Parse the wattage out of microwave power_level instead of a raw string

"700W"/"0W" was passed straight through as an untyped string sensor.
Parse the numeral and set device_class/unit so HA treats it as a power
measurement. Add a unit-handling step to the adding-device-support skill
so future dumps get this right the first time.

.claude/skills/adding-device-support/SKILL.md

@@ -103,7 +103,35 @@ sub-polled between summary polls. Pick descriptor types from `entities.py`
 as a gap for a human, or ignore it with a documented reason — never invent an
 entity on a hunch (`ignored.py`'s rule).
 
-## 5. Enum selects need translation support
+## 5. Parse units out of the value — don't ship them embedded in a string
+
+Samsung reps sometimes encode a numeral and its unit as one string
+(`x.com.samsung.da.powerLevel: "700W"`; a `desired`/`current` temperature whose
+unit lives in a sibling field instead). The lazy fix — a plain `SensorDesc`
+with no `device_class`/`unit` that passes the raw string straight through —
+binds the href and looks done, but HA then sees text, not a measurement: no
+unit conversion, no long-term statistics, no graphing. This shipped once
+already (microwave `power_level` went out as the literal string `"700W"`
+before being caught in review) — treat that as the standard failure mode to
+check for, not a one-off.
+
+Before wiring up a numeric-looking field:
+- **Check where the unit actually lives.** Embedded in the same string
+  (`powerLevel`)? A fixed, undocumented assumption (most wattages/energy
+  fields)? Or reported live in a sibling field (`/temperatures/vs/0`'s
+  per-item `unit`, `'Celsius'`/`'Fahrenheit'`)? Don't guess C vs F or W vs kW
+  without checking the dump.
+- **Parse the numeral in `value_fn`** (regex or strip the unit suffix) so the
+  entity's state is a number, not `"700W"`.
+- **Set `unit`** (static) **or `unit_fn`** (reads a live sibling field — see
+  `common.normalize_temp_unit`, used by both `fridge.py` and `oven.py` for a
+  per-device C/F reading) **plus the matching `device_class`/`state_class`**
+  so HA treats it as a real measurement.
+- A plain string `SensorDesc` (no unit/device_class) is still correct for
+  genuinely non-numeric state (mode names, enum-like text) — reserve it for
+  that, not as a shortcut past parsing a numeral.
+
+## 6. Enum selects need translation support
 
 Any select whose options are raw device codes (course/cycle, and code-valued
 settings) must render through translations, not Python:
@@ -114,7 +142,7 @@ settings) must render through translations, not Python:
   (e.g. `"16": "Cotton"`). Codes with no entry render as the raw code — that's
   the cue to identify and name them.
 
-## 6. Coverage discipline: bound or ignored
+## 7. Coverage discipline: bound or ignored
 
 Every href in the dump must resolve, or the repair fires. If a resource isn't
 worth an entity, add it to `capabilities/ignored.py` (a no-entity `Capability`)
@@ -128,7 +156,7 @@ friendlier href**.
   ignored because washers bind it. When only one family should ignore an href
   that another binds, scope the ignore to that family's registry.
 
-## 7. Reuse before writing new code
+## 8. Reuse before writing new code
 
 Check `common.py` (generic OCF: power, energy, alarms, water) and `laundry.py`
 (shared washer/dryer/dishwasher: buzzer, job status, `cycle_select` + course
@@ -137,7 +165,7 @@ registry uses `fridge.FIRMWARE_UPDATE`; all three laundry families share
 `laundry.cycle_select`. If two families hand-roll the same helper, hoist it to a
 shared module rather than copying.
 
-## 8. Lock it in
+## 9. Lock it in
 
 1. Add a **scrubbed** fixture `tests/fixtures/<type>_device.json`
    (`{"device0": [ {devcol rep}, {href, rep}, ... ]}`) — replace serials, MACs,

custom_components/localthings/registry/capabilities/microwave.py

@@ -11,8 +11,9 @@ re-declared here -- see by_type/microwave.py.
 and options-array toggles (only a Sound_On/Off slot on this dump -- no
 UpperLamp/fastpreheat/NaturalSteam like the oven family) are microwave-
 specific, so it gets its own capability here. /oven/vs/0 additionally
-reports a powerLevel field the oven family's cavity capability doesn't
-carry, so it also gets its own.
+reports a powerLevel field (a wattage with the unit embedded in the string,
+e.g. "700W") the oven family's cavity capability doesn't carry, so it also
+gets its own.
 
 Cycle start/pause is deliberately not modeled: unlike the oven family
 (whose module docstring documents confirmed-unreliable local cycle-start
@@ -27,6 +28,8 @@ below any plausible cook temperature, with no confirmed write contract.
 display string) is not modeled here -- every field is empty on this dump
 (device idle, no active cook program); see ignored.py.
 """
+import re
+
 from ..capability import Capability
 from ..entities import SelectDesc, SensorDesc, SwitchDesc
 from .common import normalize_temp_unit
@@ -39,6 +42,18 @@ def _int(v):
         return None
 
 
+_POWER_LEVEL_RE = re.compile(r'^(-?\d+)W$')
+
+
+def _power_level_watts(v):
+    """'0'/'700W' -> 0/700 -- the unit is embedded in the string on every
+    dump seen so far; strip it so the sensor reports a plain wattage."""
+    if not isinstance(v, str):
+        return None
+    m = _POWER_LEVEL_RE.match(v)
+    return int(m.group(1)) if m else None
+
+
 def _cavity_temp_unit(rep):
     items = rep.get('x.com.samsung.da.items') or []
     unit = items[0].get('x.com.samsung.da.unit') if items else None
@@ -111,10 +126,10 @@ MICROWAVE_CAVITY = Capability(
     entities=(
         SensorDesc(key='cavity_state', field='x.com.samsung.da.state',
                    name='Cavity state'),
-        # e.g. "0W"/"700W" -- unit is embedded in the string on every dump
-        # seen so far; shown as reported rather than parsed apart.
         SensorDesc(key='power_level', field='x.com.samsung.da.powerLevel',
-                   name='Power level', icon='mdi:flash'),
+                   name='Power level', icon='mdi:flash', device_class='power',
+                   state_class='measurement', unit='W',
+                   value_fn=_power_level_watts),
     ),
 )
 

tests/test_microwave_capabilities.py

@@ -84,9 +84,16 @@ def test_cavity_state_reads_state_field():
     assert desc.value_fn('Ready') == 'Ready'
 
 
-def test_power_level_reads_raw_string():
+def test_power_level_parses_watts():
     desc = next(e for e in microwave.MICROWAVE_CAVITY.entities if e.key == 'power_level')
-    assert desc.value_fn('700W') == '700W'
+    assert desc.value_fn('700W') == 700
+    assert desc.value_fn('0W') == 0
+
+
+def test_power_level_rejects_unparseable():
+    desc = next(e for e in microwave.MICROWAVE_CAVITY.entities if e.key == 'power_level')
+    assert desc.value_fn('') is None
+    assert desc.value_fn(None) is None
 
 
 # ---------------------------------------------------------------------------