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/DOCS.md

@@ -55,6 +55,70 @@ Use the ESP32's readings rather than the inverter's cloud or dongle sensors:
 those serve cached values, and a stale reading here ends the maintenance charge
 phase having charged nothing.
 
+### More than one inverter (`inverters`)
+
+The six keys above describe **one** inverter, and if that is your site there is
+nothing to do here — `inverters` ships empty and empty means *"the flat keys
+above describe the one inverter"*. **An install that upgrades into 0.6.0 reads
+identically to before: same entities, same rating, same behaviour, no operator
+action.**
+
+To run two, declare them. Each entry names its own actuator, its own rating and
+its own sensors:
+
+```yaml
+setpoint_entity: ""          # ⚠️ must be cleared — see below
+inverters:
+  - name: inverter-a
+    setpoint_entity: number.goodwe_a_setpoint_w
+    soc_entity: sensor.goodwe_a_soc
+    batt_entity: sensor.goodwe_a_battery_power
+    max_w: 5000
+  - name: inverter-b
+    setpoint_entity: number.goodwe_b_setpoint_w
+    soc_entity: sensor.goodwe_b_soc
+    batt_entity: sensor.goodwe_b_battery_power
+    max_w: 3000
+```
+
+| per-entry key | required | meaning |
+|---|---|---|
+| `name` | yes | Short identifier. It namespaces this unit's SAFETY-02 latch, heartbeat and write bookkeeping in the add-on's state file, so **two units may not share one** |
+| `setpoint_entity` | yes | This inverter's own ESPHome `number.*_goodwe_setpoint_w` |
+| `max_w` | yes | The supervised cap on what may be written to **this** inverter. The site's ceiling is the **sum** |
+| `soc_entity` | | This pack's state of charge |
+| `batt_entity` | | This unit's battery power, `+` = discharging |
+| `batt_invert` | | Flip if needed |
+
+⚠️ **Nothing is inherited.** An entry that leaves out `soc_entity` has **no SoC
+sensor** — it does *not* fall back to the flat one. That is deliberate: every
+per-device value became per-instance in 0.5.x precisely so that no inverter is
+ever graded against a sibling's numbers, and a silent fallback would rebuild
+that in YAML. `name`, `setpoint_entity` and `max_w` are required of every entry
+for the same reason: there is no rating to borrow.
+
+⚠️ **Clear the flat `setpoint_entity` when you declare a roster,** or the add-on
+refuses to start and says so. It is the single-inverter form and it is not read
+once a roster exists, so leaving it set means one of two things: it names an
+entity an entry also names — two writers on one actuator, which specs §1.5 makes
+a non-goal and the add-on refuses outright — or it names a different one, which
+nothing would ever write, leaving a site running quietly smaller than its
+configuration reads. `soc_entity`, `batt_entity`, `batt_invert` and `max_w`
+cannot be blanked (the schema gives them no empty value); they are simply not
+read, and the add-on writes one line into its action log at every start saying
+so.
+
+⚠️ **Two inverters naming the same `setpoint_entity` are refused,** whichever
+keys they are declared under and whatever the capitalisation. Two independent
+setpoints on one inverter is the arbitration problem this add-on exists not to
+have.
+
+⚠️ **Update the add-on first, then add the roster.** Home Assistant validates the
+options you save against the schema of the version that is *installed*, so
+`inverters` cannot be set before 0.6.0 is installed. The order is: update, then
+configure. Going the other way — downgrading with a roster configured — is safe:
+the older schema drops the key with a warning rather than refusing.
+
 ### P1 meter ingestion
 
 `meter_entity` above expects one signed sensor, which usually means a template
@@ -272,7 +336,7 @@ behind it would trip the firmware watchdog on a system that is working fine.
 
 | option | default | meaning |
 |---|---|---|
-| `max_w` | 2000 | Hard limit on what may be commanded. Start low, raise after commissioning |
+| `max_w` | 2000 | Hard limit on what may be commanded. Start low, raise after commissioning. **Not read when `inverters` is declared** — each entry carries its own, and the site ceiling is their sum |
 | `gain` | 0.6 | Correction per cycle. **At the limit — do not raise** |
 | `slew_w` | 1000 | Maximum change per cycle |
 | `deadband_w` | 15 | Ignore errors smaller than this |