This study explores the practical application of a chatbot driven in Chinese and Science classes, focusing on cultivating students' metacognitive thinking and guiding students' subject learning.The chatbot embedded prompts are designed to stimulate students' inquiry skills, guide subjective learning, and metacognitive thinking.At the same time, teachers have designed supplementary prompts to provide scaffolding support for students' interactions.This two-tiered design approach ensures that Fairbot can both serve as an effective learning assistant and align with subject-specific teaching frameworks.The study involved 94 fifth-grade primary school students and two teachers, and the data sources included classroom observations, teacher reflections and student feedback.The findings show that Fairbot demonstrates its potential in supporting reflective thinking, teaching guidance, and text comprehension.This study highlights the potential of AI tools in classroom while pointing out the importance of integrating AI capabilities with instructional strategies through collaborative instructional design.