SAFETY-128 review: DECISIONS states the slow-battery limit as measured

Round 2 review: a 10 s dead time reads late at 1-2 s meters, and a 15-20 s lag gives late fits; the note said 3-20 s and 6-10 s gave none. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Bdqr7PiaHcBnzPituu2yTC
SAFETY-128 round 2: find late readings from the batteries, not the meter alone
2026-11-02 05:16:28 +01:00 · 2026-11-02 04:32:04 +01:00 · 2026-11-01 23:45:03 +01:00
14 changed files with 1369 additions and 2 deletions
@@ -2,6 +2,10 @@

 ## 0.20.0

+### Not in a release yet
+
+- When Home Assistant passes readings on late, control no longer swings on them: it waits until the battery shows its last power request, and the peak limit no longer asks for full power on them. The page says so, and if the readings stay too late every inverter goes to 0 W ([[SAFETY-128]]).
+
 **A minor bump: a Forecast tab, a night grid charge sized to what the sun will not give, a kept evening forecast, and no option changes.**
 No option was added, removed or renamed, and no default changed (86 options). It is a minor bump because Leftover solar now buys different amounts from the grid and the night charge keeps its level when the forecast goes quiet; every saved setting still starts.
 **Existing installs need no option change:** options that start 0.19.2 also
@@ -0,0 +1,84 @@
+# SAFETY-128 - a reading that does not answer the last command is not current
+
+**Status: FIXED on release/1.0 (after 0.20.0).** Code: `app/lateness.py`,
+`control.compute(hold=, hold_w=)`, `peakguard.cap_floor()`,
+`Controller._readings_late()`, `Controller.read_inputs()` (feeds the fits).
+Tests: `test_safety128.py` (`tools/safety128_rig.py`, TEST-23's plant).
+
+**Cause** (SAFETY-127 report). Home Assistant can deliver readings late but
+still changing. Every gate judges arrival (SAFETY-01) or a value that stops
+changing (SAFETY-18, SAFETY-37), so a late reading passes them all. The loop
+then corrects, each cycle, an error its last command has already fixed: a
+loop with a dead time far longer than its cycle, which swings and grows. The
+peak guard projects the quarter from the same late figures and pushes to the
+inverter limit in its last seconds (OPT-34 rig F-2).
+
+**Rule.**
+1. *Find late readings* (`Answer.watch()`, every 2 s, from the 1 s reads).
+   - **Batteries** (`Delay`): fit one `d` so that each battery's reading minus
+     its own request at `t - d` (averaged over 2 s for the battery's lag and
+     the read) is flattest. The house does not move that reading, so a
+     repeating load cannot line up with it (review round 1, B1). Needs 5 new
+     readings in 60 s and the request and the reading each to move 300 W.
+     Late from 9.5 s, after 2 late fits in a row. A late fit must explain 75 %
+     and beat every fit up to 6.5 s by 2x; the shortest delay that fits about
+     as well (within 2x, or within 2 500 W^2) is taken instead, since a swing's
+     period fits again. A slow battery (3-10 s lag) answering at once gives no
+     late fit; at a 15-20 s lag some fits read late (see "What it costs").
+     No late battery fit counts for 60 s
+     after a battery gave nothing under its ask: an emptied battery lined its
+     old movement up as 85 s late.
+   - **Meter** (`MeterFit`, round 1's fit): `meter(t) + request(t - d)` is the
+     house alone at the right `d`. Quick, but confounded by the house. Needs
+     16 new values in 60 s, so only a meter of about 3.5 s or faster: at 5 s
+     it gave false delays. Late over 8 s.
+   - A meter fit says late only with evidence from the batteries' side too:
+     a request more than 100 W from the battery reading took 3 s or more to
+     move a reading towards it (`SLOW_START_S`; on time they start within
+     0-1 s in the recorded house at 1 and 2 s ticks), and no battery fit in
+     the last 60 s said on time (under 9.5 s). An ask during which a battery
+     gave nothing under its ask is no slow evidence. A repeating load fools
+     the meter fit but not these. No meter verdict in the first 150 s.
+   - On time again on a battery fit under 6.5 s, or a meter fit within 8 s
+     unless a battery fit said late (hysteresis). With no fit for 120 s the
+     verdict is dropped.
+2. *Hold.* While late, a request more than 100 W from the battery reading is
+   pending until that reading comes within 100 W of it, or half way. Meanwhile
+   the loop may not lead the reading by more than 100 W that way, and the peak
+   guard's floor is capped at the request that stands. The loop is not held
+   while a battery gives nothing under its ask or refuses (SAFETY-52/94).
+3. *Late verdict.* Pending for `LATE_S` (23 s) with no reading moving 100 W
+   towards it: control holds, then after `stale_input_s` goes to 0 W
+   ("readings late"), as for a missing input.
+4. *Seen.* While late an amber row says "Home Assistant readings show requests
+   about N seconds late, so control holds the batteries." (NL too). N is the
+   batteries' fitted delay: Home Assistant's lag plus the battery's own
+   answer. While only the meter has shown it the row gives no figure. One
+   WARNING (`READINGS_LATE`) per episode and one line when it ends.
+
+**With readings on time** no verdict was reached in any reviewer scenario
+(owner-shaped house, ovens 20/40 to 60/60 s, clouds, a 300 W/s battery, 6-8 s
+dead times, HA jitter 0-4 s, an EV following the meter, capped batteries, HA
+restarts, meter pauses; 1, 2 and 5 s meters) nor in 2 days of the recorded
+house at 1, 2 and 5 s ticks, so the commands are the same as without the gate.
+The fits run all the time; the pull request has the counts.
+
+**What it costs.**
+- Found 36-68 s after a lag starts at 1-2 s meters, about 3 minutes at a 5 s
+  meter (battery fit only; the meter fit needs a faster meter). Until then control is as before. At 5 s and 30 s
+  late the export is cut to about a third, not removed.
+- A battery that answers slowly is read as late readings and held: a dead
+  time of 10 s or more (8 s reads 7-8; 10 s reads 10 at 1-2 s meters, 9 at
+  5 s), or a 15-20 s lag (review round 2). The GoodWe measured settles in 6 s
+  (`freshness.PLANT_SETTLE_S`); the row then blames Home Assistant wrongly.
+- The row can stay up to 180 s after the readings are on time on a steady
+  site. While only the meter has shown the delay it gives no figure.
+- A battery that cannot follow while the readings are late (at a limit, not
+  reading 0 W) is held, then set to 0 W after 38 s.
+- The fits cost a few ms every 2 s (x86, measured after 3 idle days); the
+  history they read is bounded (60 s of readings, 150 s of requests).
+
+**Left out.** The setpoint -> Home Assistant round trip: the fitted delay gives
+the figure from readings the add-on already has. The hold's step-and-pull-back
+at extreme lag and the arbitrage charge's sizing on late readings
+(`charge_room_w()`) are follow-up cards.
@@ -298,6 +298,9 @@ PROBE_S = 34.0
 # command: every battery that may move this way is at its mode's limit.
 MODE_BOUND = "mode-bound"

+# SAFETY-128. The loop's reason while it waits for the readings to answer.
+WAITING = "waiting for readings"
+

@dataclass(frozen=True)
 class Tuning:
@@ -486,6 +489,8 @@ def compute(
    bound: tuple | None = None,
    gave_nothing: bool | None = None,
    idle_w: float = 0.0,
+    hold: int = 0,
+    hold_w: float | None = None,
 ) -> Decision:
    """One control cycle. A cycle is one meter update (~5 s on a HomeWizard P1).

@@ -506,6 +511,9 @@ def compute(
    `idle_w`   SAFETY-97: what `actual_w` reads while the batteries give
               nothing (app/idle.py). The refusal's band and its end are
               centred on it. 0 is the law as it was.
+    `hold`     SAFETY-128: +1 / -1, the batteries have not answered the last
+               command that way (app/lateness.py), so the loop may not go
+               past `hold_w` (None: `prev_w`) that way. 0 is the law as it was.
    """
    reason = "tracking"
    # OPT-11: a bound that leaves out 0 W would FORCE a direction, which no
@@ -622,6 +630,11 @@ def compute(
            i_w = min(moved, i_w)
        else:
            i_w = max(moved, i_w)
+    # SAFETY-128: no further than `hold_w` until the readings answer the ask.
+    held_at = float(prev_w if hold_w is None else hold_w)
+    if hold and hold * (i_w - held_at) > 0:
+        i_w = held_at
+        reason = WAITING

    # OPT-11: the integrator does not wind past what the modes let the
    # batteries place. Only a side tighter than the rail is left in `bound`
@@ -0,0 +1,373 @@
+"""SAFETY-128: a reading that does not answer the last command is not current.
+
+When Home Assistant delivers readings late but still changing, every gate that
+judges arrival (SAFETY-01) or an unchanged value (SAFETY-18, SAFETY-37) passes
+them, and the loop corrects again, each cycle, an error its last command has
+already fixed. The readings show it: they answer each power request late.
+
+`Answer.watch()` (each 1 s read) fits two delays every FIT_EVERY_S:
+- `Delay`: how long after its request each battery's reading shows it. The
+  house does not move that reading, so a repeating load cannot fool it. It
+  needs the request to move FIT_MOVE_W; one reading per 10 s makes it slow.
+- `MeterFit`: how long after the site request the meter shows it. Quick at a
+  1-3 s meter, none at a slower one, and a house load that repeats can fool it.
+The meter counts only when an ask was slow to start and no battery fit said
+"on time"; with hysteresis (ON_S / OFF_S) the result is `late_seen`. Then (`observe()`, each cycle):
+- a new command more than ANSWER_W from the battery reading is PENDING until
+  that reading comes within ANSWER_W of it, or half way;
+- while pending the loop may not lead the battery reading by more than
+  ANSWER_W that way (`hold`, `hold_w`; not while `exempt`: a battery that
+  gives nothing under its ask or refuses is SAFETY-52/94's case) and the peak
+  guard may not push past what stands (`peak_cap`). Pending for LATE_S with
+  no reading moving towards it is LATE: control holds, then 0 W after
+  `stale_input_s`, as for a missing input.
+
+Not `late_seen`, nothing here acts. DECISIONS/SAFETY-128-late-readings.md.
+"""
+
+import bisect
+from collections import deque
+
+from . import freshness
+from .control import PROBE_ANSWER_W
+
+# Within this of the command the reading has answered it (a probe's answer).
+ANSWER_W = PROBE_ANSWER_W                                         # 100
+# The slowest healthy battery answer: SAFETY-75's 6 s dead time, the 6 s plant
+# settle, one 10 s publish and one 1 s read.
+LATE_S = (2 * freshness.PLANT_SETTLE_S + freshness.PUBLISH_PERIOD_S
+          + freshness.READ_PERIOD_S)                              # 23.0
+
+
+# Each battery reading's delay is fitted over this much history, up to this.
+FIT_S = 60.0
+MAX_DELAY_S = 90
+FIT_EVERY_S = 2.0
+# A fit needs this many new readings (all batteries) and this much movement
+# of the reading and the request.
+FIT_ROWS = 5
+FIT_MOVE_W = 3 * ANSWER_W                                         # 300
+# Late from ON_S, on time again under OFF_S (hysteresis).
+ON_S = 9.5
+OFF_S = 6.5
+# ...after this many late fits in a row.
+ON_FITS = 2
+# With no fit for this long the evidence is dropped (a steady site shows none).
+FIT_GONE_S = 120.0
+# A fit counts only if the commands explain this share of the reading's swing.
+FIT_SHARE = 0.5
+# A late delay must explain this share.
+FIT_SHARE_LATE = 0.75
+# ...and a late delay only if it fits this much better than any fresh one.
+FIT_BETTER = 0.5
+# A shorter delay within this factor of the best fit is taken instead.
+FIT_NEAR = 2.0
+# ...or within this of it (W^2): two fits this good are both exact.
+FIT_FLOOR_W2 = (ANSWER_W / 2) ** 2                               # 2 500
+
+
+def per_second(cmds, first, last):
+    """The request standing at each whole second from `first` to `last`."""
+    ts = [t for t, _c in cmds]
+    return [cmds[max(0, bisect.bisect_right(ts, k) - 1)][1]
+            for k in range(first, last + 1)]
+
+
+def pooled(sets, d):
+    """Pooled variance over [(rows, c, first, sign)] of value + sign *
+    c[t - d], each set about its own mean."""
+    tot, n = 0.0, 0
+    for rows, c, first, sign in sets:
+        e = [v + sign * c[int(t) - d - first] for t, v in rows]
+        m = sum(e) / len(e)
+        tot += sum((x - m) ** 2 for x in e)
+        n += len(e)
+    return tot / n
+
+
+class UnitFit:
+    """One battery's power requests and readings, as they were seen."""
+
+    def __init__(self):
+        self.cmds = deque()      # (t, request) when it changed
+        self.reads = deque()     # (t, reading) when it changed
+
+    def add(self, now, cmd, reading):
+        if cmd is not None and (not self.cmds or self.cmds[-1][1] != cmd):
+            self.cmds.append((now, float(cmd)))
+        if reading is not None and (not self.reads
+                                    or self.reads[-1][1] != reading):
+            self.reads.append((now, float(reading)))
+        while self.reads and self.reads[0][0] < now - FIT_S:
+            self.reads.popleft()
+        while (len(self.cmds) > 1
+               and self.cmds[1][0] <= now - FIT_S - MAX_DELAY_S):
+            self.cmds.popleft()
+
+    def series(self):
+        """(rows, request each second, first second) for the fit, or None:
+        too few new readings, or a reading or a request that has not moved
+        FIT_MOVE_W. The request is averaged over the 2 s before each second:
+        the battery's own lag and the read."""
+        rows = [r for r in self.reads
+                if self.cmds and r[0] >= self.cmds[0][0] + MAX_DELAY_S]
+        vals = [v for _t, v in rows]
+        if len(rows) < 3 or max(vals) - min(vals) < FIT_MOVE_W:
+            return None
+        cs = [c for _t, c in self.cmds]
+        if max(cs) - min(cs) < FIT_MOVE_W:
+            return None
+        first, last = int(rows[0][0]) - MAX_DELAY_S - 2, int(rows[-1][0])
+        c = per_second(self.cmds, first, last)
+        avg = [c[0], c[0]] + [(c[k - 2] + c[k - 1] + c[k]) / 3
+                              for k in range(2, len(c))]
+        return rows, avg, first
+
+
+class Delay:
+    """How long after a power request the batteries' readings show it.
+
+    A reading follows its battery's own request and the house does not move
+    it, so `reading(t) - request(t - d)` is flattest at the right `d`. Each new
+    reading counts once, at the second it was seen, so the 10 s publish adds no
+    delay. One `d` for every battery (Home Assistant delays them all). None
+    with too few readings, or when the requests explain too little of them (a
+    battery that does not follow); not late unless it fits clearly better than
+    any fresh delay, and then the shortest delay that fits about as well."""
+
+    def __init__(self):
+        self.units = {}
+
+    def add(self, now, unit, cmd, reading):
+        self.units.setdefault(unit, UnitFit()).add(now, cmd, reading)
+
+    def estimate(self):
+        ser = [x for x in (u.series() for u in self.units.values()) if x]
+        if sum(len(rows) for rows, _c, _f in ser) < FIT_ROWS:
+            return None
+        sets = [(rows, c, first, -1.0) for rows, c, first in ser]
+        r_var = pooled([(rows, [0.0] * len(c), first, -1.0)
+                        for rows, c, first in ser], 0)
+        pure = [pooled(sets, d) for d in range(0, MAX_DELAY_S + 1)]
+        # The shortest that fits about as well: a swing's period fits again.
+        best = next(d for d, v in enumerate(pure)
+                    if v <= FIT_NEAR * min(pure) + FIT_FLOOR_W2)
+        if r_var <= 0 or pure[best] > (1 - FIT_SHARE) * r_var:
+            return None
+        if best < ON_S:
+            return float(best)
+        if (pure[best] > (1 - FIT_SHARE_LATE) * r_var
+                or pure[best] > FIT_BETTER * min(pure[:int(OFF_S) + 1])):
+            return None
+        return float(best)
+
+
+# The meter's delay: fitted over this much history, from this many new
+# values (a meter of about 3.5 s or faster: a slower one gives too few to
+# fit without false delays); late over M_LATE_S (the plant's 6 s settle and one 2 s meter tick),
+# but only when the batteries' own readings have not just shown them on time.
+M_FIT_S = 60.0
+M_ROWS = 16
+M_LATE_S = freshness.PLANT_SETTLE_S + 2.0                          # 8.0
+M_SHARE, M_BETTER = 0.4, 0.7
+# A meter fit counts only after an ask that took this long to start moving a
+# reading: on time they start within 1-2 s (the recorded house, at 1-5 s).
+SLOW_START_S = 3.0
+
+
+class MeterFit:
+    """How long after a site request the meter shows it (round 1's fit).
+
+    `meter(t) + request(t - d)` is the house alone at the right `d`. Quick,
+    as the meter reads every 1-5 s, but a house load that repeats can line
+    up with an earlier request, so it only counts while the batteries' own
+    fit is not on time (`Answer.watch`)."""
+
+    def __init__(self):
+        self.cmds = deque()      # (t, request) when it changed
+        self.grid = deque()      # (t, meter) new values only
+
+    def add(self, now, cmd, grid):
+        if cmd is not None and (not self.cmds or self.cmds[-1][1] != cmd):
+            self.cmds.append((now, float(cmd)))
+        if grid is not None and (not self.grid or self.grid[-1][1] != grid):
+            self.grid.append((now, float(grid)))
+        while self.grid and self.grid[0][0] < now - M_FIT_S:
+            self.grid.popleft()
+        while (len(self.cmds) > 1
+               and self.cmds[1][0] <= now - M_FIT_S - MAX_DELAY_S):
+            self.cmds.popleft()
+
+    def estimate(self):
+        if len(self.cmds) < 2:
+            return None
+        rows = [(t, g) for t, g in self.grid
+                if t >= self.cmds[0][0] + MAX_DELAY_S]
+        cs = [c for _t, c in self.cmds]
+        if len(rows) < M_ROWS or max(cs) - min(cs) < ANSWER_W:
+            return None
+        first, last = int(rows[0][0]) - MAX_DELAY_S, int(rows[-1][0])
+        c = per_second(self.cmds, first, last)
+        g_var = pooled([(rows, [0.0] * len(c), first, 1.0)], 0)
+        pure = [pooled([(rows, c, first, 1.0)], d)
+                for d in range(0, MAX_DELAY_S + 1)]
+        best = min(range(len(pure)), key=lambda d: (pure[d], d))
+        if g_var <= 0 or pure[best] > (1 - M_SHARE) * g_var:
+            return None
+        if best <= M_LATE_S:
+            return float(best)
+        if pure[best] > M_BETTER * min(pure[:int(M_LATE_S) + 1]):
+            return None
+        return float(best)
+
+
+class Answer:
+    """The answer gate. `observe()` once per cycle, before the loop."""
+
+    def __init__(self):
+        self.ask = None          # the pending command, W (site, + = give)
+        self.from_w = None       # the battery reading when it was asked
+        self.from_grid = None    # the meter when it was asked
+        self.since = None        # when it was asked
+        self.started = False     # a reading has moved towards it
+        self.late_seen = False   # the batteries' readings run late
+        self.late_at = None      # when the late verdict started
+        self.exempt = False      # a battery that cannot follow explains it
+        self._was = None         # (command, reading, meter) at the last call
+        self.delay = Delay()
+        self.meter = MeterFit()
+        self._batt_fit = None     # (when, d): the batteries' last fit
+        self._b_run = 0          # late battery fits in a row
+        self._start_age = None   # (when, how long the last ask took to start)
+        self._exempt_at = None   # when a battery last gave nothing under its ask
+        self._ask_exempt = False
+        self._start = None
+        self.delay_s = None      # the last fitted delay (either fit), s
+        self.shown_s = None      # the batteries' last late delay, for the page
+        self.fits = 0            # fits made (instrumentation)
+        self._fit_at = self._fit_ok = None
+
+    @property
+    def active(self) -> bool:
+        return self.ask is not None and self.late_seen
+
+    @property
+    def hold(self) -> int:
+        """+1 / -1: the loop may not push further that way. 0: no hold."""
+        if not self.active or self.exempt:
+            return 0
+        return 1 if self.ask > self.from_w else -1
+
+    @property
+    def hold_w(self):
+        """How far the loop may go while held: ANSWER_W past the reading."""
+        if not self.hold:
+            return None
+        return self._was[1] + self.hold * ANSWER_W
+
+    def peak_cap(self, standing_w):
+        """The most the peak guard may ask, or None."""
+        return max(float(standing_w), 0.0) if self.active else None
+
+    def late_s(self, now):
+        """Seconds the late verdict has stood, or None."""
+        return None if self.late_at is None else max(0.0, now - self.late_at)
+
+    def watch(self, now, units, standing_w=None, grid_w=None):
+        """Each read (1 s): `units` = [(name, request on its wire, its battery
+        reading)], the site request and the meter. Every FIT_EVERY_S, fit both
+        delays. Late on ON_FITS battery fits from ON_S, or on a meter fit
+        over M_LATE_S when an ask was slow to start (SLOW_START_S) and no
+        battery fit within FIT_S said on time: a house load that repeats can
+        fool the meter fit, not these. On time again on a battery fit under
+        OFF_S, or a meter fit within M_LATE_S unless a battery fit said late.
+        """
+        if self._start is None:
+            self._start = now
+        for name, cmd, reading in units:
+            self.delay.add(now, name, cmd, reading)
+        self.meter.add(now, standing_w, grid_w)
+        if self._fit_at is not None and now - self._fit_at < FIT_EVERY_S:
+            return
+        self._fit_at = now
+        b = self.delay.estimate()
+        if (b or 0.0) >= ON_S and self._exempt_at is not None \
+                and now - self._exempt_at <= FIT_S:
+            b = None          # a battery that stopped following: no late fit
+        m = self.meter.estimate()
+        if b is not None:
+            self._batt_fit = (now, b)
+            self.shown_s = b if b >= ON_S else None
+        recent = (self._batt_fit is not None
+                  and now - self._batt_fit[0] <= FIT_S)
+        b_fresh = recent and self._batt_fit[1] < ON_S
+        b_late = recent and self._batt_fit[1] >= ON_S
+
+        self._b_run = self._b_run + 1 if (b or 0.0) >= ON_S else 0
+        d = b if b is not None else m
+        if d is None:
+            if self._fit_ok is None or now - self._fit_ok > FIT_GONE_S:
+                self.late_seen = False            # nothing to tell it by
+            return
+        self.fits += 1
+        self.delay_s, self._fit_ok = d, now
+        warm = now - self._start >= MAX_DELAY_S + FIT_S
+        m_late = (m or 0.0) > M_LATE_S
+        slow = (self._start_age is not None
+                and now - self._start_age[0] <= M_FIT_S
+                and self._start_age[1] >= SLOW_START_S)
+        if self._b_run >= ON_FITS or (
+                m_late and warm and slow and not b_fresh):
+            self.late_seen = True
+        elif (b is not None and b < OFF_S) or (
+                m is not None and m <= M_LATE_S and not b_late):
+            self.late_seen = False
+
+    def observe(self, now, standing_w, batt_w, *, grid_w=None, exempt=False,
+                idle_w=0.0):
+        """`standing_w` the site command on the wire, `batt_w` the site
+        battery reading (None: unknown, nothing changes), `grid_w` the meter
+        (+ = import), `idle_w` what the batteries read while giving nothing.
+        `exempt`: a battery gives nothing under its ask, or refuses."""
+        if batt_w is None or standing_w is None:
+            return
+        cmd, r = float(standing_w), float(batt_w) - float(idle_w)
+        g = None if grid_w is None else float(grid_w)
+        self.exempt = bool(exempt)
+        if self.exempt:
+            self._exempt_at = now
+        was, self._was = self._was, (cmd, r, g)
+        if self.ask is None:
+            if was is None or cmd == was[0] or abs(cmd - was[1]) < ANSWER_W:
+                return
+            self.ask, self.from_w, self.from_grid = cmd, was[1], was[2]
+            self.since, self.started = now, False
+            self._ask_exempt = False
+        self.ask = cmd
+        # A battery that gives nothing under its ask explains a slow start.
+        self._ask_exempt = self._ask_exempt or self.exempt
+        age = now - self.since
+        gap = self.ask - self.from_w
+        way = 1.0 if gap > 0 else -1.0
+        batt_to = (r - self.from_w) * way
+        grid_to = (-1e9 if g is None or self.from_grid is None
+                   else (self.from_grid - g) * way)
+        if not self.started and max(batt_to, grid_to) >= ANSWER_W:
+            self.started, self.late_at = True, None
+            self._start_age = (now, 0.0 if self._ask_exempt else age)
+        elif (not self.started and age >= SLOW_START_S
+              and not self._ask_exempt):
+            self._start_age = (now, age)
+        if (self.ask - r) * way < ANSWER_W or batt_to >= abs(gap) / 2:
+            self._clear()                         # answered
+        elif abs(gap) < ANSWER_W:
+            self._clear()                         # withdrawn
+        elif exempt:
+            self.late_at = None
+        elif (self.late_at is None and self.late_seen and not self.started
+              and age >= LATE_S):
+            self.late_at = now
+
+    def _clear(self):
+        self.ask = self.from_w = self.from_grid = self.since = None
+        self.started, self.late_at = False, None
@@ -64,6 +64,7 @@ from .clamp import (
    shortfall_note, write_clamp_note,
 )
 from . import freshness
+from . import lateness
 from . import dayview, homeview
 from .daycurve import SolarToday
 from . import messages
@@ -1281,6 +1282,8 @@ class Controller:
        self.cycle_at = None
        self._arb_action = None
        self.inputs_bad_since = None
+        self.answer = lateness.Answer()           # SAFETY-128
+        self._late_logged = self._late_zero = False
        # SAFETY-03. What the loop's OWN bounds did last cycle - a
        # (engaged, note) pair so the alarm can say WHICH bound bit without
        # re-deriving it from a string. ⚠️ THIS ONE STAYS SITE-LEVEL, and it is
@@ -3116,6 +3119,36 @@ class Controller:
        return (decision if self._peak_needed
                else dataclasses.replace(decision, within_aim=True))

+    def _readings_late(self, standing_w):
+        """SAFETY-128: update the answer gate; seconds the late verdict has
+        stood, or None. Readings found late are logged once per episode.
+        DECISIONS/SAFETY-128-late-readings.md."""
+        a = self.answer
+        if self._now_mono is None:
+            return None
+        a.observe(self._now_mono, standing_w, self.site_batt_w,
+                  grid_w=self.grid, exempt=bool(self.batt_refused) or any(
+                      i.refused or (
+                          i.batt is not None
+                          and abs(i.standing_w()) >= lateness.ANSWER_W
+                          and abs(i.batt - i.idle_w) < lateness.ANSWER_W)
+                      for i in self.inverters),
+                  idle_w=self._site_idle_w())
+        if a.late_seen != self._late_logged:
+            self._late_logged = a.late_seen
+            if a.late_seen:
+                self.log_event("readings late - holding",
+                               hint=messages.hint("readings_late"))
+                _LOG.warning("Home Assistant readings arrive late, so control "
+                             "holds the batteries: READINGS_LATE.")
+                _LOG.debug("READINGS_LATE: the readings show a power request "
+                           "%.0f s after it is sent.", a.delay_s)
+            else:
+                self.log_event("readings on time", hint=messages.hint(
+                    "readings_back"))
+                _LOG.info("Home Assistant readings are on time again.")
+        return a.late_s(self._now_mono)
+
    def _peak_reserve(self) -> frozenset:
        """SAFETY-87: the batteries that give nothing for the peak this
        cycle: under their reserve while the others carry a peak floor."""
@@ -3727,6 +3760,10 @@ class Controller:
                else:
                    _LOG.debug("Meter readings are back.")

+        self.answer.watch(now_mono, [(inv.name, inv.standing_w(), inv.batt)
+                                     for inv in self.inverters],  # SAFETY-128
+                          sum(inv.standing_w() for inv in self.inverters),
+                          self.grid)
        if self.inputs_ok:
            if self.inputs_bad_since is not None:
                self.log_event("inputs recovered",
@@ -4647,6 +4684,8 @@ class Controller:
                    "away a partly delivering unit's output.")

        stale_after = float(self.o.get("stale_input_s", 15))
+        late_s = self._readings_late(site_standing)          # SAFETY-128
+        self._late_zero = late_s is not None and late_s >= stale_after
        # ⚠️ `any`, NOT the sole unit's. The hold exists so a single missed poll
        # does not become a fault; a LATCHED inverter must still reach the claim
        # list below, because its `failsafe` SET is what parks it. One tripped
@@ -4672,6 +4711,13 @@ class Controller:
                self.why_words = messages.why_waiting(bad_for)
                self._why_waiting_since = now - timedelta(seconds=bad_for)
                return
+        if late_s is not None and late_s < stale_after and self.inputs_ok \
+                and (self.auto or self.shadow) \
+                and not any(i.sign_wd.tripped for i in self.inverters) \
+                and not (n_units > 1 and self.site_sign_wd.tripped):
+            self.reason = f"readings late {late_s:.0f}s"     # SAFETY-128: hold
+            self.why_words = messages.why_late()
+            return

        claims = []

@@ -4850,6 +4896,9 @@ class Controller:
                               hint=messages.hint("inputs_missing"))
            claims.append(Claim.set("safety", P_SAFETY, 0.0, "inputs missing",
                                    actuator=self.actuator_of("safety")))
+        elif late_s is not None:
+            claims.append(Claim.set("safety", P_SAFETY, 0.0, "readings late",
+                                    actuator=self.actuator_of("safety")))

        # --- SAFETY-07: the quarter-peak projection guard --------------------
        # ONE `lo` limit at P_PEAK, and peakguard.py carries the whole argument.
@@ -4973,6 +5022,8 @@ class Controller:
            self.peak_guard = self._peak_on_able(self.peak_guard,
                                                 maint_results)
            self.peak_guard = self._peak_landing(self.peak_guard)
+            self.peak_guard = peakguard.cap_floor(          # SAFETY-128
+                self.peak_guard, self.answer.peak_cap(site_standing))
        # SITE, and peakguard.claim() says so on the object it builds. The
        # quantity is the 15-minute average OFFTAKE AT THE GRID CONNECTION,
        # which is what the capacity tariff bills; there is one quarter-hour
@@ -5437,6 +5488,7 @@ class Controller:
                              if len(self.inverters) == 1 else None),
                # SAFETY-97: "gives nothing" is centred on the idle reading.
                idle_w=self._site_idle_w(),
+                hold=self.answer.hold, hold_w=self.answer.hold_w,  # SAFETY-128
                # OPT-11: None unless battery modes are on. SAFETY-85: or while
                # maintenance holds a battery at N>=2, so the loop does not
                # wind past what the others can give and jump when it ends.
@@ -7333,6 +7385,10 @@ class Controller:
                              (inv.refusal_note(), False)):
                if note:
                    out.append({"ok": False, "warn": not red, "text": note})
+        if self.answer.late_seen:                             # SAFETY-128
+            out.append({"ok": False, "warn": True, "id": "late",
+                        "text": messages.row_readings_late(
+                            self.answer.shown_s, self._late_zero)})

        # SAFETY-03. Red while an over-rating clamp is engaged (amber for the
        # integrator bound, SAFETY-40), and the engagement COUNT is shown even
@@ -644,6 +644,31 @@ def row_controller_stalled(age_s, veto_s) -> str:
              f"stuurmodule zet de omvormer na {seconden(veto_s)} op 0 W.")


+def row_readings_late(delay_s, zero=False) -> str:
+    """SAFETY-128: readings show the power request late; `delay_s` the
+    batteries' fitted delay (their own answer included), or None when only
+    the meter has shown it; past the hold, 0 W."""
+    if delay_s is None:
+        if zero:
+            return Bi("Home Assistant readings show requests late, so every "
+                      "inverter is at 0 W.",
+                      "Metingen uit Home Assistant tonen vermogensvraag te "
+                      "laat, omvormers op 0 W.")
+        return Bi("Home Assistant readings show requests late, so control "
+                  "holds the batteries.",
+                  "Metingen uit Home Assistant tonen vermogensvraag te laat, "
+                  "dus de batterijen wachten.")
+    if zero:
+        return Bi(f"Home Assistant readings show requests {seconds(delay_s)} "
+                  f"late, so every inverter is at 0 W.",
+                  f"Metingen uit Home Assistant tonen vermogensvraag "
+                  f"{seconden(delay_s)} te laat, omvormers op 0 W.")
+    return Bi(f"Home Assistant readings show requests about {seconds(delay_s)} "
+              f"late, so control holds the batteries.",
+              f"Metingen uit Home Assistant tonen vermogensvraag zo'n "
+              f"{seconden(delay_s)} te laat, dus de batterijen wachten.")
+
+
 def row_meter_waiting(limit_s) -> str:
    """UX-10: no reading yet since the start, and still inside the limit."""
    return Bi(f"Meter: waiting for the first reading, limit "
@@ -1270,6 +1295,7 @@ WHY_WINNER = {
    "circulation": "Safety stop, inverters worked against each other",
    "stopped": "Control is stopped",
    "inputs missing": "A reading is missing",
+    "readings late": "Home Assistant readings arrive late",
    "no claim was made": "Nothing asked for power",
    # UX-10: the claim reasons main.why_key() can return for a safety or
    # failsafe winner. test_messages.py part 7 finds every one in the code.
@@ -1320,6 +1346,11 @@ def why_missing(what, limit_s) -> str:
    return f"No usable {what} reading for over {seconds(limit_s)}: 0 W"


+def why_late() -> str:
+    """SAFETY-128: readings arrive late, so control holds the batteries."""
+    return "Home Assistant readings arrive late, control holds"
+
+
 def why_waiting(missing_s) -> str:
    """A reading went missing a moment ago: control holds and waits."""
    return f"A reading is missing for {seconds(missing_s)}, control waits"
@@ -1337,6 +1368,8 @@ HINTS = {
    "roster": "Inverter list read: {n} inverters",
    "maint_history": "Maintenance history did not move over cleanly",
    "stop_restored": "{unit}: an earlier safety stop is back, it stays at 0 W",
+    "readings_late": "Home Assistant readings arrive late, control holds",
+    "readings_back": "Home Assistant readings are on time again",
    "battery_stuck": "{unit}: battery power reading stopped changing",
    "battery_back": "{unit}: battery power reading is used again",
    "battery_refuses": "The battery refuses to give power, the add-on asks 0 W",
@@ -1488,6 +1521,10 @@ def status_samples() -> list:
        ("row_controller_stalled", RED, row_controller_stalled(45, 30)),
        ("row_meter_stale", RED, row_meter_stale(40, 10)),
        ("row_meter_waiting", AMBER, row_meter_waiting(30)),
+        ("row_readings_late", AMBER, row_readings_late(30)),
+        ("row_readings_late", AMBER, row_readings_late(30, True)),
+        ("row_readings_late", AMBER, row_readings_late(None)),
+        ("row_readings_late", AMBER, row_readings_late(None, True)),
        ("row_meter", GREEN, row_meter(-350, 2, 3, 340)),
        ("row_meter_frozen", RED, row_meter_frozen()),
        *(("row_freeze_off", AMBER, row_freeze_off(k)) for k in FREEZE_OFF),
@@ -446,6 +446,19 @@ def shaping_suspended(decision, peak_forecast_w, cap_w) -> bool:
    return decision is not None and decision.engaged


+def cap_floor(decision, cap_w):
+    """SAFETY-128: the floor no higher than `cap_w` (the command standing while
+    the readings have not answered it), or `decision` unchanged when None.
+    DECISIONS/SAFETY-128-late-readings.md."""
+    if (cap_w is None or decision is None or decision.floor_w is None
+            or decision.floor_w <= cap_w):
+        return decision
+    return replace(
+        decision, floor_w=float(cap_w), saturated=False,
+        reason=decision.reason + f", held at {float(cap_w):+.0f} W until the "
+        "readings answer the last power request")
+
+
 def claim(decision: PeakDecision) -> Claim | None:
    """The decision as one arbiter claim (`lo` only, `hi` stays `+inf`), or None."""
    if not decision.engaged or decision.floor_w is None:
@@ -476,6 +476,7 @@
      "stopped": "Control is stopped. Every inverter is at 0 W."
    },
    "attn": {
+      "late": "Readings arrive late",
      "home_assistant": "Home Assistant is not answering",
      "controller": "Control is not running",
      "meter": "Meter reading",
@@ -397,6 +397,7 @@
    "peak_not_covered": "Geen piekgrens: deze meter meet geen kwartieren.",
    "control": {"shadow": "Schaduwmodus: elke omvormer blijft op 0 W.", "running": "De regeling is actief.", "stopped": "De regeling is gestopt. Elke omvormer staat op 0 W."},
    "attn": {
+      "late": "Metingen komen te laat",
      "home_assistant": "Home Assistant antwoordt niet",
      "controller": "Regeling is niet actief",
      "meter": "Meting van de meter",
@@ -3080,13 +3080,13 @@ _unit_sources_unrouted = [
    if CLAIM_SCOPE.get(r[0]) == SCOPE_UNIT and "," not in r[1]]
 print(f"    {len(_direct)} direct appends, each read at its own line: "
      + ", ".join(f"main.py:{ln} {s} -> {a}" for s, a, ln in _routing))
-check("all SEVENTEEN of `Controller.cycle()`'s DIRECT appends route through "
+check("all EIGHTEEN of `Controller.cycle()`'s DIRECT appends route through "
      "`self.actuator_of(<string literal>)`, so this scan can read the routing "
      "of EVERY one of them. An append that computed its actuator, or omitted "
      "the argument, or hand-wrote a string, fails HERE rather than being "
      "silently skipped - which is how a scan like this goes quietly vacuous, "
      "and 10f is in this file because that already happened once",
-      len(_direct) == 17
+      len(_direct) == 18
      and all(a is not None and a.startswith("self.actuator_of('")
              for _s, a, _ln in _routing))
 check("⚠️ AND AT EVERY ONE OF THE ELEVEN THE LITERAL IT ROUTES THROUGH IS THE "
@@ -0,0 +1,493 @@
+"""Runnable check for SAFETY-128: control does not act on late readings.
+`python3 test_safety128.py`
+
+When Home Assistant runs behind, its readings arrive late but still change, so
+every staleness gate passes them. The loop corrected again, each cycle, an
+error its last command had already fixed, and the evening give run swung with
+growing export (SAFETY-127 rig: 10 s late, commands -450..+3 790 W, grid to
+-1 947 W). The peak guard pushed to the inverter limit on the same late figures
+(OPT-34 rig F-2). Now a command the battery reading has not answered holds the
+loop and caps the peak guard (app/lateness.py), and readings found late hold,
+then go to 0 W. DECISIONS/SAFETY-128-late-readings.md.
+
+The REAL Controller on TEST-23's plant (tools/safety128_rig.py). "Without the
+gate" is the same run with `Controller._readings_late` returning None, which
+is the tree before this card (the rig runs unchanged on 77fe31b).
+
+1. The give run (two batteries, house 1 800 W), readings 10 s late for 150 s
+   and 30 s late for 300 s: without the gate the swing grows to export below
+   -1 kW; with it the command stays near the last good one, no export below
+   -200 W, and it settles once the lag stops. N=1 too.
+2. The peak guard in a quarter's last 30 s (a charge at the peak aim, readings
+   30 s late, the house steps): it does not go to the inverter limit.
+3. Seen: the late hold says so on the page (EN and NL) and logs once per
+   episode.
+4. Nothing else moves: no-lag runs at 1, 2 and 5 s meters, a load step on a
+   battery with a 6 s dead time (SAFETY-75), start-up, a battery at its
+   cut-out level: within the stated tolerance of the run without the gate.
+5. `Answer` and `compute(hold=)` at their edges.
+
+Mutations (MUTATION.md, purged copies) are listed in the pull request.
+"""
+
+import logging
+import os
+import sys
+from datetime import timedelta
+
+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 safety128_rig as R                                      # noqa: E402
+import app.main as app_main                                    # noqa: E402
+from app import control, lateness, messages                    # noqa: E402
+
+fails = []
+
+
+def check(name, cond):
+    print(f"  {'ok  ' if cond else 'FAIL'} {name}")
+    if not cond:
+        fails.append(name)
+
+
+def no_gate(fn):
+    """`fn()` with the answer gate off: the tree before SAFETY-128."""
+    real = app_main.Controller._readings_late
+    app_main.Controller._readings_late = lambda self, standing_w: None
+    try:
+        return fn()
+    finally:
+        app_main.Controller._readings_late = real
+
+
+def window(rows, t0, t1):
+    return [r for r in rows if t0 <= r[0] < t1]
+
+
+def last_good(rows, t):
+    """The site command standing just before `t`."""
+    return [r for r in rows if r[0] < t][-1][2]
+
+
+def settled_at(rows, t0, band=150.0):
+    """First second from `t0` after which the grid stays within `band` W."""
+    out = None
+    for r in rows:
+        if r[0] < t0:
+            continue
+        if abs(r[1]) > band:
+            out = None
+        elif out is None:
+            out = r[0]
+    return out
+
+
+def swing(rows, t0, t1):
+    w = window(rows, t0, t1)
+    return max(r[1] for r in w) - min(r[1] for r in w)
+
+
+# --------------------------------------------------------------------------- #
+print("1. the give run with readings late")
+ON = 300.0
+CASES = ((10.0, 150.0), (30.0, 300.0))
+for p1, units in ((2.0, ("a", "b")), (2.0, ("a",)), (1.0, ("a", "b")),
+                  (5.0, ("a", "b"))):
+    house = 1800.0 if len(units) == 2 else 1500.0
+    for lag, span in CASES:
+        off = ON + span
+        seen = []
+        new = R.Rig(house=house, lag_s=lag, lag_on=ON, lag_off=off,
+                    units=units, p1_s=p1)
+        new.run(off + 120.0, lambda rig, c, t: seen.append(
+            (t, c.answer.late_seen)) if c.answer.late_seen else None)
+        old = R.Rig(house=house, lag_s=lag, lag_on=ON, lag_off=off,
+                    units=units, p1_s=p1)
+        no_gate(lambda: old.run(off + 120.0))
+        n = f"N={len(units)}, {p1:.0f} s meter, {lag:.0f} s late for {span:.0f} s"
+        wo, wn = window(old.rows, ON, off), window(new.rows, ON, off)
+        good = last_good(new.rows, ON)
+        half = ON + span / 2
+        red = min(r[1] for r in wo) < -1000.0
+        found = min([t for t, _l in seen] or [None])
+        print(f"    {n}: without the gate cmd {min(r[2] for r in wo):.0f}.."
+              f"{max(r[2] for r in wo):.0f} W, grid {min(r[1] for r in wo):.0f}"
+              f"..{max(r[1] for r in wo):.0f} W (swing {swing(old.rows, ON, half):.0f}"
+              f" then {swing(old.rows, half, off):.0f}); with it cmd "
+              f"{min(r[2] for r in wn):.0f}..{max(r[2] for r in wn):.0f} W "
+              f"(last good {good:.0f}), grid {min(r[1] for r in wn):.0f}.."
+              f"{max(r[1] for r in wn):.0f} W, found late "
+              f"{None if found is None else found - ON} s after the start, "
+              f"settled {settled_at(new.rows, off) - off:.0f} s after")
+        if len(units) == 2 and p1 == 2.0:
+            check(f"{n}: without the gate the export goes below -1 kW and the "
+                  f"swing grows (red on 77fe31b)",
+                  red and swing(old.rows, half, off) > swing(old.rows, ON, half))
+        if red:
+            check(f"{n}: found late while the lag lasts", found is not None
+                  and found < off)
+        if p1 < 5.0:
+            # Found within about a minute: at 2 s the brief's bounds; at 1 s
+            # the swing grows faster before it is found, so twice them.
+            lim = 250.0 if p1 == 2.0 else 500.0
+            check(f"{n}: with it the command stays within {lim:.0f} W of the "
+                  f"last good one and no export below -{lim - 50:.0f} W",
+                  all(abs(r[2] - good) <= lim for r in wn)
+                  and min(r[1] for r in wn) >= -(lim - 50.0))
+        elif red:
+            # 5 s meter: only the batteries' fit runs (too few meter values),
+            # so it is found later; the export is cut to under a third.
+            check(f"{n}: with it the export is under a third of the run "
+                  f"without the gate",
+                  min(r[1] for r in wn) >= min(r[1] for r in wo) / 3.0)
+        check(f"{n}: settled within 30 s after the lag stops",
+              settled_at(new.rows, off) is not None
+              and settled_at(new.rows, off) - off <= 30.0)
+
+# --------------------------------------------------------------------------- #
+print("\n2. the peak guard in a quarter's last 30 s")
+# A charge sized to the peak aim (arbitrage on a cheap hour, the shape of the
+# owner's night charge), readings 30 s late from 300 s; the house steps
+# +2 000 W 100 s before the quarter ends (900 s).
+PTS = [(R.BASE + timedelta(hours=h), 3600, 0.02 if h < 2 else 0.40)
+       for h in range(-3, 30)]
+
+
+def peak_run(lag, gate=True, step_at=800.0):
+    seen = []
+
+    def sample(rig, c, t):
+        now = rig.start + timedelta(seconds=t)
+        if int(t) % 300 == 0:
+            c.tariff_plan = rp.plan_at(now, PTS)
+        c.tariff_at = now
+        g = c.peak_guard
+        if g is not None and 870.0 <= t < 900.0 and g.engaged:
+            seen.append((t, g.saturated, float(g.floor_w or 0.0),
+                         float(c.target)))
+    r = R.Rig(house=lambda t: 1000.0 + (2000.0 if t >= step_at else 0.0),
+              lag_s=lag, lag_on=ON, lag_off=2000.0, soc=30.0,
+              extra={"arbitrage_enabled": True,
+                     "cycle_cost_threshold_eur": 0.03})
+    (lambda f: f() if gate else no_gate(f))(lambda: r.run(900.0, sample))
+    return seen, r
+
+
+RATING = sum(R.MAXW.values())
+for lag in (10.0, 30.0):
+    pg_new, _r = peak_run(lag)
+    pg_old, _r = peak_run(lag, gate=False)
+    top_new = max([s[2] for s in pg_new] or [0.0])
+    top_old = max([s[2] for s in pg_old] or [0.0])
+    print(f"    {lag:.0f} s late: the guard's largest ask in the last 30 s "
+          f"without the gate {top_old:.0f} W ({sum(s[1] for s in pg_old)} "
+          f"cycles at the limit), with it {top_new:.0f} W "
+          f"({sum(s[1] for s in pg_new)})")
+    if lag == 30.0:
+        check("without the gate the guard goes to the inverter limit on the "
+              "late projection (red on 77fe31b)",
+              top_old >= RATING and any(s[1] for s in pg_old))
+    check(f"{lag:.0f} s late: with it the guard never goes to the limit and "
+          f"never says it is saturated",
+          top_new < RATING and not any(s[1] for s in pg_new))
+
+# --------------------------------------------------------------------------- #
+print("\n3. the page and the log say so")
+rows_seen = []
+
+
+def watch(rig, c, t):
+    rows_seen.extend((t, r) for r in c.checks() if r.get("id") == "late")
+
+
+late = R.Rig(lag_s=30.0, lag_on=ON, lag_off=ON + 300.0)
+c = late.run(ON + 300.0 + lateness.FIT_GONE_S + 60.0, watch)
+log = [e for e in c.events if "readings late" in e or "readings on time" in e]
+n_late = sum(1 for e in log if "readings late" in e)
+n_back = sum(1 for e in log if "readings on time" in e)
+first = min([t for t, _r in rows_seen] or [None])
+lastr = max([t for t, _r in rows_seen] or [None])
+print(f"    30 s late for 300 s: {n_late} late episode(s), {n_back} end(s), "
+      f"the row from {first} to {lastr} s ({len(rows_seen)} s); "
+      f"{rows_seen[0][1]['text'] if rows_seen else ''}")
+_ok_texts = {str(messages.row_readings_late(None))} | {
+    str(messages.row_readings_late(d)) for d in range(20, 33)}
+check("found late within 70 s of the lag starting, and an amber row says "
+      "so in plain words, EN and NL, with the batteries' delay once they have "
+      "shown it (20-32 s for 30 s late; never a figure from the meter alone)",
+      first is not None and first - ON <= 70.0
+      and all(r["warn"] and not r["ok"] for _t, r in rows_seen)
+      and {str(r["text"]) for _t, r in rows_seen} <= _ok_texts
+      and rows_seen[-1][1]["text"].nl.startswith(
+          "Metingen uit Home Assistant tonen vermogensvraag"))
+rows5 = []
+late5 = R.Rig(lag_s=30.0, lag_on=ON, lag_off=ON + 300.0, p1_s=5.0)
+late5.run(ON + 300.0, lambda rig, c, t: rows5.extend(
+    str(r["text"]) for r in c.checks() if r.get("id") == "late"))
+print(f"    5 s meter, 30 s late: {sorted(set(rows5))}")
+check("at a 5 s meter (the batteries' fit) the row names the delay: about "
+      "20-32 s for 30 s late",
+      rows5 and set(rows5) <= _ok_texts and any("about" in x for x in rows5))
+check("logged once for the episode, and once when it ends, not per cycle",
+      n_late == 1 and n_back == 1)
+check("the row goes once a fit shows the readings on time, or 2 minutes "
+      "after the last fit, at most 160 s after the lag (a steady site shows "
+      "nothing to fit)",
+      lastr is not None
+      and lastr - (ON + 300.0) <= lateness.FIT_S + lateness.FIT_GONE_S
+      and not [r for r in c.checks() if r.get("id") == "late"])
+# The late verdict through the real cycle(): readings found late (30 s), then
+# the gate is frozen with its verdict 5 s old (held) or 20 s old (past
+# stale_input_s, 15 s).
+seen_zero = {}
+
+
+def verdict(after_s):
+    def at(rig, c, t):
+        if t == 500.0:
+            c.answer.observe = lambda *a, **k: None
+            c.answer.late_seen, c.answer.late_at = True, c._now_mono - after_s
+            seen_zero[after_s] = [c.target]
+        if t == 506.0:
+            seen_zero[after_s] += [
+                c.target, c.reason, [r["text"] for r in c.checks()
+                                     if r.get("id") == "late"], c.why_words]
+    v = R.Rig(lag_s=30.0, lag_on=ON, lag_off=2000.0)
+    v.run(507.0, at)
+
+
+verdict(5.0)
+verdict(20.0)
+held, zero = seen_zero[5.0], seen_zero[20.0]
+print(f"    late verdict 5 s old: {held[:3]}; 20 s old: {zero[:3]}")
+check("the late verdict holds the request until stale_input_s, then every "
+      "inverter goes to 0 W, and the row says so (EN and NL)",
+      held[1] == held[0] and held[2].startswith("readings late")
+      and zero[1] == 0.0 and zero[4].startswith(
+          "Home Assistant readings arrive late: 0 W")
+      and len(zero[3]) == 1 and "every inverter is at 0 W" in zero[3][0]
+      and "omvormers op 0 W" in zero[3][0].nl)
+on_time = R.Rig(house=lambda t: 600.0 + (2500.0 if t >= 200.0 else 0.0))
+c = on_time.run(600.0)
+check("readings on time, a load step: no late episode, no row",
+      not [e for e in c.events if "readings late" in e]
+      and not c.answer.late_seen)
+
+# --------------------------------------------------------------------------- #
+print("\n4. nothing else moves")
+STEP = dict(house=lambda t: 600.0 + (2500.0 if t >= 200.0 else 0.0))
+
+
+def compare(name, tol_w, **kw):
+    a = R.Rig(**kw)
+    a.run(500.0)
+    b = R.Rig(**kw)
+    no_gate(lambda: b.run(500.0))
+    diff = max(abs(x[2] - y[2]) for x, y in zip(a.rows, b.rows))
+    sa, sb = settled_at(a.rows, 200.0), settled_at(b.rows, 200.0)
+    print(f"    {name}: largest command difference {diff:.0f} W, settled "
+          f"{sa - 200.0 if sa else None} s after the step (without the gate "
+          f"{sb - 200.0 if sb else None} s)")
+    return diff, sa, sb, a
+
+
+for p1 in (1.0, 2.0, 5.0):
+    for units in (("a", "b"), ("a",)):
+        d, sa, sb, _a = compare(f"no lag, {p1:.0f} s meter, N={len(units)}, "
+                                f"house 600 -> 3 100 W", 0.0, p1_s=p1,
+                                units=units, **STEP)
+        check(f"{p1:.0f} s meter, N={len(units)}: settles within 10 s of the "
+              f"run without the gate",
+              sa is not None and sb is not None and sa - sb <= 10.0)
+d, sa, sb, a75 = compare("SAFETY-75 shape, 6 s dead time", 0.0, dead_s=6.0,
+                         **STEP)
+check("6 s dead time (SAFETY-75): the same commands as without the gate, and "
+      "no late episode (the fit says 5-7 s, under 8 s)",
+      d == 0.0 and not any("readings late" in e for e in a75.c.events))
+d, sa, sb, a0 = compare("start-up, the house at 2 000 W from the first second",
+                        0.0, house=2000.0)
+check("start-up: the first 120 s reach the house within 30 s, as without the "
+      "gate, and no late episode",
+      settled_at(a0.rows, 0.0) is not None and settled_at(a0.rows, 0.0) <= 30.0
+      and not any("readings late" in e for e in a0.c.events))
+for on, off in ((45, 60), (30, 30)):
+    house = (lambda t, on=on, off=off:
+             400.0 + (2000.0 if t % (on + off) < on else 0.0))
+    oven = R.Rig(house=house, noise=80.0)
+    oven.run(1500.0)
+    oven0 = R.Rig(house=house, noise=80.0)
+    no_gate(lambda: oven0.run(1500.0))
+    check(f"an oven cycling 2 kW {on} s on, {off} s off (2 s meter, readings "
+          f"on time): never taken for late readings ({oven.c.answer.fits} "
+          "fits), the same commands as without the gate",
+          oven.c.answer.fits > 100 and not any(
+              "readings late" in e for e in oven.c.events)
+          and [r[2] for r in oven.rows] == [r[2] for r in oven0.rows])
+# One battery that empties to its cut-out level under an oven (1 s meter):
+# its fit lined the old movement up as 85 s late (round 2, before the fix).
+emp = R.Rig(house=lambda t: 400.0 + (2000.0 if t % 105 < 45 else 0.0),
+            noise=150.0, soc=10.6, units=("a",), p1_s=1.0)
+emp.run(1800.0)
+check("one battery emptying to its cut-out level under a cycling oven (1 s "
+      "meter): not taken for late readings",
+      not any("readings late" in e for e in emp.c.events))
+emp2 = R.Rig(house=lambda t: 400.0 + (2000.0 if t % 60 < 30 else 0.0),
+             noise=150.0, soc=10.2, units=("a",), p1_s=2.0)
+emp2.run(1800.0)
+check("one empty battery under an oven cycling 30/30 s (2 s meter): its "
+      "requests do not start, but it gives nothing, so that is no evidence "
+      "for the meter fit",
+      not any("readings late" in e for e in emp2.c.events))
+# The recorded house (2026-09-02, its first 2 hours, modes off) at a 2 s
+# meter: the meter fit alone read it as up to 65 s late here (review, B1).
+from datetime import datetime as _dt, timezone as _tz          # noqa: E402
+_tick, rp.TICK = rp.TICK, 2.0
+_late = []
+try:
+    _st, _rc = rp.run("modes_off", rp.load_house(["2026-09-02"]),
+                      rp.epex_points(),
+                      _dt.fromisoformat("2026-09-02T00:00:00+02:00")
+                      .astimezone(_tz.utc), 7200.0,
+                      check=lambda c, h, now, pr: _late.append(
+                          c.answer.late_seen))
+finally:
+    rp.TICK = _tick
+check(f"the recorded house, 2 hours at a 2 s meter: {_rc.answer.fits} fits, "
+      "never taken for late readings",
+      _rc.answer.fits > 100 and not any(_late))
+import safety94_rig as s94                                     # noqa: E402
+slow = [(n, tau, tick) for n in (1, 2) for tau in (10.0, 20.0)
+        for tick in (1.0, 2.0)
+        if any("readings late" in e for e in s94.run(
+            n, s94.reversal(300.0, -2500.0, 800.0), 600.0, tau=tau,
+            tick=tick)["c"].events)]
+check("a slow battery (10 or 20 s lag, SAFETY-85/94's rig) reversing out of a "
+      "charge, readings on time: never taken for late readings, N=1 and N=2, "
+      f"1 and 2 s meters (taken: {slow})", not slow)
+for name, kw in (("at their cut-out level", dict(soc=10.5)),
+                 ("A refusing from 200 s",
+                  dict(cut=lambda u, t: u == "a" and t >= 200.0))):
+    x = R.Rig(house=1800.0, **kw)
+    x.run(600.0)
+    y = R.Rig(house=1800.0, **kw)
+    no_gate(lambda: y.run(600.0))
+    check(f"readings on time, batteries {name}: not taken for late "
+          f"readings, the same commands as without the gate",
+          not any("readings late" in e for e in x.c.events)
+          and [r[2] for r in x.rows] == [r[2] for r in y.rows])
+
+# --------------------------------------------------------------------------- #
+print("\n5. the rules at their edges")
+check("LATE_S is SAFETY-75's slowest healthy answer: 6 + 6 + 10 + 1 = 23 s",
+      lateness.LATE_S == 23.0)
+check("ANSWER_W is a probe's answer (100 W)",
+      lateness.ANSWER_W == control.PROBE_ANSWER_W == 100.0)
+
+
+check("late from ON_S 9.5 s, on time again under OFF_S 6.5 s",
+      (lateness.ON_S, lateness.OFF_S) == (9.5, 6.5))
+
+
+def fit(delay, *, follows=True, step_every=20, dur=300, tau=0.0, units="ab"):
+    """`Delay` on batteries whose readings, published every 10 s at their own
+    phase, show each request `delay` s late (through a `tau` s lag), or never
+    (`follows` False)."""
+    import math
+    import random
+    rng, d = random.Random(7), lateness.Delay()
+    edges = [0]
+    while edges[-1] < dur:
+        edges.append(edges[-1] + step_every * rng.uniform(0.5, 1.5))
+    cmd = lambda t: 1500.0 + (600.0 if sum(e <= t for e in edges) % 2 else 0.0)
+    act, shown = 1500.0, {}
+    for t in range(0, dur):
+        want = cmd(t - delay) if t >= delay else 1500.0
+        act = want if not tau else act + (want - act) * (1 - math.exp(-1 / tau))
+        for k, u in enumerate(units):
+            if (t + 4 * k) % 10 == 0:
+                shown[u] = round(act + rng.uniform(-3, 3)) if follows else 900
+            d.add(float(t), u, cmd(t), shown.get(u))
+    return d.estimate()
+
+
+got = {k: fit(k) for k in (0, 6, 10, 30, 60)}
+print(f"    fitted delays: {got}; one battery {fit(10, units='a')}")
+check("the fit finds the readings' delay (0, 6, 10, 30, 60 s) to within 2 s "
+      "(it reads the request over the 2 s before), also with one battery",
+      all(v is not None and abs(v - k) <= 2.0 for k, v in got.items())
+      and abs((fit(10, units="a") or 0.0) - 10.0) <= 2.0)
+slow = [fit(0, tau=tau, step_every=s) for tau in (3.0, 10.0, 20.0)
+        for s in (10, 20, 40)]
+check("a battery that does not follow gives no fit, nor does a request that "
+      f"does not move, and a slow battery (3, 10, 20 s lag) is never late "
+      f"({slow})",
+      fit(10, follows=False) is None and fit(10, step_every=10_000) is None
+      and all((d or 0.0) < lateness.ON_S for d in slow))
+
+
+def gate(steps, exempt=(), late_seen=True):
+    """[(t, command, battery reading, meter)] through one Answer, its fit
+    replaced by `late_seen`; after each: (pending, hold, late s, peak cap)."""
+    a = lateness.Answer()
+    a.late_seen = late_seen
+
+    def one(t, cmd, batt, grid):
+        a.observe(float(t), cmd, batt, grid_w=grid, exempt=t in exempt)
+        return (a.ask is not None, a.hold, a.late_s(float(t)),
+                a.peak_cap(cmd))
+    return a, [one(*x) for x in steps]
+
+
+STEP = [(0, 1000, 1000, 500), (2, 1500, 1000, 500)]
+HELD = STEP + [(t, 1500, 1000, 500) for t in range(4, 40, 2)]
+a, out = gate(HELD, late_seen=False)
+check("readings on time: an unanswered ask holds nothing, caps nothing and "
+      "is never late (a battery at its limit)",
+      out[-1][0] and all(o[1] == 0 and o[2] is None and o[3] is None
+                         for o in out))
+a, out = gate(STEP + [(4, 1500, 1000, 500), (6, 1500, 1450, 60)])
+check("readings late: the ask holds the loop up and caps the peak guard at "
+      "what stands until the battery reading answers",
+      out[1][1:] == (1, None, 1500.0) and out[2][1:] == (1, None, 1500.0)
+      and out[3] == (False, 0, None, None))
+a, out = gate(HELD)
+check("...and with no move towards it for 23 s it is late (control holds, "
+      "then 0 W)",
+      [o[2] for o in out].index(0.0) == len([t for t, *_ in HELD
+                                             if t - 2 < 23]))
+a, out = gate(HELD + [(40, 1500, 1000, 380)])
+check("...which ends when a reading starts towards the ask",
+      out[-2][2] is not None and out[-1][2] is None and out[-1][0])
+a, out = gate(HELD, exempt=set(range(2, 40, 2)))
+check("exempt (a battery gives nothing under its ask, or refuses): no hold "
+      "and no late verdict, the cap stays",
+      all(o[1] == 0 and o[2] is None for o in out) and out[-1][3] == 1500.0)
+a, out = gate([(0, 1000, 1000, 500), (2, 1090, 1000, 500),
+               (4, 1000, 1000, 500)])
+check("a move under 100 W is not an ask", not any(o[0] for o in out))
+a, out = gate(STEP + [(4, 1050, 1000, 500)])
+check("an ask taken back within 100 W of the reading is withdrawn",
+      out[2][0] is False)
+T = control.Tuning(max_w=5000.0)
+base = dict(prev_w=1500.0, grid_w=800.0, actual_w=1000.0, tuning=T,
+            i_w=1500.0)
+check("compute(hold=+1): the loop may not push past the standing command, "
+      "but may come back",
+      control.compute(**base).target_w > 1500.0
+      and control.compute(**base, hold=1).target_w == 1500.0
+      and control.compute(**base, hold=1).reason == control.WAITING
+      and control.compute(**dict(base, grid_w=-800.0), hold=1).target_w
+      < 1500.0)
+check("compute(hold=-1) mirrors it, and hold=0 is the law as it was",
+      control.compute(**dict(base, grid_w=-800.0), hold=-1).target_w == 1500.0
+      and control.compute(**base, hold=0) == control.compute(**base))
+
+print()
+if fails:
+    print(f"{len(fails)} FAILED: " + ", ".join(fails))
+    sys.exit(1)
+print("all checks passed")
@@ -61,6 +61,9 @@ def without_fix(fn):
    """Run `fn` with the gate's old clock and the old refusal evidence."""
    real_f, real_c = app_inverter.Freshness, app_main.compute
    real_p = app_main.REFUSED_PROGRESS_W
+    real_l = app_main.Controller._readings_late
+    # SAFETY-128: that tree had no late-readings gate either.
+    app_main.Controller._readings_late = lambda self, standing_w: None
    app_inverter.Freshness = Before94
    app_main.compute = lambda *a, **k: real_c(*a, **dict(k, gave_nothing=None))
    app_main.REFUSED_PROGRESS_W = float("inf")
@@ -69,6 +72,7 @@ def without_fix(fn):
    finally:
        app_inverter.Freshness, app_main.compute = real_f, real_c
        app_main.REFUSED_PROGRESS_W = real_p
+        app_main.Controller._readings_late = real_l


 # ============================================================================ #
@@ -68,10 +68,14 @@ def without(fn):
    Controller._held_out_w = lambda self, live: 0.0
    Controller._reseed_drop = lambda self, live: setattr(
        self, "_live_was", frozenset(live))
+    real_late = Controller._readings_late
+    # SAFETY-128: that tree had no late-readings gate either.
+    Controller._readings_late = lambda self, standing_w: None
    try:
        return fn()
    finally:
        Controller._held_out_w, Controller._reseed_drop = fixed, real_drop
+        Controller._readings_late = real_late


 def run(n=2, *, house=lambda t: 2400.0, dur=600.0, store=None, opt=None,
@@ -0,0 +1,284 @@
+#!/usr/bin/env python3
+"""SAFETY-128: the REAL Controller with Home Assistant readings arriving late.
+
+    python3 tools/safety128_rig.py            # prints a few runs' summaries
+
+The plant is TEST-23's (SAFETY-127 rig, t127_plant.py): two batteries
+(A 5 000 W, B 4 600 W) that ramp at 5 000 W/s and then follow a 1 s lag; each
+battery reading is published every 10 s (A at :x6, B at :x1.6); the meter every
+2 s; the house is `house` W plus seeded +-`noise` W, new each second.
+
+`p1_s` sets the meter's period, `dead_s` a command dead time (SAFETY-75's
+laggy battery), `units` one battery ("a") or two.
+
+Home Assistant runs `lag_s` seconds behind (a number, or a function of t) between `lag_on` and `lag_off`:
+every reading the add-on gets (meter, battery power, battery level) is the
+one published `lag_s` seconds earlier. When the lag starts, nothing new comes
+for `lag_s` seconds, then the backlog; when it stops, the readings jump to
+now. Commands reach the plant at once (t127_shim.py's lag mode).
+
+The add-on reads every 1 s and runs a cycle on a new meter value or after
+`cycle_floor_s`, as `run_control()` does. Uses only the Controller API that
+release/1.0 77fe31b has, so the same file runs on the tree before SAFETY-128.
+"""
+
+import asyncio
+import math
+import os
+import random
+import sys
+import tempfile
+import time
+from datetime import datetime, timedelta, timezone
+
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+import app.main as m                                      # noqa: E402
+from app.main import Controller                           # noqa: E402
+from app.p1 import make_sample, split_signed              # noqa: E402
+
+# 18:00 local (CET) on a weekday: the evening give run.
+BASE = datetime(2026, 11, 4, 17, 0, tzinfo=timezone.utc)
+UNITS = ("a", "b")
+MAXW = {"a": 5000.0, "b": 4600.0}
+CAPWH = {"a": 15360.0, "b": 20480.0}
+PHASE = {"a": 6.0, "b": 1.6}
+BPER = 10.0
+P1PER = 2.0
+RAMP = 5000.0
+LAG = 1.0
+
+def options(units=UNITS):
+    o = dict(OPTIONS)
+    o["inverters"] = [
+        {"name": f"inverter-{u}", "setpoint_entity": f"number.sp_{u}",
+         "soc_entity": f"sensor.soc_{u}", "batt_entity": f"sensor.batt_{u}",
+         "max_w": int(MAXW[u]), "bms_soc_floor": 10,
+         "capacity_kwh": CAPWH[u] / 1000.0} for u in units]
+    return o
+
+
+OPTIONS = {
+    "meter_entity": "sensor.grid", "meter_source": "ha_signed",
+    "p1_net_entity": "sensor.grid", "meter_phases": 1, "meter_max_age_s": 30,
+    "peak_cap_w": 3500, "peak_margin_w": 50, "peak_soc_floor": 20,
+    "gain": 0.6, "slew_w": 0, "target_grid_w": -10, "deadband_w": 15,
+    "step_w": 10, "heartbeat_s": 10, "stale_input_s": 15,
+    "cycle_floor_s": 15, "saturation_w": 500, "saturation_cycles": 3,
+    "auto_start": True, "battery_modes_enabled": False,
+    "arbitrage_enabled": False, "bms_soc_floor": 10,
+}
+
+
+class _Store:
+    def __init__(self):
+        from app.store import DEFAULTS
+        self.data = dict(DEFAULTS)
+
+    def set(self, k, v):
+        self.data[k] = v
+
+    def get_time(self, k):
+        v = self.data.get(k)
+        return datetime.fromisoformat(v) if v else None
+
+    def set_time(self, k, when):
+        self.data[k] = when.isoformat() if when else None
+
+
+class _Pub:
+    enabled = False
+
+    def publish(self, *a, **k):
+        pass
+
+    def close(self):
+        pass
+
+
+class Plant:
+    """The batteries, their registers and the meter, in 0.1 s steps."""
+
+    def __init__(self, house, noise, seed, soc, cut=None, units=UNITS,
+                 p1_s=P1PER, dead_s=0.0):
+        self.house_fn, self.noise, self.seed = house, noise, seed
+        self.units, self.p1_s, self.dead_s = units, p1_s, dead_s
+        self.cut = cut or (lambda u, t: False)
+        self.cmd = {u: 0.0 for u in units}
+        self.queue = []                       # (t, unit, command), dead time
+        self.tgt = {u: 0.0 for u in units}
+        self.act = {u: 0.0 for u in units}
+        self.soc = {u: float(soc) for u in units}
+        self.reg = {u: 0.0 for u in units}
+        self.slot = {u: None for u in units}
+        self.p1 = None
+        self.p1_n = 0
+        self.t = 0.0
+        self.house = float(house(0.0))
+        self.hist = []          # (t, p1 value, p1 index, {reg}, {soc})
+
+    def grid(self):
+        return self.house - sum(self.act.values())
+
+    def advance(self, t):
+        while self.t < t - 1e-9:
+            self.t = round(self.t + 0.1, 6)
+            sec = int(math.floor(self.t + 1e-9))
+            rs = random.Random(self.seed * 1000003 + sec)
+            self.house = (float(self.house_fn(self.t))
+                          + rs.uniform(-self.noise, self.noise))
+            while self.queue and self.queue[0][0] <= self.t + 1e-9:
+                _t, u, v = self.queue.pop(0)
+                self.cmd[u] = v
+            for u in self.units:
+                want = max(-MAXW[u], min(MAXW[u], self.cmd[u]))
+                if self.cut(u, self.t):
+                    want = 0.0
+                if self.soc[u] <= 10.0 and want > 0:
+                    want = 0.0
+                if self.soc[u] >= 100.0 and want < 0:
+                    want = 0.0
+                d = want - self.tgt[u]
+                self.tgt[u] += math.copysign(min(abs(d), RAMP * 0.1), d)
+                self.act[u] += ((self.tgt[u] - self.act[u])
+                                * (1 - math.exp(-0.1 / LAG)))
+                self.soc[u] = max(0.0, min(100.0, self.soc[u] - self.act[u]
+                                           * 0.1 / 3600.0 / CAPWH[u] * 100.0))
+                slot = math.floor((self.t - PHASE[u]) / BPER + 1e-9)
+                if slot != self.slot[u]:
+                    self.slot[u] = slot
+                    self.reg[u] = float(round(self.act[u]))
+            if abs(self.t / self.p1_s - round(self.t / self.p1_s)) < 1e-6:
+                self.p1 = round(self.grid(), 1)
+                self.p1_n += 1
+            self.hist.append((self.t, self.p1, self.p1_n, dict(self.reg),
+                              {u: round(v, 2) for u, v in self.soc.items()}))
+        del self.hist[:-3000]
+
+    def view(self, t, lag_s, lag_on, lag_off):
+        """What Home Assistant shows at `t`: (p1, p1 index, regs, socs)."""
+        lag_s = lag_s(t) if callable(lag_s) else lag_s
+        if lag_s and lag_on <= t < lag_off:
+            want = max(lag_on, t - lag_s)
+            for row in reversed(self.hist):
+                if row[0] <= want + 1e-9:
+                    return row[1:]
+            return self.hist[0][1:]
+        return (self.p1, self.p1_n, dict(self.reg),
+                {u: round(v, 2) for u, v in self.soc.items()})
+
+
+class _Hass:
+    def __init__(self, rig):
+        self.rig = rig
+
+    async def limits(self, e):
+        return (-MAXW[e[-1]], MAXW[e[-1]], 1.0)
+
+    async def call(self, *a):
+        return True
+
+    async def state(self, e):
+        return None
+
+    async def number(self, e, invert=False):
+        _p1, _n, regs, socs = self.rig.seen
+        u = e[-1]
+        if e.startswith("sensor.soc"):
+            return socs[u]
+        if e.startswith("sensor.batt"):
+            return regs[u]
+        return None
+
+    async def set_number(self, e, v):
+        p = self.rig.plant
+        p.queue.append((p.t + p.dead_s, e[-1], float(v)))
+        self.rig.writes.append((self.rig.plant.t, e[-1], float(v)))
+        return True
+
+
+class Rig:
+    def __init__(self, house=1800.0, noise=50.0, seed=90, soc=60.0,
+                 lag_s=0.0, lag_on=0.0, lag_off=0.0, extra=None, cut=None,
+                 start=BASE, units=UNITS, p1_s=P1PER, dead_s=0.0):
+        house_fn = house if callable(house) else (lambda t, h=house: h)
+        self.plant = Plant(house_fn, noise, seed, soc, cut, units, p1_s,
+                           dead_s)
+        self.lag = (lag_s, lag_on, lag_off)
+        self.o = dict(options(units), **(extra or {}))
+        self.start = start
+        self.writes = []
+        self.rows = []
+        self.seen = None
+
+    def run(self, dur, sample=None):
+        """Run `dur` s. Rows: (t, true grid, site command, site actual,
+        loop reason, controller reason). `sample(rig, c, t)` per second."""
+        async def go():
+            db = os.path.join(tempfile.mkdtemp(prefix="s128-"), "tariff.db")
+            c = Controller(self.o, _Hass(self), _Store(), _Pub(),
+                           stop=asyncio.Event(), peak_db_path=db)
+            for i in c.inverters:
+                i.dev_min, i.dev_max = -MAXW[i.name[-1]], MAXW[i.name[-1]]
+            c.auto = True
+            self.c = c
+            real_dt = m.datetime
+            clock = [self.start]
+
+            class _DT(real_dt):
+                @classmethod
+                def now(cls, tz=None):
+                    return clock[0] if tz is None else clock[0].astimezone(tz)
+
+            m.datetime = _DT
+            floor = float(self.o.get("cycle_floor_s", 15))
+            last_grid, last_cycle, last_n = object(), None, None
+            try:
+                t = 0.0
+                while t < dur:
+                    self.plant.advance(t)
+                    now = self.start + timedelta(seconds=t)
+                    clock[0] = now
+                    self.seen = self.plant.view(t, *self.lag)
+                    p1, n = self.seen[0], self.seen[1]
+                    if p1 is not None and n != last_n:
+                        last_n = n
+                        imp, exp = split_signed(p1)
+                        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)
+                    if (c.grid != last_grid or last_cycle is None
+                            or t - last_cycle >= floor):
+                        last_grid, last_cycle = c.grid, t
+                        await c.cycle()
+                    self.rows.append((
+                        t, self.plant.grid(), sum(self.plant.cmd.values()),
+                        sum(self.plant.act.values()), c.loop_reason,
+                        c.reason))
+                    if sample is not None:
+                        sample(self, c, t)
+                    t += 1.0
+            finally:
+                m.datetime = real_dt
+            return c
+        return asyncio.run(go())
+
+
+def summary(rows, t0, t1):
+    """Over [t0, t1): (min cmd, max cmd, min grid, max grid, s of export
+    below -200 W, s below -1 000 W)."""
+    sel = [r for r in rows if t0 <= r[0] < t1]
+    return (min(r[2] for r in sel), max(r[2] for r in sel),
+            min(r[1] for r in sel), max(r[1] for r in sel),
+            sum(1 for r in sel if r[1] < -200), sum(1 for r in sel
+                                                   if r[1] < -1000))
+
+
+if __name__ == "__main__":
+    for lag in (0.0, 10.0, 30.0):
+        r = Rig(lag_s=lag, lag_on=300.0, lag_off=450.0)
+        r.run(600.0)
+        print(f"lag {lag:4.0f} s: before {summary(r.rows, 200, 300)}")
+        print(f"            during {summary(r.rows, 300, 450)}")
+        print(f"            after  {summary(r.rows, 480, 600)}")