diff --git a/custom_components/poollab/__init__.py b/custom_components/poollab/__init__.py
index 8f8d488..bc41bf3 100644
--- a/custom_components/poollab/__init__.py
+++ b/custom_components/poollab/__init__.py
@@ -47,8 +47,17 @@ async def _async_update_poollab(self):
             # Raising ConfigEntryAuthFailed will cancel future updates
             # and start a config flow with SOURCE_REAUTH (async_step_reauth)
             raise ConfigEntryAuthFailed from err
+        except TimeoutError as err:
+            raise UpdateFailed(
+                "PoolLab cloud request timed out; "
+                "no new measurements were fetched. Home Assistant will retry automatically."
+            ) from err
         except Exception as err:
-            raise UpdateFailed(f"Unknown error communicating with API: {err}") from err
+            detail = str(err).strip() or "no error message provided"
+            raise UpdateFailed(
+                f"PoolLab API request failed ({type(err).__name__}): {detail}. "
+                "Home Assistant will retry automatically."
+            ) from err
 
     def add_entity_ref(self, entity) -> None:
         """Add an entity reference to the coordinator."""
diff --git a/tests/test_coordinator_errors.py b/tests/test_coordinator_errors.py
new file mode 100644
index 0000000..b25061e
--- /dev/null
+++ b/tests/test_coordinator_errors.py
@@ -0,0 +1,65 @@
+"""Regression tests for PoolLab API error messages."""
+
+import asyncio
+from unittest.mock import AsyncMock, Mock
+
+import pytest
+
+from homeassistant.helpers.update_coordinator import UpdateFailed
+
+from custom_components.poollab import PoolLabCoordinator
+from custom_components.poollab.poollab import PoolLabApi
+
+
+@pytest.mark.parametrize(
+    ("error", "expected_message"),
+    [
+        (
+            TimeoutError(),
+            "PoolLab cloud request timed out; "
+            "no new measurements were fetched. Home Assistant will retry automatically.",
+        ),
+        (
+            RuntimeError(),
+            "PoolLab API request failed (RuntimeError): no error message provided. "
+            "Home Assistant will retry automatically.",
+        ),
+        (
+            ConnectionError("Connection lost"),
+            "PoolLab API request failed (ConnectionError): Connection lost. "
+            "Home Assistant will retry automatically.",
+        ),
+    ],
+)
+async def test_api_failure_has_useful_message(hass, error, expected_message):
+    """Report the failure type even when the exception message is empty."""
+    api = Mock(spec=PoolLabApi)
+    api.request = AsyncMock(side_effect=error)
+    coordinator = PoolLabCoordinator(hass, api)
+
+    with pytest.raises(UpdateFailed) as exc_info:
+        await coordinator._async_update_poollab()
+
+    assert str(exc_info.value) == expected_message
+    assert exc_info.value.__cause__ is error
+    api.request.assert_awaited_once()
+
+
+async def test_request_deadline_has_timeout_message(hass, monkeypatch):
+    """An expired request deadline must use the timeout-specific message."""
+    timeout = asyncio.timeout
+    monkeypatch.setattr(
+        "custom_components.poollab.asyncio.timeout", lambda _: timeout(0)
+    )
+
+    async def pending_request():
+        await asyncio.sleep(0)
+
+    api = Mock(spec=PoolLabApi)
+    api.request = AsyncMock(side_effect=pending_request)
+    coordinator = PoolLabCoordinator(hass, api)
+
+    with pytest.raises(UpdateFailed, match="cloud request timed out;"):
+        await coordinator._async_update_poollab()
+
+    assert api.request.await_count == 1