fix(coordinator): retry a command once after a dead-session reconnect

async_send_command's _do_put caught any exception, logged it, and
returned -- no reconnect, no retry, no error the user could see. A
command landing on a session Samsung's firmware closed between polls
(the same 'known device behavior' _async_update_data already
reconnects around) was silently lost, with nothing to do about it but
a manual reload of the device (issue #294).

Mirror the poll path's own recovery: on failure, close the dead
session, pause, and retry the PUT once against a freshly reconnected
one. If that also fails, raise a HomeAssistantError instead of just
logging, so the user gets a visible error rather than a command that
quietly did nothing. The retry runs under the same session lock the
poll path uses, so a write landing mid-reconnect can't race a
concurrent poll cycle rebuilding the same session.

custom_components/localthings/coordinator.py

@@ -15,7 +15,7 @@ from typing import Any
 import cbor2
 from homeassistant.config_entries import ConfigEntry
 from homeassistant.core import HomeAssistant, callback
-from homeassistant.exceptions import ServiceValidationError
+from homeassistant.exceptions import HomeAssistantError, ServiceValidationError
 from homeassistant.helpers import issue_registry as ir
 from homeassistant.helpers.device_registry import DeviceInfo
 from homeassistant.helpers.update_coordinator import DataUpdateCoordinator, UpdateFailed
@@ -1026,18 +1026,42 @@ class LocalThingsCoordinator(DataUpdateCoordinator[dict[str, Any]]):
         )
 
         def _do_put():
+            if self._session is None:
+                self._connect_session()
             sess = self._session
             if sess is None:
                 raise RuntimeError("no session")
             code, _ = sess.post(path_segs, cbor2.dumps(body), timeout=self._POST_TIMEOUT_S)
             self._log.info("PUT %s → code %#04x", write_href, code)
 
-        try:
-            await self.hass.async_add_executor_job(_do_put)
-        except Exception as e:
-            self._log.error("command failed for %s: %s", write_href, e)
-        else:
-            await self.async_request_refresh()
+        # A session Samsung's firmware closed between polls (the same "known
+        # device behavior" _async_update_data reconnects around) previously
+        # sank the PUT here with nothing but a log line -- no retry, no
+        # user-facing error, so the command was silently lost until the next
+        # manual reload (issue #294). Mirror the poll path's own recovery:
+        # one reconnect, one retry, and this time raise on final failure so
+        # the user gets a red toast instead of nothing.
+        #
+        # Locked the same as the poll path so a write landing mid-reconnect
+        # doesn't tear down a session _async_update_data is simultaneously
+        # rebuilding (or vice versa).
+        async with self._session_lock:
+            try:
+                await self.hass.async_add_executor_job(_do_put)
+            except Exception as e:
+                self._log.warning("command failed for %s, reconnecting: %s", write_href, e)
+                await self.hass.async_add_executor_job(self._close_session)
+                await asyncio.sleep(self._RECONNECT_PAUSE_S)
+                try:
+                    await self.hass.async_add_executor_job(_do_put)
+                except Exception as e2:
+                    self._log.error("command failed for %s after reconnect: %s", write_href, e2)
+                    raise HomeAssistantError(
+                        translation_domain=DOMAIN,
+                        translation_key="command_failed",
+                        translation_placeholders={"href": write_href, "error": str(e2)},
+                    ) from e2
+        await self.async_request_refresh()
 
     # ------------------------------------------------------------------
     # Debug raw write (issue #54): a power-user escape hatch for the

custom_components/localthings/translations/cs.json

@@ -1356,6 +1356,9 @@
     },
     "intensive_unavailable_for_cycle": {
       "message": "Intenzivní není u vybraného cyklu k dispozici."
+    },
+    "command_failed": {
+      "message": "Příkaz pro {href} selhal i po opětovném připojení: {error}"
     }
   }
 }

custom_components/localthings/translations/en.json

@@ -1356,6 +1356,9 @@
     },
     "intensive_unavailable_for_cycle": {
       "message": "Intensive isn't available on the selected cycle."
+    },
+    "command_failed": {
+      "message": "The command to {href} failed even after reconnecting: {error}"
     }
   }
 }

custom_components/localthings/translations/es.json

@@ -119,6 +119,9 @@
     },
     "intensive_unavailable_for_cycle": {
       "message": "El modo intensivo no está disponible en el ciclo seleccionado."
+    },
+    "command_failed": {
+      "message": "El comando para {href} falló incluso después de reconectar: {error}"
     }
   },
   "entity": {

custom_components/localthings/translations/it.json

@@ -1356,6 +1356,9 @@
     },
     "intensive_unavailable_for_cycle": {
       "message": "Intensivo non è disponibile per il ciclo selezionato."
+    },
+    "command_failed": {
+      "message": "Il comando per {href} è fallito anche dopo la riconnessione: {error}"
     }
   }
 }

custom_components/localthings/translations/ko.json

@@ -1356,6 +1356,9 @@
     },
     "intensive_unavailable_for_cycle": {
       "message": "선택한 코스에서는 강력 세탁을 사용할 수 없습니다."
+    },
+    "command_failed": {
+      "message": "재연결 후에도 {href} 명령이 실패했습니다: {error}"
     }
   }
 }

custom_components/localthings/translations/nl.json

@@ -1356,6 +1356,9 @@
     },
     "intensive_unavailable_for_cycle": {
       "message": "Intensief is niet beschikbaar voor het geselecteerde programma."
+    },
+    "command_failed": {
+      "message": "Het commando naar {href} is ook na opnieuw verbinden mislukt: {error}"
     }
   }
 }

tests/localthings/test_coordinator.py

@@ -1007,6 +1007,89 @@ async def test_send_command_survives_stale_confirm_poll(
     assert coordinator._cache.get("/test/vs/0") == {"value": 5}
 
 
+async def test_send_command_reconnects_and_retries_after_socket_closed(
+    hass: HomeAssistant,
+    mock_entry,
+    mock_coordinator_observe_session,
+) -> None:
+    """A command lost to a session Samsung's firmware closed between polls
+    must not just vanish (issue #294): `_do_put` failing once is now
+    followed by a reconnect and a single retry, mirroring the poll path's
+    own recovery in `_async_update_data`."""
+    from custom_components.localthings.registry.discovery import BoundEntity
+    from custom_components.localthings.registry.entities import NumberDesc
+
+    fake = mock_coordinator_observe_session
+    await hass.config_entries.async_setup(mock_entry.entry_id)
+    await hass.async_block_till_done()
+    coordinator: LocalThingsCoordinator = hass.data[DOMAIN][mock_entry.entry_id]
+
+    def _write_fn(payload, rep, href=None):
+        return (["test", "vs", "0"], {"value": payload})
+
+    desc = NumberDesc(key="test", field="value", write_fn=_write_fn)
+    bound = BoundEntity(href="/test/vs/0", capability=coordinator.bound[0].capability, desc=desc)
+
+    calls = {"n": 0}
+
+    def _post(*args, **kwargs):
+        calls["n"] += 1
+        if calls["n"] == 1:
+            raise ConnectionError("socket closed")
+        return (0x44, b"")
+
+    with (
+        patch.object(fake, "subscribe"),
+        patch(
+            "custom_components.localthings.coordinator.asyncio.sleep",
+            new=AsyncMock(),
+        ),
+    ):
+        fake.post = _post
+        await coordinator.async_send_command(bound, 5)
+
+    assert calls["n"] == 2
+    assert coordinator._cache.get("/test/vs/0") == {"value": 5}
+
+
+async def test_send_command_raises_after_reconnect_retry_also_fails(
+    hass: HomeAssistant,
+    mock_entry,
+    mock_coordinator_observe_session,
+) -> None:
+    """If the command still fails on the reconnected session, the user must
+    see it -- previously this was swallowed into a log line with no
+    feedback at all (issue #294)."""
+    from homeassistant.exceptions import HomeAssistantError
+
+    from custom_components.localthings.registry.discovery import BoundEntity
+    from custom_components.localthings.registry.entities import NumberDesc
+
+    fake = mock_coordinator_observe_session
+    await hass.config_entries.async_setup(mock_entry.entry_id)
+    await hass.async_block_till_done()
+    coordinator: LocalThingsCoordinator = hass.data[DOMAIN][mock_entry.entry_id]
+
+    def _write_fn(payload, rep, href=None):
+        return (["test", "vs", "0"], {"value": payload})
+
+    desc = NumberDesc(key="test", field="value", write_fn=_write_fn)
+    bound = BoundEntity(href="/test/vs/0", capability=coordinator.bound[0].capability, desc=desc)
+
+    def _post(*args, **kwargs):
+        raise ConnectionError("socket closed")
+
+    with (
+        patch(
+            "custom_components.localthings.coordinator.asyncio.sleep",
+            new=AsyncMock(),
+        ),
+        pytest.raises(HomeAssistantError),
+    ):
+        fake.post = _post
+        await coordinator.async_send_command(bound, 5)
+
+
 async def test_second_write_to_same_href_lands_during_first_writes_settle_window(
     hass: HomeAssistant,
     mock_entry,