Issues

Issues

• client_credentials sends the credential to an unverified issuer unless issuer= is passed (4.1.2)

  modelcontextprotocol/python-sdk#3850 · opened on Nov 12, 2026
  1

• Mcp-Param-* schema listing is not cancelled when a 2026-07-28 SSE client disconnects

  modelcontextprotocol/python-sdk#3849 · opened on Nov 11, 2026
  5

• docs(client): ClientSession documents only the input-required kwargs, not its mandatory parameters

  modelcontextprotocol/python-sdk#3846 · opened on Nov 9, 2026
  2

• [v2] docs: Client callbacks page doesn't say list_changed needs client.listen()

  modelcontextprotocol/python-sdk#3845 · opened on Nov 9, 2026
  4

• Authorization server selection is first-in-list for pre-provisioned providers

  modelcontextprotocol/python-sdk#3844 · opened on Nov 9, 2026
  3

• HttpResource silently decodes PNG response bytes into lossy TextResourceContents

  modelcontextprotocol/python-sdk#3843 · opened on Nov 9, 2026
  5

• A resource template value that fails the handler's type hint is logged as a crash and answered -32603

  modelcontextprotocol/python-sdk#3837 · opened on Nov 8, 2026
  3

• OTel client spans: add server.address (and other semconv client attributes) so tool calls can be attributed to a server

  modelcontextprotocol/python-sdk#3836 · opened on Nov 8, 2026
  4

• v1.30.0: normal streamable-HTTP session close logs "Error in standalone SSE writer" (anyio.ClosedResourceError) at ERROR

  modelcontextprotocol/python-sdk#3833 · opened on Nov 7, 2026
  2

• stdio_server: text a tool prints still reaches the client, because sys.stdout is flushed after fd 1 is restored

  modelcontextprotocol/python-sdk#3821 · opened on Nov 5, 2026
  3

• Non-ASCII base64 Mcp-Name header returns 500 instead of HEADER_MISMATCH

  modelcontextprotocol/python-sdk#3817 · opened on Nov 4, 2026
  2

• [Bug] ResourceManager.add_template() ignores warn_on_duplicate_resources and silently overwrites existing templates

  modelcontextprotocol/python-sdk#3813 · opened on Nov 3, 2026
  7

• OTel client span sets ERROR status for -32602 and other caller-error codes

  modelcontextprotocol/python-sdk#3811 · opened on Nov 3, 2026
  2

• OTel client span stays Unset when the tool result has isError: true

  modelcontextprotocol/python-sdk#3810 · opened on Nov 3, 2026
  4

• stdio_server cannot be cancelled, and the process cannot exit, while the client still holds stdin open

  modelcontextprotocol/python-sdk#3808 · opened on Nov 3, 2026
  2

• notifications/cancelled for request 7 cancels a concurrent request "7" (_in_flight keyed by coerce_request_id)

  modelcontextprotocol/python-sdk#3807 · opened on Nov 2, 2026
  6

• Server stop hangs while a 2026-07-28 subscriptions/listen stream is open

  modelcontextprotocol/python-sdk#3806 · opened on Nov 2, 2026
  6

• images.py example returns raw pixels from tobytes() labelled image/png, so clients cannot decode the thumbnail

  modelcontextprotocol/python-sdk#3805 · opened on Nov 2, 2026
  4

• stdio client: requests hang forever after the server closes stdout but keeps running

  modelcontextprotocol/python-sdk#3804 · opened on Nov 2, 2026
  4

• Tool results over 1 MiB cannot be received over SSE or streamable HTTP, and the limit is not configurable

  modelcontextprotocol/python-sdk#3803 · opened on Nov 2, 2026
  5

• ClientSessionGroup.connect_to_server leaves the caller's task cancelled when an HTTP server is unreachable

  modelcontextprotocol/python-sdk#3801 · opened on Nov 2, 2026
  3

• MCP Apps: clientCapabilities from the per-request _meta envelope never reaches handlers on stateless Streamable HTTP — client_supports_apps() is always False

  modelcontextprotocol/python-sdk#3800 · opened on Nov 2, 2026
  2

• Raise a distinct error when a Streamable HTTP session is lost (HTTP 404)

  modelcontextprotocol/python-sdk#3799 · opened on Nov 2, 2026
  2

• ClientSessionGroup silently omits later pages of tools, resources, and prompts

  modelcontextprotocol/python-sdk#3792 · opened on Oct 31, 2026
  3

• Productive SSE reconnects accumulate stack frames and eventually fail

  modelcontextprotocol/python-sdk#3791 · opened on Oct 31, 2026
  1