Microsoft Agent Framework

Microsoft Agent Framework .NET 1.22.0 adds AIAgent.AsIChatClient(), closing the round trip with IChatClient.AsAIAgent(). Your agent, with its instructions and tools intact, now plugs into any API that takes an IChatClient.

Microsoft Agent Framework .NET 1.21.0 ships Microsoft.Agents.AI.LocalCodeAct 1.21.0-preview.260911.1, which no longer lets the CodeAct Python subprocess inherit the parent environment when Environment is null. On 1.20, generated code could read every host variable, API keys included.

The agent-framework-hosting packages are conversion helpers, not a runtime. One Agent instance, one AgentState, and three thin adapters give you a Telegram bot, an A2A peer, and an MCP tool from the same process. Here is the wiring, the per-channel session-ID policy, and the four things each channel refuses to do.

Agent Framework ships an in-memory chat history provider and nothing else for .NET. Here is a Cosmos DB backed ChatHistoryProvider that survives process restarts, the container design that keeps a 200-turn session cheap, and the second provider you need if you want semantic recall across sessions.

Conversation history can live in your process, in your database, in the provider, or on the machine that ran the agent. Where you put it does not change your token bill, it decides your retention exposure, and it decides whether you can ever change providers. The numbers, the retention windows, and a storage shape that survives all three.

Defensive system prompts are heuristic. Information-flow control is not: label every piece of content with integrity and confidentiality, propagate most-restrictive-wins through every tool call, and check the label at the sink before it runs. An 80-line runnable harness, the Agent Framework FIDES implementation, and the false positives the pattern buys you.

Stop shipping SKILL.md folders inside every agent deployment. Serve them from an MCP server and pull them with UseMcpSkills on Microsoft.Agents.AI.Mcp 1.18. Includes the exact skill://index.json shape, a working C# server, the wire trace, and the SEP-2640 drift that will bite you.

Replace a hand-rolled classifier-plus-switch router with AgentWorkflowBuilder.CreateHandoffBuilderWith in Microsoft.Agents.AI.Workflows 1.17.0. What breaks, the six migration steps, and the gotchas around agent Ids, descriptions, and context broadcast.

Use declarative YAML when the graph is a sequential routing decision that non-developers change often. Use code-first WorkflowBuilder the moment you need parallelism, custom executors, or a non-Foundry agent. Here is the decision, the action catalog limits, and the code both ways.

Microsoft.Agents.AI.GitHub.Copilot 1.16.0 shipped on July 30, 2026. The Copilot CLI runtime now sits behind the ordinary AIAgent abstraction, permissions are deny-by-default, and Squad plugs a whole agent team in as one AIAgent.