SAFETY-47: what a shadow run can show, and the watts on its status row

Not a leak and not a write-path defect. Shadow mode's safety is intact -
the substitution, the re-seed, the authorisation gate and the clamp are
untouched. What was wrong is what three merged documents SAY a shadow run
can show you, and a number on the status row that can be 6.61x what a live
controller would command.

SHADOW MODE CANNOT SURFACE A CLOSED-LOOP DEFECT, AND THE DOCUMENTS NOW SAY
SO. The battery is held at 0 W and the carried command is re-seeded to it,
so every measured input - the meter, the billed-quarter accumulator behind
it, the battery power, the SoC - describes a plant that did not respond. A
closed-loop defect is one whose stimulus IS that response. This is the same
property that makes shadow mode safe, so it is not a gap to close later:
the closed-loop answer comes from the closed-loop rig or from a live run.
SAFETY-10 §5 already conceded this for the grid-following loop. It was
never the loop leg's limitation; it is the general case.

THE "STRATEGIES ARE UNAFFECTED" EXEMPTION WAS TRUE UNTIL SAFETY-45 MERGED,
ONE COMMIT EARLIER. That card sizes the buy leg as min(asked, headroom)
with headroom = (900/remaining) x (ceiling - projected), and `projected`
reads the open quarter's accumulator - the meter - which is a function of
what the battery did earlier in that quarter. Measured on TEST-23 stage 3
at peak_cap_w 1500 / house 1200 / max_w 2000, one hour at 5 s:

  SAFETY-45's limit cycle  NOT visible. 28 onsets live vs 1; grid
                           -455.5..+3200.0 W vs flat at the 1200 W house;
                           guard engaged 410/720 cycles vs 0/720.
  SAFETY-46's SoC churn    NOT visible. The SoC moves 0.000000000 pp.
  TARIFF-14's wrong hour   VISIBLE, and it is the only one: which hour, at
                           what price, clearing what spread - identical on
                           720 of 720 charging cycles at a binding cap.

The exemption narrows to exactly what survives: WHICH hour a strategy picks
and WHY are unaffected; HOW HARD it trades is not. The peak guard's ceiling
and reasons are worth reading from a shadow run; its ENGAGEMENTS are not.

THE NUMBER IS CAVEATED, NOT RE-COMPUTED, AND THAT IS THE DECISION. The
arithmetic is not wrong - 900/remaining is correct for a meter genuinely
under the ceiling, and in shadow the meter genuinely is. It is the right
answer to a question nobody asked. Both surfaces now introduce the watts as
what would have been commanded ON THIS CYCLE, in every state, and carry
shadow.SIZED_FROM_METER whenever a measured billed quarter sized them.
Rejected, and recorded in the decision doc: re-computing it (the recorded
decision would no longer be the decision the shipped path reached, while the
arbiter, clamp, SAFETY-28 gate, log and MQTT all ran on the real one - a
second controller everywhere except the wire); recording nothing (blanks the
row exactly when arbitrage is trading, and the log's edge key is the watts);
and recording the unsized ask beside it (a second number, no warning, and at
the shipped 3500/2000 both figures read 2000 W).

"UPPER BOUND" AND NOT "SMALLER", AND THE DIFFERENCE WAS MEASURED. Charging
only adds offtake, so the shadow size is >= the live size with EQUALITY at
the start of every quarter. Pairwise over 3600 charging cycles in five
configurations: 0 below, 730 exactly equal. The first draft said "smaller",
which would have been false on every one of those 730.

AND THE PREDICATE IS NOT KEYED ON WHETHER THE TRADE WAS CAPPED. arbitrage's
own sentence says "SIZED BY THE CAPACITY-TARIFF GUARD" only when the
headroom came out below the ask - in a shadow run, the START of the quarter,
where the two runs agree to the float. By the end, 900/remaining has
multiplied the headroom past the ask, the trade is not capped, the sentence
is silent, and the record is at its most wrong. A caveat keyed on it would
be quietest exactly where it is needed loudest.

SAFETY-10 §6's COMMITTED EVIDENCE COULD NEVER HAVE FAILED, FOR TWO
INDEPENDENT REASONS, AND CLOSING EITHER ALONE CLOSES NOTHING. Its fixture is
peak_cap_w 15000 against a 350 W house, so the guard never engages and the
sizing is inert - the harness's own comment says so. AND every identity row
reads the FIRST charging sample, where at elapsed=0 the projection IS the
held level and the two runs agree to the float even at a cap that does bind.
Measured: widening the fixture alone leaves that comparison passing. That
second reason is a new shape for MUTATION.md's habit-4 list - an INDEX, not
a fixture - and it is recorded there as the twelfth instance. §6 is re-taken
at a binding cap across the whole run: 716 of 720 charging cycles differ,
headroom 300.0..54000.0 W in shadow against 299.9..307.8 W live, recorded
-2000.0 W against a live -302.4 W.

THE GRADER IS test_arbitrage.py PART 3d, beside SAFETY-45's own closed-loop
regression and built on the same s45_loop() harness, so the runs differ in
one argument. Three lines stand in for _write_unit()'s substitution and
_shadow_settle()'s record and re-seed, marked as a transcription;
test_clamp.py part 8 remains the check on the shipped placement. The section
carries its own precondition into every check: a mutation that stopped
either run trading made it raise on its first min(), kill the file and
report ZERO reds - FCST-06's shape, driven rather than imagined.

AND THE FIX'S OWN FIRST DRAFT CARRIED THE SAME DEFECT. Deleting the caveat
from the action-log line left all 29 files green, because the sentence was
an f-string inside _shadow_settle() and the only suite that drives it uses a
meter_source:off fixture where no arbitrage decision exists. It is
shadow.log_line() now, for the reason words() is a function.

14 mutations, no survivors; M13 and M14 are +0 B and were confirmed on disk
by sha256 with every run purged. M14's first form was aimed at the wrong
direction and correctly survived - min->max makes the shadow record larger,
which is still an upper bound. All 29 check files green.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BwRLw7eKYj2byVdwB6kbjU

goodwe_controller/DOCS.md

@@ -650,8 +650,9 @@ decisions recorded while the loop runs.
 
 **What you get out of it.** The status page carries a red-amber banner saying
 the battery is not being controlled, a `Shadow mode` row saying which rung
-decided, what it **would have commanded** and why, and the `Why` row with the
-arbiter's own sentence. The action log gets one line each time the decision
+decided, what it **would have commanded on that cycle** and why — with the
+caveat below, where the number was sized from a meter the battery never
+moved — and the `Why` row with the arbiter's own sentence. The action log gets one line each time the decision
 changes — the winner or the watts — rather than one per cycle, so a 40-row log
 still contains the context of what it found. MQTT reports `status: shadow`.
 
@@ -663,7 +664,12 @@ never saw it, and **latch a trip that survives into live operation and a
 restart**. The clamp (SAFETY-03), the write-authorisation gate (SAFETY-28), the
 frozen-meter alarm (SAFETY-18) and the capacity guard all **observe**: they run
 on the number the decision path produced, so a shadow run can tell you the
-clamp would have engaged. The circulation (SAFETY-31) and delivery (SAFETY-42)
+clamp would have engaged. ⚠️ **The capacity guard observes a meter with no
+battery in it.** Every term of the quantity it thresholds is measured, so it
+engages in a shadow run only if the *house alone* would have put the quarter
+over the ceiling — 410 engaged cycles live against 0 in shadow, on the hour
+tabulated below. Its *ceiling* and its *reasons* are worth reading from a
+shadow run; its *engagements* are not evidence of anything. The circulation (SAFETY-31) and delivery (SAFETY-42)
 watchdogs observe and may legitimately latch, because their evidence is
 *measured* power, not a command. The operator stop is enforced at the wire
 instead of as a claim, so that the recorded decision is the real one.
@@ -678,17 +684,85 @@ every cycle whether control is started or not, so they already run against a
 battery that does not move on a stopped install. Shadow mode inherits that
 exactly; it neither improves it nor makes it worse.
 
-⚠️ **What a shadow run will NOT tell you.** The controller's carried command is
-re-seeded to the 0 W standing on the wire at the end of every shadow cycle —
-that is what makes turning shadow mode off safe, because the loop then resumes
-from where the battery actually is. The consequence is that the
-**grid-following loop's** recorded decision is **one slew step** and stays
-there: a shadow run answers *"what would it command now"*, not *"what
-trajectory would it have followed"*, because the trajectory depends on a
-battery responding and none did. The **strategies** are unaffected — price
-arbitrage, the capacity guard and maintenance all ask for a fixed power from
-inputs that do not depend on what the battery did — so a shadow run does show
-you the trades, the peak-guard engagements and the SoC-limit behaviour.
+⚠️ **What a shadow run will NOT tell you — and it is a whole category, not a
+footnote.** The controller's carried command is re-seeded to the 0 W standing
+on the wire at the end of every shadow cycle — that is what makes turning
+shadow mode off safe, because the loop then resumes from where the battery
+actually is. Everything below follows from the same fact.
+
+**A shadow run cannot show you a closed-loop defect. Not partially — not at
+all.** The battery is held at 0 W, so every *measured* input — the meter, the
+billed-quarter accumulator behind it, the battery power, the state of charge —
+describes a plant that did not respond. A closed-loop defect is one whose
+stimulus **is** the plant's response, and there is no response to be the
+stimulus. This is not a gap waiting to be closed: feeding the guards a
+simulated plant instead is exactly what the sign-watchdog decision below
+refuses, and for the same reason — a controller reacting to a plant that does
+not exist drifts further from reality every tick. **The closed-loop answer
+comes from the closed-loop rig or from a live run, and there is no third
+place.**
+
+Concretely, measured on the rig at `peak_cap_w` 1500 under a 1200 W house,
+`max_w` 2000, one hour at a 5 s cycle — the same hour run twice, live and in
+shadow, on the same code:
+
+| | live | shadow |
+|---|---|---|
+| charge onsets in the hour | **28** | **1** |
+| grid | **−455.5 … +3200.0 W** | **1200.0 W flat — the house** |
+| capacity guard engaged | **410 / 720 cycles** | **0 / 720** |
+| state of charge | 50.000019 → 51.856789 % | **50.000000 → 50.000000 %** |
+
+(The onset and engagement figures are taken with the trade-sizing fix reverted,
+because that is the defect being looked for; the SoC and grid figures are the
+shipped build.)
+
+⚠️ **The "strategies are unaffected" exemption that used to stand here was true
+until the trade-sizing fix landed, and is now false by hours.** That fix makes
+the buy leg `min(asked, headroom)`, where the headroom is
+`(900 / seconds remaining) × (ceiling − projected quarter average)` — and the
+projection reads the **open quarter's accumulator**, i.e. the meter, i.e. a
+function of what the battery did earlier in that same quarter. What survives
+of the exemption is exactly this much:
+
+> **Which** hour a strategy picks, and **why**, are unaffected — the clock and
+> the price series are not functions of the battery. Measured: identical live
+> and shadow on 720 of 720 charging cycles at a binding cap. **How hard** it
+> trades is not.
+
+⚠️ **So the watts on the `Shadow mode` row are the right answer to a question
+nobody asked, and the row now says so.** In a shadow run the billed quarter
+really *is* under its ceiling, because the battery really *is* not charging, so
+`900 / remaining` multiplies a gap a live run would have closed. On the same
+rig, shipped code:
+
+| cap / house | live commanded | shadow recorded | over by |
+|---|---|---|---|
+| 1500 / 1200 | −302.4 W | **−2000.0 W** | **6.61×** |
+| 3500 / 3000 | −502.6 W | −2000.0 W | 3.98× |
+| 3500 / 2000 *(shipped cap)* | −1502.6 W | −2000.0 W | 1.33× |
+| 3500 / 1800 | −1702.6 W | −2000.0 W | 1.17× |
+| 15000 / 350 | −2000.0 W | −2000.0 W | 1.00× |
+
+Whenever a measured billed quarter sized the number, the row and the action log
+carry **⚠️ AND ITS SIZE CAME FROM THE BILLED-QUARTER METER, WHICH HAS ONLY THE
+HOUSE IN IT WHILE THE BATTERY IS HELD AT 0 W** — and the watts are introduced
+as what it would have commanded **on this cycle**, in every state, because no
+number a shadow run records is a forecast of a live one. The figure is **not**
+re-computed to look right: a shadow-only sizing would mean the recorded
+decision was no longer the decision the shipped path reached, which is the one
+thing this feature has to be able to say.
+
+The **grid-following loop** is the same story told first: its recorded decision
+is **one slew step** and stays there, because a trajectory depends on a battery
+responding and none did.
+
+**What a shadow run genuinely is for**, then: *which* strategy wins, on *which*
+hour, at *which* price, for *which* reason, against which limits — the
+wrong-quarter-hour class of defect, a trade armed on a day it should not be, a
+refusal whose sentence names the wrong subsystem, a clamp that would have
+engaged, a standing failsafe latch. That is a real and useful set, and it is
+the set this feature covers.
 
 #### The sign-disagreement failsafe