04.2.4-anthropic-agents

Chapter 4.2.4 -- Anthropic / Claude as a ChatClientAgent

Companion code for Generative AI in .NET, Chapter 4 section 4.2.4 ("Anthropic Agents").

Uses an AnthropicClient and hands its chat surface to a standard ChatClientAgent. The same agent API works against OpenAI, Azure OpenAI, Ollama, etc.

Why the local AnthropicChatClient.cs shim? Anthropic.SDK 5.10.0 was compiled against Microsoft.Extensions.AI.Abstractions 10.3.0, but the repo pins 10.5.0 (required by Microsoft.Agents.AI 1.3.0, which itself rejects 10.3 with CS1705). 10.5 reshaped HostedMcpServerTool.AuthorizationToken, so new AnthropicClient(apiKey).Messages (which routes through the SDK's bundled ChatClientHelper) throws MissingMethodException at runtime. The shim sidesteps the helper by calling AnthropicClient.Messages.GetClaudeMessageAsync directly and translating between Anthropic's wire types and Microsoft.Extensions.AI types itself. When Anthropic.SDK 5.11+ ships rebuilt against M.E.AI 10.5+, drop the shim and revert to new AnthropicClient(apiKey).Messages. See docs/verification-log.md (entry 2026-05-02) for the full chain of reasoning. The chapter prose describes the intended pattern; this folder ships a concrete adapter so the sample is runnable today.

Run it

export ANTHROPIC_API_KEY=sk-ant-...
dotnet run --project samples/ch04-agent-framework/04.2.4-anthropic-agents

Override the model with ANTHROPIC_MODEL (defaults to claude-haiku-4-5-20251001).

Manuscript reference

• Manuscript/Chapter-04.md, section 4.2.4.
• Manuscript/Appendix-B-Model-Quick-Reference.md for current Claude model IDs.

Prerequisites

• .NET 9 SDK and an Anthropic API key.

Verifying model IDs are still callable

A throwaway harness at tests/AnthropicVerification/ hits the live API with each model ID listed in Appendix B. The harness has no Microsoft.Agents.AI dependency, so it can pin to M.E.AI 10.3.0 and run end-to-end -- use it during the pre-print verification passes to confirm Anthropic has not rotated the cited identifiers.