Rein Security provides an application security platform built on real-time runtime visibility technology. The company's approach operates at the OS boundary, observing system calls and correlating them with runtime context without modifying applications or injecting code. This architecture enables the platform to capture complete execution context including HTTP requests, API endpoints, library invocations, and stack traces with sub-millisecond latency and minimal CPU overhead. The platform unifies multiple application security capabilities including API security, software composition analysis (SCA), static application security testing (SAST), and AI security around a single source of runtime truth. When vulnerabilities are discovered, the system identifies which parts of applications use vulnerable code paths and whether they execute in production. For AI agents, the platform tracks the complete chain of user initiation, model processing, API calls, and data access. Rein Security's technology can be enabled or disabled through a portal without requiring application restarts or redeployment. The company was founded by Matan Bar Efrat (CEO) and Netanel Rubin (CTO), both with backgrounds in cybersecurity and intelligence. The platform addresses the challenge of application security tools relying on guesswork through sampled traffic, logs, proxies, and scans by providing continuous visibility into actual application behavior and resource interactions.