US startups raised approximately $9.3bn across 16+ major disclosed rounds. The Boring Company led with $3B for tunnel infrastructure backed by UAE sovereign capital. Cognition AI hit $48B valuation on $2B raise. Defence, AI infrastructure, and vertical AI platforms dominated.
Updated September 2026. By Remy Beaumont.
Total raised in the US this week: approximately $9.3bn across 16+ major disclosed rounds.
Key takeaways
The Boring Company raised $3bn in a Series D at a $23bn valuation, led by the United Arab Emirates with Sequoia and Andreessen Horowitz participating. The round coincides with a contract to build 150+ km of tunnels across the UAE.
Cognition AI raised $2bn at a $48bn valuation in a Series E led by Andreessen Horowitz and Accel, nearly doubling its worth in four months. Run-rate revenue reportedly approaching $900m.
Stoke Space closed the initial $1bn tranche of its Series E for fully reusable rockets. The Exploration Company raised $450m for European orbital logistics on the same day. Space infrastructure pulled over $1.4bn in a single session.
Positron AI raised $875m at a $5bn valuation for memory-first AI inference processors, just seven months after its $230m raise at $1.06bn.
Defence manufacturing continues to draw enormous capital: Mach Industries added $600m to its Series C, pushing the round to $900m total and its valuation to $3.7bn.
What did the US funding week look like?
The week ending 11th September 2026 produced approximately $9.3bn in disclosed US funding across more than 16 major rounds. This is a substantial increase on the prior week's approximately $1.9bn and ranks among the largest weekly totals of 2026 outside the frontier AI megarounds.
The composition tells the real story. Three themes dominated: physical infrastructure at venture scale (Boring Company, Stoke Space), AI silicon and interconnect (Positron, Ayar Labs), and vertical AI platforms controlling entire workflows (Cognition, Harvey, Clay). The pure software application layer took a back seat.
For founders reading the week's data, the signal is straightforward: investors paid the largest premiums for companies that control something scarce. Tunnels, launch capacity, inference memory, defence production lines, legal operating systems. Generic AI wrappers did not feature.
How did Cognition AI turn a four-month sprint into an 85% valuation jump?
Cognition AI's announcement on 9th September is the week's most instructive capital-market story.
The company raised $2bn at a $48bn valuation, up from $1bn at $26bn just four months earlier. The Series E was led by new investors Andreessen Horowitz and Accel, with Founders Fund, General Catalyst, Avenir, Benchmark, Bessemer, Kleiner Perkins, Greylock, Lightspeed, Altimeter, T. Rowe Price, DST and others participating.
What justified the reprice? Revenue velocity. Cognition says its run-rate revenue climbed from $492m to nearly $900m over the same four-month window. Those are company-reported run-rate figures, not audited annual revenue, but they represent a growth trajectory that makes most enterprise SaaS companies look static.
The tactical lesson sits in the investor composition. Cognition brought in two new tier-one leads (a16z and Accel) while retaining an unusually broad existing syndicate. That structure creates competitive tension between new and existing investors: the new leads validate the higher price, while existing backers' willingness to follow at the markup reinforces conviction. The combined signal is stronger than either group alone.
The underlying product story matters too. Cognition started with Devin, positioned as an autonomous AI software engineer. It has since acquired Windsurf and expanded beyond a single-agent product into what it calls an AI engineering platform. Customers include NVIDIA, GE Aerospace, Citi, and Mercedes-Benz. The company is no longer selling a coding assistant. It is selling a system that sits between engineering leadership and production code.
For founders planning a fast reprice: revenue velocity is the credibility engine, but the investor structure is the announcement architecture. Two new leads plus broad existing follow-on creates a story that one lead alone cannot match.
Which were the biggest US funding rounds this week?
The Boring Company, $3bn Series D at $23bn valuation. Led by the United Arab Emirates, with Sequoia Capital, Andreessen Horowitz, and Baron Capital participating. The financing coincides with an agreement to build more than 150 kilometres of tunnels across the UAE. The Boring Company's main operating showcase remains the Vegas Loop. This round represents the clearest example yet of sovereign capital and commercial deployment arriving together: the UAE is simultaneously financing and buying. Announced 10th September.
Cognition AI, $2bn Series E at $48bn valuation. Led by Andreessen Horowitz and Accel. Makers of Devin, the autonomous AI software engineer. Run-rate revenue approaching $900m, up from $492m four months ago. See the full teardown above. Announced 9th September.
Stoke Space, $1bn Series E initial close. Co-led by Point72 Ventures and Spark Capital. Total capital raised now $2.3bn. Stoke is developing Nova, a fully reusable two-stage rocket targeting first orbital flight in early 2027. The round sizes reflect investor conviction that reliable launch capacity is strategically scarce. Announced 8th September.
Positron AI, $875m Series C at $5bn valuation. NEA, Atreides Management, Valor Equity Partners, Andra Capital, SemiAnalysis Capital, and Jim Clark co-led. Qatar Investment Authority, Cisco Investments, and Naver Ventures participated. Positron builds memory-first inference processors with up to 2.3 terabytes of memory per chip. The company says it is deploying more than 50 racks at Oracle Cloud Infrastructure. Announced 10th September.
Mach Industries, $600m Series C extension at $3.7bn valuation. Ribbit Capital, Infinite Capital, Bedrock Capital, and Sequoia participated. Mach manufactures unmanned military systems, drones, and counter-drone products from its own 115,000-square-foot facility. The valuation doubled in roughly three months. Announced 10th September.
Harvey, $550m at $15.6bn valuation. Diffusion and Lightspeed co-led. Sequoia, Kleiner Perkins, a16z, Coatue, GIC, and Goldman Sachs Alternatives also participated. Legal AI platform used by 80% of the top 100 US law firms. Revenue reportedly above $400m. Also announced acquisition of agent-security startup Guardrails AI, its fourth acquisition this year. Announced 9th September.
Cylake, $245m convertible notes. Lightspeed, Picture Capital, and Redpoint Ventures. Cybersecurity platform for "operational sovereignty," approaching beta release. The convertible structure at this size, ahead of broad product disclosure, is unusual optionality capital. Announced 9th September.
Solstice Oncology, $225m Series A. RA Capital Management, Canaan Partners, and Forbion. Second-generation CTLA-4 cancer immunotherapy. One of the year's largest biotech launches. Announced 9th September.
Forus, $150m Series C at $3bn valuation. Bain Capital Ventures led, with Thrive Capital, General Catalyst, and Accel. AI agents that manage the operational steps between prescription and treatment. Works with 9 of the 15 largest biopharma companies. Valuation tripled in four months. Announced 8th September.
Ayar Labs, $150m Series E extension. Silicon-photonics company replacing copper chip-to-chip connections with optical links. Total Series E now $650m at approximately $5bn valuation. Announced 10th September.
Other notable rounds: Split Pay ($125m, consumer fintech, Khosla/Thrive), BrainChild Bio ($116m Series A, pediatric brain cancer CAR-T), Clay ($115m Series D at $7.1bn, AI sales platform), Perry Weather ($110m Series C, weather safety operations), Savvy Wealth ($100m Series C, AI wealth platform), Inspiren ($70m Series C, senior-living AI).
