diff --git a/custom_components/localthings/registry/capabilities/range.py b/custom_components/localthings/registry/capabilities/range.py
index 9941c19..c54fde1 100644
--- a/custom_components/localthings/registry/capabilities/range.py
+++ b/custom_components/localthings/registry/capabilities/range.py
@@ -148,11 +148,13 @@ COOKTOP_STATUS = Capability(
             value_fn=lambda v: str(v).lower() == "on",
         ),
         # Safe to write -- a lock toggle, not a heat control -- via a
-        # direct single-field PUT, no RMW needed.
+        # direct single-field PUT, no RMW needed. No device_class:
+        # SwitchDeviceClass only has 'outlet'/'switch', not 'lock' --
+        # passing it crashed switch platform setup for the whole device
+        # (issue #349, same bug as water_purifier.py's lock switches).
         SwitchDesc(
             key="cooktop_child_lock",
             field="childLock",
-            device_class="lock",
             entity_category="config",
             icon="mdi:lock",
             value_fn=lambda v: str(v).lower() == "on",
diff --git a/custom_components/localthings/registry/capabilities/water_purifier.py b/custom_components/localthings/registry/capabilities/water_purifier.py
index 671a375..e9a523b 100644
--- a/custom_components/localthings/registry/capabilities/water_purifier.py
+++ b/custom_components/localthings/registry/capabilities/water_purifier.py
@@ -182,10 +182,15 @@ FAVORITE_HOTWATER = Capability(
         # adapter.flatten() only ever honors exists_fn, not entity.py's
         # implicit field-presence default -- without it, whichever
         # same-keyed descriptor is processed last would silently win.
+        # No device_class: SwitchDeviceClass only has 'outlet'/'switch',
+        # not 'lock' -- passing it crashed switch platform setup entirely
+        # for the whole device (issue #349), same bug KIDS_LOCK_GENERIC
+        # dodged by switching to BinarySensorDesc (issues #181/#183). This
+        # entity stays a SwitchDesc since it's genuinely writable.
         SwitchDesc(
             key="hotwater_lock",
             field="x.com.samsung.da.switchHotwater",
-            device_class="lock",
+            icon="mdi:lock",
             entity_category="config",
             value_fn=lambda v: v != "Unlocked",
             exists_fn=lambda rep, resources: (
@@ -354,11 +359,13 @@ LOCK = Capability(
     entities=(
         # Shares its key with FAVORITE_HOTWATER's switchHotwater fallback
         # above (issue #144); see the comment there. A stub rep ({}) still
-        # counts as "present" here, matching entity.py's own default.
+        # counts as "present" here, matching entity.py's own default. No
+        # device_class on any of the three locks below -- see the
+        # device_class note on FAVORITE_HOTWATER's hotwater_lock (issue #349).
         SwitchDesc(
             key="hotwater_lock",
             field="x.com.samsung.da.hotwaterLock",
-            device_class="lock",
+            icon="mdi:lock",
             entity_category="config",
             value_fn=lambda v: v != "Unlocked",
             exists_fn=lambda rep, resources: not rep or "x.com.samsung.da.hotwaterLock" in rep,
@@ -370,7 +377,7 @@ LOCK = Capability(
         SwitchDesc(
             key="coldwater_lock",
             field="x.com.samsung.da.coldwaterLock",
-            device_class="lock",
+            icon="mdi:lock",
             entity_category="config",
             value_fn=lambda v: v != "Unlocked",
             write_fn=lambda p, rep, href=None: (
@@ -381,7 +388,7 @@ LOCK = Capability(
         SwitchDesc(
             key="buzz_lock",
             field="x.com.samsung.da.buzzLock",
-            device_class="lock",
+            icon="mdi:lock",
             entity_category="config",
             value_fn=lambda v: v != "Unlocked",
             write_fn=lambda p, rep, href=None: (
diff --git a/tests/test_switch_device_class.py b/tests/test_switch_device_class.py
new file mode 100644
index 0000000..653df47
--- /dev/null
+++ b/tests/test_switch_device_class.py
@@ -0,0 +1,45 @@
+"""Guards against a SwitchDesc.device_class HA's SwitchDeviceClass doesn't
+recognize -- switch.py passes it straight to SwitchDeviceClass(...), and an
+invalid value raises out of the whole switch platform's async_setup_entry,
+taking down every switch entity for the device, not just the offending one
+(issue #349: water_purifier.py's lock switches used device_class='lock',
+which SwitchDeviceClass only ever supported as 'outlet'/'switch').
+
+Scans every by_type registry's declared capabilities rather than a specific
+fixture, so a new capability introducing the same mistake fails here instead
+of only surfacing as a live crash report.
+"""
+
+import importlib
+import pkgutil
+
+from homeassistant.components.switch import SwitchDeviceClass
+
+from custom_components.localthings.registry import by_type
+from custom_components.localthings.registry.entities import SwitchDesc
+
+
+def _all_registries():
+    for mod_info in pkgutil.iter_modules(by_type.__path__):
+        if mod_info.name.startswith("_"):
+            continue
+        mod = importlib.import_module(
+            f"custom_components.localthings.registry.by_type.{mod_info.name}"
+        )
+        reg = getattr(mod, "REGISTRY", None)
+        if reg is not None:
+            yield reg
+
+
+def test_every_switchdesc_device_class_is_valid_for_ha():
+    bad = []
+    for reg in _all_registries():
+        caps = [c for cs in reg.capabilities.values() for c in cs] + list(reg.pattern_capabilities)
+        for cap in caps:
+            for entity in cap.entities:
+                if isinstance(entity, SwitchDesc) and entity.device_class is not None:
+                    try:
+                        SwitchDeviceClass(entity.device_class)
+                    except ValueError:
+                        bad.append((reg.name, entity.key, entity.device_class))
+    assert bad == []