diff --git a/core/key_simulator.py b/core/key_simulator.py
index 766369f..b582dce 100644
--- a/core/key_simulator.py
+++ b/core/key_simulator.py
@@ -555,6 +555,7 @@ def execute_action(action_id):
 # ==================================================================
 
 elif sys.platform == "darwin":
+    _INJECTED_EVENT_MARKER = 0x4D4F5554
     import ctypes
 
     try:
@@ -628,6 +629,13 @@ def inject_scroll(flags, delta):
         else:
             event = Quartz.CGEventCreateScrollWheelEvent(None, 0, 2, 0, delta)
         if event:
+            try:
+                # Mark synthetic scroll events so the CGEventTap can ignore them
+                Quartz.CGEventSetIntegerValueField(
+                    event, Quartz.kCGEventSourceUserData, _INJECTED_EVENT_MARKER
+                )
+            except Exception:
+                pass
             Quartz.CGEventPost(Quartz.kCGHIDEventTap, event)
 
     # Mouse button simulation
@@ -668,6 +676,13 @@ def _inject_mac_mouse(action_id, is_down):
         loc = Quartz.CGEventGetLocation(Quartz.CGEventCreate(None))
         ev = Quartz.CGEventCreateMouseEvent(None, evt_type, loc, entry["button"])
         if ev:
+            try:
+                # Mark synthetic mouse events so the CGEventTap can ignore them
+                Quartz.CGEventSetIntegerValueField(
+                    ev, Quartz.kCGEventSourceUserData, _INJECTED_EVENT_MARKER
+                )
+            except Exception:
+                pass
             Quartz.CGEventPost(Quartz.kCGHIDEventTap, ev)
 
     def inject_mouse_down(action_id):
diff --git a/core/mouse_hook.py b/core/mouse_hook.py
index 3acf0d8..825747c 100644
--- a/core/mouse_hook.py
+++ b/core/mouse_hook.py
@@ -990,6 +990,7 @@ def stop(self):
     _BTN_BACK = 3
     _BTN_FORWARD = 4
     _SCROLL_INVERT_MARKER = 0x4D4F5553
+    _INJECTED_EVENT_MARKER = 0x4D4F5554
     _kCGEventTapDisabledByTimeout = 0xFFFFFFFE
     _kCGEventTapDisabledByUserInput = 0xFFFFFFFF
 
@@ -1379,6 +1380,16 @@ def _event_tap_callback(self, proxy, event_type, cg_event, refcon):
                     self._first_event_logged = True
                     print("[MouseHook] CGEventTap: first event received", flush=True)
 
+                # Ignore events we injected ourselves.  The key_simulator marks
+                # synthetic events by setting kCGEventSourceUserData to _INJECTED_EVENT_MARKER.
+                try:
+                    if Quartz.CGEventGetIntegerValueField(
+                        cg_event, Quartz.kCGEventSourceUserData
+                    ) == _INJECTED_EVENT_MARKER:
+                        return cg_event
+                except Exception:
+                    # If the field isn't available or the call fails, continue.
+                    pass
                 mouse_event = None
                 should_block = False