Arch is a sophisticated gateway designed to safeguard, monitor, and tailor AI agents through effortless API integration. Leveraging the power of Envoy Proxy, Arch ensures secure data management, intelligent request routing, comprehensive observability, and seamless connections to backend systems, all while remaining independent of business logic. Its out-of-process architecture supports a broad range of programming languages, facilitating rapid deployment and smooth upgrades. Crafted with specialized sub-billion parameter Large Language Models, Arch shines in crucial prompt-related functions, including function invocation for API customization, prompt safeguards to thwart harmful or manipulative prompts, and intent-drift detection to improve retrieval precision and response speed. By enhancing Envoy's cluster subsystem, Arch effectively manages upstream connections to Large Language Models, thus enabling robust AI application development. Additionally, it acts as an edge gateway for AI solutions, providing features like TLS termination, rate limiting, and prompt-driven routing. Overall, Arch represents an innovative approach to AI gateway technology, ensuring both security and adaptability in a rapidly evolving digital landscape.