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v2.0.0
MCP Python SDK v2 Stable Release
This is v2.0.0, the stable v2 release of the MCP Python SDK. It supports the 2026-07-28 revision of the Model Context Protocol and serves every earlier revision from the same server.
pip install mcpnow installs 2.x.pip install "mcp[cli]" # or uv add "mcp[cli]"Documentation Rewrite
The documentation has the full tutorial and API reference. Coming from v1? What's new in v2 is the tour of what changed and why, and the migration guide lists every breaking change with before-and-after code.
V1 Maintenance mode
v1.x is in maintenance mode and will only receive security fixes from now on The 1.x line lives on the
v1.xbranch, continues to receive critical bug fixes and security patches, and is documented at https://py.sdk.modelcontextprotocol.io/v1/. If your project is not ready to migrate, keep a<2upper bound on your requirement (for examplemcp>=1.28,<2).Highlights
One SDK, both protocol eras
v2 speaks the 2026-07-28 revision (stateless requests with no handshake,
server/discover,subscriptions/listen, multi-round-trip requests) and still serves every 2025-era client from the sameMCPServer, over Streamable HTTP and stdio, with nothing to configure.Client(target)negotiates the version automatically.
FastMCPis nowMCPServer, and there is a first-classClientThe decorator API is unchanged; the low-level
Serveris rebuilt around a shared dispatcher engine, and oneClientobject replaces v1's transport-plus-ClientSession-plus-initialize()layering. It connects to a URL, a stdio subprocess, a custom transport, or straight to a server object in memory for tests.Multi-round-trip requests and resolver dependency injection
At 2026-07-28 the server can no longer call the client, so tools return the question instead. A
Resolve(fn)parameter is filled by your function invisibly to the model and can put a question to the user; one tool body serves both eras.Extension APIs, OpenTelemetry, and a standalone types package
Servers and clients compose protocol extensions through pluggable extension APIs (MCP Apps built in); OpenTelemetry tracing ships on by default; every protocol type is its own package,
mcp-types(imported asmcp_types), published in lock-step withmcp.Hardened stdio and auth
stdio servers keep handler subprocesses and stray prints off the wire, and stdout is diverted to stderr while serving. OAuth adds RFC 9207 issuer validation, the SEP-990 identity-assertion flow, and the client-credentials extension.
Coming from a v2 pre-release
Since the last release candidate: the per-version wire packages are private (
mcp_types._v*),mcp.typesis a permanent alias formcp_types, the auth registration request model is split from the registered-client record, cancelled requests are no longer answered, and log notifications are gated on the per-request log-level opt-in at 2026-07-28. Since the betas:Client(cache=False)is nowcache=NonewithCacheConfig()the default;Context.client_id,RFC7523OAuthClientProvider, andOAuthClientProvider(timeout=)are removed; the client-credentials providers takescope=;message_handlerreceives notifications and exceptions only;FileResource(is_binary=)becomesencoding;MCP_*env vars are gone withpydantic-settings; Streamable HTTP servers reject bodies over 4 MiB with HTTP 413. The migration guide covers all of it.Known gaps
The tasks extension (SEP-2663) is not part of this release. On the client, the DPoP proof binding (SEP-1932) and the workload-identity
jwt-bearergrant are not implemented; both are additive and can land in 2.x.Feedback
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6f69a37
Present v2 as the stable release across the README, docs, and policies
(#3178)78e6fbb
Serve v2 docs at the site root, with permanent per-major paths (#3176)af06330
Remove unused StreamableHTTPTransport.get_session_id() (#3205)68ca87e
Document the two-line release process for stable v2 (#3179)c9c431b
Expose the middleware chain on MCPServer and stop sending unrequested
change ...528e366
Fail fast on server-to-client requests in JSON-response mode instead of
hangi...27f5cc7
Remove unused mcpserver.exceptions.ValidationError (#3199)89c5e70
Gate log notifications on the per-request log-level opt-in at 2026-07-28
(#3198)b61ce38
docs: fix off-by-one hl_lines in apps.md (#3196)b7c9a91
Add mcp.types as a permanent alias for mcp_types (#3190)