MCP Python SDK v2.0.0b1 Released with Full 2026 Spec Support

The Model Context Protocol (MCP) Python SDK has released its first beta version, v2.0.0b1, which introduces full support for the 2026-07-28 MCP specification. This pre-release is opt-in only, ensuring that standard installations continue to resolve to the stable 1.x line.

• The core architecture replaces session-centric internals with a stateless dispatcher/runner pipeline compatible with the new protocol.
• The previous `FastMCP` class is now `MCPServer`, featuring snake_case fields and wire validation against the negotiated spec version.
• A new `Client` class automatically probes for protocol versions and supports various targets including URLs, stdio subprocesses, and in-memory servers.
• Protocol types are available as a standalone package (`mcp-types`) dependent only on Pydantic and typing-extensions.
• The update includes RFC 6570 URI template support, middleware with default OpenTelemetry tracing, and enterprise authentication via SEP-990.

This release allows developers to test the settled v2 architecture ahead of the stable launch, with migration guides available for those transitioning from v1.