Giulio Rebuffo

The Ethereum Foundation has hired Giulio Rebuffo, former CTO of the Erigon client, to lead applied AI work in client development, a bet that AI-assisted code writing and formal verification can accelerate protocol hardening without sacrificing security. The move signals the foundation’s confidence in AI tooling at a time when it has cut 20% of staff and 40% of budget, even as the network prepares major upgrades targeting 200M gas limits.

• Rebuffo joined the Ethereum Foundation on Friday (November 13) focused on “applied AI x Client Dev,” working across technical teams and management.
• The foundation has experienced at least eight high-profile exits in 2026, including three Protocol cluster leads, following a 20% workforce and 40% budget cut announced in June.
• Vitalik Buterin has argued that AI-written code, paired with formal verification and rigorous testing, can be “far more secure than the way programming has been done before.”

• 702,000 lines of code in AI-built Ethereum client assembled in roughly six days
• 20% workforce reduction announced by Ethereum Foundation in June 2026
• 200M gas limit floor established as post-Glamsterdam target in recent protocol interop

Rebuffo announced his move to the Ethereum Foundation on X on Friday (November 13), signaling a strategic pivot toward machine-learning-assisted protocol development at a moment when the foundation is operating under significant budget constraints. Rebuffo, who began contributing to the TurboGeth project (which became Erigon) while still in high school, rose to become the client’s principal engineer during Ethereum’s 2022 shift to proof-of-stake and later assumed the role of CTO by age 22. His new mandate focuses on integrating AI tools into the workflow of client developers, teams that write and maintain the software nodes use to participate in the network.

Rebuffo’s track record on client optimization and adversarial code review

Rebuffo’s appointment reflects a specific expertise: squeezing performance gains from existing protocol logic without requiring hard forks. In an interview given in October 2025, he identified adversarial thinking, the assumption that any code he writes will be attacked, as the most important skill in protocol engineering. That posture aligns closely with Buterin’s stated vision for AI-assisted development: using machine learning to generate code faster, then deploying formal verification and multiple independent implementations to catch flaws before they reach mainnet.

Erigon itself pioneered a lightweight architecture that reduced Ethereum node requirements compared to earlier clients like Geth, demonstrating that careful engineering can lower barriers to node participation without sacrificing security. Rebuffo’s move to the foundation places that mindset at the center of the organization’s client strategy during a period of constraint.

Foundation staffing crisis coincides with protocol acceleration goals

According to the Ethereum Foundation’s May protocol blog, the organization has experienced significant leadership turnover even as core development work accelerates. Researchers Julian Ma and Carl Beek resigned in May; Tomasz Stańczak stepped down as co-executive director in February after less than a year in the role; Josh Stark and Protocol Guild organizer Trent Van Epps announced exits in April. The three leads of the Protocol cluster, Barnabé Monnot, Tim Beiko and Alex Stokes, have moved on or taken sabbatical, forcing the foundation to install Will Corcoran, Kev Wedderburn and Fredrik as new coordinators.

Péter Szilágyi, creator of the Geth client, had left the previous year after a decade of work. In November, a former employee sued the foundation and co-founder Vitalik Buterin over a firing.

Rebuffo’s hire follows Buterin’s June confirmation that the foundation had cut 20% of its workforce and 40% of its budget, raising concerns among observers that the nonprofit might struggle to deliver on the protocol roadmap.

Buterin’s case for AI-assisted formal verification as infrastructure defense

Rebuffo’s mandate maps directly onto an argument Buterin has been making for months. In March, Buterin called an experimental AI-built client “quite an impressive experiment” after developer Jiayao Qi assembled ETH2030, a 702,000-line Go implementation targeting Ethereum’s 2030 roadmap, in roughly six days using Claude Code for approximately $5,750.

Buterin advocated that teams “take half the gains from AI in speed, and half the gains in security,” calling for expanded test coverage, more formal verification and multiple independent implementations of the same software.

In a May blog on formal verification, Buterin expanded his case. Formal verification, the practice of mathematically proving that code behaves as intended, could produce software “far more secure than the way programming has been done before” if executed properly. He framed AI-assisted verification as a structural defense against AI-assisted attacks on crypto infrastructure, arguing that the speed advantage AI introduces to attack design must be matched by equal speed and rigor in defense. That framing justifies hiring deep protocol expertise specifically to shepherd AI tooling into production workflows.

Next steps in Protocol cluster handover and Glamsterdam release timeline

The foundation’s immediate priority remains shipping Glamsterdam, the next major protocol upgrade, with devnets now live and scoping for the subsequent Hegotà upgrade already underway. The recent Svalbard interop established a 200M gas limit floor as a post-Glamsterdam target, derived from converged work on external proposer-builder separation (ePBS), block auction layer (BAL) optimizations and EIP-8037 repricing. The transition between outgoing cluster leads and their replacements occurred during that same event, with impromptu handover meetings designed to avoid distracting from immediate release work.

Rebuffo will work across technical teams and management, positioning him close to the engineers shipping these upgrades.

The CCS read. We see Rebuffo’s hire not as infrastructure rebuilding but as a focused bet that AI tooling can compress the security review cycle. With formal verification gaining traction in Ethereum research circles and budget pressure real, the foundation is betting that machine-assisted code generation and machine-checked proofs can sustain protocol velocity without proportional headcount recovery. That gamble depends on whether independent client teams adopt the same tooling.

The critical open question is whether Rebuffo can persuade other client teams, Lodestar, Nethermind, Prysm and others, to integrate AI-assisted workflows into their own development pipelines, or whether this remains an Ethereum Foundation initiative. The foundation’s new Protocol cluster coordinators will signal their commitment to this approach through their technical decisions on Glamsterdam and Hegotà scope in coming weeks.