Current literature that aims to describe the use of (Gen)AI in the domain of design is hindered by the lack of conceptual integration of design theories which in turn blurs the connection between the design process and human-AI interaction and collaboration frameworks. This thesis’ objective is to contribute to the conceptual understanding of LLM-based design process augmentation. This thesis shows how such LLM-based design process augmentation can look like by establishing 1) a time-based framework of a human – Augmentation-System collaborative design process, 2) a perspective on the design process augmentation capabilities of LLMs, and 3) an augmentation system architecture and interface for the practical implementation of these theoretical considerations. Other contributions that have enabled these three main contributions include 1) the unification of existing design theories (problem-solution co-evolution, situated Function-Behavior-Structure (FBS) framework, Concept-Knowledge theory, and Uncertainty Driven Action (UDA) model) to attend to a wider range of person-related characteristics required for the description of a collaborative process of design, 2) the connection between human intellect augmentation and creativity literature, resulting in 3) the application of creativity literature in the domain of GenAI and specifically LLMs, and 4) the application of the layers of behavior as described in the UDA (Uncertainty Driven Action) model for the creation of a computational augmentation system. Finally, a reflection on the feasibility and desirability of different forms and applications of augmentation systems is provided. The results of this thesis have created a fundament for further research into the direction of the initial objective, as the results have increased the conceptual power to describe and explain process, output, and other augmentation-related phenomena connected to the domain of human-LLM (or GenAI) co-design.