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2026.08.03 · 4 min read

Teams SDK for .NET 2.1 is now Generally Available

AUTHOR :Mehak Bindra
TOPICS :
teams-sdkdotnetannouncementga

Today we're announcing the general availability (GA) of Teams SDK 2.1 for .Net. This release brings the full ASP.NET Core ecosystem to your Teams bot: DI, configuration, logging, middleware, and MSAL-native auth all work exactly as they do in any other .NET service. On top of that foundation, 2.1 ships agentic identity support, built-in state management, OpenTelemetry instrumentation, and a redesigned multi-flow OAuth model.

Install to get started:

dotnet add package Microsoft.Teams.Apps

If you're building on an existing app, see the migration guide to plan your upgrade.

ASP.NET Core is now the foundation​

In 2.0, the SDK owned too much: a plugin architecture, a proprietary server lifecycle, a custom event bus, a separate dependency system, and full ownership of hosting, configuration, logging, HTTP, and storage. This meant every team had to work around the SDK instead of with the .NET ecosystem they already knew. In 2.1, the SDK steps back. It handles the Teams-specific parts (inbound activity validation, activity dispatch, auth via MSAL and outbound message builders and clients) and hands everything else back to ASP.NET Core. A basic Teams agent is now a small ASP.NET Core application with a message handler — services, configuration, logging, middleware, and authorization all work exactly as they do in any other .NET app.

Handlers in 2.1 are typed, readable, and composable, with regex routing for messages and a rich context object that gives you the typed activity, DI-resolved services, logging, and outbound helpers all in one place.

For the full overview, see the migration guide.

What's shipping in 2.1​

Agentic identity​

Using the Teams SDK, you can bring an Agent 365 agentic identity to Teams as an AI teammate, a first-class Microsoft 365 entity with its own mailbox, Teams presence, and directory entry. Unlike a traditional bot, an AI teammate calls APIs with its own identity, not app permissions. Actions are attributed to it in audit logs, and it's scoped to what it can access.

The SDK handles the token resolution automatically per turn. You don't change how you call APIs; you just optionally check whether the turn is agentic using context.Activity.Recipient?.GetAgenticIdentity().

See the Agentic Identity guide.

Multi-flow OAuth​

In 2.0, OAuth was a single pair of OnSignIn/OnSignInFailure events. Multiple connections meant branching inside a shared callback. In 2.1, each connection is a named flow registered at startup with its own lifecycle: sign-in trigger, success callback, and failure callback are all scoped per connection. Multiple flows stay isolated and independently testable. See the User Authentication guide.

Built-in state​

2.0 had no state model. 2.1 ships ConversationState and UserState out of the box via options.UseState(), backed by IDistributedCache. It defaults to in-memory for local development. To go distributed (Redis, SQL, Azure Cache), you register a cache provider before calling UseState(), and your handler code doesn't change at all.

See the State Management guide.

OpenTelemetry instrumentation​

The SDK now instruments its pipeline through standard .NET primitives (ActivitySource, Meter, and ILogger), following the .NET library instrumentation model: the SDK produces telemetry, your app chooses where it goes. Route to Azure Monitor, an OTLP collector, or both.

See the OpenTelemetry guide.

Integrating with your stack​

Pairing Teams SDK with your agent framework​

The Teams SDK's built-in AI helpers (ChatPrompt, OpenAIChatModel, MCP and A2A plugins) are removed in 2.1. The SDK's role is to be the best Teams runtime layer, not an agent framework. Dedicated frameworks (OpenAI SDK, Microsoft Agent Framework, LangChain, Foundry) handle the AI loop better than a bundled helper can. The AI libraries to agent frameworks post covers the rationale and how to migrate.

Bot Framework v4 compatibility​

If you have an existing Bot Framework v4 bot, you can run it on the new SDK infrastructure without rewriting your handlers. Install the compatibility package and pass your existing IBot implementation: two lines, and your bot works unchanged.

See the BotBuilder migration guide.

Get started​