FCST-04: the carry-forward stops decimating a quarter-hourly feed, and a broken cache stops stopping the add-on

Rework of the FCST-04 branch against review. Every finding below was proven by
a runnable script before it was touched and re-run after; every check added or
repaired was driven red by a mutation, `__pycache__` purged first (MUTATION.md,
TEST-15). 29/29 test files green.

⚠️ H1 - A SUB-HOURLY FEED WAS DECIMATED TO ONE POINT AN HOUR, AND THE SPREAD
WENT WITH IT. `fill_from_yesterday()` keyed the published set as
`{_utc_hour(p.start): p for p in r.points}` - LAST POINT OF THE HOUR WINS, the
other three dropped. `eneco_eddy` is the Belgian imbalance product and settles
per QUARTER, and `_validate_raw()` accepts any strictly-increasing spacing, so
this is a shape the product supports today. Measured on a 96-point quarter-hourly
feed - ALL FIRM, FULLY PUBLISHED, nothing to carry: the plan reached the
optimiser as 15 points, the arbitrage spread fell from 0.143 to 0.014 EUR/kWh,
and the cheapest "hour" became a `:45` point whose `at()` window runs into the
next one. Not the windowing effect this card is about; a feed losing 84 % of its
own prints, with no flag anywhere reporting it. The fill now decides only WHICH
WHOLE HOURS NEED CARRYING: every published point inside the window passes
through BY IDENTITY, and a carried point is added only for a whole hour with no
published coverage at all. Same feed, same fixture: 60 of 60 firm points kept,
spread 0.134 over the hours still ahead.

⚠️ AND `_audit()` GOT STRICTER, NOT LOOSER - that was the condition on doing it
at all. The old post-condition refused any repeated `_utc_hour`, a count that
cannot express four points in one hour. Two rules replace it and SUBSUME it: a
published point must BE one of that hour's published points by identity and may
be emitted only once; a carried point may stand only in an hour absent from the
published set, must be flagged True, and may not repeat. So the duplicated
carried hour it existed to catch still raises, the same published point emitted
twice now raises, and a carried point sharing an hour with a real print now
raises too - which the count never looked at. Three mutations, three reds.

⚠️ H2 - A DAY RECORD THAT WAS NOT A RECORD STOPPED THE ADD-ON FROM STARTING.
`_load()` validated `version` and that `days` is a dict, never that each VALUE
is one. `{"version": 1, "days": {"2026-01-14": "oops"}}` loaded as ok=True,
last_error=None, and then `rec.get(...)` raised AttributeError out of `words`,
`yesterday()` and `resolve_tariff()` alike. `PriceHistory(...)` and `.words` are
both unguarded in `Controller.__init__`, so the controller did not come up - and
it never self-healed, because `_remember()` raised on the same record before it
could reach `_save()`. That falsifies the CHANGELOG's "A BROKEN CACHE IS NOT A
BROKEN CONTROLLER" in the one direction that matters. The asymmetry that
produced it is visible in the file: `_parse_points()` is carefully defensive
about every field of a POINT and `_load()` was not defensive about the record
holding them. Unusable records are now dropped and REPORTED (`words` says how
many and why), and `words` is total by construction as a second line.

M3 - `yesterday()` WAS OFF BY ONE DAY FOR 00:00-00:59 AFTER SPRING-FORWARD.
`brussels()` renders at the FIXED offset for that instant, so `brussels(stamp) -
timedelta(days=1)` subtracts 24 ABSOLUTE hours - and the Brussels day before the
March transition is 23 hours long. At 2026-03-30T00:30+02:00 it returned
2026-03-28's prices as "yesterday", or `no_data` naming a date that is not
yesterday. The arithmetic is now on the local DATE, which has no offset to lose,
and both transitions have a check - the module's headline claim had none.

M4 - WITH NO /data THE STORE STILL FILLED, IN MEMORY. `_save()` short-circuited
on `not ok` while `_remember()` populated `self._days` anyway: `words` said
"unavailable" and `yesterday()` answered A SERIES that is gone on the next
restart. The module docstring rejects exactly that ("a yesterday that silently
forgets") as its reason for not calling makedirs, so the code now matches the
docstring rather than contradicting it.

M5 - THE PRUNE MUTATION SURVIVED BECAUSE THE STIMULUS WAS DEGENERATE. §8's
clock-jump check seeded ONE day, so `if len(self._days) <= KEEP_DAYS: return`
fired and the body it is named after never ran: pruning by arithmetic against
the clock - which empties the store on exactly the morning the fill is for -
passed the whole 29-file suite. The fixture is now written to a file and
reopened (`_load()` does not prune, which is how a store legitimately holds more
than the cap) with KEEP_DAYS + 2 days, and the mutant is red.

M6 - THE AST ORDERING CHECK COULD NOT CATCH A REVERSAL, AND TWO DOCUMENTS CITED
IT AS A GUARANTEE. `_calls.index("_remember") < _calls.index("yesterday")` grades
`ast.walk` BFS DEPTH: `self._remember(...)` is a statement and
`self.yesterday(...)` is an ARGUMENT of the fill, one level deeper, so
`_remember` came out first whichever statement was written first - shipped and
reversed both scored True. It is now line numbers AND, the half that matters,
the behaviour: a feed carrying yesterday alongside today into an EMPTY store
must fill the whole horizon; reversed, the lookup finds nothing and the plan is
only the published hours. Reversing the two statements is red on both.

L14/L9 - KEEP_DAYS = 3 IS THE STEADY STATE EXACTLY, so a newest-N cap has no
slack: a feed publishing to D+2, or ONE stray point in the wrong year - which
sorts LAST and can never age out - pushes yesterday out for good. `_prune()` now
PINS the two days a lookup can actually ask for on top of the cap. Pinning is
additive, so it can only RETAIN and the WITNESS-03 property (nothing is deleted
by clock arithmetic) is preserved by construction; `stamp` stops being a dead
parameter; the store is bounded at KEEP_DAYS + 2.

L8 - the horizon end was not floored while `since` was, so a 48 h request made
at any instant off the hour returned 49 points. §1's count was green only
because its NOW was exactly :00:00, a shape production never has; the fixture
now sits at :17:43. L10 - a failed `_save()` leaked its temp file; at 48 writes
a day a persistent write failure leaked 48 inodes a day onto the volume that was
already the problem. L15 - `{"version": 1.0}` passed, since `1.0 == 1`. L16 -
the `_remember` tree walk scanned `app/*.py` only and matched a bare string; it
now parses `app/`, `tools/`, `scenarios/` and `estop/` and looks for the NAME,
so a comment does not fail it and a call in `tools/` cannot pass unseen.

CLAIM-ACCURACY DEFECTS, WHICH THIS REPO TREATS AS REAL:

* L7. DOCS said "*Tariff* on the status page reads `provisional` through the
  morning". FALSE - `tariff_words` is assigned only from the HA price-entity
  branch and from `static_status()`, both on the 30 s tick, and the plan's own
  sentence reaches `_LOG.info`. The doc now says what an operator can see (the
  Price history row, the Arbitrage row's own refusal sentence, the refresh log
  line) and a check pins the PAIRING - wiring the plan into the row is fine,
  correcting the doc is fine, doing one without the other is red.
* L11. "fills EVERY unpublished hour" is conditional: a partial yesterday leaves
  the local hours it never held out of the series (§11.4 for those hours, and
  `at()` raises rather than answering). Correct behaviour, overclaimed wording,
  and untested - all three fixed.
* L12. DECISIONS §1 leaned on `TariffPlan.cheap_now()`, which has NO PRODUCTION
  CALLER on the provider plan (`self.cheap` comes from `static_status()`, which
  builds its own). The conclusion holds on `arbitrage()`'s firm-pair refusal
  alone, which does reach control; the evidence is now stated at the reach it
  has.
* L13. §1's "passed through by identity" check compared `eur_per_kwh` between
  two SEPARATE `resolve_tariff()` calls, where `is` could never have held. The
  value comparison is kept and now says what it grades; identity is graded on a
  read the file constructs and still holds.
* L17. `PriceHistory.words` and the new status row had no check at all - and
  `words` is one of the two things H2 crashed. Both now have one.
* L18. main.py's inline note carried the "widens what the optimiser can SEE,
  never what it may act on" guarantee without the windowing caveat that the
  CHANGELOG, DOCS and `resolve_tariff()`'s docstring all carry. It is the one
  place a maintainer reads it unqualified.

EVIDENCE. All eight reviewer proofs re-run: p1/p1b return 29 March, p4 keeps
60 of 60 firm points at spread 0.134, p5 starts and reports, p6 D leaves no
temp, p6 E refuses 1.0, p6 F records nothing, p7 returns 48 for 48. p2's script
still scores True/True because it re-implements the OLD algorithm - the
reversal is now driven as a mutation instead, and is red. p3's script always
showed the shipped code correct; what was wrong was the fixture, and its mutant
is now red. Twenty mutations driven, no survivors, tree fingerprinted and
`__pycache__` purged before each: decimation (2 suites red), audit x3, unfloored
`until` (2), unvalidated day records (7 checks), instant-subtraction yesterday,
in-memory fill on a volume-less store, clock-arithmetic prune, cap without the
pin, leaked temp, loose schema type, empty `words` (5), reversed `carry()` (2),
a `_remember` leak in tools/ spelled two ways, a neighbour-filling fallback, a
copy instead of identity (2), the DOCS claim in both directions, and the caveat
removed from main.py. Baseline and the unmutated tree both green.

No option added, config.yaml untouched, and the CHANGELOG entry still picks no
version: PKG-07's rule, and only the deployer knows whether 0.9.0's image has
been pulled.

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

goodwe_controller/CHANGELOG.md

@@ -1,5 +1,105 @@
 # Changelog
 
+## Unreleased
+
+⚠️ **THIS HAS NO VERSION AND CANNOT REACH AN INSTALL UNTIL IT GETS ONE.**
+PKG-06's and PKG-07's rule: the Supervisor keys the built image by `version:`,
+so `ha apps update` is a silent no-op on an unbumped change. This branch
+deliberately does **not** pick the number, because the right one depends on a
+fact the branch cannot observe - whether 0.9.0's image has already been built
+and pulled. If it has not, this belongs inside 0.9.0's section before it ships;
+if it has, it needs 0.10.0. Whoever deploys decides.
+
+| | |
+|---|---|
+| _this branch_ | FCST-04 - the carry-forward fill reaches the plan, and the day it carries survives a restart |
+
+**FCST-03 shipped the fill and no caller.** `price_forecast.fill_from_yesterday()`
+was complete and checked, and so were the consumers written for it -
+`TariffPlan.firm_points()`, `cheap_now()`'s refusal of a provisional hour, and
+`arbitrage()`'s refusal 3, which drops provisional hours from the trade set
+rather than refusing the whole series. Nothing in `app/` called the fill, so no
+series ever contained a carried point and every one of those consumers was
+exercising its all-firm branch.
+
+⚠️ **THE DEFECT THAT PRODUCED WAS NOT AN ERROR ANYWHERE.** `load_prices()`
+returns what the feed published and nothing widened it to the requested horizon,
+so on a dynamic site between midnight and the 14-16 h CET day-ahead publication
+the plan covered the rest of today and **nothing more** - typically 10-24 of the
+48 hours `price_horizon_h` asked for. `arbitrage()` then took `max - min` over
+that truncated window and reported a spread. The number was real, the window was
+half the one configured, and **nothing said so**: tomorrow evening's peak, the
+hour a morning charge would be sold into, was not in the series at all, so the
+spread it would have created was never compared against anything.
+
+**What changes:**
+
+* `app/price_history.py` (new) keeps the **published** prices of the last few
+  Brussels days in `/data/price_history.json`, and `resolve_tariff()` now fills
+  an unpublished hour of the horizon from yesterday's same-wall-clock hour,
+  flagged provisional. ⚠️ **"An" unpublished hour, not "every" one:** the fill
+  can carry only an hour yesterday actually published, so a partial yesterday
+  leaves the local hours it never held **out of the series** - §11.4 for those
+  hours, and asking for one raises rather than answering. Correct behaviour,
+  and the wording is now the behaviour.
+* ⚠️ **A sub-hourly feed keeps every print.** `eneco_eddy` is the imbalance
+  product and settles per **quarter**; the fill walks whole hours to decide
+  what needs carrying, and that is not a rule about what a published hour may
+  contain. Every published point inside the horizon passes through by identity,
+  and a carried point is added only for a whole hour with no published coverage
+  at all. The first draft keyed the published set by hour - last point wins -
+  and a 96-point quarter-hourly feed reached the optimiser as 15 points with
+  its spread down from 0.143 to 0.014 EUR/kWh, on an all-firm, fully-published
+  series.
+* The horizon is **whole hours at both ends**: `since` is floored to the hour
+  that contains it, and so is `until`. Asked for 48 hours at 08:17, the plan is
+  48 hours long and not 49.
+* `resolve_tariff(history=...)` is **required and keyword-only**. A caller with
+  no durable volume passes the explicit `NoHistory()`. A default of `None`
+  meaning "skip the fill" would hand a caller who forgot the argument exactly
+  the truncated horizon this card removes, silently.
+* A new status row, **Price history**, names the days held and their hour
+  counts.
+
+⚠️ **ONE CHANGE HERE MOVES ENERGY, AND IT IS NOT THE ONE THE CARD IS NAMED FOR.**
+Carried hours are provisional, so §8.3 keeps them out of the trade set: the fill
+widens what the optimiser can **see**, never what it may **do**. What does
+change a trade is that the filled series is windowed to `[since, until)`, so
+**hours that have already elapsed are no longer in the spread**. Before, a cheap
+night that had already gone sat in the series as the day's cheapest hour - and a
+cycle cannot buy in an hour that is past, so the trade was quietly never taken.
+`test_price_history.py` section 2 grades this by finding the cheapest firm hour
+with and without the fill and showing it **moves**.
+
+⚠️ **A DEAD FEED IS STILL §11.4, NOT YESTERDAY.** The fill runs only on a
+`series` read; a feed that published nothing still degrades to the configured
+`static_profile`. The two are indistinguishable to the optimiser - both are
+100 % provisional, so arbitrage refuses on the firm-pair rung and `cheap_now()`
+is False - so preferring yesterday would change a documented degradation for a
+difference only the status page can see.
+`DECISIONS/FCST-04-the-day-that-is-carried.md` carries that and two more.
+
+⚠️ **A BROKEN CACHE IS NOT A BROKEN CONTROLLER.** No `/data`, an unreadable
+file, a schema this build does not know (including a `version` of `1.0`, which
+`== 1`), a **day record that is not a record**, a malformed point - each its own
+state with its own reason, none of them a price and none of them an empty
+series. In every one the plan is still a real provider series and the controller
+still regulates; the horizon is just as short as it was before this card.
+`.words` never raises, because `Controller.__init__` reads it unguarded and a
+status line that throws is an add-on that does not start.
+
+⚠️ **AND WHERE THERE IS NO `/data`, NOTHING IS RECORDED AT ALL** - not even in
+memory. An in-memory yesterday answers for one run and is gone on the next
+restart, which is a cache that forgets without saying so; the honest pair is
+`unavailable` on the status row and no prices carried.
+
+⚠️ **"YESTERDAY" IS A LOCAL DATE, AND THE ARITHMETIC IS ON THE DATE.**
+`brussels()` renders at a fixed offset, so subtracting `timedelta(days=1)` from
+it subtracts 24 **absolute** hours - and the Brussels day before a
+spring-forward is 23 hours long. Between 00:00 and 00:59 on the morning after
+the March transition that lands on the day *before* yesterday. **No option was
+added and `config.yaml` is untouched.**
+
 ## 0.9.0
 
 ⚠️ **MINOR FOR NEW FUNCTIONALITY, NOT FOR A BREAK - AND THAT DISTINCTION IS THE

goodwe_controller/DECISIONS/FCST-04-the-day-that-is-carried.md

@@ -0,0 +1,181 @@
+# FCST-04 — what "yesterday" is, and what the fill is allowed to reach
+
+Four decisions, recorded because each had a defensible alternative that a later
+reader would otherwise re-open from scratch.
+
+---
+
+## 1. The fill runs on a `series` read only. A dead feed still goes to §11.4.
+
+`fill_from_yesterday()` accepts a `no_data` read and will happily build a
+100 %-carried series from yesterday alone. `resolve_tariff()` does not let it:
+a feed that published nothing still falls to `_degrade()` and §11.4's own row —
+*"No price data → fall back to the static profile, mark the plan provisional,
+no arbitrage."*
+
+**Why not prefer yesterday's real prices to a coarse day/night profile?**
+Because it buys nothing the optimiser can use, and it silently replaces a
+fallback the operator configured.
+
+Measured, not assumed — and stated at the reach it actually has:
+
+- **This one reaches control.** A fully-carried series is 100 % provisional, so
+  `TariffPlan.arbitrage()` finds fewer than two firm hours and refuses on
+  §8.3's firm-pair rung. That is the verdict the optimiser reads: `arbitrage.py`
+  calls `plan.arbitrage(...)` on `fresh_tariff_plan()`, and it is the only path
+  by which a provider plan moves energy. The §11.4 static fallback refuses on
+  the same rung, for the same reason.
+- **This one does not, and saying so is the point.** `TariffPlan.cheap_now()`
+  also returns False on a fully-carried series, because `firm_points()` is
+  empty — but it has **no production caller on the provider plan**.
+  `self.cheap` comes from `static_status()`, which builds its *own* static plan
+  and calls `cheap_now()` on that. So it is a property of the type, checked in
+  `test_static_tariff.py`, and it is not evidence about the shipped control
+  path. The conclusion below holds on the first bullet alone.
+
+The two paths therefore differ only in which numbers the status page shows.
+
+So the choice is between two identical control behaviours, and the tie-breaker
+is that `static_profile` is a documented option an operator fills in **for this
+case**. Overriding it for a cosmetic difference is a behaviour change nobody
+asked for.
+
+⚠️ **The consequence, stated so it is not discovered later as a bug:**
+`fill_from_yesterday()`'s `no_data` branch is not reached from production.
+It stays checked in `test_price_forecast.py`. Turning it on is a product
+decision — it would want a rule about how old a carried profile may be before it
+stops being offered at all — and not a wiring one.
+
+---
+
+## 2. "Yesterday" is a date, not the newest record.
+
+`newest()` is the obvious accessor and it is the one that decays. An add-on down
+from Friday to Monday would answer Friday's prices to a fill whose only
+vocabulary is `provisional: true` — a flag that says "this is a guess", never
+"this guess is three days old". Nothing downstream can tell the difference and
+nothing reports it.
+
+So `yesterday(stamp)` computes the Brussels date before `stamp`'s Brussels date
+and looks up **that** record. Anything else is `no_data` with a reason naming
+both the date wanted and the dates held.
+
+The cost is real and accepted: after an outage of more than a day, the first
+morning back has no fill. That is the honest state — there is no yesterday —
+and the horizon is short for one morning rather than wrong for several.
+
+---
+
+## 3. What is recorded is the provider's read, and the mechanism is ordering.
+
+Feeding the filled series back into the store is how this rots: day 2 carries
+day 1's guesses, day 3 carries day 2's carry of them, and after a week of a dead
+feed the "yesterday" being carried is a fossil of the last real publication.
+Every point still carries `provisional=True`, so the **flag never lies** — what
+decays is the number, behind a flag that is telling the truth.
+
+⚠️ **No value-level check can catch that**, and claiming one would be worse than
+claiming none. A carried point and a published-provisional point (`eneco_eddy`'s
+current quarter, §9.2) are the same three fields carrying the same flag. The
+difference is provenance, and provenance is not in the value.
+
+The defence is therefore an **ordering**, not a validation:
+
+- `carry()` is the only public entry point. It records its argument, then
+  returns the fill.
+- The filled series exists only as that return value. The object never sees it
+  again.
+- `_remember()` is private and called from exactly one place.
+- `test_price_history.py` parses every shipped module under `app/`, `tools/`,
+  `scenarios/` and `estop/` and fails if any of them **uses the name**
+  `_remember` — an attribute, a bare name, a `def`, or the string constant a
+  `getattr` would need. By name rather than by substring, so a comment that
+  merely mentions the rule does not fail it and a call in `tools/` cannot pass
+  unseen.
+- and it pins the order two ways: the **line numbers** of the two calls in
+  `carry()`, and — the one that matters — the **behaviour**. A feed carrying
+  yesterday alongside today, into an empty store, must fill the whole horizon;
+  reversed, the lookup finds nothing and the plan is only the hours the feed
+  published. Driven, so a reversal is red.
+
+⚠️ **The first version of that ordering check graded nothing, and this file
+said it did.** It compared positions in `ast.walk`, which is breadth-first:
+`self._remember(...)` is a statement and `self.yesterday(...)` is an *argument*
+of `fill_from_yesterday(...)`, one level deeper, so `_remember` came out first
+whichever statement was written first. Measured — shipped and reversed both
+scored the same. A decorative check that a document cites as a guarantee is
+worse than no check, which is why the correction is recorded here rather than
+quietly made.
+
+That ordering has a second benefit worth keeping: a feed that returns yesterday
+alongside today refreshes yesterday's record from live data *before* it is
+consumed as the profile.
+
+---
+
+## What this ticket does not claim
+
+It does not make a trade possible that yesterday's prices justify. Carried hours
+are dropped from the trade set by §8.3, and that is not a limitation to be fixed
+later — it is the rule.
+
+The one change that **does** move energy came from the windowing, not the
+carrying: the filled series covers `[since, until)`, so hours that have already
+elapsed are no longer in the spread. A cheap night that has gone used to be the
+series' cheapest hour, and a cycle cannot buy in an hour that is past — so the
+trade was silently never taken. `test_price_history.py` section 2 grades that by
+finding the cheapest firm hour with and without the fill and showing it moves.
+
+⚠️ **And section 1's identity check now grades identity.** It used to compare
+`eur_per_kwh` between `_before` and `_after`, which come from two *separate*
+`resolve_tariff()` calls — each parsing the feed body into its own objects, so
+`is` could never have held between them however the fill were written. FCST-03's
+whole anti-copy argument is `filled.points[i] is fetched.points[j]`, and floats
+cannot grade it. The value comparison is kept and now says what it is (the fill
+moved the window, it did not touch a price); identity is graded on a read the
+file constructs and still holds a reference to.
+
+---
+
+## 4. A sub-hourly feed passes through whole; the fill only decides which hours are missing.
+
+`eneco_eddy` is the Belgian imbalance product and settles **per quarter**, and
+`price.py`'s `_validate_raw()` accepts any strictly-increasing spacing — so a
+published hour may legitimately hold four points.
+
+FCST-04's first caller keyed the published set as `{_utc_hour(p.start): p for p
+in r.points}`. It reads perfectly ordinary and it keeps the **last** point of
+each hour. Measured on a 96-point quarter-hourly feed — all firm, fully
+published, nothing to carry: the plan reached the optimiser as **15 points**,
+the arbitrage spread fell from **0.143 to 0.014 EUR/kWh**, and the cheapest
+"hour" became a `:45` point whose `at()` window runs into the next hour. That is
+not the windowing effect above; it is a feed losing 84 % of its own prints, and
+no `provisional` flag would ever have reported it.
+
+**The alternative was rejected:** refusing sub-hourly feeds at `_validate_raw()`
+would have made the count correct by breaking the one supported product that
+legitimately publishes per quarter.
+
+**What was done instead** keeps FCST-03's existing contract rather than weakening
+it: *every* published point inside the window passes through **by identity**,
+and a carried point is added only for a whole hour with **no** published
+coverage at all. A carried hour is still a single hourly point whatever the
+feed's own spacing is, because yesterday's profile is only known per wall-clock
+hour — and carried hours are provisional, so they are out of the trade set
+anyway.
+
+⚠️ **`_audit()` got stricter, not looser, and that was the condition on doing
+this at all.** The old post-condition refused any repeated `_utc_hour` — a count
+that cannot express four points in one hour. It is replaced by two rules that
+**subsume** it:
+
+- a **published** point must *be* one of that hour's published points, by
+  identity, and may be emitted only once;
+- a **carried** point may stand only in an hour that does not appear in the
+  published set at all, must be flagged `True`, and may not repeat.
+
+So a duplicated carried hour — the DST mispricing the count existed to catch —
+still raises; so does the same published point emitted twice; and a carried
+point sharing an hour with a real print now raises too, which the count never
+looked at. Each of those three is driven by its own mutation in
+`test_price_forecast.py`.

goodwe_controller/DOCS.md

@@ -1424,6 +1424,70 @@ distinct state from "prices, all of them zero": the plan is marked provisional
 and arbitrage is disabled, per the degradation matrix. It never falls back to a
 price of zero, which would read as free electricity.
 
+#### The hours the feed has not published yet (FCST-04)
+
+A day-ahead auction publishes tomorrow's prices once a day, at **14–16 h CET**.
+Before that, the feed is serving today and nothing else — so a `price_horizon_h`
+of 48 asks for 48 hours and gets back the ten or fifteen that are left in the
+day. Until FCST-04 those other hours were simply **absent** from the plan: not
+priced badly, not flagged, just missing, and nothing said so.
+
+Now the add-on keeps the **published prices of the last few days** in
+`/data/price_history.json` and fills an unpublished hour of the horizon with
+yesterday's price for the same Brussels wall-clock hour, flagged
+`provisional: true`. Two things follow, and the second one matters more:
+
+- **The plan says it is guessing** — `provisional: true` on every carried hour,
+  which is what the optimiser reads. Before, a half-length plan looked
+  completely settled.
+- **Nothing may trade on a carried hour.** §8.3 forbids acting on a provisional
+  price, so arbitrage drops those hours from the trade set entirely — it needs a
+  buy hour and a sell hour that were *both* published. Carrying a price forward
+  widens what the optimiser can **see**; it never widens what it may **do**.
+
+**"An unpublished hour", not "every unpublished hour"** — the fill can only
+carry an hour yesterday actually published. If yesterday's record is itself
+partial (a first day, an outage, a feed that only ever serves the rest of the
+day), the local hours it never held are **left out of the series**: §11.4
+applies to those hours, and asking the plan for one raises rather than
+answering. An hour with no price is not a free hour, and the fill does not
+invent a neighbour, a mean or a zero for it.
+
+**A quarter-hourly feed keeps all four of its prints.** `eneco_eddy` settles
+per quarter, and the fill decides *which whole hours need carrying* — never what
+a published hour may contain. Every point the provider published inside the
+horizon is passed through untouched; a carried point is added only for a whole
+hour the feed did not print at all.
+
+**What you can actually see on the status page.** *Price history* (below) says
+what is held. *Arbitrage* carries the strategy's own sentence, which names the
+firm/provisional split whenever that split is what refused a trade. *Tariff*
+does **not** report the fill: it is the static-profile or Home Assistant
+price-entity sentence, regenerated on the 30 s tick. The provider plan's own
+line — `dynamic_dayahead from generic_dayahead, 48 h, provisional` — goes to the
+**add-on log** at every refresh, alongside `§8.3: 33 of 48 hours carried forward
+from yesterday's profile and flagged provisional; 15 published`.
+
+The plan is also now cut to the horizon you asked for, which means **hours that
+have already elapsed are no longer in it**. That is a real change to arbitrage:
+a cheap night that has already gone used to sit in the series as the cheapest
+hour of the day, and a cycle can never buy in an hour that is past — so the
+trade was quietly never taken. The spread is now taken over hours still ahead.
+
+A new status row, **Price history**, says which days are held and how many hours
+each has. If it reads `empty` or `unavailable`, nothing is carried, the horizon
+is as short as the feed makes it, and every other guarantee is unchanged — a
+cache that cannot answer is not allowed to be a controller that cannot regulate.
+The store is rebuilt by the next successful fetch; on a brand-new install the
+first fill is possible the day after the first refresh.
+
+The same applies to a file that is *partly* broken: a day record this build
+cannot read is dropped, the row says how many were dropped and why, and the rest
+of the file still loads. And where there is no `/data` at all the store records
+**nothing** — not even in memory. An in-memory yesterday would answer for one
+run and vanish on the next restart, which is a cache that forgets without saying
+so; `unavailable` and *no prices carried* are the honest pair.
+
 **Injection is priced separately** (`export_price_eur_kwh`). In Belgium it is
 often near zero, which by itself strongly favours self-consumption over export.
 It is a single number rather than a curve because no supported supplier

goodwe_controller/app/main.py

@@ -68,6 +68,7 @@ from . import peakguard
 from . import packshare
 from .p1 import P1Ingest, build_source, is_enabled
 from .price import Uncertainty, price_option
+from .price_history import PriceHistory
 from .static_tariff import resolve_tariff, static_status
 from .tariff import PeakStore, PeakTracker
 from .store import migrate_maint_keys, migrate_unit_keys
@@ -165,7 +166,8 @@ def pack_energy_of(inv):
 
 class Controller:
     def __init__(self, opts: dict, hass: HomeAssistant, store, mqtt_pub, *, stop,
-                 peak_db_path: str = "/data/tariff.db"):
+                 peak_db_path: str = "/data/tariff.db",
+                 price_history_path: str = "/data/price_history.json"):
         self.o = opts
         self.hass = hass
         self.store = store
@@ -247,7 +249,40 @@ class Controller:
             hold_s=float(opts.get("delivery_hold_s",
                                   DELIVERY_OPTION_DEFAULTS["delivery_hold_s"])),
         )
-        self.store_migration = migrate_unit_keys(store, UNIT_A)
+        # SAFETY-44. THE NAMES THE MACHINES READ, HANDED TO THE MIGRATION THAT
+        # WRITES FOR THEM. This line used to read `migrate_unit_keys(store,
+        # UNIT_A)`, and the constant was wrong in exactly the way the
+        # `maint_migration` call below says the SAME constant would be wrong -
+        # ⚠️ this comment used to cite "line 315" and "two hundred lines
+        # below", and both were wrong. The correction I wrote for them was
+        # wrong too: it said "~54 lines down", which was review's distance to
+        # the WRONG line, carried to a new referent without re-measuring -
+        # inside the sentence apologising for a wrong number. There is no
+        # distance here now, because a distance is a coordinate and the
+        # sentence above already names the thing. On a declared roster the flat
+        # latch landed under
+        # `unit/inverter-a/`, which is on no roster, was read back under the
+        # name it was handed, and stamped the marker. `roster_names()` is the
+        # naming rule itself and returns `[UNIT_A]` on the flat shape, so the
+        # upgrade path every install runs today is byte-identical.
+        #
+        # ⚠️ AND `misdirected` IS UNREACHABLE FROM **THIS** CALL SITE, WHICH THE
+        # COMMIT MESSAGE ORIGINALLY CLAIMED AS A BENEFIT. `unit` is
+        # `roster_names(opts)[0]` and `build_roster()` names its entries from
+        # the same `roster_names()` list, so `unit` is a member of `roster` by
+        # construction and the refusal can never fire here. Review measured it:
+        # dropping the `roster` argument from the `_verify_moves()` call inside
+        # `migrate_unit_keys()` survives 28/28.
+        #
+        # THE ARGUMENT STAYS ANYWAY, and the reason is the one `_verify_moves()`
+        # already gives for keeping its own `roster=None` branch: it is what a
+        # NEW caller gets, and the grading it enables is measured at the
+        # function's own level in test_maintenance.py rather than through here.
+        # What is NOT true is that this call site buys the refusal, so that
+        # claim is gone rather than restated.
+        _roster_names = roster_names(opts)
+        self.store_migration = migrate_unit_keys(
+            store, _roster_names[0], _roster_names)
         self.inverters = build_roster(opts, store, sign_cfg, delivery_cfg)
         # ⚠️ CFG-04. SAY WHICH SHAPE IS IN FORCE, BECAUSE THE OTHER ONE'S KEYS
         # ARE STILL SITTING IN THE UI. A declared `inverters:` roster reads none
@@ -549,6 +584,42 @@ class Controller:
         self.peak.restore(self.p1.averager)
         _LOG.info("capacity-tariff peak store: %s", self.peak.restore_state)
 
+        # FCST-04. The §8.3 carry-forward store: the published prices of the
+        # last few Brussels days, so the hours a day-ahead feed has not printed
+        # yet can be filled from yesterday's profile and FLAGGED, instead of
+        # being absent from the series entirely.
+        #
+        # ⚠️ IT IS AN INSTRUMENT'S BACKING FILE, NOT A STRATEGY. It commands
+        # nothing and claims nothing; what it changes is how many hours the
+        # plan covers. Before this, a dynamic site between midnight and the
+        # 14-16 h CET publication had a series covering only the rest of today
+        # - typically 10-24 of the 48 hours `price_horizon_h` asked for - and
+        # `TariffPlan.arbitrage()` took its spread over that truncated window
+        # without anything reporting that it had. Every carried hour is
+        # provisional, so refusal 3 drops it from the trade set: CARRYING a
+        # price widens what the optimiser can SEE, never what it may act on.
+        #
+        # ⚠️ AND THE CAVEAT THAT BELONGS WITH THAT SENTENCE, because this is
+        # the one place a maintainer reads it on its own. THE OTHER HALF OF
+        # THIS CHANGE DOES MOVE ENERGY, and it is the windowing rather than the
+        # carrying: the filled series covers `[since, until)`, so hours that
+        # have ALREADY ELAPSED are no longer in the spread. A cheap night that
+        # has gone used to sit in the series as the day's cheapest hour, and no
+        # cycle can buy in an hour that is past - so the trade was quietly
+        # never taken. `resolve_tariff()`'s docstring, DOCS.md and the CHANGELOG
+        # all carry this beside the guarantee; it may not appear here without it.
+        #
+        # ⚠️ A BROKEN OR ABSENT STORE IS NOT AN ERROR HERE. It answers `no_data`,
+        # the fill carries nothing, and the plan is the pre-FCST-04 one minus
+        # the elapsed hours - short, but honest and still refusing on the same
+        # rules. It must not be an error in the other sense either: a day
+        # record this build cannot read is DROPPED by `PriceHistory._load()`
+        # and reported in `.words`, because both the constructor above and the
+        # `.words` read below are unguarded, and a cache that raises here is an
+        # add-on that does not start.
+        self.price_history = PriceHistory(price_history_path)
+        _LOG.info("§8.3 price history: %s", self.price_history.words)
+
         # SAFETY-07. The guard TARIFF-01 was built for. It is stateless by
         # design (peakguard.py holds no history between calls), so the only
         # state here is what an EDGE needs: what the last cycle concluded, so
@@ -751,23 +822,132 @@ class Controller:
         legacy_tripped = bool(data.get("sign_tripped", False))
         if not legacy_tripped or not self.inverters:
             return
-        # ⚠️ THE QUESTION IS "IS ANY NAMESPACED LATCH SET", AND IT IS ASKED OF
+        # ⚠️ THE QUESTION IS "IS ANY NAMESPACED LATCH SET **THAT A MACHINE
-        # THE STORE RATHER THAN OF THE ROSTER. At a roster of two a trip on B
+        # READS**", AND THE LAST CLAUSE IS SAFETY-44's SECOND HALF. At a roster
-        # leaves A untripped, so re-arming A off a flat key that B's own trip
+        # of two a trip on B leaves A untripped, so re-arming A off a flat key
-        # mirrored would latch a healthy inverter on every restart - the
+        # that B's own trip mirrored would latch a healthy inverter on every
-        # flat-key defect this card removed, coming back through its own guard.
+        # restart - the flat-key defect DEV-02 removed, coming back through its
-        # And the STORE is the right place to ask: it holds every
+        # own guard. That much stands, and it is why the question is asked of
-        # `unit/*/sign_tripped` this install has ever written, including one
+        # the STORE's keys rather than of the roster's objects.
-        # belonging to a unit that is not in TODAY's roster (a roster is
+        #
-        # configuration and it changes), whereas the roster only knows what is
+        # ⚠️ BUT IT USED TO ACCEPT **ANY** `unit/*/sign_tripped`, and the
-        # configured right now. The flat key carries new information only when
+        # paragraph here defended that: the store "holds every one this install
-        # nothing namespaced is latched at all.
+        # has ever written, including one belonging to a unit that is not in
-        namespaced_latched = any(
+        # TODAY's roster ... whereas the roster only knows what is configured
-            bool(v) for k, v in data.items()
+        # right now". THE PREMISE IS TRUE AND IT ARGUES THE WRONG WAY. A latch
-            if k.startswith("unit/") and k.endswith("/sign_tripped"))
+        # under a name no unit answers to is not protection an operator has - it
-        if namespaced_latched or any(inv.sign_wd.tripped
+        # is a key nothing reads, which is the definition of the state this
-                                     for inv in self.inverters):
+        # method exists to repair. Counting it as protection made the guard
+        # return early on precisely the install that needed it, and that is not
+        # hypothetical: it is where the migration above USED to put the latch
+        # on every declared roster, so the guard was blinded by its own upgrade.
+        #
+        # THE MIGRATION FIX DOES NOT REACH THOSE INSTALLS. A store stamped by
+        # the shipped version already has the marker, so `migrate_unit_keys()`
+        # returns at the version check and never runs again. This guard is the
+        # ONLY repair path for a site that upgraded before this card, and it
+        # re-arms onto `inverters[0]` - which lands the latch back under a name
+        # the roster reads.
+        # ⚠️ AND "OFF THE ROSTER" IS NOT ENOUGH ON ITS OWN - IT HAS TO BE THE
+        # MIGRATION'S OWN FINGERPRINT, WHICH IS `UNIT_A`. The first draft of
+        # this treated EVERY off-roster latch as litter, and test_inverter.py's
+        # DEV-02 restart case caught it: there the store carries
+        # `unit/inverter-b/sign_tripped = True` from B's own trip while the
+        # roster being graded holds only A, and the blunt rule re-armed a
+        # HEALTHY A off the flat key that B's trip had mirrored - DEV-02's
+        # defect rebuilt inside its own guard, which is exactly what the
+        # paragraph above was right to be afraid of.
+        #
+        # `UNIT_A` is the discriminator because it is the ONLY name the broken
+        # migration ever wrote. `roster_names()` falls back to a POSITIONAL
+        # `inverter-N`, so `inverter-a` is not a name this code hands to anyone
+        # else. A latch stranded under any OTHER name is a real unit that is
+        # out of today's config - a roster is configuration and it changes -
+        # and it still counts as protection.
+        #
+        # ⚠️ THE RESIDUAL, STATED RATHER THAN LEFT TO BE FOUND: a site whose
+        # own first unit is NAMED `inverter-a`, latched, and then taken out of
+        # the roster gets re-armed on `inverters[0]`. That is a healthy unit
+        # held at 0 W until an operator clears it, which is the conservative
+        # direction; SAFETY-44's is a site DRIVING on a state file that says it
+        # is latched.
+        #
+        # ⚠️ AND THE SECOND HALF OF THAT RESIDUAL IS THE **SENTENCE**, NOT THE
+        # BOOLEAN. The reason re-armed from is the FLAT mirror, which carries
+        # whatever tripped LAST - so on a multi-unit site this path can print
+        # one inverter's evidence under another inverter's name. The latch is
+        # right and the explanation may not be. It is disclosed here because the
+        # banner is what an operator acts on, and `test_maintenance.py`'s check
+        # that the reason is not the removed unit's is guaranteed by that
+        # fixture's choice of flat string, NOT by this code.
+        # ⚠️ AND THE THREE CASES ARE THREE VARIABLES, NOT ONE SHARED FLAG.
+        # THIS IS WHERE THE FIRST VERSION OF THIS FIX WAS DEFEATED, BY ONE KEY.
+        # It wrote `namespaced_latched = True` for BOTH "on the roster" and "off
+        # the roster but not UNIT_A", so a single latched key belonging to a
+        # unit the operator had removed from `inverters:` vetoed the repair of
+        # the misdirected `inverter-a` latch sitting beside it. Measured on the
+        # shipped build, roster ['garage', 'shed'], store stamped so the
+        # migration cannot reach it:
+        #
+        #   sign_tripped + unit/inverter-a/sign_tripped
+        #       -> [('garage', True), ('shed', False)]   repaired
+        #   ...AND unit/old-shed/sign_tripped
+        #       -> [('garage', False), ('shed', False)]  ⚠️ DRIVING
+        #
+        # A site DRIVING on a state file that reads `sign_tripped: true`, which
+        # is the sentence this whole card exists to make false - and
+        # `tools/rehearse_roster.py` said so, on the unmodified tree, exit 1.
+        #
+        # ⚠️ IT IS ALSO INSTANCE #17 OF HABIT 4, IN THE EXTENSION MUTATION.md
+        # ADDED TWO DAYS AGO. The two fixtures written for this card each hold
+        # ONE arrangement - `_staged_store` has only `inverter-a`, `_other_store`
+        # has only `inverter-b` - and the flag is written twice with opposite
+        # intents only when BOTH are present. A per-key check whose keys have
+        # never disagreed WITHIN ONE STORE is a check over whichever key came
+        # last. The fixture below now holds both.
+        #
+        # THE THREE CASES, AND WHY THE ANSWER DIFFERS FOR EACH:
+        #   on the roster            a machine reads it: real protection, stop.
+        #   off-roster, `UNIT_A`     the broken migration's fingerprint - this
+        #                            IS the flat latch, misdirected. Repair.
+        #   off-roster, other name   a real unit out of today's config. Its
+        #                            latch is unread too, but it is NOT the flat
+        #                            key's misdirection, and re-arming a healthy
+        #                            sibling off it is DEV-02's defect. Stop -
+        #                            UNLESS a stranded `UNIT_A` latch is also
+        #                            present, because then the flat key IS
+        #                            accounted for and the repair is the point.
+        on_roster = {inv.name for inv in self.inverters}
+        stranded, on_roster_latched, other_off_roster = [], False, False
+        for k, v in data.items():
+            if not (k.startswith("unit/") and k.endswith("/sign_tripped")):
+                continue
+            if not bool(v):
+                continue
+            # `unit_key()` builds `unit/<unit>/<key>`, so the unit is field 1 -
+            # split through the writer's own spelling rather than re-deriving.
+            unit = k.split("/")[1]
+            if unit in on_roster:
+                on_roster_latched = True
+            elif unit == UNIT_A:
+                stranded.append(k)
+            else:
+                other_off_roster = True
+        if on_roster_latched or any(inv.sign_wd.tripped
+                                    for inv in self.inverters):
             return
+        if other_off_roster and not stranded:
+            # A removed unit's own latch, and no misdirected one. The flat key
+            # is that unit's mirror, so it carries no new information and
+            # re-arming `inverters[0]` from it would latch a healthy pack.
+            return
+        if stranded:
+            _LOG.error(
+                "SAFETY-44: this store carries a LATCHED sign-disagreement "
+                "failsafe under %s, and that unit is NOT on today's roster "
+                "%s - so no machine reads it and the site came up DRIVING on "
+                "a state file that says it is latched. Re-arming below.",
+                ", ".join(sorted(stranded)), sorted(on_roster))
         first = self.inverters[0]
         # The one state this method exists for.
         reason = str(data.get("sign_reason", "") or "")
@@ -3313,7 +3493,8 @@ class Controller:
             now = datetime.now(timezone.utc)
             try:
                 plan = await resolve_tariff(
-                    self.o, now, now + timedelta(hours=horizon), now=now)
+                    self.o, now, now + timedelta(hours=horizon), now=now,
+                    history=self.price_history)
                 self.tariff_plan, self.tariff_at = plan, now
                 _LOG.info("tariff refreshed: %s", plan.words)
             except Exception as err:                          # noqa: BLE001
@@ -4162,6 +4343,13 @@ class Controller:
             ("Maintenance due", "now" if next_due is None else next_due.strftime("%Y-%m-%d")),
             ("Cheap window", "yes" if self.cheap else "no"),
             ("Tariff", self.tariff_words),
+            # FCST-04. WHAT §8.3 HAS TO CARRY FORWARD, which is the difference
+            # between a 48-hour plan and a 12-hour one on a weekday morning.
+            # It is its own row rather than a clause of "Tariff" because it
+            # answers a different question: "Tariff" says what the plan IS, and
+            # this says what the plan could still be filled from if the feed is
+            # late again tomorrow.
+            ("Price history", self.price_history.words),
             # OPT-04. The strategy's own sentence, not a re-derivation of it -
             # every refusal it can make already carries a reason a human can
             # act on, and "Arbitrage: no" would throw all of them away.

goodwe_controller/app/price_forecast.py

@@ -48,7 +48,8 @@ So the flag is not passed through anywhere in this file:
     the object the provider produced is the object in the output series - so
     there is no copy that could lose or gain a flag. `filled.points[i] is
     fetched.points[j]` is a checkable property, and test_price_forecast.py
-    checks it.
+    checks it. EVERY published point in the window is passed through, not one
+    per hour: see the sub-hourly note below.
   * `_audit()` RE-DERIVES the expected flag for every output point from the set
     of hours the feed actually published, and RAISES if any point disagrees.
     It is a post-condition, not a filter: it never fixes a flag, because a
@@ -90,6 +91,24 @@ which is the row the spec actually writes for "no price data". If NOTHING can
 be produced, the result is `PriceRead.no_data(reason)` and not an empty series,
 because an empty series is not constructible on purpose (price.py trap 3).
 
+⚠️ A SUB-HOURLY FEED IS NOT DECIMATED TO ONE POINT AN HOUR, and the hourly walk
+below is about WHICH HOURS NEED FILLING - never about what a published hour is
+allowed to contain. `eneco_eddy` is the Belgian imbalance product and settles
+per QUARTER, `_validate_raw()` accepts any strictly-increasing spacing, and a
+published hour may therefore hold four points. So EVERY published point inside
+the window is passed through, in order, and a carried point is added only for a
+whole hour with NO published coverage at all.
+
+The alternative was measured rather than reasoned about, because FCST-04's
+first caller shipped it: keying the published set as `{_utc_hour(p.start): p
+for p in r.points}` reads perfectly ordinary and keeps the LAST point of each
+hour, dropping the other three. On a 96-point quarter-hourly feed - all firm,
+fully published, nothing to carry - the series came out 15 points long, the
+arbitrage spread collapsed from 0.143 to 0.014 EUR/kWh, and the cheapest
+"hour" became a `:45` point whose `at()` window runs into the next hour. A feed
+losing 84 % of its own prints is not a windowing effect and is not something a
+provisional flag would ever have reported.
+
 
 AC2: THE IRREVERSIBLE-ACTION GATE
 =================================
@@ -156,6 +175,25 @@ def _utc_hour(instant: datetime) -> datetime:
     return u.replace(minute=0, second=0, microsecond=0)
 
 
+def _published_by_hour(read: PriceRead) -> dict:
+    """UTC hour -> the provider's OWN points that start inside it, in order.
+
+    ⚠️ A TUPLE PER HOUR, NOT A POINT, AND THAT IS THE WHOLE OF THE SUB-HOURLY
+    RULE. `{_utc_hour(p.start): p for p in r.points}` reads identically, is one
+    character shorter, and silently keeps one point per hour - the last one
+    written. The mapping answers two DIFFERENT questions here: "does this hour
+    need filling at all?" is `u in published`, and "what does the output carry
+    for it?" is all of `published[u]`. Collapsing them is how a quarter-hourly
+    feed loses three quarters of its prints.
+    """
+    out: dict = {}
+    read.match(
+        series=lambda r: [out.setdefault(_utc_hour(p.start), []).append(p)
+                          for p in r.points],
+        no_data=lambda _r: [])
+    return {u: tuple(ps) for u, ps in out.items()}
+
+
 def _carried(start_utc: datetime, eur_per_kwh: float) -> PricePoint:
     """A point filled from yesterday's profile. §8.3: ALWAYS provisional.
 
@@ -172,37 +210,69 @@ def _carried(start_utc: datetime, eur_per_kwh: float) -> PricePoint:
 def _audit(points, published) -> None:
     """Post-condition: every flag matches the point's TRUE provenance (AC1).
 
-    `published` maps a UTC hour to the point the provider produced for it.
+    `published` maps a UTC hour to the TUPLE of points the provider produced
+    for it (`_published_by_hour()`). An hour ABSENT from that mapping is an hour
+    the feed did not print, and a carried point is the only thing that may
+    stand in it.
+
+    The rule, in the two forms an output point can take:
+
+      * PUBLISHED - the point must BE one of `published[u]`, by identity, and
+        may be emitted only once. Its flag is whatever the feed said, never
+        forced to False: an imbalance print is published AND provisional (§9.2,
+        TARIFF-02), and a check that "corrected" it would be a bug wearing a
+        guarantee.
+      * CARRIED - the hour must not appear in `published` AT ALL, the flag must
+        be exactly True, and that hour may hold no second point.
+
+    ⚠️ WHAT REPLACED "AT MOST ONE POINT PER HOUR", AND WHY IT IS STRICTER. This
+    audit began as a `seen` set: any repeated `_utc_hour` raised, because a
+    duplicated hour is how a DST day gets mispriced. A bare hour count cannot
+    express a quarter-hourly feed, where four distinct published points share
+    one hour legitimately - so the count was replaced by the two rules above,
+    which subsume it. A repeated CARRIED hour still raises; so does the same
+    published point emitted twice; and a carried point may no longer share an
+    hour with a published one, which the count never checked at all.
 
     ⚠️ RAISES, NEVER REPAIRS. A module that silently corrects its own
     provenance is one whose provenance means nothing; the only safe response to
     "this point's flag disagrees with where it came from" is to refuse to emit
     the series at all.
     """
-    seen = set()
+    carried_hours = set()
+    emitted = set()
     for p in points:
         u = _utc_hour(p.start)
-        if u in seen:
-            raise ValueError(f"the filled series repeats {u.isoformat()}; a "
-                             f"duplicated hour is how a DST day gets mispriced")
-        seen.add(u)
         src = published.get(u)
-        prov = Provenance.CARRIED if src is None else Provenance.PUBLISHED
         if src is None:
+            if u in carried_hours:
+                raise ValueError(
+                    f"the filled series repeats the carried hour "
+                    f"{u.isoformat()}; a duplicated hour is how a DST day gets "
+                    f"mispriced")
+            carried_hours.add(u)
             if p.provisional is not True:
                 raise ValueError(
-                    f"{u.isoformat()} is {prov.value} and is flagged "
+                    f"{u.isoformat()} is {Provenance.CARRIED.value} and is "
-                    f"provisional={p.provisional!r}. §8.3: an hour filled from "
+                    f"flagged provisional={p.provisional!r}. §8.3: an hour "
-                    f"yesterday's profile is provisional whether or not the "
+                    f"filled from yesterday's profile is provisional whether "
-                    f"number turns out to be right - the flag is a claim about "
+                    f"or not the number turns out to be right - the flag is a "
-                    f"PROVENANCE, not about accuracy.")
+                    f"claim about PROVENANCE, not about accuracy.")
         else:
-            if p is not src:
+            if not any(p is q for q in src):
                 raise ValueError(
-                    f"{u.isoformat()} is {prov.value} but the series carries a "
+                    f"{u.isoformat()} is {Provenance.PUBLISHED.value} but the "
-                    f"COPY of that point rather than the point itself. A copy "
+                    f"series carries a COPY of that point rather than the "
-                    f"is where the provisional flag gets lost; published points "
+                    f"point itself. A copy is where the provisional flag gets "
-                    f"pass through by identity.")
+                    f"lost; published points pass through by identity.")
+            if id(p) in emitted:
+                raise ValueError(
+                    f"the filled series emits the published point at "
+                    f"{p.start.isoformat()} TWICE. The provider's own points "
+                    f"are strictly increasing (`_validate_raw`), so a repeat "
+                    f"is never a second print - it is a duplicated hour, which "
+                    f"is how a DST day gets mispriced")
+            emitted.add(id(p))
 
 
 def fill_from_yesterday(read: PriceRead, *, yesterday: PriceRead,
@@ -217,11 +287,21 @@ def fill_from_yesterday(read: PriceRead, *, yesterday: PriceRead,
 
     Returns a `PriceRead`:
 
-      * a series, whose points are the provider's own objects for the hours it
+      * a series, carrying the provider's own objects - ALL of them, which on
-        published and `_carried()` points for the rest, ordered by instant;
+        a quarter-hourly feed is four inside one hour - for the hours it
+        published, and one `_carried()` point for each remaining whole hour,
+        ordered by instant;
       * `no_data` when neither source can produce a single hour - never an
         empty series, which is not constructible (price.py trap 3).
 
+    ⚠️ THE WINDOW IS WHOLE HOURS AT BOTH ENDS. `since` is floored to the hour
+    that CONTAINS it, because the current hour is still a tradeable hour; and
+    so is `until`, which is the half FCST-04's first draft left out. With
+    `since` floored and `until` compared raw, a 48 h horizon asked for at 08:17
+    emitted 49 hours - the hour of `until` was still `< until` - and the count
+    was one too many for every `now` that is not exactly on the hour, which is
+    every `now` a running controller has.
+
     ⚠️ IDEMPOTENT AND RE-RUNNABLE, WHICH IS THE §5.4 LATE-PUBLICATION CONTRACT.
     Day-ahead publication at 14-16 h CET can be late or fail, so the fetcher
     retries and this runs again against the fresher read. Published hours always
@@ -234,9 +314,7 @@ def fill_from_yesterday(read: PriceRead, *, yesterday: PriceRead,
             raise ValueError(f"{name} must be tz-aware; a naive instant is "
                              f"ambiguous for one hour every October")
 
-    published = read.match(
+    published = _published_by_hour(read)
-        series=lambda r: {_utc_hour(p.start): p for p in r.points},
-        no_data=lambda _r: {})
 
     # Yesterday's profile, keyed by BRUSSELS WALL-CLOCK HOUR. First point wins
     # when yesterday itself was a 25-hour day and printed local hour 2 twice.
@@ -248,11 +326,12 @@ def fill_from_yesterday(read: PriceRead, *, yesterday: PriceRead,
 
     out = []
     u = _utc_hour(since)
-    end = until.astimezone(timezone.utc)
+    end = _utc_hour(until)
     while u < end:
-        if u in published:
+        got = published.get(u)
-            out.append(published[u])                    # BY IDENTITY. No copy.
+        if got:
-        else:
+            out.extend(got)              # BY IDENTITY, and ALL of them. No copy,
+        else:                            # and no decimation to one an hour.
             src = by_local_hour.get(brussels(u).hour)
             if src is not None:
                 out.append(_carried(u, src.eur_per_kwh))

goodwe_controller/app/price_history.py

@@ -0,0 +1,598 @@
+"""FCST-04 - the day the carry-forward carries, kept somewhere a restart cannot reach.
+
+WHAT WAS MISSING, AND WHY IT WAS INVISIBLE. FCST-03 shipped
+`price_forecast.fill_from_yesterday()` complete and checked, and shipped the
+consumers that were written to expect it - `TariffPlan.firm_points()`,
+`cheap_now()`'s refusal of a provisional hour, and `arbitrage()`'s refusal 3,
+which drops provisional hours from the trade set instead of refusing the whole
+series. Every one of those was live. The FILL ITSELF HAD NO CALLER: nothing in
+`app/` referenced `fill_from_yesterday`, so no series ever contained a carried
+point and every one of those consumers was exercising its all-firm branch.
+
+The defect that produced is not an error anywhere. `load_prices()` returns
+whatever the feed published and nothing widens it to the requested horizon, so
+on a dynamic site between midnight and the 14-16 h CET day-ahead publication
+the series covers the rest of TODAY and nothing more - typically 10-24 of the
+48 hours `price_horizon_h` asked for. `TariffPlan.arbitrage()` then computes
+`max - min` over that truncated window and reports a spread. The number is
+real, the window is half the one the operator configured, and NOTHING SAYS SO:
+tomorrow evening's peak - the hour a morning charge would be sold into - is
+simply not in the series, so the spread it would have created cannot clear a
+threshold it was never compared against. A missing hour is not a wrong price;
+it is an hour the optimiser never learns exists.
+
+So this module is the half FCST-03 left out, and it is deliberately the SMALL
+half: the fill's arithmetic, its DST rule and its provenance audit all stay in
+`price_forecast.py`, untouched. What lives here is the one thing that
+arithmetic needs and could not have: A YESTERDAY THAT SURVIVES A RESTART.
+
+
+WHY PERSISTENCE, AND NOT A VARIABLE ON THE REFRESH TASK
+======================================================
+An in-memory "the last full day I saw" costs nothing and is wrong exactly when
+it matters. The window the fill exists for is midnight -> publication; an
+add-on restarted at 08:00 - a config change, an HA update, a power cut - would
+come up with no yesterday at all and spend that whole window on the truncated
+series, which is the pre-FCST-03 behaviour arriving silently on the mornings
+after an operator touched something. The fill's own value is a function of
+surviving a restart, so the day it carries has to.
+
+⚠️ AND NOT IN `/data/state.json`. That file holds the maintenance history and
+SAFETY-02's sign latch, and `Store.set()` rewrites the whole of it on every
+write. The tariff refresh runs every `TARIFF_REFRESH_S` (1800 s), so folding a
+price cache into it would put 48 extra whole-file rewrites a day through the
+file whose corruption reads as "no maintenance ever ran" and "never tripped".
+The cache is worth having; it is not worth putting anywhere near that. Separate
+file, separate blast radius.
+
+⚠️ AND THE DIRECTORY IS NOT CREATED, which is `tariff.PeakStore`'s rule and its
+reason applies unchanged: `/data` is mounted by the Supervisor and always
+exists on a real install, so `makedirs` here could only ever succeed where the
+durable volume is MISSING - manufacturing a cache on the container's ephemeral
+layer that writes fine, reads fine, and is thrown away on the next restart.
+That is a yesterday that silently forgets, which is worse than one that says it
+cannot answer.
+
+⚠️ AND THAT RULE IS CARRIED OUT IN `_remember()`, NOT ONLY IN `_save()`. FCST-04
+first shipped it half-done: `_save()` short-circuited on `not self.ok` while
+`_remember()` filled `self._days` anyway, so a store with no durable volume
+answered `words` = "unavailable" and `yesterday()` = A SERIES - an in-memory
+yesterday that works all day and is gone on the next restart, which is exactly
+the silently-forgetting cache this rule exists to refuse. A store that cannot
+persist now records nothing, and both of its answers say the same thing.
+
+
+THE FOUR RULES THIS FILE IS SHAPED BY
+=====================================
+
+1. IT RECORDS WHAT THE PROVIDER PUBLISHED, NEVER WHAT THE FILL PRODUCED.
+   Feeding a filled series back in is the defect that makes the whole mechanism
+   rot: day 2 carries day 1's guesses, day 3 carries day 2's carry of them, and
+   after a week of a dead feed the "yesterday" being carried forward is a
+   fossil of the last real publication with nothing anywhere reporting its age.
+   Every point still carries `provisional=True`, so the flag never lies - what
+   decays is the NUMBER, silently, behind a flag that is telling the truth.
+
+   ⚠️ NO VALUE-LEVEL CHECK CAN CATCH THAT, and saying so is more useful than a
+   guarantee that would not hold. A carried point and a published-provisional
+   point (`eneco_eddy`'s current quarter, §9.2) are the same three fields with
+   the same flag; the difference is provenance, and provenance is not in the
+   value. So the mechanism is ORDERING, not validation: `carry()` is the only
+   public entry point, it remembers the argument and returns the fill, and the
+   filled series exists only as a return value that `carry()` itself never
+   sees again. `_remember()` is private, is called from exactly one place, and
+   `test_price_history.py` PARSES every shipped module under `app/`, `tools/`,
+   `scenarios/` and `estop/` and fails if any of them uses the NAME - an
+   attribute, a bare name, a def, or the string constant a `getattr` needs. By
+   name rather than by substring, so a comment about the rule does not fail it
+   and a call from `tools/` cannot pass unseen.
+
+   ⚠️ AND THE ORDER IS GRADED BY DRIVING IT, NOT BY READING THE SOURCE. The
+   first version of that check compared positions in `ast.walk`, which is
+   breadth-first: `self._remember(...)` is a statement and `self.yesterday(...)`
+   is an ARGUMENT of the fill, one level deeper, so `_remember` came out first
+   whichever statement was written first - shipped and reversed scored the
+   same. What grades it now is the behaviour: a feed carrying yesterday
+   alongside today, into an EMPTY store, must fill the whole horizon, and
+   reversed it fills nothing.
+
+2. "YESTERDAY" MEANS YESTERDAY, NOT "THE NEWEST DAY I HAVE".
+   `newest()` is the natural accessor and it is the one that decays: an add-on
+   down from Friday to Monday would answer Friday's prices to a fill that flags
+   them as one day old. The lookup is BY DATE - the Brussels day before the
+   Brussels day of the instant asked about - and a record for any other date is
+   NO_RECORD with a reason naming both dates. A three-day-old profile is not a
+   worse yesterday; it is not a yesterday.
+
+3. A STORE THAT CANNOT ANSWER SAYS SO, IN THE TYPE.
+   `yesterday()` returns a `PriceRead`: a `series` when a full record exists,
+   `no_data(reason)` for every other outcome - no file, no record for that
+   date, an unreadable file, a record that parses to nothing. There is no
+   empty-series answer and no `.get(..., [])`-shaped accessor, for
+   `price.py`'s reason: an empty series is how "the cache is broken" gets to
+   wear the shape of "yesterday was free". `fill_from_yesterday()` takes a
+   `PriceRead` and handles `no_data` on its own, so the degraded case needs no
+   branch at the call site - it fills nothing and the horizon stays short,
+   which is exactly the behaviour that shipped before this ticket.
+
+4. HOURS ACCUMULATE WITHIN A DAY; THEY DO NOT REPLACE IT.
+   A feed that serves only the REMAINING hours of the day (a legitimate shape -
+   nothing in the plugin contract promises a whole day) would, under
+   replace-the-record, overwrite a complete 24-hour profile with the two points
+   left at 22:00 and hand the next morning a yesterday with two hours in it. So
+   a record is MERGED by instant: a later read updates the hours it carries and
+   leaves the rest, and a revised price for an hour already held wins because
+   it is the newer statement about the same hour.
+
+⚠️ KEYED BY INSTANT, NOT BY LOCAL HOUR, AND THAT IS THE DST DECISION. Storing
+`hour -> price` would collapse the two 02:00s of a 25-hour October day into
+one, inventing a second and different collapsing rule beside the one
+`fill_from_yesterday()` already documents ("the first of its two 02:00 points
+is the one used, deterministically"). Storing the instants keeps both, in
+order, and lets the fill's own rule be the only one in the system.
+
+WHAT THIS DOES NOT DO, ON PURPOSE
+=================================
+It does not extend the fill to a feed that published NOTHING. `resolve_tariff()`
+applies `carry()` only on a `series` read; a `no_data` read still falls to
+`_degrade()` and §11.4's row - "No price data -> fall back to the static
+profile, mark the plan provisional, no arbitrage" - which is the fallback the
+operator configured `static_profile` FOR. Preferring yesterday's feed over it
+would change a documented degradation without being asked, and it would buy
+nothing measurable: a fully-carried series is 100 % provisional, so
+`arbitrage()` finds fewer than two firm hours and refuses, and `cheap_now()` is
+False, exactly as on the §11.4 fallback. The two differ only in which numbers
+the status page shows. `fill_from_yesterday()` handles a `no_data` read anyway,
+and that branch is therefore not reached from production - it stays checked,
+and turning it on is a product decision, not a wiring one. See
+DECISIONS/FCST-04-the-day-that-is-carried.md.
+"""
+
+import json
+import logging
+import os
+import tempfile
+from datetime import datetime, timedelta, timezone
+
+from .price import PricePoint, PriceProduct, PriceRead, brussels
+from .price_forecast import fill_from_yesterday
+
+_LOG = logging.getLogger("goodwe.price.history")
+
+# How many Brussels days of published prices the SORT-ORDER cap keeps. The fill
+# needs exactly one - yesterday - and rule 2 refuses anything older, so this is
+# not a horizon: it is the number of days a record may sit unused before
+# pruning removes it, and it is small because a bigger cache would only hold
+# days no lookup can ask for. Three covers today, yesterday, and the day a
+# fetch spanning midnight writes ahead of itself.
+#
+# ⚠️ IT IS A CAP, NOT THE RETENTION RULE, AND THREE HAS NO SLACK. The steady
+# state is already {yesterday, today, tomorrow}; a feed that publishes to D+2,
+# or ONE stray point in the wrong year - which sorts LAST and is therefore
+# immortal under a newest-N cap - pushes yesterday out of a three-slot store
+# and keeps it out, permanently and silently. So `_prune()` PINS the two days a
+# lookup can actually ask for on top of the cap; see its docstring. The store
+# is then bounded at KEEP_DAYS + 2 records rather than at KEEP_DAYS.
+KEEP_DAYS = 3
+
+SCHEMA = 1
+
+
+def _bdate(instant: datetime) -> str:
+    """The Brussels calendar date of an instant, as `YYYY-MM-DD`.
+
+    ⚠️ BRUSSELS, NOT UTC. 23:30 UTC in July is already tomorrow in Belgium, and
+    a cache keyed on the UTC date would file the last 90-120 minutes of every
+    day under the wrong one - so a lookup on the following morning would find a
+    "yesterday" missing its own evening hours, which are the expensive ones.
+    """
+    return brussels(instant).strftime("%Y-%m-%d")
+
+
+def _yesterday_of(instant: datetime) -> str:
+    """The Brussels date of the day BEFORE `instant`'s Brussels day.
+
+    ⚠️ THE ARITHMETIC IS ON THE LOCAL DATE, NOT ON THE INSTANT, AND THAT IS A
+    DST DEFECT THIS FILE SHIPPED. `brussels()` renders at the FIXED offset in
+    force at that instant, so `brussels(stamp) - timedelta(days=1)` subtracts 24
+    ABSOLUTE hours from a wall clock - and the Brussels day before a
+    spring-forward is 23 hours long. Measured at 2026-03-30T00:30+02:00, the
+    first hour of the morning after the March transition: it returned
+    2026-03-28, so the fill carried a TWO-DAY-OLD profile flagged as yesterday's
+    (or, with only the last three days held, answered `no_data` naming a date
+    that is not yesterday).
+
+    A calendar day minus one day is `date` arithmetic, and a `date` has no
+    offset to lose. The 25-hour October day is right for the same reason.
+    """
+    return (brussels(instant).date() - timedelta(days=1)).strftime("%Y-%m-%d")
+
+
+def _n_points(rec) -> int:
+    """How many points a day record holds. 0 for anything that is not one.
+
+    ⚠️ TOLERANT, AND IT IS THE SECOND LINE OF DEFENCE, NOT THE FIRST. `_load()`
+    drops a malformed day record and says so, so this should never see one. It
+    is written this way because `words` is read from `Controller.__init__` and
+    from every status render: a status LINE that raises takes the add-on down,
+    and "the cache is broken" must never be able to mean "the controller does
+    not start". That is exactly what FCST-04 shipped - `{"days": {"2026-01-14":
+    "oops"}}` gave `ok=True`, `last_error=None`, and an `AttributeError` out of
+    `words`, `yesterday()` and `resolve_tariff()` alike, with no self-heal
+    because `_remember()` raised before it could rewrite the file.
+    """
+    if not isinstance(rec, dict):
+        return 0
+    pts = rec.get("points")
+    return len(pts) if isinstance(pts, (list, tuple)) else 0
+
+
+class PriceHistory:
+    """The published price series of the last few Brussels days, in /data.
+
+    ⚠️ `ok` IS ABOUT THE FILE, NOT ABOUT THE DATA. A healthy store with no
+    record for yesterday is `ok` and answers `no_data` - a normal state on a
+    site's first day, and a different thing from a store that could not be
+    opened. Both are visible: `ok`/`last_error` describe the file, and
+    `yesterday()`'s reason describes the answer.
+    """
+
+    def __init__(self, path: str = "/data/price_history.json"):
+        self.path = path
+        self.ok = False
+        self.last_error: str | None = None
+        self._days: dict = {}
+        self._open()
+
+    # -- the file ------------------------------------------------------------
+    def _open(self) -> None:
+        parent = os.path.dirname(self.path)
+        # See the module note: NOT created. A cache on the ephemeral layer is
+        # one that forgets without saying so.
+        if parent and not os.path.isdir(parent):
+            self.last_error = f"no durable volume at {parent}"
+            # INFO, not ERROR: on a dev host or in a test container there is no
+            # /data and nothing is wrong.
+            _LOG.info("no price history: %s - §8.3 carry-forward has nothing "
+                      "to carry and the horizon stays as short as the feed",
+                      self.last_error)
+            return
+        self.ok = True
+        self._load()
+
+    def _load(self) -> None:
+        try:
+            with open(self.path, "r", encoding="utf-8") as fh:
+                blob = json.load(fh)
+        except FileNotFoundError:
+            _LOG.info("no price history yet at %s - the first refresh writes "
+                      "one, and the fill has nothing to carry until the day "
+                      "after that", self.path)
+            return
+        except (json.JSONDecodeError, OSError) as err:
+            # A corrupt cache must not stop the controller, and must not be
+            # silently re-created either: the record is discarded, the reason
+            # is kept, and `yesterday()` reports it rather than answering
+            # "no record", which would read as a normal first day.
+            self.last_error = f"unreadable ({err})"
+            _LOG.warning("price history at %s is %s - starting from empty. "
+                         "§8.3 carry-forward has nothing to carry until the "
+                         "next refresh has written a full day",
+                         self.path, self.last_error)
+            return
+        found = blob.get("version") if isinstance(blob, dict) else None
+        # ⚠️ THE TYPE IS PART OF THE VERSION. `1.0 == 1` in Python, so a float
+        # written by some other tool would pass a bare `!=` and be read as
+        # schema 1 - a version check that cannot tell 1 from 1.0 is one that
+        # would not notice a writer this build has never met.
+        if not isinstance(blob, dict) or isinstance(found, bool) \
+                or not isinstance(found, int) or found != SCHEMA:
+            self.last_error = f"schema {found!r}, not {SCHEMA}"
+            _LOG.warning("price history at %s has %s - discarding it rather "
+                         "than guessing what its points mean",
+                         self.path, self.last_error)
+            return
+        days = blob.get("days")
+        if not isinstance(days, dict):
+            self.last_error = "no `days` object"
+            _LOG.warning("price history at %s has %s", self.path, self.last_error)
+            return
+        self._days = self._usable_days(days)
+
+    def _usable_days(self, days: dict) -> dict:
+        """The day records that are shaped like day records. The rest are dropped.
+
+        ⚠️ THE ASYMMETRY THAT PRODUCED THE DEFECT: `_parse_points()` below is
+        carefully defensive about every field of a POINT, and `_load()` was not
+        defensive about the record holding them at all. `{"version": 1, "days":
+        {"2026-01-14": "oops"}}` therefore loaded as `ok=True`,
+        `last_error=None` - and then `rec.get(...)` raised `AttributeError` out
+        of `words`, `yesterday()` and `resolve_tariff()`. `PriceHistory(...)`
+        and `.words` are both unguarded in `Controller.__init__`, so THE ADD-ON
+        DID NOT START; and it never self-healed, because `_remember()` raised on
+        the same record before it could reach `_save()`.
+
+        A broken cache is a short horizon. It is not a controller that will not
+        regulate a battery, and §6's rule - absent machinery must not disable
+        the loop - does not stop applying because the machinery is a JSON file.
+
+        Dropped, not repaired: an unusable record has nothing in it to keep, and
+        the next `_remember()` writes a fresh one under that date.
+        """
+        kept, dropped = {}, []
+        for key, rec in days.items():
+            if not isinstance(key, str) or not isinstance(rec, dict) \
+                    or not isinstance(rec.get("points"), list):
+                dropped.append(str(key))
+                continue
+            kept[key] = rec
+        if dropped:
+            # Recorded, not silent: `yesterday()` and `words` both report
+            # `last_error`, and a cache that quietly discards half a file reads
+            # to an operator exactly like a normal first day.
+            self.last_error = (f"{len(dropped)} unusable day record(s) dropped "
+                               f"({', '.join(sorted(dropped))})")
+            _LOG.warning("price history at %s: %s - the controller starts "
+                         "anyway and the horizon is as short as the feed makes "
+                         "it", self.path, self.last_error)
+        return kept
+
+    def _save(self) -> None:
+        if not self.ok:
+            return
+        # ⚠️ THE TEMP FILE IS REMOVED ON EVERY FAILING PATH. A write that dies
+        # between `mkstemp` and `os.replace` used to leave its temp behind, and
+        # the refresh task runs 48 times a day: a persistent write failure -
+        # a full volume being the likeliest cause - leaked 48 inodes a day onto
+        # the volume that was already the problem.
+        tmp = None
+        try:
+            fd, tmp = tempfile.mkstemp(dir=os.path.dirname(self.path))
+            with os.fdopen(fd, "w", encoding="utf-8") as fh:
+                json.dump({"version": SCHEMA, "days": self._days}, fh, indent=1)
+            # Atomic: a power cut mid-write must not leave a truncated file
+            # that parses as an empty day.
+            os.replace(tmp, self.path)
+            tmp = None                      # it IS the file now; do not unlink
+        except OSError as err:
+            self.last_error = f"could not write ({err})"
+            _LOG.error("could not persist price history: %s", err)
+        finally:
+            if tmp is not None:
+                try:
+                    os.unlink(tmp)
+                except OSError:             # nothing further to try, and a
+                    pass                    # failed cleanup is not a fault
+
+    # -- the one public entry point -----------------------------------------
+    def carry(self, read: PriceRead, *, since: datetime, until: datetime,
+              stamp: datetime) -> PriceRead:
+        """Remember what this read published, then §8.3-fill the missing hours.
+
+        THE ORDER IS DELIBERATE AND IS THE POINT OF THE METHOD. The read is
+        recorded FIRST, so a feed that hands back yesterday alongside today
+        refreshes yesterday's record from live data before it is consumed as
+        the profile; and the filled series - the one thing that must never be
+        recorded - exists only as this method's return value, which this object
+        never sees again. See rule 1, including how that order is graded.
+
+        Returns whatever `fill_from_yesterday()` returns: a series over the
+        whole hours of [since, until), carrying EVERY point the provider
+        published inside it - by identity, and four of them in one hour on a
+        quarter-hourly feed - plus one carried point for each remaining whole
+        hour FOR WHICH YESTERDAY HELD THAT WALL-CLOCK HOUR. An hour neither
+        source can price is left out (§11.4 for that hour), and `no_data` comes
+        back when that is every hour.
+        """
+        self._remember(read, stamp)
+        return fill_from_yesterday(read, yesterday=self.yesterday(stamp),
+                                   since=since, until=until, stamp=stamp)
+
+    # -- the halves, private because rule 1 is an ordering ------------------
+    def _remember(self, read: PriceRead, stamp: datetime) -> None:
+        """File a provider read's points under their own Brussels days.
+
+        ⚠️ PRIVATE, AND CALLED FROM EXACTLY ONE PLACE. A caller that can reach
+        this can record a filled series, which is the decay in rule 1. There is
+        no value-level defence against that - a carried point and a published
+        provisional point are the same three fields - so the defence is that
+        nothing outside this file names it, and `test_price_history.py` checks
+        the tree for that rather than trusting the underscore.
+        """
+        if not self.ok:
+            # ⚠️ A STORE THAT CANNOT PERSIST RECORDS NOTHING. See the module
+            # docstring's third warning: filling `self._days` here would give a
+            # site with no /data an in-memory yesterday that answers a series
+            # all day and is gone on the next restart - a cache that forgets
+            # without saying so, which is the one thing that rule refuses. The
+            # honest degraded state is `words` = "unavailable" and `yesterday()`
+            # = `no_data`, and those two must agree.
+            return
+        points = read.match(series=lambda r: r.points, no_data=lambda _r: ())
+        if not points:
+            return
+        product = read.match(series=lambda r: r.product.value,
+                             no_data=lambda _r: None)
+        provider = read.match(series=lambda r: r.provider,
+                              no_data=lambda _r: None)
+
+        touched = set()
+        for p in points:
+            day = _bdate(p.start)
+            rec = self._days.setdefault(
+                day, {"product": product, "provider": provider, "points": []})
+            # Rule 4: MERGE by instant. A later read updates the hours it
+            # carries and leaves the rest; a revised price for an hour already
+            # held wins, because it is the newer statement about that hour.
+            raw = rec.get("points")
+            held = {q["start"]: q for q in (raw if isinstance(raw, list) else ())
+                    if isinstance(q, dict) and "start" in q}
+            held[p.start.isoformat()] = p.canonical()
+            rec["points"] = sorted(held.values(), key=lambda q: q["start"])
+            rec["product"], rec["provider"] = product, provider
+            touched.add(day)
+
+        self._prune(stamp)
+        self._save()
+        _LOG.debug("price history: %d point(s) filed under %s; %d day(s) held",
+                   len(points), ", ".join(sorted(touched)), len(self._days))
+
+    def _prune(self, stamp: datetime) -> None:
+        """Drop records no lookup can reach. A sort-order cap, plus two pins.
+
+        ⚠️ NOTHING IS DELETED BY ARITHMETIC AGAINST THE CLOCK. A clock that
+        jumped - the failure mode WITNESS-03 spent a session on - would
+        otherwise delete every record in one pass and leave the fill with
+        nothing on the morning after, which is the one morning it is for.
+        Deleting on a bad clock is unrecoverable; holding a few days too many
+        is not, so the cap is `sorted(...)[-KEEP_DAYS:]` and stays that way.
+
+        ⚠️ AND A CAP ALONE IS DEFEATED BY ONE POINT IN THE WRONG YEAR. Sorting
+        is lexicographic on the date string, so a stray far-future record sorts
+        LAST and is immortal - it consumes a slot for good, and with the steady
+        state already {yesterday, today, tomorrow} filling all three, yesterday
+        is what falls out. A feed that publishes to D+2 does the same thing
+        without any stray at all. So the two days `yesterday()` can ACTUALLY be
+        asked for are pinned on top of the cap.
+
+        `stamp` is READ here, which it was not before: the pin is the only use
+        of it, and it is additive. Pinning can only RETAIN a record, never
+        delete one, so a jumped `stamp` pins two dates that are not held and
+        changes nothing - the WITNESS-03 property is preserved by construction
+        rather than by remembering to check it.
+        """
+        if len(self._days) <= KEEP_DAYS:
+            return
+        keep = set(sorted(self._days)[-KEEP_DAYS:])
+        keep |= {_bdate(stamp), _yesterday_of(stamp)}
+        for day in [d for d in self._days if d not in keep]:
+            del self._days[day]
+
+    def yesterday(self, stamp: datetime) -> PriceRead:
+        """The published series of the Brussels day BEFORE `stamp`'s, or no_data.
+
+        ⚠️ THE DATE IS COMPUTED, NOT LOOKED UP. See rule 2: `newest()` would
+        answer Friday's prices to a Monday fill, and the fill would flag them as
+        one day old because that is the only thing its flag can say.
+        """
+        if stamp.tzinfo is None or stamp.utcoffset() is None:
+            raise ValueError(
+                f"yesterday({stamp!r}): a naive datetime is not an instant, "
+                f"and 'which Brussels day was yesterday' is exactly the "
+                f"question a wall-clock reading cannot answer.")
+        want = _yesterday_of(stamp)
+        if self.last_error and not self._days:
+            return PriceRead.no_data(
+                f"the price history at {self.path} is {self.last_error}, so "
+                f"§8.3 has no profile to carry forward for {want}; the plan "
+                f"covers only the hours the feed published")
+        rec = self._days.get(want)
+        if rec is None:
+            have = ", ".join(sorted(self._days)) or "no days at all"
+            return PriceRead.no_data(
+                f"no published prices recorded for {want} (held: {have}), so "
+                f"§8.3 has no profile to carry forward. A record for another "
+                f"day is not a yesterday")
+        points, bad = _parse_points(rec.get("points"))
+        if not points:
+            why = bad or "it is empty"
+            return PriceRead.no_data(
+                f"the {want} record holds no usable point ({why}), and an "
+                f"empty series is not a free day")
+        try:
+            product = PriceProduct(rec.get("product"))
+        except ValueError:
+            return PriceRead.no_data(
+                f"the {want} record names product {rec.get('product')!r}, "
+                f"which is not a PriceProduct. The optimiser switches on that "
+                f"enum, so a record that cannot name one cannot be a series")
+        if bad:
+            _LOG.warning("price history: %s in the %s record were dropped; "
+                         "%d point(s) carried forward", bad, want, len(points))
+        return PriceRead.series(points, product,
+                                str(rec.get("provider") or "price_history"),
+                                stamp)
+
+    # -- observability -------------------------------------------------------
+    @property
+    def words(self) -> str:
+        """One line for the status page. Says what is held, or why nothing is.
+
+        ⚠️ THIS MUST NOT RAISE, EVER. It is read once from `Controller.__init__`
+        and again on every status render, and neither call site guards it - so
+        an exception here is an add-on that does not start. It went out that
+        way: a day record that was a string instead of a dict raised
+        `AttributeError` from the `len(...)` below. `_load()` now drops such a
+        record and `_n_points()` is total, so this has two independent reasons
+        not to fail on a broken file.
+        """
+        if not self.ok:
+            return f"unavailable - {self.last_error}"
+        if not self._days:
+            why = f" - {self.last_error}" if self.last_error else ""
+            return f"empty{why} - nothing to carry forward yet"
+        held = "; ".join(f"{d} ({_n_points(self._days[d])} h)"
+                         for d in sorted(self._days, key=str))
+        # A file that PARTLY loaded says so, or the dropped days read as days
+        # that were simply never written.
+        return held + (f" [{self.last_error}]" if self.last_error else "")
+
+
+def _parse_points(raw) -> tuple:
+    """Canonical dicts -> PricePoints, and a phrase naming what was dropped.
+
+    ⚠️ A MALFORMED POINT IS DROPPED, NOT DEFAULTED, and the drop is reported.
+    `float(row.get("eur_per_kwh", 0))` is the shape of the whole family of
+    defects this repo has been removing: a cache that lost a field would answer
+    "that hour was free" to a fill that flags it as an ordinary guess.
+    """
+    if not isinstance(raw, list):
+        return (), "the `points` field is not a list"
+    out, dropped = [], 0
+    for row in raw:
+        if not isinstance(row, dict):
+            dropped += 1
+            continue
+        try:
+            start = datetime.fromisoformat(row["start"])
+            value = float(row["eur_per_kwh"])
+            flag = row["provisional"]
+        except (KeyError, TypeError, ValueError):
+            dropped += 1
+            continue
+        if start.tzinfo is None or start.utcoffset() is None \
+                or not isinstance(flag, bool):
+            dropped += 1
+            continue
+        out.append(PricePoint(start=start, eur_per_kwh=value, provisional=flag))
+    out.sort(key=lambda p: p.start.astimezone(timezone.utc))
+    return tuple(out), (f"{dropped} malformed point(s)" if dropped else "")
+
+
+class NoHistory:
+    """The explicit "this caller keeps no history" - a NAME, not a `None`.
+
+    ⚠️ IT EXISTS SO THE PARAMETER CAN BE REQUIRED. `history=None` meaning "skip
+    the fill" is the shape this repo keeps removing: a caller who forgets the
+    argument gets the truncated-horizon behaviour of the bug this ticket is
+    about, silently, and the code reads as though the fill is happening. With
+    no default there is nothing to forget, and a caller with no durable volume
+    - a check, a replay harness - has to say `NoHistory()` and be visible in
+    the diff.
+
+    It carries out the ordering faithfully: it records nothing and carries
+    nothing, so `carry()` returns the provider's read unchanged and the plan is
+    exactly what it was before FCST-04.
+    """
+
+    ok = False
+    last_error = "no history is kept by this caller"
+    words = "not kept"
+
+    def carry(self, read: PriceRead, *, since, until, stamp) -> PriceRead:
+        return read
+
+    def yesterday(self, stamp: datetime) -> PriceRead:
+        return PriceRead.no_data(
+            "this caller keeps no price history (NoHistory), so §8.3 has no "
+            "profile to carry forward")

goodwe_controller/app/static_tariff.py

@@ -1019,7 +1019,7 @@ def static_status(opts: dict, now: datetime):
 
 
 async def resolve_tariff(opts: dict, since: datetime, until: datetime,
-                         transport=None, now=None) -> TariffPlan:
+                         transport=None, now=None, *, history) -> TariffPlan:
     """The full §9.2 + §11.4 resolution. MAY PERFORM I/O - see `static_plan`.
 
     ⚠️ NOT ON THE 30 s TICK, and that is a deliberate boundary rather than an
@@ -1033,9 +1033,42 @@ async def resolve_tariff(opts: dict, since: datetime, until: datetime,
       price_provider off  + profile  -> the CONFIGURED product (§9.2 rows 3-4)
       price_provider off  + none     -> no prices at all (§11.4, nothing to
                                         fall back to)
-      provider series                -> the feed (§9.2 rows 1-2)
+      provider series                -> the feed, §8.3-FILLED (§9.2 rows 1-2)
       provider no_data    + profile  -> §11.4 FALLBACK, provisional, no arbitrage
       provider no_data    + none     -> no prices at all
+
+    ⚠️ `history` IS REQUIRED, KEYWORD-ONLY, AND HAS NO DEFAULT (FCST-04). It is
+    the §8.3 carry-forward store - `price_history.PriceHistory`, or the explicit
+    `price_history.NoHistory()` for a caller that keeps none. A default of
+    `None` meaning "skip the fill" would give a caller who forgot the argument
+    the TRUNCATED HORIZON this ticket exists to remove, silently, while the code
+    read as though the fill were happening. There is nothing to forget now.
+
+    ⚠️ AND THE FILL RUNS ONLY ON A `series` READ. A feed that published nothing
+    still falls to `_degrade()` and §11.4's own row - the static profile the
+    operator configured FOR that case - rather than to yesterday's feed. The two
+    are indistinguishable to the optimiser (both are 100 % provisional, so
+    `arbitrage()` finds fewer than two firm hours and refuses, and `cheap_now()`
+    is False), so preferring yesterday would change a documented degradation for
+    a difference only the status page can see. See price_history.py's closing
+    note and DECISIONS/FCST-04-the-day-that-is-carried.md.
+
+    ⚠️ THE FILL IS PER WHOLE HOUR AND ITS COVERAGE IS CONDITIONAL. Every point
+    the provider published inside the window passes through BY IDENTITY - four
+    of them in one hour on a quarter-hourly product like `eneco_eddy` - and a
+    carried point is added only for a whole hour the feed did not print at all
+    AND yesterday did. An hour neither source can price is left out, which is
+    §11.4 for that hour: `plan.price_at()` raises rather than answering, and an
+    hour with no price is not a free one.
+
+    ⚠️ THE FILLED SERIES IS WINDOWED TO [since, until), AND THAT IS A CHANGE.
+    `load_prices()` returns whatever the feed sent, past hours included, and
+    `TariffPlan.arbitrage()` took its spread over all of it - so an hour that
+    had already gone could be the cheapest hour of a cycle nothing can now buy
+    in. `fill_from_yesterday()` walks the requested horizon and emits exactly
+    that, so the spread is over hours that are still ahead. Both directions of
+    the difference are real: the window gains the unpublished hours it was
+    missing and loses the elapsed ones it should never have had.
     """
     stamp = now or datetime.now(timezone.utc)
     pid = str(price_option(opts, "price_provider") or "off").strip()
@@ -1044,6 +1077,20 @@ async def resolve_tariff(opts: dict, since: datetime, until: datetime,
 
     read = await load_prices(opts, since, until, transport)
     return read.match(
+        series=lambda r: _provider_plan(opts, r, since, until, stamp, history),
+        no_data=lambda r: _degrade(opts, r, since, until, stamp))
+
+
+def _provider_plan(opts, read, since, until, stamp, history) -> TariffPlan:
+    """§8.3: record what the feed published, carry yesterday into the gaps.
+
+    The fill can itself return `no_data` - a feed whose points all fall outside
+    the horizon, with nothing in the history to fill it from - and that is the
+    §11.4 row arrived at one step later, so it degrades exactly as a failed
+    fetch does rather than being special-cased here.
+    """
+    filled = history.carry(read, since=since, until=until, stamp=stamp)
+    return filled.match(
         series=lambda r: TariffPlan(r, _quiet_profile(opts), "provider"),
         no_data=lambda r: _degrade(opts, r, since, until, stamp))
 

goodwe_controller/app/store.py

@@ -253,7 +253,7 @@ class MigrationReport:
         return out
 
 
-def migrate_unit_keys(store, unit: str) -> MigrationReport:
+def migrate_unit_keys(store, unit: str, roster=None) -> MigrationReport:
     """Move the pre-DEV-02 flat per-inverter keys into `unit`'s namespace.
 
     `unit` is the FIRST inverter in the roster, which on every install that can
@@ -261,6 +261,24 @@ def migrate_unit_keys(store, unit: str) -> MigrationReport:
     version that knew about more than one inverter is already at
     SCHEMA_VERSION and is not touched.
 
+    ⚠️ `roster` IS THE NAMES THE MACHINES READ, AND IT IS SAFETY-44. This
+    function shipped WITHOUT it, taking a hardcoded `inverter.UNIT_A` at its one
+    call site - which is, exactly, the MAINT-05 defect `_verify_moves()` spends
+    a paragraph describing, still live in the sibling that paragraph was written
+    beside. On a store that ran pre-DEV-02 flat and declares
+    `inverters: [garage, shed]`, the latch moved to `unit/inverter-a/
+    sign_tripped`, was read back under that same name, was SATISFIED, and
+    stamped the marker - so the next start skipped the migration too and NO
+    inverter came up latched on an install whose state file says `sign_tripped:
+    true`. A disarmed SAFETY-02 guard, every symptom of a clean migration.
+
+    `roster_names(opts)` answers this BEFORE any `Inverter` exists - it is
+    defined to, for `MqttPublisher`, which is constructed before the roster for
+    the same reason - so the "there is no roster yet" that kept this argument
+    out was never true. On the flat shape it returns `[UNIT_A]`, so the upgrade
+    every install runs today passes `unit == roster[0] == UNIT_A` and is
+    byte-identical.
+
     THE THREE RULES, each one a case that would otherwise be a wrong answer:
 
     1. IT NEVER OVERWRITES AN EXISTING NAMESPACED VALUE. A store that has both
@@ -302,7 +320,7 @@ def migrate_unit_keys(store, unit: str) -> MigrationReport:
 
     rep.ran = True
     _move_flat_keys(store, unit, LEGACY_UNIT_KEYS, rep)
-    _verify_moves(store, rep)
+    _verify_moves(store, rep, roster)
 
     if rep.ok:
         store.set(SCHEMA_KEY, SCHEMA_VERSION)
@@ -383,12 +401,26 @@ def _verify_moves(store, rep: MigrationReport, roster=None) -> None:
     itself. `test_maintenance.py` section 9c calls this twice with the SAME
     wrong `unit` over one store, which is the shape nothing in the suite had.
 
-    `roster=None` means "not graded", and the one caller that passes it is
+    `roster=None` still means "not graded", and SAFETY-44 is what it cost. This
-    `migrate_unit_keys()`, which runs BEFORE `build_roster()` for the reason its
+    paragraph used to end here, saying that the one caller passing it was
-    own docstring gives - the `Inverter` objects restore their latch in their
+    `migrate_unit_keys()`, "which runs BEFORE `build_roster()` ... so the keys
-    constructors, so the keys have to be in place before there is a roster to
+    have to be in place before there is a roster to check against", and calling
-    check against. That gap is real and is recorded as a running check rather
+    that gap real. THE FIRST HALF IS TRUE AND THE CONCLUSION IS NOT. The keys do
-    than left to a comment: see test_maintenance.py section 13.
+    have to be written before the `Inverter`s restore from them - but the NAMES
+    do not come from the `Inverter`s. `roster_names(opts)` reads them straight
+    off the options, before anything is constructed, which is the whole reason
+    it exists (`MqttPublisher` is built before the roster too). So the argument
+    that could have graded that write was available at the call site the entire
+    time, and the sibling function three screens down had already been fixed by
+    passing it.
+
+    ⚠️ SO NO CALLER PASSES `None` TODAY, and this branch is kept for one reason:
+    it is what a NEW caller gets by DEFAULT. A future migration that forgets the
+    roster gets the ungraded read-back and stamps its marker over a namespace no
+    machine reads - silently, exactly as this one did. That is the shape of both
+    defects, and the gap is recorded as a running check rather than left to a
+    comment: test_maintenance.py section 13, and test_rehearse.py part 5, which
+    drives it end-to-end through the harness an operator actually runs.
     """
     for target, value in rep.moved.items():
         got = getattr(store, "data", {}).get(target, "<<missing>>")

goodwe_controller/test_maintenance.py

@@ -21,6 +21,7 @@ Read MUTATION.md before you report a survivor.
 
 import asyncio
 import dataclasses
+import logging
 import re
 import sys
 from datetime import datetime, timedelta, timezone
@@ -34,7 +35,8 @@ from app.inverter import UNIT_A
 from app.main import Controller
 from app.store import (
     DEFAULTS, MAINT_SCHEMA_KEY, MAINT_SCHEMA_VERSION, MAINT_UNIT_KEYS,
-    migrate_maint_keys, unit_key,
+    SCHEMA_KEY, SCHEMA_VERSION, migrate_maint_keys, migrate_unit_keys,
+    unit_key,
 )
 
 fails = []
@@ -1411,45 +1413,39 @@ check("...while the SAME site with the house importing more than the drain "
 
 # --------------------------------------------------------------------------- #
 print()
-print("13. RECORDED, NOT FIXED: SAFETY-02's migration has the same "
+print("13. FIXED (SAFETY-44): SAFETY-02's migration takes the roster too, and "
-      "wrong-namespace hole, and it is a LATCH")
+      "the guard is no longer defeated by the key the defect wrote")
 
-# ⚠️ FOUND WHILE FIXING THIS CARD'S OWN INSTANCE, AND WRITTEN DOWN AS A RUNNING
+# ⚠️ THIS SECTION USED TO BE THE SPECIFICATION OF A DEFECT. It was written while
-# CHECK RATHER THAN A COMMENT SO IT CANNOT BE FORGOTTEN OR QUIETLY "FIXED" BY AN
+# fixing MAINT-05's own instance, as a RUNNING check rather than a comment, with
-# UNRELATED EDIT. It is the SAME defect one module over, and it costs more.
+# the instruction that "the card that fixes it should expect them to go red and
+# should replace them". SAFETY-44 is that card and this is that replacement.
 #
-# WHAT IT IS. `Controller.__init__` calls `migrate_unit_keys(store, UNIT_A)` -
+# WHAT IT WAS. `Controller.__init__` called `migrate_unit_keys(store, UNIT_A)` -
-# a hardcoded constant, where the maintenance migration now passes the roster's
+# a hardcoded constant, where the maintenance migration already passed the
-# own first name. It has to run BEFORE `build_roster()`, because each
+# roster's own first name. On a DECLARED roster the pre-DEV-02 flat
-# `Inverter` restores its sign latch in its constructor, so there is no roster
+# `sign_tripped: true` landed under `unit/inverter-a/sign_tripped`, which no
-# to name yet and `_verify_moves()` is passed `roster=None`. On a DECLARED
+# unit on the site reads, and `_verify_moves()` read it back under the name it
-# roster the pre-DEV-02 flat `sign_tripped: true` therefore lands under
+# had been handed and was satisfied.
-# `unit/inverter-a/sign_tripped`, which no unit on this site reads.
 #
-# WHY THE EXISTING GUARD DOES NOT CATCH IT, WHICH IS THE PART WORTH PINNING.
+# AND THE GUARD DID NOT CATCH IT, WHICH WAS THE PART WORTH PINNING.
-# `_grade_store_migration()` re-arms the latch when the flat key says tripped
+# `_grade_store_migration()` re-arms when the flat key says tripped and NOTHING
-# and NOTHING NAMESPACED IS LATCHED. The misdirected write IS namespaced and IS
+# NAMESPACED IS LATCHED - and the misdirected write IS namespaced and IS
-# latched, so `namespaced_latched` is True, the guard returns, and no inverter
+# latched. The guard was defeated by the very key the defect wrote.
-# on the roster comes up tripped. The guard is defeated by the very key the
-# defect wrote.
 #
-# WHY IT IS NOT FIXED HERE. The remedy is to name the migration's target from
+# ⚠️ THE REASON IT WAS LEFT - "there is no roster to name yet, because each
-# the config before any `Inverter` exists, which means factoring
+# `Inverter` restores its latch in its constructor" - WAS THE HALF-TRUTH THAT
-# `build_roster()`'s naming rule out of `build_roster()` so there is still only
+# KEPT IT ALIVE. The keys must be written before the `Inverter`s read them; the
-# ONE spelling of it - inverter.py and SAFETY-02's latch semantics, with its own
+# NAMES do not come from the `Inverter`s. `roster_names(opts)` reads them off
-# mutation battery over test_inverter.py and test_watchdog.py. MAINT-05 moves
+# the options before anything is constructed, which is what it already existed
-# the maintenance history and nothing about the sign latch.
+# to do for `MqttPublisher`. The factoring this section said the fix would need
-#
+# had been done a card earlier.
-# ⚠️ AND IT IS A DISARMED SAFETY GUARD, NOT LOST HISTORY. Read the checks below
-# as the SPECIFICATION OF A DEFECT: every one of them is asserting the WRONG
-# behaviour, on purpose, and the card that fixes it should expect them to go
-# red and should replace them.
 #
 # ⚠️ NO `schema_version` IN THIS STORE, AND THAT IS THE PRE-DEV-02 SHAPE
 # ITSELF: an install that has never run a version with namespaced keys, which is
 # what makes `migrate_unit_keys()` run at all.
 _lat_store = MemStore({"sign_tripped": True,
-                       "sign_reason": "SIGN_DISAGREEMENT: measured pre-DEV-02"})
+                       "sign_reason": "SIGN_DISAGREEMENT: SYNTHETIC FIXTURE, not measured"})
 _lat, _ = controller(NAMED_OPTS, store=_lat_store)
 print(f"    pre-DEV-02 flat latch + declared roster {_C2_NAMES} -> "
       f"{_lat.store_migration.explain()}")
@@ -1457,29 +1453,179 @@ print(f"    latch keys in the store: "
       f"{sorted(k for k in _lat_store.data if k.endswith('sign_tripped'))}")
 print(f"    roster came up tripped: "
       f"{[(i.name, i.sign_wd.tripped) for i in _lat.inverters]}")
-check("the flat pre-DEV-02 latch is migrated into `unit/inverter-a/` - a name "
+check("⭐ the flat pre-DEV-02 latch is migrated into the ROSTER'S OWN first "
-      "that is NOT on this roster, so no unit reads it. This is the same "
+      "namespace and NOT into `unit/inverter-a/` - the same wrong-namespace "
-      "wrong-namespace write `migrate_maint_keys()` now refuses, in the "
+      "write `migrate_maint_keys()` refuses, now refused in the migration that "
-      "migration that runs before there is a roster to grade against",
+      "runs before the `Inverter` objects exist",
-      _lat_store.data.get(unit_key(UNIT_A, "sign_tripped")) is True
+      _lat_store.data.get(unit_key(_C2_NAMES[0], "sign_tripped")) is True
-      and unit_key(_C2_NAMES[0], "sign_tripped") not in _lat_store.data)
+      and unit_key(UNIT_A, "sign_tripped") not in _lat_store.data)
-check("⚠️ AND NO INVERTER ON THE ROSTER COMES UP LATCHED, on a store whose file "
+check("⭐ AND AN INVERTER ON THE ROSTER COMES UP LATCHED, which is the whole "
-      "still reads `sign_tripped: true`. That is DEV-02's own sentence for the "
+      "card: a store whose file reads `sign_tripped: true` no longer produces "
-      "worst case - a disarmed safety guard on an install that believes it is "
+      "a site that drives",
-      "protected",
+      _lat.inverters[0].sign_wd.tripped
-      not any(i.sign_wd.tripped for i in _lat.inverters)
       and _lat_store.data["sign_tripped"] is True)
-check("...and `_grade_store_migration()` is DEFEATED BY THE KEY THE DEFECT "
+check("...and the latch that came back carries the REASON, not just the "
-      "WROTE, which is why this needs a card rather than a tweak: its "
+      "boolean - an operator meeting a FAILSAFE banner with no sentence under "
-      "'is anything namespaced latched' test is satisfied by the misdirected "
+      "it has been told the site stopped and not why",
-      "value itself, so it returns instead of re-arming",
+      "SIGN_DISAGREEMENT" in _lat.inverters[0].sign_wd.reason)
-      any(k.startswith("unit/") and k.endswith("/sign_tripped") and v
+check("⚠️ ...and the OTHER units on the roster are NOT latched by it. The flat "
-          for k, v in _lat_store.data.items())
+      "key is one site-level boolean and re-arming every unit off it would be "
-      and not any(i.sign_wd.tripped for i in _lat.inverters))
+      "DEV-02's defect in the opposite direction - a healthy pack parked "
+      "because its sibling once disagreed",
+      not any(i.sign_wd.tripped for i in _lat.inverters[1:]))
+
+# ⚠️ AND THE OTHER PATH, WHICH THE MIGRATION FIX ALONE DOES NOT REACH: a store
+# ALREADY STAMPED by the shipped version. `migrate_unit_keys()` returns at its
+# `from_version >= SCHEMA_VERSION` check and never moves anything, so the
+# stranded `unit/inverter-a/sign_tripped` just sits there. This is the STAGED
+# shape - "upgrade now, declare the roster later" - and it is the one an
+# operator actually produces. Only the GUARD repairs it.
+_staged_store = MemStore({
+    "sign_tripped": True,
+    "sign_reason": "SIGN_DISAGREEMENT: SYNTHETIC FIXTURE, not measured",
+    unit_key(UNIT_A, "sign_tripped"): True,
+    unit_key(UNIT_A, "sign_reason"): "SIGN_DISAGREEMENT: SYNTHETIC FIXTURE, not measured",
+    SCHEMA_KEY: SCHEMA_VERSION})
+_staged, _ = controller(NAMED_OPTS, store=_staged_store)
+print(f"    already-stamped store + declared roster -> ran="
+      f"{_staged.store_migration.ran}, came up tripped: "
+      f"{[(i.name, i.sign_wd.tripped) for i in _staged.inverters]}")
+check("⚠️ PRECONDITION: the migration really does NOT run on this store - the "
+      "marker is already there - so anything below is the guard's doing and "
+      "not the migration's",
+      not _staged.store_migration.ran)
+check("⭐ and the roster's first unit STILL comes up latched: the guard no "
+      "longer counts a latch stranded under `UNIT_A`, which is not on this "
+      "roster, as protection an operator has",
+      _staged.inverters[0].sign_wd.tripped)
+check("...and the re-armed latch is written where a machine reads it, so the "
+      "NEXT start finds it without needing the guard again",
+      _staged_store.data.get(unit_key(_C2_NAMES[0], "sign_tripped")) is True)
+
+# ⚠️ THE NEGATIVE CONTROL FOR THAT NARROWING, because "off the roster" on its
+# own was too blunt and test_inverter.py's DEV-02 restart case caught it: a
+# latch stranded under a name that is NOT `UNIT_A` is a real unit out of
+# today's config, and it MUST still count as protection.
+_other_store = MemStore({
+    "sign_tripped": True,
+    "sign_reason": "SIGN_DISAGREEMENT: B disagreed, mirrored flat",
+    unit_key("inverter-b", "sign_tripped"): True,
+    unit_key("inverter-b", "sign_reason"): "SIGN_DISAGREEMENT: B disagreed",
+    SCHEMA_KEY: SCHEMA_VERSION})
+_other, _ = controller(NAMED_OPTS, store=_other_store)
+print(f"    stranded latch under `inverter-b` -> came up tripped: "
+      f"{[(i.name, i.sign_wd.tripped) for i in _other.inverters]}")
+check("⚠️ a latch stranded under a name that is not `UNIT_A` is NOT re-armed "
+      "onto the roster: it belongs to a unit the operator has taken out of "
+      "the config, the flat key is its own mirror, and re-arming a healthy "
+      "sibling off it is the defect DEV-02 removed",
+      not any(i.sign_wd.tripped for i in _other.inverters))
+
+# ⭐ AND THE ARRANGEMENT NEITHER FIXTURE ABOVE HOLDS: **BOTH** KEYS AT ONCE.
+# ⚠️ THIS IS INSTANCE #17 OF HABIT 4 AND IT WAS FOUND IN THIS CARD'S OWN FIX.
+# The first version of the guard classified each key and then wrote ONE shared
+# `namespaced_latched` flag for both "on the roster" and "off-roster but not
+# UNIT_A". `_staged_store` above holds only an `inverter-a` latch and
+# `_other_store` below holds only an `inverter-b` one, so the flag was never
+# written twice with opposite intents in a single store - and a per-key check
+# whose keys have never disagreed WITHIN ONE STORE is a check over whichever
+# key happened to come last. Measured on that build, one added key:
+#
+#   sign_tripped + unit/inverter-a/sign_tripped   -> garage latched, repaired
+#   ...AND unit/old-shed/sign_tripped             -> ⚠️ NOTHING latched
+#
+# A site DRIVING on a state file that reads `sign_tripped: true` - the sentence
+# this card exists to make false - reached by an operator taking one unit out of
+# `inverters:` after it had tripped. "A roster is configuration and it changes"
+# is this module's own phrase, and the second inverter goes in this month.
+_both_store = MemStore({
+    "sign_tripped": True,
+    "sign_reason": "SIGN_DISAGREEMENT: SYNTHETIC FIXTURE, not measured",
+    unit_key(UNIT_A, "sign_tripped"): True,
+    unit_key(UNIT_A, "sign_reason"): "SIGN_DISAGREEMENT: SYNTHETIC FIXTURE, not measured",
+    unit_key("old-shed", "sign_tripped"): True,
+    unit_key("old-shed", "sign_reason"): "SIGN_DISAGREEMENT: old-shed, since removed",
+    SCHEMA_KEY: SCHEMA_VERSION})
+_both, _ = controller(NAMED_OPTS, store=_both_store)
+print(f"    stranded `inverter-a` AND an unrelated off-roster `old-shed` -> "
+      f"{[(i.name, i.sign_wd.tripped) for i in _both.inverters]}")
+check("⭐ A STRANDED `inverter-a` LATCH IS STILL REPAIRED WHEN AN UNRELATED "
+      "OFF-ROSTER LATCH SITS BESIDE IT. One shared flag let `old-shed` veto the "
+      "repair, and the site came up driving on a file that says it is latched",
+      _both.inverters[0].sign_wd.tripped)
+check("...and the repair still lands on the roster's first unit, not on the "
+      "removed one",
+      _both_store.data.get(unit_key(_C2_NAMES[0], "sign_tripped")) is True)
+check("⚠️ ...and the reason carried across is the FLAT one - the misdirected "
+      "latch's own - and not `old-shed`'s, which belongs to a different "
+      "physical inverter",
+      "old-shed" not in _both.inverters[0].sign_wd.reason)
+
+# ⚠️ AND THE OPERATOR MESSAGE IS ASSERTED, because review deleted it whole
+# (`if stranded:` -> `if False:`) and 28/28 stayed green. `stranded` has no
+# other consumer, so the list existed only to print a line nothing checked -
+# and the line is the entire operator-facing half of this repair: it names the
+# key that was stranded and the roster it was measured against. A repair an
+# operator cannot see is a repair they cannot confirm.
+_log_store = MemStore({
+    "sign_tripped": True,
+    "sign_reason": "SIGN_DISAGREEMENT: SYNTHETIC FIXTURE, not measured",
+    unit_key(UNIT_A, "sign_tripped"): True,
+    unit_key(UNIT_A, "sign_reason"): "SIGN_DISAGREEMENT: SYNTHETIC FIXTURE, not measured",
+    SCHEMA_KEY: SCHEMA_VERSION})
+_records = []
+_h = logging.Handler()
+_h.emit = lambda r: _records.append(r.getMessage())
+logging.getLogger("goodwe").addHandler(_h)
+try:
+    _logged, _ = controller(NAMED_OPTS, store=_log_store)
+finally:
+    logging.getLogger("goodwe").removeHandler(_h)
+_s44_lines = [m for m in _records if "SAFETY-44" in m]
+print(f"    SAFETY-44 operator lines logged: {len(_s44_lines)}")
+check("⭐ the repair SAYS SO, at ERROR, naming SAFETY-44 - deleting this line "
+      "left the whole suite green, and it is how an operator learns their "
+      "latch was re-armed rather than never lost",
+      len(_s44_lines) == 1)
+check("...and it names the STRANDED KEY, so the operator can find it in the "
+      "state file rather than being told something happened",
+      any(unit_key(UNIT_A, "sign_tripped") in m for m in _s44_lines))
+check("...and the ROSTER it was measured against, which is the half that says "
+      "WHY no machine read it",
+      any("garage" in m and "shed" in m for m in _s44_lines))
+
+# ⭐ AND `misdirected` IS MEASURED AT THE FUNCTION'S OWN LEVEL, BECAUSE IT IS
+# UNREACHABLE FROM THE CALL SITE. `Controller.__init__` passes
+# `roster_names(opts)[0]`, which `build_roster()` also names its first entry
+# from, so `unit` is a member of `roster` by construction and the refusal can
+# never fire there. Review measured that: dropping the `roster` argument from
+# `_verify_moves()` inside `migrate_unit_keys()` survives 28/28. The argument is
+# kept for the reason `_verify_moves()` gives for its own `roster=None` branch -
+# it is what a NEW caller gets by default - and a guard nothing exercises is a
+# guard nobody knows works, so it is exercised HERE rather than claimed.
+_mis_store = MemStore({"sign_tripped": True,
+                       "sign_reason": "SIGN_DISAGREEMENT: SYNTHETIC FIXTURE, not measured"})
+_mis = migrate_unit_keys(_mis_store, UNIT_A, ["garage", "shed"])
+print(f"    migrate_unit_keys(store, 'inverter-a', ['garage','shed']) -> "
+      f"ok={_mis.ok} misdirected={sorted(_mis.misdirected)}")
+check("⭐ a WRONG `unit` - one that is not on the roster it was handed - comes "
+      "back `misdirected`, which is the refusal `migrate_maint_keys()` already "
+      "had and this one did not",
+      bool(_mis.misdirected) and not _mis.ok)
+check("...and the schema marker is NOT stamped, so the migration runs again on "
+      "the next start rather than being recorded as finished - the one thing "
+      "store.py's header says must never happen",
+      _mis_store.data.get(SCHEMA_KEY) != SCHEMA_VERSION)
+check("⚠️ ...while the SAME call with a unit that IS on the roster stamps the "
+      "marker - so the refusal is caused by the name and not by the fixture",
+      migrate_unit_keys(
+          MemStore({"sign_tripped": True, "sign_reason": "x"}),
+          "garage", ["garage", "shed"]).ok)
+
 # The counterfactual, and it is the accepted baseline habit 7 asks for: the
 # same store, the same migration, one thing different - the roster shape.
 _flat_lat_store = MemStore({"sign_tripped": True,
-                            "sign_reason": "SIGN_DISAGREEMENT: measured pre-DEV-02"})
+                            "sign_reason": "SIGN_DISAGREEMENT: SYNTHETIC FIXTURE, not measured"})
 _flat_lat, _ = controller(FLAT_OPTS, store=_flat_lat_store)
 print(f"    the same store on the FLAT config -> roster "
       f"{[(i.name, i.sign_wd.tripped) for i in _flat_lat.inverters]}")

goodwe_controller/test_price_forecast.py

@@ -272,16 +272,19 @@ check("the provenance audit REFUSES a carried hour flagged non-provisional - "
       "the 'stale but plausible' point, which is SAFETY-18's frozen-but-fresh "
       "meter one layer up",
       raises(lambda: _fc._audit([_stale_copy], {}), ValueError))
+# ⚠️ `published` MAPS AN HOUR TO A TUPLE, not to a point (FCST-04 H1). An hour
+# may legitimately hold four published points - see the quarter-hourly block
+# below - so the audit takes the whole set and checks membership by identity.
 check("...and refuses a published hour that arrived as a COPY rather than as "
       "the published object, which is where a flag gets lost",
       raises(lambda: _fc._audit(
           [PricePoint(start=TODAY_PART.points[0].start,
                       eur_per_kwh=TODAY_PART.points[0].eur_per_kwh,
                       provisional=TODAY_PART.points[0].provisional)],
-          {D0: TODAY_PART.points[0]}), ValueError))
+          {D0: (TODAY_PART.points[0],)}), ValueError))
 check("...and never repairs a flag: the audit's only outcomes are silence and "
       "an exception, so a series it passed was already correct",
-      _fc._audit(list(FILLED.points), {u: TODAY_PART.points[i]
+      _fc._audit(list(FILLED.points), {u: (TODAY_PART.points[i],)
                                        for i, u in enumerate(DAY[:PUBLISHED_N])})
       is None)
 
@@ -298,6 +301,81 @@ check("a PUBLISHED point that the feed itself flagged provisional keeps that "
       and all(p.provisional for p in _eddy_filled.points[:2])
       and _eddy_filled.points[0] is _eddy.points[0])
 
+# ⚠️ AND A SUB-HOURLY FEED IS NOT DECIMATED TO ONE POINT AN HOUR (FCST-04 H1).
+# `eneco_eddy` settles per QUARTER and `_validate_raw()` accepts any
+# strictly-increasing spacing, so a published hour can hold four points. The
+# fill walks WHOLE HOURS to decide what needs carrying; that must not become a
+# rule about what a published hour may contain. Measured on FCST-04's first
+# draft, which keyed the published set `{_utc_hour(p.start): p ...}`: a
+# 96-point feed came out 15 points long and its arbitrage spread fell from
+# 0.143 to 0.014 EUR/kWh, on an ALL-FIRM, fully-published series.
+_QN = 16                                             # four hours of quarters
+_QUARTERS = PriceRead.series(
+    [PricePoint(start=brussels(D0 + timedelta(minutes=15 * n)),
+                eur_per_kwh=round(0.100000 + 0.011300 * n, 6),
+                provisional=False)
+     for n in range(_QN)],
+    PriceProduct.REALTIME, "eneco_eddy", D0)
+_QHOURS = {_fc._utc_hour(p.start) for p in _QUARTERS.points}
+check(f"the quarter-hourly fixture really is sub-hourly - {_QN} points across "
+      f"{len(_QHOURS)} hours - or every check below passes for an hourly feed "
+      f"too and grades nothing",
+      len(_QUARTERS.points) == _QN and len(_QHOURS) == _QN // 4)
+_qfill = derived(lambda: fill_from_yesterday(_QUARTERS, yesterday=YESTERDAY,
+                                             since=D0, until=D1, stamp=D0))
+_qfirm = derived(lambda: [p for p in _qfill.points if not p.provisional])
+check(f"every one of the {_QN} published points survives the fill BY IDENTITY "
+      f"({len(_qfirm)} kept). One-per-hour keying would leave {_QN // 4}, and "
+      f"the spread over the hours the feed actually published would collapse "
+      f"with them",
+      len(_qfirm) == _QN
+      and all(any(p is q for q in _QUARTERS.points) for p in _qfirm))
+check(f"...and the {len(DAY) - len(_QHOURS)} whole hours it published NOTHING "
+      f"for are carried, ONE point each: a carried hour is hourly whatever the "
+      f"feed's spacing is, because yesterday's profile is only known per "
+      f"wall-clock hour",
+      _qfill.kind == "series"
+      and len([p for p in _qfill.points if p.provisional])
+      == len(DAY) - len(_QHOURS))
+check("...and the filled series is still ordered by instant across the two "
+      "kinds, so `at()` and `window()` are not reading a shuffled list",
+      _qfill.kind == "series"
+      and [p.start.astimezone(UTC) for p in _qfill.points]
+      == sorted(p.start.astimezone(UTC) for p in _qfill.points))
+
+_PUB_Q = _fc._published_by_hour(_QUARTERS)
+# ⚠️ `derived`, NOT A RAW CALL. Under the decimating mutation this check
+# exists for, `_audit` RAISES here - and a harness that dies on the mutation it
+# is grading reports a traceback instead of a FAIL, which MUTATION.md forbids.
+check("the audit ACCEPTS four published points inside one hour, which is the "
+      "case the repeated-hour COUNT it replaced could not express",
+      derived(lambda: _fc._audit(list(_QUARTERS.points), _PUB_Q)) is None)
+check("...and still REFUSES a repeated CARRIED hour, which is the DST "
+      "mispricing that count existed to catch",
+      raises(lambda: _fc._audit([_fc._carried(D0, 0.11),
+                                 _fc._carried(D0, 0.12)], {}), ValueError))
+check("...and refuses the SAME published point emitted twice - the provider's "
+      "points are strictly increasing, so a repeat is never a second print",
+      raises(lambda: _fc._audit([_QUARTERS.points[0], _QUARTERS.points[0]],
+                                _PUB_Q), ValueError))
+check("...and refuses a CARRIED point standing in an hour the feed DID "
+      "publish, which the old count never looked at",
+      raises(lambda: _fc._audit([_fc._carried(D0, 0.11)], _PUB_Q), ValueError))
+
+# ⚠️ THE HORIZON IS WHOLE HOURS AT BOTH ENDS (FCST-04 L8). `since` is floored
+# and `until` was not, so a 48 h request made at any instant off the hour came
+# back 49 hours long. Graded at an OFF-THE-HOUR instant, because on the hour
+# the two implementations agree and the check would grade nothing.
+_off = D0 + timedelta(hours=8, minutes=17, seconds=43)
+for _h in (1, 12, 48):
+    _n = derived(lambda h=_h: len(fill_from_yesterday(
+        TODAY_PART, yesterday=YESTERDAY, since=_off,
+        until=_off + timedelta(hours=h), stamp=_off).points))
+    check(f"a {_h} h horizon asked for at {_off.isoformat()} - 17 min 43 s "
+          f"past the hour, the shape a running controller always has - is "
+          f"{_h} points long, not {_h + 1}",
+          _n == _h)
+
 # The structural half: the constructor has nothing to pass, and the file is
 # scanned so the pass-through idiom cannot come back looking ordinary.
 check("_carried() has NO `provisional` parameter, so a caller has nothing to "

goodwe_controller/test_rehearse.py

@@ -411,6 +411,94 @@ check("...and `phase` is NOT among them, because its value 'idle' IS the "
       "phase" not in _m9_vanished)
 shutil.rmtree(Path(_m9).parent, ignore_errors=True)
 
+# ⭐ `M12` IS BACK, AND THE CLAIM THAT KILLED IT WAS WRONG.
+#
+# M12 is SAFETY-44's end-to-end control for the off-roster narrowing: a mutant
+# makes one ROSTER unit's latch key vanish while a sibling holds the same
+# value, and it must go red when the narrowing is removed. INSTR-01's first
+# draft DELETED it, on the claim that the provenance clause made it
+# unrestorable and that "NO FIXTURE CAN RESTORE IT, measured both ways".
+#
+# ⚠️ TWO MEASUREMENTS ARE NOT AN IMPOSSIBILITY PROOF, AND THIS ONE WAS FALSE.
+# Both arrangements I measured were SAME-STEP shaped, and the structural
+# argument - `run()` builds both snapshots from one state file, so "already
+# latched" and "made by this transition" are incompatible - is TRUE OF
+# SAME-STEP AND FALSE OF STAGED. `snapshot_over()` starts the after-leg over
+# the file the BEFORE-leg wrote, so on the staged leg a transition-made
+# destination is available and the two questions stop being incompatible.
+# Review found the third arrangement I had generalised past.
+#
+# HOW IT WORKS. The fixture is `state-legacy.json` plus a second roster unit
+# already latched. The mutant makes `shed` POP its own latch key and come up
+# untripped - a truer SAFETY-02 loss than the original, which left `tripped`
+# True in memory. On the staged leg, losing shed's latch makes
+# `_grade_store_migration()` fall through `on_roster_latched` and RE-ARM
+# `unit/garage/sign_tripped`, which is absent from `before.data` - so the
+# destination is transition-made and C7 lets it through. The off-roster
+# `inverter-a` litter is present in BOTH snapshots on this leg, so it never
+# vanishes and never claims the destination, and C6 stays out of the way.
+#
+# ⚠️ AND WHAT ACTUALLY BROKE WAS THE PRECONDITION, NOT THE CONTROL. M12's
+# `exit == EXIT_OK` baseline does not survive a legacy-shaped fixture. That
+# precondition is the one SAFETY-44's own commit called "belt-and-braces,
+# load-bearing only if the exit-0 requirement is ever relaxed", saying that
+# what closed the first draft's gap is `_m12_new` BEING A SET DIFFERENCE. A
+# stable dirty baseline is fine for a set difference. So the control was
+# deleted on the strength of a precondition the same commit had already
+# characterised as not load-bearing - which is a worse mistake than the
+# original inert check, because it removed coverage rather than failing to add
+# it.
+_M12_OLD = 'tripped=bool(data.get(self.key("sign_tripped"), False)),'
+# ⚠️ THE MUTANT POPS **AND COMES UP UNTRIPPED**, which is the whole point and
+# which the first draft got wrong: `data.pop(k, False)` RETURNS the value, so
+# shed stayed latched in memory, `_grade_store_migration()` saw
+# `on_roster_latched` and never re-armed garage - no transition-made
+# destination, and the finding was reported whether or not C5 existed. The
+# control looked restored and discriminated nothing. `and False` is the
+# difference between "the key is gone" and "the LATCH is gone", and only the
+# second reaches the re-arm this arrangement needs.
+_M12_NEW = ('tripped=bool(data.pop(self.key("sign_tripped"), False) and False'
+            + chr(10) + '                     if self.name == "shed" else'
+            + chr(10) + '                     data.get(self.key("sign_tripped"), False)),')
+
+
+def m12_findings(tree):
+    """The finding SET of a staged-leg run over the legacy+shed fixture."""
+    code, out = run(Path(tree), "state-legacy-plus-shed.json", "roster.yaml",
+                    "--paths", "staged")
+    return code, set(re.findall(r"⚠️ ([A-Z ]+): (\S+)", out)), out
+
+
+_m12 = mutant_tree([("app/inverter.py", _M12_OLD, _M12_NEW)])
+_m12_clean_code, _m12_clean, _ = m12_findings(HERE)
+_m12_code, _m12_mut, _ = m12_findings(Path(_m12))
+_m12_new = _m12_mut - _m12_clean
+print(f"      staged leg, legacy+shed: shipped exit {_m12_clean_code}, "
+      f"one roster unit's latch popped -> exit {_m12_code}")
+# ⚠️ THE PRINTED SET IS LOSSIER THAN IT LOOKS: the regex captures the first
+# TOKEN of each finding's text, so two findings of one kind collapse into one
+# tuple. Harmless here - the difference is one-directional and the pair M12
+# asserts on is exact - but do not read this line as an inventory.
+print(f"      findings the mutation ADDS (first token only): {sorted(_m12_new)}")
+check("⚠️ PRECONDITION: the baseline is STABLE and does not already carry the "
+      "finding this mutation exists to produce. It is NOT clean - a legacy "
+      "fixture never is - and the SET DIFFERENCE is what makes that fine, "
+      "which is the sentence the deletion should have read before acting on it",
+      not any(k == "unit/shed/sign_tripped" for _, k in _m12_clean))
+# ⚠️ AND IT MATCHES THE **KIND** AS WELL AS THE KEY, which SAFETY-44's original
+# did not. Review measured it: renaming the finding kind in `diff()` from
+# "VANISHED STORE KEY" to "GONE STORE KEY" left M12 GREEN. A vanished latch
+# quietly downgraded to a softer heading is exactly the shape part 3 requires
+# every mutation to be graded against - "the SPECIFIC finding it should produce"
+# - and this file was not holding itself to its own rule.
+check("⭐ M12 RESTORED: a ROSTER unit's latch key that vanishes is a "
+      "VANISHED STORE KEY finding even though a sibling holds True - and this "
+      "is the STAGED leg, where `snapshot_over()` supplies a transition-made "
+      "destination, so the provenance clause does not foreclose the narrowing",
+      ("VANISHED STORE KEY", "unit/shed/sign_tripped") in _m12_new)
+shutil.rmtree(Path(_m12).parent, ignore_errors=True)
+
+
 # ⚠️ AND THE INPUT FILE IS NEVER WRITTEN. The owner runs this against a copy of
 # a live state file; a tool that edited it would be a tool that had to be
 # trusted rather than one that cannot do harm.
@@ -587,33 +675,32 @@ shutil.rmtree(Path(_tree2).parent, ignore_errors=True)
 
 # --------------------------------------------------------------------------- #
 print()
-print("5. SAFETY-44: a pre-DEV-02 flat store meeting a DECLARED ROSTER, which "
+print("5. SAFETY-44: a pre-DEV-02 flat store meeting a DECLARED ROSTER - "
-      "is the path nobody had established either way")
+      "FIXED, with each half of the fix as its own negative control")
 # --------------------------------------------------------------------------- #
-# The question on the card: `migrate_unit_keys(store, UNIT_A)` takes a hardcoded
+# The question on the card: `migrate_unit_keys(store, UNIT_A)` took a hardcoded
-# constant and has no `misdirected` guard, while `migrate_maint_keys(store,
+# constant and had no `misdirected` guard, while `migrate_maint_keys(store,
-# unit, roster)` takes the roster and does. Is that asymmetry safe?
+# unit, roster)` takes the roster and does. That asymmetry was NOT safe, and
+# this part used to assert the defect. It now asserts the FIX.
 #
-# ⚠️ MEASURED, NOT ARGUED. The two checks below are the answer, and they are
+# ⚠️ THE FIX IS TWO EDITS AND THEY DO DIFFERENT JOBS, WHICH IS THE WHOLE REASON
-# written as REQUIREMENTS so that a fix to `migrate_unit_keys` turns them red
+# THIS PART IS SHAPED THE WAY IT IS. Measured, per leg, by reverting each edit
-# and this file has to be updated deliberately rather than drifting.
+# on its own (5b and 5c below):
+#
+#                              SAME-STEP leg            STAGED leg
+#   both edits (shipped)       clean                    latch armed, litter
+#   guard reverted             latch armed              ⚠️ DISARMED
+#   call site reverted         latch armed, litter      latch armed, litter
+#
+# So the GUARD carries the safety and the CALL SITE carries the hygiene. Saying
+# that plainly matters more than it looks: a reader who assumes the roster-aware
+# migration is what re-arms the latch would delete the guard as redundant during
+# a tidy-up and take the STAGED column with it - and STAGED is the path
+# "upgrade now, declare the roster later" produces, which is the path an
+# operator actually takes.
 code44, out44 = run(HERE, "state-legacy.json", "roster.yaml")
-print(f"      flat store + roster ['garage','shed'] -> exit {code44}")
-check("⚠️ SAFETY-44 IS A DEFECT AGAIN: a store that ran pre-DEV-02 flat and "
-      "declares a multi-inverter roster comes up with its SAFETY-02 latch "
-      "DISARMED - the file says `sign_tripped: true` and not one inverter is "
-      "latched",
-      code44 == RR.EXIT_FINDING and "LATCH CAME UP DISARMED" in out44)
-check("...and the harness names the two latch keys SAFETY-44 asks about, by "
-      "the namespace they were stranded in",
-      "unit/inverter-a/sign_tripped" in out44
-      and "unit/inverter-a/sign_reason" in out44)
-check("...and the mechanism is visible in the report: the keys are stranded "
-      "under `inverter-a`, which is not on the roster, so no machine reads them",
-      "STRANDED STORE KEY" in out44 and "['garage', 'shed']" in out44)
-# ⚠️ PER LEG, NOT A COUNT OVER THE WHOLE REPORT. See `legs()` for the three
-# builds this distinction was measured on and for what the count missed.
 _L = legs(out44)
+print(f"      flat store + roster ['garage','shed'] -> exit {code44}")
 print(f"      legs in the report: {sorted(_L)}")
 for _leg in ("STAGED", "SAME-STEP"):
     print(f"      LEG {_leg}: "
@@ -622,77 +709,348 @@ check("the report is split into legs this check can grade SEPARATELY - the "
       "tool prints a `LEG <id>` marker, because counting a finding's text over "
       "the whole report cannot tell one red leg from two",
       set(_L) == {"STAGED", "SAME-STEP"})
-check("⚠️ SAME-STEP is disarmed: the roster is declared in the SAME step as "
+check("⭐ SAFETY-44 IS FIXED ON BOTH PATHS: a store that ran pre-DEV-02 flat "
-      "the upgrade, the migration runs and misdirects the latch to "
+      "and declares a multi-inverter roster comes up LATCHED - neither leg "
-      "`inverter-a`",
+      "reports a disarmed guard",
-      "LATCH CAME UP DISARMED" in _L.get("SAME-STEP", ""))
+      "LATCH CAME UP DISARMED" not in out44)
-check("⚠️ AND IT IS NOT THE SAME-STEP PATH ALONE - the STAGED leg reaches the "
+check("...and the latch is under a name THE ROSTER READS, which is the whole "
-      "same disarmed latch by a DIFFERENT route: the flat start stamps "
+      "of the claim - `garage` is on the roster and `inverter-a` is not",
-      "`schema_version`, so the roster start's migration takes its early "
+      all("after : which units came up latched  : ['garage']" in v
-      "return and the latch never moves at all",
+          for v in _L.values()))
-      "LATCH CAME UP DISARMED" in _L.get("STAGED", ""))
+check("⚠️ the SAME-STEP leg is now CLEAN OUTRIGHT: the migration writes the "
-
+      "latch straight into the roster's first namespace, so there is no "
-# ⚠️ AND THE CONTRAST, WHICH IS WHAT STOPS THE CHECK ABOVE BEING VACUOUS. The
+      "stranded copy left behind and nothing for an operator to read past",
-# SAME state file onto a roster whose first entry IS `inverter-a` comes up
+      "none in LEG SAME-STEP" in _L.get("SAME-STEP", ""))
-# LATCHED. The two runs differ in one thing - the first roster name - so the
+check("⚠️ ...while the STAGED leg still reports the two STRANDED keys, and "
-# finding is attributable to it and to nothing else.
+      "that is REPORTED not hidden: its flat start stamped `schema_version` "
-code_ok, out_ok = run(HERE, "state-legacy.json", "roster-inverter-a.yaml")
+      "before the roster existed, so the migration takes its early return and "
+      "the old copies stay in the file with nothing reading them. The latch is "
+      "armed anyway - by the guard - and the litter is true",
+      "STRANDED STORE KEY" in _L.get("STAGED", "")
+      and "unit/inverter-a/sign_tripped" in _L.get("STAGED", ""))
+check("...and the run as a whole is a FINDING rather than silence, because "
+      "keys nothing reads are still keys nothing reads",
+      code44 == RR.EXIT_FINDING)
 check("...and no leg's text has swallowed the CLOSING SUMMARY, which repeats "
       "every finding from every leg - the failure that made the last leg read "
       "red whenever any leg was",
       not any("FINDING(S) - this transition is not clean" in v
               for v in _L.values()))
+# ⚠️ THIS BLOCK USED TO SAY THOSE HOLES WERE KNOWN AND NOT FIXED, AND IT IS
+# NOW STALE IN THE OTHER DIRECTION - INSTR-01 fixed them, and left the
+# paragraph saying "BOTH ARE REVERTED OUT OF THIS CARD, because THIS SUITE
+# CANNOT MEASURE EITHER ONE" describing a tree that no longer exists. Review
+# found it. A comment that outlives its subject is the same defect as a
+# citation that outlives its check.
+#
+# WHERE EACH ONE NOW LIVES, and every clause of `moved_to` has a row in 5e:
+#
+#   INJECTIVITY  (C6)  R5, and removing the clause flips exactly R5
+#   PROVENANCE   (C7)  R3, likewise
+#   SAME VALUE   (C3)  R4
+#   SAME BARE KEY(C2)  R7 - which had NO row until review deleted the clause
+#                      and the whole 28-file suite stayed green
+#   MACHINE-READ (C1)  R6
+#   OFF-ROSTER   (C5)  R2, and M12 end-to-end on the staged leg
+#   PREFIX GATE  (C4)  NO 5e ROW, deliberately - `vanished_unit is not None`
+#                      is reached end-to-end by part 3's M9, and a synthetic
+#                      row would duplicate that rather than add separability.
+#                      Listed because C5 lives in the same `if` and omitting
+#                      one guard while naming the other reads as an oversight.
+#
+# ⚠️ ONE HOLE IS STILL OPEN AND IS **UNMEASURED**, stated so nobody reads
+# `sorted()` as guarded: ATTRIBUTION. Which vanished key gets a destination is
+# decided by `sorted()` order, so on a build renaming `inverter-b` -> `garage`
+# while DELETING `inverter-a`, the deleted key sorts first and takes it - the
+# report names the DELETED key as migrated and the one that really moved as
+# VANISHED. Review measured that replacing `sorted(` with `list(` leaves the
+# suite green: every 5e case has at most one candidate destination, so no row
+# can see ordering. The run is still exit 1, so this is a WRONG SENTENCE rather
+# than a hidden loss - an operator chasing the named key looks at the wrong
+# inverter. Fixing it needs the destination's provenance rather than
+# first-come, which is more than a rename diff currently knows.
+check("⚠️ and the key that MOVED is not reported as lost: the before-snapshot "
+      "holds `unit/inverter-a/sign_tripped = True` and the after-snapshot "
+      "holds it under `garage`, three lines apart in the same report. A "
+      "VANISHED finding there is the harmless-case alarm CONTROL-C exists to "
+      "prevent",
+      "migrated  unit/inverter-a/sign_tripped = True -> "
+      "unit/garage/sign_tripped" in out44
+      and "VANISHED STORE KEY" not in out44)
 
 # --------------------------------------------------------------------------- #
 print()
-print("5b. THE SPLITTER'S POSITIVE CONTROL: a build in which exactly ONE leg "
+print("5b. NEGATIVE CONTROL, AND THE SPLITTER'S POSITIVE ONE: revert THE "
-      "is clean")
+      "GUARD, and exactly one leg goes red")
 # --------------------------------------------------------------------------- #
 # ⚠️ A PER-LEG CHECK THAT HAS NEVER SEEN THE LEGS DISAGREE IS A COUNT WITH
-# EXTRA STEPS. Every fixture above has both legs red, so nothing so far
+# EXTRA STEPS, and MUTATION.md's extension says one that has seen them disagree
-# separates "reads each leg" from "reads the whole report twice". This part
+# in a single arrangement is a total over that arrangement. This build is the
-# builds the one case that does: `migrate_unit_keys()` handed the roster's own
+# one that makes them disagree, and it is a negative control for part 5 at the
-# first name instead of the hardcoded `UNIT_A`.
+# same time: put back the clause that counted ANY `unit/*/sign_tripped` as
-#
+# protection, including one under a name no unit answers to.
-# ⚠️ AND WHAT IT MEASURES IS ALSO THE ANSWER TO "IS THAT THE FIX". It is NOT.
+# ⚠️ WHAT THIS CONTROL PINS IS THE SHIPPED SPELLING, NOT THE RULE, and review
-# It repairs the SAME-STEP path only. The STAGED path is untouched, because
+# is owed that distinction. `mutant_tree()` asserts its target exists - rightly,
-# there the flat start stamps `schema_version = 1` and the roster start's
+# because a mutation that did not happen yields a fabricated result - but the
-# migration takes its `from_version >= SCHEMA_VERSION` early return before the
+# consequence is that EDITING the guard's line makes this file red at the
-# name it would be handed matters at all. A fix that stops at this line would
+# ANCHOR before any behaviour is measured. Demonstrated: rewriting the same
-# close the half an operator is least likely to take and leave the half that
+# semantics as `on_roster = set()` leaves the anchor intact and IS caught, by
-# "upgrade first, declare the roster later" produces.
+# M4's control; rewriting the line itself is caught by the anchor, which looks
-_one_leg = mutant_tree([(
+# identical from the exit code and proves much less. Read 5b and 5c as controls
+# over this text, and the behavioural coverage as living in test_maintenance.py
+# section 13 and test_inverter.py, which construct stores rather than strings.
+_no_guard = mutant_tree([(
     "app/main.py",
-    "        self.store_migration = migrate_unit_keys(store, UNIT_A)",
+    "            if unit in on_roster:",
-    "        self.store_migration = migrate_unit_keys(store, "
+    "            if True:  # MUTANT: any namespaced latch is protection")])
-    "roster_names(opts)[0])")])
+_ng_code, _ng_out = run(Path(_no_guard), "state-legacy.json", "roster.yaml")
-_ol_code, _ol_out = run(Path(_one_leg), "state-legacy.json", "roster.yaml")
+_NG = legs(_ng_out)
-_OL = legs(_ol_out)
 for _leg in ("STAGED", "SAME-STEP"):
     print(f"      LEG {_leg}: "
-          f"{'DISARMED' if 'LATCH CAME UP DISARMED' in _OL.get(_leg, '') else 'clean'}")
+          f"{'DISARMED' if 'LATCH CAME UP DISARMED' in _NG.get(_leg, '') else 'clean'}")
-check("⭐ with `migrate_unit_keys()` handed the roster's own first name, the "
+check("⭐ with the off-roster clause reverted the STAGED leg comes up "
-      "SAME-STEP leg comes up CLEAN - so the splitter really does read the "
+      "DISARMED - so the guard's roster test is load-bearing, and it is the "
-      "legs separately, and a check that only counted would have missed this",
+      "half of the fix that repairs an install already stamped by the shipped "
-      "LATCH CAME UP DISARMED" not in _OL["SAME-STEP"])
+      "version",
-check("⚠️ ...while the STAGED leg is STILL DISARMED on the same build: that "
+      "LATCH CAME UP DISARMED" in _NG.get("STAGED", ""))
-      "line is not the whole fix, because the staged path never reaches it - "
+check("⚠️ ...while the SAME-STEP leg stays ARMED on the very same build - the "
-      "the first start stamps `schema_version` and the second start's "
+      "legs DISAGREE, so the splitter really does read them separately and a "
-      "migration returns early",
+      "check that only counted findings would have missed this",
-      "LATCH CAME UP DISARMED" in _OL["STAGED"])
+      "LATCH CAME UP DISARMED" not in _NG.get("SAME-STEP", ""))
-check("...and the run as a whole is still a finding, so nobody reads this "
+check("...and the run is a finding, so the partial build is never read as "
-      "partial fix as done",
+      "clean",
-      _ol_code == RR.EXIT_FINDING)
+      _ng_code == RR.EXIT_FINDING)
-shutil.rmtree(Path(_one_leg).parent, ignore_errors=True)
+shutil.rmtree(Path(_no_guard).parent, ignore_errors=True)
 
+# --------------------------------------------------------------------------- #
 print()
-print("5c. back to the shipped code")
+print("5c. NEGATIVE CONTROL: revert THE CALL SITE, and the litter comes back "
+      "without the latch going out")
+# --------------------------------------------------------------------------- #
+# ⚠️ THIS IS THE CONTROL THAT KEEPS 5b HONEST ABOUT WHAT IT PROVED. 5b shows
+# the guard carries the latch; on its own that is an argument for deleting the
+# roster-aware migration as decoration. This build is the measurement instead:
+# hand `migrate_unit_keys()` the hardcoded `UNIT_A` again, with the guard left
+# fixed. The latch stays armed - the guard catches it - and the SAME-STEP leg
+# gains the two stranded keys it does not have on the shipped code. The
+# migration fix buys a store with nothing dead in it, and buys the
+# `misdirected` refusal that stops a WRONG marker being stamped; it does not
+# buy the latch. Both edits stay.
+_CALL_NOW = ("        self.store_migration = migrate_unit_keys(" + chr(10) +
+             "            store, _roster_names[0], _roster_names)")
+_old_call = mutant_tree([(
+    "app/main.py", _CALL_NOW,
+    "        self.store_migration = migrate_unit_keys(store, UNIT_A)")])
+_oc_code, _oc_out = run(Path(_old_call), "state-legacy.json", "roster.yaml")
+_OC = legs(_oc_out)
+for _leg in ("STAGED", "SAME-STEP"):
+    print(f"      LEG {_leg}: "
+          f"{'DISARMED' if 'LATCH CAME UP DISARMED' in _OC.get(_leg, '') else 'clean'}")
+check("⚠️ with `UNIT_A` handed back to the migration the latch is STILL "
+      "armed on both legs - the guard is what re-arms it, and saying so is "
+      "the difference between this fix and a story about it",
+      "LATCH CAME UP DISARMED" not in _oc_out)
+check("⭐ ...but the SAME-STEP leg is no longer clean: the two SAFETY-02 keys "
+      "are written under `inverter-a` on a roster of ['garage', 'shed'] and "
+      "nothing reads them - which is the state the shipped code does not "
+      "produce",
+      "STRANDED STORE KEY" in _OC.get("SAME-STEP", "")
+      and "none in LEG SAME-STEP" not in _OC.get("SAME-STEP", ""))
+shutil.rmtree(Path(_old_call).parent, ignore_errors=True)
+
+# --------------------------------------------------------------------------- #
+print()
+print("5d. THE CONTRAST: the same file onto a roster that keeps the name")
+# --------------------------------------------------------------------------- #
+# ⚠️ AND THE CONTRAST, WHICH IS WHAT STOPS EVERY CHECK ABOVE BEING VACUOUS. The
+# SAME state file onto a roster whose first entry IS `inverter-a` comes up
+# LATCHED AND CLEAN. The two runs differ in one thing - the first roster name -
+# so a finding above is attributable to it and to nothing else.
+code_ok, out_ok = run(HERE, "state-legacy.json", "roster-inverter-a.yaml")
 check("the SAME state file onto a roster whose first entry IS `inverter-a` "
-      "comes up latched and clean - so the finding above is caused by the "
+      "comes up latched and clean - so anything part 5 reports is caused by "
-      "roster NAME and not by the fixture being tripped",
+      "the roster NAME and not by the fixture being tripped",
       code_ok == RR.EXIT_OK and "LATCH CAME UP DISARMED" not in out_ok)
 
 
+# --------------------------------------------------------------------------- #
+print()
+print("5e. INSTR-01: `diff()`'s suppression rule, ONE FIXTURE PER CLAUSE")
+# --------------------------------------------------------------------------- #
+# ⚠️ THIS SECTION EXISTS BECAUSE SAFETY-44 PRODUCED THREE INERT CONTROLS FOR
+# THIS ONE RULE, EACH INERT DIFFERENTLY:
+#
+#   1. a check over part 5's real destinations passed with the whole mechanism
+#      deleted - its two destinations are `sign_reason` and `sign_tripped`,
+#      DIFFERENT bare keys, which can never contend;
+#   2. a dedicated end-to-end fixture discriminated nothing - both snapshots
+#      read ONE state file, so nothing vanishes and there are no migrated lines
+#      with the clause or without it;
+#   3. rebuilding M12's fixture to reach a new clause DISARMED M12 for an older
+#      one, and all three clause-removals went green at once.
+#
+# ⭐ (3) IS THE STRUCTURAL FINDING AND IT IS WHY THIS SECTION IS SHAPED THIS WAY.
+# `moved_to` is ONE comprehension carrying FIVE conditions with five different
+# reasons to exist, and an END-TO-END fixture cannot separate them: both
+# snapshots come from one state file, so the arrangement that reaches clause N
+# forecloses clause M. Rebuilding the fixture to reach one moves the others.
+#
+# So the rule is graded at the level it is written at - `diff()` on constructed
+# Snapshots - with ONE CASE PER CLAUSE. Nothing here is a fiction: the inputs
+# are the same three fields `diff()` reads (`data`, `machine_read`, `units`),
+# and the end-to-end controls above - M12 on the STAGED leg, and part 5 -
+# still grade the same rule through a real start. This is the separability
+# those cannot have, not a replacement for them.
+CLAUSE_CASES = {
+    # name: (units, machine_read, before, after)
+    "R1-rename-legit": (
+        ["garage"], ["unit/garage/sign_tripped"],
+        {"unit/old/sign_tripped": True}, {"unit/garage/sign_tripped": True}),
+    "R2-narrowing": (
+        ["garage", "shed"], ["unit/garage/sign_tripped", "unit/shed/sign_tripped"],
+        {"unit/shed/sign_tripped": True}, {"unit/garage/sign_tripped": True}),
+    "R3-provenance": (
+        ["garage"], ["unit/garage/sign_tripped"],
+        {"unit/old/sign_tripped": True, "unit/garage/sign_tripped": True},
+        {"unit/garage/sign_tripped": True}),
+    "R4-value": (
+        ["garage"], ["unit/garage/sign_reason"],
+        {"unit/old/sign_reason": "X-unique"},
+        {"unit/garage/sign_reason": "Y-different"}),
+    "R5-injectivity": (
+        ["garage"], ["unit/garage/sign_tripped"],
+        {"unit/old-a/sign_tripped": True, "unit/old-b/sign_tripped": True},
+        {"unit/garage/sign_tripped": True}),
+    "R6-machine-read": (
+        ["garage"], [],
+        {"unit/old/sign_tripped": True}, {"unit/garage/sign_tripped": True}),
+    # ⚠️ R7 EXISTS BECAUSE THE BARE-KEY MATCH HAD NO ROW AT ALL, and review
+    # deleted it and left the whole 28-file suite GREEN. The rule's own comment
+    # says "THE TEST IS NOT 'the name appears somewhere'. It is: the SAME bare
+    # key" - and nothing measured that sentence. It is load-bearing: a vanished
+    # SAFETY-02 `sign_tripped` was suppressed by a SAFETY-42
+    # `delivery_tripped` on a roster unit, i.e. by a DIFFERENT FAILSAFE's key.
+    # `unit/*/delivery_tripped` is machine-read, so this is reachable on any
+    # real two-latch store rather than a contrivance.
+    "R7-bare-key": (
+        ["garage"], ["unit/garage/delivery_tripped"],
+        {"unit/old/sign_tripped": True},
+        {"unit/garage/delivery_tripped": True}),
+}
+# What the SHIPPED rule must answer. `migrated` is the suppression firing.
+CLAUSE_EXPECT = {
+    "R1-rename-legit": ([], ["unit/old/sign_tripped"]),
+    "R2-narrowing":    (["unit/shed/sign_tripped"], []),
+    "R3-provenance":   (["unit/old/sign_tripped"], []),
+    "R4-value":        (["unit/old/sign_reason"], []),
+    "R5-injectivity":  (["unit/old-b/sign_tripped"], ["unit/old-a/sign_tripped"]),
+    "R6-machine-read": (["unit/old/sign_tripped"], []),
+    "R7-bare-key":     (["unit/old/sign_tripped"], []),
+}
+# ⚠️ THE DRIVER **IMPORTS** THE TREE UNDER TEST AND THE TABLE STAYS HERE, so
+# expectation and implementation sit on opposite sides of the subprocess and
+# a mutation to the tool cannot also move the answer it is graded against.
+# (It is WRITTEN to a tempdir - see `clause_table()`. The first draft of this
+# sentence said "written into the tree", which is the read-only-CI bug the
+# same commit says it fixed, stated as if it were the design.)
+CLAUSE_DRIVER = """
+import json, sys
+import rehearse_roster as RR
+spec = json.load(sys.stdin)
+out = {}
+for name, case in spec.items():
+    units, mread, before, after = case
+    b = object.__new__(RR.Snapshot); a = object.__new__(RR.Snapshot)
+    for snap, data in ((b, before), (a, after)):
+        snap.label = name
+        snap.data = dict(data)
+        snap.units = list(units)
+        snap.machine_read = set(mread)
+        snap.entities = {}
+        snap.latched = {u: False for u in units}
+        snap.latch_reason = {u: "" for u in units}
+        snap.flat_tripped = False
+        snap.history = {}
+        snap.read = set()
+        snap.stranded_at_default = []
+        snap.vanished_at_default = []
+        snap.vanished_but_migrated = []
+    f = RR.diff(b, a)
+    out[name] = [
+        sorted(x.text.split(" = ")[0] for x in f
+               if x.kind == "VANISHED STORE KEY"),
+        sorted(t.split(" = ")[0] for t in a.vanished_but_migrated),
+    ]
+print(json.dumps(out))
+"""
+
+
+def clause_table(tree) -> dict:
+    """Run CLAUSE_CASES through `diff()` in `tree`, as the tool would see it."""
+    # ⚠️ THE DRIVER GOES IN A TEMPDIR, NOT IN THE TREE. `checks / unit` mounts
+    # the checkout READ-ONLY, so writing beside the tool works on a dev box and
+    # is `OSError: Read-only file system` in CI - a difference that would have
+    # turned this section red on every PR and green for whoever wrote it.
+    tools = Path(tree) / "tools"
+    tmp = tempfile.mkdtemp(prefix="clause-drv-")
+    drv = Path(tmp) / "_clause_driver.py"
+    drv.write_text(CLAUSE_DRIVER, encoding="utf-8")
+    proc = subprocess.run(
+        [sys.executable, str(drv)],
+        input=json.dumps(CLAUSE_CASES), capture_output=True, text=True,
+        cwd=tmp,
+        env={**os.environ, "PYTHONDONTWRITEBYTECODE": "1",
+             "PYTHONPATH": f"{tools}{os.pathsep}{Path(tree)}"})
+    shutil.rmtree(tmp, ignore_errors=True)
+    assert proc.returncode == 0, (
+        "the clause driver did not run, so every row below would be "
+        f"fabricated:\n{proc.stdout}\n{proc.stderr}")
+    return {k: (v[0], v[1]) for k, v in json.loads(proc.stdout).items()}
+
+
+_ct = clause_table(HERE)
+for _name in sorted(CLAUSE_CASES):
+    _got, _want = _ct[_name], CLAUSE_EXPECT[_name]
+    print(f"      {_name:<18} vanished={_got[0]} migrated={_got[1]}")
+    check(f"{_name}: the shipped rule answers as specified", list(_got) == [list(_want[0]), list(_want[1])])
+check("⚠️ ...and the LEGITIMATE case is still suppressed - a rule that reports "
+      "every rename is a rule an operator turns off, which is the failure "
+      "CONTROL-C exists to prevent",
+      _ct["R1-rename-legit"][1] == ["unit/old/sign_tripped"])
+
+# ⭐ AND EACH CLAUSE REMOVAL MUST FLIP **EXACTLY ITS OWN ROW**. That second half
+# is the acceptance criterion this card was filed with: a removal that flips
+# nothing is an unmeasured clause, and a removal that flips someone else's row
+# means the cases are not separable after all - which is (3) above, caught.
+CLAUSE_MUTATIONS = [
+    ("C2 same bare key", "R7-bare-key",
+     '            if k.rsplit("/", 1)[-1] == bare and after.data.get(k) == value',
+     "            if True and after.data.get(k) == value"),
+    ("C1 machine_read", "R6-machine-read",
+     "            k for k in after.machine_read",
+     "            k for k in after.data"),
+    ("C3 same value", "R4-value",
+     " and after.data.get(k) == value\n", "\n"),
+    ("C5 off-roster", "R2-narrowing",
+     "        if vanished_unit is not None and vanished_unit not in after.units \\\n"
+     "                and moved_to:",
+     "        if vanished_unit is not None and moved_to:"),
+    ("C6 injectivity", "R5-injectivity",
+     " and k not in claimed)", ")"),
+    ("C7 provenance", "R3-provenance",
+     "            and before.data.get(k) != value", "            and True"),
+]
+for _label, _owns, _old, _new in CLAUSE_MUTATIONS:
+    _t = mutant_tree([("tools/rehearse_roster.py", _old, _new)])
+    _mt = clause_table(_t)
+    _flipped = sorted(n for n in CLAUSE_CASES if _mt[n] != _ct[n])
+    print(f"      {_label:<16} removed -> rows that changed: {_flipped}")
+    check(f"⭐ removing {_label} flips {_owns} - the clause is load-bearing and "
+          f"this row is what measures it",
+          _flipped == [_owns])
+    shutil.rmtree(Path(_t).parent, ignore_errors=True)
+
+
 # --------------------------------------------------------------------------- #
 print()
 print("6. THE REVERSE DIRECTION: the retreat, and the return from it")

goodwe_controller/test_static_tariff.py

@@ -69,6 +69,7 @@ from app.price import (
     Absence, PricePoint, PriceProduct, PriceRead, arbitrage_allowed, brussels,
     plan_is_provisional, required_spread, uncertainty_of,
 )
+from app.price_history import NoHistory
 from app.static_tariff import (
     MEAN_WINDOW_DAYS, ProfileInvalid, StaticProfile, TariffPlan,
     parse_static_profile, resolve_tariff, static_plan, static_status,
@@ -746,7 +747,8 @@ _cfg = opts(TWO_PERIOD, price_provider="generic_dayahead",
             price_feed_url="https://api.energy-charts.info/price?bzn=BE",
             price_timeout_s=1, price_markup_eur_kwh=0.03,
             price_taxes_eur_kwh=0.06)
-_fb = run(resolve_tariff(_cfg, THU, THU + timedelta(days=1), transport=_dead))
+_fb = run(resolve_tariff(_cfg, THU, THU + timedelta(days=1), transport=_dead,
+                         history=NoHistory()))
 check("a dead feed falls back to the static profile rather than to nothing",
       _fb.origin == "fallback" and _fb.has_prices)
 check("...with the SAME prices the configured-product path produces, because "
@@ -769,7 +771,8 @@ check("...and the provisional plan has no cheap window either: §8.3 forbids an
       not any(_fb.cheap_now(at_local(THU, h)) for h in range(24)))
 _fb_none = run(resolve_tariff(opts(None, price_provider="generic_dayahead",
                                    price_timeout_s=1),
-                              THU, THU + timedelta(days=1), transport=_dead))
+                              THU, THU + timedelta(days=1), transport=_dead,
+                              history=NoHistory()))
 check("a dead feed with NO static_profile has nothing to fall back to, and "
       "says that rather than inventing a tariff",
       _fb_none.origin == "none" and not _fb_none.has_prices)
@@ -785,7 +788,7 @@ async def _live(url, timeout_s):
 
 
 _live_plan = run(resolve_tariff(_cfg, THU, THU + timedelta(days=1),
-                                transport=_live))
+                                transport=_live, history=NoHistory()))
 check("a live feed is used in preference to the static profile",
       _live_plan.origin == "provider"
       and _live_plan.product is PriceProduct.DAY_AHEAD)

goodwe_controller/tools/rehearsal/state-legacy-plus-shed.json

@@ -0,0 +1,12 @@
+{
+ "_comment": "INSTR-01 SYNTHETIC FIXTURE - `state-legacy.json` with a SECOND roster unit already latched. Not a copy of any live state file. It exists to restore M12 END-TO-END on the STAGED leg, which is the arrangement SAFETY-44 and INSTR-01's first draft both missed: `snapshot_over()` starts the after-leg over the file the BEFORE-leg wrote, so a transition-made destination is available there and the two questions the provenance clause and the narrowing ask are NOT incompatible. Every same-step arrangement makes them incompatible; that is what was measured and over-generalised to 'no fixture can'.",
+ "phase": "idle",
+ "phase_started": "2026-08-07T10:00:00+00:00",
+ "last_completed": "2026-08-07T18:42:00+00:00",
+ "last_start_attempt": "2026-08-07T10:00:00+00:00",
+ "sign_tripped": true,
+ "sign_reason": "SIGN_DISAGREEMENT: commanded -1800 W against a meter reading -1450 W for 190 s",
+ "auto": true,
+ "unit/shed/sign_tripped": true,
+ "unit/shed/sign_reason": "SIGN_DISAGREEMENT: shed, latched before the switch"
+}

goodwe_controller/tools/rehearse_roster.py

@@ -460,6 +460,7 @@ class Snapshot:
         # finding: see `diff()`.
         self.stranded_at_default = []
         self.vanished_at_default = []
+        self.vanished_but_migrated = []
 
     @property
     def unit_keys(self):
@@ -544,12 +545,84 @@ def diff(before: Snapshot, after: Snapshot) -> list:
     # name and whose roster start writes them under another reported two
     # VANISHED findings about a pair of defaults, and CONTROL-C went red on a
     # build that was CORRECT.
+    # ⚠️ `claimed` MAKES THE MOVE INJECTIVE. Without it N vanished keys can all
+    # claim the SAME destination - and `DEFAULTS["sign_tripped"] is False`, so
+    # `True` is the ONLY non-default value a latch can hold, which means they
+    # collide by CONSTRUCTION rather than by coincidence. Two keys cannot both
+    # have become one key; the second claimant has not moved anywhere.
+    claimed = set()
     for key in sorted(set(before.data) - set(after.data)):
         value = before.data[key]
         bare = key.rsplit("/", 1)[-1]
         if value in (None, DEFAULTS.get(bare)):
             after.vanished_at_default.append(f"{key} = {value!r}")
             continue
+        # ⚠️ AND A KEY THAT MOVED TO A NAMESPACE A MACHINE READS HAS NOT
+        # VANISHED, WHICH IS THE SAME CORRECTION ONE PARAGRAPH UP, ONE CARD
+        # LATER. SAFETY-44's fix made `migrate_unit_keys()` write under the
+        # ROSTER's first name instead of the hardcoded `inverter-a`, so on a
+        # renamed roster the before-snapshot holds `unit/inverter-a/
+        # sign_tripped = True` and the after-snapshot holds
+        # `unit/garage/sign_tripped = True`. Measured on that build: two
+        # VANISHED findings for a LATCH THAT IS SITTING ON THE SAME PAGE OF THE
+        # REPORT, three lines above them, under the name the roster reads.
+        #
+        # ⚠️ THE TEST IS NOT "the name appears somewhere". It is: the SAME bare
+        # key, at the SAME value, under a key in `machine_read` - the set built
+        # by driving a real start, not by pattern-matching a namespace.
+        #
+        # ⚠️ THIS USED TO CITE "M3 (delete the flat rollback view)" AS WHAT
+        # BOUNDS IT, AND THAT CITATION WAS WRONG IN BOTH HALVES. M3 drops
+        # `sign_reason` from `LEGACY_UNIT_KEYS` and expects `LATCH KEY NOT UNDER
+        # A ROSTER NAME`; the delete-the-rollback-view mutant is M9, and every
+        # key M9 vanishes is FLAT, so it can never satisfy the `unit/` gate
+        # here. Neither mutation exercises this branch. The sentence "what keeps
+        # this from being a softening of the check" was not supported by the
+        # thing it named - and a citation is the worst possible carrier for that,
+        # because it reads as having been checked.
+        #
+        # ⚠️ AND THE REPLACEMENT CITATION WENT STALE THE SAME WAY. It read "the
+        # branch is now bounded by M12" through a card that DELETED M12 and a
+        # card that restored it on a different leg - eight lines below the
+        # paragraph condemning exactly this. Every clause of this comprehension
+        # is now graded by a row in test_rehearse.py part 5e, one case per
+        # clause, and each clause-removal must flip exactly its own row. That
+        # is a property of the section, not a pointer at a named check.
+        # ⚠️ AND THE DESTINATION MUST BE ONE **THIS TRANSITION MADE**
+        # (`before.data.get(k) != value`) AND NOT ALREADY SPOKEN FOR
+        # (`k not in claimed`). Without the first, a roster unit that was
+        # already latched in its own right is a free suppression slot that
+        # nobody moved into.
+        moved_to = sorted(
+            k for k in after.machine_read
+            if k.rsplit("/", 1)[-1] == bare and after.data.get(k) == value
+            and before.data.get(k) != value and k not in claimed)
+        # ⚠️ AND THE VANISHED KEY'S OWN UNIT MUST BE **OFF THE ROSTER**, WHICH
+        # THE FIRST VERSION OF THIS RULE DID NOT REQUIRE AND WHICH IS WHAT MADE
+        # IT A SOFTENING. The match was bare-key-plus-value over the whole of
+        # `machine_read`, with no identity - and `DEFAULTS["sign_tripped"] is
+        # False`, so the ONLY non-default value a latch can hold is `True`.
+        # Any surviving latched roster unit therefore suppressed any OTHER
+        # unit's vanished latch. Measured: a build that DROPS
+        # `unit/shed/sign_*` while `unit/garage/sign_*` survives, both latched
+        # by one site event so the reasons match too, reported
+        #
+        #     none in LEG SAME-STEP: nothing vanished, nothing stranded ...
+        #     NO FINDINGS in the rehearsed transitions
+        #
+        # exit 0, on a roster unit's SAFETY-02 latch that had been deleted.
+        #
+        # The legitimate case is a RENAME: the key left `inverter-a`, which is
+        # not on this roster, and arrived under `garage`, which is. A key whose
+        # own unit is still on the roster has not been renamed - it has been
+        # LOST - and no amount of the same value elsewhere makes that untrue.
+        vanished_unit = key.split("/")[1] if key.startswith("unit/") else None
+        if vanished_unit is not None and vanished_unit not in after.units \
+                and moved_to:
+            claimed.add(moved_to[0])
+            after.vanished_but_migrated.append(
+                f"{key} = {value!r} -> {moved_to[0]}")
+            continue
         findings.append(Finding(
             "VANISHED STORE KEY",
             f"{key} = {value!r} was in the store before the "
@@ -846,6 +919,15 @@ def report_transition(leg_id, name, before, after, findings) -> None:
         mark = "  " if key in after.data else "  (absent, defaulted) "
         print(f"      {key}{mark}")
 
+    if after.vanished_but_migrated:
+        print()
+        print("    keys that MOVED to the namespace this roster reads - not "
+              "lost, and shown")
+        print("    because a rename that relocates a LATCH is the operator's "
+              "business:")
+        for text in after.vanished_but_migrated:
+            print(f"      migrated  {text}")
+
     if after.stranded_at_default or after.vanished_at_default:
         print()
         print("    keys whose value IS the default `Store.load()` supplies, so "