AI collapsed the cost of building. A founder with no engineering background can ship working software this week — which means building was never the moat. The scarce edge now is knowing what’s worth building, and accumulating evidence a competitor can’t copy.

This playbook re-grounds the startup journey for that world. It walks the three stages every founder moves through — Business Model Design, Problem/Solution Fit, and Product/Market Fit — and shows what changes when AI is doing the work alongside you.

At each stage you get the goal, the riskiest assumptions to retire, the exit criteria, the new AI-era traps to avoid, and a set of hands-on exercises — each with a short thing to type into LEANSpark and a full prompt you can hand to any AI assistant.

It’s the same job it always was: find a problem worth solving, build a solution worth paying for, and turn it into a company that lasts. The rules just tightened where the constraints loosened. This is how to run lean when anyone can build anything.

What's inside

Why building is no longer the moat — and what is

Stage 1 · Business Model Design — get your idea onto one page and find its riskiest assumption

Stage 2 · Problem/Solution Fit — prove the problem is real and that someone will commit

Stage 3 · Product/Market Fit — turn early commitments into a repeatable Customer Factory

What to type into LEANSpark at every step — plus a full prompt for any AI assistant

Running Lean: The AI-Native Founder's Playbook

What's inside