The Model Context Protocol's next release candidate makes the protocol stateless, removing the initialize and initialized handshake and the Mcp-Session-Id header that tied a client to a single server instance. Protocol version, client info and capabilities now ride inline in a _meta field on every request.
To get there, SEP-2577 deprecates three of MCP's original features: Roots, Logging, and Sampling, the hook that let a server ask the client's own model to generate a completion. Server authors are now told to call a model provider's API directly instead. A new lifecycle policy keeps deprecated features in place for at least twelve months before removal, so nothing breaks the day the spec lands.
Sampling was the cleanest part of MCP's bring-your-own-model pitch, letting a tool stay model-agnostic and lean on whatever the user already pays for. Pulling it pushes model choice and billing back onto every server author, which is the price of an architecture that scales cleanly across distributed, load-balanced infrastructure.