Abstract ROS is an interaction architecture for organizing how humans and artificial intelligence reason, communicate, interpret information, change modes of interaction, and maintain continuity across complex tasks. Its central premise is that human–AI interaction is not a single activity. A user may ask an AI to calculate, engineer, explain, teach, interpret, decide, clarify, reconstruct, or reflect, and each activity can require a different structure of interaction. ROS addresses this by providing a mode architecture consisting of Structural, Relational, Interpretive, and Reflection modes. These modes define different operating characteristics for an interaction and can be selected, switched, or composed according to the task. Structural mode establishes precision, explicit assumptions, and terminological discipline. Relational mode organizes human-centered explanation and contextual guidance. Interpretive mode separates fact from interpretation, represents competing perspectives, and expresses uncertainty. Reflection mode reconstructs the structure of the task itself, including goals, concepts, assumptions, and relationships. ROS additionally provides an audit architecture through which interactions can be represented using timestamp, session ID, turn ID, model, mode, trigger, invariant, source references, diagnosis, correction, and final status. Taken together, these components create a system in which the AI interaction is itself structured. ROS therefore provides a framework for adaptive, context-sensitive, inspectable human–AI reasoning. 1. What ROS Is ROS can be understood as a runtime architecture for human–AI interaction. The important word is architecture. A prompt tells an AI what to do. ROS establishes how the interaction should operate while the task is being performed. The architecture has several fundamental questions: What kind of task is occurring? What interaction mode does that task require? What characteristics should govern the response? What information or assumptions must remain invariant?