Background: Conventional reflective learning methodologies in programming education often lack structured guidance and individualised feedback, limiting their pedagogical effectiveness. Whilst computational thinking (CT) offers a systematic problem-solving framework with decomposition, pattern recognition, abstraction, and algorithm design, its potential application as a diagnostic instrument for reflection remains insufficiently explored within programming education. Objectives: This study aims to develop and evaluate a CT-based diagnostic reflective report system as a technological intervention to facilitate structured reflective learning in programming education. Furthermore, it investigates the impact of this system on knowledge construction, higher-order thinking skills (HOTS), and project performance within an introductory Python programming course. Methods: The study employed a quasi-experimental design spanning two academic semesters, involving 82 undergraduate students randomly assigned to experimental (n = 42) and control (n = 40) groups. The experimental group utilised weekly CT-based diagnostic reflective reports, whilst the control group engaged in traditional reflective practises. The curriculum integrated Python programming with Raspberry Pi embedded systems. Assessment measures included pre- and post-tests for knowledge construction, a validated questionnaire for HOTS evaluation, and the Creative Product Analysis Matrix (CPAM) for project performance assessment. Results and Conclusions: Implementation of the CT-based diagnostic reflective report system demonstrated statistically significant improvements in knowledge construction, critical thinking, and problem-solving skills compared to traditional approaches. Project performance metrics, including valuable, logical, useful, understandable, and well-crafted, showed marked enhancement. However, no significant impact was observed regarding creativity. These findings substantiate the efficacy of integrating CT diagnostic mechanisms with reflective learning practises.