Giulio Rebuffo, formerly chief technology officer of the Ethereum client Erigon, has joined the Ethereum Foundation, where his work will center on applying artificial intelligence to client development.

Clients are the software implementations that execute Ethereum's rules and keep the chain running, and the network deliberately runs on several independent ones — Erigon and Geth among them — a design intended to keep a bug in any single implementation from stalling the network on its own.

Rebuffo announced the move on X on Friday, November 13, writing that his new role is focused on “applied AI x Client Dev,” and adding that he “will be working alongside the technical teams and the management.”

The appointment lands in a year in which at least eight senior researchers and leaders have left the nonprofit.

From high school contributor to Merge engineer

Rebuffo's path into Ethereum is far from typical. In an interview given in October 2025, he recounted starting on TurboGeth, the project that became Erigon, while still in high school, and becoming one of Ethereum's youngest core developers at 17.

He served as principal engineer on Erigon during the Merge, Ethereum's switch in 2022 to proof-of-stake, and had taken over as the client's CTO by age 22. His work at Erigon focused on prototyping features and squeezing more speed out of the protocol without changing it through hard forks.

The skill he names as most important is adversarial thinking: assuming that any code he writes will be attacked. His new role at the foundation concentrates on AI.

Eight high-profile exits and counting

The workforce Rebuffo is joining looks different from that of a year ago. The foundation has seen significant exits throughout the year, and at least eight of them are high-profile.

Researchers Julian Ma and Carl Beek resigned in May. Before them, Tomasz Stańczak stepped down as co-executive director in February, having spent less than a year in the job. Josh Stark and Protocol Guild organizer Trent Van Epps announced their exits on the same day in April. The three leads of the influential Protocol cluster, Barnabé Monnot, Tim Beiko, and Alex Stokes, also moved on or went on sabbatical, which pushed the foundation to install Will Corcoran, Kev Wedderburn, and Fredrik as new cluster coordinators.

Geth creator Péter Szilágyi had left the previous year after about a decade. Earlier in November, a former employee sued the foundation and co-founder Vitalik Buterin over a firing.

Buterin's case for AI-written code

Rebuffo's mandate maps 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 client targeting Ethereum's draft 2030 roadmap. The project was put together in roughly six days using Claude Code, at a cost of about $5,750.

Buterin said that teams should “take half the gains from AI in speed, and half the gains in security.” He pushed for more test cases, more formal verification, and more independent implementations of the same software.

In a May blog post on formal verification, the practice of mathematically proving that code behaves as intended, Buterin expanded on those points. Done well, he wrote, it could produce code that is “far more secure than the way programming has been done before.” He framed AI-assisted verification as a defense against AI-assisted attacks on crypto infrastructure.

Rebuffo's appointment gives that argument a staffed counterpart inside the foundation.

A rebuild, or just one hire

The foundation has now hired an engineer with deep client experience and pointed him at AI tooling, testing, and verification. Observers looking for further high-profile replacements for the executives who departed this year may have to wait longer.

Buterin confirmed in June that the foundation had cut 20% of its workforce and was also going to cut 40% of its budget, moves that prompted think pieces and posts questioning whether the foundation could fall short in delivering on the blockchain's roadmap. That remains to be seen.

Rebuffo will work across the technical teams and management, per his post, placing him close to the client developers. Buterin wants code written and checked faster. What to watch from here is whether the AI push shows up in the software itself: whether experimental AI-built clients like ETH2030 mature toward production-grade code, and whether the test cases and formal verification Buterin has called for begin appearing in the independent clients the network runs on.