fix(gateway): reap orphaned gateways before spawning restart (#77276)

_spawn_gateway_restart() now calls _reap_unsupervised_gateway_orphans()
before spawning a new `hermes gateway restart` child.  On desktop-app
restart the old serve exits but its gateway child gets reparented to
launchd (PPID=1) and keeps its platform connection alive.  The new
serve then spawns a fresh gateway, resulting in two live gateways
racing the same connection.

The reap was already implemented for the CLI restart path (#75936) but
the dashboard's _spawn_gateway_restart path was not covered.

Fixes #77276

hermes_cli/web_server.py

@@ -4018,8 +4018,21 @@ def _spawn_gateway_restart(profile: Optional[str] = None) -> Tuple[subprocess.Po
     concurrent ``hermes gateway restart`` children race each other on the
     manual kill-and-start path, so reuse the live one instead.
 
+    Before spawning, sweep for orphaned gateway processes whose parent has
+    exited (e.g. desktop-app restarts leaving a reparented gateway child
+    under launchd/PPID=1).  Without this the orphan keeps its platform
+    connection alive and the fresh gateway stacks a duplicate (#77276).
+
     Returns ``(proc, reused)``.
     """
+    # Reap orphaned gateways before spawning a new one (#77276).
+    try:
+        from hermes_cli.gateway import _reap_unsupervised_gateway_orphans
+
+        _reap_unsupervised_gateway_orphans()
+    except Exception:
+        pass  # best-effort — don't block the restart on a reap failure
+
     subcommand = _gateway_subcommand(profile, "restart")
     existing = _ACTION_PROCS.get("gateway-restart")
     if existing is not None and existing.poll() is None:

tests/hermes_cli/test_spawn_gateway_restart_reap.py

@@ -0,0 +1,52 @@
+"""Tests for _spawn_gateway_restart orphan-reap guard (#77276)."""
+from __future__ import annotations
+
+import subprocess
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+
+class TestSpawnGatewayRestartReapsOrphans:
+    """_spawn_gateway_restart must reap orphaned gateways before spawning."""
+
+    @patch("hermes_cli.web_server._gateway_subcommand", return_value=["gateway", "restart"])
+    @patch("hermes_cli.web_server._spawn_hermes_action")
+    @patch("hermes_cli.web_server._ACTION_PROCS", {})
+    def test_reap_called_before_spawn(self, mock_spawn, mock_subcmd):
+        """Orphan reap runs before the new gateway process is spawned."""
+        mock_proc = MagicMock(spec=subprocess.Popen)
+        mock_proc.poll.return_value = None
+        mock_spawn.return_value = mock_proc
+
+        from hermes_cli.web_server import _spawn_gateway_restart
+
+        with patch(
+            "hermes_cli.gateway._reap_unsupervised_gateway_orphans"
+        ) as mock_reap:
+            proc, reused = _spawn_gateway_restart()
+
+        mock_reap.assert_called_once()
+        mock_spawn.assert_called_once()
+        assert proc is mock_proc
+        assert reused is False
+
+    @patch("hermes_cli.web_server._gateway_subcommand", return_value=["gateway", "restart"])
+    @patch("hermes_cli.web_server._spawn_hermes_action")
+    @patch("hermes_cli.web_server._ACTION_PROCS", {})
+    def test_reap_failure_does_not_block_spawn(self, mock_spawn, mock_subcmd):
+        """If reap raises, the restart still proceeds."""
+        mock_proc = MagicMock(spec=subprocess.Popen)
+        mock_proc.poll.return_value = None
+        mock_spawn.return_value = mock_proc
+
+        from hermes_cli.web_server import _spawn_gateway_restart
+
+        with patch(
+            "hermes_cli.gateway._reap_unsupervised_gateway_orphans",
+            side_effect=OSError("permission denied"),
+        ):
+            proc, reused = _spawn_gateway_restart()
+
+        mock_spawn.assert_called_once()
+        assert proc is mock_proc