The Model Context Protocol (MCP) Python SDK has released its v2.0.0 stable version, which supports the 2026-07-28 revision of the Model Context Protocol while remaining compatible with earlier revisions from the same server.
- The SDK now speaks the 2026-07-28 protocol (stateless requests, `server/discover`, subscriptions) and serves every 2025-era client from the same `MCPServer` without configuration.
- `FastMCP` is renamed to `MCPServer`, featuring a shared dispatcher engine, while a first-class `Client` object replaces the previous transport-plus-session layering.
- Multi-round-trip requests are supported via a `Resolve(fn)` parameter that allows tools to return questions to the user invisibly.
- OpenTelemetry tracing is enabled by default, and protocol types are now in a standalone package called `mcp-types`.
- Security enhancements include hardened stdio handling (diverting stdout to stderr) and OAuth support for RFC 9207 issuer validation and SEP-990 identity assertion.
The v1.x line has entered maintenance mode, receiving only security fixes and critical bug patches. Users are advised to update their requirements to `<2` if they are not ready to migrate.