Microsoft has released the MCP C# SDK version 2.0, a significant update for the official software development kit supporting Model Context Protocol servers and clients. This latest iteration introduces a fundamental shift toward stateless architecture, aligning the library with the most recent updates to the underlying protocol specification.
Transition to Stateless Protocol Architecture
The release of the MCP C# SDK v2.0 marks a pivotal change in how the framework handles communication between AI models and external data sources. By implementing the July 2026 revision of the Model Context Protocol, Microsoft has transitioned the default operational mode from stateful to stateless. This change represents the most extensive overhaul of the protocol since its initial introduction to the developer community.
In earlier versions of the SDK, specifically the 1.x branch, the system relied on stateful sessions by default. These sessions required the server and client to maintain a constant, active connection to track the context of interactions. The new version reverses this requirement, setting the default configuration for HTTP server transport options to stateless. Developers who prefer the previous behavior must now manually opt into stateful session management.
