raise

esphome/core/__init__.py

@@ -523,8 +523,8 @@ class EsphomeCore:
         # Key: platform name (e.g. "sensor", "binary_sensor"), Value: count
         self.platform_counts: defaultdict[str, int] = defaultdict(int)
         # Track entity unique IDs to handle duplicates
-        # Key: (device_id, platform, object_id), Value: count of duplicates
-        self.unique_ids: dict[tuple[int, str, str], int] = {}
+        # Set of (device_id, platform, object_id) tuples
+        self.unique_ids: set[tuple[int, str, str]] = set()
         # Whether ESPHome was started in verbose mode
         self.verbose = False
         # Whether ESPHome was started in quiet mode
@@ -556,7 +556,7 @@ class EsphomeCore:
         self.loaded_integrations = set()
         self.component_ids = set()
         self.platform_counts = defaultdict(int)
-        self.unique_ids = {}
+        self.unique_ids = set()
         PIN_SCHEMA_REGISTRY.reset()
 
     @property

esphome/entity.py

@@ -99,23 +99,21 @@ async def setup_entity(var: MockObj, config: ConfigType, platform: str) -> None:
             "Entity has empty name, using '%s' as object_id base", base_object_id
         )
 
-    # Handle duplicates
     # Check for duplicates
     unique_key: tuple[int, str, str] = (device_id, platform, base_object_id)
     if unique_key in CORE.unique_ids:
-        # Found duplicate, add suffix
-        count = CORE.unique_ids[unique_key] + 1
-        CORE.unique_ids[unique_key] = count
-        object_id = f"{base_object_id}_{count}"
-        _LOGGER.info(
-            "Duplicate %s entity '%s' found. Renaming to '%s'",
-            platform,
-            config[CONF_NAME],
-            object_id,
+        # Found duplicate - fail validation
+        from esphome.config_validation import Invalid
+
+        entity_name = config[CONF_NAME] or base_object_id
+        device_prefix = f" on device '{device_name}'" if device_name else ""
+        raise Invalid(
+            f"Duplicate {platform} entity with name '{entity_name}' found{device_prefix}. "
+            f"Each entity on a device must have a unique name within its platform."
         )
     else:
-        # First occurrence
-        CORE.unique_ids[unique_key] = 1
+        # First occurrence - register it
+        CORE.unique_ids.add(unique_key)
         object_id = base_object_id
 
     add(var.set_object_id(object_id))