Elon Musk's xAI has moved into OpenAI's old HQ: report

• Elon Musk's xAI has moved into OpenAI's founding HQ.
• Musk cofounded OpenAI in 2015 and leased the AI startup's first office, according to a lawsuit.
• Musk subsequently left OpenAI and has become increasingly critical of the company, founding rival startup xAI last year.

Elon Musk is racing to upstage OpenAI — and now the billionaire has moved his own AI startup into the company's old HQ.

Musk's AI startup xAI has taken over OpenAI's original office in San Francisco's Mission district, according to a report from the San Francisco Business Times.

It comes amid an escalating war of words between the Tesla CEO and the AI startup he helped found in 2015.

An xAI invite-only open house held on Tuesday was reportedly hosted at the office on 3180 18th Street, known as the Pioneer Building.

Attendee Martin von Hagen told the San Francisco Chronicle that Elon Musk announced that xAI would be occupying the office space, which Musk said had already been refurbished.

According to Musk's previous lawsuit against Sam Altman and OpenAI, the billionaire initially leased the Pioneer Building office when he cofounded OpenAI and paid monthly rent costs.

It is unclear what happened to this arrangement after Musk stepped down from OpenAI in 2018.

OpenAI moved out of the Pioneer Building over the summer, with the San Francisco Business Times reporting that Musk had put the offices up for sublease.

Elon Musk and OpenAI did not respond to a request for comment, sent outside normal working hours.

Musk takes on OpenAI

Relations between Musk and OpenAI have become increasingly tense in recent years.

The billionaire slammed OpenAI as "evil" in an X post on Wednesday after reports suggested the company had asked investors in its $6.6 billion funding round not to invest in OpenAI's rivals, including xAI.

Musk cofounded OpenAI with CEO Sam Altman and President Greg Brockman but stepped down from the company's board of directors three years later.

Since then, he has become increasingly critical of the company's commitment to safety and its partnership with Microsoft.

The billionaire founded his rival startup xAI last year and, in August, refiled a previously dropped lawsuit against Altman and OpenAI that claimed he'd been "deceived" into cofounding OpenAI.

Do you work at xAI or have any information to share? Get in touch with this reporter via email at tcarter@businessinsider.com.