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Futures · Explore

Assumption stress test

Takes the most ambitious option on the table and asks what would have to be true for it to work. Not a risk exercise — a way of finding out whether the upside case is even coherent.

The printable canvas and the handoff into Claude Code are part of a paid plan. See what a plan includes. It needs the Claude desktop app on this machine, and your team and the prompt library already installed in that project — we cannot see your disk, so open it there.

Stage
02 Explore
Works at
All levels
Maturity
Any
Time
Ninety minutes

What it is

A structured examination of what would have to be true for an ambitious option to deliver its projected outcome. It is the optimistic mirror of a pre-mortem: rather than asking how something fails, it asks what the world must look like for it to succeed, and whether that world is plausible.

The claim
The ambitious outcome, stated with a number and a date. Everything else tests this one statement.
Necessary conditions
What must hold for the claim to be true — about demand, competition, cost, capability, timing and capital. Typically eight to twelve.
Plausibility
How likely each condition is on current evidence. Assessed independently of how much you want the option to work.
Controllability
Whether each condition is something you influence or something you are betting on. A case resting mostly on the second kind is a wager.
Compounded probability
The conditions multiplied. This is where most optimistic cases fall apart, because each condition looked reasonable on its own.
The load-bearing condition
The single assumption doing most of the work. Identifying it tells you what to test first and cheapest.
The mistake people makeRating conditions individually and never multiplying them is how confident plans get built out of a chain of reasonable-sounding assumptions. Compound them explicitly — the arithmetic is the argument.
What it’s forYou want to know what would have to be true for the ambitious option to work.
What it’s not forYou need to reduce risk, not size opportunity. Use a pre-mortem instead.

How you run it

  1. State the ambitious outcome preciselyWith a number and a date. "It could be transformational" cannot be stress tested.
  2. Work backwards to the necessary conditionsWhat must be true about customers, competitors, costs, capacity and timing for that number to happen? Aim for eight to twelve conditions.
  3. Rate each on plausibility, not desirabilityHow likely is this, judged from evidence rather than hope? Mark which are within your control and which are not.
  4. Multiply the independent onesFour conditions each at 70 per cent gives you a 24 per cent case. Teams reliably assess conditions individually and never compound them.
  5. Find the load-bearing oneThere is usually a single condition the whole case rests on. Test that one first, cheaply, before committing to anything else.

The prompt

Two ways to run it

Run this tool in your own Claude

The short prompt starts your partner against the library on your disk. The long one carries everything with it and needs nothing installed.

🔒 Prompt locked

Everything above is free — what this tool is, what it is for, what it is not for, and how to run it as a workshop. Three tool prompts a month are free with an account; beyond three, and for the printable canvas, it is the paid part.

See plans — from £19 a month

Your playbook

It lands in the earliest stage this tool suits. Move it on the Playbook page.

You’ll need

  • A specific ambitious option, with its projected outcome
  • The model or logic behind that projection
  • People willing to state numbers out loud

You’ll end up with

  • The conditions the case depends on, listed
  • Each rated for how plausible it is
  • The one or two that carry the whole case

Runs well with

Acquisition screen and synergy thesisAdjacency mapAnalysis planAnsoff matrix