SAFETY-79: peak guard keeps a margin below the limit

New option peak_margin_w (default 50 W, 0-500 W). The peak guard, the
forecast checks and the maintenance charge sizing aim at
peak_cap_w - peak_margin_w; the month peak, the bill, headroom, warnings
and every notice keep the real cap. Owner decision 2026-09-28.

peak_margin_w 0 is byte-identical to ed739d4 (tools/safety79_identity.py,
test_peak_margin.py part 1). validate.py rule 12 refuses a value outside
0-500, not whole, or not below the peak limit.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UBtqPrG1mDLXzTEBnhEkkV

goodwe_controller/tools/replay_ac3.py

@@ -176,7 +176,7 @@ def replay(paths, *, guarded: bool, cap_w, max_w, max_hold_s, cycle_s,
             next_cycle = t + timedelta(seconds=cycle_s)
             cycles += 1
             d = decide(PeakTracker.project(ing.averager, t), batt_w=batt,
-                       cap_w=cap_w, reading=tracker.peak(t),
+                       cap_w=cap_w, margin_w=0.0, reading=tracker.peak(t),
                        achievable_w=max_w, max_hold_s=max_hold_s, soc=soc,
                        soc_floor=soc_floor, frozen=False)
             if d.engaged:

goodwe_controller/tools/safety79_identity.py

@@ -0,0 +1,114 @@
+#!/usr/bin/env python3
+"""SAFETY-79: with `peak_margin_w: 0`, is every command byte-identical to before?
+
+    python3 tools/safety79_identity.py          # prints one digest per scenario
+
+tools/opt11_identity.py's harness (the REAL Controller, read_inputs + cycle, in
+simulated time) with a P1 meter, so the peak guard runs, and a peak limit the
+house goes over. Each row hashes opt11_identity's fields plus the guard's floor,
+limit and sentence. It uses only the API release/1.0 ed739d4 already had, so
+the same file runs on the old tree (which ignores `peak_margin_w`) and the new.
+test_peak_margin.py part 1 holds the new tree to the digests printed on ed739d4.
+"""
+
+import functools
+import hashlib
+import os
+import sys
+import tempfile
+import time
+from datetime import timedelta
+
+sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
+
+import opt11_identity as rig                               # noqa: E402
+from app import packmode                                  # noqa: E402
+from app.p1 import make_sample, split_signed              # noqa: E402
+from app.store import unit_key                            # noqa: E402
+
+CAP_W = 2500
+
+
+def load(t):
+    """A house under the limit, over it, a solar surplus, far over, over."""
+    if t < 300:
+        return 800.0
+    if t < 900:
+        return 3200.0
+    if t < 1500:
+        return -2600.0
+    if t < 2100:
+        return 6000.0
+    return 4200.0
+
+
+def soc(u, t):
+    return 60.0         # above the peak reserve: the guard may discharge
+
+
+def _feed(c, t):
+    """One P1 telegram per cycle: the meter reads what the house and the
+    batteries' measured power leave."""
+    imp, exp = split_signed(c.hass.grid())
+    c.p1.submit(make_sample("ha_signed", imp, exp, phases=1,
+                            ingest_ts=rig.BASE + timedelta(seconds=t),
+                            ingest_mono=time.monotonic()))
+
+
+def store_off(name):
+    """A store where battery `name` is switched Off (OPT-11)."""
+    s = rig._Store()
+    s.data[unit_key(name, packmode.USE_KEY)] = False
+    return s
+
+
+P1 = {"meter_source": "ha_signed", "p1_net_entity": "sensor.net",
+      "meter_phases": 1, "peak_cap_w": CAP_W}
+MODES = {"battery_modes_enabled": True}
+
+SCENARIOS = {
+    "n1": dict(n=1),
+    "n2": dict(n=2),
+    # OPT-11: the only battery Off, so only the peak guard makes it give.
+    "n1_off": dict(n=1, modes=True, off="inverter-a"),
+    # OPT-11: B Off, so B covers what A cannot.
+    "n2_off": dict(n=2, modes=True, off="inverter-b"),
+}
+
+
+def run(n, *, margin=None, modes=False, off=None, dur=2700.0):
+    """Rows for one scenario; `margin=None` leaves the key out."""
+    extra = dict(P1, **(MODES if modes else {}))
+    if margin is not None:
+        extra["peak_margin_w"] = margin
+    guard = []
+
+    def on_cycle(c, t):
+        g = c.peak_guard
+        guard.append(None if g is None else (g.engaged, g.floor_w, g.ceiling_w,
+                                             g.ceiling_from, g.reason))
+    db = os.path.join(tempfile.mkdtemp(prefix="s79-"), "tariff.db")
+    real = rig.Controller
+    rig.Controller = functools.partial(real, peak_db_path=db)
+    try:
+        rows, c = rig.run(n, extra=extra, dur=dur, load=load, soc=soc,
+                          cut=lambda u, t: False, before=_feed,
+                          on_cycle=on_cycle,
+                          store=store_off(off) if off else None)
+    finally:
+        rig.Controller = real
+    return [r + (g,) for r, g in zip(rows, guard)], c
+
+
+def digest(rows) -> str:
+    return hashlib.sha256(repr(rows).encode()).hexdigest()
+
+
+def digests(margin=None) -> dict:
+    return {k: digest(run(**v, margin=margin)[0]) for k, v in SCENARIOS.items()}
+
+
+if __name__ == "__main__":
+    m = None if len(sys.argv) < 2 else int(sys.argv[1])
+    for k, v in digests(m).items():
+        print(f"{k} {v}")