Ethereum’s Fusaka Upgrade Set for Late 2025 as EOF Proposal Gets Scrapped

Ethereum’s next major network upgrade, Fusaka, is now expected to roll out in the third or fourth quarter of 2025, according to Tomasz Kajetan Stańczak, co-executive director at the Ethereum Foundation.

In a post published on X on April 28, Stańczak shared that while the target timeframe for Fusaka has been set, the precise schedule remains under discussion. Initially, the upgrade was anticipated to include a significant change to the Ethereum Virtual Machine (EVM) called the EVM Object Format (EOF) — but this component has since been removed following concerns from developers.

Ethereum core developer Tim Beiko confirmed the decision, citing unresolved technical uncertainties that could potentially delay the broader Fusaka deployment. Beiko detailed the removal in a GitHub post the same day.

What Was EOF Meant to Change?

The EVM, the core engine behind Ethereum’s smart contracts, executes low-level bytecode instructions compiled from programming languages like Solidity. EOF was designed to overhaul how this bytecode is structured and validated, introducing a more organized, versioned container format to separate code and data for efficiency.

Key features of EOF included:

• A standardized header (starting with 0xEF00) and versioning system.
• A metadata table describing each section of the contract.
• Clearly defined sections for code and data, with room for future expansion.

Supporters believed that EOF would make smart contracts more efficient, secure, and easier to audit. It would also simplify the deployment process by verifying bytecode structure at launch, potentially reducing bugs and vulnerabilities.

One notable change under EOF was the introduction of RJUMP and RJUMPI instructions — safer alternatives to the traditional JUMP and JUMPI commands. These new instructions aimed to eliminate dynamic jumps, a practice that can cause hidden bugs and even open doors for malicious code injections.

Meanwhile, traditional JUMP/JUMPI behavior would still be permitted but subjected to stricter validation checks under proposals like EIP-3670 and EIP-3690.

Developer Backlash Halts Progress

Despite its technical appeal, EOF sparked sharp debate among the Ethereum developer community. Critics argue that the overhaul was unnecessarily complex and risked complicating the EVM's already intricate system.

Pascal Caversaccio, an Ethereum developer, voiced concerns in a post on Ethereum Magicians, warning that EOF would introduce new semantics, overhaul opcodes, and significantly expand the attack surface. He also pointed out that maintaining legacy EVM functionality alongside EOF would likely be necessary “indefinitely,” burdening future development.

Caversaccio and others advocated for a more gradual approach, suggesting that the proposed benefits of EOF could be achieved through smaller, more targeted updates without radically altering the EVM’s foundations.

Sentiment within the wider community appears similarly divided. A poll conducted on ETHPulse, an Ethereum-focused polling platform, revealed strong opposition to EOF: 39 voters, representing almost 17,745 ETH, stood against the upgrade, compared to only seven voters in favor, who together held less than 300 ETH.

What's Next?

Although EOF will no longer be included in the Fusaka upgrade, Ethereum developers remain focused on delivering improvements that enhance the network’s scalability, security, and developer experience.

As Ethereum continues its transition toward a more modular and scalable ecosystem, the upcoming Fusaka upgrade — even without EOF — will likely play a key role in shaping the platform’s next phase of growth.

For now, the community watches closely as developers refine the roadmap, balancing innovation with the need to maintain Ethereum’s stability and developer trust.