Microsoft ships C# SDK for AG-UI agent-to-app protocol
Microsoft announced a .NET SDK for AG-UI on September 25, developed with CopilotKit, so C# developers can use the protocol that standardizes communication between AI agents and user-facing applications. The SDK joins the TypeScript and Python versions in the AG-UI repository and is available on NuGet under the MIT license, with support usable from any .NET service. AG-UI is an event-based protocol with eight event categories, and the .NET SDK provides server and client components for exposing or consuming AG-UI endpoints.
Microsoft's September 25 release gives C# developers a .NET SDK for AG-UI, built with CopilotKit. It sits beside TypeScript and Python implementations in the AG-UI repository and is offered on NuGet under MIT terms. The C# version can be used from any .NET service, and Microsoft Agent Framework's AG-UI support now relies on it.
AG-UI is event-based and defines eight event groups: life-cycle, text message, tool call, state management, activity, subagent, special, and draft. The SDK works both ways: AGUI.Server exposes an agent as an endpoint, while AGUI.Client lets .NET apps consume one. Five NuGet packages cover abstractions, formatting, Protobuf, client, and server pieces.
This SDK could lower barriers for C# and .NET teams building agent-powered interfaces, letting more developers connect AI agents to existing applications. That may speed experimentation with assistants in customer support, productivity tools, and internal workflows. It could also make agent behavior more consistent across languages, though adoption depends on developer interest, protocol maturity, and whether organizations trust agents with sensitive tasks. End users may see more responsive, integrated AI features, but also new reliability and privacy questions.