• Designed a failure-detection system for AI responses (“false success” cases) , automatically triggering provider fallback to ensure reliability. • Implemented a multi-tenant Node.js backend using Role-Based Access Control (RBAC) to enforce strict dataisolation and keep different user workspaces completely separate.• • Secured the Express.js APIs by adding rate limiting to prevent spam and abuse, which protected the expensive AIendpoints from getting overloaded.