Ethereum’s weekly All Core Developer calls are a lot to keep up with, so this "Checkpoint" series aims for high-level updates roughly every 4-5 weeks, depending on what’s happening in core development. See the previous update here.

Fusaka follows this year's Pectra upgrade, representing a major step forward in Ethereum's scaling roadmap by introducing PeerDAS and key improvements that enhance blob throughput, L1 performance, and user experience. This post announces the testnet activation schedule for the first three testnets, beginning with Holesky at slot 5,283,840 (October 1, 2025, 08:48:00 UTC). See the activation table below for the complete Sepolia and Hoodi timeline. Fusaka also introduces Blob Parameter Only (BPO) forks to safely scale blob throughput after PeerDAS activation. These are minimal, config-only upgrades that adjust the blob target/max and fee update fraction. The Fusaka testnet client releases are listed below. Once all three testnets have successfully upgraded, a mainnet activation slot will be chosen.

World’s Fairs have historically showcased the biggest innovations of their time like telephones, televisions, photography, and light bulbs. In this spirit, Ethereum gets its own World’s Fair this November in Buenos Aires. A week where the ecosystem doesn’t just talk about innovation, but showcases what’s being built now, and what’s next. We’re creating a space to see, touch, and experience the frontier of technology. A World’s Fair that showcases what Ethereum can do today.

Today, we are excited to announce the start of the Fusaka audit contest, co-sponsored by Gnosis and Lido, hosted on Sherlock, and running for four weeks from September 15th. The goal is simple: maximize scrutiny of the Fusaka upgrade and surface vulnerabilities before they can impact the network. To raise the stakes, valid findings reported in the first week have a 2x multiplier applied to their points rewarded, and those in the second week have a 1.5x multiplier. To help security researchers, we’ve prepared a Fusaka auditor guide.

As previously announced, the Holešky testnet has reached its planned end-of-life date and will be sunset shortly. The vast majority of remaining validator nodes will be shut down 2 weeks after the Fusaka upgrade has finalized on Holešky. After this, Holešky will no longer be supported by client, testing or infrastructure teams. Following the launch of the Hoodi testnet in March 2025, infrastructure providers and staking operators have had the opportunity to migrate their testing operations.

A few months ago, we announced a renewed focus of Protocol on three strategic initiatives: Scale L1, Scale blobs, Improve UX. Following previous updates on Scale L1 and Scale blobs, this note relates to our “Improve UX” track, and its mission: Seamless, secure and permissionless experience across the Ethereum ecosystem, for individuals and institutions. We see interoperability, and related projects presented in this note, as the highest leverage opportunity within the broader UX domain over the next 6-12 months, in our position as a public, core Ethereum R\&D group. The near-term strategy focuses on areas we believe will continue to be fundamental components of interop: Intent-based architecture and general message-passing. For both, our aim is to focus on clear, measurable protocol metrics to drive down latency and cost,

The EF’s Grants Program launched in 2018 and has evolved over time to become the Ecosystem Support Program (ESP), providing grants and support to builders that help the Ethereum ecosystem thrive. Our mission is to enable work that strengthens Ethereum’s foundations and empowers future builders, in domains such as developer tooling, research, community building, infrastructure, and open standards. In 2024 alone, ESP awarded close to $3M in funding to 105 projects and initiatives that came through our open grants program webforms. These grants, which are one part of ESP’s larger portfolio, supported a diverse range of work, such as Commit-Boost (developer tooling), BundleBear (data and analytics), Web3Bridge (education), ZK Playbook (research), and Ethereum Cypherpunk Congress (community event). Over the past three years, we have streamlined our processes

Following up from Protocol Update 001, we’d like to introduce our approach to blob scaling. The L1 serves as a robust foundation for L2 systems to scale Ethereum, and a necessary component of secure L2 solutions is data availability provided by the L1. Data availability ensures that updates L2s make back to the L1 can be verified by anyone. Blobs are the unit of data availability in the protocol today, so scaling the blob count per block is a key requirement to usher in a wave of L2 adoption for use cases like real-time payments, DeFi, social media, gaming, and AI/agentic applications. Our work is structured as a series of incremental changes to Ethereum’s blob architecture. To accelerate our rate of scaling, we are expanding from