Security AutoDesigner is an AI-assisted automotive Threat Analysis & Risk Assessment (TARA) tool designed for OEMs and Tier-1 automotive suppliers. It automates the creation of TARA reports to support compliance with ISO/SAE 21434 and UNECE WP.29 UNR 155 cybersecurity regulations. The tool draws on a curated threat database built from dozens of real-world automotive TARA projects, containing over 100 automotive-specific threats categorized by risk severity (from very low to critical). This threat database is continuously updated by PlaxidityX's research team as new automotive threats are identified. TARA generation is performed at both the vehicle level and the component/ECU level, allowing assessments to cover system-wide risks (e.g., CAN bus attacks) as well as specific components such as ECUs, sensors, and communication interfaces. The product supports continuous TARA updates triggered by changes in product architecture, and can incorporate vulnerability data (e.g., CVE/NVD feeds) through integration with PlaxidityX's SW Supply Chain Security tool to dynamically update risk assessments. Key automation benefits include a reported 60–80% reduction in manual effort, elimination of human bias in threat scoring, auto-generated ISO 21434-compliant reports, and accelerated time-to-market for vehicles and components. Security AutoDesigner can integrate with the PlaxidityX DevSecOps platform and connect to common requirements management tools.