diff --git a/main.py b/main.py
index aeb261c..ea19041 100644
--- a/main.py
+++ b/main.py
@@ -623,25 +623,27 @@ def start(self, start_node_id=None):
             raise
 
     def stop(self):
-        if not self.running: return
-        self.stop_event.set()
-        self.pause_event.set()
         with self.thread_lock:
+            if not self.running: return
+            self.stop_event.set()
+            self.pause_event.set()
             self.pending_nodes.clear()
         self.log("🛑 正在停止...", "warning")
         # The engine waits for active workers before allowing another run.
 
     def pause(self):
-        if not self.running or self.stop_event.is_set() or self.paused: return
-        self.paused = True
-        self.pause_event.clear()
+        with self.thread_lock:
+            if not self.running or self.stop_event.is_set() or self.paused: return
+            self.paused = True
+            self.pause_event.clear()
         self.log("⏸️ 流程暂停", "paused")
         self.app.after(0, lambda: self.app.update_debug_btn_state(True))
 
     def resume(self):
-        if not self.running or not self.paused: return
-        self.paused = False
-        self.pause_event.set()
+        with self.thread_lock:
+            if not self.running or not self.paused: return
+            self.paused = False
+            self.pause_event.set()
         self.log("▶️ 流程继续", "info")
         self.app.after(0, lambda: self.app.update_debug_btn_state(False))
     
diff --git a/tests/test_regressions.py b/tests/test_regressions.py
index d6eb280..ddab150 100644
--- a/tests/test_regressions.py
+++ b/tests/test_regressions.py
@@ -71,6 +71,15 @@ def setUpClass(cls):
             "AutomationCore", "start",
             {"threading": threading, "time": time}
         )
+        cls.StopProbe = extract_class_with_method(
+            "AutomationCore", "stop"
+        )
+        cls.PauseProbe = extract_class_with_method(
+            "AutomationCore", "pause"
+        )
+        cls.ResumeProbe = extract_class_with_method(
+            "AutomationCore", "resume"
+        )
         cls.MemorySnapshotProbe = extract_class_with_method(
             "AutomationCore", "_memory_snapshot",
             {"threading": threading}
@@ -204,6 +213,75 @@ def after(self, delay, callback):
         self.assertTrue(engine.pause_event.is_set())
         self.assertEqual(engine.pending_nodes, [])
 
+    def test_stop_atomically_signals_workers_and_discards_queued_nodes(self):
+        import threading
+
+        class Event:
+            def __init__(self, value=False):
+                self.value = value
+            def set(self):
+                self.value = True
+            def clear(self):
+                self.value = False
+            def is_set(self):
+                return self.value
+
+        core = self.StopProbe()
+        core.thread_lock = threading.Lock()
+        core.running = True
+        core.stop_event = Event()
+        core.pause_event = Event(False)
+        core.pending_nodes = ["queued-a", "queued-b"]
+        logs = []
+        core.log = lambda *args: logs.append(args)
+
+        core.stop()
+
+        self.assertTrue(core.stop_event.is_set())
+        self.assertTrue(core.pause_event.is_set())
+        self.assertEqual(core.pending_nodes, [])
+        self.assertEqual(len(logs), 1)
+
+    def test_pause_and_resume_update_state_under_lock(self):
+        import threading
+
+        class Event:
+            def __init__(self, value=False):
+                self.value = value
+            def set(self):
+                self.value = True
+            def clear(self):
+                self.value = False
+            def is_set(self):
+                return self.value
+
+        class App:
+            def __init__(self):
+                self.calls = []
+            def after(self, delay, callback):
+                callback()
+            def update_debug_btn_state(self, paused):
+                self.calls.append(paused)
+
+        core = self.PauseProbe()
+        core.thread_lock = threading.Lock()
+        core.running = True
+        core.paused = False
+        core.stop_event = Event()
+        core.pause_event = Event(True)
+        core.log = lambda *args: None
+        core.app = App()
+        core.resume = self.ResumeProbe.resume.__get__(core, type(core))
+
+        core.pause()
+        self.assertTrue(core.paused)
+        self.assertFalse(core.pause_event.is_set())
+
+        core.resume()
+        self.assertFalse(core.paused)
+        self.assertTrue(core.pause_event.is_set())
+        self.assertEqual(core.app.calls, [True, False])
+
     def test_parallel_stat_updates_do_not_lose_counts(self):
         import threading