fixes

esphome/cpp_helpers.py

@@ -17,7 +17,7 @@ from esphome.core import CORE, ID, coroutine
 from esphome.coroutine import FakeAwaitable
 from esphome.cpp_generator import MockObj, add, get_variable
 from esphome.cpp_types import App
-from esphome.helpers import sanitize, snake_case
+from esphome.entity import get_base_entity_object_id
 from esphome.types import ConfigFragmentType, ConfigType
 from esphome.util import Registry, RegistryEntry
 
@@ -122,19 +122,14 @@ async def setup_entity(var: MockObj, config: ConfigType, platform: str) -> None:
 
     add(var.set_name(config[CONF_NAME]))
 
-    # Calculate base object_id
-    base_object_id: str
+    # Calculate base object_id using the same logic as C++
+    # This must match the C++ behavior in esphome/core/entity_base.cpp
+    base_object_id = get_base_entity_object_id(config[CONF_NAME], CORE.friendly_name)
+
     if not config[CONF_NAME]:
-        # Use the friendly name if available, otherwise use the device name
-        if CORE.friendly_name:
-            base_object_id = sanitize(snake_case(CORE.friendly_name))
-        else:
-            base_object_id = sanitize(snake_case(CORE.name))
         _LOGGER.debug(
             "Entity has empty name, using '%s' as object_id base", base_object_id
         )
-    else:
-        base_object_id = sanitize(snake_case(config[CONF_NAME]))
 
     # Handle duplicates
     # Check for duplicates
@@ -156,6 +151,12 @@ async def setup_entity(var: MockObj, config: ConfigType, platform: str) -> None:
         object_id = base_object_id
 
     add(var.set_object_id(object_id))
+    _LOGGER.debug(
+        "Setting object_id '%s' for entity '%s' on platform '%s'",
+        object_id,
+        config[CONF_NAME],
+        platform,
+    )
     add(var.set_disabled_by_default(config[CONF_DISABLED_BY_DEFAULT]))
     if CONF_INTERNAL in config:
         add(var.set_internal(config[CONF_INTERNAL]))

esphome/entity.py

@@ -0,0 +1,41 @@
+"""Entity-related helper functions."""
+
+from esphome.core import CORE
+from esphome.helpers import sanitize, snake_case
+
+
+def get_base_entity_object_id(name: str, friendly_name: str | None) -> str:
+    """Calculate the base object ID for an entity that will be set via set_object_id().
+
+    This function calculates what object_id_c_str_ should be set to in C++.
+
+    The C++ EntityBase::get_object_id() (entity_base.cpp lines 38-49) works as:
+    - If !has_own_name && is_name_add_mac_suffix_enabled():
+        return str_sanitize(str_snake_case(App.get_friendly_name()))  // Dynamic
+    - Else:
+        return object_id_c_str_ ?? ""  // What we set via set_object_id()
+
+    Since we're calculating what to pass to set_object_id(), we always need to
+    generate the object_id the same way, regardless of name_add_mac_suffix setting.
+
+    Args:
+        name: The entity name (empty string if no name)
+        friendly_name: The friendly name from CORE.friendly_name
+
+    Returns:
+        The base object ID to use for duplicate checking and to pass to set_object_id()
+    """
+
+    if name:
+        # Entity has its own name (has_own_name will be true)
+        base_str = name
+    elif friendly_name:
+        # Entity has empty name (has_own_name will be false)
+        # Calculate what the object_id should be
+        # C++ uses App.get_friendly_name() which returns friendly_name or device name
+        base_str = friendly_name
+    else:
+        # Fallback to device name
+        base_str = CORE.name
+
+    return sanitize(snake_case(base_str))