OpenAI, one of the darlings of the San Francisco office market, has vacated its headquarters at 3180 Mission St.

A company affiliated with Elon Musk, a co-founder of OpenAI, offered the building for sublease this month, the San Francisco Business Times reported.

San Francisco’s AI darling OpenAI is moving out of the famous Pioneer Trunk Factory.

An unnamed source told the Business Times that OpenAI was leaving the building, also known as the Pioneer Trunk Factory, due to competition from Musk’s new artificial intelligence firm, xAI. An OpenAI spokesperson denied this claim and confirmed that the company had left the office, but said it was because it had grown too big for the space.

Musk split from OpenAI in 2018 and filed suit against the company in February, claiming it had shirked its mission and put profits above the public good. In documents filed as part of that lawsuit, Musk’s lawyers wrote that he pays monthly rent for the Mission Street space, the Business Times reported.

Musk withdrew the lawsuit in June, but refiled it earlier this month.

Representatives for Musk did not respond to requests for comment Monday afternoon.

OpenAI made waves in fall 2023 when it signed the largest office lease in the Bay Area since before the pandemic. The company took over two buildings from Uber totaling 486,000 square feet. It later signed another lease for the 315,000-square-foot 550 Terry Francois.

The leases of the company and other AI companies offer a glimmer of hope in San Francisco’s otherwise gloomy office market.

Bisnow reached out to Raise Commercial Real Estate, a technology-focused brokerage firm that has represented OpenAI in its real estate transactions, but did not receive a response.

JLL, which will handle the sublease at the Pioneer Trunk Factory, did not respond to a request for comment.