Agent Framework 1.24: The Anthropic Agent Package Is Stable, Except for Beta Services

Microsoft Agent Framework dotnet-1.24.0 shipped on October 7, 2026, and one line in the changelog matters more than the rest if you run Claude-backed agents in .NET: PR #9111, “Stabilize Anthropic agent package”. Until last week, Microsoft.Agents.AI.Anthropic only existed as preview builds (the last one was 1.23.0-preview.260928.1). On NuGet it is now plain 1.24.0, published alongside the rest of the framework.

What stable actually covers

The package has two extension classes, and they did not get the same treatment.

AnthropicClientExtensions, which hangs AsAIAgent off IAnthropicClient, is now shipped public API. The PR adds PublicAPI.Shipped.txt baselines for every target framework the package builds for (net10.0, net9.0, net8.0, netstandard2.0, net472), so package validation will flag breaking changes from here on. The dependency also moved from Anthropic 12.45.0 to 12.53.0, the official Anthropic C# SDK, which is itself GA.

AnthropicBetaServiceExtensions, the AsAIAgent overloads on IBetaService (what you get from client.Beta), is the exception. The whole class is now marked [Experimental("MAAIANTHROPIC001")], with a doc note that it “may change in non-major releases as the underlying beta services evolve”. The reasoning in issue #9110 is straightforward: the Anthropic SDK is GA, but its beta surface is not, and Agent Framework does not want to promise a compatibility contract that its upstream does not.

What changes in your code

If you build agents from the regular client, nothing changes except the package version:

<PackageReference Include="Microsoft.Agents.AI.Anthropic" Version="1.24.0" />

using Anthropic;
using Microsoft.Agents.AI;

AnthropicClient client = new() { ApiKey = Environment.GetEnvironmentVariable("ANTHROPIC_API_KEY") };

ChatClientAgent agent = client.AsAIAgent(
    model: "claude-sonnet-5-5",
    instructions: "You review C# pull requests and answer in short bullet points.",
    name: "reviewer");

Console.WriteLine(await agent.RunAsync("Is `async void` ever fine in an ASP.NET Core handler?"));

The beta path is where it gets subtle. I compile-checked it on SDK 10.0.302 against the 1.24.0 package. First, the overloads live in the Anthropic.Services namespace, so client.Beta.AsAIAgent(...) does not resolve until you add that using. Second, the attribute sits on the class, not on the methods, and C# only reports a class-level [Experimental] when the type name appears in your code. Extension-method syntax never names the type, so this compiles cleanly with no diagnostic:

using Anthropic.Services;

ChatClientAgent agent = client.Beta.AsAIAgent(
    model: "claude-sonnet-5-5",
    instructions: "You create PowerPoint presentations.",
    tools: [pptxSkill.AsAITool()]);

Name the class directly, as in a static call or when you tune the shared default token budget, and you get an error, because [Experimental] diagnostics are errors by default:

AnthropicBetaServiceExtensions.DefaultMaxTokens = 8000;

error MAAIANTHROPIC001: 'Anthropic.Services.AnthropicBetaServiceExtensions' is for evaluation purposes only and is subject to change or removal in future updates. Suppress this diagnostic to proceed.

The framework’s own skills sample suppresses it at the top of the file with #pragma warning disable MAAIANTHROPIC001. If beta features are part of your design rather than an experiment, suppress it once for the project:

<PropertyGroup>
  <NoWarn>$(NoWarn);MAAIANTHROPIC001</NoWarn>
</PropertyGroup>

Why the split is the right call

Pinning a preview package in production is a common reason to keep Claude agents out of Agent Framework and wire IChatClient by hand instead (the tradeoffs are in my Anthropic SDK vs Microsoft.Extensions.AI comparison). That excuse is gone for the stable path. Just do not treat the diagnostic as an audit. Because the extension call shape slips past it, a clean build does not mean you are off the beta surface: grep for client.Beta and IBetaService to find the call sites that can break on a minor Agent Framework or Anthropic SDK bump.

The rest of 1.24.0 is hardening: LocalCodeAct capability validation, rejecting sensitive identifiers in declarative agents, and binding MCP approval headers to the approved invocation. If you skipped 1.23, start with its function middleware change before upgrading.