Ethereum Foundation hires Erigon’s Giulio Rebuffo to apply AI to clients

Giulio Rebuffo, Erigon’s former chief technology officer, has joined the Ethereum Foundation to work on applying AI to client development.

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

The hire comes after a year in which at least eight senior researchers and leaders left the nonprofit.

From high-school contributor to the Merge engineer

Rebuffo is not a typical new hire. 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.

Rebuffo was the principal engineer on Erigon during the Merge, which was Ethereum’s switch in 2022 to proof-of-stake. He took 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 any code he writes will be attacked.

His new role at the foundation focuses on AI.

Eight high-profile exits and counting

The Ethereum Foundation that Rebuffo is joining is not the same in terms of its workforce. This is because it has seen significant exits all through the year, and at least eight of them are high-profile.

Researchers Julian Ma and Carl Beek resigned in May, and 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. A former employee sued the foundation and co-founder Vitalik Buterin over a firing earlier in November.

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. This was done in roughly six days using Claude Code for 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 blog on formal verification, which is the practice of mathematically proving that code behaves as intended, that was published in May, Buterin expanded on his previous talking points.

Done well, Buterin 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.

A rebuild, or just one hire

The foundation has hired an engineer with deep client experience pointed at AI tooling, testing, and verification.

Some observers that may be looking out for other high-profile replacements for the foundation’s executive that have left this year may have to wait longer.

Buterin confirmed in June that the foundation had cut 20% of its workforce, and it was also going to cut 40% of its budget. There were think pieces and posts about how the foundation may come short of delivering on the blockchain’s roadmap as a result of those cuts. That is to be seen.

Rebuffo will work across the technical teams and management, per his post, which places him close to the client developers. Buterin wants writing and checking code faster.