Abstract
The traditional SaaS model, centered on human-operated dashboards, is being supplanted by Agents-as-a-Service (AaaS), where autonomous agents orchestrate outcomes. This article explores the architectural shift from request-response to reason-act loops, a reference "Agentic Stack," the rise of Agent-to-Agent (A2A) communication, and the implications for business models and system design, emphasizing the transition from User Experience (UX) to Agent Experience (AX).