Update metadata in MCP SSE similar to what we do in MCP stdio.

gateway/common/mcp_sessions_manager.py

@@ -2,8 +2,10 @@
 
 import asyncio
 import contextlib
+import getpass
 import os
 import random
+import socket
 
 from typing import Any, Dict, List, Optional
 
@@ -24,6 +26,14 @@ from gateway.integrations.guardrails import check_guardrails
 DEFAULT_API_URL = "https://explorer.invariantlabs.ai"
 
 
+def user_and_host() -> str:
+    """Get the current user and hostname."""
+    username = getpass.getuser()
+    hostname = socket.gethostname()
+
+    return f"{username}@{hostname}"
+
+
 class McpSession(BaseModel):
     """
     Represents a single MCP session.
@@ -81,6 +91,14 @@ class McpSession(BaseModel):
         async with self._lock:
             yield
 
+    def session_metadata(self) -> dict:
+        """Generate metadata for the current session."""
+        return {
+            "session_id": self.session_id,
+            "system_user": user_and_host(),
+            **(self.metadata or {}),
+        }
+
     async def get_guardrails_check_result(
         self,
         message: dict,
@@ -102,6 +120,10 @@ class McpSession(BaseModel):
             dataset_name=self.explorer_dataset,
             invariant_authorization="Bearer " + os.getenv("INVARIANT_API_KEY"),
             guardrails=self.guardrails,
+            guardrails_parameters={
+                "metadata": self.session_metadata(),
+                "action": action,
+            },
         )
 
         guardrails_to_check = (
@@ -170,12 +192,10 @@ class McpSession(BaseModel):
 
             # If no trace exists, create a new one
             if not self.trace_id:
-                # pylint: disable=no-member
-                metadata = {"source": "mcp", "tools": self.metadata.get("tools", [])}
-                if self.metadata.get("mcp_client_name"):
-                    metadata["mcp_client"] = self.metadata.get("mcp_client_name")
-                if self.metadata.get("mcp_server_name"):
-                    metadata["mcp_server"] = self.metadata.get("mcp_server_name")
+                # default metadata
+                metadata = {"source": "mcp"}
+                # include MCP session metadata
+                metadata.update(self.session_metadata())
 
                 response = await client.push_trace(
                     PushTracesRequest(

gateway/routes/mcp_sse.py

@@ -89,7 +89,7 @@ async def mcp_post_gateway(
     if request_json.get(MCP_PARAMS) and request_json.get(MCP_PARAMS).get(
         MCP_CLIENT_INFO
     ):
-        session.metadata["mcp_client_name"] = (
+        session.metadata["mcp_client"] = (
             request_json.get(MCP_PARAMS).get(MCP_CLIENT_INFO).get("name", "")
         )
 
@@ -446,10 +446,6 @@ def _convert_localhost_to_docker_host(mcp_server_base_url: str) -> str:
     Returns:
         str: Modified server address with localhost references changed to host.docker.internal
     """
-    # check if we are running in a docker container
-    if not os.environ.get("DOCKER_ENV"):
-        return mcp_server_base_url
-
     if "localhost" in mcp_server_base_url or "127.0.0.1" in mcp_server_base_url:
         # Replace localhost or 127.0.0.1 with host.docker.internal
         modified_address = re.sub(
@@ -510,7 +506,7 @@ async def _handle_message_event(session_id: str, sse: ServerSentEvent) -> bytes:
         if response_json.get(MCP_RESULT) and response_json.get(MCP_RESULT).get(
             MCP_SERVER_INFO
         ):
-            session.metadata["mcp_server_name"] = (
+            session.metadata["mcp_server"] = (
                 response_json.get(MCP_RESULT).get(MCP_SERVER_INFO).get("name", "")
             )
 

tests/integration/mcp/test_mcp.py

@@ -174,6 +174,8 @@ async def test_mcp_with_gateway_and_logging_guardrails(
         and metadata["mcp_client"] == "mcp"
         and metadata["mcp_server"] == "messenger_server"
     )
+    assert "session_id" in metadata
+    assert "system_user" in metadata
     assert trace["messages"][2]["role"] == "assistant"
     assert trace["messages"][2]["tool_calls"][0]["function"] == {
         "name": "get_last_message_from_user",
@@ -287,6 +289,8 @@ async def test_mcp_with_gateway_and_blocking_guardrails(
         and metadata["mcp_client"] == "mcp"
         and metadata["mcp_server"] == "messenger_server"
     )
+    assert "session_id" in metadata
+    assert "system_user" in metadata
     assert trace["messages"][2]["role"] == "assistant"
     assert trace["messages"][2]["tool_calls"][0]["function"] == {
         "name": "get_last_message_from_user",
@@ -388,6 +392,8 @@ async def test_mcp_with_gateway_hybrid_guardrails(
         and metadata["mcp_client"] == "mcp"
         and metadata["mcp_server"] == "messenger_server"
     )
+    assert "session_id" in metadata
+    assert "system_user" in metadata
     assert trace["messages"][2]["role"] == "assistant"
     assert trace["messages"][2]["tool_calls"][0]["function"] == {
         "name": "get_last_message_from_user",
@@ -475,4 +481,4 @@ async def test_mcp_tool_list_blocking(
     assert "blocked_get_last_message_from_user" in str(tools_result), (
         "Expected the tool names to be renamed and blocked because of the blocking guardrail on the tools/list call. Instead got: "
         + str(tools_result)
-    )
+    )