Layla Zulfa
Just over 100 Ethereum core contributors recently concluded the Soldøgn Interop, a week-long, intensive development summit held above the Arctic Circle in Longyearbyen, Svalbard. This pivotal gathering focused on advancing the "Glamsterdam" network upgrade, a critical step in Ethereum’s ongoing evolution towards greater scalability and efficiency. The secluded, polar setting, characterized by its perpetual daylight during this period, provided a unique backdrop for the developers to immerse themselves in complex technical challenges, culminating in significant breakthroughs for the network’s future.
The Soldøgn Interop, meaning "midnight sun" in Norwegian, built upon the success of previous developer gatherings like Berlinterop, Amphora, Edelweiss, and Nyota. Unlike some predecessors, it returned to a single-track format, allowing for highly focused, multi-client progress on specific upgrade components. The primary objective was to "harden" Glamsterdam, ensuring its robust implementation across the diverse client ecosystem that underpins Ethereum. By the end of the week, the concentrated effort yielded three major accomplishments: a crucial alignment on a post-Glamsterdam gas limit floor of 200 million, the successful implementation of stable ePBS (enshrined Proposer-Builder Separation) with external builders, and the finalization of repricing numbers for EIP-8037, a key Ethereum Improvement Proposal. Additionally, substantial progress was made on features earmarked for future upgrades, such as "Hegotá," including FOCIL (Forward-Compatible Index List) and native account abstraction.
The Arctic Crucible: A Unique Setting for Innovation
The choice of Svalbard, a Norwegian archipelago nestled deep in the Arctic Ocean, was more than just an exotic locale; it held symbolic and practical significance for the Ethereum community. Longyearbyen, the world’s northernmost permanent settlement, offers a unique environment where, notably, anyone can live and work without a visa, regardless of nationality. This open-access policy mirrors the decentralized, permissionless ethos of Ethereum itself.
Beyond its welcoming immigration policy, Svalbard is home to the Global Seed Vault and the Arctic World Archive. These "cold storage" facilities, burrowed deep into the permafrost, safeguard humanity’s most vital information – from agricultural seeds to historical documents and critical source code, including a snapshot of Ethereum’s own foundational code. This connection resonated deeply with developers dedicated to building a resilient, long-lasting digital infrastructure. The concept of preserving essential data for future generations provided a powerful metaphor for their work on Ethereum, a network designed to be a permanent, censorship-resistant public utility.
Furthermore, the period from late April through August in Svalbard experiences 24/7 daylight, a phenomenon known as the midnight sun. This "24/7 uptime" mirrored the always-on nature of the Ethereum blockchain, allowing core developers to work intensely around the clock, blurring the traditional lines between day and night, and maximizing their collaborative output. The intense, focused environment, far removed from daily distractions, proved highly conducive to tackling complex technical challenges.
Glamsterdam: Hardening the Network for Scalability
The overarching goal of the Soldøgn Interop was to fortify Glamsterdam implementations and establish a definitive target for a post-upgrade gas limit floor. The gas limit, a measure of the maximum computational work allowed in a single block, directly impacts Ethereum’s transaction throughput and, consequently, its ability to scale. Raising this limit safely is a multifaceted challenge, demanding careful consideration of how blocks are constructed and proposed, the operational headroom of client implementations under heavy load, and how the costs associated with creating new state scale with increased transaction volume.
The current Ethereum gas limit typically hovers around 30 million. The agreement to target a 200 million gas limit floor post-Glamsterdam represents a nearly seven-fold increase in potential block capacity. This significant expansion is anticipated to dramatically improve network throughput, reduce transaction fees (assuming sustained demand), and enable more complex applications to operate on the blockchain. Achieving this ambitious target required simultaneous advancements across several key technical areas: ePBS, Block-Level Access Lists (BAL), and gas repricings via EIP-8037.
A Week of Intense Collaboration: The Soldøgn Interop Chronology
The interop was characterized by a rapid, iterative cycle of coding, testing, debugging, and collaborative decision-making. Developers frequently worked until the early hours, punctuated by focused breakout sessions to achieve alignment on design choices and discuss long-term roadmap items. The in-person format proved invaluable, compressing what would typically be weeks of asynchronous discussion and development into days.
Three teams from the Ethereum Foundation provided crucial infrastructure support for the week. EthPandaOps delivered ethIQ for performance monitoring and a panda MCP server to facilitate agentic workflows. Protocol Support managed soldogn.xyz, serving as the single source of truth for interop goals, schedules, and notes. The EF Digital Studio team documented the entire week on film, promising an upcoming interop documentary.
Key Achievements of the Soldøgn Interop
1. Enhanced Block Production: Understanding ePBS
Enshrined Proposer-Builder Separation (ePBS) is a critical component of Glamsterdam, designed to refine the relationship between block proposers (validators) and block builders (specialized entities that construct transaction bundles). Beyond clarifying these roles, ePBS fundamentally restructures block slots by introducing explicit deadlines for block construction, payload revelation, and attestations. This architectural change allocates more predictable time for execution, thereby increasing the "headroom" necessary to safely raise the gas limit.
The week began with the ambitious goal of establishing a stable 4 Execution Layer (EL) x 4 Consensus Layer (CL) Glamsterdam devnet by Monday evening. Initial attempts revealed several issues, pushing the target to Tuesday, when a 4×3 configuration achieved sufficient stability for stress testing to commence. The remainder of the week involved a rigorous ePBS hardening cycle: continuous stress testing, identification and resolution of edge cases, and repeated fixes. A Tuesday morning breakout session significantly streamlined the Builder API specification, simplifying validator registration, the bid/header/commitments flow, the trust model for builder payments, and circuit-breaker behavior. Mid-week debugging efforts pinpointed cross-client edge cases, particularly concerning execution-request invalidation of beacon requests. A newly developed test suite exposed a critical gap across all client implementations, which was subsequently addressed. By Thursday, CL teams reported stable ePBS, with EL-side bid pathways being debugged and resolved by Friday. Two complex questions remain under active debate by the All Core Developers (ACD): whether a request signature should commit to the receiving builder, and how to maintain the resilience of a 1 ETH-staked-builder design against P2P Sybil-based liveness attacks. Despite these open points, by Friday, nearly all clients were successfully running together on glamsterdam-devnet-2, with the external builders pipeline thoroughly tested end-to-end.
2. Optimizing Execution: Block-Level Access Lists (BAL)
While ePBS addresses the consensus layer’s role in scaling, Block-Level Access Lists (BALs), defined in EIP-7928, constitute a dominant execution layer counterpart. BALs provide clients with upfront information about a block’s read/write set, enabling crucial optimizations such as parallel execution, batched I/O operations, and parallel state-root computation. These capabilities are fundamental in determining how large a block clients can efficiently process.
The BAL track at Soldøgn operated on its own dedicated devnets, isolated from the Glamsterdam ePBS chains, preventing entanglement of optimization benchmarks with consensus-layer stabilization efforts. Each optimization was placed behind its own feature flag, allowing for isolated measurement and comparison. The BAL benchmark dashboard and leaderboard were instrumental in highlighting each client’s worst-case scenarios across the test suite. By focusing on improving the slowest paths first, teams effectively elevated the gas limit floor across the board, rather than solely optimizing for the fastest implementations.
3. Sustainable Growth: EIP-8037 Gas Repricings
Glamsterdam integrates several execution layer gas repricings designed to calibrate transaction costs more accurately to actual resource usage at higher throughputs. EIP-8037, which focuses on increasing state-creation gas costs, is central to this effort. Its purpose is to raise the price of writing new state, ensuring that a higher gas limit does not lead to unchecked state growth, which could burden node operators and compromise network health.
Initially, the EIP-8037 specification proposed dynamic per-state-byte pricing tied to the block gas limit, which proved combinatorially challenging for testing and nearly intractable for benchmarking. Early in the week, teams collaboratively decided to abandon dynamic pricing in favor of a fixed cost_per_state_byte, with future repricings to be handled at subsequent hard fork boundaries. The accounting model for gas repricings underwent an iterative refinement process. A Monday breakout moved state-gas accounting from mid-execution to end-of-call-frame. A Tuesday follow-up addressed account creation costs, code deposit costs, and CREATE-transaction reverts. By Wednesday, reservoir refund/refill edge cases necessitated a fundamental rethink. A Thursday breakout reverted accounting to the opcode level, concluding that the primary complexity lay within the reservoir model itself. By Friday, the specification had stabilized on bal-devnet-6, with the BAL track delivering the final repricing numbers. This rapid resolution of complex specification, implementation, testing, debugging, and design issues underscores the unique efficiency of interop weeks.
Ultimately, these three convergent threads – ePBS providing more execution time, BAL optimizations increasing client throughput, and EIP-8037 ensuring sustainable state growth – enabled the core contributors to confidently propose a credible 200 million post-Glamsterdam gas limit floor, a monumental step for Ethereum’s scaling ambitions.
Refining the Upgrade: Other Glamsterdam Scope Decisions
Beyond the core components, several breakout sessions addressed other Glamsterdam-scoped EIPs. Consensus Layer (CL) teams finalized decisions on smaller EIPs: EIP-8061 (exit/consolidation churn increase) was included in glamsterdam-devnet-1. EIP-8080 (exits via the consolidation queue) was declined. EIP-8045 (slashed-validator duty removal) was refined to apply only to proposer duties within the look-ahead window. EIP-7688 (SSZ stable containers) remains within Glamsterdam’s scope but was held out of glamsterdam-devnet-1 pending work on bounded gossip-message size for attestations under progressive lists.
A Wednesday morning Execution Layer (EL)/Consensus Layer (CL) sync architecture breakout deferred EIP-8237 out of Glamsterdam to preserve optionality for a longer-term "top-up sync" architecture in a future fork. In its place, the group agreed to draft a new EIP that standardizes forkchoiceUpdated, newPayload, and getPayload sequencing, specifies a snap-sync initiation handshake, and tightens valid/invalid consistency between the engine API surfaces. The theme of hardening was pervasive throughout the week, with a Thursday session covering fork-choice compliance testing frameworks, the Diamond repository for reproducible CL edge-case scenarios, and buildoor, PandaOps’s external-builder testing tool, which was demoed with immediate attack scenario suggestions from attendees.
Paving the Way for Future Forks: Beyond Glamsterdam
The interop also dedicated significant time to discussions beyond the immediate Glamsterdam upgrade, looking towards future forks like "Hegotá" and beyond. A proposal-agnostic session on native Account Abstraction explored the requirements and constraints for any future design. Key feature goals identified included alternative signature schemes, aggregation, batching, recovery, gas sponsorship, and flexible nonces, all while adhering to strict constraints around public-mempool compatibility, statelessness, and Layer 2 (L2) DoS resistance.
A Thursday FOCIL (Forward-Compatible Index List) breakout provided updates on implementation, with early prototypes already functional. Multi-client interop and a dedicated FOCIL devnet were identified as immediate next steps. Two notable design decisions were made: 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 into the future, a long-running ETH P2P track outlined a QUIC-based replacement for libp2p, aiming for privacy-by-default and slot-aware integration. A prototype for erasure-coded broadcast simulated approximately six times faster propagation than GossipSub for 2.4 MB payloads. The CL track also expressed strong sentiment towards eventually deprecating consolidations entirely, suggesting a final fork that supports them before requiring exit-then-redeposit for validator set management, as a cleaner long-term solution to validator-set state growth.
Strengthening Governance: The All Core Devs (ACD) Process
A dedicated session led by Nixo and Ansgar, the two ACDE co-leads, gathered input from core contributors regarding the All Core Developers (ACD) process. Discussions revisited the "headliner construct," debated the merits of a "strawmap" for future upgrades, and formalized EIP SFI (Specification Freeze Index) criteria. The consensus favored retaining headliners but with greater flexibility, accepting "theme + candidate EIP" as a viable pattern. The long-term year assignments in the strawmap beyond 2026 were deemed overly canonicalized and likely to be softened. A new four-point SFI definition was proposed, with ACDT (All Core Devs – Testing) signaling readiness and ACDE (All Core Devs – Execution) / ACDC (All Core Devs – Consensus) retaining the final call. A new prioritization-ordering process, to be produced after CFI (Call for Inclusion) decisions and reflected in the meta-EIP, will replace SFI’s former role in driving devnet inclusion, starting with Hegotá.
On the call-coordination front, Alex Stokes announced a three-month sabbatical, with Pari stepping in as interim ACDC moderation and Barnabas filling in for ACDT. This establishes Nixo and Ansgar as chairs for ACDE, Pari as interim for ACDC, and Mario, Barnabas, and Danceratopz rotating ACDT moderation.
Everything Else
Beyond the headline achievements, the in-person setting facilitated progress on a multitude of other initiatives. Teams advanced efforts on improving test harnesses, significantly compressing Hive feedback loops from hours to minutes. Improvements were made to engine-API plumbing, including gossip deduplication, batched calls, and light-client-driven head discovery. Crucial discussions also addressed difficult tradeoffs around client diversity and numerous other topics. A comprehensive list of session notes is available at soldogn.xyz.
Implications for Ethereum’s Future
The achievements at the Soldøgn Interop have profound implications for Ethereum’s future. The agreed-upon 200 million gas limit floor signals a major leap in the network’s capacity, promising lower transaction fees, faster transaction processing, and the ability to support more complex and data-intensive decentralized applications (dApps). The hardening of ePBS ensures a more robust and efficient block production mechanism, while BAL optimizations enhance execution efficiency. EIP-8037’s repricings lay the groundwork for sustainable growth, preventing state bloat even with increased throughput.
The progress on future features like native account abstraction and FOCIL demonstrates a clear roadmap for improving user experience and developer capabilities. The ongoing refinement of the ACD process reflects a mature and responsive governance model, essential for guiding such a complex, globally distributed open-source project. This interop solidifies Ethereum’s commitment to continuous improvement and its ambitious vision for a scalable, decentralized future.
Next Steps and Outlook
Following this highly productive week, core development teams will return home to translate the prototypes and agreements made in Svalbard into production-ready code. The coming weeks will be dedicated to hardening client implementations against the new specifications, finalizing test coverage, and merging the draft PRs (Pull Requests) into the main codebase.
The final decisions regarding critical values such as the 200 million gas limit target and the definitive repricing numbers will be publicly announced and discussed on upcoming All Core Devs calls. These calls are expected to be the primary forum for these significant topics in the immediate future.
The Ethereum community extends profound gratitude to all contributors who journeyed to 78°N and made the Soldøgn Interop a resounding success. Special recognition is due to EthPandaOps for their organizational prowess and to everyone who dedicated themselves under the midnight sun, including the Ethrex crew, who marked their first interop experience. The week’s extraordinary productivity ensures that a full short film will serve as a lasting testament to this pivotal gathering.
