A secure runtime is an execution environment that limits what software can do while it is running. Instead of trusting the program to follow policy, the runtime can constrain file access, network calls, process spawning, tool use, and other sensitive actions. This makes it a practical defense layer when code is untrusted, complex, or able to operate for long periods.
In cyber security, secure runtimes matter because many attacks succeed after code is already executing. Malware, malicious scripts, prompt-injected AI agents, and compromised plugins all rely on runtime privileges to cause damage. A secure runtime can reduce that risk by isolating workloads, applying allowlists, and enforcing policy at execution time. In agent systems, it can shape behavior before an out-of-band watchdog or other control stops actions that cross a boundary. The goal is not to make software harmless, but to narrow the blast radius when something goes wrong.