UX validation traditionally depends on real users. Interviews, usability testing, and quantitative data allow us to observe authentic behaviors and make informed decisions. However, in early design stages or rapid iteration cycles, it is not always feasible to rely immediately on formal research.
In this context, a structural tension emerges. We need to stress-test design decisions before investing in formal validation, yet we lack an intermediate instrument that allows us to do so in a rigorous and reproducible way.
Traditional personas describe user profiles, but they do not execute decisions. Language models can simulate interaction, but they tend to optimize the flow, fill design gaps, or rely on undeclared knowledge.
The issue is not the absence of simulation. It is the absence of controlled simulation.
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This document defines a framework for building and using synthetic users as decision agents operating under explicit rules and clearly defined constraints, with the goal of revealing structural friction before exposing the system to real users.
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A UX persona is a descriptive artifact. It summarizes context, motivations, and characteristics of a typical user. Its purpose is to guide design discussions.
A synthetic user does not describe. It executes.
The difference is methodological. A descriptive artifact does not make decisions within a workflow. An executable agent does.
A synthetic user does not attempt to predict human behavior or represent a population. It does not generate empirical evidence. Its function is to simulate decision-making under controlled conditions in order to expose how a system behaves when interpreted by an agent with defined limits.
It does not simulate humanity. It simulates interpretation and cognitive friction.
A synthetic user is an artificial decision agent constructed through an explicit objective, behavioral rules, defined constraints, and forbidden assumptions, designed to interact with a digital system under controlled conditions and without external compensation.
Each component is essential: