OpenAI hired xAI Chief Financial Officer Mike Liberatore after the finance expert quit Elon Musk’s company just a few months into the job, CNBC reported.

Liberatore will become the US startup’s business finance officer, overseeing billions of dollars in AI infrastructure spending, CNBC said, citing a company spokesperson. He will report to Chief Financial Officer Sarah Friar starting Tuesday, according to the report.

The former executive joined xAI this year and was involved in some of the company’s fundraising efforts and data center expansions in Memphis. But he left the company in July, just three months after starting, according to the Wall Street Journal.

The move is likely to stoke tensions between OpenAI chief Sam Altman and Musk, one of the tech industry’s highest-profile feuds.

The billionaire founder of xAI Holdings — which now houses the Grok AI team and X social network — worked with Altman to found OpenAI a decade ago before going on to launch his rival startup.

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He’s been locked in a legal skirmish with OpenAI, repeatedly trying to derail the startup’s plans to restructure as a more conventional for-profit business. The billionaire filed two lawsuits against OpenAI for allegedly straying from its founding principles, and asked a court to block the company’s overhaul.

Liberatore’s departure leaves vacant an important role at xAI, which has been raising money aggressively as it seeks to expand its AI infrastructure, including data center projects and computing chips. Mahmoud Reza Banki, a former executive at Tubi, is still working as CFO of X.

Jared Birchall, who leads Musk’s family office and is involved in fundraising across his companies, is also heavily involved in financial decisions at xAI, Bloomberg News has reported.