A six-phase protocol for squeezing real signal out of twelve virtual people — and the honest line about what the cast still can't tell you, and what fifty real humans must.
The cast is a sparring partner, not an oracle. Be honest about what it's good for before you use it. Otherwise you'll mistake a sycophantic LLM for a market.
Each phase has a single question. Each produces a tangible artefact. Each forces you to commit to something you can be wrong about — which is the whole point.
Each phase is around a week of evening sessions. Each requires you to write something down before you start (your pitch, your mock, your objection prompt) — without that, the session generates noise.
"Walk me through the last time the topic of death, inheritance, or who-gets-what came up in your family in any form. What happened, what got said, what got avoided?"
What you're listening for:
Three questions, after the pitch, in this order:
What you're hunting: the first sentence that loses Klaus is different from the one that loses Marcus. The word that triggers Ana Lúcia ("trust"? "offshore"? "structure"?) tells you about brand language. The promise the Yoons don't believe tells you which proof points you need.
Three questions per screen, no more:
What you're hunting: mental-model collisions across the cast. Marcus wants a manual; Patricia wants a counsellor — does your UI try to be both? Wei wants speed; Klaus wants completeness — does your default mode match either? Khalid wants discretion; Ana Lúcia wants warmth — can the same interface deliver both?
The two-round protocol:
The cold round captures raw reaction. The hot round captures dynamics — disagreement, deflection, where one persona's word makes another go quiet. You moderate; you can call on the quieter voice; you can cut off the dominator.
"For this conversation, set aside being polite. You will not hurt my feelings. The most useful thing you can do is give me the sharpest objection you have. If you'd never use this, say so and tell me exactly why."
What you build from this: the sales-objection catalogue you'd otherwise compile bleeding in real sales calls over six months. Patricia's "I want a human" objection is different from Marcus's "show me the failure mode" objection is different from Khalid's "discretion" objection. Catalog each. Pre-build the response. Test the response on the next persona.
The handoff to each cofounder:
Why this matters: the output of Phases 1–5 is what people would buy if you could sell anything; the council output is what you can actually sell. Skip this phase and you'll ship something that becomes a state-bar disciplinary complaint or a breach response or both.
Each group is composed to make disagreement productive. You don't put four similar personas together to confirm; you put three or four different ones together to argue.
Without these, the cast will helpfully agree with everything you say, give you confidence, and teach you nothing.
Almost every founder using LLMs as research subjects falls into at least one of these. Watch your own felt-sense in the session: if you keep feeling good, something is wrong.
This protocol will produce a pitch you'd be embarrassed by today, a wireframe markedly better than what you'd ship now, and a sales-objection catalogue with thirty to fifty entries. That is enormous value for three to four weeks of work.
It will not tell you that there's a market. Twelve souls in your laptop cannot tell you that. After this protocol, you go book thirty to fifty real conversations — preferably skewed toward people whose financial and family situations match your sharpest synthetic profiles.
The virtual cast tells you which thirty humans to find and what to ask them. That, in the end, is what it's for.