The concepts behind a plugin call
A plugin call connects your application to one approved piece of extension code. The concepts below explain what the host controls and what remains in your application. Your .NET application hosts the runtime and decides when a plugin is called. Plugins implement application-defined functions and asynchronous result streams in C#, Python or TypeScript.
A binding is an authority boundary
A binding combines the host-selected tenant context, plugin artifact/version, execution profile and callback grants. Request payloads do not choose tenant authority or executable paths. A used worker is never reassigned to another tenant.
A client binding is single-flight, including the entire enumeration of a stream. Use independent bindings for parallel work, subject to shared worker and admission limits.
Callbacks connect plugins to application services
A plugin can ask the host for a capability such as reading a document or looking up knowledge. The host grants the capability explicitly. The callback implementation must still authorize the particular object being accessed; a grant is not permission to access every customer’s data.
State belongs to the application
Worker memory is temporary. Persist facts, workflow checkpoints and external-action identities in application-owned stores. An interrupted call may have produced an external effect. Recovery and retry require an explicit application policy; cancellation is not proof that nothing happened.
Share the execution budget
The copyable coordinator template owns one host and shared operation admission. It is application source, not another public package API. Multiple coordinators have independent budgets. Native memory reservations are estimates for admission, not enforced OS memory ceilings.
Choose execution according to trust
Native execution is for owner-controlled code running with the host OS user's rights. It does not confine hostile plugins. Container execution has a different deployment policy and trust boundary; a profile switch does not prove equivalent qualification.
Read the architecture, integration contract, worker lifecycle and security architecture for exact boundaries and limitations. OpenSpec requirements define verified behavior.