A team has a prototype that every tester navigates without help, and engineering has costed the build and signed it off. Nobody on the team can point to evidence that a person outside the company wants the thing. Which of Cagan's two discovery findings is still open?

The principle — the two findings fail independently, and a team is usually strongest on the one it can see.

Why the key is correct — Cagan's first finding is that First, you need to discover whether there are real users out there that want this product. A prototype and an engineering sign-off both belong to the second finding: Second, you need to discover a product solution to this problem that is usable, useful, and feasible. Every piece of evidence the team holds is about the solution. None of it is about demand, so the first finding is untouched.

Why the others are wrong — a prototype people navigate easily is evidence of usability, and reading it as evidence of demand is the substitution the split exists to prevent. Feasibility has in fact been addressed here, so naming it as the gap misreads the scenario. And treating a completed round of interviews as the finish line confuses an activity with a finding.

Remember this — a team can be finished with the solution and have never asked whether anyone wants it.

Sources — Marty Cagan on product discovery, Silicon Valley Product Group.