@@ -1524,6 +1524,9 @@ python scripts/battery_throughput.py
 
 ## Recent Updates
 
+**2026-06-01**
+- **Fix: crash and blind restart when Solcast drops past periods mid-day.** Two related bugs surfaced when the monitor restarted at 10:38 UTC. (1) The intra-day forecast refresh replaced `today_period_forecast` wholesale with Solcast's 2-period result (Aftn, Eve) while `ordered_period_windows` still held all 3 periods — the coordinator then crashed with `KeyError: 'Morn'`. (2) On restart, `today_period_windows` is empty so the startup flow fell into the intra-day branch, produced `daytime_periods = []`, and fired no handlers for the rest of the day. Fixed by: merging (not replacing) `today_period_forecast` on intra-day refresh; always anchoring window boundaries to the canonical `["Morn","Aftn","Eve"]` triplet on day-reset so windows remain thirds even after a mid-day restart; triggering a day-reset when `ordered_period_windows` is empty at startup; and guarding `_process_period_windows` against any period absent from the forecast.
+
 **2026-05-31**
 - **Fix: export restart blocked after SOC floor hit until SOC recovers.** When a timed export was stopped early by the SOC floor, the 15-minute cooldown previously allowed a restart as soon as it expired — even if SOC had only recovered marginally above the floor. This caused brief oscillating re-exports (e.g. a 3-minute export) that immediately re-hit the floor. A per-period `soc_floor_hit` flag is now set in `day_state` when the SOC floor fires. The period-start export path then requires SOC to recover to `DAYTIME_TIMED_EXPORT_MIN_SOC_PERCENT + TIMED_EXPORT_FLOOR_HIT_RECOVERY_PERCENT` (default 40% + 7.5% = 47.5%) before restarting. The flag is per-period and resets at midnight. Configurable via `TIMED_EXPORT_FLOOR_HIT_RECOVERY_PERCENT` in `settings.py`.
 
 
@@ -160,7 +160,7 @@ async def _handle_auth_refresh(self, now: datetime, today: date) -> None:
 
     async def _handle_forecast_refresh(self, now: datetime, today: date) -> bool:
         """Refresh forecast data if needed. Returns True if the tick should be skipped."""
-        if today != self.state.current_date:
+        if today != self.state.current_date or not self.state.ordered_period_windows:
             self.state.current_date = today
             try:
                 await refresh_daily_data(self.state, self.logger, reset_day_state=True)
@@ -359,6 +359,8 @@ async def _process_period_windows(self, now: datetime, today: date) -> None:
 
         if not night_tick_consumed:
             for period_index, (period, period_start) in enumerate(self.state.ordered_period_windows):
+                if period not in self.state.today_period_forecast:
+                    continue
                 solar_value, status = self.state.today_period_forecast[period]
                 period_end_utc = (
                     self.state.ordered_period_windows[period_index + 1][1]
 
@@ -60,8 +60,15 @@ async def refresh_daily_data(
     logger.info("[SCHEDULER] Refreshing daily forecast and sunrise/sunset data.")
     state.forecast_calibration = build_and_save_forecast_calibration()
     forecast_obj: SolarForecastProvider = create_solar_forecast_provider(logger)
-    state.today_period_forecast = forecast_obj.get_todays_period_forecast()
+    new_today = forecast_obj.get_todays_period_forecast()
     state.tomorrow_period_forecast = forecast_obj.get_tomorrows_period_forecast()
+    if reset_day_state:
+        state.today_period_forecast = new_today
+    else:
+        # Intra-day: merge rather than replace. Solcast stops returning past periods
+        # (e.g. Morn after ~10:00), but today_period_windows still references them;
+        # a full overwrite would cause a KeyError in _process_period_windows.
+        state.today_period_forecast.update(new_today)
     logger.info(f"[SCHEDULER] Today's forecast: {state.today_period_forecast}")
     logger.info(f"[SCHEDULER] Tomorrow's forecast: {state.tomorrow_period_forecast}")
 
@@ -95,17 +102,18 @@ async def refresh_daily_data(
     )
 
     if reset_day_state:
-        # Derive today's period windows from the full 3-period forecast at day start.
-        # Intra-day refreshes must NOT recalculate these: once Morn completes Solcast
-        # stops returning it, so the list shrinks to 2 periods and the windows would
-        # be recalculated as halves instead of thirds, shifting Eve ~3 h too early.
-        daytime_periods = order_daytime_periods(state.today_period_forecast)
-        state.today_period_windows = derive_period_windows(sunrise_utc, sunset_utc, daytime_periods)
+        # Always anchor windows to the full canonical period set. Solcast drops
+        # past periods mid-day, so a mid-day restart would otherwise produce
+        # 2-period windows (halves of the solar day) instead of the correct thirds.
+        # _process_period_windows skips any period absent from today_period_forecast.
+        canonical_periods = ["Morn", "Aftn", "Eve"]
+        state.today_period_windows = derive_period_windows(sunrise_utc, sunset_utc, canonical_periods)
         state.ordered_period_windows = sorted(state.today_period_windows.items(), key=lambda item: item[1])
         state.day_state = {
             p: {"pre_set": False, "start_set": False, "clipping_export_set": False, "high_soc_export_set": False, "soc_floor_hit": False}
-            for p in daytime_periods
+            for p in canonical_periods
         }
+        daytime_periods = canonical_periods
     else:
         daytime_periods = list(state.today_period_windows.keys())
         for period in daytime_periods:
 
@@ -381,3 +381,83 @@ def test_is_pre_sunrise_discharge_window_false_outside_months() -> None:
         months_csv="4,5,6,7,8,9",
         lead_minutes=60,
     ) is False
+
+
+# ---------------------------------------------------------------------------
+# Tests for mid-day restart / Solcast period-drop resilience (2026-06-01 crash)
+# ---------------------------------------------------------------------------
+
+def _make_day_state(periods: list[str]) -> "dict[str, Any]":
+    return {p: {"pre_set": False, "start_set": False, "clipping_export_set": False,
+                "high_soc_export_set": False, "soc_floor_hit": False} for p in periods}
+
+
+def test_refresh_daily_data_intraday_preserves_dropped_periods(tmp_path, monkeypatch) -> None:
+    """Intra-day forecast refresh must merge, not replace, so past periods
+    that Solcast has stopped returning are kept in today_period_forecast.
+    Regression: 2026-06-01 crash KeyError: 'Morn'."""
+    import asyncio
+    from unittest.mock import patch as _patch, MagicMock
+    from datetime import date
+    from logic.scheduler_operations import refresh_daily_data
+    from logic.scheduler_state import SchedulerState
+    from logic.schedule_utils import derive_period_windows
+
+    sunrise = datetime(2026, 6, 1, 4, 5, tzinfo=timezone.utc)
+    sunset = datetime(2026, 6, 1, 20, 51, tzinfo=timezone.utc)
+
+    state = SchedulerState(current_date=date(2026, 6, 1))
+    state.today_period_forecast = {"Morn": (1059, "Red"), "Aftn": (2871, "Amber"), "Eve": (2466, "Amber")}
+    state.today_period_windows = derive_period_windows(sunrise, sunset, ["Morn", "Aftn", "Eve"])
+    state.ordered_period_windows = sorted(state.today_period_windows.items(), key=lambda x: x[1])
+    state.day_state = _make_day_state(["Morn", "Aftn", "Eve"])
+
+    mock_provider = MagicMock()
+    mock_provider.get_todays_period_forecast.return_value = {"Aftn": (2757, "Amber"), "Eve": (2330, "Amber")}
+    mock_provider.get_tomorrows_period_forecast.return_value = {"Morn": (2142, "Amber")}
+
+    with _patch("logic.scheduler_operations.build_and_save_forecast_calibration", return_value={}), \
+         _patch("logic.scheduler_operations.create_solar_forecast_provider", return_value=mock_provider), \
+         _patch("logic.scheduler_operations.get_sunrise_sunset", side_effect=[
+             ("2026-06-01T04:05:14+00:00", "2026-06-01T20:51:26+00:00"),
+             ("2026-06-02T04:04:22+00:00", "2026-06-02T20:52:37+00:00"),
+         ]):
+        asyncio.run(refresh_daily_data(state, _test_logger, reset_day_state=False))
+
+    assert "Morn" in state.today_period_forecast, "Morn must be preserved after intra-day merge"
+    assert state.today_period_forecast["Aftn"] == (2757, "Amber")
+    assert state.today_period_forecast["Eve"] == (2330, "Amber")
+
+
+def test_refresh_daily_data_reset_uses_canonical_period_windows(tmp_path, monkeypatch) -> None:
+    """Day-reset must always compute windows against canonical ['Morn','Aftn','Eve']
+    even when Solcast only returns 2 periods (mid-day restart scenario).
+    Regression: after 2026-06-01 crash, restart left ordered_period_windows=[]."""
+    import asyncio
+    from unittest.mock import patch as _patch, MagicMock
+    from datetime import date
+    from logic.scheduler_operations import refresh_daily_data
+    from logic.scheduler_state import SchedulerState
+
+    state = SchedulerState(current_date=date(2026, 6, 1))
+
+    mock_provider = MagicMock()
+    mock_provider.get_todays_period_forecast.return_value = {"Aftn": (2757, "Amber"), "Eve": (2330, "Amber")}
+    mock_provider.get_tomorrows_period_forecast.return_value = {"Morn": (2142, "Amber"), "Aftn": (4831, "Green"), "Eve": (2455, "Amber")}
+
+    with _patch("logic.scheduler_operations.build_and_save_forecast_calibration", return_value={}), \
+         _patch("logic.scheduler_operations.create_solar_forecast_provider", return_value=mock_provider), \
+         _patch("logic.scheduler_operations.get_sunrise_sunset", side_effect=[
+             ("2026-06-01T04:05:14+00:00", "2026-06-01T20:51:26+00:00"),
+             ("2026-06-02T04:04:22+00:00", "2026-06-02T20:52:37+00:00"),
+         ]):
+        asyncio.run(refresh_daily_data(state, _test_logger, reset_day_state=True))
+
+    assert set(state.today_period_windows.keys()) == {"Morn", "Aftn", "Eve"}
+    assert len(state.ordered_period_windows) == 3
+    assert set(state.day_state.keys()) == {"Morn", "Aftn", "Eve"}
+    # Windows must be thirds of the solar day — Eve start must be > halfway
+    morn_start = state.today_period_windows["Morn"]
+    aftn_start = state.today_period_windows["Aftn"]
+    eve_start = state.today_period_windows["Eve"]
+    assert morn_start < aftn_start < eve_start