HashiCorp Sentinel vs Open Policy Agent

HashiCorp Sentinel has no write-up on Specifiction yet; its figures are above.

Open Policy Agent (OPA) is a free, open-source policy engine that separates policy decisions from the systems that enforce them. It evaluates policies against structured input and can return structured data, making it applicable to microservices, Kubernetes, CI/CD pipelines, and API gateways. Policies use Rego, a declarative language for complex hierarchical data. Applications can request evaluations through a REST API, Go API, WebAssembly runtimes, or custom evaluators using OPA's intermediate representation. Bundles distribute policy and data to OPA instances, while discovery bundles carry configuration. Management interfaces support policy distribution, health and status checks, and decision logs. Listed integrations include Kubernetes, Terraform, Envoy, and code editors; the documentation recommends OPA Gatekeeper for Kubernetes admission control. Installation options cover macOS, Linux/Unix, Windows, and Docker. OPA's security guidance says API authentication and authorization are off by default and recommends configuring TLS, authentication, and authorization when securing the API. OPA is a graduated Cloud Native Computing Foundation project.