diff --git a/black_screen_dim.py b/black_screen_dim.py
index 8bde989..68d3d60 100644
--- a/black_screen_dim.py
+++ b/black_screen_dim.py
@@ -80,16 +80,52 @@ class BrightnessController:
     def _write_native(self, handle, value):
         try:
             dx = ctypes.windll.dxva2
-            return bool(dx.SetMonitorBrightness(int(handle), wt.DWORD(int(value))))
+            res = {}
+
+            def _t():
+                try:
+                    res["v"] = bool(
+                        dx.SetMonitorBrightness(int(handle), wt.DWORD(int(value)))
+                    )
+                except Exception as e:
+                    res["e"] = e
+
+            th = threading.Thread(target=_t, daemon=True)
+            th.start()
+            th.join(timeout=2.0)
+            if th.is_alive():
+                LOG.warning("native SetMonitorBrightness timed out (monitor in standby?)")
+                return False
+            if "e" in res:
+                LOG.warning("native write failed: %r", res["e"])
+                return False
+            return res.get("v", False)
         except Exception as e:
-            LOG.warning("native write failed: %r", e)
+            LOG.warning("native write error: %r", e)
             return False
 
     def _close_native(self, handle):
-        dx = ctypes.windll.dxva2
-        arr = (BrightnessController.PHYSICAL_MONITOR * 1)()
-        arr[0].hPhysicalMonitor = handle
-        dx.DestroyPhysicalMonitors(1, arr)
+        try:
+            dx = ctypes.windll.dxva2
+            arr = (BrightnessController.PHYSICAL_MONITOR * 1)()
+            arr[0].hPhysicalMonitor = handle
+            res = {}
+
+            def _t():
+                try:
+                    res["v"] = dx.DestroyPhysicalMonitors(1, arr)
+                except Exception as e:
+                    res["e"] = e
+
+            th = threading.Thread(target=_t, daemon=True)
+            th.start()
+            th.join(timeout=2.0)
+            if th.is_alive():
+                return
+            if "e" in res:
+                LOG.warning("native close failed: %r", res["e"])
+        except Exception as e:
+            LOG.warning("native close error: %r", e)
 
     def _build(self):
         self.targets = []
@@ -214,6 +250,9 @@ if sys.platform == "win32":
     DT_SINGLELINE = 0x00000020
     TRANSPARENT = 1
     DEFAULT_GUI_FONT = 17
+    ES_CONTINUOUS = 0x80000000
+    ES_SYSTEM_REQUIRED = 0x00000001
+    ES_DISPLAY_REQUIRED = 0x00000002
 
     LRESULT = ctypes.c_int64
     HMONITOR = ctypes.c_void_p
@@ -329,6 +368,8 @@ if sys.platform == "win32":
     kernel32.GetModuleHandleW.restype = wt.HINSTANCE
     kernel32.GetLastError.argtypes = []
     kernel32.GetLastError.restype = wt.DWORD
+    kernel32.SetThreadExecutionState.argtypes = [wt.DWORD]
+    kernel32.SetThreadExecutionState.restype = wt.DWORD
 
     # --- native DDC/CI brightness (dxva2) ---
     class PHYSICAL_MONITOR(ctypes.Structure):
@@ -485,6 +526,13 @@ if sys.platform == "win32":
         if not _hook_id:
             LOG.warning("SetWindowsHookExW failed: %d", kernel32.GetLastError())
 
+        # keep display awake while running: prevents the monitor from entering
+        # standby during idle, which would make the DDC/CI brightness restore on
+        # exit block/hang (often ~30s) waiting for the monitor to wake.
+        kernel32.SetThreadExecutionState(
+            ES_CONTINUOUS | ES_DISPLAY_REQUIRED | ES_SYSTEM_REQUIRED
+        )
+
         msg = wt.MSG()
         while user32.GetMessageW(ctypes.byref(msg), 0, 0, 0) > 0:
             user32.TranslateMessage(ctypes.byref(msg))
@@ -492,6 +540,7 @@ if sys.platform == "win32":
 
         if _hook_id:
             user32.UnhookWindowsHookEx(_hook_id)
+        kernel32.SetThreadExecutionState(ES_CONTINUOUS)  # allow display sleep again
         for h in _hwnds:
             user32.DestroyWindow(h)
         # restore cursor