Biggest US funding rounds, week ending 4th September

Updated September 2026. By Remy Beaumont.

Total raised in the US this week: approximately $1.9bn across 20+ disclosed rounds.

Key takeaways

• Odyssey raised $310m in a Series B at a $1.45bn valuation for AI world models, led by Natural Capital with Amazon, AMD Ventures, Google Ventures, and others backing the round.

• Owner.com closed $240m in a Series D at $2.3bn, surpassing $100m ARR and expecting to drive over $1bn in restaurant sales this year.

• Felix raised $200m for WhatsApp-based remittances for Latino immigrants, structured as $87m equity led by a16z and General Catalyst plus $113m debt.

• Cybersecurity produced the week's most striking pattern: $150m in seed capital across two deals (Ent.AI at $100m, AIR Security at $50m), both focused on securing AI agents.

• AIR Security's two-round, same-day announcement is the week's best tactical case study. Two tier-1 lead names from a six-month-old company created a narrative that a single $50m round would not have matched.

• Quantum, defence AI, and healthcare continued to draw growth-stage capital with Atom Computing, Twenty Technologies, and Cityblock Health each closing $100m or more.

What did the US funding week look like?

The week ending 4th September 2026 produced approximately $1.9bn in disclosed US funding across more than 20 rounds. That figure sits neatly within the $2bn baseline that has held steady since August, once you strip out the Anthropic $65bn outlier from earlier in the month. The steady state is holding. What is shifting is the composition.

For the running picture across the month, see our monthly roundup of the biggest US funding rounds.

Three things stand out. First, AI infrastructure capital is rotating from pure compute into adjacent layers: world models (Odyssey), data centre interconnects (AttoTude), and quantum hardware (Atom Computing). The GPU cloud and chip rounds that dominated August are giving way to the next ring of the stack. Second, vertical AI platforms, companies embedding AI into a specific industry's workflows, drove the two largest rounds by valuation: Owner.com in restaurants and Felix in remittances. Third, cybersecurity had a breakout week, with $150m flowing into seed-stage companies building security for AI agents. That last point deserves its own section.

How did AIR Security turn two seed rounds into one momentum story?

AIR Security's announcement on 1st September is the week's most instructive case for founders planning their raise narrative.

The company emerged from stealth with $50m in total seed funding, structured across two back-to-back rounds closed on the same day. The first was a $10m seed led by Sequoia. The second was a $40m round led by Greenoaks. AIR Security was founded in February 2026. It was six months old at the time of announcement.

This is a deliberate structuring choice, not a funding necessity. A company raising $50m in seed capital from willing investors does not need to split the round in two for operational reasons. The split exists for narrative reasons.

Here is why it works. A "$50m seed round led by Sequoia and Greenoaks" is one headline. A "company raises $10m from Sequoia, then immediately raises $40m from Greenoaks on the same day" is a momentum story. The second framing implies competitive demand, escalating conviction, and speed. It tells the market that the second investor moved fast because the first was already in. Whether that sequence was genuinely competitive or choreographed in advance does not matter for the press effect. The story structure carries the signal.

The two-lead-name mechanic also doubles the firm-level distribution. Sequoia's network amplifies the story to one audience. Greenoaks amplifies it to another. Two separate lead names create two separate endorsement signals, each carrying the weight of a tier-1 firm putting its brand behind a six-month-old company.

For founders: if you have more capital committed than you need at the seed stage, consider whether splitting the round across two named leads creates a stronger announcement than a single larger round with one lead and a list of participants. The tradeoff is complexity in closing, but the press upside can be significant.

AIR Security builds an AI agent security firewall, positioning itself at the boundary between autonomous AI systems and the enterprise environments they interact with. The Israeli-founded team is targeting what it sees as the inevitable perimeter problem: as AI agents proliferate, the attack surface shifts from human-operated endpoints to agent-operated workflows.

The cybersecurity mega-seed trend

AIR Security is not an isolated signal. The same week, Ent.AI closed a $100m seed round for AI workspace cybersecurity. Led by Decibel Partners, the round included Craft Ventures, Sequoia, IQT, Felicis, and Shield Capital. The founding team came from RiskIQ and Microsoft's Security Copilot programme.

Two agentic AI security companies raised a combined $150m at the seed stage in a single week. That deserves context.

Historically, seed rounds above $20m were rare. Seed rounds above $50m were essentially non-existent outside of repeat founders with exceptional track records. A $100m seed is not a seed in the traditional sense. It is a bet sized like a Series B, placed at the earliest possible stage, by investors who believe the category window is closing fast.

The logic is straightforward. AI agents are being deployed into enterprise environments at an accelerating rate. Every major foundation model provider is shipping agent capabilities. Every enterprise software company is integrating them. The security layer for those agents does not yet exist at scale. The investors writing $50m and $100m seed cheques are making a timing bet: the security category will crystallise within 12 to 18 months, and being the incumbent when it does is worth overpaying for at the seed stage.

For founders in adjacent spaces, the signal is clear. If your category is obviously necessary, obviously early, and obviously going to attract multiple well-funded entrants, the investors who led AIR Security and Ent.AI are telling you that they will pay a premium for speed. Get there first, raise more than you think you need, and use the announcement itself as a competitive moat.

Which were the biggest US funding rounds this week?

Odyssey, $310m Series B at $1.45bn valuation. Menlo Park-based Odyssey raised the week's largest round for AI world models, technology that generates realistic, physically accurate simulations of real-world environments. Led by Natural Capital, with Amazon, AMD Ventures, EQT, Google Ventures, IQT, and SignalRank participating. Total raised to date: $337m. World models sit at the intersection of generative AI and simulation, with applications spanning autonomous systems, robotics, and synthetic training data. The $1.45bn valuation on a Series B signals investor conviction that world models will become foundational infrastructure rather than a niche research output.

Owner.com, $240m Series D at $2.3bn valuation. Owner.com builds an AI-powered restaurant management platform covering online ordering, marketing, and operations. Led by Goldman Sachs with Headline, Redpoint, and Meritech. The company has crossed $100m in annual recurring revenue and expects to facilitate more than $1bn in restaurant sales this year. The $2.3bn valuation at Series D, for a company selling into an industry known for thin margins and high churn, suggests Owner.com has found a pricing and retention model that works. Announced 29th August.

Felix (Felix Pago), $200m Series C. Miami-based Felix enables WhatsApp-based remittances for Latino immigrants in the United States. The round comprised $87m in equity led by a16z and General Catalyst, plus $113m in debt from the GC Customer Value Fund. QED, Castle Island, Switch, Contour, and Endeavor Catalyst also participated. The equity-plus-debt structure reflects the economics of remittance businesses: capital-intensive float requirements that are better served by debt than by dilutive equity. Announced 1st September.

Chronograph, $140m PE growth round. New York-based Chronograph builds portfolio monitoring software for private capital allocators. Led by Sixth Street Growth. Total raised: $160m. As private markets expand in both size and complexity, the software layer that tracks portfolio performance, calculates carry, and generates LP reporting becomes essential infrastructure. Chronograph is positioning itself as that layer.

alice, $140m. AI trust, safety, and security platform alice raised $140m from Norwest, ClalTech, CRV, NFX, Grove Ventures, Highland Europe, and Apax. The breadth of the investor syndicate, spanning US, Israeli, and European firms, signals that AI safety tooling is viewed as a global opportunity rather than a US-specific market.

Cityblock Health, $116m Series E. AI-driven value-based care platform serving government health programmes. Led by General Catalyst. Cityblock targets underserved populations enrolled in Medicaid and dually eligible programmes, using AI to coordinate care delivery and reduce costs. The Series E signals that value-based care, after years of mixed results from earlier entrants, is finding a viable model when paired with AI-driven care coordination.

Blank Street, $105m. Specialty coffee chain Blank Street raised $105m from General Atlantic. The company uses automated brewing technology to reduce labour costs and maintain consistency across locations. Coffee is not a sector that typically appears in venture funding roundups, but Blank Street's thesis is that automation can make specialty coffee unit economics work at scale in a way that labour-dependent models cannot.

Hydra Host, $100m Series A. Boulder-based Hydra Host builds a bare-metal GPU platform for distributed AI compute. Led by Kindred Ventures, with ARK, Founders Fund, Nvidia, and Comcast Ventures. Total raised: approximately $119m. A $100m Series A for GPU infrastructure reflects the same dynamic seen in Lambda's debt facility last week: AI compute providers are raising infrastructure-scale capital at earlier and earlier stages.

Ent.AI, $100m seed. Santa Clara-based Ent.AI builds AI workspace cybersecurity tools. Led by Decibel Partners with Craft Ventures, Sequoia, IQT, Felicis, and Shield Capital. The founding team includes veterans of RiskIQ and Microsoft's Security Copilot programme. See the cybersecurity mega-seed analysis above.

Twenty Technologies, $100m Series B at $1bn valuation. Arlington, Virginia-based Twenty Technologies builds AI cyber warfare capabilities for the US military. Led by Accel with Caffeinated Capital, Friends & Family Capital, and Point72. Total raised: $138m. Defence AI is attracting Silicon Valley growth capital at scale, with Accel leading a round for a company building offensive and defensive cyber tools for government customers.

Atom Computing, $100m Series C. Berkeley-based Atom Computing develops neutral-atom quantum computing systems. Led by Third Point Ventures with Cisco and DCVC. The company also received a $100m Department of Commerce Letter of Intent under the CHIPS and Science Act. Total raised: approximately $191m. The DoC Letter of Intent is significant: it signals that quantum computing is now included in the government's strategic semiconductor and advanced computing agenda alongside classical chip manufacturing.

Where is US capital flowing?

The week's deal flow reveals three concurrent capital rotations.

AI infrastructure is moving up the stack. Last month's biggest rounds went to GPU clouds and chip designers. This week's infrastructure capital went to world models (Odyssey), data centre interconnects (AttoTude, $52m Series C), bare-metal GPU platforms (Hydra Host), and quantum hardware (Atom Computing). The base layer of compute is being treated as increasingly commoditised. The value is migrating to the layers that sit above raw GPUs: orchestration, interconnection, simulation, and alternative compute architectures.

Vertical AI platforms are commanding the highest valuations. Owner.com at $2.3bn and Felix at $200m raised are both companies that embed AI into a specific industry workflow rather than selling horizontal AI tools. The restaurant management platform and the WhatsApp remittance product share a structural similarity: they own the customer relationship end-to-end, use AI to reduce operational costs, and generate revenue from the transaction itself rather than from software subscriptions alone.

AI security is being pre-funded at unprecedented scale. $150m in seed capital across two deals in one week is not a trend. It is a land grab. Investors are betting that AI agent security will be a mandatory enterprise spend category within 18 months, and they are willing to write seed cheques at Series B sizes to secure their position.

Notable signals from the syndicate composition

General Catalyst appeared in three separate deals this week: Felix (co-lead with a16z), Cityblock Health (lead), and indirectly through the GC Customer Value Fund providing Felix's $113m debt facility. GC is deploying across fintech, healthcare, and lending infrastructure simultaneously, using its Customer Value Fund to provide debt capital alongside equity investments. This blended model, equity plus affiliated debt, gives GC deeper economics in capital-intensive businesses than a pure equity investor can achieve.

Goldman Sachs appeared as lead investor in Owner.com and as a participant in the previous week's Socure round. The bank's direct investment arm is increasingly active in growth-stage AI companies, particularly those with proven revenue. For founders at the Series C and D stage with strong ARR metrics, Goldman's direct investment team is now a credible lead alongside traditional growth equity firms.

The rest of the week's top US rounds

What should founders raising soon do this week?

Study the two-round, same-day mechanic. AIR Security's structure is replicable if you have multiple committed leads. Splitting a round into two named tranches creates a momentum narrative that a single round cannot. The tradeoff is coordination complexity, but the press amplification from two tier-1 firm names is measurable.

Consider equity-plus-debt structures for capital-intensive models. Felix's $87m equity plus $113m debt is a template for any business with high float, inventory, or receivables requirements. Debt for the capital-intensive component preserves equity for growth. General Catalyst's Customer Value Fund model, where the equity lead also provides affiliated debt, is a structure worth exploring with firms that offer it.

Position your security narrative now. If you are building anything that touches AI agents, the $150m in seed-stage cybersecurity funding this week tells you that investors are actively looking for the security layer. Even if you are not a security company, articulating how your product handles agent authentication, access control, and audit trails will become a due diligence requirement within the next two quarters.

Track the infrastructure-to-application rotation. The biggest rounds are shifting from raw compute (GPUs, chips, cloud) to what sits above it: world models, interconnects, orchestration, quantum. If you are raising for infrastructure, your pitch needs to explain why your layer has not yet been commoditised and when it will develop pricing power.

Frequently asked questions

What were the biggest US funding rounds this week? Odyssey raised $310m in a Series B at a $1.45bn valuation for AI world models. Owner.com closed $240m in a Series D at $2.3bn for AI restaurant management. Felix raised $200m in a Series C ($87m equity, $113m debt) for WhatsApp-based remittances. Chronograph raised $140m in PE growth funding for portfolio monitoring software. alice raised $140m for AI trust, safety, and security.

How much did US startups raise in total this week? Approximately $1.9bn across more than 20 disclosed rounds for the week ending 4th September 2026. This continues the steady baseline of approximately $2bn per week that has held since August, once you exclude Anthropic's $65bn outlier.

Why is the cybersecurity mega-seed trend significant? Two agentic AI security companies raised a combined $150m at the seed stage in one week. Ent.AI closed a $100m seed led by Decibel Partners with Sequoia, Craft Ventures, and Felicis. AIR Security emerged from stealth with $50m across two back-to-back seed rounds from Sequoia and Greenoaks. Seed rounds at this scale are historically unusual and signal that top-tier investors view AI agent security as a category worth pre-empting before product-market fit is proven.

What was AIR Security's two-round, same-day announcement strategy? AIR Security announced $50m across two seed rounds on the same day: a $10m first close led by Sequoia, followed immediately by a $40m second close led by Greenoaks. The company was founded in February 2026 and was only six months old at announcement. By structuring two rounds with two tier-1 lead names, AIR Security created a momentum narrative that a single $50m announcement from one lead would not have produced.

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