diff --git a/backend/app/gateway/routers/mcp.py b/backend/app/gateway/routers/mcp.py
index 3e6e9f9588..7c54daba0d 100644
--- a/backend/app/gateway/routers/mcp.py
+++ b/backend/app/gateway/routers/mcp.py
@@ -1,4 +1,5 @@
 import asyncio
+import json
 import logging
 import os
 import re
@@ -793,7 +794,8 @@ def _validate_mcp_update_request(
                 status_code=status.HTTP_400_BAD_REQUEST,
                 detail=(
                     f"Bundled MCP server '{name}' uses a different Python interpreter. "
-                    f"Edit this server's JSON and set 'command' to {sys.executable!r}. "
+                    f"Edit this server's JSON and set 'command' to {json.dumps(sys.executable)} "
+                    f"(raw path for terminal use: {sys.executable}). "
                     "Keep its capability metadata and credentials unchanged to preserve Agent selections; do not delete and reinstall it."
                 ),
             )