EthisysCore.Plugin.Sdk.Host 1.4.0

EthisysCore Plugin SDK Host

EthisysCore.Plugin.Sdk.Host is the runtime host used for .NET plugins that run out-of-process or in containers.

Supported Modes

Both modes use the same gRPC protocol (plugin_runtime.proto). The only difference is the network path: loopback TCP in out-of-process mode versus Dapr sidecar-to-sidecar routing in container mode.

Dapr Security Posture (Container Mode)

When the DAPR_API_TOKEN environment variable is set, the host runs in Dapr-secured mode. Two interceptors enforce the identity contract:

DaprGrpcInterceptor (outbound)

Added to every outbound gRPC channel from the plugin to the kernel. Sets the Dapr Host header to the kernel's Dapr app-ID so the local sidecar routes the call correctly. The app-ID is supplied by the kernel in the HostServicesAddress field of the Initialize request.

DaprCallerAppIdInterceptor (inbound)

Added to the Kestrel gRPC server pipeline. On every inbound call it validates the dapr-caller-app-id metadata header that Dapr injects on every service-invocation request:

• Disabled when DAPR_API_TOKEN is absent (local dev / out-of-process mode).
• Pre-Initialize pass-through while the expected caller ID is not yet set; Dapr's own access-control policy acts as the perimeter guard for this window.
• Header-stuffing protection — requires exactly one dapr-caller-app-id header; zero or more than one is rejected.
• Case-sensitive value comparison — header key lookup is OrdinalIgnoreCase; value comparison is Ordinal (Dapr app-IDs are case-sensitive).
• Rejects with PermissionDenied on any mismatch.

Contract Surface

The protocol is split into focused proto files under proto/pluginbridge/v1:

• plugin_runtime.proto — host → plugin lifecycle, tool, and resource calls
• host_services.proto — plugin → host callbacks
• datastore.proto, mcp.proto, and common.proto — shared bridge contracts

Use the handwritten Protocol package contracts where available; treat generated gRPC types as transport details.

Package Contents

• The SDK host executable and runtime files
• Compiled proto-generated types used by the host
• MSBuild targets required by consuming SDK-host scenarios

Usage

Plugin authors normally do not call this package directly. It is used by:

• The platform process host for out-of-process plugins
• Container entry points that run PluginHostRunner.Run<TPlugin>(args)
• Build/package workflows that need the runtime assets present

Related Packages

• EthisysCore.Plugin.Sdk for authoring .NET plugins
• EthisysCore.Protocol for transport-neutral contracts