From 86c5febdd1d31200c6fa982c2e98eb27c116e876 Mon Sep 17 00:00:00 2001
From: teknium1 <127238744+teknium1@users.noreply.github.com>
Date: Tue, 7 Jul 2026 13:23:34 -0700
Subject: [PATCH] fix(mcp): watchdog wrap after OSV preflight + forward SIGTERM
 to child group

Two fixes on top of the salvaged parent-death watchdog:
- Apply the watchdog wrap AFTER the OSV malware preflight so the check
  inspects the real npx/uvx package instead of the python wrapper
  (the wrap previously made the preflight a silent no-op for every
  stdio server).
- The real server runs in its own process group under the watchdog, so
  the graceful-shutdown killpg no longer reached it; the watchdog now
  forwards SIGTERM/SIGINT to the child's group, keeping wedged servers
  killable on clean shutdown.
---
 tools/mcp_stdio_watchdog.py | 13 +++++++++++++
 tools/mcp_tool.py           | 25 +++++++++++++++----------
 2 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/tools/mcp_stdio_watchdog.py b/tools/mcp_stdio_watchdog.py
index 46761c16337..17e6fb4c41c 100644
--- a/tools/mcp_stdio_watchdog.py
+++ b/tools/mcp_stdio_watchdog.py
@@ -138,6 +138,19 @@ def main(argv: list[str] | None = None) -> int:
         start_new_session=True,
     )
 
+    # Because the real server lives in its OWN process group (above), the
+    # parent's graceful-shutdown killpg of *our* group no longer reaches it.
+    # Forward SIGTERM/SIGINT to the child's group so graceful teardown
+    # (`_kill_orphaned_mcp_children`, shutdown sweeps) still kills a wedged
+    # server that ignores stdin EOF — otherwise the watchdog wrap would
+    # invert the bug it fixes.
+    def _forward_shutdown(signum, frame):  # noqa: ARG001
+        _terminate_process_group(proc)
+        sys.exit(128 + signum)
+
+    signal.signal(signal.SIGTERM, _forward_shutdown)
+    signal.signal(signal.SIGINT, _forward_shutdown)
+
     watchdog = threading.Thread(
         target=_watchdog_loop,
         args=(proc, args.ppid, args.create_time),
diff --git a/tools/mcp_tool.py b/tools/mcp_tool.py
index 1d45a079027..5f5726d769b 100644
--- a/tools/mcp_tool.py
+++ b/tools/mcp_tool.py
@@ -1949,21 +1949,14 @@ class MCPServerTask:
         safe_env = _build_safe_env(user_env)
         command, safe_env = _resolve_stdio_command(command, safe_env)
 
-        # Wrap the real command in a parent-death watchdog supervisor so an
-        # ungraceful exit of this Hermes process (kill -9, crash, force-quit)
-        # can't leave the stdio MCP child (and its own descendants, e.g.
-        # mcp-remote's spawned `node`) running forever. On a clean exit,
-        # MCPServerTask.shutdown() / _kill_orphaned_mcp_children() still do
-        # the reaping as before -- this only covers the case where that code
-        # never gets to run. POSIX-only (relies on process groups); no-op
-        # elsewhere, matching existing killpg-based cleanup's platform scope.
-        command, args = _wrap_command_with_watchdog(command, args)
-
         # Check package against OSV malware database before spawning.
         # Run off the event loop (the urllib HTTPS call is blocking) and bound
         # it with a wall-clock timeout so a stalled SSL handshake can't freeze
         # MCP discovery / gateway startup (#29184). The check is fail-open, so
         # on timeout we log and proceed rather than blocking indefinitely.
+        # NOTE: must run against the REAL command/args — the watchdog wrap
+        # below rewrites argv to `python -m tools.mcp_stdio_watchdog …`,
+        # which would silently turn the preflight into a no-op.
         from tools.osv_check import check_package_for_malware
         try:
             malware_error = await asyncio.wait_for(
@@ -1982,6 +1975,18 @@ class MCPServerTask:
                 f"MCP server '{self.name}': {malware_error}"
             )
 
+        # Wrap the real command in a parent-death watchdog supervisor so an
+        # ungraceful exit of this Hermes process (kill -9, crash, force-quit)
+        # can't leave the stdio MCP child (and its own descendants, e.g.
+        # mcp-remote's spawned `node`) running forever. On a clean exit,
+        # MCPServerTask.shutdown() / _kill_orphaned_mcp_children() still do
+        # the reaping as before -- this only covers the case where that code
+        # never gets to run. POSIX-only (relies on process groups); no-op
+        # elsewhere, matching existing killpg-based cleanup's platform scope.
+        # Applied AFTER the OSV preflight so the check inspects the real
+        # package, not the watchdog wrapper.
+        command, args = _wrap_command_with_watchdog(command, args)
+
         server_params = StdioServerParameters(
             command=command,
             args=args,