diff --git a/custom_components/dkncloudna/entity.py b/custom_components/dkncloudna/entity.py
new file mode 100644
index 0000000..cba7ec4
--- /dev/null
+++ b/custom_components/dkncloudna/entity.py
@@ -0,0 +1,116 @@
+"""Shared base entity for DKN Cloud NA."""
+
+from __future__ import annotations
+
+import asyncio
+import time
+from typing import Any
+
+from homeassistant.helpers.device_registry import CONNECTION_NETWORK_MAC, DeviceInfo
+from homeassistant.helpers.update_coordinator import CoordinatorEntity
+
+from .const import DOMAIN, MANUFACTURER, OPTIMISTIC_TTL_SEC, POST_WRITE_REFRESH_DELAY_SEC
+from .coordinator import DknCoordinator
+
+
+class DknEntity(CoordinatorEntity[DknCoordinator]):
+    """Base class for all DKN Cloud NA entities.
+
+    Provides:
+    - device_info populated from the device's MAC and name.
+    - Per-device asyncio.Lock for serializing concurrent writes.
+    - Optimistic overlay: _optimistic_set() / _optimistic_get() / _optimistic_clear()
+      so entities can show a locally-set value until the coordinator refreshes.
+    - _schedule_refresh(): coalesced post-write coordinator refresh.
+    """
+
+    _attr_has_entity_name = True
+
+    def __init__(self, coordinator: DknCoordinator, mac: str) -> None:
+        super().__init__(coordinator)
+        self._mac = mac
+
+    @property
+    def _device_data(self) -> dict[str, Any]:
+        """Return raw device dict from coordinator, or empty dict if unavailable."""
+        return (self.coordinator.data or {}).get(self._mac, {})
+
+    @property
+    def device_info(self) -> DeviceInfo:
+        data = self._device_data
+        return DeviceInfo(
+            identifiers={(DOMAIN, self._mac)},
+            connections={(CONNECTION_NETWORK_MAC, self._mac)},
+            name=data.get("name") or self._mac,
+            manufacturer=MANUFACTURER,
+            sw_version=data.get("version"),
+        )
+
+    # ------------------------------------------------------------------
+    # Per-device write lock
+    # ------------------------------------------------------------------
+
+    def _get_device_lock(self) -> asyncio.Lock:
+        """Return (creating if needed) the asyncio.Lock for this device."""
+        bucket = self.hass.data.setdefault(DOMAIN, {}).setdefault(
+            self.coordinator._entry.entry_id, {}
+        )
+        locks: dict[str, asyncio.Lock] = bucket.setdefault("device_locks", {})
+        if self._mac not in locks:
+            locks[self._mac] = asyncio.Lock()
+        return locks[self._mac]
+
+    # ------------------------------------------------------------------
+    # Optimistic overlays
+    # ------------------------------------------------------------------
+
+    def _optimistic_set(self, key: str, value: Any) -> None:
+        """Store a locally-set value with a TTL timestamp."""
+        bucket = self.hass.data.setdefault(DOMAIN, {}).setdefault(
+            self.coordinator._entry.entry_id, {}
+        )
+        overlays: dict[str, dict[str, Any]] = bucket.setdefault("optimistic", {})
+        device_overlays = overlays.setdefault(self._mac, {})
+        device_overlays[key] = {"value": value, "expires": time.monotonic() + OPTIMISTIC_TTL_SEC}
+
+    def _optimistic_get(self, key: str, fallback: Any) -> Any:
+        """Return the optimistic value if still fresh, else fallback."""
+        bucket = self.hass.data.get(DOMAIN, {}).get(
+            self.coordinator._entry.entry_id, {}
+        )
+        overlays = bucket.get("optimistic", {}).get(self._mac, {})
+        entry = overlays.get(key)
+        if entry and time.monotonic() < entry["expires"]:
+            return entry["value"]
+        return fallback
+
+    def _optimistic_clear(self, key: str) -> None:
+        """Expire an optimistic overlay immediately."""
+        bucket = self.hass.data.get(DOMAIN, {}).get(
+            self.coordinator._entry.entry_id, {}
+        )
+        overlays = bucket.get("optimistic", {}).get(self._mac, {})
+        overlays.pop(key, None)
+
+    # ------------------------------------------------------------------
+    # Post-write coordinator refresh (coalesced)
+    # ------------------------------------------------------------------
+
+    def _schedule_refresh(self) -> None:
+        """Schedule a coordinator refresh after POST_WRITE_REFRESH_DELAY_SEC.
+
+        Multiple calls within the window collapse into a single refresh.
+        """
+        bucket = self.hass.data.setdefault(DOMAIN, {}).setdefault(
+            self.coordinator._entry.entry_id, {}
+        )
+        existing: asyncio.Task | None = bucket.get("pending_refresh")
+        if existing and not existing.done():
+            return
+
+        async def _do_refresh() -> None:
+            import asyncio as _asyncio
+            await _asyncio.sleep(POST_WRITE_REFRESH_DELAY_SEC)
+            await self.coordinator.async_request_refresh()
+
+        bucket["pending_refresh"] = self.hass.async_create_task(_do_refresh())