The Model Context Protocol C# SDK reached v1.0 on March 5, 2026, adding authorization server discovery, Client ID Metadata Documents, tool sampling, and long-running async request support — bringing .NET to feature parity with the Python and TypeScript SDKs. This matters because enterprise .NET shops (banking, healthcare, insurance) previously had no production-grade MCP path; v1.0 removes that blocker. TypeScript SDK v1.27.1 and Python SDK v1.26 also shipped recent updates, and OpenAI's Agents SDK added MCP retry and error normalization in v0.12.5.