Bastion is a multi-agent code intelligence platform that scans GitHub repositories for security vulnerabilities and surfaces actionable fix recommendations. Architected a 6-stage async scanning pipeline using Celery and Redis (clone → validate → Bandit security scan → AST parse → AI review → save findings), enabling parallel multi-file analysis without blocking API requests. Built real-time scan progress updates via Redis Pub/Sub and WebSockets. Integrated a RAG system using Pinecone with AST-based symbol-level chunking for repository-aware code understanding. Combines Bandit static analysis with Gemini AI review behind GitHub OAuth and JWT-protected endpoints.