OPT-34 round 3: the latch ends on time, with the run, with the mode, and with the night

- F1: an expired latch is dropped whatever the run state; plan_targets() and the
  store loader ignore one that has ended (no stale latch after a restart).
- F2: the "charge goes on" line only while a cheap run is on.
- F3: a battery that is off or no longer Leftover solar leaves the latch.
- F4: a run carries the latch on only if it starts by the bell start (06:00
  local) after the latch began (manager's call, 2026-10-31).
Tests: test_opt34 scenarios stale/stale_live and part 5; test_modes_p4 asks at a
moment inside the latch.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Bdqr7PiaHcBnzPituu2yTC

goodwe_controller/CHANGELOG.md

@@ -5,8 +5,9 @@
 ### Not in a release yet
 
 - The night grid charge no longer raises "Battery stopped limiting the peak" when the 15-minute period stays on the aim. A steadily rising load now alarms a little later, and with a peak margin of 0 a period can end up to 10 W over the limit without this alarm ([[SAFETY-126]]).
+- A night grid charge for *Leftover solar* no longer stops at 03:00 when the solar forecast sensors went quiet in the evening. The evening's figure is used until 06:00, and a charge that has started goes on to its level ([[OPT-34]]).
 
-**A patch bump: one fix for charging from the grid under the peak limit, and no option changes.**
+**A patch bump: two fixes, one for charging from the grid under the peak limit and one for the night charge of Leftover solar, and no option changes.**
 No option was added, removed or renamed, and no default changed (86 options).
 **Existing installs need no option change:** options that start 0.19.1 also
 start 0.19.2. The change below applies with one inverter or two.

goodwe_controller/DECISIONS/OPT-27-last-fresh-forecast-for-the-night.md

@@ -19,14 +19,16 @@ still keeps a run under way when a read is lost.
 **The rule** (`Hold.stand_in()`). A kept reading is for one day. It covers a
 sensor that is missing or stale, never one with a bad value or unit, and:
 - for up to `FRESH_S` when the sensor is missing: a short outage, any time of day;
-- from the end of the bell (20:00 local, `BELL_TO_H`) until local midnight + 3 h
-  (`KEPT_UNTIL_H`), if the reading is at most `KEPT_MAX_AGE_S` (12 h) old when used;
+- from the end of the bell (20:00 local, `BELL_TO_H`) until local midnight, if the
+  reading is at most `KEPT_MAX_AGE_S` (12 h) old when used; after midnight the
+  tomorrow figure is today's until the bell starts (06:00), up to 15 h old
+  (OPT-34 changed this from midnight + 3 h);
 - the day it is for: a today figure only on that day, a tomorrow figure as
   tomorrow until midnight and, if the today sensors are still stale, as today's
-  until midnight + 3 h (all sensors of the sum are needed, as for any sum);
+  until 06:00 (all sensors of the sum are needed, as for any sum);
 - until the next fresh reading, which replaces it at once.
 
-So a figure is never used for another day and never older than 12 hours (`KEPT_MAX_AGE_S`): a 17:05 reading serves until 03:00 (9 h 55 min), a 09:05 reading only until 21:05.
+So a figure is never used for another day and never older than 12 hours (`KEPT_MAX_AGE_S`), except the morning case above: a 17:05 reading serves until 06:00 (12 h 55 min), a 09:05 reading only until 21:05. Until OPT-34 the figure ended at 03:00, and a charge under way lost its level there; OPT-34 closes that limit.
 Daytime is as before: a sensor that stopped is stale after 3 h, and no forecast
 all day is still no forecast (the night run still needs 1.5x).
 

goodwe_controller/DECISIONS/OPT-34-the-night-charge-keeps-its-level.md

@@ -0,0 +1,62 @@
+# OPT-34 - the night charge keeps its level when the kept forecast ends
+
+**Status: done on `release/1.0`, not released.** Tests: `test_opt34.py`.
+
+**The defect** (OPT-27 rig test, F-1). The kept evening figure ended at midnight + 3 h.
+With the sensors silent from 17:05 the Leftover solar battery's level went with
+it in the middle of the charge: A ended at 49.8 % against 79.9 % with a fresh
+figure. Whether Forecast.Solar refreshes after midnight on a live site is not
+known, so the add-on does not depend on it.
+
+**The rule.**
+1. *A charge under way keeps its level* (`Controller._latch_charge()`). While
+   there is a forecast (fresh or kept), each battery that charges from the grid in the
+   cheap run takes its planned level into a latch (store key `night_charge_latch`).
+   With no forecast, `plan_targets()` gives the latched level, and the wide
+   no-forecast gap does not refuse the next slice of the run (`weather_held()`,
+   as TARIFF-24 does for the run under way). While a
+   forecast is there the latch follows the plan, up or down as a fresh figure moves
+   it. It lasts through every cheap run on and one price slot after the last, and it
+   ends at once when its end time passes, whatever the run state (it is also
+   ignored at a restart if it has ended). A battery that is switched off or
+   changed to another mode leaves it.
+   *Night bound (manager's call, 2026-10-31):* a run carries the latch on only if
+   it starts by the bell start (06:00 local) after the latch began; that run
+   finishes, plus one slot. Chosen over a fixed 12 h because the night tariff
+   (22:00-07:00) needs the 06:00-07:00 slice and 12 h from a late start would
+   reach into the day. With dynamic prices a chain of cheap slots cannot carry a
+   night's level into the next day.
+2. *The evening's tomorrow figure is today's until the bell starts*, 06:00 local
+   (`BELL_FROM_H`, `solarfc._bell_start()`), not until midnight + 3 h.
+   Nothing has been produced yet, so it is still the whole day.
+3. *Up to 15 h old for that case only* (`KEPT_MORNING_MAX_AGE_S`): a 17:05
+   reading is 12 h 55 min old at 06:00. It must have been at most 12 h old at
+   midnight, so a 09:05 reading, unusable since 21:05, does not come back for five
+   minutes after midnight. Same-day figures and the daytime rule keep 12 h and 3 h.
+4. A fresh figure replaces the kept one at once, as before.
+
+**Step 1 alone is enough for the owner's shape, steps 2-3 are still needed.**
+With the window put back to midnight + 3 h the owner's night still ends as a
+fresh figure ends it (A 86.9 %, B 95.0 %), because the charge had started at
+22:00. But a charge that has not started by 03:00 (the price dips at 04:00, or
+the headroom is taken) has no level to latch: A ends at 38 % against 78 %. The
+plan, the screens and a restart also need the figure itself.
+
+**Screens.** "Solar forecast read {at}, kept for tonight." is still true until
+06:00 and unchanged. After the figure ends, with a charge still going on: "No
+solar forecast now. The charge under way goes on to its planned level." /
+"Nu geen zonneprognose. De lopende lading gaat door tot het geplande niveau."
+(`home_words.solar.latched`, only while a cheap run is on and a latched battery is below its level).
+
+**Not used.** A figure over 15 h old; a morning figure at night (12 h); a figure
+for another day; a bad value or unit; and no latch for a charge that has not
+started, for a battery that is not charging, or after the cheap runs have ended
+(plus one slot).
+
+**Not changed.** Charge sizing, the peak guard, Cheap hours, modes off, arbitrage.
+A fresh figure that LOWERS the level during a charge still lowers it, as before.
+
+**Mutants** (all red in `test_opt34.py`): no latch; window back to midnight + 3 h;
+15 h without a limit; no "usable at midnight" rule; the latch without the narrow
+gap, without its save, or not kept through the next run; the window 6 h after
+midnight instead of 06:00 local (DST); 15 h cut to 12 h; the new screen line off or shown without a cheap run; no expiry check; no pruning of a changed mode; no night bound; a left-the-plan battery keeping its level.

goodwe_controller/DOCS.md

@@ -557,7 +557,7 @@ With battery modes on, these choices replace the *Charging and selling on price*
 - The plan is checked every 15 minutes. A planned level moves only by 1 kWh or 10 %, so a wobbling forecast does not flip it.
 - No forecast, one older than 3 hours or from before midnight, or no house use yet: *Leftover solar* takes solar only and *Cheap hours only* fills to the top level. The Batteries screen says so.
 - A battery needs its capacity (`inverters.capacity_kwh`) for a plan.
-- **At night.** Some forecasts stop updating in the evening (Forecast.Solar does). The add-on keeps the last reading of each sensor and uses it for that night's plan: from 20:00 until 03:00, or until a newer reading comes. A sensor that is missing for up to 3 hours is covered the same way. A figure is never used for another day, and never when it is more than 12 hours old. The Batteries screen says "Solar forecast read 17:05, kept for tonight." With no reading all day, the night run still needs the wider gap.
+- **At night.** Some forecasts stop updating in the evening (Forecast.Solar does). The add-on keeps the last reading of each sensor and uses it for that night's plan: from 20:00 until 06:00, or until a newer reading comes. After midnight the evening's figure for tomorrow is today's, whole, because nothing has been produced yet. A sensor that is missing for up to 3 hours is covered the same way. A figure is never used for another day, and never when it is more than 12 hours old (15 hours after midnight, for a figure that was still in use at midnight). A charge from the grid that has started keeps its level when the forecast ends, and goes on to it; the Batteries screen says so. The Batteries screen says "Solar forecast read 17:05, kept for tonight." With no reading all day, the night run still needs the wider gap.
 
 **What always comes first.**
 - The peak limit, the safety stops and the monthly cycle come before a battery's mode.

goodwe_controller/app/homeview.py

@@ -535,15 +535,29 @@ def plan_cover(c, name):
     return targets[name], max(0.0, top - floor) / 100.0 * cap * EFF
 
 
+def _latched_below(c) -> bool:
+    """OPT-34: no forecast, but a cheap run is on and a battery is still below
+    the level its night charge keeps (`Controller.plan_targets()`), so control
+    goes on charging."""
+    rp = getattr(c, "mode_runs", None)
+    if rp is None or rp.cheap is None or not rp.cheap.holds(
+            datetime.now(timezone.utc)):
+        return False
+    targets = getattr(c, "plan_targets", lambda: None)() or {}
+    return any(inv.soc is not None and inv.name in targets
+               and inv.soc < targets[inv.name] for inv in c.inverters)
+
+
 def plan_state(c):
     """P4: `"plan"` (a day plan is made), `"learning"` (no house profile
-    yet), `"no_forecast"` (set but missing or stale), or None (not set, or
-    battery modes off)."""
+    yet), `"no_forecast"` (set but missing or stale), `"latched"` (OPT-34:
+    the same, but a night charge under way is still going on to its level),
+    or None (not set, or battery modes off)."""
     if not getattr(c, "modes_on", False) or \
             getattr(c, "fc_entity", None) is None:
         return None
     if getattr(c, "solar_fc", None) is None:
-        return "no_forecast"
+        return "latched" if _latched_below(c) else "no_forecast"
     hp = getattr(c, "house_profile", None)
     if hp is not None and not hp.ready():
         return "learning"
@@ -564,7 +578,7 @@ def solar_block(c, now):
         out.update(fc_kwh=round(fc.today.kwh, 1),
                    count_kwh=round(fc.today.kwh * trust, 1),
                    updated=hhmm(fc.at))
-    if st in ("no_forecast", "learning"):
+    if st in ("no_forecast", "learning", "latched"):
         out["line"] = _t("solar." + st)
     elif fc is not None:
         out["line"] = line_solar(fc.today.kwh, out["count_kwh"],
@@ -1642,7 +1656,8 @@ def _samples() -> list:
                                kwh="9.4 kWh")) for k in words["why"]]
     out += [("plan", today_words(k)) for k in words["today"]]
     out += [("plan", line_solar(9.2, 6.4, "10:15")),
-            ("plan", _t("solar.no_forecast")), ("plan", _t("solar.learning"))]
+            ("plan", _t("solar.no_forecast")), ("plan", _t("solar.learning")),
+            ("plan", _t("solar.latched"))]
     out += [("plan", day_note(k, pct=70, name="Battery A", at="08:15",
                               kwh="9.2 kWh", count="6.4 kWh"))
             for k in words["day"]]

goodwe_controller/app/main.py

@@ -211,9 +211,41 @@ HOUSE_PROFILE_KEY = "house_profile"
 # OPT-27: the forecast sensors' last fresh readings (`solarfc.Hold`), so an
 # evening restart keeps the figure the night plan uses.
 FC_HOLD_KEY = "solar_fc_hold"
+# OPT-34: the level of a night grid charge that has started, so it does not
+# drop when the forecast goes (`Controller._latch_charge()`).
+CHARGE_LATCH_KEY = "night_charge_latch"
+# OPT-34: a latch outlives the cheap run it was last used in by one price
+# slot, because the next run is planned at the slot edge, in the cycle after
+# the old one ended.
+CHARGE_LATCH_GRACE_S = 900.0
 FORECAST_READ_S = 60.0
 
 
+def _load_latch(data, now=None):
+    """`(until, {name: level %}, born)` from the store, or None if it is not a
+    well-formed latch or has ended (OPT-34)."""
+    try:
+        until = datetime.fromisoformat(data["until"])
+        born = datetime.fromisoformat(data.get("born") or data["until"])
+        levels = {str(n): float(v) for n, v in data["levels"].items()}
+    except (TypeError, KeyError, ValueError, AttributeError):
+        return None
+    if until.tzinfo is None or born.tzinfo is None or not levels or not all(
+            math.isfinite(v) and 0.0 <= v <= 100.0 for v in levels.values()):
+        return None
+    if now is not None and now >= until:
+        return None
+    return until, levels, born
+
+
+def _night_limit(born):
+    """OPT-34: a run that starts after this cannot carry the latch on: the
+    first bell start (`solarfc.BELL_FROM_H`, local) after `born`."""
+    d0, d1 = solarfc._bounds(born)
+    bell = solarfc._bell_start(d0)
+    return bell if bell > born else solarfc._bell_start(d1)
+
+
 def why_raised(resolution, claims) -> bool:
     """F2 (OPT-11 P1 test): did the limit that bound the site target push it
     ABOVE what the winner asked (the peak floor asking for more power)? Then
@@ -1005,6 +1037,10 @@ class Controller:
             (getattr(store, "data", None) or {}).get(FC_HOLD_KEY))
         self.day_plan = None
         self._plan_targets = None
+        # OPT-34: `(until, {name: level %})` of a night charge under way.
+        self._charge_latch = _load_latch(
+            (getattr(store, "data", None) or {}).get(CHARGE_LATCH_KEY),
+            datetime.now(timezone.utc))
         self.house_profile = None
         if self.fc_entity is not None:
             self.house_profile = dayplan.HouseProfile(
@@ -2265,9 +2301,13 @@ class Controller:
     def weather_held(self, now) -> bool:
         """TARIFF-24: no forecast now, but a run planned with one is under
         way: it keeps its gap to its end. The wider gap applies from the next
-        run. Pure; Home asks the same (`homeview.trade_verdict()`)."""
-        return (self.solar_fc is None and self._wx_free_to is not None
-                and now < self._wx_free_to)
+        run. OPT-34: a night charge that keeps its level (`_latch_charge()`)
+        keeps the gap too, run after run, or the next slice of it would be
+        refused. Pure; Home asks the same (`homeview.trade_verdict()`)."""
+        return self.solar_fc is None and (
+            (self._wx_free_to is not None and now < self._wx_free_to)
+            or (self._charge_latch is not None
+                and now < self._charge_latch[0]))
 
     def _price_runs(self, now, packs, floor_pct, ceiling_pct):
         """The kept run plan, rebuilt at most once per price slot (15 min) or
@@ -2352,11 +2392,73 @@ class Controller:
 
     def plan_targets(self):
         """P4: each battery's planned level, or None (no day plan). Dropped
-        at once when the forecast goes (stale or missing)."""
+        at once when the forecast goes (stale or missing), except the level
+        of a night charge that has started (OPT-34): it keeps that level."""
         if self.solar_fc is None:
-            return None
+            lt = self._charge_latch
+            if lt is None or datetime.now(timezone.utc) >= lt[0]:
+                return None
+            return dict(lt[1])
         return self._plan_targets
 
+    def _latch_charge(self, now, runs, targets, packs=None) -> None:
+        """OPT-34, once per cycle after `modetrade.decide()`. A night grid
+        charge that has started keeps its planned level when the forecast goes
+        mid-charge (the kept figure ends and the sensors are still silent).
+
+        While there is a forecast, fresh or kept, the latch is rebuilt each
+        cycle from the plan: a battery that charges from the grid in the cheap
+        run comes in with its planned level, and stays in it at whatever level
+        the plan gives it, up or down as a fresh figure moves it (also when it
+        has stopped, at a lowered level), until it leaves the plan. While there
+        is none, `plan_targets()` gives the latched levels, so the charge goes
+        on to them, and `weather_held()` keeps the narrow price gap. The latch
+        lasts through every cheap run on and one price slot after the last
+        (`CHARGE_LATCH_GRACE_S`), but a run is carried on only if it starts
+        by the bell start of the night the latch began in (`_night_limit()`;
+        the run under way then finishes). It is dropped when `now` passes its
+        end whatever the run state, and a battery that is off or no longer in
+        a mode with a planned level (`packs`) leaves it. A charge that never
+        started has none."""
+        old = lt = self._charge_latch
+        tick = self.mode_tick
+        run = None if runs is None else runs.cheap
+        in_run = run is not None and run.holds(now)
+        grace = timedelta(seconds=CHARGE_LATCH_GRACE_S)
+        if lt is not None and now >= lt[0]:
+            lt = None
+        if lt is not None and packs is not None:
+            ok = {p.name for p in packs
+                  if p.use and p.mode in packmode.PLAN_CHARGE_MODES}
+            lv = {n: v for n, v in lt[1].items() if n in ok}
+            lt = (lt[0], lv, lt[2]) if lv else None
+        # A run may carry the latch on only if it starts by the night's bell.
+        carry = in_run and (lt is None or run.start <= _night_limit(lt[2]))
+        if in_run and self.solar_fc is not None:
+            # Rebuilt from the plan: a battery already latched follows its
+            # level up or down whatever its role this tick (a fresh figure may
+            # lower it below the SoC), one that left the plan is dropped, and
+            # a new one comes in only while it charges from the grid.
+            tg = targets or {}
+            lv = {n: float(tg[n]) for n in (lt[1] if lt else {}) if n in tg}
+            if tick is not None and tick.action == modetrade.CHARGE:
+                lv.update({n: float(tg[n]) for n, r in tick.roles.items()
+                           if r == modetrade.CHARGE and n in tg})
+            if not lv:
+                lt = None
+            elif lt is None:
+                lt = (run.end + grace, lv, now)
+            else:
+                lt = (max(run.end + grace, lt[0]) if carry else lt[0], lv,
+                      lt[2])
+        elif lt is not None and carry:
+            lt = (max(lt[0], run.end + grace), lt[1], lt[2])
+        if lt != old:
+            self._charge_latch = lt
+            self.store.set(CHARGE_LATCH_KEY, None if lt is None else {
+                "until": lt[0].isoformat(), "levels": lt[1],
+                "born": lt[2].isoformat()})
+
     def _mode_roles(self, now, maint_results):
         """OPT-11 P3: each battery's role and range this tick. Grid charging
         and selling need a fresh plan that `TariffPlan.arbitrage()` allows
@@ -2429,6 +2531,7 @@ class Controller:
             blocked=self._charge_blocked_q == quarter,
             done_charge=done_c, done_sell=done_s, targets=targets,
             draining=any(r.phase == DRAIN for r in maint_results or ()))
+        self._latch_charge(now, runs, targets, packs)
         # A charge the guard or the headroom stopped stays off this period.
         # OPT-15: only a MEASURED stop latches; the first unmeasured headroom
         # (None) in a quarter stops this tick only, so a gap cannot cost the

goodwe_controller/app/solarfc.py

@@ -34,11 +34,13 @@ evening and api.forecast.solar is sometimes out for a poll. A kept reading
 stands in for its sensor (a) for up to `FRESH_S` when the sensor is missing
 or unavailable, as a sensor that merely stopped updating is already
 tolerated, and (b) from the end of the bell (`BELL_TO_H`) until local
-midnight + `KEPT_UNTIL_H`, if it is at most `KEPT_MAX_AGE_S` old when used.
-Never beyond that, and never
-for another day: a today figure is only today's, a tomorrow figure is
-tomorrow's until midnight and then, until midnight + 3 h, today's.
-DECISIONS/OPT-27-last-fresh-forecast-for-the-night.md.
+midnight, if it is at most `KEPT_MAX_AGE_S` old when used.
+Never beyond that, and never for another day: a today figure is only today's,
+a tomorrow figure is tomorrow's until midnight and then, until the bell starts
+(`BELL_FROM_H`, 06:00 local), today's (OPT-34: at most `KEPT_MORNING_MAX_AGE_S`
+old, and it must have been usable at midnight).
+DECISIONS/OPT-27-last-fresh-forecast-for-the-night.md,
+DECISIONS/OPT-34-the-night-charge-keeps-its-level.md.
 
 OPT-17: each day may instead name a list (`pv_forecast_entities`,
 `pv_forecast_tomorrow_entities`), summed by `read_sum()`. One member that is
@@ -63,11 +65,16 @@ FRESH_S = 3 * 3600.0
 BELL_FROM_H, BELL_TO_H = 6.0, 20.0
 
 # OPT-27: a kept reading serves the night plan from the end of the bell until
-# this many hours after local midnight (the card: "local midnight + 3 h").
-KEPT_UNTIL_H = 3.0
-# OPT-27: and a reading older than this when used is not kept (a morning
-# figure must not drive the night).
+# local midnight, and a reading older than this when used is not kept (a
+# morning figure must not drive the night).
 KEPT_MAX_AGE_S = 12 * 3600.0
+# OPT-34: the evening's "tomorrow" figure, once midnight has passed, is today's
+# until the bell starts (`BELL_FROM_H`): nothing has been produced yet, so it
+# is still the whole day. A 17:05 reading is 12 h 55 min old at 06:00, so this
+# case may be older than `KEPT_MAX_AGE_S`, up to this, but only a figure that
+# was usable at midnight (at most `KEPT_MAX_AGE_S` old then), so one that has
+# not been used all evening does not come back at 00:00.
+KEPT_MORNING_MAX_AGE_S = 15 * 3600.0
 SAVE_EVERY_S = 900.0
 
 # Why there is no forecast (the page words are in ui_text `home_words`).
@@ -279,7 +286,7 @@ class Hold:
     `day0`) or "tomorrow" (all of `day0`), and `day0` is the day the figure is
     FOR. A today figure therefore never answers for another day, and a
     tomorrow figure answers for its own day only: tomorrow until midnight,
-    then today until midnight + `KEPT_UNTIL_H`. Only the newest reading of a
+    then today until the bell starts (OPT-34). Only the newest reading of a
     key is kept, so the next fresh reading ends the hold at once.
 
     `dump()` / `load()` are what the controller keeps in its store, so an
@@ -322,25 +329,27 @@ class Hold:
 
         The kept reading must be for `day0`, and either (a) at most `FRESH_S`
         old, or (b) used at night: from the end of the bell to local midnight,
-        or within `KEPT_UNTIL_H` after it, and then at most `KEPT_MAX_AGE_S`
-        old. `kept` is true when (b) was needed,
-        or `as_today` (a tomorrow figure standing in for today, after
-        midnight)."""
+        at most `KEPT_MAX_AGE_S` old. `kept` is true when (b) was needed,
+        or `as_today` (OPT-34: a tomorrow figure standing in for today, after
+        midnight and until the bell starts, `KEPT_MORNING_MAX_AGE_S`)."""
         rec = self._r.get((kind, entity, day0))
         if rec is None:
             return None
         day, at = rec
-        if (now - at).total_seconds() <= FRESH_S and not as_today:
+        age = (now - at).total_seconds()
+        if age <= FRESH_S and not as_today:
             return day, at, False
-        if (now - at).total_seconds() > KEPT_MAX_AGE_S:
-            return None
-        # Both sides: a tomorrow sensor is asked with day0 = the next
-        # midnight, which is in the future all day (round 2).
-        after_midnight = day0 <= now < day0 + timedelta(hours=KEPT_UNTIL_H)
-        evening = _local_hour(now) >= BELL_TO_H and now < _bounds(day0)[1]
         if as_today:
-            return (day, at, True) if after_midnight else None
-        return (day, at, True) if (evening or after_midnight) else None
+            ok = (day0 <= now < _bell_start(day0)
+                  and age <= KEPT_MORNING_MAX_AGE_S
+                  and (day0 - at).total_seconds() <= KEPT_MAX_AGE_S)
+            return (day, at, True) if ok else None
+        if age > KEPT_MAX_AGE_S:
+            return None
+        # A tomorrow sensor is asked with day0 = the next midnight, which is
+        # in the future all day, so the evening ends at that day's end.
+        evening = _local_hour(now) >= BELL_TO_H and now < _bounds(day0)[1]
+        return (day, at, True) if evening else None
 
     def dump(self) -> dict:
         return {"v": 1, "r": [
@@ -395,6 +404,15 @@ def _bounds(now):
     return d0.astimezone(timezone.utc), d1.astimezone(timezone.utc)
 
 
+def _bell_start(day0):
+    """The moment the bell starts on the local day that begins at `day0`
+    (`BELL_FROM_H` local, so 06:00 on a 23 h or 25 h day too)."""
+    here = day0.astimezone(BILLING_TZ)
+    t = datetime(here.year, here.month, here.day, tzinfo=BILLING_TZ) \
+        + timedelta(hours=BELL_FROM_H)
+    return t.astimezone(timezone.utc)
+
+
 def _today(state, day0, now):
     """`(Day, at, None)` or `(None, None, why)` for one today sensor."""
     today, why = _day(state, day0, now, today=True)
@@ -474,7 +492,7 @@ def read_sum(today, tomorrow, now: datetime, hold: Hold | None = None):
     where `Hold.stand_in()` allows it (the forecast then has `kept` set when
     that took a reading older than `FRESH_S`). After midnight, if the today
     side is still short, the tomorrow figures read before midnight are
-    today's, until midnight + `KEPT_UNTIL_H`. Without a `hold` this is
+    today's, until the bell starts (`stand_in()`). Without a `hold` this is
     exactly as before."""
     if not today:
         return None, NOT_SET, ()

goodwe_controller/app/ui_text/en.json

@@ -360,7 +360,7 @@
       "tops_up": "It charges from the grid to {pct}. That covers {kwh} of expensive hours the sun will not.",
       "no_forecast": "No solar forecast, so it charges from solar only."
     },
-    "solar": {"line": "Solar still to come today: {kwh}, we count on {count}. Updated {at}.", "uncovered": "The expensive hours need more than Leftover solar can hold. The rest, {kwh}, comes from another battery or the grid.", "kept": "Solar forecast read {at}, kept for tonight.", "no_forecast": "No solar forecast now, so Leftover solar charges from solar only.", "learning": "The add-on is learning your house's use. The plan starts after one full day."},
+    "solar": {"line": "Solar still to come today: {kwh}, we count on {count}. Updated {at}.", "uncovered": "The expensive hours need more than Leftover solar can hold. The rest, {kwh}, comes from another battery or the grid.", "kept": "Solar forecast read {at}, kept for tonight.", "no_forecast": "No solar forecast now, so Leftover solar charges from solar only.", "latched": "No solar forecast now. The charge under way goes on to its planned level.", "learning": "The add-on is learning your house's use. The plan starts after one full day."},
     "today": {
       "not_planned": "Not planned yet.",
       "no_runs": "No cheap or expensive hours left today.",

goodwe_controller/app/ui_text/nl.json

@@ -300,7 +300,7 @@
       "tops_up": "Ze laadt van het net tot {pct}. Dat dekt {kwh} dat de zon in dure uren niet levert.",
       "no_forecast": "Geen zonneprognose, dus ze laadt alleen met zonne-energie."
     },
-    "solar": {"line": "Nog verwachte zon vandaag: {kwh}, we rekenen op {count}. Bijgewerkt om {at}.", "uncovered": "De dure uren vragen meer dan Overschot zonne-energie kan opslaan. De rest, {kwh}, komt van een andere batterij of het net.", "kept": "Zonneprognose van {at}, bewaard voor vannacht.", "no_forecast": "Nu geen zonneprognose, dus Overschot zonne-energie laadt alleen met zon.", "learning": "De add-on leert eerst het verbruik van uw huis. Het plan start na één volle dag."},
+    "solar": {"line": "Nog verwachte zon vandaag: {kwh}, we rekenen op {count}. Bijgewerkt om {at}.", "uncovered": "De dure uren vragen meer dan Overschot zonne-energie kan opslaan. De rest, {kwh}, komt van een andere batterij of het net.", "kept": "Zonneprognose van {at}, bewaard voor vannacht.", "no_forecast": "Nu geen zonneprognose, dus Overschot zonne-energie laadt alleen met zon.", "latched": "Nu geen zonneprognose. De lopende lading gaat door tot het geplande niveau.", "learning": "De add-on leert eerst het verbruik van uw huis. Het plan start na één volle dag."},
     "today": {
       "not_planned": "Nog niet gepland.",
       "no_runs": "Vandaag geen goedkope of dure uren meer.",

goodwe_controller/test_modes_p4.py

@@ -671,7 +671,9 @@ check("Cheap hours with a sun forecast charges as with none (P3)",
       charge and abs(max(r["soc"]["b"] for r in rows_nf) - top) < 1.0
       and top > 80.0)
 
-# The forecast goes away mid-run: Leftover solar stops at once (P3 option A).
+# The forecast goes away mid-run: a charge under way goes on to its level
+# (OPT-34; it stopped at once, P3 option A, before). With no charge under way
+# the levels go with the forecast (below, and test_opt27.py).
 # OPT-27: a sensor that is unavailable is covered by its last fresh reading
 # for up to 3 h (`solarfc.Hold`), so "lost" here is a hold that never covers;
 # the next scenario is the same loss with the hold (test_opt27.py).
@@ -695,8 +697,9 @@ before = [r for r in rows if r["now"] < DROP and r["action"]
           == arbitrage.CHARGE]
 late = [r for r in rows if r["now"] > DROP + timedelta(
     seconds=2 * 60 + 10) and r["action"] == arbitrage.CHARGE]
-check("forecast lost mid-run: Leftover solar was charging, and stops within "
-      "a forecast read (60 s) and a cycle", before and not late)
+check("forecast lost mid-run (OPT-34): Leftover solar was charging, and goes "
+      "on charging past a forecast read (60 s) and a cycle, to its level",
+      before and late)
 rows, st_, c = run_day(SF_LS, fc=lambda now: 1.0 if now < DROP else None,
                        soc0={"a": 60.0, "b": 10.0})
 invariants("forecast unavailable mid-run, covered", rows, c)
@@ -798,12 +801,25 @@ _m1 = c._run_mark("charge", _run, _packs, lambda p: True, ((B, 40.0),))
 _m2 = c._run_mark("charge", _run, _packs, lambda p: False, ((B, 50.0),))
 check("a level the hysteresis moved opens the run to that battery again",
       _m1 and not _m2)
+latch, c._charge_latch = c._charge_latch, None
 c.solar_fc = None
-check("the levels are dropped as soon as the forecast goes, even before "
-      "the plan is rebuilt", c._plan_targets and c.plan_targets() is None)
+check("with no charge under way, the levels are dropped as soon as the "
+      "forecast goes, even before the plan is rebuilt",
+      c._plan_targets and c.plan_targets() is None)
 check("a lost forecast says so: no forecast, Leftover solar solar only",
       homeview.solar_block(c, datetime.now(timezone.utc))["state"]
       == "no_forecast" and homeview.day_key(c, B) == "no_forecast")
+c._charge_latch = latch
+# the latch ends at its end time; this replay ran in September, so ask at a
+# moment inside it
+_real_dt = rp.m.datetime
+rp.m.datetime = type("_DT", (datetime,), {"now": classmethod(
+    lambda cls, tz=None: latch[0] - timedelta(hours=1))})
+check("OPT-34: with a charge under way (B charged in this run), the level "
+      "stays: plan_targets() gives it (the line: test_opt34.py)",
+      latch is not None and c.plan_targets() is not None
+      and B in c.plan_targets() and c.plan_targets()[B] == c._plan_targets[B])
+rp.m.datetime = _real_dt
 check("the Why line wins over 'saves its power' only while holding",
       homeview.battery_why(modes_on=True, mode="leftover_solar", off=False,
                            reading=True, phase="idle", shadow=False,

goodwe_controller/test_opt27.py

@@ -7,9 +7,10 @@ Forecast.Solar site was "no forecast": a price mode's night cheap run needed
 fresh reading of each sensor, for the day it is FOR:
 
 * up to `FRESH_S` when the sensor is missing or unavailable (a short outage);
-* from the end of the bell (20:00) until local midnight + 3 h, if the reading
-  is at most `KEPT_MAX_AGE_S` (12 h) old when used (the night plan); never
-  beyond, never for another day.
+* from the end of the bell (20:00) until local midnight, if the reading is at
+  most `KEPT_MAX_AGE_S` (12 h) old when used (the night plan); after midnight
+  the evening's tomorrow figure is today's until the bell starts (06:00, OPT-34,
+  test_opt34.py); never beyond, never for another day.
 
 DECISIONS/OPT-27-last-fresh-forecast-for-the-night.md.
 
@@ -21,7 +22,7 @@ DECISIONS/OPT-27-last-fresh-forecast-for-the-night.md.
    b. no forecast all day: the night run still needs 1.5x and does not charge;
    c. an evening restart keeps it (a new Controller on the saved store);
    d. a one-hour outage at 18:47 does not drop it;
-   e. past midnight + 3 h the figure is not used, before it it is.
+   e. from 06:00 (the bell) the figure is not used, before it it is (OPT-34).
 3. The screens: the forecast line says when it was read and that it is kept
    for tonight (EN and NL), and Home agrees with control.
 
@@ -153,7 +154,7 @@ for label, tm in (("stale", st(12.0, at(4, 9, 5))), ("unavailable", GONE)):
     check(f"11:00, tomorrow {label} for under 3 h: still covered, not kept",
           fs is not None and fs.tomorrow is not None and not fs.kept)
 
-# The bound: midnight + 3 h, and the day a figure is for.
+# The bound: the bell start (06:00), and the day a figure is for.
 fm = rs(st(0.0, at(3, 23, 0)), st(0.0, at(3, 23, 0)), at(4, 1, 0), h2)[0]
 check("00:30 is covered by the 18:05 tomorrow figure, as TODAY's",
       rs(GONE, GONE, at(4, 0, 30), h2)[0] is not None)
@@ -165,9 +166,12 @@ check("02:59: tomorrow's 12.0 kWh is now today's, there is no tomorrow",
 check("... its sun is counted on the day it is for (06:00-20:00 on the 4th)",
       fmid is not None and fmid.between(at(4, 3, 0), at(4, 7, 0)) is not None
       and fmid.between(at(4, 3, 0), at(4, 7, 0)) > 0.0)
-check("03:01 (midnight + 3 h): not used any more",
-      rs(GONE, GONE, at(4, 3, 1), h2)[0] is None)
-check("... and not the next evening either (past midnight + 3 h)",
+check("03:01: still used (OPT-34: until the bell starts at 06:00)",
+      rs(GONE, GONE, at(4, 3, 1), h2)[0] is not None
+      and rs(GONE, GONE, at(4, 5, 59), h2)[0] is not None)
+check("06:00 (the bell starts): not used any more",
+      rs(GONE, GONE, at(4, 6, 0), h2)[0] is None)
+check("... and not the next evening either (past 06:00)",
       rs(GONE, GONE, at(4, 22, 0), h2)[0] is None)
 fe = rs(st(0.1, at(4, 21, 50)), GONE, at(4, 22, 0), h2)[0]
 check("... the next evening, with today fresh and tomorrow's sensor down, "
@@ -268,11 +272,16 @@ hy = solarfc.Hold()
 rs(st(0.4, at(3, 17, 5)), st(12.0, at(3, 17, 5)), at(3, 17, 10), hy)
 check("F1: a 17:05 reading is kept at 22:00 (5 h) ...",
       (lambda f: f is not None and f.kept)(rs(GONE, GONE, at(3, 22, 0), hy)[0]))
-check("... and at 02:59 next day (9 h 54 min), the midnight + 3 h bound ...",
+check("... and at 02:59 next day (9 h 54 min) ...",
       (lambda f: f is not None and f.kept)(rs(GONE, GONE, at(4, 2, 59),
                                               hy)[0]))
-check("... and at 03:00 next day it is not (midnight + 3 h; 9 h 55 min old)",
-      rs(GONE, GONE, at(4, 3, 0), hy)[0] is None)
+check("... and at 03:00 and 05:59 next day (OPT-34: the bell starts at 06:00)",
+      (lambda f: f is not None and f.kept)(rs(GONE, GONE, at(4, 3, 0),
+                                              hy)[0])
+      and (lambda f: f is not None and f.kept)(rs(GONE, GONE, at(4, 5, 59),
+                                                  hy)[0]))
+check("... and at 06:00 it is not (12 h 55 min old, the bell has started)",
+      rs(GONE, GONE, at(4, 6, 0), hy)[0] is None)
 hm = solarfc.Hold()
 rs(st(0.9, at(3, 9, 5)), st(12.0, at(3, 9, 5)), at(3, 9, 10), hm)
 check("F1: a 09:05 reading is kept at 20:00 (10 h 55 min) but not at 22:00",
@@ -564,18 +573,18 @@ check("... and the 22:00 night run is planned and charges",
       present(ld) and ld["runs_on"] is True
       and sum(r["charging"] for r in rd) > len(rd) // 2)
 
-# e. the bound: midnight + 3 h
+# e. the bound: until the bell starts (06:00, OPT-34; it was midnight + 3 h)
 mid = [at(DAY3, 16, 0) + timedelta(minutes=30 * i) for i in range(12)]
-ce, re_, pe = drive27(opts(), stops_at(LAST), pre=mid + [at(4, 2, 30)],
-                      start=at(4, 2, 30))
+ce, re_, pe = drive27(opts(), stops_at(LAST), pre=mid + [at(4, 5, 30)],
+                      start=at(4, 5, 30))
 le = nth(re_, -1, "last cycle")
-check("02:30 (before midnight + 3 h): the figure from 17:05 is still used, "
+check("05:30 (before the bell starts): the figure from 17:05 is still used, "
       "as today's; the night run is planned",
       present(le) and le["kept"] and le["runs_on"] is True)
-cf, rf, pf = drive27(opts(), stops_at(LAST), pre=mid + [at(4, 3, 30)],
-                     start=at(4, 3, 30))
+cf, rf, pf = drive27(opts(), stops_at(LAST), pre=mid + [at(4, 6, 30)],
+                     start=at(4, 6, 30))
 lf = nth(rf, -1, "last cycle")
-check("03:30 (after midnight + 3 h): a figure from before the night is not "
+check("06:30 (the bell has started): a figure from before the night is not "
       "used: no forecast, 1.5x, not worth, no charge",
       present(lf) and lf["fc_none"] and lf["runs_on"] is False
       and lf["reason"] == "not_worth" and not any(r["charging"] for r in rf))

goodwe_controller/test_opt34.py

@@ -0,0 +1,747 @@
+"""Runnable check for OPT-34.  `python3 test_opt34.py`
+
+OPT-27 keeps the last fresh Forecast.Solar figure over the night. With the
+sensors silent from 17:05 it ended at local midnight + 3 h, in the middle of the
+night grid charge: Leftover solar's planned level went with it and the charge
+stopped (rig, 2026-10-31: battery A 49.8 % at 07:00 against 79.9 % with a fresh
+figure). Forecast.Solar may not refresh after midnight on a live site, so the
+add-on must not depend on it. OPT-34:
+
+1. a night charge that has started keeps its planned level when the forecast
+   goes (`Controller._latch_charge()`), and the next slice of the run is planned
+   with it (the wide no-forecast gap does not refuse it);
+2. the evening's "tomorrow" figure is today's until the bell starts (06:00
+   local, `BELL_FROM_H`) instead of until midnight + 3 h;
+3. for that case only, a reading may be up to 15 h old (a 17:05 reading is
+   12 h 55 min old at 06:00), but only if it was at most 12 h old at midnight;
+4. a fresh figure replaces the kept one at once.
+
+DECISIONS/OPT-34-the-night-charge-keeps-its-level.md.
+
+Mutations (MUTATION.md, purged copies, graded over this file): see the
+DECISIONS note and the dev report.
+
+1. `solarfc` alone: the window, the age limits, the day, DST, restart.
+2. The real Controller, the owner's shape (modes on, arbitrage off, A Leftover
+   solar + B Cheap hours, both 10 % at the start of the night, the night rate
+   22:00-07:00, tomorrow 6 kWh, a 2.5 kW peak limit so the charge takes hours),
+   sensors silent from 17:05, whole nights at 5 s per cycle (run in parallel
+   processes, about 2.5 minutes each):
+   a. silent from 17:05: both batteries end the night where a fresh figure
+      ends them (the base left A at 57 % against 87 %), and the screens agree;
+   b. restarts at 01:00 and 04:00 change nothing;
+   c. a charge that cannot start before 03:00 (the price dips at 04:00) still
+      starts at 04:00 on the kept figure;
+   d. a fresh figure at 02:00 replaces the level at once, up, during the charge;
+      and before a charge has started, up and down;
+   e. the last hour, after the kept figure has ended at 06:00: the charge under
+      way goes on to its level, also over a restart; the screens say so.
+3. The text, EN and NL.
+4. `_latch_charge()` alone: a battery that leaves the plan leaves the latch.
+"""
+
+import asyncio
+import json
+import logging
+import os
+import sys
+import tempfile
+import time
+from concurrent.futures import ProcessPoolExecutor
+from datetime import datetime, timedelta, timezone
+from multiprocessing import get_context
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+sys.path.insert(0, HERE)
+sys.path.insert(0, os.path.join(HERE, "tools"))
+logging.disable(logging.WARNING)
+
+import opt11p3_replay as rp                                    # noqa: E402
+import app.main as m                                           # noqa: E402
+from app import homeview, solarfc                              # noqa: E402
+from app.main import Controller                                # noqa: E402
+from app.p1 import make_sample, split_signed                   # noqa: E402
+from app.store import unit_key                                 # noqa: E402
+
+fails = []
+
+
+def check(name, cond):
+    print(f"  {'ok  ' if cond else 'FAIL'} {name}")
+    if not cond:
+        fails.append(name)
+
+
+L = timezone(timedelta(hours=1))             # Brussels in winter (CET)
+
+
+def at(day, hh, mm=0):
+    """Local time on 2026-11-`day` (CET) as UTC."""
+    return datetime(2026, 11, day, hh, mm, tzinfo=L).astimezone(timezone.utc)
+
+
+def st(kwh, when, *, unit="kWh"):
+    return {"state": f"{kwh}", "attributes": {"unit_of_measurement": unit},
+            "last_updated": when.isoformat(),
+            "last_reported": when.isoformat()}
+
+
+GONE = {"state": "unavailable", "attributes": {}}
+T_ENT, M_ENT = "sensor.fc_today", "sensor.fc_tomorrow"
+BRU = solarfc.BILLING_TZ
+
+
+def bru(y, mo, d, hh, mm=0):
+    return datetime(y, mo, d, hh, mm, tzinfo=BRU).astimezone(timezone.utc)
+
+
+def rs(today, tomorrow, now, hold):
+    return solarfc.read_sum([(T_ENT, today)], [(M_ENT, tomorrow)], now, hold)
+
+
+def near(a, b, tol):
+    """`|a - b| < tol`, and False (not a crash) when `a` is missing."""
+    return a is not None and abs(a - b) < tol
+
+
+def used(hold, now):
+    f = rs(GONE, GONE, now, hold)[0]
+    return f is not None
+
+
+def hold_of(read_at, today=0.4, tomorrow=12.0):
+    h = solarfc.Hold()
+    rs(st(today, read_at), st(tomorrow, read_at),
+       read_at + timedelta(minutes=5), h)
+    return h
+
+
+# --------------------------------------------------------------------------- #
+print("1. solarfc: the evening figure serves until the bell starts")
+h17 = hold_of(at(3, 17, 5))
+check("a 17:05 reading is kept at 20:00, 22:00, 00:00, 03:00 and 05:59",
+      all(used(h17, t) for t in (at(3, 20, 0), at(3, 22, 0), at(4, 0, 0),
+                                 at(4, 3, 0), at(4, 5, 59))))
+f_late = rs(GONE, GONE, at(4, 5, 59), h17)[0]
+check("... at 05:59 it is tomorrow's 12.0 kWh as TODAY's, the whole day",
+      f_late is not None and f_late.kept and f_late.today.kwh == 12.0
+      and f_late.tomorrow is None and f_late.at == at(3, 17, 5)
+      and f_late.between(at(4, 6, 0), at(4, 20, 0)) is not None
+      and abs(f_late.between(at(4, 6, 0), at(4, 20, 0)) - 12.0) < 1e-6)
+check("... and at 06:00 (12 h 55 min old, the bell starts) it is not",
+      not used(h17, at(4, 6, 0)) and not used(h17, at(4, 6, 30))
+      and not used(h17, at(4, 12, 0)))
+check("... not the next evening either, and not on the 5th",
+      not used(h17, at(4, 22, 0)) and not used(h17, at(5, 3, 0)))
+
+# The age limit of this case: 15 h, for a figure that was usable at midnight.
+h1230 = hold_of(at(3, 12, 30))
+check("a 12:30 reading (11 h 30 min old at midnight): used until 03:29 "
+      "(14 h 59 min old) ...",
+      used(h1230, at(4, 0, 0)) and used(h1230, at(4, 3, 29)))
+check("... and not from 03:31 (15 h 01 min), though it is before 06:00",
+      not used(h1230, at(4, 3, 31)) and not used(h1230, at(4, 5, 30)))
+h1600 = hold_of(at(3, 16, 0))
+check("a 16:00 reading: the 06:00 window ends it, not the 15 h limit "
+      "(14 h old at 06:00)", used(h1600, at(4, 5, 59))
+      and not used(h1600, at(4, 6, 0)))
+
+# Not used: a morning figure at night (12 h), and no come-back after midnight.
+h0905 = hold_of(at(3, 9, 5))
+check("a 09:05 reading: kept at 20:00 (10 h 55 min), not at 22:00 (12 h 55 min)",
+      used(h0905, at(3, 20, 0)) and not used(h0905, at(3, 22, 0)))
+check("... and it does not come back after midnight (14 h 55 min at 00:00, "
+      "under the 15 h of the evening-to-morning case): it was not usable "
+      "at midnight",
+      not used(h0905, at(4, 0, 0)) and not used(h0905, at(4, 0, 2))
+      and not used(h0905, at(4, 2, 0)))
+h1105 = hold_of(at(3, 11, 59))
+check("the same for a reading that is 12 h 01 min old at midnight",
+      not used(h1105, at(4, 0, 0)) and not used(h1105, at(4, 0, 30)))
+h1201 = hold_of(at(3, 12, 1))
+check("... and one that is 11 h 59 min old at midnight is used",
+      used(h1201, at(4, 0, 0)) and used(h1201, at(4, 3, 0)))
+check("a same-day figure past 12 h is not used: a 07:05 reading at 20:00 "
+      "(12 h 55 min)", not used(hold_of(at(3, 7, 5)), at(3, 20, 0)))
+check("a figure over 15 h old is not used: 17:05 read, 08:06 next day "
+      "(15 h 01 min, bell started)", not used(h17, at(4, 8, 6)))
+check("(a figure from the day before is not used either)",
+      not used(hold_of(at(2, 17, 5)), at(3, 22, 0))
+      and not used(hold_of(at(2, 17, 5)), at(4, 3, 0)))
+
+# Today's figure is not tomorrow's, and the figure is for its own day only.
+hd = solarfc.Hold()
+rs(st(3.0, at(3, 17, 0)), st(12.0, at(3, 17, 0)), at(3, 17, 5), hd)
+fx = rs(GONE, GONE, at(4, 4, 0), hd)[0]
+check("04:00: today's sensor is gone: the 4th gets the 3rd's TOMORROW "
+      "figure (12.0), never the 3rd's today figure (3.0)",
+      fx is not None and fx.today.kwh == 12.0)
+fy = rs(st(5.0, at(4, 3, 50)), st(9.0, at(4, 3, 50)), at(4, 4, 0), hd)[0]
+check("a fresh figure replaces the kept one at once (04:00: 5.0 today, "
+      "9.0 tomorrow; not kept)", fy is not None and not fy.kept
+      and fy.today.kwh == 5.0 and fy.tomorrow.kwh == 9.0)
+fy2 = rs(st(5.0, at(4, 7, 55)), GONE, at(4, 8, 0), hd)[0]
+check("... and at 08:00, today fresh and tomorrow's sensor down for over 3 h: "
+      "no tomorrow (the 3rd's figure is not the 5th's)",
+      fy2 is not None and fy2.tomorrow is None and fy2.today.kwh == 5.0)
+
+# Restart: the saved hold keeps the figure.
+for label, now in (("01:00", at(4, 1, 0)), ("04:00", at(4, 4, 0))):
+    back = solarfc.Hold(json.loads(json.dumps(hold_of(at(3, 17, 5)).dump())))
+    fr = rs(GONE, GONE, now, back)[0]
+    check(f"restart at {label}: the saved hold (FC_HOLD_KEY) gives the "
+          "17:05 figure again", fr is not None and fr.kept
+          and fr.today.kwh == 12.0 and fr.at == at(3, 17, 5))
+
+# DST: the 25 h autumn day and the 23 h spring day. The window ends at 06:00
+# LOCAL, not 6 h after midnight.
+for (y, mo, d), label in (((2026, 10, 25), "25 h day 2026-10-25"),
+                          ((2027, 3, 28), "23 h day 2027-03-28")):
+    t17 = bru(y, mo, d - 1, 17, 5)
+    hs = hold_of(t17)
+    ok_in = used(hs, bru(y, mo, d - 1, 23, 59)) and all(
+        used(hs, bru(y, mo, d, hh, mm)) for hh, mm in
+        ((0, 0), (1, 30), (4, 0), (5, 59)))
+    check(f"{label}: the 17:05 figure serves 23:59 to 05:59 local", ok_in)
+    check(f"... and not at 06:00 local", not used(hs, bru(y, mo, d, 6, 0))
+          and not used(hs, bru(y, mo, d, 6, 30)))
+
+# --------------------------------------------------------------------------- #
+print("\n2. The real Controller, whole nights (parallel processes)")
+A, B = "inverter-a", "inverter-b"
+PROFILE = ('{"periods": ['
+           '{"name": "night", "days": "all", "from": "22:00", "to": "07:00",'
+           ' "eur_per_kwh": 0.26},'
+           '{"name": "day", "days": "all", "from": "07:00", "to": "22:00",'
+           ' "eur_per_kwh": 0.34}]}')
+# The price dips at 04:00 (a dynamic site): the cheap run starts after 03:00.
+PROFILE_LATE = ('{"periods": ['
+                '{"name": "night", "days": "all", "from": "22:00",'
+                ' "to": "04:00", "eur_per_kwh": 0.28},'
+                '{"name": "dawn", "days": "all", "from": "04:00",'
+                ' "to": "07:00", "eur_per_kwh": 0.20},'
+                '{"name": "day", "days": "all", "from": "07:00",'
+                ' "to": "22:00", "eur_per_kwh": 0.34}]}')
+CHOICE = {"a": (True, "leftover_solar", False),
+          "b": (True, "cheap_hours", False)}
+LAST = at(3, 17, 5)
+EVENING = [at(3, 16, 0) + timedelta(minutes=30 * i) for i in range(12)] \
+    + [at(3, 21, 55)]
+
+
+def opts(late=False, cap=2500):
+    o = dict(rp.options(True, False, 2))
+    o.update(cycle_cost_threshold_eur=0.07,
+             static_profile=PROFILE_LATE if late else PROFILE,
+             pv_forecast_entity=T_ENT, pv_forecast_tomorrow_entity=M_ENT,
+             peak_cap_w=cap)
+    return o
+
+
+def sensors(*, silent=True, fresh_from=None, fresh=(1.0, 5.0),
+            fresh_until=None):
+    """Sensors that update until 17:05 (or all night) and then show that
+    reading for good; from `fresh_from` a new reading every call."""
+    def f(now, ent):
+        if fresh_from is not None and now >= fresh_from:
+            when = now if fresh_until is None else min(now, fresh_until)
+            return st(fresh[0] if ent == T_ENT else fresh[1], when)
+        when = min(now, LAST) if silent else now
+        return st(0.4 if ent == T_ENT else 6.0, when)
+    return f
+
+
+def run_night(spec):
+    """One scenario in this process -> a plain dict. `spec`: start (UTC),
+    hours, silent, fresh_from, fresh, restarts, soc, load_until_s, marks."""
+    start = spec["start"]
+    soc0 = spec.get("soc", {"a": 10.0, "b": 10.0})
+    house_w = spec.get("house_w", 700.0)
+    store = rp._Store()
+    for u, (use, mode, sell) in CHOICE.items():
+        for k, val in (("pack_use", use), ("pack_mode", mode),
+                       ("pack_sell", sell)):
+            store.data[unit_key(f"inverter-{u}", k)] = val
+    if spec.get("latch"):
+        store.data[m.CHARGE_LATCH_KEY] = spec["latch"]
+    sens = sensors(silent=spec.get("silent", True),
+                   fresh_from=spec.get("fresh_from"),
+                   fresh=spec.get("fresh", (1.0, 5.0)),
+                   fresh_until=spec.get("fresh_until"))
+    clock = [EVENING[0]]
+
+    class H(rp.Hass):
+        async def state(self, e):
+            return GONE if spec.get("gone") else sens(clock[0], e)
+
+    hass = H(("a", "b"), lambda t: 300.0, soc0)
+    out = dict(marks={}, soc_at={})
+
+    def build(sto):
+        tmp = tempfile.mkdtemp(prefix="o34-")
+        c = Controller(dict(opts(spec.get("late", False),
+                                 spec.get("cap", 2500))), hass, sto,
+                       rp._Pub(),
+                       stop=asyncio.Event(),
+                       peak_db_path=os.path.join(tmp, "tariff.db"),
+                       price_history_path=os.path.join(tmp, "ph.json"))
+        for i in c.inverters:
+            i.dev_min, i.dev_max = -5000.0, 5000.0
+        c.auto = True
+        c.house_profile.load({d: {str(hh): house_w for hh in range(24)}
+                              for d in ("2026-10-31", "2026-11-01",
+                                        "2026-11-02")})
+        return c
+
+    async def go():
+        cur = store
+        c = build(cur)
+        real_dt, real_hv = m.datetime, homeview.datetime
+
+        class _DT(real_dt):
+            @classmethod
+            def now(cls, tz=None):
+                return clock[0] if tz is None else clock[0].astimezone(tz)
+
+        m.datetime = homeview.datetime = _DT
+        try:
+            for t_pre in EVENING:
+                clock[0] = t_pre
+                await c._read_forecast()
+            pending = sorted(spec.get("restarts", ()))
+            marks = sorted(spec.get("marks", ()))
+            first, t = True, 0.0
+            hz = spec["hours"] * 3600.0
+            while t < hz:
+                now = start + timedelta(seconds=t)
+                clock[0] = now
+                if pending and now >= pending[0]:
+                    pending.pop(0)
+                    data = json.loads(json.dumps(cur.data))
+                    cur = rp._Store()
+                    cur.data.update(data)
+                    c = build(cur)
+                    first = True
+                if first or int(t) % 600 == 0:
+                    # The tariff, resolved here at its own pace: the real
+                    # refresh task sleeps on the wall clock.
+                    hor = float(m.price_option(c.o, "price_horizon_h"))
+                    c.tariff_plan = await m.resolve_tariff(
+                        c.o, now, now + timedelta(hours=hor), now=now,
+                        history=c.price_history, watch=c.price_watch)
+                    c.tariff_at = now
+                    first = False
+                hass.t = t
+                imp, exp = split_signed(hass.grid())
+                c.p1.submit(make_sample("ha_signed", imp, exp, phases=1,
+                                        ingest_ts=now,
+                                        ingest_mono=time.monotonic()))
+                await c.read_inputs(now_mono=t)
+                await c.cycle()
+                hass.advance(5.0, 10.0)
+                if int(t) % 300 == 0:
+                    out["soc_at"][now.astimezone(L).strftime("%H:%M")] = (
+                        hass.plants["a"].soc, hass.plants["b"].soc,
+                        hass.plants["a"].p, c.solar_fc is None,
+                        bool(c.solar_fc and c.solar_fc.kept),
+                        None if c.plan_targets() is None
+                        else c.plan_targets().get(A))
+                while marks and now >= marks[0]:
+                    marks.pop(0)
+                    cards = homeview.battery_rows(c, False, True)
+                    blk = homeview.solar_block(c, now)
+                    a_card = next(b for b in cards if b["name"] == A)
+                    out["marks"][now.astimezone(L).strftime("%H:%M")] = dict(
+                        line=blk["line"], state=blk["state"],
+                        why_a=a_card["why_key"],
+                        fc_none=c.solar_fc is None,
+                        kept=bool(c.solar_fc and c.solar_fc.kept),
+                        target_a=(c.plan_targets() or {}).get(A),
+                        soc_a=hass.plants["a"].soc,
+                        p_a=hass.plants["a"].p,
+                        charging=hass.plants["b"].p < -200.0)
+                t += 5.0
+            out["soc"] = (hass.plants["a"].soc, hass.plants["b"].soc)
+            out["latch"] = getattr(c, "_charge_latch", None) is not None
+        finally:
+            m.datetime, homeview.datetime = real_dt, real_hv
+        return out
+
+    return asyncio.run(go())
+
+
+NIGHT = at(3, 22, 0)
+SCEN = {
+    "fresh": dict(start=NIGHT, hours=9, silent=False,
+                  marks=[at(4, 4, 30)]),
+    "silent": dict(start=NIGHT, hours=9,
+                   marks=[at(4, 1, 0), at(4, 4, 30), at(4, 6, 30)]),
+    "restart": dict(start=NIGHT, hours=9,
+                    restarts=[at(4, 1, 0), at(4, 4, 0)],
+                    marks=[at(4, 1, 30), at(4, 4, 30)]),
+    # c. the charge cannot start before 03:00 (the price dips at 04:00)
+    "late": dict(start=at(4, 2, 30), hours=4.5, late=True, house_w=500.0,
+                 soc={"a": 40.0, "b": 70.0}, marks=[at(4, 3, 30)]),
+    "late_fresh": dict(start=at(4, 2, 30), hours=4.5, late=True,
+                       house_w=500.0, soc={"a": 40.0, "b": 70.0},
+                       silent=False),
+    # d. a fresh, darker figure at 02:00 during the charge (a lighter house
+    # use, so the level has room to rise)
+    "dark": dict(start=at(4, 1, 30), hours=2.0, soc={"a": 45.0, "b": 45.0},
+                 house_w=500.0, fresh_from=at(4, 2, 0), fresh=(1.0, 5.0),
+                 marks=[at(4, 1, 59), at(4, 2, 5)]),
+    "kept": dict(start=at(4, 1, 30), hours=2.0, soc={"a": 45.0, "b": 45.0},
+                 house_w=500.0, marks=[at(4, 1, 59), at(4, 2, 5)]),
+    # before the charge starts: a fresh figure replaces the kept one, up and
+    # down, at once
+    "pre_kept": dict(start=at(4, 2, 30), hours=0.25, late=True,
+                     house_w=500.0, marks=[at(4, 2, 44)]),
+    "pre_dark": dict(start=at(4, 2, 30), hours=0.25, late=True,
+                     house_w=500.0, fresh_from=at(4, 2, 40),
+                     fresh=(1.0, 5.0), marks=[at(4, 2, 44)]),
+    "pre_bright": dict(start=at(4, 2, 30), hours=0.25, late=True,
+                       house_w=500.0, fresh_from=at(4, 2, 40),
+                       fresh=(30.0, 30.0), marks=[at(4, 2, 44)]),
+    # d. the last hour, after the kept figure ended at 06:00
+    "tail": dict(start=at(4, 5, 40), hours=80 / 60.0,
+                 soc={"a": 70.0, "b": 70.0}, restarts=[at(4, 6, 30)],
+                 marks=[at(4, 5, 50), at(4, 6, 10), at(4, 6, 40)]),
+    # a fresh, brighter figure at 03:10 lowers A's level below its SoC (A
+    # stops, B goes on), then the sensors go quiet: the forecast ends at 06:10
+    "lowered": dict(start=at(4, 2, 30), hours=4.5, house_w=500.0,
+                    soc={"a": 30.0, "b": 30.0}, fresh_from=at(4, 3, 10),
+                    fresh_until=at(4, 3, 10), fresh=(30.0, 30.0),
+                    marks=[at(4, 3, 5), at(4, 3, 20), at(4, 6, 30)]),
+    # F1: the add-on was down when the latch of the night before ended; it is
+    # back inside a cheap run, with the sensors unavailable (no forecast)
+    "stale": dict(start=at(3, 22, 0), hours=0.5, gone=True,
+                  latch={"until": at(3, 7, 15).isoformat(),
+                         "born": at(2, 23, 0).isoformat(),
+                         "levels": {A: 80.0, B: 80.0}},
+                  marks=[at(3, 22, 20)]),
+    "stale_live": dict(start=at(3, 22, 0), hours=0.5, gone=True,
+                       latch={"until": at(4, 7, 15).isoformat(),
+                              "born": at(3, 22, 0).isoformat(),
+                              "levels": {A: 80.0, B: 80.0}},
+                       marks=[at(3, 22, 20)]),
+    # the same, B already full and a 1.5 kW limit: the run is sized at the
+    # battery's 2.5 kW rating and ends at 06:33, before A is there, so the
+    # next slice is planned after 06:00 and is only A's
+    "tail_bfull": dict(start=at(4, 5, 40), hours=80 / 60.0, cap=1500,
+                       soc={"a": 65.0, "b": 95.0},
+                       marks=[at(4, 5, 50), at(4, 6, 10), at(4, 6, 45)]),
+}
+t0 = time.time()
+with ProcessPoolExecutor(max_workers=min(6, os.cpu_count() or 2),
+                         mp_context=get_context("fork")) as pool:
+    futs = {k: pool.submit(run_night, v) for k, v in SCEN.items()}
+    R = {k: f.result() for k, f in futs.items()}
+print(f"    {len(R)} scenarios in {time.time() - t0:.0f} s")
+
+
+def show(k):
+    r = R[k]
+    print(f"    {k:10} A {r['soc'][0]:.2f} %  B {r['soc'][1]:.2f} %  "
+          f"marks {', '.join(sorted(r['marks']))}")
+
+
+for k in R:
+    show(k)
+fa, si, rr = R["fresh"], R["silent"], R["restart"]
+
+# a. silent from 17:05
+check("a fresh figure all night: A ends at its planned level (87 %), B "
+      "full", abs(fa["soc"][0] - 86.9) < 0.5 and fa["soc"][1] > 94.5)
+check("sensors silent from 17:05: A ends where the fresh run ends it "
+      f"({si['soc'][0]:.1f} against {fa['soc'][0]:.1f} %)",
+      abs(si["soc"][0] - fa["soc"][0]) < 0.3)
+check("... and so does B (Cheap hours; the wide no-forecast gap does not "
+      f"stop its slices): {si['soc'][1]:.1f} against {fa['soc'][1]:.1f} %",
+      abs(si["soc"][1] - fa["soc"][1]) < 0.3)
+check("A charges through 03:00 without a break (no step at 03:00)",
+      si["soc_at"]["03:30"][0] > si["soc_at"]["03:00"][0] + 4.0
+      and si["soc_at"]["03:00"][0] > si["soc_at"]["02:55"][0] + 0.3)
+m1, m4 = si["marks"]["01:00"], si["marks"]["04:30"]
+check("01:00 and 04:30: the kept figure is in use, with a day plan, and the "
+      "line says so (EN)",
+      not m1["fc_none"] and m1["kept"] and not m4["fc_none"] and m4["kept"]
+      and m4["state"] == "plan"
+      and m4["line"] == "Solar forecast read 17:05, kept for tonight."
+      and m4["target_a"] is not None
+      and near(m4["target_a"], fa["marks"]["04:30"]["target_a"], 1e-9))
+check("... and the level is the fresh run's (the kept figure counts as a "
+      "fresh one)", near(m4["target_a"], 86.87, 0.2))
+m6 = si["marks"]["06:30"]
+check("06:30: the kept figure has ended (the bell started) and the screen "
+      "does not say 'kept' (the charge was done by then in this shape)",
+      m6["fc_none"] and "kept" not in m6["line"])
+
+# b. restarts
+check("restarts at 01:00 and 04:00 (a new Controller on the saved store): "
+      f"A {rr['soc'][0]:.1f}, B {rr['soc'][1]:.1f} % as without them",
+      abs(rr["soc"][0] - si["soc"][0]) < 0.3
+      and abs(rr["soc"][1] - si["soc"][1]) < 0.3)
+check("... with the figure kept right after each restart",
+      all(rr["marks"][k]["kept"] and not rr["marks"][k]["fc_none"]
+          and rr["marks"][k]["target_a"] is not None
+          for k in ("01:30", "04:30")))
+
+# c. a charge that cannot start before 03:00
+la, lf = R["late"], R["late_fresh"]
+ml = la["marks"]["03:30"]
+check("the cheap hours start at 04:00: nothing charges at 03:30",
+      ml["soc_a"] < 40.1 and not ml["charging"])
+check("... the kept figure still stands at 03:30 (no charge had started, so "
+      "no level to latch): the plan is kept, not 'no forecast'",
+      not ml["fc_none"] and ml["kept"] and ml["target_a"] is not None)
+check("... and the charge starts at 04:00 on it: A ends where a fresh "
+      f"figure ends it ({la['soc'][0]:.1f} against {lf['soc'][0]:.1f} %)",
+      lf["soc"][0] > 50.0 and abs(la["soc"][0] - lf["soc"][0]) < 0.3
+      and abs(la["soc"][1] - lf["soc"][1]) < 0.3)
+
+# d. a fresh figure replaces the kept one at once
+dk, kp = R["dark"], R["kept"]
+check("a fresh, darker figure at 02:00 during the charge: the level goes "
+      "UP at once (02:05)",
+      kp["marks"]["02:05"]["target_a"] is not None
+      and dk["marks"]["02:05"]["target_a"] is not None
+      and dk["marks"]["02:05"]["target_a"] > kp["marks"]["02:05"]["target_a"]
+      + 3.0 and not dk["marks"]["02:05"]["kept"]
+      and dk["marks"]["01:59"]["kept"])
+check("... and A charges on to it (more than on the kept figure: "
+      f"{dk['soc'][0]:.1f} against {kp['soc'][0]:.1f} %)",
+      dk["soc"][0] > kp["soc"][0] + 3.0)
+pk, pd, pb = R["pre_kept"], R["pre_dark"], R["pre_bright"]
+t_k, t_d, t_b = (x["marks"]["02:44"]["target_a"] for x in (pk, pd, pb))
+print(f"    level before any charge, 02:44: kept {t_k}, dark {t_d}, "
+      f"bright {t_b}")
+check("before a charge has started (nothing charges at 02:44): a darker "
+      "fresh figure raises the level and a brighter one lowers it, at once",
+      all(not x["marks"]["02:44"]["charging"] for x in (pk, pd, pb))
+      and t_k is not None and t_d is not None and t_b is not None
+      and t_d > t_k + 3.0 and t_b < t_k - 3.0
+      and not pd["marks"]["02:44"]["kept"]
+      and not pb["marks"]["02:44"]["kept"])
+
+# e. the last hour, after the kept figure ended
+tl = R["tail"]
+t5, t6, t7 = (tl["marks"][k] for k in ("05:50", "06:10", "06:40"))
+check("05:50: charging on the kept figure; 06:10: the figure has ended",
+      t5["kept"] and not t5["fc_none"] and t6["fc_none"])
+check("06:10 and 06:40 (the second after a restart at 06:30): A still "
+      "charges to its level, 'charges from the grid' is the Why",
+      t6["p_a"] < -500.0 and t7["p_a"] < -500.0
+      and t6["why_a"] == "grid_charge" and t7["why_a"] == "grid_charge")
+check("... and ends the hour higher than it was (+8 % or more from 06:00)",
+      tl["soc_at"]["06:55"][0] > tl["soc_at"]["06:00"][0] + 8.0)
+lo = R["lowered"]
+l0, l1, l2 = (lo["marks"][k] for k in ("03:05", "03:20", "06:30"))
+check("a fresh, brighter figure lowers A's level below its SoC during the "
+      f"charge ({l0['target_a']} -> {l1['target_a']}, SoC "
+      f"{l1['soc_a']:.1f} %), and A stops",
+      l0["target_a"] is not None and l1["target_a"] is not None
+      and l1["target_a"] < l1["soc_a"] - 2.0
+      and l1["target_a"] < l0["target_a"] - 10.0
+      and lo["soc_at"]["03:30"][0] < lo["soc_at"]["03:20"][0] + 0.5)
+check("the sensors go quiet, the forecast ends (06:30): the latch holds the "
+      "LOWERED level, so A does not charge back up to the old one "
+      f"({lo['soc_at']['03:30'][0]:.1f} -> {lo['soc_at']['06:55'][0]:.1f} %), "
+      "while B goes on",
+      l2["fc_none"] and l2["target_a"] is not None
+      and l2["target_a"] < l2["soc_a"] and l2["p_a"] > -200.0
+      and lo["soc_at"]["06:55"][0] < lo["soc_at"]["03:30"][0] + 1.0
+      and lo["soc"][1] > lo["soc_at"]["03:30"][1] + 15.0)
+st_, sl_ = R["stale"], R["stale_live"]
+check("F1: a latch from the night before (ended 07:15) loaded at a restart "
+      "inside a cheap run, with no forecast: nothing grid-charges "
+      f"(A {st_['soc'][0]:.1f}, B {st_['soc'][1]:.1f} %) and the line does "
+      "not say the charge goes on",
+      st_["soc"][0] < 10.2 and st_["soc"][1] < 10.2
+      and st_["marks"]["22:20"]["state"] == "no_forecast"
+      and not st_["latch"])
+check("(control: the same latch, still valid until tomorrow 07:15, does "
+      f"charge both: A {sl_['soc'][0]:.1f}, B {sl_['soc'][1]:.1f} %)",
+      sl_["soc"][0] > 11.0 and sl_["soc"][1] > 11.0
+      and sl_["marks"]["22:20"]["state"] == "latched")
+tb = R["tail_bfull"]
+check("B full: the run ends at 06:33 before A is at its level, so the next "
+      "slice is only A's, planned after the figure has ended with A's "
+      "latched level: A goes on charging (06:10, 06:45; "
+      f"{tb['soc_at']['06:00'][0]:.1f} to {tb['soc_at']['06:55'][0]:.1f} %)",
+      tb["marks"]["06:10"]["fc_none"] and tb["marks"]["06:10"]["p_a"] < -500.0
+      and tb["marks"]["06:45"]["p_a"] < -500.0
+      and tb["soc_at"]["06:55"][0] > tb["soc_at"]["06:00"][0] + 8.0)
+check("the screens say what control does (EN): 'No solar forecast now. The "
+      "charge under way goes on to its planned level.'",
+      t6["state"] == "latched" and t7["state"] == "latched"
+      and t6["line"] == "No solar forecast now. The charge under way goes "
+      "on to its planned level.")
+
+# --------------------------------------------------------------------------- #
+print("\n3. The text (EN and NL)")
+en = json.load(open(os.path.join(HERE, "app", "ui_text", "en.json"),
+                    encoding="utf-8"))
+nl = json.load(open(os.path.join(HERE, "app", "ui_text", "nl.json"),
+                    encoding="utf-8"))
+l_en, l_nl = (x["home_words"]["solar"]["latched"] for x in (en, nl))
+print(f"    EN {l_en!r}\n    NL {l_nl!r}")
+check("the new line is short and plain in both languages and the NL is not "
+      "the English", l_en != l_nl and len(l_en.split()) <= 24
+      and len(l_nl.split()) <= 24 and "{" not in l_en + l_nl)
+check("'kept for tonight' is unchanged (EN and NL)",
+      en["home_words"]["solar"]["kept"]
+      == "Solar forecast read {at}, kept for tonight."
+      and nl["home_words"]["solar"]["kept"]
+      == "Zonneprognose van {at}, bewaard voor vannacht.")
+
+# --------------------------------------------------------------------------- #
+print("\n4. The latch alone: a battery that leaves the plan leaves the latch")
+from types import SimpleNamespace                              # noqa: E402
+from app import modetrade, priceruns                           # noqa: E402
+
+CLOCK = [at(4, 1, 0)]
+_dt0 = m.datetime
+
+
+class _FixedDT(_dt0):
+    @classmethod
+    def now(cls, tz=None):
+        return CLOCK[0] if tz is None else CLOCK[0].astimezone(tz)
+
+
+m.datetime = homeview.datetime = _FixedDT
+_tmp = tempfile.mkdtemp(prefix="o34-")
+lc = Controller(dict(opts()), rp.Hass(("a", "b"), lambda t: 300.0,
+                                      {"a": 40.0, "b": 40.0}),
+                rp._Store(), rp._Pub(), stop=asyncio.Event(),
+                peak_db_path=os.path.join(_tmp, "tariff.db"),
+                price_history_path=os.path.join(_tmp, "ph.json"))
+n0 = at(4, 1, 0)
+lruns = SimpleNamespace(cheap=priceruns.Run(at(3, 22, 0), at(4, 7, 0), 0.26))
+charging = SimpleNamespace(action=modetrade.CHARGE,
+                           roles={A: modetrade.CHARGE, B: modetrade.CHARGE})
+resting = SimpleNamespace(action=None, roles={A: modetrade.HOLD,
+                                              B: modetrade.HOLD})
+
+
+def latch_step(fc, tick, targets, now=n0, runs=None, packs=None):
+    CLOCK[0] = now
+    lc.solar_fc, lc.mode_tick = fc, tick
+    lc._latch_charge(now, runs or lruns, targets, packs)
+    return lc._charge_latch, lc.store.data.get(m.CHARGE_LATCH_KEY)
+
+
+FC = object()                   # a forecast is read (fresh or kept)
+lt, saved = latch_step(FC, charging, {A: 80.0, B: 70.0})
+check("both batteries charge with a forecast: both are latched at their "
+      "levels, to the run's end + one slot, and saved",
+      lt is not None and lt[1] == {A: 80.0, B: 70.0}
+      and lt[0] == at(4, 7, 15) and saved is not None
+      and saved["levels"] == {A: 80.0, B: 70.0})
+lt, saved = latch_step(FC, charging, {B: 70.0})
+check("A leaves the plan (its mode or use changed): A is dropped from the "
+      "latch at once, B stays", lt is not None and lt[1] == {B: 70.0}
+      and saved["levels"] == {B: 70.0})
+lc.solar_fc = None
+check("... and with the forecast then gone, A has no latched level (it is "
+      "not charged back to 80 %)", lc.plan_targets() == {B: 70.0})
+lt, saved = latch_step(FC, resting, {A: 80.0, B: 70.0})
+check("A back in the plan while nothing charges: it does not rejoin",
+      lt is not None and lt[1] == {B: 70.0})
+lt, saved = latch_step(FC, resting, {A: 80.0})
+check("B leaves the plan too: the latch is empty, so it is gone and "
+      "cleared from the store", lt is None and saved is None
+      and lc.plan_targets() is None)
+latch_step(FC, charging, {A: 80.0})
+lc.solar_fc = None
+ia = next((i for i in lc.inverters if i.name == A), None)
+st_below = st_at = st_after = None
+lc.mode_runs = lruns
+if ia is not None:
+    ia.soc = 50.0
+    st_below = homeview.plan_state(lc)
+    CLOCK[0] = at(4, 7, 5)          # the run has ended, the latch has not
+    st_after = homeview.plan_state(lc)
+    CLOCK[0] = n0
+    ia.soc = 80.0
+    st_at = homeview.plan_state(lc)
+check("the screen says the charge goes on only while the latched battery is "
+      f"below its level ({st_below!r} at 50 %, {st_at!r} at 80 %)",
+      st_below == "latched" and st_at == "no_forecast")
+check("F2: and only while a cheap run is on: at 07:05, the run over and the "
+      f"latch in its grace slot, it does not ({st_after!r})",
+      st_after == "no_forecast")
+
+print("\n5. The latch ends: expiry, a changed mode, the night's bell")
+long_run = SimpleNamespace(cheap=priceruns.Run(at(4, 7, 0), at(4, 23, 0), .2))
+lc._charge_latch = (at(4, 7, 15), {A: 80.0}, at(4, 1, 0))
+lt, saved = latch_step(None, resting, None, now=at(4, 7, 20), runs=long_run)
+check("F1: past its end (07:15) the latch is dropped even with a cheap run "
+      "on and no forecast (it was only dropped when no run held)",
+      lt is None and saved is None)
+lc._charge_latch = (at(4, 7, 15), {A: 80.0}, at(4, 1, 0))
+CLOCK[0] = at(4, 7, 20)
+lc.solar_fc = None
+check("... plan_targets() ignores a latch past its end", lc.plan_targets()
+      is None)
+CLOCK[0] = at(4, 1, 0)
+check("... and _load_latch() does not bring one back from the store",
+      m._load_latch({"until": at(4, 7, 15).isoformat(), "born":
+                     at(4, 1, 0).isoformat(), "levels": {A: 80.0}},
+                    at(4, 7, 20)) is None
+      and m._load_latch({"until": at(4, 7, 15).isoformat(), "born":
+                         at(4, 1, 0).isoformat(), "levels": {A: 80.0}},
+                        at(4, 6, 0)) is not None)
+
+# F3: the mode or use of a latched battery changes
+def packs_of(a_mode, a_use=True):
+    return [modetrade.Pack(A, a_use, a_mode, False, 2500.0, 50.0, 10.0),
+            modetrade.Pack(B, True, "cheap_hours", False, 2500.0, 50.0, 10.0)]
+
+
+lc._charge_latch = (at(4, 7, 15), {A: 80.0}, at(4, 1, 0))
+lt, _s = latch_step(None, resting, None, packs=packs_of("leftover_solar"))
+check("F3: A is still Leftover solar and on: it stays latched",
+      lt is not None and lt[1] == {A: 80.0})
+lt, saved = latch_step(None, resting, None, packs=packs_of("solar_first"))
+check("F3: the user changes A to Solar first (no forecast): it leaves the "
+      "latch, which is then gone and cleared, so the narrow gap goes too",
+      lt is None and saved is None)
+lc._charge_latch = (at(4, 7, 15), {A: 80.0}, at(4, 1, 0))
+lt, _s = latch_step(None, resting, None,
+                    packs=packs_of("leftover_solar", a_use=False))
+check("F3: or switches A off", lt is None)
+
+# F4: the night's bell
+lc._charge_latch = None
+lt, _s = latch_step(FC, charging, {A: 80.0}, now=at(4, 1, 0))
+check("F4: the latch began at 01:00, so its night's bell is 06:00 the same "
+      "day", m._night_limit(lt[2]) == at(4, 6, 0)
+      and m._night_limit(at(3, 23, 0)) == at(4, 6, 0)
+      and m._night_limit(at(4, 6, 0)) == at(5, 6, 0))
+r1 = SimpleNamespace(cheap=priceruns.Run(at(4, 0, 0), at(4, 7, 0), .2))
+r2 = SimpleNamespace(cheap=priceruns.Run(at(4, 7, 0), at(4, 23, 0), .2))
+r3 = SimpleNamespace(cheap=priceruns.Run(at(4, 6, 0), at(4, 9, 0), .2))
+lc._charge_latch = None
+lt, _s = latch_step(FC, charging, {A: 80.0}, now=at(4, 1, 0), runs=r1)
+check("F4: first run 00:00-07:00 sets the end at 07:15", lt[0] == at(4, 7, 15))
+lt, _s = latch_step(None, resting, None, now=at(4, 6, 50), runs=r1)
+lt2, _s = latch_step(None, resting, None, now=at(4, 7, 5), runs=r2)
+check("F4: a back-to-back run that starts after the bell (07:00-23:00) does "
+      "NOT carry it on: still 07:15", lt2 is not None
+      and lt2[0] == at(4, 7, 15))
+lt3, _s = latch_step(None, resting, None, now=at(4, 7, 20), runs=r2)
+check("F4: and at 07:20 it has ended, though the run goes on", lt3 is None)
+lc._charge_latch = (at(4, 6, 10), {A: 80.0}, at(4, 1, 0))
+lt, _s = latch_step(None, resting, None, now=at(4, 6, 5), runs=r3)
+check("F4: a run that starts AT the bell (06:00-09:00) does carry it on, "
+      "to its end + one slot", lt is not None and lt[0] == at(4, 9, 15))
+m.datetime = homeview.datetime = _dt0
+
+print()
+if fails:
+    print(f"{len(fails)} FAILED:")
+    for f in fails:
+        print("  -", f)
+    sys.exit(1)
+print("all checks passed")