feature flag, allowing for isolated comparison of performance metrics. The BAL benchmark dashboard and leaderboard provided insights into each client’s worst-case performance scenarios across the test suite. By prioritizing the optimization of the slowest execution paths, developers aimed to elevate the gas limit floor universally, rather than solely benefiting the fastest implementations.
Gas Repricings: Calibrating Costs for Higher Throughput
Glamsterdam incorporates several gas repricings within the execution layer, meticulously calibrating transaction costs to align with resource utilization at higher throughput levels. A central component of this effort is EIP-8037, which increases the gas cost associated with creating new state. This measure is designed to prevent a higher gas limit from translating into unbounded state growth.
Prior to Soldøgn, the EIP-8037 specification featured dynamic per-state-byte pricing that was directly tied to the block gas limit. This approach presented significant testing challenges, requiring a combinatorial fuzz matrix for each gas limit band and making benchmarking nearly intractable. Early in the week, participants agreed to transition away from dynamic pricing in favor of a fixed cost_per_state_byte. Future repricing adjustments will be managed at fork boundaries, rather than being dynamically adjusted within a single 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 the call frame. A subsequent session on Tuesday addressed account creation costs, code deposit costs, and CREATE-transaction reverts. On Wednesday, challenges related to reservoir refund and refill edge cases prompted a fundamental reevaluation. By Thursday, the accounting model reverted to the opcode level, with the conclusion that the primary complexity resided within the reservoir model itself, not in the accounting computation. By Friday, the specification had stabilized on bal-devnet-6, with the BAL track delivering the final repricing numbers. This iterative process exemplifies the power of interop events, compressing weeks of asynchronous progress into days by enabling rapid resolution of complex specification, implementation, testing, debugging, and design issues.
The convergence of these three critical threads—ePBS, BAL optimizations, and gas repricings—culminated in the week’s headline achievement: a credible target of a 200 million gas limit floor post-Glamsterdam. This substantial increase is underpinned by ePBS, which structures the block slot to afford the execution layer more processing time; BAL optimizations, which provide clients with the necessary throughput headroom within that structure; and EIP-8037, which ensures that the increased gas limit does not lead to uncontrolled state expansion.
Other Glamsterdam Threads: EIPs and Architectural Decisions
Beyond the core advancements in ePBS, BALs, and gas repricings, the Soldøgn Interop addressed numerous other aspects of the Glamsterdam upgrade. Consensus-layer teams finalized decisions on several smaller Glamsterdam EIPs. EIP-8061, which aims to increase 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 cycle. 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.
An important architecture breakout session on Wednesday morning, involving both EL and CL teams, led to the decision to defer EIP-8237 from Glamsterdam. This decision preserves optionality for a more comprehensive "top-up sync" architecture in a future fork. In its place, the session agreed to draft a new EIP that standardizes the sequencing of forkchoiceUpdated, newPayload, and getPayload calls. This new EIP will also specify a snap-sync initiation handshake and enforce tighter consistency between the engine API surfaces for valid and invalid states.
Hardening and robust testing remained a pervasive theme throughout the week. A dedicated session on Thursday explored frameworks for fork-choice compliance testing. The Diamond repository, a collection of reproducible CL edge-case scenarios, and buildoor, PandaOps’s external-builder testing tool, were showcased. During the buildoor demonstration, attendees actively suggested attack scenarios, which were then simulated in real-time, highlighting the collaborative and adaptive nature of the interop process.
Beyond Glamsterdam: Looking Towards Hegotá and Future Forks
Several breakout sessions at Soldøgn cast their gaze towards Hegotá, the subsequent network upgrade, and subsequent forks. A deliberately proposal-agnostic session on native Account Abstraction initiated discussions around the fundamental requirements and constraints that any future design must satisfy. Key feature-set goals, including alternative signature schemes, aggregation, batching, recovery, gas sponsorship, flexible nonces, and keystore wallets, were considered alongside critical hard constraints such as public mempool compatibility, statelessness, and L2 Denial-of-Service resistance.
A dedicated FOCIL breakout session on Thursday focused on implementation updates. Early prototypes for FOCIL were already functional, with multi-client interop and the establishment of a dedicated FOCIL devnet identified as immediate next steps. Two significant design decisions were also made: FOCIL will be disabled during periods of two-epoch non-finality, mirroring the behavior of the proposer-boost circuit breaker, and an index-based bookmark approach will be adopted to ensure compatibility with frame transactions and EIP-7702.
Looking further ahead, a long-running ETH P2P track explored the potential for a QUIC-based replacement for libp2p, designed with privacy-by-default features and slot-aware integration. Additionally, a prototype for erasure-coded broadcast demonstrated approximately six times faster propagation speeds compared to GossipSub for 2.4 MB payloads. The CL track also revealed a strong consensus towards the eventual deprecation of consolidations. The proposed approach involves designating a final fork that supports consolidations and subsequently requiring validators to exit and redeposit, presenting a cleaner long-term solution for managing validator-set state growth.
ACD Process: Refining Governance and Prioritization
A significant session on Wednesday afternoon, led by ACDE co-leads Nixo and Ansgar, gathered input from core contributors regarding the All-Core-Devs (ACD) process. This session revisited the "headliner" construct, debated the merits of maintaining a strawmap, and formalized EIP Specification Freeze Indicator (SFI) criteria. The consensus favored retaining headliners while relaxing the rigid distinction between EIPs and broader themes, accepting a "theme plus candidate EIP" approach as a viable pattern. The strawmap’s per-fork year assignments beyond 2026 were identified as potentially over-canonicalized and likely to be softened. A new four-point SFI definition was proposed, signaling ACDT readiness and reserving the final decision-making authority for ACDE and ACDC. A new prioritization and ordering process, to be implemented after CFI decisions and reflected in the meta-EIP, will supersede SFI’s previous role in dictating 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 cover ACDT duties. The updated leadership structure for core developer coordination includes Nixo and Ansgar chairing ACDE, Pari serving as interim ACDC moderator, and Mario, Barnabas, and Danceratopz rotating ACDT moderation.
Everything Else: A Broad Spectrum of Progress
Beyond the major initiatives, teams utilized the in-person collaboration at Soldøgn to advance a wide array of other critical areas. This included improvements to test harnesses, significantly compressing Hive feedback loops from hours to mere minutes. Progress was also made on engine-API plumbing enhancements, such as gossip deduplication, batched calls, and light-client-driven head discovery. Furthermore, difficult trade-offs concerning client diversity and numerous other topics were thoroughly discussed and resolved. The complete compilation of session notes is accessible on soldogn.xyz.
Next Steps: From Arctic Innovation to Production Readiness
The developers now return from Svalbard to transition the prototypes developed during the Soldøgn Interop into production-ready code. The coming weeks will be characterized by intensive efforts to harden client implementations against the newly established specifications, finalize test coverage, and integrate the draft PRs from the summit into the main codebase.
As is customary, final decisions regarding key values, such as the 200 million gas limit target and the precise repricing numbers, will be formally announced and publicly shared during AllCoreDevs calls. These critical decisions are expected to be the primary focus of discussions in the immediate future.
The success of the Soldøgn Interop is a testament to the dedication and collaborative spirit of the Ethereum core development community. The unique setting above the Arctic Circle fostered an environment of intense focus and innovation, yielding significant advancements towards a more scalable and robust Ethereum network. The forthcoming documentary promises to be a compelling record of this extraordinary week of progress under the midnight sun.
