Open Policy Agent (OPA) brings fine-grained, declarative control to your systems. With Zsh, the most advanced shell for many developers, OPA can enforce rules on every command, every script, every API call you initiate. Pairing OPA with Zsh turns your shell into more than a command runner—it becomes a policy checkpoint.
OPA works by evaluating policies written in Rego. These policies define the conditions under which actions are allowed or denied. By integrating OPA directly into Zsh, you can make those checks seamless and invisible to the user until the moment a rule triggers. This can prevent unsafe deployments, block risky scripts, or require approval for sensitive operations.
To set up OPA with Zsh, start by installing OPA locally, or run it as a service. Then, create a script wrapper for your Zsh commands that sends relevant context—command, arguments, environment variables—to OPA’s REST API. Zsh’s preexec hooks are especially useful for intercepting commands before they execute. OPA returns a decision, and based on that decision, your shell either continues or halts.