Definition
The evidence standard that decides what you may commit to next
Stage-matched proof is the test that separates a company that is early from a company that is over-committed.
Every company holds some evidence. The question that changes decisions is whether that evidence is strong enough for the specific commitment being considered. Stage-matched proof turns that question into something a founder, an investor and a board can answer in the same words.
Direct answer
What is stage-matched proof?
Stage-matched proof is external behaviour strong enough to justify the next irreversible decision at the company's current stage.
Deeper explanation
What it proves
- That someone outside the company changed their behaviour
- That the behaviour is strong enough for this specific decision
- That the decision is being taken at the right point in the sequence
What it does not prove
- That the behaviour will repeat at volume
- That the buyer will stay
- That the same evidence supports a larger or later decision
- That the company is ready for the stage after this one
Common false signals
- Enthusiasm without commitment: praise, interest, intent to buy
- Signals produced by the company rather than by the market
- One exceptional customer generalised into a pattern
- Evidence borrowed from an adjacent segment or geography
- Proof that was true before a material change in product, price or buyer
Founder implications
- Before a commitment, you state the decision and the evidence in the same sentence.
- You stop reporting effort as if it were evidence.
- You are allowed to say the evidence is not there yet, which is the cheapest thing you can do.
Investor implications
- You ask what external behaviour supports the specific use of funds.
- You separate a strong team with weak evidence from a weak team with strong evidence.
- You avoid funding a stage the company has not entered.
Board implications
- You require the evidence standard before the decision, not after it.
- You ask what would have to be true for this proof to be wrong.
- You record the evidence that a decision was based on.
Why external behaviour, and not internal conviction
Internal conviction is required to build anything, and it is a poor evidence source, because it is available in unlimited quantity and costs nothing to produce. External behaviour such as signature, payment, renewal, referral, integration or repeat use costs someone else something.
How to apply the test in a single meeting
- Name the decision, and say what makes it hard to reverse.
- Name the external behaviour that supports it.
- Say who behaved that way, how often, and how recently.
- State what would falsify the proof.
- Decide, postpone, or name the missing evidence.
Where this sits in the book and the OS ebooks
More Scars Than Trophies explains stage-matched proof as theory: why the distinction exists and how it changes judgement. The Proof Stack OS ebooks turn it into operating practice, and each OS ebook has its own separate role-specific AI chatbot.
- Proof Stack Daily OS: The founder's operating system for turning proof into daily decisions.
- Proof Stack Company OS: The company and board operating system for evidence-based governance.
- Proof Stack Investor OS: The angel investor's operating system for evidence-based startup decisions.
Evidence boundaries
What this page does not claim
The limits of the model are stated on the page, not buried in a footnote.
- Stage-matched proof is a threshold test, not a score. There is no numeric rating in the model.
- External behaviour can be misread. The model reduces error; it does not remove it.
- The test says nothing about whether a decision is strategically wise once the threshold is met.
Audience implications
What changes for each reader
The same evidence standard, read from three different seats.
Founders
- Before a commitment, you state the decision and the evidence in the same sentence.
- You stop reporting effort as if it were evidence.
- You are allowed to say the evidence is not there yet, which is the cheapest thing you can do.
Investors
- You ask what external behaviour supports the specific use of funds.
- You separate a strong team with weak evidence from a weak team with strong evidence.
- You avoid funding a stage the company has not entered.
Boards
- You require the evidence standard before the decision, not after it.
- You ask what would have to be true for this proof to be wrong.
- You record the evidence that a decision was based on.
Author
Petri Lehmuskoski
Petri Lehmuskoski has founded, scaled, repaired and exited companies over more than four decades. He is Founding & General Partner of Gorilla Capital.
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Related
Continue through the model
- The Proof Stack
The Proof Stack is an ordered model of the evidence a company must hold before a decision that is difficult to reverse: a Discovery stage followed by four Proof layers (Buyer Proof, Value Proof, Scaling Proof and Exit Proof).
- Irreversible decisions
An irreversible decision is a commitment that cannot be undone cheaply or quickly, because reversing it costs capital, time, credibility, relationships or options the company cannot replace.
- Evidence versus activity
Evidence is a change in external behaviour caused by the company's work; activity is the work itself, and no amount of it substitutes for evidence.
A plain-text version of this evidence layer, generated from the same page content, is available at /concepts.md.
Read the chapter that starts the argument
Chapter 1: Most Founders Do Not Fail Because They Make Bad Decisions. Free to read now, no email required.