The argument
What Lean was rationing, what survived, and where the scarcity went.
Reserve your copy · Coming Holiday Season 2026
TheMaximumViableProduct
How AI Killed the Lean Startup — and What Comes Next
01 The old constraint
Lean Startup was a rationing system.
Every practice protected the scarcest thing in the company: engineering hours. Estimation rationed them. The MVP rationed them. Build-Measure-Learn spent them one careful turn at a time.
Reserve your copy02 The changed constraint
The ration
ended.
Building got cheap. The habits did not notice.
A methodology whose constraint has died keeps running its practices as superstitions. The discipline survives by asking what is scarce now.
Reserve your copy03 The next discipline
Build the whole thing.
Learn at full speed.
Stop rationing the build. Start rationing your attention. The one thing still scarce is where you look.
Reserve your copy Follow the argument| The 2011 rule | The premise that broke | The 2026 replacement |
|---|---|---|
| The 2011 ruleMVP — build the least you can learn from | The premise that brokeBuild hours were the scarcest spend | The 2026 replacementBuild the whole thing; ration exposure, not ambition. |
| The 2011 ruleFive Whys | The premise that brokeRoot cause was a meeting culture | The 2026 replacementKept — and mechanized. |
| The 2011 ruleEngines of growth — will anyone pay? | The premise that broke(nothing broke) | The 2026 replacementNot replaced. |
Inside the book
An argument to read.
A discipline to use.
Fifteen serialized pieces, then an expanded manuscript in three parts.
The author
Daniel
Willoughby.
An operator writing from a logged record.
Daniel Willoughby has founded and operated five consumer brands. He was employee #1 at Dandy, scaled it through acquisition, and became CEO after the acquisition. For one brand he drove 30M+ organic TikTok impressions in under 90 days.
Today he is CEO of Jinn, the operating system for brands: it knows a brand, acts for it, and learns from what lands. His daily practices building Jinn, and his team's, supply the book's replacement column. Every replacement is a practice they run, most forced by a specific logged failure.
Meet the authorWho is it for?
You’re a founder or operator who learned Lean. You now build with AI. Keep the discipline. Change the practices whose constraint has gone. Start with Part II for the operating changes. Come back to the argument when you need it.
What is this book?
A way to decide what to keep, change, and stop doing when you build with AI. Lean Startup’s practices were built around expensive engineering. That constraint is gone. This book re-derives each practice. Dan is writing it to inspire the next generation of entrepreneurs the way The Lean Startup did for his. Fifteen serialized pieces come first, followed by an expanded manuscript.
When is it out?
The book lands Holiday Season 2026. You can start reading before the finished book arrives. Pieces publish on Substack first, as the book is written.
Is it written by AI?
The writing is Dan’s. In the spirit of the book, AI was used for pieces of the creation: research, editing, and pulling evidence from his work inside Jinn. Every replacement in the table is a practice his operation runs.
Why write it in public?
Read the argument while the book takes shape. The book argues for shipping whole things to a rationed audience. Publishing complete pieces first is that practice applied to the book itself.
What formats will be available?
All traditional and digital formats will be available. Reserve now and you hear first when pre-orders open. No payment is taken.
How much will it cost?
The book’s price is not set. You can reserve now. Reserving costs nothing.
What is in the free kit?
Five worksheets, a 20-question audit, and the Replacement Table. Use them in your next plan. Free, with your email.