The Pioneer Building has become something like a revolving door for San Francisco’s tech elite. Stripe once called the three-story historic Mission District building home, followed by OpenAI and Elon Musk’s xAI. Now another buzzy artificial intelligence startup is taking over the keys.
Exa, a five-year-old AI research company launched by Harvard roommates Will Bryk and Jeff Wang, has taken over the roughly 40,000 square-foot building at 3180 18th St., the founders announced on social media Monday.
Real estate insiders confirmed to the Chronicle that its lease at the Pioneer building is for a minimum term of seven years. Exa did not immediately respond to a request for comment.
Real estate firm CBRE represented Exa in the transaction, while Charlie Hannafin of JLL represented landlord Artemis Real Estate Partners.
Exa was previously headquartered at 430 Shotwell St. in the Mission, where it grew into a provider of search infrastructure for AI that today powers search for more than 400,000 developers and customers such as Cursor, according to its own account.
The Pioneer Building is one of the few in the mission zoned as true office space rather than light industrial uses. Though Exa’s office space selection seems to have been driven, at least in part, by the 1902 landmark’s cachet of prior tenants.
“Elon assembled the Colossus cluster here (his mattress was still lying there during our tour),” said Bryk in a post to X, Musk’s social media company. “Alec Radford trained GPT-3 here. The Collison brothers built the web’s financial backbone here.”
More than a century ago the Pioneer Building was an automobile trunk factory, though it was converted into creative office space by the 1980s. Its tech transition didn’t come until 2013, when the property was acquired by real estate investment firms and leased up by online payments company Stripe, which eventually moved into larger offices in nearby SoMa, making room for AI.
The building became OpenAI’s headquarters in 2016, after Musk arranged a long-term lease through Musk Industries. Musk envisioned the Pioneer Building as a home not only for the fledgling AI nonprofit, which he helped fund, but potentially for employees from his other ventures, including Neuralink, SpaceX and Tesla.
As OpenAI’s ambitions grew, Musk clashed with co-founders Sam Altman and Greg Brockman over the company’s future, before eventually resigning as co-chair a few years later. Yet his connection to the Pioneer Building lingered, as Musk remained the leaseholder of the space even after he left OpenAI, which continued to operate out of the building for years. The company vacated in 2024, after signing a major lease in Mission Bay.
Musk formally returned to the Pioneer Building that year, moving in his, at the time, newly founded xAI company. But his lease at the building is up this month, and xAI has been growing its footprint in Palo Alto rather than opting to renew in the Mission District.
