MCP Python SDK 2.0.0 renames FastMCP to MCPServer, takes over the mcp PyPI name, and puts 1.x into maintenance mode

The MCP Python SDK published v2.0.0 on July 28, and pip install mcp now installs the 2.x line. The release renames the high-level FastMCP server class to MCPServer with the decorator API unchanged, rebuilds the low-level Server, and replaces v1's transport plus ClientSession plus initialize() layering with one unified Client object. It supports the 2026-07-28 revision and serves every earlier revision from the same server.

The v1 line moves to maintenance mode, receiving only security fixes from now on, and the release notes recommend that projects staying on it declare an upper bound such as mcp>=1.28,<2. Protocol types split into a standalone mcp-types package published in lock-step, with mcp.types kept as a permanent alias. Removals include Context.client_id, RFC7523OAuthClientProvider, the OAuthClientProvider(timeout=) parameter, and the MCP_* environment variables along with the pydantic-settings dependency. Streamable HTTP servers now reject request bodies over 4 MiB with HTTP 413.

The release notes also name what did not make the cut: the tasks extension (SEP-2663) is not in this release, and on the client side DPoP proof binding (SEP-1932) and the workload-identity jwt-bearer grant are not implemented.

The mcp.server.fastmcp module removal broke downstream projects immediately. AWS's server collection pinned the SDK below 2.0.0 the same day, with a release entry reading "fix: pin ceiling mcp SDK <2.0.0 for servers using the removed mcp.server.fastmcp module". That pin is direct evidence the breakage was real in at least one major downstream; how far it reached beyond that has not been surveyed.