Artificial intelligence startup Anthropic committed to its burgeoning office footprint in downtown San Francisco by signing a direct lease for 240K SF at 500 Howard St.

Anthropic had subleased the space from workplace messaging platform Slack, which vacated the property in 2023 for new headquarters in Salesforce Tower, the San Francisco Business Times reported. Anthropic’s sublease was set to expire in 2028.

The building is the third downtown office property occupied by Anthropic, the SFBT reported. At the end of January, Anthropic leased the entirety of 300 and 342 Howard St., a 480K SF deal that was one of the largest single-tenant leases inked in the city in the past five years, according to the San Francisco Chronicle.

In March, Anthropic added about 100K SF at 400 Howard St. and another 100K SF at 505 Howard St., the SFBT reported. All told, the developer of AI assistant Claude has leased approximately 850K SF in a three-block section of downtown San Francisco over the past three years.

The lease at 500 Howard St. was signed directly with the building’s landlord, according to a statement an Anthropic spokesperson provided to Bisnow. Lease terms weren’t disclosed, but the long-term deal will help the company plan in the future as it scales its headcount in San Francisco.

Anthropic’s physical expansion dovetails with its rapid rise as a company. The startup, founded in early 2021 by siblings Dario and Daniela Amodei, closed $30B in a Series G funding round that values the company at $380B. The funding will fuel expansions in research, product development and infrastructure, Anthropic said.

Anthropic’s run-rate revenue, meanwhile, soared from $100M in 2024 to $14B in 2026. Business subscriptions to Claude Code have quadrupled this year, the company said, with enterprise use accounting for more than half of Claude Code revenue.

Anthropic rival OpenAI, maker of ChatGPT, is also on a leasing tear. In late March, OpenAI leased a five-building office campus in Mountain View. Earlier in the month, the company subleased the 280K SF former headquarters of Dropbox.