The goal of this clinical trial is to learn if an AI-enabled stratified management system (SMART-CHD) can improve post-discharge outcomes in adults aged 18-45 with premature coronary artery disease. The main questions it aims to answer are: 1. Does SMART-CHD reduce the combined rate of all-cause death, myocardial infarction, stroke and rehospitalization within 12 months? 2. Does SMART-CHD achieve better control of modifiable risk factors compared with usual care? Researchers will compare SMART-CHD to standard discharge management (verbal and printed instructions on medications, follow-up timelines and lifestyle advice) to see if the AI-driven platform leads to fewer adverse events and improved risk-factor profiles. Participants will: 1. Install and use the SMART-CHD mobile app after a 10-minute structured orientation session with supervised simulations. 2. Complete regular in-app surveys on lifestyle behaviors, laboratory/imaging results and clinical events (with OCR-powered LLM assistance). 3. Wear paired sensors for continuous monitoring of blood pressure, heart rate and other physiologic metrics. 4. Receive automated EHR data harvesting, AI-driven voice-call reminders, and real-time CRC support via a dedicated WeChat group. 5. Follow personalized, guideline-based risk-factor recommendations (diet, exercise, sleep, weight, smoking, alcohol, hypertension, dyslipidemia, diabetes).