Timestamp relay changes with a read-only state listener

Polling only sees the relay's current state and last change, so two or
more changes between polls (e.g. an on/off round trip) made the lag
estimate unknown and paused learning for about half an hour.

Subscribe to the relay's state changes (read-only) and integrate every
recorded change between polls. Because HA delivers these events one
loop iteration late, the current state stays authoritative and fills in
a change not yet recorded. Unknown periods (non on/off states, missed
transitions, event overflow) still restart the estimate with an
explicit error bound. Without the listener, behavior is as before.

HA skips unload callbacks after unexpected setup errors, so setup now
removes the listener itself on any failure and registers it for unload
only once setup succeeds.

Tested on HA Core 2025.12.0 and 2026.2.3.

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

custom_components/heating_mpc/coordinator.py

@@ -2,12 +2,13 @@
 from __future__ import annotations
 
 import logging
+from collections import deque
 from datetime import datetime, timedelta, timezone
 from functools import partial
 from math import exp, isfinite
 from typing import Any
 
-from homeassistant.core import HomeAssistant
+from homeassistant.core import Event, HomeAssistant, callback
 from homeassistant.config_entries import ConfigEntry
 from homeassistant.helpers.storage import Store
 from homeassistant.helpers.update_coordinator import DataUpdateCoordinator
@@ -21,11 +22,13 @@ from .const import (
 from .data_quality import freshness
 from .physics import (
     LAG_LEARN_MAX_UNCERTAINTY, LAG_TAU_SECONDS, Learner, advance_lag,
-    lag_from_time_in_state, optimize,
+    lag_from_time_in_state, optimize, relay_segments,
 )
 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
 
 
 class HeatingMPCCoordinator(DataUpdateCoordinator[dict[str, Any]]):
@@ -43,6 +46,9 @@ class HeatingMPCCoordinator(DataUpdateCoordinator[dict[str, Any]]):
         # Radiator-lag proxy at the last poll with a valid relay state. Tracked
         # independently of room sensors so lag survives room outages and transitions.
         self._lag: dict[str, Any] | None = None
+        # (time, new state) of relay changes since the last poll, from a read-only listener.
+        self._relay_events: deque[tuple[datetime, str]] = deque(maxlen=MAX_RELAY_EVENTS)
+        self._relay_events_dropped = False
         self._on_samples = 0
         self._off_samples = 0
 
@@ -79,32 +85,55 @@ class HeatingMPCCoordinator(DataUpdateCoordinator[dict[str, Any]]):
         return freshness(getattr(state, "last_reported", getattr(state, "last_updated", None)),
                          now, limit * 60)
 
+    @callback
+    def async_relay_changed(self, event: Event) -> None:
+        """Record relay state changes as they happen; read-only state listener."""
+        old, new = event.data.get("old_state"), event.data.get("new_state")
+        if new is None:
+            self.record_relay_state(event.time_fired, "removed")
+        elif old is None or old.state != new.state:
+            self.record_relay_state(new.last_changed, new.state)
+
+    def record_relay_state(self, when: datetime, state: str) -> None:
+        if len(self._relay_events) == self._relay_events.maxlen:
+            self._relay_events_dropped = True
+        self._relay_events.append((when, state))
+
     def _track_lag(self, now: datetime, heater_on: bool, last_changed: datetime) -> bool:
         """Advance the lag proxy to `now`; return True if the relay held one state throughout.
 
-        A single relay change since the last poll is integrated at its timestamp.
-        Anything ambiguous (several changes, an outage, clock jumps) restarts the
-        estimate from the time spent in the current state, with an explicit error bound.
+        Relay changes since the last poll are integrated at their timestamps. Anything
+        ambiguous (missed changes, an outage, clock jumps) restarts the estimate from
+        the time spent in the current state, with an explicit error bound.
         """
         tracker = self._lag
         steady = False
         lag = uncertainty = None
-        if tracker is not None:
-            dt = (now - tracker["time"]).total_seconds()
-            if dt > 0 and heater_on == tracker["heater_on"] and last_changed <= tracker["time"]:
-                lag = advance_lag(tracker["lag"], heater_on, dt)
-                steady = True
-            elif dt > 0 and heater_on != tracker["heater_on"] and tracker["time"] < last_changed <= now:
-                before = (last_changed - tracker["time"]).total_seconds()
-                lag = advance_lag(tracker["lag"], tracker["heater_on"], before)
-                lag = advance_lag(lag, heater_on, (now - last_changed).total_seconds())
-            if lag is not None:
+        if tracker is not None and now > tracker["time"]:
+            start = tracker["time"]
+            changes = [(when, state) for when, state in self._relay_events if start < when <= now]
+            # The current state is authoritative; its change event may still be queued,
+            # and without a listener it is the only change visible.
+            if last_changed > start and (not changes or changes[-1][0] < last_changed):
+                changes.append((last_changed, "on" if heater_on else "off"))
+            segments = None if self._relay_events_dropped else relay_segments(
+                tracker["heater_on"], start.timestamp(),
+                [(when.timestamp(), state) for when, state in changes], now.timestamp())
+            if segments is not None and segments[-1][0] == heater_on:
+                lag = tracker["lag"]
+                for command, seconds in segments:
+                    lag = advance_lag(lag, command, seconds)
                 # The lag update is a contraction, so an initial error decays the same way.
-                uncertainty = tracker["uncertainty"] * exp(-dt / LAG_TAU_SECONDS)
+                uncertainty = tracker["uncertainty"] * exp(
+                    -(now - start).total_seconds() / LAG_TAU_SECONDS)
+                steady = len(segments) == 1
         if lag is None:
             lag, uncertainty = lag_from_time_in_state(
                 heater_on, (now - last_changed).total_seconds())
         self._lag = {"time": now, "heater_on": heater_on, "lag": lag, "uncertainty": uncertainty}
+        self._relay_events = deque((e for e in self._relay_events if e[0] > now),
+                                   maxlen=MAX_RELAY_EVENTS)
+        self._relay_events_dropped = False
         return steady
 
     def _prediction_inputs(self) -> tuple:
@@ -191,6 +220,8 @@ class HeatingMPCCoordinator(DataUpdateCoordinator[dict[str, Any]]):
             status["heat_lag_uncertainty"] = round(self._lag["uncertainty"], 3)
         else:
             self._lag = None
+            self._relay_events.clear()
+            self._relay_events_dropped = False
         if (not heater_valid or climate is None or outside is None or
                 any(temp is None for temp in temps.values())):
             self._previous = None