Out now, on Amazon & Kindle
AI can build anything. It can’t tell you what to build.
The field guide to product-market fit when anyone can ship. Read what customers do, not what they say.
Paperback and Kindle · By Boris Manhart
“Makes you nervous, in the best way. Surgical about the excuses founders hide behind.”
“Tells founders what to do on Monday morning. Read it with a pen.”
“Building was never the hard part. This teaches the real craft.”
“If you’re building with AI and speed alone isn’t enough, this is the book.”
When AI builds anything, the human signal becomes the moat.
The barrier to building has collapsed. The barrier to winning has not. What still separates the products that make it is the ability to read genuine demand through the noise, and to act on it before you lose years learning it the hard way.
- InterestSign-ups, replies, meetings
- EngagementComes back, uses it
- CommitmentPays, signs, refers
- RecurrenceKeeps paying
Every layer is behaviour, not opinion. Fit shows at the bottom.
Read the signal
Tell a polite compliment apart from a genuine buying signal. Behaviour over opinion, every time.
Two frameworks
The PMF Flywheel maps the search; the Signal Stack tells real demand from noise across three layers.
Find and defend fit
Read fit from what customers actually do, not from vanity metrics, then build the advantage a well-funded rival can’t copy in a year.
From a vague idea to fit you can prove.
Choose the market
The one with the fastest learning, not the biggest TAM.
Find the real problem
Deep enough to earn the right to build. Workarounds, not opinions.
Sharpen the value
Why you, and not the status quo. Basics, performance, delight.
Test demand
A commitment that costs something: money, a slot, a paid pilot.
Build with AI
Ship an artifact, get behavioural signal within 72 hours.
Defend it
What a well-funded competitor could not copy in twelve months.
How strong is your PMF signal?
Nine honest questions, three minutes, a straight score with a concrete recommendation on where to start. Built on the method from the book. No login, your result stays in your browser.
Every tool from the book. Free.
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7 worksheets, free, no upsell
Get the tools by email
One email, no password. The same address subscribes you to the free weekly News on Substack (you confirm once by email). We send you a link that unlocks every worksheet.
Find fit in 8 weeks, live and guided.
Eight weekly live sessions, a private cohort, and full access to the PMF App. Led by Boris Manhart and Marc Pittner.
8 weekly live sessions
90 minutes each, one per station of the Flywheel.
Private Slack
Ask Boris and your peers between sessions.
The PMF App
Score, build and experiment, all in one place.
Early Bird until 30 November
CHF 1'290once
Founding Cohort price.
Founding Cohort · January 2027 · Max. 10 founders
- 8 weekly live group sessions
- Maximum 10 founders
- Direct feedback from Boris & Marc
- Full PMF Mastery platform
- AI tools, templates and experiments
- 12 months platform access
No payment today. We’ll confirm your seat first.
“Reading this in the context of having been in the venture business for 35 plus years, it reminds me as an investor we rarely make as much of a difference as we’d like to think. What’s more, and even less flattering, we mostly know what to do and what works, yet our biases and ego get in the way. Conflating need for demand with no effective way to separate opinion from fact, we end up adding more capital as that’s easier than answering the hard questions. Boris is pointing explicitly at the true-north with start-ups: it’s hard, takes a long time, sometimes it works. While actual outcomes are more random than we’d like, this ‘manifesto’ provides insight on how to remain aspirational with required humility. While helpful for founders, I think it’s an even more important read for investors. Excellent.”
The two people behind it.
Behind Human Signal is Growth Unltd., a two-person team that has built and scaled companies, not just advised them.
Boris Manhart
Author, Leadership & PMF
5 companies · 1 unicorn · 30+ teams a year
Two decades building and scaling digital ventures. Founded five companies, co-founded the unicorn Numbrs, led CodeCheck to millions of users. Innosuisse Expert Coach and startup strategist at IMD, sees 30+ founder teams a year.
Marc Pittner
Build with AI & Delivery
Adtech exit · Silicon Valley · Head of Digital Sales, largest Swiss telco
Serial entrepreneur. Built and exited an adtech company, spent time in Silicon Valley and has shipped platforms inside large organisations for years, today as Head of Digital Sales at Switzerland’s largest telco. Turns strategy into working product, pragmatic and hands-on. In PMF Mastery he leads Build with AI and running experiments.
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