YC's Spring 2026 Demo Day unveils 11 standout startups in defense tech, AI, and developer tools.
With each new season comes another YC Demo Day. On Tuesday, the Spring 2026 cohort was unveiled, filled with defense tech, robotics, AI infrastructure and developer tools, and of course, AI agents. TechCrunch spoke to eight investors to determine which ones were the hottest companies in this batch — both the ones they were watching and the startups they heard other VCs couldn’t get enough of.
This list consists primarily of companies that had been flagged by at least two investors as the buzziest in the batch. That excitement translated into larger rounds and massive price tags for some of these companies. Just when we thought YC valuations couldn’t get any higher, they surpassed all expectations.
This batch had at least two startups fetching valuations of $175 million or more. Investors were also clearly willing to pay a premium for proven, repeat founders. We’ve organized the standouts alphabetically below: What it’s building: AI-powered counter-drone systems Why it’s a fav: The Russia-Ukraine conflict is showing just how lethal small drones are, with the systems now accounting for roughly 80% of casualties.
Existing counter-drone solutions are expensive and often useless at jamming swarms of drones flying at low altitudes. 9 Mothers claims that it developed a more “affordable” robot that can track and kill drones traveling at 60 miles per hour. Founded in 2024, the startup has already booked $1.6 million in sales, with a single contract expected to expand to $35 million later this year.
The company is also promising investors that it can reach a pipeline of $1 billion in contracts. That potential coupled with a clear need had VCs eager to invest, at a valuation of upward of $200 million, one VC told us. At that valuation, 9 Mothers is not only the most highly valued startup of the batch, but also potentially one of the most valuable in YC history.
(9 Mothers did not respond to our request for comment.) What it’s building: A tool that provides digital twin environments for testing AI agents Why it’s a fav : AI helps software engineers generate more code at much faster speeds. That code needs to be tested, but traditional testing environments, also known as sandboxes, cannot be created fast enough to keep up. Arga Labs solves this bottleneck by instantly spinning up “digital twins” of a company’s software, allowing AI agents to safely test their code before it reaches production.
What it’s building: Mobile MRI clinics for early cancer detection Why it’s a fav : We know early detection saves lives, but the healthcare system doesn’t have enough MRI machines to screen everyone regularly. They are just too expensive — costing millions to buy and tens of thousands a year to maintain. Adialante is trying to solve this problem.
The startup says it has designed a compact MRI unit that can be transported in a small truck. Adialante’s business model is to bring these machines to clinics and charge $250 a scan. The company’s massive but worthwhile ambition is to change MRI scans from being reserved for symptomatic patients into a routine annual screening.
What it’s building: Compliance management for physical products Why it’s a fav : It can be quite complicated to ship physical goods across borders. There are so many regulations, such as ensuring proper translations when selling into the EU, or ensuring a beauty product’s labeling complies with each country’s labeling requirements. Complir hopes to make this easier by creating AI agents that help businesses manage and monitor compliance, risk, and regulatory changes, and generate the necessary documentation and product labels for products that will be shipped internationally.
It’s not shocking that investors have taken note of a company like this — its product is addressing a specific pain point for many businesses where AI should be able to help. What it’s building: Satellites that can safely return products manufactured in space back to Earth Why it’s a fav : Space, due to microgravity and a near-perfect vacuum, is a great environment for manufacturing certain pharmaceuticals, semiconductors, and 3D-printed human tissues and organs. Manufacturing in space could be the future, and Dispatch wants to be a part of it by developing vehicles that can withstand the heat and return those products back to Earth.
Unlike many space capsules that burn up or are discarded after one use, Dispatch is designing its vehicles to be refurbished and sent back up to space over and over. VCs are betting that space manufacturing is closer than we think, and there could be great value in handling the transportation of those products. What it’s building: A tool that lets non-engineers ship and build features without writing code Why it’s a fav: Lightsprint lets anyone, whether they have coding experience or not, build and ship production features for applications.
In the past, if a change needed to be made in an application, a product manager had to wait for an engineer to fix it. But Lightsprint hopes to be the tool that product managers use directly instead. Users explain what they want fixed or adjusted, then pick from visual options of how they want the changes to appear, and a Lightsprint AI agent will build it for them.
After the product manager is satisfied, an engineer reviews, approves, and merges the new code into the existing code, and then the company can officially ship the new feature. What it’s building: A tool that automates website building and marketing growth Why it’s a fav : Our sources weren’t kidding that Ploy is hot. Shortly after we added the company to our list, Ploy announced a healthy $27 million seed round led by First Round and Y Combinator.
The draw? Ploy is founded by Bryant Chou, co-founder and former CTO of Webflow, a drag-and-drop website builder last valued at $4 billion. Ploy takes website creation much further by automatically generating landing pages, writing marketing copy, and launching campaigns.
The startup’s AI agents continuously refine website content with an eye on accelerating inbound growth. In this way, the startup promises to eliminate the need for a large marketing team. What it’s building: An AI-powered platform to find and generate fixes for software problems Why it’s a fav: Sazabi was founded by Sherwood Callaway, a repeat YC founder, with a résumé that also includes being an a16z scout, an employee at Brex and at 11x.
Those types of experiences alone make him an investor darling. But VCs are also intrigued by the product, a tool that helps find and flag problems in software production systems. Sazabi integrates with Slack to communicate with teams via that chat app.
It performs log analysis (the script the software writes while it’s running) to help determine why something broke in production, and lets users tell it to generate and submit a fix for the problem in one click. What it’s building: AI security infrastructure Why it’s a fav : Autonomy is a hot space right now for investors, as they fund countless companies putting AI agents to work on important parts of the business. Silmaril is working to ensure that agents can’t be hacked via “prompt injection” — meaning that the agent’s public-facing parts can’t be manipulated by hackers via prompts, emails, or other documents.
Silmaril’s agents autonomously probe for new threats to agents and applications, and once they find a threat, they autonomously retrain the firewall to develop immunity to it. What it’s building: A platform that lets developers run at least 100 coding agents simultaneously Why it’s a fav: Coding agents have fully invaded the software development world. As they proliferate, there needs to be a way to manage them in one space.
That’s what Superset is seeking to do. Its tool allows developers to launch 100 or more coding agents at once and manage them. Any command-line interface (CLI) agent — like Claude or Cursor — can run on the platform, and each agent runs in its own little workspace, so there are no conflicts between them.
The tool can also be opened in any integrated development environment (IDE) such as VS Code or Cursor. What it’s building: A task-performing AI agent Why it’s a fav : The company’s premise is simple but it has the potential to be incredibly effective. Tasklet is an AI agent that connects to various work applications’ APIs like Slack, Outlook, Google Drive, and others.
Users can then tell it to perform tasks involving these apps using natural language. A user can ask it to automatically handle workflows and perform tasks, such as sorting emails or pulling reports. It also runs continuously, meaning that even if the user closes a tab, the agent will continue to work.
It can write and run its own code as well as build interfaces. Though some investors have noted they are moving away from investing in horizontal tools like this, it seems Tasklet is running against the grain. It positions itself as a place users go to give commands rather than opening applications up individually.
There is a future, perhaps, in which this becomes a default way that some will interact with software. Why this matters: The YC Demo Day startups reveal a clear trend towards AI-driven solutions for complex problems across industries. From AI-powered counter-drone systems to task-performing AI agents, these startups are tackling specific pain points with innovative approaches.
For developers and businesses, this means access to cutting-edge tools that can streamline processes, improve efficiency, and drive growth. For consumers, it could mean more personalized and efficient services. However, as these startups continue to grow and scale, questions around AI safety, security, and regulation will need to be addressed.
The investments pouring into these companies also raise questions about the potential for consolidation and the emergence of new industry leaders. As the AI landscape continues to evolve, one thing is clear: these startups are at the forefront of shaping the future of technology.
