CFG-04: an operator can declare a second inverter, and the shape was measured

DEV-02 made every per-device value per-instance - rating, SoC, watchdogs,
heartbeat, store keys - so the code stopped assuming one inverter. The options
schema did not. `build_roster()` returned a list of exactly one and said so in
its own docstring, and there was no `inverters:` key for an operator to write,
so the roster could only ever be a roster of one.

THE SHAPE, AND WHY IT WAS MEASURED RATHER THAN CHOSEN

config.yaml had no list-of-objects anywhere, and `static_profile` carries a
whole tariff structure as a JSON string in a `str?` precisely because a nested
schema was doubted. That is a question about somebody else's software, so it was
answered by running it: `tools/supervisor_shape_probe.py` (committed) runs
Supervisor 2026.08.0's OWN `AppOptions` validator and `SCHEMA_APP_CONFIG`, out
of the release image, against this repository's config.yaml. 2026.08.0 is the
version the live install reports. The full transcript and the argument are in
DECISIONS/CFG-04-inverter-roster.md.

It accepts the list, enforces per-entry types, refuses a missing `name` /
`setpoint_entity` / `max_w` BY NAME, renders the option in the UI as a
repeatable section, and drops the key with a warning under an older schema - so
a downgrade is not the forward trap in reverse.

⚠️ AND THE `inverters: []` DEFAULT IS LOAD-BEARING, WHICH IS THE MEASUREMENT
THAT MATTERED MOST. Supervisor answers `Missing option 'inverters' in root` for
an options blob that has no such key - which every existing install's has, since
the key did not exist when they were written. `App.options` is the shipped
`options:` block deep-merged with the operator's stored one, so the empty
default is the difference between an upgrade nobody notices and an add-on that
cannot start with a schema pinned to the version that would fix it. That is
docs/deploy-rollback.md §4's trap in the FORWARD direction, found before it was
sprung. The merger was checked too: lists override rather than concatenate, so a
non-empty default could not have grown a roster behind the operator's back.

NOTHING IS INHERITED, WHICH IS DEV-02 RESTATED AS A CONFIG RULE

`name`, `setpoint_entity` and `max_w` are required of every entry. An entry that
omits `soc_entity` has no SoC sensor; it does not borrow the flat one. A
three-line fallback would have rebuilt the sibling-grading defect DEV-02 spent a
card removing, in YAML. Defaults still live in exactly one place (CFG-03):
there is no per-entry default anywhere, because there is no optional per-entry
number. A flat `setpoint_entity` left set beside a declared roster is refused
rather than ignored - it names an actuator nothing will write.

TWO PERMISSIVE READERS IN SHIPPED CODE, AND THREE MORE IN THE CHECKS

  validate.py rules 5 and 6 compared their thresholds against the FLAT `max_w`.
  At a roster of two 2000 W units with `max_w: 5000` left over from a
  single-inverter install, `sign_disagree_w: 3000` passed rule 5 while
  SAFETY-02's watchdog could fire on NEITHER unit - rule 5's own failure mode,
  reached through rule 5. They read `unit_caps()` now, which at one inverter is
  `[max_w]` exactly.

  main.py's `run_control()` re-ran the device-rating check behind
  `if self.o.get("setpoint_entity")` - the flat key, which a roster leaves blank
  - so on a two-inverter site no inverter's `max_w` was graded against the
  device it is written to, and the skip was silent. `validate_unit_ranges()`
  grades each unit against its own ESPHome and runs unconditionally.

  test_peakguard.py's `read_option()` and `_schema_bound()` and
  test_inverter.py's `read_schema_max()` matched a STRIPPED line and took the
  first hit, so the nested per-inverter `max_w:` began outranking the flat one -
  silently, and correctly, because the two bounds are the same int(100,5000)
  today. A reader that is right by coincidence is this project's named failure
  mode. All three are anchored at exactly two spaces now; the file's two halves
  disambiguate `peak_cap_w` instead of first-match, and an ambiguous key raises
  rather than picking one. test_tariff.py's copy of the idiom went with them.

THE AUDIT IS A CHECK, NOT A PROMISE

test_inverter.py part 11 finds every config.yaml-reading function in the suite -
transitively, because two of the readers CFG-04 had to change never name the
file - EXECUTES each against a synthetic two-inverter config.yaml whose
per-inverter numbers differ from its flat ones, and fails if any answers with
the per-inverter value. The table is not maintained by hand: the signature
decides, so the eleventh reader is named on its first run. config.yaml declares
`inverters:` BEFORE `max_w:` on purpose and part 11 asserts that ordering, so
the trap stays baited.

SAFETY-28's `actuator_writers()` needed no change - it was already a structural,
case-folding census - but until now there was no configuration in which two
writers on one actuator could be WRITTEN DOWN. There is now, and it is refused.

VERIFIED BY BREAKING IT

Ten mutations run through tools/mutation_run.sh and observed red, listed in
test_inverter.py part 12 with the check that bites each. Two survived the first
run and the CHECKS were changed, not the table: the inheritance check had blank
flat keys, so "inherited" and "not inherited" were the same empty string; and
the `run_control()` check asserted a SOURCE LINE was present, which re-indenting
it does not remove. Both are recorded in MUTATION.md's "the check's data cannot
reach the failure it names" section, which now carries two more habits: assert
on behaviour rather than on source text, and give a check whose failure mode is
a hang a deadline.

19/19 green in the goodwe-addon-ci image. The one-inverter path is byte-
identical: the whole existing suite runs unmodified against it.

Version bumped to 0.6.0 - the Supervisor keys the built image by `version:`, so
a schema change without a bump is a schema nobody reads.

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

goodwe_controller/MUTATION.md

@@ -135,8 +135,9 @@ manufactures them from a **fixture**: the check runs, the assertion is
 evaluated, the sentence above it is true — and the numbers it compares are
 arranged so that the failure it describes could not have changed the answer.
 
-It is not hypothetical and it is not rare. Three instances in one week, all
-found by review rather than by a red line:
+It is not hypothetical and it is not rare. Five instances in two weeks; the
+first three were found by review rather than by a red line, and the last two -
+CFG-04's - by an author's own mutation battery, which is the cheaper place:
 
 * **ARB-03** shipped a call-site scan asserting that every `claims.append` in
   `cycle()` routes through `actuator_of()`. Its own parse **saw 3 of the 8
@@ -150,6 +151,20 @@ found by review rather than by a red line:
   B's rating to A's, so it compared `(-5000, 5000)` against `(-5000, 5000)` —
   **a number against itself**. Filing both per-unit bounds from
   `self.inverters[0]` left **all 19 files green**.
+* **CFG-04** wrote *"an entry that omits `soc_entity` has NO SoC sensor and does
+  not borrow the flat one"* against a fixture whose **flat `soc_entity` was
+  blank**. Inherited and not-inherited were both `""`, so the mutation that
+  makes `build_roster()` fall back to the flat key survived. The fixture now
+  sets a real entity there, and the check asserts that the flat value is present
+  as well as that the entry's is empty.
+* **CFG-04** also wrote *"main.py runs the per-unit range check
+  UNCONDITIONALLY"* as a **substring test over `app/main.py`'s source**. The
+  mutation that defeats it puts the call back inside `if entity:` — one level of
+  indentation — and the substring is still there. That is habit 4 below in a new
+  costume: the check asserted against the TEXT of the thing under test rather
+  than against its behaviour. It now drives the shipped `run_control()` on a
+  two-inverter config, **under a deadline**, because the mutation's real symptom
+  is that the controller enters its loop and never returns.
 
 Note what these have in common with a masked rung: the mutation *runs*, and the
 suite is *honestly* green. Nothing in a purge, a fingerprint or a disassembly
@@ -177,6 +192,17 @@ Three cheap habits fall out of it, and all three are now used in this repository
    actuator: {'inverter-a': (-5000, 5000), 'inverter-b': (-5000, 5000)}` is
    self-evidently not evidence of a difference.
 
+4. **Assert on the BEHAVIOUR, not on the source text of the thing under test.**
+   A substring test over a module is a check on how the code is spelled;
+   whitespace, an alias or a moved line defeats it while the property it names
+   is gone. `test_inverter.py` part 10 has one of each — a source pin for a
+   claim that genuinely IS about the code's shape, and a driven `run_control()`
+   for a claim about behaviour — and the second replaced the first after the
+   mutation battery walked straight through it.
+5. **A check whose failure mode is a HANG needs a deadline.** Otherwise the
+   mutation that defeats it produces a CI timeout with no name attached, which
+   reads like flaky infrastructure and gets retried rather than read.
+
 And the mutation-table consequence: **a variant is not covered because a
 near-miss of it is.** DEV-02's table listed the *actuator* variant of the
 per-unit claim defect (`device`/`supervised` filed without `inv`), which the