We present AutoPBL, an LLM-powered self project-based learning (SPBL) platform that guides and supports learners in learning through projects. SPBL combines project-based learning's benefit of being engaging and effective with the flexibility of self-learning, leading to its popularity. However, insufficient guidance and support during SPBL may lead to unsatisfactory learning experiences and outcomes. While LLM chatbots (e.g., ChatGPT) could potentially serve as SPBL tutors, we have yet to see an SPBL platform with responsible and systematic LLM integration. To address this gap, we examined human PBL tutors' role through formative interviews to inform our design of AutoPBL. AutoPBL features an LLM-guided learning process with checkpoint questions and in-context QA with an integrated LLM tutor. In a user study where 29 beginners learned machine learning through entry-level projects, we found that AutoPBL effectively improves learning outcomes and elicits better learning behavior and metacognition by clarifying current priorities and providing timely assistance.
