TARIFF-02: one canonical price format, and a seam that keeps supplier names out of the optimiser

Five provider plugins - generic_dayahead, engie_dynamic,
totalenergies_dynamic, eneco_eddy, manual_csv - all emitting exactly
{"prices": [{"start", "eur_per_kwh", "provisional"}]}, tz-aware at the
Brussels offset, EUR/kWh, all-in. Nothing consumes it yet; the seam
lands first, per the PM's ordering.

It is built in goodwe_controller/app/ rather than at specs.md 2.2's
ems/ingest/prices/, per the product owner's decision of 2026-08-30. The
behaviour 9.3 / 8.3 / 11.4 specifies is unchanged.

Three things shape the design, and each is the mechanism rather than a
comment saying to be careful:

Double-counting the markup is unreachable. A plugin does not return a
price - it returns the figure its source published and declares which of
{energy, markup, taxes} that figure already contains. assemble() adds
the complement, once, in the framework. A plugin is never handed
price_markup_eur_kwh: PluginOptions raises FrameworkOption on it, so the
line that adds the margin a second time cannot be written. Engie and
TotalEnergies publish a retail figure with their margin inside; adding
the configured 3 c/kWh on top would have made every arbitrage decision
wrong by that amount with nothing reporting it.

The product type is declared, not inferred from the plugin's name.
eneco_eddy is real-time/imbalance and gets 8.3's widened thresholds
through capabilities().product and volatility_regime(), never through a
name comparison - which is AC2. test_price.py asserts mechanically that
no plugin id appears anywhere in the framework's code, and drives a
sixth provider defined inside the test file to the right regime with
price.py untouched.

"No price data" is a type, not an empty list - the same rework
sim/riglock.py took under TEST-04. A fetch returns PriceRead.series(...)
or PriceRead.no_data(reason), and only the first carries fields. An
empty series is not constructible; no_data has no .points, no .at(), and
.get("points", []) raises rather than returning the default. A day of
free electricity and a day with no prices are different instructions -
arbitrage is pointless under one and forbidden under the other - and an
implementation returning [] cannot tell them apart. Every site-level
failure returns no_data; nothing raises into the control tick.

Also: injection stays a separate scalar (export_price_eur_kwh, AC4),
negative prices survive the boundary validator (17's regression case),
egress is allow-listed against each plugin's own declaration (16), and
no tzdata is used - the shipped Alpine image has none, so Brussels
offsets come from the EU rule and instants are carried as UTC.

validate.py grows rule 7: an unknown provider id, manual_csv with no
path, and - the HA overlap the PM told us to decide about -
price_provider set alongside price_now_entity/price_avg_entity, which is
two price sources where the HA pair silently wins. The HA sensors are
kept and still work alone; TARIFF-03 and OPT-04 are what replace them.

CFG-03 is not widened: the price defaults have ONE in-code mirror,
PRICE_OPTION_DEFAULTS, which validate.py imports rather than restating
and which test_price.py pins to config.yaml by reading the file.

test_price.py is runnable, assert-free in the house style, and every
verdict it prints is derived. It grades the markup arithmetic with
0.031/0.057 rather than the shipped 0.03/0.06, because 0.06 is exactly
twice 0.03 and a degenerate pair would make double-counting
indistinguishable from correct addition - and it asserts that
non-degeneracy as its first section. The DST checks run on the 23-hour
and 25-hour days, not on a normal day where a fixed 24-slot
implementation and a correct one agree. Thirteen mutations were driven
through it; all thirteen go red.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015VXjA3LWccN1rJsk3okyPC

goodwe_controller/app/validate.py

@@ -116,6 +116,21 @@ NOT READY banner already names the problem, (b) does not apply.
      (13.8 kWh usable at 2000 W is ~6.9 h against the 720 min DRAIN_TIMEOUT).
      It is warned about below, not refused.
 
+  7. A price configuration that cannot mean what it says.  [(a)]
+     Three cases, all in `_price_problems()`: an unknown `price_provider` id
+     (refused rather than defaulted to 'off', per the §14 warning box);
+     `price_provider` set alongside `price_now_entity`/`price_avg_entity`,
+     which is TWO PRICE SOURCES ON ONE SITE where the Home Assistant pair
+     silently wins; and `manual_csv` with no `price_csv_path`, which turns the
+     documented offline fallback into a permanent no-price-data condition
+     reached by accident. Same shape as 1, 4 and 5 every time - a source the
+     operator chose, overridden by a layer they cannot see.
+
+     ⚠️ `price_provider: "off"` IS NOT REFUSED AND MUST NOT BECOME SO. §11.4
+     makes no-price-data a supported state, and §9.2 says a large share of the
+     installed base is on a fixed or static tariff. Refusing to start without a
+     price feed would lock those sites out of the add-on entirely.
+
 WHAT IS DELIBERATELY *NOT* REFUSED, because it is untidy rather than unsafe:
 
   - `integrator_max_w` above `max_w`. DOCS.md is right that the only thing the
@@ -141,6 +156,7 @@ WHAT IS DELIBERATELY *NOT* REFUSED, because it is untidy rather than unsafe:
 import logging
 
 from .p1 import is_enabled, validate_meter_options
+from .price import PROVIDERS
 
 _LOG = logging.getLogger("goodwe.config")
 
@@ -349,6 +365,9 @@ def validate_startup_config(opts: dict, dev_min=None, dev_max=None) -> list[str]
             f"two numbers. Lower maintenance_charge_w to {max_w:.0f} W or less, "
             f"or raise max_w to at least {charge_w:.0f} W.")
 
+    # --- 7. two price sources on one site ------------------------------------
+    problems.extend(_price_problems(opts))
+
     # --- warnings: real, but not worth refusing over -------------------------
     integ = opts.get("integrator_max_w")
     integ_w = None if not integ else _number(opts, "integrator_max_w", None)
@@ -382,6 +401,66 @@ def validate_startup_config(opts: dict, dev_min=None, dev_max=None) -> list[str]
     return problems
 
 
+def _price_problems(opts: dict) -> list[str]:
+    """Rule 7 (TARIFF-02): the price configuration, refused where it is untrue.
+
+    ⚠️ NOTE WHAT IS *NOT* HERE. `price_provider: "off"` is not refused and never
+    will be: §11.4 makes no-price-data a first-class supported state (static
+    profile, provisional plan, no arbitrage), and an add-on that will not start
+    without a price feed is an add-on that a Belgian fixed-tariff site - a large
+    share of the installed base, per §9.2 - cannot run at all.
+
+    Three refusals, all case (a) from this module's docstring: a source the
+    operator SET being overridden by a layer they cannot see.
+    """
+    problems: list[str] = []
+    pid = str(opts.get("price_provider", "") or "off").strip() or "off"
+
+    if pid != "off" and pid not in PROVIDERS:
+        problems.append(
+            f"price_provider is {pid!r}, which is not a shipped plugin. The "
+            f"ids that exist are: off, {', '.join(sorted(PROVIDERS))}. "
+            "Refused rather than defaulted, per the §14 warning box - a "
+            "silent fall back to 'off' would look exactly like a working "
+            "provider that happens never to find a cheap hour.")
+        return problems          # nothing below can be judged against an unknown id
+
+    # ⚠️ THE HA-SIDE OVERLAP THE PM TOLD US TO DECIDE ABOUT, DECIDED HERE.
+    # price_now_entity/price_avg_entity are the existing delegation of pricing
+    # to Home Assistant: main.py reduces them to ONE BOOLEAN, `cheap`, read only
+    # by the maintenance cheap-window charge floor. They are KEPT (TARIFF-03 and
+    # OPT-04 are what replace them, and neither has landed), but they may not
+    # run alongside a provider. With both configured the provider series drives
+    # nothing at all while the two entities quietly keep deciding, and the
+    # operator's evidence that they picked a supplier is a status line saying
+    # they picked a supplier. That is (a), and it is the "silently double up"
+    # the PM named on 2026-08-30.
+    ha_price = [k for k in ("price_now_entity", "price_avg_entity")
+                if str(opts.get(k, "") or "").strip()]
+    if pid != "off" and ha_price:
+        problems.append(
+            f"price_provider is {pid!r} AND {' and '.join(ha_price)} "
+            f"{'is' if len(ha_price) == 1 else 'are'} set, which is two price "
+            "sources on one site. THE HOME ASSISTANT ENTITIES WIN: they are "
+            "what main.py reduces to the `cheap` flag the maintenance cycle "
+            "reads, and nothing yet consumes the provider series, so the "
+            "supplier you configured would decide nothing while the status "
+            "page named it. Clear price_now_entity and price_avg_entity to use "
+            f"the {pid!r} plugin, or set price_provider to 'off' to keep the "
+            "Home Assistant sensors.")
+
+    if pid == "manual_csv" and not str(opts.get("price_csv_path", "") or "").strip():
+        problems.append(
+            "price_provider is 'manual_csv' but price_csv_path is empty, so "
+            "the offline fallback has no file to read. Every fetch would "
+            "return no-price-data with a filesystem error as its reason - "
+            "which is §11.4 behaviour arrived at by accident rather than by "
+            "configuration. Point it at the CSV, or set price_provider to "
+            "'off', which says the same thing on purpose.")
+
+    return problems
+
+
 def _number(opts: dict, key, default):
     raw = opts.get(key, default)
     if raw is None or raw == "":