Two years ago, Replit CEO Amjad Masad invited Paul Graham, the legendary cofounder of the startup incubator Y Combinator, to his home office near Palo Alto, California, to give Graham a sneak peek of Replit’s new and novel product: an AI agent that could write its own code. It was the first time Graham had seen what would become known as vibe coding. “The name hadn’t even been invented,” Graham recalls.

As the agent got to work building apps, Graham, a lifelong computer programmer, instinctively looked at the code. Masad scolded him, saying there was no need, arguing that the source code would only be an unimportant byproduct, and programming would now be done in English — a radical change for software engineers. “It was mind-bending,” Graham, one of Replit’s earliest investors, tells Forbes. “He’s bald with that beard, and I think he was actually wearing a black turtleneck. I felt like he was a Bond villain: ‘Hahaha! Don’t look at that code!’”

Now vibe coding, of course, is everywhere, and Replit is looking to take it a step further. On Wednesday, the startup announced its new agent, simply called Agent 4, which aims to deliver a new type of interface for vibe coding. Like last time, Masad demoed the new agent to Graham at his home office in early March. After the meeting, Graham gushed about the product on X. “Amjad showed me Replit's latest stuff,” he posted. “They're about to redefine vibe coding in a way that will seem obvious in retrospect. A lot of the biggest ideas have that quality.”

Instead of just typing in prompts to instruct the agent on what to code, Replit offers what it calls a digital canvas, where users can tweak mockups and app designs, doodle drawings of new features, and collaborate with other developers in real time. “It’s about designing together with the agent,” says Masad, with the goal of replicating the experience of brainstorming and building in real life. “When I walk around the office, when I see designers working with engineers, they're on the whiteboard, they're drawing, they're doing that sort of stuff.”

The takeaway, Graham tells Forbes now: “He keeps taking me around the back of his house and showing me the future.”

To jumpstart that quest for the future, Replit — which wouldn’t comment on revenues except to say it’s on track to hit annual recurring revenue of $1 billion by the end of the........

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