Kill engine process groups on trial cleanup

tests/test_core_flow.py

@@ -16,7 +16,7 @@ from aituner.slo import RequestOutcome, summarize_evaluations
 from aituner.spec import Proposal, StudyState, TrialSummary, load_study_spec
 from aituner.store import StudyStore
 from aituner.trace import load_trace_requests, summarize_window
-from aituner.worker import _replay_requests, _wait_for_server_or_exit
+from aituner.worker import _replay_requests, _terminate_process_tree, _wait_for_server_or_exit
 from aituner.trace import TraceRequest
 
 
@@ -910,6 +910,17 @@ class CoreFlowTests(unittest.TestCase):
                 ready_timeout_s=10.0,
             )
 
+    def test_terminate_process_tree_kills_process_group(self) -> None:
+        process = mock.Mock()
+        process.pid = 1234
+        process.poll.side_effect = [None, None, 0]
+        process.wait.return_value = 0
+        with mock.patch("aituner.worker.os.getpgid", return_value=1234):
+            with mock.patch("aituner.worker.os.killpg") as mock_killpg:
+                _terminate_process_tree(process, timeout_s=1.0)
+        mock_killpg.assert_called_once()
+        self.assertEqual(mock_killpg.call_args[0][0], 1234)
+
     def test_openai_url_avoids_double_v1(self) -> None:
         self.assertEqual(
             _openai_url("http://example.com", "/v1/chat/completions"),