AI Startups Lead a $3.9B Week in U.S. Startup Funding

AI drew the largest checks in a varied week for U.S. startup funding. Tenstorrent raised $1.5 billion at a $6.2 billion valuation, while Flapping Airplanes secured $1 billion less than 10 months after its seed round. Together, those financings account for $2.5 billion of the ten listed rounds. The rest spanned infrastructure software, space technology, drug development, robotics, an online business platform and manufacturing tools.

That mix matters: the list shows how investors are backing both AI model development and applications in specific industries, while substantial sums also flowed to companies whose core businesses aren’t described as AI. The funding amounts alone don’t establish how quickly these companies can turn capital into products or revenue. Valuations offer a snapshot of how the rounds were priced, but don’t reveal the terms or future performance.

AI infrastructure and industry applications

Tenstorrent, based in Santa Clara, California, raised $1.5 billion in Series E funding. Trace Capital and Innovation X led the round, which valued the 10-year-old developer of AI processors and systems at $6.2 billion. That pairing of a large financing with an established company’s $6.2 billion valuation makes Tenstorrent the week’s largest deal by amount and the clearest example of investors putting capital behind the hardware and systems that support AI computing.

Flapping Airplanes raised $1 billion in Series A funding, led by Lux Capital and Index Ventures. The San Francisco AI lab is working on models intended to cost less to train and run. It had raised $180 million in seed financing less than 10 months earlier. The quick succession of the seed and Series A rounds, along with the new financing’s size, puts the company among the week’s biggest funding stories. The stated cost focus also points to a business challenge for AI labs: building models is only part of the equation if the expense of operating them limits their use.

Two other rounds applied AI to sectors with distinct technical demands. Boston-based ASI raised $325 million in Series C funding, led by Spark Capital, at a $3 billion valuation. Its software is designed to secure and operate critical infrastructure in fields including aviation and transportation. Arda Industries, meanwhile, raised $160 million in Series A funding at a $1.5 billion valuation. The San Francisco company develops AI-powered manufacturing engineering software; Altimeter Capital, Accel and Khosla Ventures co-led the round. Arda also disclosed a previously unreported $72 million seed financing, putting its total disclosed funding across the two rounds at $232 million.

Biotech and space add scale

Three financings brought substantial capital to space and life sciences. Xona raised $250 million in Series D funding, led by Future Ventures. The Burlingame, California-based startup is developing a next-generation version of GPS, and the round set its valuation at $2.4 billion.

New York-based Pathos AI, which applies AI to drug development, completed a $237 million Series E financing at a post-money valuation around $3 billion. Bristol-Myers Squibb led the financing. Warp Sciences raised $215 million in a Series A led by Lightspeed Venture Partners. The company combines AI and robotics to speed the development of medicines. These rounds put capital behind different approaches to drug development, though the funding figures don’t indicate how soon either business will produce results.

Star Therapeutics raised $200 million in new financing led by OrbiMed and Janus Henderson Investors. The South San Francisco drug developer’s financing followed Incyte’s July purchase of Star subsidiary Vega Therapeutics, in a deal valued at up to $2 billion. That figure describes the maximum value of the subsidiary deal; the source doesn’t provide further terms. Star’s new financing is a separate event and should be read on its own terms.

Marketplace funding and the weekly tally

New York-based Whop raised $200 million in Series D funding, co-led by Sequoia Capital and Shopify Ventures. The platform helps entrepreneurs build and run online businesses, and the round valued it at $5.1 billion. Its financing shows that the week’s large checks weren’t confined to AI, biotechnology or space ventures.

The ten listed rounds total $4.087 billion, including Warhound’s $200 million seed financing, according to the amounts in the roundup. The deals were announced for Oct. 17–23, 2026, and the tally covers U.S.-based companies tracked in the Crunchbase database. Its figures may miss some rounds reported late in the week, so the total is a snapshot of reported financings rather than a complete count of every deal closed during that period. For comparison across rounds, the listed stages range from seed to Series E, while only some entries include valuations; those differences limit what the weekly ranking alone can show about company maturity or financing terms.

Illustration: Dom Guzman