diff --git a/custom_components/hotata/config_flow.py b/custom_components/hotata/config_flow.py
index 5efd98e..57065a9 100644
--- a/custom_components/hotata/config_flow.py
+++ b/custom_components/hotata/config_flow.py
@@ -143,6 +143,12 @@ async def async_step_user(
                                 CONF_DESCENT_TIME, DEFAULT_DESCENT_TIME
                             )
                         ),
+                        CONF_BACKUP_USERNAME: user_input.get(
+                            CONF_BACKUP_USERNAME, ""
+                        ).strip(),
+                        CONF_BACKUP_PASSWORD: user_input.get(
+                            CONF_BACKUP_PASSWORD, ""
+                        ),
                         **creds,
                     },
                 )
@@ -154,6 +160,8 @@ async def async_step_user(
                 vol.Required(
                     CONF_DESCENT_TIME, default=DEFAULT_DESCENT_TIME
                 ): vol.All(vol.Coerce(int), vol.Range(min=0, max=20)),
+                vol.Optional(CONF_BACKUP_USERNAME): str,
+                vol.Optional(CONF_BACKUP_PASSWORD): str,
             }
         )
         return self.async_show_form(
diff --git a/custom_components/hotata/hub.py b/custom_components/hotata/hub.py
index 3a0bdf2..63bb7ad 100644
--- a/custom_components/hotata/hub.py
+++ b/custom_components/hotata/hub.py
@@ -477,10 +477,10 @@ async def _switch_back_to_primary(self) -> bool:
             if not self._using_backup:
                 return False
             try:
-                # Probe: account-level read (listBindings). A fresh IoT
-                # credential does NOT lift a throttled account's penalty,
-                # so verify with a real request before switching.
-                await self._primary_api.async_list_devices()
+                # Round 1: account-level read. A fresh IoT credential
+                # does NOT lift a throttled account's penalty, so
+                # verify the account is free before trying devices.
+                devices = await self._primary_api.async_list_devices()
             except HotataRateLimited:
                 self._primary_penalty_until = (
                     time.time() + SWITCH_BACK_PROBE_DELAY
@@ -488,11 +488,9 @@ async def _switch_back_to_primary(self) -> bool:
                 self._switch_back_failures += 1
                 self._async_save_runtime_state()
                 self._schedule_switch_back()
-                _LOGGER.info("Primary still rate-limited, staying on backup")
+                _LOGGER.info("Primary still rate-limited (account probe), staying on backup")
                 return False
             except HotataAuthError as err:
-                # Credentials rejected — refresh was already attempted inside
-                # the client; retry later on the probe schedule.
                 self._switch_back_failures += 1
                 self._schedule_switch_back()
                 _LOGGER.warning("Primary probe auth failed: %s", err)
@@ -500,9 +498,54 @@ async def _switch_back_to_primary(self) -> bool:
             except HotataError as err:
                 self._switch_back_failures += 1
                 self._schedule_switch_back()
-                _LOGGER.warning("Primary probe failed: %s", err)
+                _LOGGER.warning("Primary account probe failed: %s", err)
                 return False
-            # Probe OK — activate the primary identity.
+
+            # Round 2: device-level probe. Account probe alone may pass
+            # when throttling only applies to device-level requests.
+            # Query properties of the first discovered device — this is
+            # the same heavy request the coordinator polls with, so if
+            # it 403s here we know the primary is still unfit for
+            # real traffic and we keep the backup.
+            if devices:
+                try:
+                    await self._primary_api.async_get_properties(
+                        devices[0].iot_id
+                    )
+                except HotataRateLimited:
+                    self._primary_penalty_until = (
+                        time.time() + SWITCH_BACK_PROBE_DELAY
+                    )
+                    self._switch_back_failures += 1
+                    self._async_save_runtime_state()
+                    self._schedule_switch_back()
+                    _LOGGER.info(
+                        "Primary still rate-limited (device probe on %s), "
+                        "staying on backup",
+                        devices[0].iot_id,
+                    )
+                    return False
+                except HotataAuthError as err:
+                    self._switch_back_failures += 1
+                    self._schedule_switch_back()
+                    _LOGGER.warning(
+                        "Primary device probe auth failed on %s: %s",
+                        devices[0].iot_id,
+                        err,
+                    )
+                    return False
+                except HotataError as err:
+                    self._switch_back_failures += 1
+                    self._schedule_switch_back()
+                    _LOGGER.warning(
+                        "Primary device probe failed on %s: %s",
+                        devices[0].iot_id,
+                        err,
+                    )
+                    return False
+
+            # Heavy probe OK — the primary account can actually serve
+            # real traffic. Activate the primary identity.
             self._using_backup = False
             self._primary_penalty_until = 0.0
             self._switch_back_failures = 0
diff --git a/custom_components/hotata/manifest.json b/custom_components/hotata/manifest.json
index 71dbbbe..abc0a8d 100644
--- a/custom_components/hotata/manifest.json
+++ b/custom_components/hotata/manifest.json
@@ -12,5 +12,6 @@
   "requirements": [
     "cryptography>=42.0.0"
   ],
-  "version": "4.0.1"
+  "version": "4.0.2"
 }
+
diff --git a/custom_components/hotata/sensor.py b/custom_components/hotata/sensor.py
index 41c35d8..d5c201d 100644
--- a/custom_components/hotata/sensor.py
+++ b/custom_components/hotata/sensor.py
@@ -108,7 +108,7 @@ def _sensor(
     ),
     _sensor(
         "DeviceModelType",
-        "设备型号",
+        "机型功能配置",
         value_map={
             0: "照明、消毒、风干、烘干",
             1: "照明",