The endorsements about the productivity gains from AI at coding are coming in thick and fast.
Garry Tan, CEO of Y Combinator — the world’s best-known startup accelerator — recently shared a personal story that captures just how dramatically AI has changed what a single person can build. What makes the account particularly striking is who’s telling it: not a wide-eyed newcomer to tech, but a founder, engineer, and investor who has seen multiple generations of software development up close.
“I’m in the middle of a very intense addiction to Claude Code and Codex,” Tan said. “Actually using this stuff is pretty wild. I basically recreated my 2008 startup. It’s like 70,000 lines of code. I did it in about 90 hours over two weeks — because I have a full-time job and I’m also trying to raise kids — but it really compressed a lot of my sleep.”
Tan had co-founded a startup named Posterous in 2008, which was a blogging platform that integrated posting to several social platforms. It was acquired by Twitter in 2012.
“At the end of it, I have a codebase that is better than what it took five engineers and me taking anti-narcoleptics to build for my YC startup. It’s crazy. It’s unbelievable.”
Tan then pointed to a specific moment he believes triggered the shift — the release of Claude Opus 4.5 at the end of November:
“Something happened at the end of November when Opus 4.5 came out. I heard about it and I was like, ‘Hey, what’s going on?’ The most interesting thing for us is that we’d been talking about it for years. We’d been using it for years. And then it wasn’t until really even December where AI is here for code. I feel like I could create in 80 hours something that I could not create with $5 million and five engineers in two years.”
Tan’s comments are the latest in a series of remarkable statements from top tech figures about what vibe coding has unlocked. NVIDIA’s Jensen Huang has said that nothing would give him more joy than if his engineers never had to write code at all. Microsoft CEO Satya Nadella has noted that AI in coding went from being a joke to standard issue in a matter of months. And Naval Ravikant has argued that vibe coding is the new product management — that the line between having an idea and shipping it has effectively collapsed. And CEOs of companies like Shopify and Coinbase are actively vibe-coding and showing off their Github profiles.
What’s significant about Tan’s story specifically is the benchmark he’s using. He isn’t comparing AI to a solo developer tinkering on weekends. He’s comparing it to a funded startup with a full engineering team, running on caffeine and anti-narcoleptics, building for years. If that framing holds up even partially, it has profound implications for how startups are staffed, how venture capital is deployed, and what a small team can realistically accomplish. The question is no longer whether AI can help you code faster — it’s whether the traditional model of building a software company still makes sense at all.