fix(mcp): detach session context instead of leaving it attached

instrumentation-loongsuite/loongsuite-instrumentation-mcp/CHANGELOG.md

@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Fixed
+
+- Detach the MCP session context instead of leaving it attached after the client transport exits
+  ([#280](https://github.com/alibaba/loongsuite-python/pull/280))
+
 ## Version 0.9.0 (2026-09-07)
 
 There are no changelog entries for this release.

instrumentation-loongsuite/loongsuite-instrumentation-mcp/src/opentelemetry/instrumentation/mcp/session_handler.py

@@ -82,7 +82,7 @@ def _safe_attach(self, context: Any):
 
     def _safe_detach(self, context: Any):
         try:
-            if context is None or hasattr(context[0], "_session_context"):
+            if context is None or not hasattr(context[0], "_session_context"):
                 return
             delattr(context[0], "_session_context")
         except Exception:

instrumentation-loongsuite/loongsuite-instrumentation-mcp/tests/test_session_handler.py

@@ -14,6 +14,7 @@
 
 import os
 from contextlib import asynccontextmanager
+from types import SimpleNamespace
 
 import pytest
 from mcp import JSONRPCRequest
@@ -25,6 +26,7 @@
 from opentelemetry import context, propagate
 from opentelemetry import trace as trace_api
 from opentelemetry.instrumentation.mcp import MCPInstrumentor, ServerMetrics
+from opentelemetry.instrumentation.mcp.session_handler import _SessionContext
 from opentelemetry.metrics import get_meter
 from opentelemetry.trace import SpanKind
 
@@ -38,6 +40,25 @@ async def mock_client(params):
     yield params
 
 
+def test_session_context_detach_removes_attached_context():
+    target = SimpleNamespace()
+    session_context = _SessionContext({})
+    context = (target,)
+    session_context._safe_attach(context)
+    assert hasattr(target, "_session_context")
+
+    session_context._safe_detach(context)
+
+    assert not hasattr(target, "_session_context")
+
+
+def test_session_context_detach_without_attachment_does_not_raise():
+    target = SimpleNamespace()
+    session_context = _SessionContext({})
+    session_context._safe_detach((target,))
+    assert not hasattr(target, "_session_context")
+
+
 @pytest.mark.asyncio
 async def test_client_invalid(tracer_provider):
     import mcp.client.sse  # noqa: PLC0415