## 1 Introduction  
User-centered design (UCD) is an iterative design approach that places end-users at the core of the development process [1]. Designers traditionally gather user needs, create prototypes, collect feedback, and refine solutions in iterations. While the definition of UCD has shifted since its conception, its philosophy still focuses on incorporating the perspective of the user throughout the design process to understand the cognitive factors present in a given interaction [2]. This design process is often carried out in an iterative fashion, where designers consult with the users between each iteration in the form of a user study until the desired usability objectives are met [3]. During the user study, multiple design decisions are made by interdisciplinary teams to create the final design based on the needs of the user. Building on the iterative nature of UCD, agile methodologies naturally emerged as a way to streamline rapid prototyping and foster continuous user engagement [4]. Tools such as Figma--a cloud-based design tool that facilitates real-time collaboration and rapid prototyping--and Sketch--a vector-based design tool widely used for UI/UX design and prototyping--have democratized this process by offering intuitive platforms to craft high-fidelity prototypes that mimic interactive behaviors and visualize potential designs. Theseadvancements have simplified the design process, making it more accessible to a broader audience and facilitating a more inclusive approach to product development [5]. Generative AI is increasingly integrated into this process, although its adoption varies across contexts. UX professionals use AI primarily for individual tasks like content drafting, with limited team-wide integration or formal policies [6]. Designers' perceptions of AI range from seeing it as a threat to viewing it as a creative partner, with metacognitive skills playing a key role in successful adoption [7]. Tools like PromptInfuser demonstrate how LLMs can accelerate prototyping by binding UI elements to AI-generated content [8]. Meanwhile, multimodal AI systems such as ProtoDreamer bridge physical and digital prototyping, enhancing creativity and iteration speed [9]. In education, text-to-image models support early-stage ideation, encouraging divergent thinking but requiring further refinement by designers [10]. Looking ahead, conceptual frameworks envision AI as an interactive collaborator that dynamically adapts to designer inputs, negotiates ideas, and sustains creative motivation [11]. However, the integration of generative AI through live-prototyping represents a further leap towards democratizing design. This approach not only accelerates feedback loops by enabling real-time modifications during user studies but also embodies a more inclusive design philosophy [12]. By empowering designers to iterate on components instantly based on user input, generative AI in live-prototyping bridges the gap between expert knowledge and user experience, reducing the barrier of entry, which allows diverse perspectives to contribute to the design process. Generative AI's ability to seamlessly integrate into the testing process and the application itself enables functionalities such as dynamic interface adaptation, real-time content generation, and instantaneous feedback analysis [13; 14]. These capabilities closely mirror the traditional Wizard-of-Oz (WOZ) technique, where human operators emulate system responses to test partially implemented components [15]. However, while WOZ simulations are subject to human limitations like response variability, fatigue, and scalability challenges, AI-driven prototyping offers consistent, scalable, and immediate simulations. This technological shift not only addresses the inherent constraints of WOZ but also amplifies the iterative nature of UCD. Our paper aims to explore the potential of generative AI in assisting live-prototyping within user studies.