From Idea to $650M Exit: Lessons in Building AI Startups

Jake Heller is the co-founder & CEO of Casetext, the AI legal startup behind CoCounsel, which was acquired by Thomson Reuters for $650 million.In his talk at AI Startup School on June 17th, 2025, he shared how his team did it—from picking the right idea to building AI products that actually work—and how founders can turn a cool demo into a reliable tool used by real customers.

Nearly every modern AI model, from ChatGPT and Claude to Gemini and Grok, is built on the same foundation: the Transformer.In this video, YC's Ankit Gupta traces how AI learned to understand language — from early RNNs and LSTMs to attention mechanisms and the breakthrough 2017 paper Attention Is All You Need — the discovery that unlocked the modern AI era.

Every founder faces moments where they’re not sure what to do next — such as how to go to market with AI products, when to pivot, and who/when to hire.In this episode of Office Hours, YC partners Pete Koomen, Brad Flora, Nicolas Dessaigne, and Gustaf Alströmer answer real questions from founders and share stories about how great teams build conviction, learn faster, and make better decisions as they grow.

For years, we've heard two major narratives about AI. One predicting the end of human work, the other dismissing it as hype. The truth is more nuanced, and more hopeful.From radiology to software engineering, the pattern repeats: as technology makes tasks cheaper and faster, demand for human creativity and judgment grows.YC's Garry Tan explores what history, economics, and real companies show us— that technology doesn't replace people, it redefines what we can do.

Karri Saarinen is the co-founder and CEO of Linear, the issue tracking tool used by thousands of high-growth companies. Before Linear, he was the first designer at Coinbase and later a lead designer at Airbnb.On Design Review with YC's Aaron Epstein, Karri shares how his design background shaped Linear’s product philosophy, why quality and craft matter from day one, what founders should look for when hiring, and how AI is changing the way teams build. It’s a deep dive into building products that truly stand out.

Paul Gross and his team at Remora are trying to do something that’s never been done before.They're building mobile carbon capture devices for commercial trucks and trains—capturing CO2 from moving vehicles before it enters the atmosphere, then turning those emissions into revenue by selling it to customers that can turn the liquified CO2 into new products.In this episode of Hard Tech, YC's Gustaf Alströmer visits Remora's headquarters outside Detroit to see how a recent college grad with no engineering background is helping transform the $2 trillion transportation industry.

Jordan Fisher is the co-founder & CEO of Standard AI and now leads an AI alignment research team at Anthropic. In his talk at AI Startup School on June 17th, 2025, he frames the future of startups through questions rather than answers—asking how founders should navigate a world where AGI may be just a few years away.He surfaces the big questions startups should be asking in the age of AGI: Should you even start a company right now? What happens when software becomes commoditized? How do you build trust as teams shrink and AI takes on more responsibility?

Ever wonder what it actually takes to train a frontier AI model?YC General Partner Ankit Gupta sits down with Nick Joseph, Anthropic's Head of Pre-training, to explore the engineering challenges behind training Claude—from managing thousands of GPUs and debugging cursed bugs to balancing compute between pre-training and RL. We cover scaling laws, data strategies, team composition, and why the hardest problems in AI are often infrastructure problems, not ML problems.

We are entering the era of Fintech 3.0. Regulatory clarity, growing consumer adoption, and low-cost chains have paved the way for a golden age of building in crypto — and at YC, Base, and Coinbase we want to fund builders to seize this moment. In this episode of Main Function, YC's Harj Taggar and Base's Jesse Pollak sat down to discuss what kinds of companies they're most excited to see, why this is such an exciting time in crypto, and what the future could look like onchain.More on our latest RFS: https://www.ycombinator.com/blog/build-onchain

For nearly two decades, Box co-founder and CEO Aaron Levie has been at the frontlines of how technology reshapes work—guiding the company through the rise of mobile, the cloud, and now the age of AI.In his fireside with YC General Partner David Lieb at AI Startup School, Aaron reflects on what it means to adapt a company over the long term, the hard lessons of staying relevant across multiple technology waves, and why he believes AI represents the most transformative shift yet.