Fix process tree cancellation for tools

tests/test_python_exec_tool.py

@@ -1,7 +1,12 @@
 from __future__ import annotations
 
+import os
+import re
+import signal
+import subprocess
 import sys
 import tempfile
+import time
 from pathlib import Path
 from unittest import TestCase
 
@@ -179,3 +184,54 @@ class PythonExecToolTests(TestCase):
         self.assertTrue(result.ok)
         self.assertIn('a|b', result.content)
         self.assertEqual(result.metadata.get('mode'), 'script')
+
+    def test_python_exec_timeout_kills_spawned_children(self) -> None:
+        if os.name != 'posix':
+            self.skipTest('process group cleanup test is POSIX-only')
+
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            config = AgentRuntimeConfig(
+                cwd=Path(tmp_dir),
+                permissions=AgentPermissions(allow_shell_commands=True),
+            )
+            context = build_tool_context(config)
+            child_code = (
+                'import subprocess, sys, time\n'
+                'child = subprocess.Popen([sys.executable, "-c", "import time; time.sleep(60)"])\n'
+                'print(child.pid, flush=True)\n'
+                'time.sleep(60)\n'
+            )
+            result = execute_tool(
+                default_tool_registry(),
+                'python_exec',
+                {
+                    'code': child_code,
+                    'timeout_seconds': 1,
+                    'max_output_chars': 2000,
+                },
+                context,
+            )
+
+        self.assertTrue(result.ok)
+        self.assertTrue(result.metadata.get('timed_out'))
+        match = re.search(r'\[stdout\]\s*(\d+)', result.content)
+        self.assertIsNotNone(match, result.content)
+        child_pid = int(match.group(1))
+        time.sleep(0.3)
+        if self._pid_is_running(child_pid):
+            try:
+                os.kill(child_pid, signal.SIGKILL)
+            except ProcessLookupError:
+                pass
+            self.fail(f'spawned child process is still running: {child_pid}')
+
+    @staticmethod
+    def _pid_is_running(pid: int) -> bool:
+        status = subprocess.run(
+            ['ps', '-p', str(pid), '-o', 'stat='],
+            capture_output=True,
+            text=True,
+            check=False,
+        )
+        state = status.stdout.strip()
+        return bool(state) and not state.startswith('Z')