A model of the visit.
Some people scan a screen and leave. Some read the proof. Some arrive from an ad already checking the promise. Those differences are the model, not a name swapped into a prompt.
A live URL, a variant, or a mockup nobody has shipped. Set the goal (a trial, a demo, the click) and let it go. Original, variant, and mockup can share one run. You do not need a live experiment first.
What are you testing?
Candidates
AOriginal
acme.com/
BVariant 1
Outcome-led headline
CMockup
pricing-first.png
Goal
Metric
Not one average person. A paid click, a skimmer, a researcher, someone coming back. They do not want the same page. Patience, reading depth, and intent change what each of them reaches.
Every result is marked predicted, so it cannot be mistaken for the test. Skimmers never reached the button on A. Researchers still wanted A. That split is the experiment.
Homepage hero test
40 simulated visits · Goal: Start a free trial
Candidate B · journeys
Desktop
Simulated trial starts
By visitor type
B repeats the ad's promise, so it stayed past the hero.
Engaged: Hero headline · On A, 3 of 5 left at the hero
B's trial button is on the first screen. On A it's two scrolls down.
Engaged: Primary button · On A, stopped scrolling before the CTA
Wanted pricing and proof before a CTA. B asked too early.
Engaged: Pricing and logos · On B, left from the pricing table
Found the trial button on both. B was one click faster.
Engaged: Primary button · No drop-off on either
Simulation isn't the result. It drafts the test, attaches the notes, and leaves the launch with you. The draft keeps the variants, the goal, and what each visitor did. You review it. Real visitors decide.
Simulation
Homepage hero test
Homepage hero test
DraftA/B test · acme.com/
One page, one goal, a review when it's done. Run a simulation when you have a specific question, not a pile of ideas.
Hero test
The homepage you have, next to a new first screen. See whether a paid click stays through the fold.
Offer check
Same page, different goal. See which ask each visitor type actually reaches.
Ad match
A paid-ad visitor is checking that promise. If the hero says something else, they leave at the top.
Pricing pass
Some visitors look for the price. Others never scroll that far. You see which type stops, and on which version.
Some people scan a screen and leave. Some read the proof. Some arrive from an ad already checking the promise. Those differences are the model, not a name swapped into a prompt.
Which version each type preferred, why, and where they stopped. When they disagree, that is the brief for the experiment.
The useful finding in the public work is that a grounded agent beats a demographic sketch, and that simulation is an intervention you can replay, not a story about what is likely. That work is Stanford's generative-agent papers, and Simile, the company built from them.
We do not claim their numbers. The 85% result is agreement with a person's own survey retest, on agents built from long interviews. A page rehearsal earns its own, against live experiments.
Start with the page you already have. One goal. Who stayed and who left, then a draft experiment you still launch yourself.
Questions, enterprise, or a walkthrough: we'll reply shortly.