Top image: Aerial view of San Mateo’s Hayward Park neighborhood and State Route 92, February 2018. The Concar Drive office campus sits beside the Hayward Park Caltrain station. Photo: Pi.1415926535 / CC BY-SA 3.0 via Wikimedia Commons
Fireworks AI, a San Mateo startup that runs other companies’ AI models, has leased roughly 105,000 square feet at 450 Concar Drive, the former headquarters of cloud data company Snowflake, according to the Silicon Valley Business Journal, which first reported the deal Tuesday.
The numbers are the story. Fireworks’ current headquarters spans about 21,800 square feet at 900 Concar Drive, about half a mile west, The Real Deal reported. The new space is nearly five times larger. The building itself totals about 210,000 square feet, according to Hoodline, so Fireworks will take roughly half of it.
What Fireworks actually does
Most coverage of AI focuses on training, the expensive process of building a model. Fireworks works on the other half: inference, which is the act of running a trained model to answer a request. Every time a coding assistant suggests a line or a chatbot replies, that is an inference call. Fireworks builds the backend infrastructure that lets businesses run fine-tuned versions of open-weight models, meaning models whose parameters are published and can be customized. Hoodline, summarizing Business Insider’s reporting, lists the AI coding company Cursor among its customers.
The company’s growth figures, as reported, are steep. Hoodline, citing other outlets, reported that Fireworks raised a Series D in July 2026 at a $17.5 billion valuation, crossed $1 billion in annualized revenue that month, and by October had entered early talks to raise at a valuation of $30 billion to $40 billion. The Chronicle has not independently verified those figures, and the company has not disclosed them in a public filing. They are best read as a signal of investor appetite rather than audited results.
Co-founder and chief executive Lin Qiao previously led the PyTorch team at Meta, experience Hoodline credits with underpinning investor confidence.
Why this lease matters for the Peninsula
The Concar campus, which includes 400 and 450 Concar Drive, sits beside the Hayward Park Caltrain station. Snowflake dropped its formal headquarters designation in 2021, Hoodline reported, leaving one of the Peninsula’s better-located office buildings in search of an anchor.
AI is filling that kind of gap. The Real Deal, citing JLL data reported by the Business Times, said AI and robotics companies are driving the strongest Peninsula office leasing market since 2018, with newer buildings near Caltrain stations in particular demand. Silicon Valley as a whole just logged its second-highest quarter for office leasing on record, about 3 million square feet in the third quarter, according to the same report.
There is a useful distinction here. The AI firms leasing big blocks of space in 2026 are increasingly not the model labs alone but the infrastructure layer around them: companies that serve, tune and route models for paying customers. Their headcount grows with usage, and usage is what enterprises are now buying.
The long view
Two things are worth watching. First, whether inference revenue proves durable as model prices fall and the largest labs build their own serving infrastructure; a fivefold office expansion is a bet that it will. Second, what the AI leasing wave does for transit-adjacent offices on the Peninsula. A building beside a Caltrain station is being filled by a company whose employees could commute by rail, at the same time Caltrain is warning of possible service cuts in 2028 without new operating money. The two stories are more connected than they look.
Sources
- Silicon Valley Business Journal: Fireworks AI San Mateo office expansion (Oct. 21, 2026)
- The Real Deal: Another AI firm leases bigger offices in Silicon Valley (Oct. 22, 2026)
- Hoodline: Fireworks AI signs lease at former Snowflake HQ
- Palo Alto Civic: Caltrain briefing to Palo Alto City Council (Oct. 19, 2026)
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