fix(light): an unknown WHAT does not keep a state restored at startup

custom_components/myhome/light.py

@@ -372,6 +372,9 @@ def __init__(
             self._attr_icon = self._off_icon
 
         self._attr_is_on = None
+        # True while is_on is only what Home Assistant restored at startup: not
+        # worth keeping against a fault report (an actuator stuck at WHAT 19).
+        self._is_on_restored = False
         self._attr_brightness: int | None = None
         self._attr_brightness_pct: int | None = None
 
@@ -471,8 +474,10 @@ async def async_restore_last_state(self, last_state: State) -> None:
         # 5. Restore power state
         if last_state.state == "on":
             self._attr_is_on = True
+            self._is_on_restored = True
         elif last_state.state == "off":
             self._attr_is_on = False
+            self._is_on_restored = True
 
     async def async_update(self) -> None:
         """Update the entity.
@@ -533,6 +538,7 @@ def _apply_brightness_state(self, pct: int, is_on: bool | None = None) -> None:
             self._attr_is_on = is_on
         else:
             self._attr_is_on = pct > 0
+        self._is_on_restored = False
         if pct > 0:
             self._last_brightness_pct = pct
 
@@ -665,6 +671,7 @@ async def async_turn_on_timed(
         )
         await self._gateway_handler.send(cmd)
         self._attr_is_on = True
+        self._is_on_restored = False
         self.async_write_ha_state()
 
     async def async_turn_on(self, **kwargs: Any) -> None:
@@ -752,6 +759,7 @@ async def async_turn_on(self, **kwargs: Any) -> None:
 
             if ATTR_BRIGHTNESS not in kwargs and ATTR_BRIGHTNESS_PCT not in kwargs:
                 self._attr_is_on = True
+                self._is_on_restored = False
                 if self._attr_brightness is None and self._last_brightness_pct:
                     self._apply_brightness_state(self._last_brightness_pct, is_on=True)
                 self.async_schedule_update_ha_state()
@@ -871,17 +879,24 @@ def handle_event(self, message: OWNLightingEvent) -> None:
         )
         if message.is_on is not None:
             self._attr_is_on = message.is_on
+            self._is_on_restored = False
 
         # A WHAT outside the WHO 1 table (e.g. 19 from an MH200 actuator with a
-        # WHO 1001 fault) leaves is_on None: keep the last state, show the value.
+        # WHO 1001 fault) leaves is_on None: keep a state seen on the bus or set
+        # from Home Assistant, but not one restored at startup - that may be the
+        # "on" a fault left behind before OWNd knew better (light 74, #456).
         unknown_state = getattr(message, "unknown_state", None)
         if isinstance(unknown_state, int):
+            if self._is_on_restored:
+                self._attr_is_on = None
+                self._is_on_restored = False
             if self._attr_extra_state_attributes.get("unknown_state") != unknown_state:
                 LOGGER.warning(
-                    "%s light %s reports unknown lighting WHAT %s; keeping its last state",
+                    "%s light %s reports unknown lighting WHAT %s; %s",
                     self._gateway_handler.log_id,
                     self._full_where,
                     unknown_state,
+                    "its state is unknown" if self._attr_is_on is None else "keeping its last state",
                 )
             self._attr_extra_state_attributes["unknown_state"] = unknown_state
         elif message.is_on is not None:

tests/test_component_light.py

@@ -15,6 +15,7 @@
     LightEntityFeature,
 )
 from homeassistant.const import CONF_NAME
+from homeassistant.core import State
 from homeassistant.helpers.dispatcher import async_dispatcher_send
 from OWNd.message import (
     OWNEvent,
@@ -1841,3 +1842,56 @@ def test_mh200_what_19_reply_does_not_turn_the_light_on(hass):
 
     assert light.is_on is False
     assert light.extra_state_attributes["unknown_state"] == 19
+
+
+def _fault_event(value=19):
+    event = MagicMock(spec=OWNLightingEvent, is_on=None, brightness=None, brightness_preset=None)
+    event.unknown_state = value
+    return event
+
+
+async def test_unknown_state_does_not_keep_a_restored_state(hass, caplog):
+    """A restored "on" may be the one the fault left behind: the next fault report makes it unknown."""
+    light = _unknown_state_light(hass)
+    await light.async_restore_last_state(State("light.light_74", "on"))
+    assert light.is_on is True
+
+    with caplog.at_level(logging.WARNING, logger="custom_components.myhome"):
+        light.handle_event(_fault_event())
+    assert light.is_on is None
+    assert light.state is None  # Home Assistant shows "unknown"
+    assert light.extra_state_attributes["unknown_state"] == 19
+    assert any("its state is unknown" in r.getMessage() for r in caplog.records)
+
+    # the next real state from the bus is taken, and then kept against the fault
+    light.handle_event(MagicMock(spec=OWNLightingEvent, is_on=False, brightness=None, brightness_preset=None))
+    light.handle_event(_fault_event())
+    assert light.is_on is False
+
+
+async def test_unknown_state_keeps_a_state_set_from_home_assistant(hass):
+    light = _unknown_state_light(hass)
+    light.entity_id = "light.light_74"
+    light.async_write_ha_state = MagicMock()
+    light._gateway_handler.send = AsyncMock()
+    await light.async_restore_last_state(State("light.light_74", "off"))
+    await light.async_turn_on_timed(duration=60)
+    light.handle_event(_fault_event())
+    assert light.is_on is True
+
+
+@pytest.mark.xfail(
+    _OWND_WHAT_19_IS_ON,
+    reason="installed OWNd reports lighting WHAT 19 (outside the WHO 1 table) as on",
+    strict=True,
+)
+async def test_mh200_light_74_restored_on_after_the_fix(hass):
+    """Live 2026-09-24 17:16 on the MH200 test build: light.light_74 came back "on" from the
+    state the bug had left, and the bus only ever answered *1*19*74## (+ WHO 1001 DIMENSION 11)."""
+    light = _unknown_state_light(hass)
+    await light.async_restore_last_state(State("light.light_74", "on"))
+
+    light.handle_event(OWNEvent.parse("*1*19*74##"))
+
+    assert light.is_on is None
+    assert light.extra_state_attributes["unknown_state"] == 19