SAFETY-52: a battery that refuses is asked for 0 W, with a 200 W probe every 15 min

At the BMS cut-out the saturation freeze held the last request for hours
(+5000 W for 11.87 h on 09-06, +1940 W for 3 h 55 m on 09-19) until the grid
error changed sign. compute() now carries a refused direction: after
SETTLE_CYCLES of a ~0 W reading against a larger ask it holds that direction
at 0 W, probes 200 W (below the gate's 250 W) every 15 minutes, and lets go
on charge, an answered probe, stop/start or another writer. A stale-reading
trip on a frozen ~0 W reading seeds the same hold, which ends SAFETY-59's
~70 s cycle. One inverter only; no SoC in the loop (SAFETY-25 Option A).

test_refusal.py drives the real Controller and gate; tools/replay_refusal.py
replays the 16-day capture. test_clamp.py and test_delivery.py re-baselined
where they asserted the old hold. DECISIONS/SAFETY-52 has the record and what
SAFETY-58/59 must take into account.

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

goodwe_controller/app/control.py

@@ -265,6 +265,30 @@ _SAT_COUNT_CAP = SETTLE_CYCLES + 1                           # 13
 # `slew_limit_w()` and therefore with the rail.
 SLEW_LEAD_STEPS = 1
 
+# ---------------------------------------------------------------------------
+# SAFETY-52. A BATTERY THAT REFUSES IS ASKED FOR 0 W, NOT HELD AT ITS LAST ASK.
+#
+# At the BMS cut-out the pack delivers ~0 W whatever it is asked, so the
+# saturation freeze below holds the command where it stood (the recorded
+# 09-06 case: +5000 W for 11.87 h) until the grid error changes sign. The
+# freeze's own exit cannot help: a reading of ~0 against a large ask is inside
+# the interval a limit can produce. So a refused DIRECTION is held at 0 W,
+# carried between cycles like `sat_count`, and left again when the loop wants
+# the other direction, when a small probe is answered, or when the caller
+# resets it (stop, start, another writer). The record is DECISIONS/SAFETY-52.
+#
+# PROBE_W is below freshness.MOVE_W (250 W) on purpose: a probe that small can
+# never arm the stale-reading gate, so it cannot start the gate's ~70 s cycle.
+# test_refusal.py pins the inequality. The cadence and length are the owner's
+# 2026-09-27 answer (every 15 minutes) and freshness.BATT_OBLIGED_S twice over
+# (17 s is how long a healthy reading needs to show a command).
+REFUSED = "battery refuses"
+PROBING = "battery probe"
+PROBE_W = 200.0
+PROBE_ANSWER_W = PROBE_W / 2
+PROBE_EVERY_S = 900.0
+PROBE_S = 34.0
+
 
 @dataclass(frozen=True)
 class Tuning:
@@ -346,6 +370,9 @@ class Decision:
     i_bound_w: float = 0.0
     requested_w: float = 0.0
     clamped_w: float = 0.0
+    # SAFETY-52. The refused direction to carry back in (+1 discharge, -1
+    # charge, 0 none), or None when the caller does not carry it.
+    refused: int | None = None
 
 
 def slew_limit_w(tuning: Tuning) -> float:
@@ -442,6 +469,8 @@ def compute(
     tuning: Tuning,
     sat_count: int = 0,
     i_w: float | None = None,
+    refused: int | None = None,
+    probe: bool = False,
 ) -> Decision:
     """One control cycle. A cycle is one meter update (~5 s on a HomeWizard P1).
 
@@ -449,6 +478,9 @@ def compute(
     `grid_w`   net grid power, + = importing
     `actual_w` what the inverter reports it is doing, + = discharging
     `i_w`      the carried integrator, or None to seed it from `prev_w`
+    `refused`  SAFETY-52's carried refused direction, or None to leave it out
+               (the `i_w=None` equivalence path does)
+    `probe`    the caller's clock says a refused direction may try PROBE_W now
     """
     reason = "tracking"
 
@@ -739,6 +771,26 @@ def compute(
             target = min(target, prev_w) if prev_w > 0 else max(target, prev_w)
             reason = "saturated-freeze"
 
+    # --- SAFETY-52: a refused direction is held at 0 W ----------------------
+    # Engages only where the freeze has held for SETTLE_CYCLES and the unit
+    # delivers ~nothing: a reading within `saturation_w` of 0 against an ask
+    # beyond it is a refusal, not a slow plant. The drop to 0 skips the slew
+    # limit because it only removes an ask the battery is not meeting.
+    if refused is not None:
+        if (refused == 0 and frozen and sat_count >= SETTLE_CYCLES
+                and abs(prev_w) > tuning.saturation_w
+                and abs(actual_w) < tuning.saturation_w):
+            refused = 1 if prev_w > 0 else -1
+        if refused and refused * i_w < 0:
+            refused = 0                          # the loop wants the other way
+        elif refused and probe and refused * actual_w >= PROBE_ANSWER_W:
+            refused = 0                          # the probe was answered
+        elif refused:
+            wants = refused * i_w > 0
+            i_w = 0.0
+            target = refused * PROBE_W if probe and wants else 0.0
+            reason = PROBING if probe and wants else REFUSED
+
     # --- quantise ----------------------------------------------------------
     # 10 W. The register is 1 W and the inverter reports at 1 W, but its
     # response lands on a coarser ladder (~17.6 W measured at ~900 W, consistent
@@ -749,7 +801,7 @@ def compute(
 
     return Decision(float(target), sat_count, frozen, reason, float(i_w),
                     i_clamped, clamped, float(i_bound_w), float(want),
-                    float(clamped_w))
+                    float(clamped_w), refused)
 
 
 def maintenance_charge_floor(

goodwe_controller/app/main.py

@@ -39,6 +39,7 @@ from .arbiter import (
     P_LOOP, P_MAINT_SHAPE, P_MAINTENANCE, P_PEAK, P_SAFETY,
     Claim, Resolution, actuator_for, resolve,
 )
+from . import control as _ctl
 from .control import Tuning, compute, maintenance_charge_floor, peak_at_risk
 from .delivery import (
     DELIVERY_OPTION_DEFAULTS, DeliveryConfig, UnitDelivery,
@@ -241,6 +242,10 @@ def why_key(winner: str, claims) -> str:
     disagreement"). A failsafe with no claim of its own is the arbiter's "no
     claim was made", or main.py's refusal to split the power ("unsplit").
     """
+    if winner == "loop":
+        # SAFETY-52: a loop holding a refused direction says so.
+        return next((c.reason for c in claims if c.source == "loop"
+                     and c.reason in (_ctl.REFUSED, _ctl.PROBING)), winner)
     if winner in ("safety", "failsafe"):
         return next((c.reason for c in claims
                      if c.source == winner and c.kind == "set"),
@@ -925,6 +930,12 @@ class Controller:
         self.target = 0.0
         self.sat_count = 0
         self.i_w = 0.0        # the loop's integrator, carried between cycles
+        # SAFETY-52. The direction the battery refuses (+1 / -1 / 0), carried
+        # like `i_w`, and when the refusal (or its last probe) started.
+        self.batt_refused = 0
+        self.batt_refused_at = None
+        self._now_mono = None
+        self._refusal_auto = False
         # TEL-10. What the last cycle's loop did, kept for publication. Seeded
         # to the SAME values the "stopped or blind" branch of `cycle()` writes,
         # because before the first cycle the loop has not run - which is the
@@ -1058,6 +1069,68 @@ class Controller:
         self.loop_pass_mono = None
 
     # -- helpers -------------------------------------------------------------
+    # --- SAFETY-52: a battery that refuses is asked for 0 W ------------------
+    def _refusal_probe(self) -> bool:
+        """True while a refused direction may try `PROBE_W` (every 15 min)."""
+        if (not self.batt_refused or self.batt_refused_at is None
+                or self._now_mono is None):
+            return False
+        held = self._now_mono - self.batt_refused_at
+        if held >= _ctl.PROBE_EVERY_S + _ctl.PROBE_S:
+            self.batt_refused_at = self._now_mono
+            return False
+        return held >= _ctl.PROBE_EVERY_S
+
+    def _refusal_start(self, sign: int, evidence: str) -> None:
+        self.batt_refused = sign
+        self.batt_refused_at = self._now_mono
+        self.log_event(f"BATTERY REFUSES {evidence}",
+                       hint=messages.hint("battery_refuses"))
+        _LOG.info("The battery refuses to give power, so the add-on asks 0 W "
+                  "and tries %.0f W every %.0f minutes: BATTERY_REFUSES.",
+                  _ctl.PROBE_W, _ctl.PROBE_EVERY_S / 60)
+        _LOG.debug("Evidence: BATTERY_REFUSES: %s.", evidence)
+
+    def _refusal_end(self, why: str) -> None:
+        if not self.batt_refused:
+            return
+        self.batt_refused, self.batt_refused_at = 0, None
+        self.log_event(f"BATTERY REFUSES ENDED: {why}",
+                       hint=messages.hint("battery_gives"))
+        _LOG.info("The battery refusal ends, control asks for power again: %s.",
+                  why)
+
+    def _refusal_update(self, decision, asked_w, batt_w, probe) -> None:
+        """Follow `compute()`'s carried refused direction, and say so."""
+        now = decision.refused or 0
+        if now and not self.batt_refused:
+            self._refusal_start(now, f"asked {asked_w:+.0f} W, the battery "
+                                     f"gave {batt_w:+.0f} W for "
+                                     f"{decision.sat_count} cycles")
+        elif self.batt_refused and not now:
+            answered = probe and self.batt_refused * batt_w >= _ctl.PROBE_ANSWER_W
+            self._refusal_end("the probe was answered" if answered
+                              else "the grid now asks the other direction")
+
+    def _refusal_from_stale(self, inv, now_mono) -> None:
+        """A stale-reading stop while the loop is frozen on ~0 W is a refusal.
+
+        Only at one inverter: with several, one empty battery must not stop the
+        site (OPT-09's pack limit moves its share to the others).
+        """
+        t = self.tuning
+        standing = inv.standing_w()
+        if (len(self.inverters) == 1 and (self.auto or self.shadow)
+                and not self.batt_refused
+                and self.sat_count >= t.saturation_cycles
+                and inv.batt_fresh.held is not None
+                and abs(inv.batt_fresh.held) < t.saturation_w
+                and abs(standing) > t.saturation_w):
+            self._now_mono = now_mono
+            self._refusal_start(1 if standing > 0 else -1,
+                                f"stale reading {inv.batt_fresh.held:+.0f} W "
+                                f"while asked {standing:+.0f} W")
+
     def log_event(self, msg: str, hint: str | None = None) -> None:
         """`msg` goes on the action log, the add-on's own technical record.
         `hint` is `messages.hint()`'s plain words for the same event, and is
@@ -1840,6 +1913,7 @@ class Controller:
         """
         o = self.o
         now_mono = freshness.monotonic() if now_mono is None else float(now_mono)
+        self._now_mono = now_mono
         if self.p1_enabled:
             # ⚠️ P1 is the only authoritative measurement of what the utility
             # sees (§5.1). When it is stale this is None, which falls into the
@@ -2003,6 +2077,7 @@ class Controller:
         if inv.batt_fresh.stale and not was_stale:
             self.log_event(f"STALE {inv.name}: " + inv.batt_fresh.reason,
                            hint=messages.hint("battery_stuck", unit=inv.name))
+            self._refusal_from_stale(inv, now_mono)
             # ⚠️ SAFETY-57 REWROTE THE LAST SENTENCE OF THIS LINE AND NOTHING
             # ELSE IN IT. The escape clause used to read "It clears itself the
             # moment the register reports a different value", full stop - and
@@ -3340,6 +3415,12 @@ class Controller:
         # loop should be. It is safe because the loop's `prev_w` is
         # `self.target`, which the end of this method re-seeds to what is
         # actually standing on the wire.
+        # SAFETY-52: a refusal learned while control ran does not survive a
+        # stop or a start (shadow mode keeps the loop running when stopped).
+        if bool(self.auto) != self._refusal_auto:
+            self._refusal_auto = bool(self.auto)
+            self._refusal_end("control started" if self.auto
+                              else "control stopped")
         if (self.auto or self.shadow) and self.inputs_ok:
             # ⚠️ prev is the ARBITER's last output, not the loop's own last
             # wish. If something outranked the loop, that is what the hardware
@@ -3357,6 +3438,13 @@ class Controller:
             # stale period as power.
             if self.loop_w is None or self.target != self.loop_w:
                 self.i_w = self.target
+            # SAFETY-52: another writer overrode the loop, so a refusal learned
+            # against the loop's own ask no longer describes the wire. A gap
+            # (`loop_w` None: blind or stopped) keeps it: the stale-reading stop
+            # is what seeds it, and dropping it there restarts the ~70 s cycle.
+            if self.loop_w is not None and self.target != self.loop_w:
+                self._refusal_end("another writer")
+            probe = self._refusal_probe()
             # ⚠️ `actual_w` IS THE SITE SUM AND THAT IS DEV-02's OTHER HALF.
             # The anti-windup test inside compute() is
             # `abs(prev_w - actual_w) > saturation_w`, and `prev_w` is the SITE
@@ -3385,6 +3473,10 @@ class Controller:
                 tuning=self.tuning,
                 sat_count=self.sat_count,
                 i_w=self.i_w,
+                # SAFETY-52 at one inverter only: with several, OPT-09's pack
+                # limit already closes an empty battery's discharge end.
+                refused=self.batt_refused if len(self.inverters) == 1 else None,
+                probe=probe,
             )
             if decision.frozen and self.sat_count < self.tuning.saturation_cycles:
                 self.log_event(f"saturation freeze ({self.target:.0f} W vs "
@@ -3393,6 +3485,7 @@ class Controller:
             self.sat_count = decision.sat_count
             self.i_w = decision.i_w
             self.loop_w = decision.target_w
+            self._refusal_update(decision, loop_prev, site_batt, probe)
             # --- TEL-10 ------------------------------------------------------
             # ⚠️ THE INTEGRATOR HAS NEVER LEFT THIS PROCESS, AND THAT IS WHAT
             # THE CARD IS. `self.i_w` is carried between cycles and published

goodwe_controller/app/messages.py

@@ -802,6 +802,9 @@ WHY_WINNER = {
     # failsafe winner. test_messages.py part 7 finds every one in the code.
     "sign disagreement": "Safety stop, power went the wrong way",
     "unsplit": "The power could not be split, all at 0 W",
+    # SAFETY-52: the loop's two words for a battery that gives nothing.
+    "battery refuses": "The battery refuses to give power",
+    "battery probe": "Testing if the battery gives power again",
 }
 WHY_LIMIT = {
     "peak(quarter peak)": "the peak limit",
@@ -852,6 +855,8 @@ HINTS = {
     "stop_restored": "{unit}: an earlier safety stop is back, it stays at 0 W",
     "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",
+    "battery_gives": "The battery refusal ended, control asks for power again",
     "bad_value": "The add-on made an invalid power value, inverters set to 0 W",
     "write_blocked": "{unit}: a power request was blocked, it is set to 0 W",
     "all_blocked": "A power request was blocked, inverters set to 0 W",