AGUI.Abstractions

AGUI.Abstractions is the protocol-types package for the AG-UI .NET SDK. It defines the shared event, message, tool, context, capability, interrupt, and serialization types used by AG-UI clients and servers.

dotnet add package AGUI.Abstractions

The package has no opinion about HTTP, ASP.NET Core, or a specific agent runtime. It is the .NET sibling of @ag-ui/core: stable wire types for the event stream and request payload.

AGUI.Abstractions targets net10.0, net9.0, net8.0, netstandard2.0, and net472. It is AOT-compatible: serializable protocol types are registered in the source-generated AGUIJsonSerializerContext.

SDK packages

The .NET SDK is split into small packages so protocol types, wire formats, client code, and server code can be adopted independently.

Package	Use it for
`AGUI.Abstractions`	Protocol events, messages, tools, capabilities, interrupts, and JSON serialization.
`AGUI.Formatting`	Event-stream formatter abstractions and Server-Sent Events support.
`AGUI.Protobuf`	Protobuf event-stream formatting and binary protocol support.
`AGUI.Client`	HTTP client and `IChatClient` implementation for consuming AG-UI endpoints.
`AGUI.Server`	Framework-agnostic adapter from `ChatResponseUpdate` streams to AG-UI events.

Wire formats and parity

JSON over Server-Sent Events is the full-fidelity event stream. AGUI.Formatting defines the event-stream formatter contract and SSE support. AGUI.Protobuf adds binary event-stream formatting for the protocol subset supported by the shared proto schema. Protocol parity starts in AGUI.Abstractions. When the TypeScript reference SDK adds or changes a wire type, the matching .NET event, message, tool, or capability type should update alongside AGUIJsonSerializerContext and the compatibility fixtures. Public API tracking files should update whenever a protocol change adds or changes .NET types.

cd sdks/dotnet
dotnet test tests/AGUI.Abstractions.UnitTests/
dotnet test tests/AGUI.Formatting.UnitTests/
dotnet test tests/AGUI.Protobuf.UnitTests/

Types

Core data structures that represent the building blocks of the protocol:

RunAgentInput - Input payload for running agents
Message types - Conversation, tool, activity, and reasoning messages
AGUIContext - Contextual information provided to agents
AGUITool - Tool definitions with JSON Schema parameters
AgentCapabilities - Structured capability declarations

Types Reference

Complete documentation of the protocol types in AGUI.Abstractions

Multimodal Inputs

User message content parts for text, image, audio, video, document, and binary input

Events

Events power communication between agents and frontends:

Lifecycle events - Run and step tracking
Text message events - Assistant message streaming
Tool call events - Function call lifecycle
State management events - Agent state and message snapshots
Reasoning events - Reasoning stream support
Activity events - Structured progress and transient UI state
Special events - Raw and custom events

Events Reference

Complete documentation of all event types in AGUI.Abstractions

TypeScript

Python

.NET

Overview

AGUI.Abstractions

SDK packages

Wire formats and parity

Types

Types Reference

Multimodal Inputs

Events

Events Reference

​AGUI.Abstractions

​SDK packages

​Wire formats and parity

​Types

Types Reference

Multimodal Inputs

​Events

Events Reference

AGUI.Abstractions

SDK packages

Wire formats and parity

Types

Events