Alphabet (NASDAQ:GOOGL) owned Google co-founder Sergey Brin has been back working at the tech giant’s Mountain View, California offices in recent months, alongside researchers, according to a report from The Wall Street Journal on Friday.

Brin is said to be visiting the offices three to four days a week, working with researchers as they try to develop the company’s next large artificial intelligence system.

WSJ sources told the publication that while he participated in meetings about AI late last year, the frequency and intensity of his involvement have since increased.

Brin stepped down from an executive role at Alphabet in 2019 and has since taken a hands-off approach. However, there has been a shift in gears in recent months.

He has reportedly been working closely with researchers at GOOGL’s newly constructed Charleston East building, creating Google’s long-awaited AI model Gemini, and discussing technical matters such as “loss curves.”

Sources told the WSJ that Sundar Pichai, chief executive of both Google and Alphabet, is excited about Brin’s involvement and has encouraged his contributions.