Psychological assessment has spent a century refining a single architecture. A person sits down once, completes an instrument built for everyone, and receives a score positioned against a population mean. I designed ATLAS, the Agentic Digital Twin-Led Assessment System, to change the order of inference. The model of the person is built first, the assessment content is generated from that model, and the evaluation is performed by a population of reasoning agents whose disagreement is preserved rather than averaged away. ATLAS is a conceptual architecture and a falsifiable design proposal, not a validated product.