SAFETY-42: a unit that stops delivering, and the discriminator the card asked for does not exist #59

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Claude 090a8ecc35 SAFETY-42 round 2: pin the two thresholds at a config that is not the shipped one
checks / unit (pull_request) Successful in 6m7s
THE BLOCKER. At the `delinquent()` call site, `self.tuning.saturation_w` ->
`250.0` (-19 B) was a survivor of all 23 suites. It is not an equivalent
mutant: two copies of inverter A, B wedged, `saturation_w: 1800` (inside its
own schema int(100,2000)) and a load of 1600 W put B's shortfall strictly
between the literal and the configured value - head names nobody, the mutant
names B. At the shipped 500 both name it, which is exactly why every fixture
in part 4 was blind: their gaps are all above both thresholds.

It matters beyond a mutation score. `delivery.py`'s MIN_W_IS_SATURATION_W note
and the `delivery_hold_s` block in config.yaml both promise an operator, in
shipped prose, that there is no fourth copy of a threshold to keep in step and
no way for the two to drift - raise `saturation_w` and this check moves with
you. A literal at the call site removes exactly that promise, silently, and
the promise is why the design was chosen over a `delivery_w` key.

ASKING THE SAME QUESTION OF EVERY OTHER NUMBER THIS CHECK READS FOUND A SECOND
SURVIVOR OF ALL 23 SUITES: `bms_floor=inv.bms_soc_floor` -> `10.0` (-13 B),
invisible because config.yaml's own example states 10 % and every fixture in
this file used it. Two arms bracket it: a pack at 15 % against its own 25 %
cut-out is cold and must stay unnamed (the literal names an empty pack), and a
pack at 8 % against its own 5 % cut-out is wedged and must be named (the
literal explains the fault away). One arm on each side leaves no constant at
all.

`delivery_hold_s` and `is_live()`'s window were ALREADY pinned - the fixtures
had to move them to run - and `LINK_STALE_S` has no option behind it, so
"pinned across a changed config" is not available for it and is not claimed.
DECISIONS section 9 enumerates all of it with the deltas and which check kills
which.

Verified in the CI image, tree mounted :ro, `python3 -B`, `__pycache__` purged
and counted before every run (TEST-15):
  R5 saturation_w -> 250.0                    -19 B  killed by part 4b(a)
  R6 bms_soc_floor -> 10.0                    -13 B  killed by part 4b(b), both arms
  R7 arm(self.delivery_cfg) -> DeliveryConfig()  -1 B  killed (already)
  R8 is_live(now) -> is_live(now, 3600.0)      +8 B  killed (already)
  R9 pack cut-out -> conjoined site floor    +105 B  killed twice
  head: 23/23 test files PASS, no bytecode written during the run.

No shipped behaviour changes: the only edits to app/ are comments.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BwRLw7eKYj2byVdwB6kbjU
2026-09-06 19:25:45 +02:00
glenn schrooyenandClaude Opus 5 c7eb8c6b97 SAFETY-42: close two mutation gaps, and correct what makes N=1 inert
The battery is 12 mutations, one freshly copied tree each, purged, `:ro`,
`python3 -B`, byte deltas measured. First round: 9 red, 3 survivors. All three
are now accounted for and the ledger is in DECISIONS §8.

M5 - `share <= 0` relaxed to `share == 0`, +0 B - WAS A REAL GAP AND THE TWO
OBVIOUS CHECKS DID NOT CLOSE IT. `short_by(-2000, 0) is None` and
`short_by(-2000, -100) is None` both stayed GREEN under the mutant: for a charge
share that is UNDER-delivered `share - measured` is negative and the `gap > 0`
test answers None anyway, so neither input can separate the two spellings. The
one that can is a unit moving MORE than its charge share - -2000 W told,
-3000 W measured, `share - measured` = +1000 W - which the mutant reports as a
shortfall. It is not one; it is something else driving that pack, which is
SAFETY-30's and SAFETY-31's question. That input is now the check, and M5 is RED.
MUTATION.md's third failure mode in miniature: the assertion ran, the sentence
was true, and the data could not reach the failure it named.

M11 - `inv.is_live(now)[0]` replaced by a literal `True`, -15 B - was a WIRING
gap the pure checks structurally could not see. `account(live=False, ...)` was
graded as a FUNCTION; nothing graded that `cycle()` asks the question, because no
fixture had a unit whose writes were being rejected. Such a unit still has its
last ACCEPTED command standing on the wire (`write_setpoint` leaves `last_write`
alone on a rejected write) and still measures nothing, so it looks exactly like a
wedged one to every number this check reads - and reporting it would be the
second, louder alarm about a state the allocator has already handled and logged.
`test_delivery.py` part 6 now builds that unit, with `rejected_since` back-dated
past LINK_STALE_S because the fixture runs in two seconds and the timer is
test_inverter.py's to grade. M11 is RED.

M3 - `len(asked) < 2` relaxed to `< 1`, +0 B - IS STILL A SURVIVOR, and it is an
EQUIVALENT MUTANT. With one asked unit `unaccounted` is a subset of a one-element
set, so it is either empty (`not unaccounted` returns {}) or equal to `asked`
(`len(unaccounted) == len(asked)` returns {}); with zero asked units both
spellings return {} as well. No input separates them, so no check can.

⚠️ AND FINDING IT CORRECTED THE MODULE'S OWN PROSE, WHICH IS THE MORE USEFUL
HALF. `delinquent()`'s docstring claimed `len(asked) < 2` was what makes N=1
inert. It is not - the PROPER-SUBSET rule is, and that line is a fast path and a
signpost. A false attribution of the mechanism in the file's own prose is exactly
what this repository keeps finding, and a mutation that survives is how it
surfaced. The line stays, with the equivalence written down beside it the way
circulation.circulating_w() records its own max(0.0, ...).

Also recorded, rather than left implicit: `account()`'s `parked` branch is graded
as a function but its WIRING is not mutated on its own; part 6's reversed-unit
fixture exercises it end to end, which is weaker, and the ledger says so.

Baseline 23/23 green before and after. app/main.py is byte-identical to the
previous commit - both closures are a test and a comment.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BwRLw7eKYj2byVdwB6kbjU
2026-09-06 19:25:45 +02:00
glenn schrooyenandClaude Opus 5 706e625d99 SAFETY-42: a unit that stops delivering, and the discriminator the card asked for does not exist
A unit standing at a non-zero share and producing nothing is seen by NOTHING.
SAFETY-30's per-unit sign gate needs OPPOSITION on both sides of 250 W and a
unit at 0 W is not opposing, it is ABSENT. The site sum still agrees with the
meter in direction. Circulating power is exactly zero when one unit does
nothing. The only trace left is `reason == "saturated-freeze"`, which
clamp.py:93-96 documents as the alarm an operator learns to ignore. It is
HW-01's shape, which ran 6 h 25 m with all three layers spectators.

⚠️ THE CARD'S OWN DISCRIMINATOR WAS BUILT FIRST AND FALSIFIED, AND THAT IS THE
MAIN CONTENT. SAFETY-42 asks for "saturation persisting past N while
|grid error| > X, both derived". Run on the two-master rig it fails in BOTH
directions, and no (N, X) fixes either:

  FALSE POSITIVE  `plantsim.Plant.limit()` returns 0 W for a discharge command
      into a pack at its own floor, and a wedged unit produces 0 W too. Load
      2000 W, equal weights, 2000 W per-unit cap, 120 cycles: THE TWO ARMS ARE
      IDENTICAL ON ALL 120 in grid, site target, every share and every measured
      watt. Both saturated-freeze on 116 of them, both hold |grid error| over
      300 W on all 120 and settle at 1200 W, both read circulating 0.0 W. The
      predicate's inputs do not differ, so no threshold on them can differ. And
      "a cold pack at its floor must not alarm" is the card's own AC 2.

  FALSE NEGATIVE  the standing grid error is what a HEALTHY SIBLING ERASES.
      Load 800 W, same config, B wedged: over the last 30 of 200 cycles the loop
      is frozen on 30 of 30 while the worst |grid error| is 30 W, with B standing
      at +770 W and delivering 0 W. Any X above 30 W is silent for the whole run
      on the exact fault the card describes.

WHAT REPLACES IT. Per unit, for a discharge share, `share - measured`; readable
because of a reduction that only exists at N>=2:

    a unit is named while it is short by more than `saturation_w` with NO
    ACCOUNT for it, and the units in that state are a PROPER SUBSET of the units
    asked to discharge.

THE ACCOUNT keeps the cold pack out and is the only thing that can: the two
cases are identical in the power domain, so the discriminator has to be a
non-power fact, and there is exactly one - the pack's own SoC against its own
`bms_soc_floor`, asked through `peakguard.discharge_permitted()` rather than
transcribed. ⚠️ `bms_soc_floor` ALONE, not `pack_floor_pct()`'s conjunction with
`peak_soc_floor`: that floor bounds a money-saving discharge only and using it
would explain away a wedged unit anywhere between the two.

THE PROPER SUBSET keeps a whole-site cause out - a derate this add-on cannot see
hits every unit; one box that stopped listening does not - and it is what makes
this INERT AT N=1, by algebra rather than by a roster guard.

IT REPORTS. IT DOES NOT ACT, and the strongest argument is for acting. Dropping
the wedged unit from `live` genuinely recovers a site the shipped path does not:
at load 1500 W, kept in the split the site settles at 800 W with a 700 W error
and NEVER comes inside 100 W in 150 cycles (the freeze pins the target, so the
sibling's SHARE never grows); dropped, it delivers 1500 W from cycle 14. What
refuses it is that the only re-allocation this add-on can express is
all-or-nothing: a unit derated to 50 % is short by more than saturation_w with
nothing to explain it, so this detector names it too, and at load 3000 W
dropping it leaves the site delivering 2000 W against 2400 W kept - 400 W WORSE.
A partial re-allocation is what would make acting safe and the allocator cannot
express it. That is a card.

control.py is NOT MODIFIED. The freeze shapes the loop; this reports on it.

NUMBERS, MEASURED. The watts side is `Tuning.saturation_w`, read at runtime, so
there is no fourth CFG-03 copy and it cannot drift from the number the control
law itself calls "not following". `delivery_hold_s: 185` comes off 2640
closed-loop two-inverter runs in which nothing is faulty (6 gains x 5 slews over
the whole schema range, across load reversals, a flapping load and ASYMMETRIC
SPLITS - a family SAFETY-30's campaign did not have and the one that dominates
here) plus 1890 runs at a roster of ONE as the control:

    threshold   reversals   flapping   weighted   N=1 control
     * 500 W      20.0 s      0.0 s      30.0 s      0.0 s

The N=1 column is 0.0 s at EVERY threshold in all 1890 runs, and the flapping
column - the family that defeated SAFETY-30's site window - is zero too, because
a common stimulus makes both units short at once and the subset stops being
proper. ⚠️ The curve is NOT monotone (55.0 s at 250 W against 40.0 s at 100 W):
lowering the threshold can turn a proper subset into the whole roster and BREAK
the run.

⚠️ THE MARGIN IS MEASURED, NOT FELT, BECAUSE INVERTER B DOES NOT PHYSICALLY
EXIST. `plantsim.INVERTER_B` is A COPIED, `measured=False`, so every two-inverter
figure above is two copies of A. Sweeping a different second unit: the worst
legitimate episode is insensitive to B's RAMP (30.0 s at half A's) and scales
with its LAG - 45.0 s at twice A's measured 10 s, 90.0 s at four times it.
185 s is 6.2x the measured worst, 2.06x the four-times-slower case, 6.2x
LINK_STALE_S and 4.9x inside the 900 s quarter. Deliberately not 180, which is
SAFETY-02's site hold.

SAFETY-34. `unit/<name>/delivery_tripped` in the store, one notification id per
unit, re-raised on the first cycle of every process, cleared by the Start press.
No flat mirror: a rollback lands on a version that drives one actuator, where
this check is inert.

⚠️ SCHEMA CHANGE - `delivery_hold_s` joins options: and schema:, so this needs a
version bump before it ships. Additive and defaulted, so an existing options blob
stays valid.

STATED GAPS: charge shares are not graded (no configured charge ceiling exists,
so a constant-voltage taper cannot be explained and arming it would fire on every
maintenance charge); every unit wedged at once is not caught (the subset is not
proper and no instrument here separates that from a plant that cannot).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BwRLw7eKYj2byVdwB6kbjU
2026-09-06 19:25:45 +02:00