diff --git a/tests/unit/mcp/test_mcp_tools.py b/tests/unit/mcp/test_mcp_tools.py
index 0064ed9a..6535fd1f 100644
--- a/tests/unit/mcp/test_mcp_tools.py
+++ b/tests/unit/mcp/test_mcp_tools.py
@@ -31,6 +31,7 @@
     mobile_manage_task,
     mobile_run_task,
 )
+from mcp_server.tools import task_runner
 from artemis.runtime import trace_store
 
 
@@ -43,6 +44,31 @@ def temp_trace_env(monkeypatch):
     shutil.rmtree(temp_dir, ignore_errors=True)
 
 
+@pytest.fixture(autouse=True)
+def stub_spawn_watchdog(monkeypatch):
+    """Record watchdog launches instead of starting real daemon threads.
+
+    `mobile_run_task` arms `_start_spawn_watchdog` after `Popen` returns.
+    These tests mock `Popen`, so the watchdog would monitor a PID that is a
+    MagicMock attribute and outlive both `temp_trace_env`'s directory and its
+    monkeypatches. Past its deadline it goes on to terminate a process tree,
+    cancel a reservation, write into the restored trace directory and dispatch
+    failure notifications -- for tasks that never existed.
+
+    Production watchdog behaviour is covered on its own in
+    `tests/unit/mcp/test_spawn_watchdog.py`, so nothing is lost here.
+
+    Yields the recorded `(trace_id, pid, queue_ticket, conversation_id)` calls.
+    """
+    calls: list[tuple] = []
+    monkeypatch.setattr(
+        task_runner,
+        "_start_spawn_watchdog",
+        lambda *args: calls.append(args),
+    )
+    return calls
+
+
 def test_tool_signatures():
     # mobile_run_task signature check
     sig_run = inspect.signature(mobile_run_task)
@@ -88,7 +114,9 @@ def test_mobile_run_task_invalid_model():
         mobile_run_task(task_desc="test", conversation_id="conv-1", model="invalid_model")
 
 
-def test_mobile_run_task_reserves_and_passes_global_queue_ticket(temp_trace_env):
+def test_mobile_run_task_reserves_and_passes_global_queue_ticket(
+    temp_trace_env, stub_spawn_watchdog
+):
     process = MagicMock(pid=43210)
     with (
         patch(
@@ -119,9 +147,11 @@ def test_mobile_run_task_reserves_and_passes_global_queue_ticket(temp_trace_env)
     status = trace_store.read_status(result["trace_id"])
     assert status["queue_ticket"] == "queue-ticket-1"
     assert status["device_serial"] is None
+    # The watchdog is armed for this dispatch, with this task's identity.
+    assert stub_spawn_watchdog == [(result["trace_id"], 43210, "queue-ticket-1", "conv-1")]
 
 
-def test_mobile_run_task_with_device_serial(temp_trace_env):
+def test_mobile_run_task_with_device_serial(temp_trace_env, stub_spawn_watchdog):
     process = MagicMock(pid=54321)
     with (
         patch(
@@ -167,6 +197,9 @@ def test_mobile_run_task_with_device_serial(temp_trace_env):
 
     status = trace_store.read_status(result["trace_id"])
     assert status["device_serial"] == "pixel-11-pro-001"
+    # The watchdog is armed with the mocked runner's pid and this dispatch's
+    # ticket, not with whatever process happens to own that pid on the host.
+    assert stub_spawn_watchdog == [(result["trace_id"], 54321, "queue-ticket-dev", "conv-2")]
 
 
 def test_mobile_run_task_dispatched_to_daemon(temp_trace_env, monkeypatch):