One of the leading companies in the AI race is doubling down on downtown San Francisco.

Real estate sources say Anthropic -- which was founded in 2021 by a group of former OpenAI researchers -- has agreed to lease two floors at 505 Howard St. in SoMa, adding to its presence at a complex known as Foundry Square.

The company is headquartered across the street, at 500 Howard St., where it subleased an entire 230,325-square-foot building from Slack in 2023. According to sources familiar with the new deal, Anthropic negotiated a short-term lease at 505 Howard St. so that both contracts will expire at the same time, in 2028.