<![CDATA[The urgency of this study lies in the need for an innovative and feasible Project-Based Learning (PjBL)-based electronic portfolio assessment that can authentically measure students’ creative thinking skills in understanding the abstract and complex concepts of chemical bonding. Creative thinking is a core dimension of Higher Order Thinking Skills (HOTS) that remains difficult to cultivate in chemistry instruction, particularly on the abstract topic of chemical bonding, where conventional written assessments have yet to accommodate authentic, process-based evaluation of students' creative thinking. This study employed a Research and Development (R&D) approach based on the 4D model, limited to the define, design, and develop stages, to develop and test the feasibility (validity and reliability) of a Project-Based Learning (PjBL)-based electronic portfolio assessment instrument for evaluating students' creative thinking skills in chemical bonding. Content validity was examined through expert judgment involving five validators, comprising three chemistry education lecturers and two chemistry teachers, using the Content Validity Ratio (CVR), while inter-rater reliability was examined through the Intraclass Correlation Coefficient (ICC) Two-Way Mixed-Effects Model of Consistency involving five raters who scored the work of 19 students selected through total sampling. The results show that the PjBL-based electronic portfolio assessment instrument possesses highly adequate quality, with a perfect CVR value of 1.00 (Valid) for all task items. Furthermore, the inter-rater reliability test showed consistent stability, with ICC values ranging from 0.949-0.981 (excellent) for Task 1 (Open-Ended Essay), 0.866-0.942 (good to excellent) for Task 2 (Concept Map), and 0.850-0.936 (good to excellent) for Task 3 (Digital Poster). The resulting instrument offers teachers a systematic and objective alternative for assessing creative thinking through project-based tasks, encourages students' active engagement and self-reflection through digital portfolios, and provides a validated reference for future development of technology-based authentic assessment in science education.]]>
