One of the original employees at Elon Musk’s xAI has left and returned to OpenAI

It’s been less than a year since Elon Musk formally launched his generative AI company—xAI—and one of its original employees has already parted ways with the startup.

Kyle Kosic, a founding engineer and one of xAI’s first 11 employees, left to return to his former employer and xAI rival OpenAI. Kosic left xAI in April, according to his LinkedIn profile, and his departure had not been previously reported.

OpenAI confirmed Kosic had rejoined the company, but declined to comment further. xAI and Kosic did not return requests for comment.

Kosic’s exit came about a month before xAI announced its $6 billion funding round, which valued the new generative AI entrant at a heaping $24 billion. During those fundraising efforts, Kosic had been featured prominently as a founding member of xAI’s team in a slide deck distributed to prospective investors, which Fortune obtained. The deck said Kosic is a full-stack reliability engineer and data scientist and that he was focused on automation, scalability, and distributed computing at xAI.

Kosic’s departure is just the latest in the ongoing rivalry between OpenAI—which Musk cofounded in 2015, then left three years later—and Musk’s newest venture, xAI. Musk has positioned xAI as an open-source generative AI company that is going after “understanding the universe.”

The feud between xAI and OpenAI—the two most valuable AI startups—has been anything but private. Musk, who left OpenAI after a power struggle, has repeatedly raised concerns about the dangers of that company’s technology. Earlier this year, Musk sued OpenAI, alleging the company had breached its founding agreement (he withdrew that lawsuit earlier this month). Shortly after the lawsuit was filed, OpenAI fired back, publishing redacted emails to present what the company argued to be “facts about our relationship with Elon.”

It’s still early days for xAI and the chatbot it released at the end of last year, called “Grok.” Musk said he intended it to be “anti-woke,” in response to missteps by rival chatbots. While the company has raised billions of dollars in funding in such a short period of time, it’s a late entrant into the space, with others like OpenAI, Anthropic, and Cohere already in the market for years.

xAI currently has around 100 employees, according to estimates from PitchBook. And the company is hiring—with a series of open engineer and AI tutor roles posted on its website. Apart from Kosic, all of xAI’s original employees appear to still be with the company.

For his part, Musk hopes to leverage proprietary data from his web of companies—ranging from X and SpaceX to Tesla and brain chip startup Neuralink, in order to set xAI apart from its peers. The slide deck that was shared with investors highlighted the importance of xAI’s ties to the “Muskonomy”—laying out how xAI can tap visual, sensory, navigation, and all sorts of other data from his various companies.

Jessica Mathews

Update, June 28, 2024: This article has been updated with confirmation from OpenAI.

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The rest of today’s Data Sheet was written by David Meyer.

This story was originally featured on Fortune.com