Microsoft Agent Framework

Microsoft Agent Framework for .NET 1.27.0 makes DefaultHttpRequestHandler throw HttpRequestException when its client-provider callback returns a client for a redirect destination. Here is why that hole existed, what breaks, and how to rewrite the callback.

If a specialist agent is just a model loop wrapped around a few read-only calls into your own services, collapse it into a skill served over MCP: a SKILL.md plus typed tools that the parent model calls directly. Keep it an A2A agent when it needs its own model, private context, a long multi-step workflow or an independent lifecycle. Here is the decision matrix, the measured cost of each path, and the Agent Framework 1.17 wiring.

Microsoft Agent Framework 1.26.0 makes MapAGUIServer resolve the keyed AIAgent, its AgentSessionStore, and the isolation key provider per request, and adds a selector overload that picks the agent from the HttpContext.

On container protocol 2.0.0, Foundry hosted agents isolate conversations and sessions per Entra caller by default. When your own backend fronts many end users, you delegate with x-ms-user-identity, grant a custom impersonation role, and key everything your container stores by session ID plus user ID. Here is the C# for each layer and the traps that leak data between users.

Magentic orchestration is Agent Framework's port of AutoGen's Magentic-One: an LLM manager writes a fact sheet and plan (the task ledger), then grades every round with a JSON progress ledger to pick the next agent, detect stalls and replan. Here is how the loop works on Microsoft.Agents.AI.Workflows 1.24.0 and agent-framework-orchestrations 1.3.1, what it costs per round, and the limit defaults that let it run forever.

Microsoft.Agents.AI.Anthropic 1.24.0 drops the preview suffix and depends on Anthropic 12.53.0. Agents built from IAnthropicClient are now stable API, while the client.Beta extensions are marked experimental under MAAIANTHROPIC001, which extension-method calls do not trigger.

The Agent Harness is Microsoft Agent Framework's batteries-included runtime: one call (AsHarnessAgent in .NET, create_harness_agent in Python) wraps any chat client in a tool loop with todos, plan/execute modes, file memory, tool approval, compaction and OpenTelemetry. Here is what it actually sends to the model on Microsoft.Agents.AI.Harness 1.23.0, what it costs per call, and how to trim it.

In a workflow, your code decides the next step and the model fills in each step. In an agent, the model decides the next step and your code only executes it. That one question (who owns the control flow) determines cost, latency, testability and failure modes. Here is the distinction as Anthropic, Microsoft Agent Framework and LangGraph define it, with the same task built both ways in Python against claude-haiku-4-5 and claude-sonnet-5-5.

Microsoft Agent Framework .NET 1.23.0 honors assignments to FunctionInvocationContext.Function, so middleware can redirect a tool call to a different AIFunction. A new WrapWithPendingMiddleware helper keeps the rest of the chain in the loop.

The AG-UI protocol now has a standalone .NET SDK: AGUI.Server 1.0.0 streams any IChatClient as AG-UI events over SSE, and AGUIChatClient consumes an AG-UI endpoint as an IChatClient, down to .NET Framework 4.7.2. Agent Framework users get renamed APIs.