Vibe Design: Human-in-the-loop AI Agents for UI Design with Large Language Models

New tectonic shifts are looming in the UI design process due to advances in LLMs. These shifts have led researchers to adopt LLM-based approaches to develop design systems. However, such systems often focus on narrow functions and rely on code-based data that limits real-world applicability. We propose Vibe Design, an agentic framework that enables designers to co-create and evaluate prototypes with the LLM-based agents. The framework consists of a design agent that supports UI creation and a user testing agent that generates usability feedback through simulated user interviews, guided by the Persona-Scenario-Goal methodology. We also incorporated a human-in-the-loop mechanism to enhance the reliability and quality of the LLM-generated responses. We successfully generated functional prototypes and extracted user requirements from diverse personas. This study provides insights into the use of LLMs for both UI generation and user feedback collection, offering practical implications for future design workflows.