Remove client OTel session-id wrapper

Author: Kludex

src/mcp/client/streamable_http.py

@@ -7,7 +7,6 @@
 from collections.abc import AsyncGenerator, Awaitable, Callable
 from contextlib import asynccontextmanager
 from dataclasses import dataclass
-from types import TracebackType
 
 import anyio
 import httpx
@@ -18,7 +17,6 @@
 from mcp.client._transport import TransportStreams
 from mcp.shared._context_streams import ContextReceiveStream, ContextSendStream, create_context_streams
 from mcp.shared._httpx_utils import create_mcp_http_client
-from mcp.shared._stream_protocols import WriteStream
 from mcp.shared.message import ClientMessageMetadata, SessionMessage
 from mcp.types import (
     INTERNAL_ERROR,
@@ -514,35 +512,6 @@ def get_session_id(self) -> str | None:
         return self.session_id  # pragma: no cover
 
 
-class _SessionAwareWriteStream:
-    """Write-stream wrapper that exposes the transport session ID."""
-
-    def __init__(self, inner: WriteStream[SessionMessage], transport: StreamableHTTPTransport) -> None:
-        self._inner = inner
-        self._transport = transport
-
-    async def send(self, item: SessionMessage) -> None:
-        await self._inner.send(item)
-
-    async def aclose(self) -> None:
-        await self._inner.aclose()
-
-    def get_session_id(self) -> str | None:
-        return self._transport.session_id
-
-    async def __aenter__(self) -> _SessionAwareWriteStream:
-        await self._inner.__aenter__()
-        return self
-
-    async def __aexit__(
-        self,
-        exc_type: type[BaseException] | None,
-        exc_val: BaseException | None,
-        exc_tb: TracebackType | None,
-    ) -> bool | None:
-        return await self._inner.__aexit__(exc_type, exc_val, exc_tb)
-
-
 # TODO(Marcelo): I've dropped the `get_session_id` callback because it breaks the Transport protocol. Is that needed?
 # It's a completely wrong abstraction, so removal is a good idea. But if we need the client to find the session ID,
 # we should think about a better way to do it. I believe we can achieve it with other means.
@@ -612,7 +581,7 @@ def start_get_stream() -> None:
             )
 
             try:
-                yield read_stream, _SessionAwareWriteStream(write_stream, transport)
+                yield read_stream, write_stream
             finally:
                 if transport.session_id and terminate_on_close:
                     await transport.terminate_session(client)

src/mcp/shared/_otel.py

@@ -42,7 +42,6 @@ def build_client_span_attributes(
     method: str,
     request_id: str | int,
     params: dict[str, Any] | None = None,
-    session_id: str | None = None,
 ) -> dict[str, Any]:
     """Build OTel attributes for an MCP client request span."""
     attributes: dict[str, Any] = {
@@ -55,9 +54,6 @@ def build_client_span_attributes(
     if params is not None and (resource_uri := params.get("uri")) is not None:
         attributes["mcp.resource.uri"] = resource_uri
 
-    if session_id is not None:
-        attributes["mcp.session.id"] = session_id
-
     return attributes
 
 

src/mcp/shared/session.py

@@ -5,7 +5,7 @@
 from collections.abc import Callable
 from contextlib import AsyncExitStack
 from types import TracebackType
-from typing import Any, Generic, Protocol, TypeVar, cast
+from typing import Any, Generic, Protocol, TypeVar
 
 import anyio
 from anyio.streams.memory import MemoryObjectSendStream
@@ -236,13 +236,6 @@ async def __aexit__(
         self._task_group.cancel_scope.cancel()
         return await self._task_group.__aexit__(exc_type, exc_val, exc_tb)
 
-    def _get_transport_session_id(self) -> str | None:
-        """Return the transport session ID when the write stream exposes it."""
-        get_session_id = getattr(self._write_stream, "get_session_id", None)
-        if callable(get_session_id):
-            return cast("str | None", get_session_id())
-        return None
-
     async def send_request(
         self,
         request: SendRequestT,
@@ -287,7 +280,6 @@ async def send_request(
                     method=request.method,
                     request_id=request_id,
                     params=request_data.get("params"),
-                    session_id=self._get_transport_session_id(),
                 ),
             ):
                 # Inject W3C trace context into _meta (SEP-414).

tests/shared/test_streamable_http.py

@@ -23,7 +23,6 @@
 import requests
 import uvicorn
 from httpx_sse import ServerSentEvent
-from logfire.testing import CaptureLogfire
 from starlette.applications import Starlette
 from starlette.requests import Request
 from starlette.routing import Mount
@@ -1082,26 +1081,6 @@ async def test_streamable_http_client_resource_read(initialized_client_session:
     assert response.contents[0].text == "Read test-resource"
 
 
-@pytest.mark.anyio
-@pytest.mark.filterwarnings("ignore::RuntimeWarning")
-async def test_streamable_http_resource_read_spans_include_session_id(
-    capfire: CaptureLogfire, basic_server: None, basic_server_url: str
-):
-    """Verify streamable HTTP spans include the negotiated MCP session ID."""
-    async with streamable_http_client(f"{basic_server_url}/mcp") as (read_stream, write_stream):
-        async with ClientSession(read_stream, write_stream) as session:
-            await session.initialize()
-            response = await session.read_resource(uri="foobar://test-resource")
-
-    assert response.contents[0].uri == "foobar://test-resource"
-
-    spans = capfire.exporter.exported_spans_as_dict()
-    client_span = next(s for s in spans if s["name"] == "MCP send resources/read")
-
-    assert client_span["attributes"]["mcp.session.id"]
-    assert client_span["attributes"]["mcp.resource.uri"] == "foobar://test-resource"
-
-
 @pytest.mark.anyio
 async def test_streamable_http_client_tool_invocation(initialized_client_session: ClientSession):
     """Test client tool invocation."""