Fix uncaught exception in MCP server (#967)

tests/shared/test_streamable_http.py

@@ -1521,3 +1521,40 @@ def test_server_backwards_compatibility_no_protocol_version(basic_server, basic_
     )
     assert response.status_code == 200  # Should succeed for backwards compatibility
     assert response.headers.get("Content-Type") == "text/event-stream"
+
+
+@pytest.mark.anyio
+async def test_client_crash_handled(basic_server, basic_server_url):
+    """Test that cases where the client crashes are handled gracefully."""
+
+    # Simulate bad client that crashes after init
+    async def bad_client():
+        """Client that triggers ClosedResourceError"""
+        async with streamablehttp_client(f"{basic_server_url}/mcp") as (
+            read_stream,
+            write_stream,
+            _,
+        ):
+            async with ClientSession(read_stream, write_stream) as session:
+                await session.initialize()
+                raise Exception("client crash")
+
+    # Run bad client a few times to trigger the crash
+    for _ in range(3):
+        try:
+            await bad_client()
+        except Exception:
+            pass
+        await anyio.sleep(0.1)
+
+    # Try a good client, it should still be able to connect and list tools
+    async with streamablehttp_client(f"{basic_server_url}/mcp") as (
+        read_stream,
+        write_stream,
+        _,
+    ):
+        async with ClientSession(read_stream, write_stream) as session:
+            result = await session.initialize()
+            assert isinstance(result, InitializeResult)
+            tools = await session.list_tools()
+            assert tools.tools