Keep models of rooms removed in Options

Saving wrote only the currently configured rooms, so removing a room in
Configure (even by accident) discarded its learned model at the next
save, and adding it back started from scratch.

Keep validated models of removed rooms (at most 24, oldest dropped
first) in an optional retired_learners payload key and restore them when
the room is added back. Payload schema_version stays 2: the key is
additive and older 0.2.x readers ignore it. Replacing the relay still
starts a fresh model, as before. Status lists retired_room_models.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

custom_components/heating_mpc/coordinator.py

@@ -29,6 +29,8 @@ from .weather_sources import choose_weather_sources, sources_for, normalize
 _LOGGER = logging.getLogger(__name__)
 # Relay changes kept between polls; more than this in five minutes is chatter.
 MAX_RELAY_EVENTS = 256
+# Models of rooms removed in Options, kept in case a room is added back.
+MAX_RETIRED_ROOMS = 24
 
 
 class HeatingMPCCoordinator(DataUpdateCoordinator[dict[str, Any]]):
@@ -41,6 +43,7 @@ class HeatingMPCCoordinator(DataUpdateCoordinator[dict[str, Any]]):
         self.config = {**DEFAULTS, **entry.data, **entry.options}
         self.rooms: list[str] = self.config[CONF_ROOMS]
         self.learners: dict[str, Learner] = {room: Learner() for room in self.rooms}
+        self._retired: dict[str, dict[str, Any]] = {}
         self._store = Store(hass, 1, f"{DOMAIN}.{entry.entry_id}")
         self._previous: dict[str, Any] | None = None
         # Radiator-lag proxy at the last poll with a valid relay state. Tracked
@@ -62,13 +65,23 @@ class HeatingMPCCoordinator(DataUpdateCoordinator[dict[str, Any]]):
         if stored.get("heater_entity", self.config[CONF_HEATER]) != self.config[CONF_HEATER]:
             _LOGGER.warning("Heating MPC heater changed; starting a fresh thermal model")
             return
-        # Models carry room identity, so changing the room list is safe.
-        saved = stored.get("learners", {})
-        if not isinstance(saved, dict):
-            return
-        for room, data in saved.items():
-            if room in self.learners:
-                self.learners[room] = Learner.from_dict(data)
+        # Models carry room identity, so changing the room list is safe. Models of
+        # rooms no longer configured are retained, most recently removed last.
+        for key in ("retired_learners", "learners"):  # current learners take precedence
+            saved = stored.get(key)
+            if not isinstance(saved, dict):
+                continue
+            for room, data in saved.items():
+                if not isinstance(room, str):
+                    continue
+                learner = Learner.from_dict(data)
+                if room in self.learners:
+                    self.learners[room] = learner
+                elif learner.count:
+                    self._retired.pop(room, None)
+                    self._retired[room] = learner.as_dict()
+        while len(self._retired) > MAX_RETIRED_ROOMS:
+            self._retired.pop(next(iter(self._retired)))
         self._update_counts()
 
     def _update_counts(self) -> None:
@@ -210,6 +223,7 @@ class HeatingMPCCoordinator(DataUpdateCoordinator[dict[str, Any]]):
             "weather_active_sources": {k: v for k, v in active_sources.items() if v},
             "weather_comparison": {k: v for k, v in weather_comparisons.items() if v},
             "weather_model_inputs": ["temperature"],
+            "retired_room_models": sorted(self._retired),
         }
         heater_valid = heater is not None and heater.state in ("on", "off")
         heater_on = heater_valid and heater.state == "on"
@@ -256,6 +270,8 @@ class HeatingMPCCoordinator(DataUpdateCoordinator[dict[str, Any]]):
                 await self._store.async_save({
                     "schema_version": 2,
                     "learners": {room: learner.as_dict() for room, learner in self.learners.items()},
+                    # Optional; older 0.2.x readers ignore it and keep working.
+                    "retired_learners": self._retired,
                     "on_samples": self._on_samples, "off_samples": self._off_samples,
                     "heater_entity": self.config[CONF_HEATER],
                     "outside_source": active_sources["temperature"],