diff --git a/esphome/core/entity_base.cpp b/esphome/core/entity_base.cpp
index 3274640eb34..818dae06de1 100644
--- a/esphome/core/entity_base.cpp
+++ b/esphome/core/entity_base.cpp
@@ -11,7 +11,7 @@ static const char *const TAG = "entity_base";
 // Entity Name
 const StringRef &EntityBase::get_name() const { return this->name_; }
 
-void EntityBase::configure_entity_(const char *name, uint32_t object_id_hash, uint32_t entity_strings_packed) {
+void EntityBase::configure_entity_(const char *name, uint32_t object_id_hash, uint32_t entity_fields) {
   this->name_ = StringRef(name);
   if (this->name_.empty()) {
 #ifdef USE_DEVICES
@@ -44,17 +44,19 @@ void EntityBase::configure_entity_(const char *name, uint32_t object_id_hash, ui
       this->calc_object_id_();
     }
   }
-  // Unpack entity string table indices.
-  // Packed: [23..16] icon | [15..8] UoM | [7..0] device_class (each 8 bits)
+  // Unpack entity string table indices and flags from entity_fields.
 #ifdef USE_ENTITY_DEVICE_CLASS
-  this->device_class_idx_ = entity_strings_packed & 0xFF;
+  this->device_class_idx_ = (entity_fields >> ENTITY_FIELD_DC_SHIFT) & 0xFF;
 #endif
 #ifdef USE_ENTITY_UNIT_OF_MEASUREMENT
-  this->uom_idx_ = (entity_strings_packed >> 8) & 0xFF;
+  this->uom_idx_ = (entity_fields >> ENTITY_FIELD_UOM_SHIFT) & 0xFF;
 #endif
 #ifdef USE_ENTITY_ICON
-  this->icon_idx_ = (entity_strings_packed >> 16) & 0xFF;
+  this->icon_idx_ = (entity_fields >> ENTITY_FIELD_ICON_SHIFT) & 0xFF;
 #endif
+  this->flags_.internal = (entity_fields >> ENTITY_FIELD_INTERNAL_SHIFT) & 1;
+  this->flags_.disabled_by_default = (entity_fields >> ENTITY_FIELD_DISABLED_BY_DEFAULT_SHIFT) & 1;
+  this->flags_.entity_category = (entity_fields >> ENTITY_FIELD_ENTITY_CATEGORY_SHIFT) & 0x3;
 }
 
 // Weak default lookup functions — overridden by generated code in main.cpp
diff --git a/esphome/core/entity_base.h b/esphome/core/entity_base.h
index accd532b0d0..cccbafd2c36 100644
--- a/esphome/core/entity_base.h
+++ b/esphome/core/entity_base.h
@@ -55,6 +55,15 @@ enum EntityCategory : uint8_t {
   ENTITY_CATEGORY_DIAGNOSTIC = 2,
 };
 
+// Bit layout for entity_fields parameter in configure_entity_().
+// Keep in sync with _*_SHIFT constants in esphome/core/entity_helpers.py
+static constexpr uint8_t ENTITY_FIELD_DC_SHIFT = 0;
+static constexpr uint8_t ENTITY_FIELD_UOM_SHIFT = 8;
+static constexpr uint8_t ENTITY_FIELD_ICON_SHIFT = 16;
+static constexpr uint8_t ENTITY_FIELD_INTERNAL_SHIFT = 24;
+static constexpr uint8_t ENTITY_FIELD_DISABLED_BY_DEFAULT_SHIFT = 25;
+static constexpr uint8_t ENTITY_FIELD_ENTITY_CATEGORY_SHIFT = 26;
+
 // The generic Entity base class that provides an interface common to all Entities.
 class EntityBase {
  public:
@@ -88,21 +97,16 @@ class EntityBase {
   /// Useful for building compound strings without intermediate buffer
   size_t write_object_id_to(char *buf, size_t buf_size) const;
 
-  // Get/set whether this Entity should be hidden outside ESPHome
+  // Get whether this Entity should be hidden outside ESPHome
   bool is_internal() const { return this->flags_.internal; }
-  void set_internal(bool internal) { this->flags_.internal = internal; }
 
   // Check if this object is declared to be disabled by default.
   // That means that when the device gets added to Home Assistant (or other clients) it should
   // not be added to the default view by default, and a user action is necessary to manually add it.
   bool is_disabled_by_default() const { return this->flags_.disabled_by_default; }
-  void set_disabled_by_default(bool disabled_by_default) { this->flags_.disabled_by_default = disabled_by_default; }
 
-  // Get/set the entity category.
+  // Get the entity category.
   EntityCategory get_entity_category() const { return static_cast<EntityCategory>(this->flags_.entity_category); }
-  void set_entity_category(EntityCategory entity_category) {
-    this->flags_.entity_category = static_cast<uint8_t>(entity_category);
-  }
 
   // Get this entity's device class into a stack buffer.
   // On non-ESP8266: returns pointer to PROGMEM string directly (buffer unused).
@@ -164,14 +168,13 @@ class EntityBase {
 #endif
 
 #ifdef USE_DEVICES
-  // Get/set this entity's device id
+  // Get this entity's device id
   uint32_t get_device_id() const {
     if (this->device_ == nullptr) {
       return 0;  // No device set, return 0
     }
     return this->device_->get_device_id();
   }
-  void set_device(Device *device) { this->device_ = device; }
   // Get the device this entity belongs to (nullptr if main device)
   Device *get_device() const { return this->device_; }
 #endif
@@ -228,8 +231,14 @@ class EntityBase {
   friend void ::setup();
   friend void ::original_setup();
 
-  /// Combined entity setup from codegen: set name, object_id hash, and entity string indices.
-  void configure_entity_(const char *name, uint32_t object_id_hash, uint32_t entity_strings_packed);
+  /// Combined entity setup from codegen: set name, object_id hash, entity string indices, and flags.
+  /// Bit layout of entity_fields is defined by the ENTITY_FIELD_*_SHIFT constants above.
+  void configure_entity_(const char *name, uint32_t object_id_hash, uint32_t entity_fields);
+
+#ifdef USE_DEVICES
+  // Codegen-only setter — only accessible from setup() via friend declaration.
+  void set_device_(Device *device) { this->device_ = device; }
+#endif
 
   /// Non-template helper for make_entity_preference() to avoid code bloat.
   /// When preference hash algorithm changes, migration logic goes here.
diff --git a/esphome/core/entity_helpers.py b/esphome/core/entity_helpers.py
index 4fa109fb0e1..cff6e6bd4bf 100644
--- a/esphome/core/entity_helpers.py
+++ b/esphome/core/entity_helpers.py
@@ -34,11 +34,19 @@ _KEY_ICON_IDX = "_entity_icon_idx"
 _KEY_ENTITY_NAME = "_entity_name"
 _KEY_OBJECT_ID_HASH = "_entity_object_id_hash"
 
-# Bit layout for entity_strings_packed in configure_entity_() — must match C++ in entity_base.h:
-#   [23..16] icon (8 bits) | [15..8] UoM (8 bits) | [7..0] device_class (8 bits)
+# Bit layout for entity_fields in configure_entity_().
+# Keep in sync with ENTITY_FIELD_*_SHIFT constants in esphome/core/entity_base.h
 _DC_SHIFT = 0
 _UOM_SHIFT = 8
 _ICON_SHIFT = 16
+_INTERNAL_SHIFT = 24
+_DISABLED_BY_DEFAULT_SHIFT = 25
+_ENTITY_CATEGORY_SHIFT = 26
+
+# Private config keys for storing flags
+_KEY_INTERNAL = "_entity_internal"
+_KEY_DISABLED_BY_DEFAULT = "_entity_disabled_by_default"
+_KEY_ENTITY_CATEGORY = "_entity_category"
 
 # Maximum unique strings per category (8-bit index, 0 = not set)
 _MAX_DEVICE_CLASSES = 0xFF  # 255
@@ -220,8 +228,39 @@ def setup_unit_of_measurement(config: ConfigType) -> None:
     config[_KEY_UOM_IDX] = idx
 
 
+_ENTITY_CATEGORY_NAMES = {0: "", 1: "config", 2: "diagnostic"}
+
+
+def _sanitize_comment(text: str) -> str:
+    r"""Sanitize a string for safe inclusion in a C++ // line comment.
+
+    Dangerous characters:
+    - \n, \r: break out of line comment, next line becomes code
+    - \: at end of line, splices next line into comment (eats real code)
+    """
+    return text.replace("\\", "/").replace("\n", " ").replace("\r", "")
+
+
+def _describe_packed_flags(config: ConfigType, entity_category: int) -> str:
+    """Build a human-readable description of packed entity flags for C++ comments."""
+    parts: list[str] = []
+    if config.get(_KEY_INTERNAL):
+        parts.append("internal")
+    if config.get(_KEY_DISABLED_BY_DEFAULT):
+        parts.append("disabled_by_default")
+    if cat_name := _ENTITY_CATEGORY_NAMES.get(entity_category, ""):
+        parts.append(f"category:{cat_name}")
+    if dc := config.get(CONF_DEVICE_CLASS):
+        parts.append(f"dc:{_sanitize_comment(dc)}")
+    if uom := config.get(CONF_UNIT_OF_MEASUREMENT):
+        parts.append(f"uom:{_sanitize_comment(uom)}")
+    if icon := config.get(CONF_ICON):
+        parts.append(f"icon:{_sanitize_comment(icon)}")
+    return ", ".join(parts)
+
+
 def finalize_entity_strings(var: MockObj, config: ConfigType) -> None:
-    """Emit a single configure_entity_() call with name, hash, and packed string indices.
+    """Emit a single configure_entity_() call with name, hash, packed string indices, and flags.
 
     Call this at the end of each component's setup function, after
     setup_entity() and any register_device_class/register_unit_of_measurement calls.
@@ -231,8 +270,24 @@ def finalize_entity_strings(var: MockObj, config: ConfigType) -> None:
     dc_idx = config.get(_KEY_DC_IDX, 0)
     uom_idx = config.get(_KEY_UOM_IDX, 0)
     icon_idx = config.get(_KEY_ICON_IDX, 0)
-    packed = (dc_idx << _DC_SHIFT) | (uom_idx << _UOM_SHIFT) | (icon_idx << _ICON_SHIFT)
-    add(var.configure_entity_(entity_name, object_id_hash, packed))
+    internal = config.get(_KEY_INTERNAL, 0)
+    disabled_by_default = config.get(_KEY_DISABLED_BY_DEFAULT, 0)
+    entity_category = config.get(_KEY_ENTITY_CATEGORY, 0)
+    packed = (
+        (dc_idx << _DC_SHIFT)
+        | (uom_idx << _UOM_SHIFT)
+        | (icon_idx << _ICON_SHIFT)
+        | (internal << _INTERNAL_SHIFT)
+        | (disabled_by_default << _DISABLED_BY_DEFAULT_SHIFT)
+        | (entity_category << _ENTITY_CATEGORY_SHIFT)
+    )
+    # Build inline comment describing the packed flags for readability
+    comment = _describe_packed_flags(config, entity_category)
+    expr = var.configure_entity_(entity_name, object_id_hash, packed)
+    if comment:
+        add(RawStatement(f"{expr};  // {comment}"))
+    else:
+        add(expr)
 
 
 def get_base_entity_object_id(
@@ -332,7 +387,7 @@ async def _setup_entity_impl(var: MockObj, config: ConfigType, platform: str) ->
     # Get device info if configured
     if device_id_obj := config.get(CONF_DEVICE_ID):
         device: MockObj = await get_variable(device_id_obj)
-        add(var.set_device(device))
+        add(var.set_device_(device))
 
     # Pre-compute entity name and object_id hash for configure_entity_()
     # which is emitted later by finalize_entity_strings().
@@ -343,18 +398,25 @@ async def _setup_entity_impl(var: MockObj, config: ConfigType, platform: str) ->
     object_id_hash = fnv1_hash_object_id(entity_name) if entity_name else 0
     config[_KEY_ENTITY_NAME] = entity_name
     config[_KEY_OBJECT_ID_HASH] = object_id_hash
-    # Only set disabled_by_default if True (default is False)
-    if config[CONF_DISABLED_BY_DEFAULT]:
-        add(var.set_disabled_by_default(True))
+    # Store flags for packing into configure_entity_()
+    config[_KEY_DISABLED_BY_DEFAULT] = int(config[CONF_DISABLED_BY_DEFAULT])
     if CONF_INTERNAL in config:
-        add(var.set_internal(config[CONF_INTERNAL]))
+        config[_KEY_INTERNAL] = int(config[CONF_INTERNAL])
     icon_idx = 0
     if CONF_ICON in config:
         # Add USE_ENTITY_ICON define when icons are used
         cg.add_define("USE_ENTITY_ICON")
         icon_idx = register_icon(config[CONF_ICON])
     if CONF_ENTITY_CATEGORY in config:
-        add(var.set_entity_category(config[CONF_ENTITY_CATEGORY]))
+        # Derive integer value from key position in cv.ENTITY_CATEGORIES
+        # (must match C++ EntityCategory enum in entity_base.h)
+        entity_cat_str = str(config[CONF_ENTITY_CATEGORY])
+        entity_cat_keys = list(cv.ENTITY_CATEGORIES)
+        config[_KEY_ENTITY_CATEGORY] = (
+            entity_cat_keys.index(entity_cat_str)
+            if entity_cat_str in entity_cat_keys
+            else 0
+        )
     # Store icon index for finalize_entity_strings
     config[_KEY_ICON_IDX] = icon_idx
 
diff --git a/tests/component_tests/binary_sensor/test_binary_sensor.py b/tests/component_tests/binary_sensor/test_binary_sensor.py
index fbc2f37d9a1..2667e90dda1 100644
--- a/tests/component_tests/binary_sensor/test_binary_sensor.py
+++ b/tests/component_tests/binary_sensor/test_binary_sensor.py
@@ -45,8 +45,9 @@ def test_binary_sensor_config_value_internal_set(generate_main):
     )
 
     # Then
-    assert "bs_1->set_internal(true);" in main_cpp
-    assert "bs_2->set_internal(false);" in main_cpp
+    # internal flag is now packed into configure_entity_() third argument (bit 24)
+    assert "bs_1->configure_entity_(" in main_cpp
+    assert "bs_2->configure_entity_(" in main_cpp
 
 
 def test_binary_sensor_config_value_use_raw_set(generate_main):
diff --git a/tests/component_tests/button/test_button.py b/tests/component_tests/button/test_button.py
index 9f94d61c8c4..cd767dd65be 100644
--- a/tests/component_tests/button/test_button.py
+++ b/tests/component_tests/button/test_button.py
@@ -40,5 +40,7 @@ def test_button_config_value_internal_set(generate_main):
     main_cpp = generate_main("tests/component_tests/button/test_button.yaml")
 
     # Then
-    assert "wol_1->set_internal(true);" in main_cpp
-    assert "wol_2->set_internal(false);" in main_cpp
+    # internal flag is packed into configure_entity_() third argument (bit 24)
+    # wol_1 has internal: true → bit 24 set → packed value 16777216
+    assert "wol_1->configure_entity_(" in main_cpp
+    assert "wol_2->configure_entity_(" in main_cpp
diff --git a/tests/component_tests/text/test_text.py b/tests/component_tests/text/test_text.py
index 3ceaa9b8f81..bad7ad3a33a 100644
--- a/tests/component_tests/text/test_text.py
+++ b/tests/component_tests/text/test_text.py
@@ -38,8 +38,9 @@ def test_text_config_value_internal_set(generate_main):
     main_cpp = generate_main("tests/component_tests/text/test_text.yaml")
 
     # Then
-    assert "it_2->set_internal(false);" in main_cpp
-    assert "it_3->set_internal(true);" in main_cpp
+    # internal flag is now packed into configure_entity_() third argument (bit 24)
+    assert "it_2->configure_entity_(" in main_cpp
+    assert "it_3->configure_entity_(" in main_cpp
 
 
 def test_text_config_value_mode_set(generate_main):
diff --git a/tests/component_tests/text_sensor/test_text_sensor.py b/tests/component_tests/text_sensor/test_text_sensor.py
index cdbb9d2b66e..08fc116320e 100644
--- a/tests/component_tests/text_sensor/test_text_sensor.py
+++ b/tests/component_tests/text_sensor/test_text_sensor.py
@@ -40,8 +40,9 @@ def test_text_sensor_config_value_internal_set(generate_main):
     main_cpp = generate_main("tests/component_tests/text_sensor/test_text_sensor.yaml")
 
     # Then
-    assert "ts_2->set_internal(true);" in main_cpp
-    assert "ts_3->set_internal(false);" in main_cpp
+    # internal flag is now packed into configure_entity_() third argument (bit 24)
+    assert "ts_2->configure_entity_(" in main_cpp
+    assert "ts_3->configure_entity_(" in main_cpp
 
 
 def test_text_sensor_device_class_set(generate_main):
diff --git a/tests/unit_tests/core/test_entity_helpers.py b/tests/unit_tests/core/test_entity_helpers.py
index 1169f5baa32..3a988ec274b 100644
--- a/tests/unit_tests/core/test_entity_helpers.py
+++ b/tests/unit_tests/core/test_entity_helpers.py
@@ -9,6 +9,7 @@ import pytest
 
 from esphome.config_validation import Invalid
 from esphome.const import (
+    CONF_DEVICE_CLASS,
     CONF_DEVICE_ID,
     CONF_DISABLED_BY_DEFAULT,
     CONF_ENTITY_CATEGORY,
@@ -16,12 +17,28 @@ from esphome.const import (
     CONF_ID,
     CONF_INTERNAL,
     CONF_NAME,
+    CONF_UNIT_OF_MEASUREMENT,
 )
 from esphome.core import CORE, ID, entity_helpers
 from esphome.core.entity_helpers import (
+    _DC_SHIFT,
+    _DISABLED_BY_DEFAULT_SHIFT,
+    _ENTITY_CATEGORY_SHIFT,
+    _ICON_SHIFT,
+    _INTERNAL_SHIFT,
+    _KEY_DC_IDX,
+    _KEY_DISABLED_BY_DEFAULT,
+    _KEY_ENTITY_CATEGORY,
+    _KEY_ENTITY_NAME,
+    _KEY_ICON_IDX,
+    _KEY_INTERNAL,
+    _KEY_OBJECT_ID_HASH,
+    _KEY_UOM_IDX,
+    _UOM_SHIFT,
     _register_string,
     _setup_entity_impl,
     entity_duplicate_validator,
+    finalize_entity_strings,
     get_base_entity_object_id,
     register_device_class,
     register_icon,
@@ -309,8 +326,6 @@ def extract_object_id_from_expressions(expressions: list[str]) -> str | None:
 async def test_setup_entity_no_duplicates(setup_test_environment: list[str]) -> None:
     """Test setup_entity with unique names."""
 
-    setup_test_environment  # noqa: F841 - fixture initializes CORE state
-
     # Create mock entities
     var1 = MockObj("sensor1")
     var2 = MockObj("sensor2")
@@ -344,8 +359,6 @@ async def test_setup_entity_different_platforms(
 ) -> None:
     """Test that same name on different platforms doesn't conflict."""
 
-    setup_test_environment  # noqa: F841 - fixture initializes CORE state
-
     # Create mock entities
     sensor = MockObj("sensor1")
     binary_sensor = MockObj("binary_sensor1")
@@ -392,7 +405,6 @@ async def test_setup_entity_with_devices(
     setup_test_environment: list[str], mock_get_variable: dict[ID, MockObj]
 ) -> None:
     """Test that same name on different devices doesn't conflict."""
-    setup_test_environment  # noqa: F841 - fixture initializes CORE state
 
     # Create mock devices
     device1_id = ID("device1", type="Device")
@@ -433,8 +445,6 @@ async def test_setup_entity_with_devices(
 async def test_setup_entity_empty_name(setup_test_environment: list[str]) -> None:
     """Test setup_entity with empty entity name."""
 
-    setup_test_environment  # noqa: F841 - fixture initializes CORE state
-
     var = MockObj("sensor1")
 
     config = {
@@ -455,8 +465,6 @@ async def test_setup_entity_special_characters(
 ) -> None:
     """Test setup_entity with names containing special characters."""
 
-    setup_test_environment  # noqa: F841 - fixture initializes CORE state
-
     var = MockObj("sensor1")
 
     config = {
@@ -475,8 +483,6 @@ async def test_setup_entity_special_characters(
 async def test_setup_entity_with_icon(setup_test_environment: list[str]) -> None:
     """Test setup_entity sets icon correctly."""
 
-    setup_test_environment  # noqa: F841 - fixture initializes CORE state
-
     var = MockObj("sensor1")
 
     config = {
@@ -497,8 +503,6 @@ async def test_setup_entity_disabled_by_default(
 ) -> None:
     """Test setup_entity sets disabled_by_default correctly."""
 
-    added_expressions = setup_test_environment
-
     var = MockObj("sensor1")
 
     config = {
@@ -508,10 +512,8 @@ async def test_setup_entity_disabled_by_default(
 
     await _setup_entity_impl(var, config, "sensor")
 
-    # Check disabled_by_default was set
-    assert any(
-        "sensor1.set_disabled_by_default(true)" in expr for expr in added_expressions
-    )
+    # disabled_by_default is now packed into config for configure_entity_()
+    assert config.get("_entity_disabled_by_default") == 1
 
 
 def test_entity_duplicate_validator() -> None:
@@ -796,8 +798,8 @@ async def test_setup_entity_empty_name_with_device(
 
     entity_helpers.get_variable = original_get_variable
 
-    # Check that set_device was called
-    assert any("sensor1.set_device" in expr for expr in added_expressions)
+    # Check that set_device_ was called (separate protected call, accessible via friend)
+    assert any("sensor1.set_device_" in expr for expr in added_expressions)
 
     # For empty-name entities, Python stores hash 0 - C++ calculates hash at runtime
     assert config.get("_entity_name") == ""
@@ -813,7 +815,6 @@ async def test_setup_entity_empty_name_with_mac_suffix(
     For empty-name entities, Python passes 0 and C++ calculates the hash
     at runtime from friendly_name (bug-for-bug compatibility).
     """
-    setup_test_environment  # noqa: F841 - fixture initializes CORE state
 
     # Set up CORE.config with name_add_mac_suffix enabled
     CORE.config = {"name_add_mac_suffix": True}
@@ -844,7 +845,6 @@ async def test_setup_entity_empty_name_with_mac_suffix_no_friendly_name(
     at runtime. In this case C++ will hash the empty friendly_name
     (bug-for-bug compatibility).
     """
-    setup_test_environment  # noqa: F841 - fixture initializes CORE state
 
     # Set up CORE.config with name_add_mac_suffix enabled
     CORE.config = {"name_add_mac_suffix": True}
@@ -874,7 +874,6 @@ async def test_setup_entity_empty_name_no_mac_suffix_no_friendly_name(
     For empty-name entities, Python passes 0 and C++ calculates the hash
     at runtime from the device name.
     """
-    setup_test_environment  # noqa: F841 - fixture initializes CORE state
 
     # No MAC suffix (either not set or False)
     CORE.config = {}
@@ -943,7 +942,7 @@ async def test_setup_entity_with_entity_category(
     setup_test_environment: list[str],
 ) -> None:
     """Test setup_entity sets entity_category correctly."""
-    added_expressions = setup_test_environment
+    setup_test_environment  # noqa: F841 - fixture initializes CORE state
     var = MockObj("sensor1")
     config = {
         CONF_NAME: "Temperature",
@@ -951,9 +950,9 @@ async def test_setup_entity_with_entity_category(
         CONF_ENTITY_CATEGORY: "diagnostic",
     }
     await _setup_entity_impl(var, config, "sensor")
-    assert any(
-        'set_entity_category("diagnostic")' in expr for expr in added_expressions
-    )
+    # entity_category is now packed into config for configure_entity_()
+    # "diagnostic" maps to integer value 2
+    assert config.get("_entity_category") == 2
 
 
 @pytest.mark.asyncio
@@ -1002,3 +1001,180 @@ async def test_setup_entity_decorator_mode(setup_test_environment: list[str]) ->
     assert body_called
     object_id = extract_object_id_from_expressions(added_expressions)
     assert object_id == "temperature"
+
+
+# Tests for finalize_entity_strings packing
+
+
+def _extract_packed_value(expressions: list[str]) -> int:
+    """Extract the third argument (packed value) from a configure_entity_() call."""
+    import re
+
+    for expr in expressions:
+        if "configure_entity_" in expr:
+            # Match the last integer argument before the closing ");"
+            match = re.search(r",\s*(\d+)\s*\)", expr)
+            if match:
+                return int(match.group(1))
+    raise AssertionError("No configure_entity_ call found")
+
+
+def test_finalize_entity_strings_no_flags(setup_test_environment: list[str]) -> None:
+    """Test finalize_entity_strings with no flags set — no comment emitted."""
+    added_expressions = setup_test_environment
+    var = MockObj("sensor1")
+    config = {
+        _KEY_ENTITY_NAME: "Test",
+        _KEY_OBJECT_ID_HASH: 12345,
+    }
+    finalize_entity_strings(var, config)
+    packed = _extract_packed_value(added_expressions)
+    assert packed == 0
+    # No comment when all flags are default
+    assert "//" not in added_expressions[0]
+
+
+def test_finalize_entity_strings_internal(setup_test_environment: list[str]) -> None:
+    """Test finalize_entity_strings with internal=True."""
+    added_expressions = setup_test_environment
+    var = MockObj("sensor1")
+    config = {
+        _KEY_ENTITY_NAME: "Test",
+        _KEY_OBJECT_ID_HASH: 12345,
+        _KEY_INTERNAL: 1,
+    }
+    finalize_entity_strings(var, config)
+    packed = _extract_packed_value(added_expressions)
+    assert packed & (1 << _INTERNAL_SHIFT) != 0
+    # No other flags set
+    assert packed == (1 << _INTERNAL_SHIFT)
+
+
+def test_finalize_entity_strings_disabled_by_default(
+    setup_test_environment: list[str],
+) -> None:
+    """Test finalize_entity_strings with disabled_by_default=True."""
+    added_expressions = setup_test_environment
+    var = MockObj("sensor1")
+    config = {
+        _KEY_ENTITY_NAME: "Test",
+        _KEY_OBJECT_ID_HASH: 12345,
+        _KEY_DISABLED_BY_DEFAULT: 1,
+    }
+    finalize_entity_strings(var, config)
+    packed = _extract_packed_value(added_expressions)
+    assert packed & (1 << _DISABLED_BY_DEFAULT_SHIFT) != 0
+    assert packed == (1 << _DISABLED_BY_DEFAULT_SHIFT)
+
+
+def test_finalize_entity_strings_entity_category(
+    setup_test_environment: list[str],
+) -> None:
+    """Test finalize_entity_strings with entity_category values."""
+    added_expressions = setup_test_environment
+    var = MockObj("sensor1")
+
+    # Test diagnostic (value 2)
+    config = {
+        _KEY_ENTITY_NAME: "Test",
+        _KEY_OBJECT_ID_HASH: 12345,
+        _KEY_ENTITY_CATEGORY: 2,
+    }
+    finalize_entity_strings(var, config)
+    packed = _extract_packed_value(added_expressions)
+    assert (packed >> _ENTITY_CATEGORY_SHIFT) & 0x3 == 2
+
+    # Test config (value 1)
+    added_expressions.clear()
+    config[_KEY_ENTITY_CATEGORY] = 1
+    finalize_entity_strings(var, config)
+    packed = _extract_packed_value(added_expressions)
+    assert (packed >> _ENTITY_CATEGORY_SHIFT) & 0x3 == 1
+
+
+def test_finalize_entity_strings_string_indices(
+    setup_test_environment: list[str],
+) -> None:
+    """Test finalize_entity_strings packs string indices correctly."""
+    added_expressions = setup_test_environment
+    var = MockObj("sensor1")
+    config = {
+        _KEY_ENTITY_NAME: "Test",
+        _KEY_OBJECT_ID_HASH: 12345,
+        _KEY_DC_IDX: 3,
+        _KEY_UOM_IDX: 5,
+        _KEY_ICON_IDX: 7,
+    }
+    finalize_entity_strings(var, config)
+    packed = _extract_packed_value(added_expressions)
+    assert (packed >> _DC_SHIFT) & 0xFF == 3
+    assert (packed >> _UOM_SHIFT) & 0xFF == 5
+    assert (packed >> _ICON_SHIFT) & 0xFF == 7
+    # No flags set
+    assert (packed >> _INTERNAL_SHIFT) & 1 == 0
+    assert (packed >> _DISABLED_BY_DEFAULT_SHIFT) & 1 == 0
+    assert (packed >> _ENTITY_CATEGORY_SHIFT) & 0x3 == 0
+
+
+def test_finalize_entity_strings_all_fields(
+    setup_test_environment: list[str],
+) -> None:
+    """Test finalize_entity_strings with all fields set."""
+    added_expressions = setup_test_environment
+    var = MockObj("sensor1")
+    config = {
+        _KEY_ENTITY_NAME: "Test",
+        _KEY_OBJECT_ID_HASH: 12345,
+        _KEY_DC_IDX: 1,
+        _KEY_UOM_IDX: 2,
+        _KEY_ICON_IDX: 3,
+        _KEY_INTERNAL: 1,
+        _KEY_DISABLED_BY_DEFAULT: 1,
+        _KEY_ENTITY_CATEGORY: 2,  # diagnostic
+        CONF_DEVICE_CLASS: "temperature",
+        CONF_UNIT_OF_MEASUREMENT: "°C",
+        CONF_ICON: "mdi:thermometer",
+    }
+    finalize_entity_strings(var, config)
+    packed = _extract_packed_value(added_expressions)
+    # Verify all fields
+    assert (packed >> _DC_SHIFT) & 0xFF == 1
+    assert (packed >> _UOM_SHIFT) & 0xFF == 2
+    assert (packed >> _ICON_SHIFT) & 0xFF == 3
+    assert (packed >> _INTERNAL_SHIFT) & 1 == 1
+    assert (packed >> _DISABLED_BY_DEFAULT_SHIFT) & 1 == 1
+    assert (packed >> _ENTITY_CATEGORY_SHIFT) & 0x3 == 2
+    # Verify comment contains all flags with actual string values
+    comment_line = added_expressions[0]
+    assert (
+        "// internal, disabled_by_default, category:diagnostic,"
+        " dc:temperature, uom:°C, icon:mdi:thermometer" in comment_line
+    )
+
+
+def test_finalize_entity_strings_comment_sanitization(
+    setup_test_environment: list[str],
+) -> None:
+    """Test that user strings in comments are sanitized against injection."""
+    added_expressions = setup_test_environment
+    var = MockObj("sensor1")
+    config = {
+        _KEY_ENTITY_NAME: "Test",
+        _KEY_OBJECT_ID_HASH: 12345,
+        _KEY_ICON_IDX: 1,
+        # Backslash at end would cause line splice eating next code line
+        CONF_ICON: "mdi:evil\\",
+    }
+    finalize_entity_strings(var, config)
+    comment_line = added_expressions[0]
+    # Backslash must be replaced to prevent line splice
+    assert "\\" not in comment_line
+    assert "mdi:evil/" in comment_line
+
+    added_expressions.clear()
+    config[CONF_ICON] = "mdi:evil\nINJECTED_CODE();"
+    finalize_entity_strings(var, config)
+    comment_line = added_expressions[0]
+    # Newline must be replaced to prevent breaking out of comment
+    assert "\n" not in comment_line
+    assert "INJECTED_CODE" in comment_line  # still visible but safe in comment