Move is_stateless_http_server metadata assignment to the Streamable route from the common metadata method.

gateway/mcp/mcp_sessions_manager.py

@@ -23,7 +23,6 @@ from gateway.integrations.explorer import (
     fetch_guardrails_from_explorer,
 )
 from gateway.integrations.guardrails import check_guardrails
-from gateway.mcp.constants import INVARIANT_SESSION_ID_PREFIX
 
 
 def user_and_host() -> str:
@@ -110,9 +109,6 @@ class McpSession(BaseModel):
             "system_user": user_and_host(),
             **(self.attributes.metadata or {}),
         }
-        metadata["is_stateless_http_server"] = self.session_id.startswith(
-            INVARIANT_SESSION_ID_PREFIX
-        )
         return metadata
 
     async def get_guardrails_check_result(

gateway/mcp/mcp_transport_base.py

@@ -52,7 +52,7 @@ class McpTransportBase(ABC):
         """
         # Update session with request information
         session = self.session_store.get_session(session_id)
-        McpTransportBase.update_session_from_request(session, request_data)
+        self.update_session_from_request(session, request_data)
 
         # Refresh guardrails
         await session.load_guardrails()
@@ -74,7 +74,7 @@ class McpTransportBase(ABC):
         """
         # Update session with server information
         session = self.session_store.get_session(session_id)
-        McpTransportBase.update_mcp_server_in_session_metadata(session, response_data)
+        self.update_mcp_server_in_session_metadata(session, response_data)
 
         # Intercept and apply guardrails to response
         return await McpTransportBase.intercept_response(
@@ -106,11 +106,11 @@ class McpTransportBase(ABC):
         interception_result = request_data
         is_blocked = False
         if method == MCP_TOOL_CALL:
-            interception_result, is_blocked = await McpTransportBase.hook_tool_call(
+            interception_result, is_blocked = await self.hook_tool_call(
                 session_id, self.session_store, request_data
             )
         elif method == MCP_LIST_TOOLS:
-            interception_result, is_blocked = await McpTransportBase.hook_tool_call(
+            interception_result, is_blocked = await self.hook_tool_call(
                 session_id=session_id,
                 session_store=self.session_store,
                 request_body={

gateway/mcp/streamable.py

@@ -27,7 +27,7 @@ CONTENT_TYPE_JSON = "application/json"
 CONTENT_TYPE_SSE = "text/event-stream"
 CONTENT_TYPE_HEADER = "content-type"
 MCP_SESSION_ID_HEADER = "mcp-session-id"
-MCP_SERVER_POST_DELETE_HEADERS = {
+MCP_SERVER_POST_AND_DELETE_HEADERS = {
     "connection",
     "accept",
     CONTENT_TYPE_HEADER,
@@ -392,6 +392,9 @@ class StreamableTransport(McpTransportBase):
         """Update MCP response info in session metadata."""
         session = self.session_store.get_session(session_id)
         self.update_mcp_server_in_session_metadata(session, response_body)
+        session.attributes.metadata["is_stateless_http_server"] = session_id.startswith(
+            INVARIANT_SESSION_ID_PREFIX
+        )
         session.attributes.metadata["server_response_type"] = (
             "json" if is_json_response else "sse"
         )
@@ -402,7 +405,7 @@ class StreamableTransport(McpTransportBase):
         for k, v in request.headers.items():
             if k.startswith(MCP_CUSTOM_HEADER_PREFIX):
                 filtered_headers[k.removeprefix(MCP_CUSTOM_HEADER_PREFIX)] = v
-            if k.lower() in MCP_SERVER_POST_DELETE_HEADERS and not (
+            if k.lower() in MCP_SERVER_POST_AND_DELETE_HEADERS and not (
                 k.lower() == MCP_SESSION_ID_HEADER
                 and v.startswith(INVARIANT_SESSION_ID_PREFIX)
             ):

tests/integration/mcp/test_mcp.py

@@ -2,7 +2,6 @@
 
 import os
 import uuid
-
 from resources.mcp.sse.client.main import run as mcp_sse_client_run
 from resources.mcp.stdio.client.main import run as mcp_stdio_client_run
 from resources.mcp.streamable.client.main import run as mcp_streamable_client_run
@@ -12,8 +11,6 @@ import httpx
 import pytest
 import requests
 
-from mcp.shared.exceptions import McpError
-
 # Taken from docker-compose.test.yml
 MCP_SSE_SERVER_HOST = "mcp-messenger-sse-server"
 MCP_SSE_SERVER_PORT = 8123