Merge branch 'dev' of https://github.com/esphome/esphome into usb-uart

esphome/automation.py

@@ -16,7 +16,12 @@ from esphome.const import (
     CONF_UPDATE_INTERVAL,
 )
 from esphome.core import ID
-from esphome.cpp_generator import MockObj, MockObjClass, TemplateArgsType
+from esphome.cpp_generator import (
+    LambdaExpression,
+    MockObj,
+    MockObjClass,
+    TemplateArgsType,
+)
 from esphome.schema_extractors import SCHEMA_EXTRACT, schema_extractor
 from esphome.types import ConfigType
 from esphome.util import Registry
@@ -87,6 +92,7 @@ def validate_potentially_or_condition(value):
 
 DelayAction = cg.esphome_ns.class_("DelayAction", Action, cg.Component)
 LambdaAction = cg.esphome_ns.class_("LambdaAction", Action)
+StatelessLambdaAction = cg.esphome_ns.class_("StatelessLambdaAction", Action)
 IfAction = cg.esphome_ns.class_("IfAction", Action)
 WhileAction = cg.esphome_ns.class_("WhileAction", Action)
 RepeatAction = cg.esphome_ns.class_("RepeatAction", Action)
@@ -97,9 +103,40 @@ ResumeComponentAction = cg.esphome_ns.class_("ResumeComponentAction", Action)
 Automation = cg.esphome_ns.class_("Automation")
 
 LambdaCondition = cg.esphome_ns.class_("LambdaCondition", Condition)
+StatelessLambdaCondition = cg.esphome_ns.class_("StatelessLambdaCondition", Condition)
 ForCondition = cg.esphome_ns.class_("ForCondition", Condition, cg.Component)
 
 
+def new_lambda_pvariable(
+    id_obj: ID,
+    lambda_expr: LambdaExpression,
+    stateless_class: MockObjClass,
+    template_arg: cg.TemplateArguments | None = None,
+) -> MockObj:
+    """Create Pvariable for lambda, using stateless class if applicable.
+
+    Combines ID selection and Pvariable creation in one call. For stateless
+    lambdas (empty capture), uses function pointer instead of std::function.
+
+    Args:
+        id_obj: The ID object (action_id, condition_id, or filter_id)
+        lambda_expr: The lambda expression object
+        stateless_class: The stateless class to use for stateless lambdas
+        template_arg: Optional template arguments (for actions/conditions)
+
+    Returns:
+        The created Pvariable
+    """
+    # For stateless lambdas, use function pointer instead of std::function
+    if lambda_expr.capture == "":
+        id_obj = id_obj.copy()
+        id_obj.type = stateless_class
+
+    if template_arg is not None:
+        return cg.new_Pvariable(id_obj, template_arg, lambda_expr)
+    return cg.new_Pvariable(id_obj, lambda_expr)
+
+
 def validate_automation(extra_schema=None, extra_validators=None, single=False):
     if extra_schema is None:
         extra_schema = {}
@@ -240,7 +277,9 @@ async def lambda_condition_to_code(
     args: TemplateArgsType,
 ) -> MockObj:
     lambda_ = await cg.process_lambda(config, args, return_type=bool)
-    return cg.new_Pvariable(condition_id, template_arg, lambda_)
+    return new_lambda_pvariable(
+        condition_id, lambda_, StatelessLambdaCondition, template_arg
+    )
 
 
 @register_condition(
@@ -406,7 +445,7 @@ async def lambda_action_to_code(
     args: TemplateArgsType,
 ) -> MockObj:
     lambda_ = await cg.process_lambda(config, args, return_type=cg.void)
-    return cg.new_Pvariable(action_id, template_arg, lambda_)
+    return new_lambda_pvariable(action_id, lambda_, StatelessLambdaAction, template_arg)
 
 
 @register_action(

esphome/codegen.py

@@ -62,6 +62,7 @@ from esphome.cpp_types import (  # noqa: F401
     EntityBase,
     EntityCategory,
     ESPTime,
+    FixedVector,
     GPIOPin,
     InternalGPIOPin,
     JsonObject,

esphome/components/api/__init__.py

@@ -71,10 +71,12 @@ SERVICE_ARG_NATIVE_TYPES = {
     "int": cg.int32,
     "float": float,
     "string": cg.std_string,
-    "bool[]": cg.std_vector.template(bool),
+    "bool[]": cg.FixedVector.template(bool).operator("const").operator("ref"),
-    "int[]": cg.std_vector.template(cg.int32),
+    "int[]": cg.FixedVector.template(cg.int32).operator("const").operator("ref"),
-    "float[]": cg.std_vector.template(float),
+    "float[]": cg.FixedVector.template(float).operator("const").operator("ref"),
-    "string[]": cg.std_vector.template(cg.std_string),
+    "string[]": cg.FixedVector.template(cg.std_string)
+    .operator("const")
+    .operator("ref"),
 }
 CONF_ENCRYPTION = "encryption"
 CONF_BATCH_DELAY = "batch_delay"
@@ -258,6 +260,10 @@ async def to_code(config):
     if config.get(CONF_ACTIONS) or config[CONF_CUSTOM_SERVICES]:
         cg.add_define("USE_API_SERVICES")
 
+    # Set USE_API_CUSTOM_SERVICES if external components need dynamic service registration
+    if config[CONF_CUSTOM_SERVICES]:
+        cg.add_define("USE_API_CUSTOM_SERVICES")
+
     if config[CONF_HOMEASSISTANT_SERVICES]:
         cg.add_define("USE_API_HOMEASSISTANT_SERVICES")
 
@@ -265,6 +271,8 @@ async def to_code(config):
         cg.add_define("USE_API_HOMEASSISTANT_STATES")
 
     if actions := config.get(CONF_ACTIONS, []):
+        # Collect all triggers first, then register all at once with initializer_list
+        triggers: list[cg.Pvariable] = []
         for conf in actions:
             template_args = []
             func_args = []
@@ -278,8 +286,10 @@ async def to_code(config):
             trigger = cg.new_Pvariable(
                 conf[CONF_TRIGGER_ID], templ, conf[CONF_ACTION], service_arg_names
             )
-            cg.add(var.register_user_service(trigger))
+            triggers.append(trigger)
             await automation.build_automation(trigger, func_args, conf)
+        # Register all services at once - single allocation, no reallocations
+        cg.add(var.initialize_user_services(triggers))
 
     if CONF_ON_CLIENT_CONNECTED in config:
         cg.add_define("USE_API_CLIENT_CONNECTED_TRIGGER")

esphome/components/api/api_server.h

@@ -125,8 +125,14 @@ class APIServer : public Component, public Controller {
 #endif  // USE_API_HOMEASSISTANT_ACTION_RESPONSES
 #endif  // USE_API_HOMEASSISTANT_SERVICES
 #ifdef USE_API_SERVICES
+  void initialize_user_services(std::initializer_list<UserServiceDescriptor *> services) {
+    this->user_services_.assign(services);
+  }
+#ifdef USE_API_CUSTOM_SERVICES
+  // Only compile push_back method when custom_services: true (external components)
   void register_user_service(UserServiceDescriptor *descriptor) { this->user_services_.push_back(descriptor); }
 #endif
+#endif
 #ifdef USE_HOMEASSISTANT_TIME
   void request_time();
 #endif

esphome/components/api/custom_api_device.h

@@ -53,8 +53,14 @@ class CustomAPIDevice {
   template<typename T, typename... Ts>
   void register_service(void (T::*callback)(Ts...), const std::string &name,
                         const std::array<std::string, sizeof...(Ts)> &arg_names) {
+#ifdef USE_API_CUSTOM_SERVICES
     auto *service = new CustomAPIDeviceService<T, Ts...>(name, arg_names, (T *) this, callback);  // NOLINT
     global_api_server->register_user_service(service);
+#else
+    static_assert(
+        sizeof(T) == 0,
+        "register_service() requires 'custom_services: true' in the 'api:' section of your YAML configuration");
+#endif
   }
 #else
   template<typename T, typename... Ts>
@@ -86,8 +92,14 @@ class CustomAPIDevice {
    */
 #ifdef USE_API_SERVICES
   template<typename T> void register_service(void (T::*callback)(), const std::string &name) {
+#ifdef USE_API_CUSTOM_SERVICES
     auto *service = new CustomAPIDeviceService<T>(name, {}, (T *) this, callback);  // NOLINT
     global_api_server->register_user_service(service);
+#else
+    static_assert(
+        sizeof(T) == 0,
+        "register_service() requires 'custom_services: true' in the 'api:' section of your YAML configuration");
+#endif
   }
 #else
   template<typename T> void register_service(void (T::*callback)(), const std::string &name) {

esphome/components/api/user_services.cpp

@@ -11,23 +11,58 @@ template<> int32_t get_execute_arg_value<int32_t>(const ExecuteServiceArgument &
 }
 template<> float get_execute_arg_value<float>(const ExecuteServiceArgument &arg) { return arg.float_; }
 template<> std::string get_execute_arg_value<std::string>(const ExecuteServiceArgument &arg) { return arg.string_; }
+
+// Legacy std::vector versions for external components using custom_api_device.h - optimized with reserve
 template<> std::vector<bool> get_execute_arg_value<std::vector<bool>>(const ExecuteServiceArgument &arg) {
-  return std::vector<bool>(arg.bool_array.begin(), arg.bool_array.end());
+  std::vector<bool> result;
+  result.reserve(arg.bool_array.size());
+  result.insert(result.end(), arg.bool_array.begin(), arg.bool_array.end());
+  return result;
 }
 template<> std::vector<int32_t> get_execute_arg_value<std::vector<int32_t>>(const ExecuteServiceArgument &arg) {
-  return std::vector<int32_t>(arg.int_array.begin(), arg.int_array.end());
+  std::vector<int32_t> result;
+  result.reserve(arg.int_array.size());
+  result.insert(result.end(), arg.int_array.begin(), arg.int_array.end());
+  return result;
 }
 template<> std::vector<float> get_execute_arg_value<std::vector<float>>(const ExecuteServiceArgument &arg) {
-  return std::vector<float>(arg.float_array.begin(), arg.float_array.end());
+  std::vector<float> result;
+  result.reserve(arg.float_array.size());
+  result.insert(result.end(), arg.float_array.begin(), arg.float_array.end());
+  return result;
 }
 template<> std::vector<std::string> get_execute_arg_value<std::vector<std::string>>(const ExecuteServiceArgument &arg) {
-  return std::vector<std::string>(arg.string_array.begin(), arg.string_array.end());
+  std::vector<std::string> result;
+  result.reserve(arg.string_array.size());
+  result.insert(result.end(), arg.string_array.begin(), arg.string_array.end());
+  return result;
+}
+
+// New FixedVector const reference versions for YAML-generated services - zero-copy
+template<>
+const FixedVector<bool> &get_execute_arg_value<const FixedVector<bool> &>(const ExecuteServiceArgument &arg) {
+  return arg.bool_array;
+}
+template<>
+const FixedVector<int32_t> &get_execute_arg_value<const FixedVector<int32_t> &>(const ExecuteServiceArgument &arg) {
+  return arg.int_array;
+}
+template<>
+const FixedVector<float> &get_execute_arg_value<const FixedVector<float> &>(const ExecuteServiceArgument &arg) {
+  return arg.float_array;
+}
+template<>
+const FixedVector<std::string> &get_execute_arg_value<const FixedVector<std::string> &>(
+    const ExecuteServiceArgument &arg) {
+  return arg.string_array;
 }
 
 template<> enums::ServiceArgType to_service_arg_type<bool>() { return enums::SERVICE_ARG_TYPE_BOOL; }
 template<> enums::ServiceArgType to_service_arg_type<int32_t>() { return enums::SERVICE_ARG_TYPE_INT; }
 template<> enums::ServiceArgType to_service_arg_type<float>() { return enums::SERVICE_ARG_TYPE_FLOAT; }
 template<> enums::ServiceArgType to_service_arg_type<std::string>() { return enums::SERVICE_ARG_TYPE_STRING; }
+
+// Legacy std::vector versions for external components using custom_api_device.h
 template<> enums::ServiceArgType to_service_arg_type<std::vector<bool>>() { return enums::SERVICE_ARG_TYPE_BOOL_ARRAY; }
 template<> enums::ServiceArgType to_service_arg_type<std::vector<int32_t>>() {
   return enums::SERVICE_ARG_TYPE_INT_ARRAY;
@@ -39,4 +74,18 @@ template<> enums::ServiceArgType to_service_arg_type<std::vector<std::string>>()
   return enums::SERVICE_ARG_TYPE_STRING_ARRAY;
 }
 
+// New FixedVector const reference versions for YAML-generated services
+template<> enums::ServiceArgType to_service_arg_type<const FixedVector<bool> &>() {
+  return enums::SERVICE_ARG_TYPE_BOOL_ARRAY;
+}
+template<> enums::ServiceArgType to_service_arg_type<const FixedVector<int32_t> &>() {
+  return enums::SERVICE_ARG_TYPE_INT_ARRAY;
+}
+template<> enums::ServiceArgType to_service_arg_type<const FixedVector<float> &>() {
+  return enums::SERVICE_ARG_TYPE_FLOAT_ARRAY;
+}
+template<> enums::ServiceArgType to_service_arg_type<const FixedVector<std::string> &>() {
+  return enums::SERVICE_ARG_TYPE_STRING_ARRAY;
+}
+
 }  // namespace esphome::api

esphome/components/binary_sensor/__init__.py

@@ -155,6 +155,7 @@ DelayedOffFilter = binary_sensor_ns.class_("DelayedOffFilter", Filter, cg.Compon
 InvertFilter = binary_sensor_ns.class_("InvertFilter", Filter)
 AutorepeatFilter = binary_sensor_ns.class_("AutorepeatFilter", Filter, cg.Component)
 LambdaFilter = binary_sensor_ns.class_("LambdaFilter", Filter)
+StatelessLambdaFilter = binary_sensor_ns.class_("StatelessLambdaFilter", Filter)
 SettleFilter = binary_sensor_ns.class_("SettleFilter", Filter, cg.Component)
 
 _LOGGER = getLogger(__name__)
@@ -299,7 +300,7 @@ async def lambda_filter_to_code(config, filter_id):
     lambda_ = await cg.process_lambda(
         config, [(bool, "x")], return_type=cg.optional.template(bool)
     )
-    return cg.new_Pvariable(filter_id, lambda_)
+    return automation.new_lambda_pvariable(filter_id, lambda_, StatelessLambdaFilter)
 
 
 @register_filter(

esphome/components/binary_sensor/filter.h

@@ -111,6 +111,21 @@ class LambdaFilter : public Filter {
   std::function<optional<bool>(bool)> f_;
 };
 
+/** Optimized lambda filter for stateless lambdas (no capture).
+ *
+ * Uses function pointer instead of std::function to reduce memory overhead.
+ * Memory: 4 bytes (function pointer on 32-bit) vs 32 bytes (std::function).
+ */
+class StatelessLambdaFilter : public Filter {
+ public:
+  explicit StatelessLambdaFilter(optional<bool> (*f)(bool)) : f_(f) {}
+
+  optional<bool> new_value(bool value) override { return this->f_(value); }
+
+ protected:
+  optional<bool> (*f_)(bool);
+};
+
 class SettleFilter : public Filter, public Component {
  public:
   optional<bool> new_value(bool value) override;

esphome/components/esp32/gpio.h

@@ -40,13 +40,13 @@ class ESP32InternalGPIOPin : public InternalGPIOPin {
   // - 3 bytes for members below
   // - 1 byte padding for alignment
   // - 4 bytes for vtable pointer
-  uint8_t pin_;        // GPIO pin number (0-255, actual max ~54 on ESP32)
+  uint8_t pin_;          // GPIO pin number (0-255, actual max ~54 on ESP32)
-  gpio::Flags flags_;  // GPIO flags (1 byte)
+  gpio::Flags flags_{};  // GPIO flags (1 byte)
   struct PinFlags {
     uint8_t inverted : 1;        // Invert pin logic (1 bit)
     uint8_t drive_strength : 2;  // Drive strength 0-3 (2 bits)
     uint8_t reserved : 5;        // Reserved for future use (5 bits)
-  } pin_flags_;                  // Total: 1 byte
+  } pin_flags_{};                // Total: 1 byte
   // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
   static bool isr_service_installed;
 };

esphome/components/esp32/gpio.py

@@ -223,7 +223,10 @@ async def esp32_pin_to_code(config):
     var = cg.new_Pvariable(config[CONF_ID])
     num = config[CONF_NUMBER]
     cg.add(var.set_pin(getattr(gpio_num_t, f"GPIO_NUM_{num}")))
-    cg.add(var.set_inverted(config[CONF_INVERTED]))
+    # Only set if true to avoid bloating setup() function
+    # (inverted bit in pin_flags_ bitfield is zero-initialized to false)
+    if config[CONF_INVERTED]:
+        cg.add(var.set_inverted(True))
     if CONF_DRIVE_STRENGTH in config:
         cg.add(var.set_drive_strength(config[CONF_DRIVE_STRENGTH]))
     cg.add(var.set_flags(pins.gpio_flags_expr(config[CONF_MODE])))

esphome/components/esp8266/gpio.h

@@ -29,8 +29,8 @@ class ESP8266GPIOPin : public InternalGPIOPin {
   void attach_interrupt(void (*func)(void *), void *arg, gpio::InterruptType type) const override;
 
   uint8_t pin_;
-  bool inverted_;
+  bool inverted_{};
-  gpio::Flags flags_;
+  gpio::Flags flags_{};
 };
 
 }  // namespace esp8266

esphome/components/esp8266/gpio.py

@@ -165,7 +165,10 @@ async def esp8266_pin_to_code(config):
     num = config[CONF_NUMBER]
     mode = config[CONF_MODE]
     cg.add(var.set_pin(num))
-    cg.add(var.set_inverted(config[CONF_INVERTED]))
+    # Only set if true to avoid bloating setup() function
+    # (inverted bit in pin_flags_ bitfield is zero-initialized to false)
+    if config[CONF_INVERTED]:
+        cg.add(var.set_inverted(True))
     cg.add(var.set_flags(pins.gpio_flags_expr(mode)))
     if num < 16:
         initial_state: PinInitialState = CORE.data[KEY_ESP8266][KEY_PIN_INITIAL_STATES][

esphome/components/ethernet/__init__.py

@@ -14,7 +14,7 @@ from esphome.components.esp32.const import (
     VARIANT_ESP32S2,
     VARIANT_ESP32S3,
 )
-from esphome.components.network import IPAddress
+from esphome.components.network import ip_address_literal
 from esphome.components.spi import CONF_INTERFACE_INDEX, get_spi_interface
 import esphome.config_validation as cv
 from esphome.const import (
@@ -320,11 +320,11 @@ def _final_validate_spi(config):
 def manual_ip(config):
     return cg.StructInitializer(
         ManualIP,
-        ("static_ip", IPAddress(str(config[CONF_STATIC_IP]))),
+        ("static_ip", ip_address_literal(config[CONF_STATIC_IP])),
-        ("gateway", IPAddress(str(config[CONF_GATEWAY]))),
+        ("gateway", ip_address_literal(config[CONF_GATEWAY])),
-        ("subnet", IPAddress(str(config[CONF_SUBNET]))),
+        ("subnet", ip_address_literal(config[CONF_SUBNET])),
-        ("dns1", IPAddress(str(config[CONF_DNS1]))),
+        ("dns1", ip_address_literal(config[CONF_DNS1])),
-        ("dns2", IPAddress(str(config[CONF_DNS2]))),
+        ("dns2", ip_address_literal(config[CONF_DNS2])),
     )
 
 

esphome/components/host/gpio.h

@@ -28,8 +28,8 @@ class HostGPIOPin : public InternalGPIOPin {
   void attach_interrupt(void (*func)(void *), void *arg, gpio::InterruptType type) const override;
 
   uint8_t pin_;
-  bool inverted_;
+  bool inverted_{};
-  gpio::Flags flags_;
+  gpio::Flags flags_{};
 };
 
 }  // namespace host

esphome/components/host/gpio.py

@@ -57,6 +57,9 @@ async def host_pin_to_code(config):
     var = cg.new_Pvariable(config[CONF_ID])
     num = config[CONF_NUMBER]
     cg.add(var.set_pin(num))
-    cg.add(var.set_inverted(config[CONF_INVERTED]))
+    # Only set if true to avoid bloating setup() function
+    # (inverted bit in pin_flags_ bitfield is zero-initialized to false)
+    if config[CONF_INVERTED]:
+        cg.add(var.set_inverted(True))
     cg.add(var.set_flags(pins.gpio_flags_expr(config[CONF_MODE])))
     return var

esphome/components/libretiny/gpio.py

@@ -199,6 +199,9 @@ async def component_pin_to_code(config):
     var = cg.new_Pvariable(config[CONF_ID])
     num = config[CONF_NUMBER]
     cg.add(var.set_pin(num))
-    cg.add(var.set_inverted(config[CONF_INVERTED]))
+    # Only set if true to avoid bloating setup() function
+    # (inverted bit in pin_flags_ bitfield is zero-initialized to false)
+    if config[CONF_INVERTED]:
+        cg.add(var.set_inverted(True))
     cg.add(var.set_flags(pins.gpio_flags_expr(config[CONF_MODE])))
     return var

esphome/components/libretiny/gpio_arduino.h

@@ -27,8 +27,8 @@ class ArduinoInternalGPIOPin : public InternalGPIOPin {
   void attach_interrupt(void (*func)(void *), void *arg, gpio::InterruptType type) const override;
 
   uint8_t pin_;
-  bool inverted_;
+  bool inverted_{};
-  gpio::Flags flags_;
+  gpio::Flags flags_{};
 };
 
 }  // namespace libretiny

esphome/components/light/addressable_light_effect.h

@@ -57,9 +57,9 @@ class AddressableLightEffect : public LightEffect {
 
 class AddressableLambdaLightEffect : public AddressableLightEffect {
  public:
-  AddressableLambdaLightEffect(const char *name, std::function<void(AddressableLight &, Color, bool initial_run)> f,
+  AddressableLambdaLightEffect(const char *name, void (*f)(AddressableLight &, Color, bool initial_run),
                                uint32_t update_interval)
-      : AddressableLightEffect(name), f_(std::move(f)), update_interval_(update_interval) {}
+      : AddressableLightEffect(name), f_(f), update_interval_(update_interval) {}
   void start() override { this->initial_run_ = true; }
   void apply(AddressableLight &it, const Color &current_color) override {
     const uint32_t now = millis();
@@ -72,7 +72,7 @@ class AddressableLambdaLightEffect : public AddressableLightEffect {
   }
 
  protected:
-  std::function<void(AddressableLight &, Color, bool initial_run)> f_;
+  void (*f_)(AddressableLight &, Color, bool initial_run);
   uint32_t update_interval_;
   uint32_t last_run_{0};
   bool initial_run_;

esphome/components/light/base_light_effects.h

@@ -112,8 +112,8 @@ class RandomLightEffect : public LightEffect {
 
 class LambdaLightEffect : public LightEffect {
  public:
-  LambdaLightEffect(const char *name, std::function<void(bool initial_run)> f, uint32_t update_interval)
+  LambdaLightEffect(const char *name, void (*f)(bool initial_run), uint32_t update_interval)
-      : LightEffect(name), f_(std::move(f)), update_interval_(update_interval) {}
+      : LightEffect(name), f_(f), update_interval_(update_interval) {}
 
   void start() override { this->initial_run_ = true; }
   void apply() override {
@@ -130,7 +130,7 @@ class LambdaLightEffect : public LightEffect {
   uint32_t get_current_index() const { return this->get_index(); }
 
  protected:
-  std::function<void(bool initial_run)> f_;
+  void (*f_)(bool initial_run);
   uint32_t update_interval_;
   uint32_t last_run_{0};
   bool initial_run_;

esphome/components/logger/__init__.py

@@ -1,7 +1,7 @@
 import re
 
 from esphome import automation
-from esphome.automation import LambdaAction
+from esphome.automation import LambdaAction, StatelessLambdaAction
 import esphome.codegen as cg
 from esphome.components.esp32 import add_idf_sdkconfig_option, get_esp32_variant
 from esphome.components.esp32.const import (
@@ -430,7 +430,9 @@ async def logger_log_action_to_code(config, action_id, template_arg, args):
     text = str(cg.statement(esp_log(config[CONF_TAG], config[CONF_FORMAT], *args_)))
 
     lambda_ = await cg.process_lambda(Lambda(text), args, return_type=cg.void)
-    return cg.new_Pvariable(action_id, template_arg, lambda_)
+    return automation.new_lambda_pvariable(
+        action_id, lambda_, StatelessLambdaAction, template_arg
+    )
 
 
 @automation.register_action(
@@ -455,7 +457,9 @@ async def logger_set_level_to_code(config, action_id, template_arg, args):
         text = str(cg.statement(logger.set_log_level(level)))
 
     lambda_ = await cg.process_lambda(Lambda(text), args, return_type=cg.void)
-    return cg.new_Pvariable(action_id, template_arg, lambda_)
+    return automation.new_lambda_pvariable(
+        action_id, lambda_, StatelessLambdaAction, template_arg
+    )
 
 
 FILTER_SOURCE_FILES = filter_source_files_from_platform(

esphome/components/network/__init__.py

@@ -1,3 +1,5 @@
+import ipaddress
+
 import esphome.codegen as cg
 from esphome.components.esp32 import add_idf_sdkconfig_option
 import esphome.config_validation as cv
@@ -10,6 +12,41 @@ AUTO_LOAD = ["mdns"]
 network_ns = cg.esphome_ns.namespace("network")
 IPAddress = network_ns.class_("IPAddress")
 
+
+def ip_address_literal(ip: str | int | None) -> cg.MockObj:
+    """Generate an IPAddress with compile-time initialization instead of runtime parsing.
+
+    This function parses the IP address in Python during code generation and generates
+    a call to the 4-octet constructor (IPAddress(192, 168, 1, 1)) instead of the
+    string constructor (IPAddress("192.168.1.1")). This eliminates runtime string
+    parsing overhead and reduces flash usage on embedded systems.
+
+    Args:
+        ip: IP address as string (e.g., "192.168.1.1"), ipaddress.IPv4Address, or None
+
+    Returns:
+        IPAddress expression that uses 4-octet constructor for efficiency
+    """
+    if ip is None:
+        return IPAddress(0, 0, 0, 0)
+
+    try:
+        # Parse using Python's ipaddress module
+        ip_obj = ipaddress.ip_address(ip)
+    except (ValueError, TypeError):
+        pass
+    else:
+        # Only support IPv4 for now
+        if isinstance(ip_obj, ipaddress.IPv4Address):
+            # Extract octets from the packed bytes representation
+            octets = ip_obj.packed
+            # Generate call to 4-octet constructor: IPAddress(192, 168, 1, 1)
+            return IPAddress(octets[0], octets[1], octets[2], octets[3])
+
+    # Fallback to string constructor if parsing fails
+    return IPAddress(str(ip))
+
+
 CONFIG_SCHEMA = cv.Schema(
     {
         cv.SplitDefault(

esphome/components/nrf52/gpio.py

@@ -74,6 +74,9 @@ async def nrf52_pin_to_code(config):
     var = cg.new_Pvariable(config[CONF_ID])
     num = config[CONF_NUMBER]
     cg.add(var.set_pin(num))
-    cg.add(var.set_inverted(config[CONF_INVERTED]))
+    # Only set if true to avoid bloating setup() function
+    # (inverted bit in pin_flags_ bitfield is zero-initialized to false)
+    if config[CONF_INVERTED]:
+        cg.add(var.set_inverted(True))
     cg.add(var.set_flags(pins.gpio_flags_expr(config[CONF_MODE])))
     return var

esphome/components/rp2040/gpio.h

@@ -29,8 +29,8 @@ class RP2040GPIOPin : public InternalGPIOPin {
   void attach_interrupt(void (*func)(void *), void *arg, gpio::InterruptType type) const override;
 
   uint8_t pin_;
-  bool inverted_;
+  bool inverted_{};
-  gpio::Flags flags_;
+  gpio::Flags flags_{};
 };
 
 }  // namespace rp2040

esphome/components/rp2040/gpio.py

@@ -94,6 +94,9 @@ async def rp2040_pin_to_code(config):
     var = cg.new_Pvariable(config[CONF_ID])
     num = config[CONF_NUMBER]
     cg.add(var.set_pin(num))
-    cg.add(var.set_inverted(config[CONF_INVERTED]))
+    # Only set if true to avoid bloating setup() function
+    # (inverted bit in pin_flags_ bitfield is zero-initialized to false)
+    if config[CONF_INVERTED]:
+        cg.add(var.set_inverted(True))
     cg.add(var.set_flags(pins.gpio_flags_expr(config[CONF_MODE])))
     return var

esphome/components/sensor/__init__.py

@@ -261,6 +261,7 @@ ExponentialMovingAverageFilter = sensor_ns.class_(
 )
 ThrottleAverageFilter = sensor_ns.class_("ThrottleAverageFilter", Filter, cg.Component)
 LambdaFilter = sensor_ns.class_("LambdaFilter", Filter)
+StatelessLambdaFilter = sensor_ns.class_("StatelessLambdaFilter", Filter)
 OffsetFilter = sensor_ns.class_("OffsetFilter", Filter)
 MultiplyFilter = sensor_ns.class_("MultiplyFilter", Filter)
 ValueListFilter = sensor_ns.class_("ValueListFilter", Filter)
@@ -573,7 +574,7 @@ async def lambda_filter_to_code(config, filter_id):
     lambda_ = await cg.process_lambda(
         config, [(float, "x")], return_type=cg.optional.template(float)
     )
-    return cg.new_Pvariable(filter_id, lambda_)
+    return automation.new_lambda_pvariable(filter_id, lambda_, StatelessLambdaFilter)
 
 
 DELTA_SCHEMA = cv.Schema(

esphome/components/sensor/filter.h

@@ -296,6 +296,21 @@ class LambdaFilter : public Filter {
   lambda_filter_t lambda_filter_;
 };
 
+/** Optimized lambda filter for stateless lambdas (no capture).
+ *
+ * Uses function pointer instead of std::function to reduce memory overhead.
+ * Memory: 4 bytes (function pointer on 32-bit) vs 32 bytes (std::function).
+ */
+class StatelessLambdaFilter : public Filter {
+ public:
+  explicit StatelessLambdaFilter(optional<float> (*lambda_filter)(float)) : lambda_filter_(lambda_filter) {}
+
+  optional<float> new_value(float value) override { return this->lambda_filter_(value); }
+
+ protected:
+  optional<float> (*lambda_filter_)(float);
+};
+
 /// A simple filter that adds `offset` to each value it receives.
 class OffsetFilter : public Filter {
  public:

esphome/components/substitutions/__init__.py

@@ -1,4 +1,6 @@
 import logging
+from re import Match
+from typing import Any
 
 from esphome import core
 from esphome.config_helpers import Extend, Remove, merge_config, merge_dicts_ordered
@@ -39,7 +41,34 @@ async def to_code(config):
     pass
 
 
-def _expand_jinja(value, orig_value, path, jinja, ignore_missing):
+def _restore_data_base(value: Any, orig_value: ESPHomeDataBase) -> ESPHomeDataBase:
+    """This function restores ESPHomeDataBase metadata held by the original string.
+    This is needed because during jinja evaluation, strings can be replaced by other types,
+    but we want to keep the original metadata for error reporting and source mapping.
+    For example, if a substitution replaces a string with a dictionary, we want that items
+    in the dictionary to still point to the original document location
+    """
+    if isinstance(value, ESPHomeDataBase):
+        return value
+    if isinstance(value, dict):
+        return {
+            _restore_data_base(k, orig_value): _restore_data_base(v, orig_value)
+            for k, v in value.items()
+        }
+    if isinstance(value, list):
+        return [_restore_data_base(v, orig_value) for v in value]
+    if isinstance(value, str):
+        return make_data_base(value, orig_value)
+    return value
+
+
+def _expand_jinja(
+    value: str | JinjaStr,
+    orig_value: str | JinjaStr,
+    path,
+    jinja: Jinja,
+    ignore_missing: bool,
+) -> Any:
     if has_jinja(value):
         # If the original value passed in to this function is a JinjaStr, it means it contains an unresolved
         # Jinja expression from a previous pass.
@@ -65,10 +94,17 @@ def _expand_jinja(value, orig_value, path, jinja, ignore_missing):
                 f"\nSee {'->'.join(str(x) for x in path)}",
                 path,
             )
+        # If the original, unexpanded string, contained document metadata (ESPHomeDatabase),
+        # assign this same document metadata to the resulting value.
+        if isinstance(orig_value, ESPHomeDataBase):
+            value = _restore_data_base(value, orig_value)
+
     return value
 
 
-def _expand_substitutions(substitutions, value, path, jinja, ignore_missing):
+def _expand_substitutions(
+    substitutions: dict, value: str, path, jinja: Jinja, ignore_missing: bool
+) -> Any:
     if "$" not in value:
         return value
 
@@ -76,14 +112,14 @@ def _expand_substitutions(substitutions, value, path, jinja, ignore_missing):
 
     i = 0
     while True:
-        m = cv.VARIABLE_PROG.search(value, i)
+        m: Match[str] = cv.VARIABLE_PROG.search(value, i)
         if not m:
             # No more variable substitutions found. See if the remainder looks like a jinja template
             value = _expand_jinja(value, orig_value, path, jinja, ignore_missing)
             break
 
         i, j = m.span(0)
-        name = m.group(1)
+        name: str = m.group(1)
         if name.startswith("{") and name.endswith("}"):
             name = name[1:-1]
         if name not in substitutions:
@@ -98,7 +134,7 @@ def _expand_substitutions(substitutions, value, path, jinja, ignore_missing):
             i = j
             continue
 
-        sub = substitutions[name]
+        sub: Any = substitutions[name]
 
         if i == 0 and j == len(value):
             # The variable spans the whole expression, e.g., "${varName}". Return its resolved value directly
@@ -121,7 +157,13 @@ def _expand_substitutions(substitutions, value, path, jinja, ignore_missing):
     return value
 
 
-def _substitute_item(substitutions, item, path, jinja, ignore_missing):
+def _substitute_item(
+    substitutions: dict,
+    item: Any,
+    path: list[int | str],
+    jinja: Jinja,
+    ignore_missing: bool,
+) -> Any | None:
     if isinstance(item, ESPLiteralValue):
         return None  # do not substitute inside literal blocks
     if isinstance(item, list):
@@ -160,7 +202,9 @@ def _substitute_item(substitutions, item, path, jinja, ignore_missing):
     return None
 
 
-def do_substitution_pass(config, command_line_substitutions, ignore_missing=False):
+def do_substitution_pass(
+    config: dict, command_line_substitutions: dict, ignore_missing: bool = False
+) -> None:
     if CONF_SUBSTITUTIONS not in config and not command_line_substitutions:
         return
 

esphome/components/substitutions/jinja.py

@@ -1,10 +1,14 @@
 from ast import literal_eval
+from collections.abc import Iterator
+from itertools import chain, islice
 import logging
 import math
 import re
+from types import GeneratorType
+from typing import Any
 
 import jinja2 as jinja
-from jinja2.sandbox import SandboxedEnvironment
+from jinja2.nativetypes import NativeCodeGenerator, NativeTemplate
 
 from esphome.yaml_util import ESPLiteralValue
 
@@ -24,7 +28,7 @@ detect_jinja_re = re.compile(
 )
 
 
-def has_jinja(st):
+def has_jinja(st: str) -> bool:
     return detect_jinja_re.search(st) is not None
 
 
@@ -109,12 +113,56 @@ class TrackerContext(jinja.runtime.Context):
         return val
 
 
-class Jinja(SandboxedEnvironment):
+def _concat_nodes_override(values: Iterator[Any]) -> Any:
+    """
+    This function customizes how Jinja preserves native types when concatenating
+    multiple result nodes together. If the result is a single node, its value
+    is returned. Otherwise, the nodes are concatenated as strings. If
+    the result can be parsed with `ast.literal_eval`, the parsed
+    value is returned. Otherwise, the string is returned.
+    This helps preserve metadata such as ESPHomeDataBase from original values
+    and mimicks how HomeAssistant deals with template evaluation and preserving
+    the original datatype.
+    """
+    head: list[Any] = list(islice(values, 2))
+
+    if not head:
+        return None
+
+    if len(head) == 1:
+        raw = head[0]
+        if not isinstance(raw, str):
+            return raw
+    else:
+        if isinstance(values, GeneratorType):
+            values = chain(head, values)
+        raw = "".join([str(v) for v in values])
+
+    try:
+        # Attempt to parse the concatenated string into a Python literal.
+        # This allows expressions like "1 + 2" to be evaluated to the integer 3.
+        # If the result is also a string or there is a parsing error,
+        # fall back to returning the raw string. This is consistent with
+        #  Home Assistant's behavior when evaluating templates
+        result = literal_eval(raw)
+        if not isinstance(result, str):
+            return result
+
+    except (ValueError, SyntaxError, MemoryError, TypeError):
+        pass
+    return raw
+
+
+class Jinja(jinja.Environment):
     """
     Wraps a Jinja environment
     """
 
-    def __init__(self, context_vars):
+    # jinja environment customization overrides
+    code_generator_class = NativeCodeGenerator
+    concat = staticmethod(_concat_nodes_override)
+
+    def __init__(self, context_vars: dict):
         super().__init__(
             trim_blocks=True,
             lstrip_blocks=True,
@@ -142,19 +190,10 @@ class Jinja(SandboxedEnvironment):
             **SAFE_GLOBALS,
         }
 
-    def safe_eval(self, expr):
+    def expand(self, content_str: str | JinjaStr) -> Any:
-        try:
-            result = literal_eval(expr)
-            if not isinstance(result, str):
-                return result
-        except (ValueError, SyntaxError, MemoryError, TypeError):
-            pass
-        return expr
-
-    def expand(self, content_str):
         """
         Renders a string that may contain Jinja expressions or statements
-        Returns the resulting processed string if all values could be resolved.
+        Returns the resulting value if all variables and expressions could be resolved.
         Otherwise, it returns a tagged (JinjaStr) string that captures variables
         in scope (upvalues), like a closure for later evaluation.
         """
@@ -172,7 +211,7 @@ class Jinja(SandboxedEnvironment):
         self.context_trace = {}
         try:
             template = self.from_string(content_str)
-            result = self.safe_eval(template.render(override_vars))
+            result = template.render(override_vars)
             if isinstance(result, Undefined):
                 print("" + result)  # force a UndefinedError exception
         except (TemplateSyntaxError, UndefinedError) as err:
@@ -201,3 +240,10 @@ class Jinja(SandboxedEnvironment):
             content_str.result = result
 
         return result, None
+
+
+class JinjaTemplate(NativeTemplate):
+    environment_class = Jinja
+
+
+Jinja.template_class = JinjaTemplate

esphome/components/template/binary_sensor/__init__.py

@@ -38,8 +38,14 @@ async def to_code(config):
         condition = await automation.build_condition(
             condition, cg.TemplateArguments(), []
         )
+        # Generate a stateless lambda that calls condition.check()
+        # capture="" is safe because condition is a global variable in generated C++ code
+        # and doesn't need to be captured. This allows implicit conversion to function pointer.
         template_ = LambdaExpression(
-            f"return {condition.check()};", [], return_type=cg.optional.template(bool)
+            f"return {condition.check()};",
+            [],
+            return_type=cg.optional.template(bool),
+            capture="",
         )
         cg.add(var.set_template(template_))
 

esphome/components/template/binary_sensor/template_binary_sensor.cpp

@@ -9,10 +9,10 @@ static const char *const TAG = "template.binary_sensor";
 void TemplateBinarySensor::setup() { this->loop(); }
 
 void TemplateBinarySensor::loop() {
-  if (this->f_ == nullptr)
+  if (!this->f_.has_value())
     return;
 
-  auto s = this->f_();
+  auto s = (*this->f_)();
   if (s.has_value()) {
     this->publish_state(*s);
   }

esphome/components/template/binary_sensor/template_binary_sensor.h

@@ -8,7 +8,7 @@ namespace template_ {
 
 class TemplateBinarySensor : public Component, public binary_sensor::BinarySensor {
  public:
-  void set_template(std::function<optional<bool>()> &&f) { this->f_ = f; }
+  void set_template(optional<bool> (*f)()) { this->f_ = f; }
 
   void setup() override;
   void loop() override;
@@ -17,7 +17,7 @@ class TemplateBinarySensor : public Component, public binary_sensor::BinarySenso
   float get_setup_priority() const override { return setup_priority::HARDWARE; }
 
  protected:
-  std::function<optional<bool>()> f_{nullptr};
+  optional<optional<bool> (*)()> f_;
 };
 
 }  // namespace template_

esphome/components/template/cover/template_cover.cpp

@@ -63,7 +63,7 @@ void TemplateCover::loop() {
 }
 void TemplateCover::set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
 void TemplateCover::set_assumed_state(bool assumed_state) { this->assumed_state_ = assumed_state; }
-void TemplateCover::set_state_lambda(std::function<optional<float>()> &&f) { this->state_f_ = f; }
+void TemplateCover::set_state_lambda(optional<float> (*f)()) { this->state_f_ = f; }
 float TemplateCover::get_setup_priority() const { return setup_priority::HARDWARE; }
 Trigger<> *TemplateCover::get_open_trigger() const { return this->open_trigger_; }
 Trigger<> *TemplateCover::get_close_trigger() const { return this->close_trigger_; }
@@ -124,7 +124,7 @@ CoverTraits TemplateCover::get_traits() {
 }
 Trigger<float> *TemplateCover::get_position_trigger() const { return this->position_trigger_; }
 Trigger<float> *TemplateCover::get_tilt_trigger() const { return this->tilt_trigger_; }
-void TemplateCover::set_tilt_lambda(std::function<optional<float>()> &&tilt_f) { this->tilt_f_ = tilt_f; }
+void TemplateCover::set_tilt_lambda(optional<float> (*tilt_f)()) { this->tilt_f_ = tilt_f; }
 void TemplateCover::set_has_stop(bool has_stop) { this->has_stop_ = has_stop; }
 void TemplateCover::set_has_toggle(bool has_toggle) { this->has_toggle_ = has_toggle; }
 void TemplateCover::set_has_position(bool has_position) { this->has_position_ = has_position; }

esphome/components/template/cover/template_cover.h

@@ -17,7 +17,7 @@ class TemplateCover : public cover::Cover, public Component {
  public:
   TemplateCover();
 
-  void set_state_lambda(std::function<optional<float>()> &&f);
+  void set_state_lambda(optional<float> (*f)());
   Trigger<> *get_open_trigger() const;
   Trigger<> *get_close_trigger() const;
   Trigger<> *get_stop_trigger() const;
@@ -26,7 +26,7 @@ class TemplateCover : public cover::Cover, public Component {
   Trigger<float> *get_tilt_trigger() const;
   void set_optimistic(bool optimistic);
   void set_assumed_state(bool assumed_state);
-  void set_tilt_lambda(std::function<optional<float>()> &&tilt_f);
+  void set_tilt_lambda(optional<float> (*tilt_f)());
   void set_has_stop(bool has_stop);
   void set_has_position(bool has_position);
   void set_has_tilt(bool has_tilt);
@@ -45,8 +45,8 @@ class TemplateCover : public cover::Cover, public Component {
   void stop_prev_trigger_();
 
   TemplateCoverRestoreMode restore_mode_{COVER_RESTORE};
-  optional<std::function<optional<float>()>> state_f_;
+  optional<optional<float> (*)()> state_f_;
-  optional<std::function<optional<float>()>> tilt_f_;
+  optional<optional<float> (*)()> tilt_f_;
   bool assumed_state_{false};
   bool optimistic_{false};
   Trigger<> *open_trigger_;

esphome/components/template/datetime/template_date.h

@@ -15,7 +15,7 @@ namespace template_ {
 
 class TemplateDate : public datetime::DateEntity, public PollingComponent {
  public:
-  void set_template(std::function<optional<ESPTime>()> &&f) { this->f_ = f; }
+  void set_template(optional<ESPTime> (*f)()) { this->f_ = f; }
 
   void setup() override;
   void update() override;
@@ -35,7 +35,7 @@ class TemplateDate : public datetime::DateEntity, public PollingComponent {
   ESPTime initial_value_{};
   bool restore_value_{false};
   Trigger<ESPTime> *set_trigger_ = new Trigger<ESPTime>();
-  optional<std::function<optional<ESPTime>()>> f_;
+  optional<optional<ESPTime> (*)()> f_;
 
   ESPPreferenceObject pref_;
 };

esphome/components/template/datetime/template_datetime.h

@@ -15,7 +15,7 @@ namespace template_ {
 
 class TemplateDateTime : public datetime::DateTimeEntity, public PollingComponent {
  public:
-  void set_template(std::function<optional<ESPTime>()> &&f) { this->f_ = f; }
+  void set_template(optional<ESPTime> (*f)()) { this->f_ = f; }
 
   void setup() override;
   void update() override;
@@ -35,7 +35,7 @@ class TemplateDateTime : public datetime::DateTimeEntity, public PollingComponen
   ESPTime initial_value_{};
   bool restore_value_{false};
   Trigger<ESPTime> *set_trigger_ = new Trigger<ESPTime>();
-  optional<std::function<optional<ESPTime>()>> f_;
+  optional<optional<ESPTime> (*)()> f_;
 
   ESPPreferenceObject pref_;
 };

esphome/components/template/datetime/template_time.h

@@ -15,7 +15,7 @@ namespace template_ {
 
 class TemplateTime : public datetime::TimeEntity, public PollingComponent {
  public:
-  void set_template(std::function<optional<ESPTime>()> &&f) { this->f_ = f; }
+  void set_template(optional<ESPTime> (*f)()) { this->f_ = f; }
 
   void setup() override;
   void update() override;
@@ -35,7 +35,7 @@ class TemplateTime : public datetime::TimeEntity, public PollingComponent {
   ESPTime initial_value_{};
   bool restore_value_{false};
   Trigger<ESPTime> *set_trigger_ = new Trigger<ESPTime>();
-  optional<std::function<optional<ESPTime>()>> f_;
+  optional<optional<ESPTime> (*)()> f_;
 
   ESPPreferenceObject pref_;
 };

esphome/components/template/lock/template_lock.cpp

@@ -45,7 +45,7 @@ void TemplateLock::open_latch() {
   this->open_trigger_->trigger();
 }
 void TemplateLock::set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
-void TemplateLock::set_state_lambda(std::function<optional<lock::LockState>()> &&f) { this->f_ = f; }
+void TemplateLock::set_state_lambda(optional<lock::LockState> (*f)()) { this->f_ = f; }
 float TemplateLock::get_setup_priority() const { return setup_priority::HARDWARE; }
 Trigger<> *TemplateLock::get_lock_trigger() const { return this->lock_trigger_; }
 Trigger<> *TemplateLock::get_unlock_trigger() const { return this->unlock_trigger_; }

esphome/components/template/lock/template_lock.h

@@ -13,7 +13,7 @@ class TemplateLock : public lock::Lock, public Component {
 
   void dump_config() override;
 
-  void set_state_lambda(std::function<optional<lock::LockState>()> &&f);
+  void set_state_lambda(optional<lock::LockState> (*f)());
   Trigger<> *get_lock_trigger() const;
   Trigger<> *get_unlock_trigger() const;
   Trigger<> *get_open_trigger() const;
@@ -26,7 +26,7 @@ class TemplateLock : public lock::Lock, public Component {
   void control(const lock::LockCall &call) override;
   void open_latch() override;
 
-  optional<std::function<optional<lock::LockState>()>> f_;
+  optional<optional<lock::LockState> (*)()> f_;
   bool optimistic_{false};
   Trigger<> *lock_trigger_;
   Trigger<> *unlock_trigger_;

esphome/components/template/number/template_number.h

@@ -10,7 +10,7 @@ namespace template_ {
 
 class TemplateNumber : public number::Number, public PollingComponent {
  public:
-  void set_template(std::function<optional<float>()> &&f) { this->f_ = f; }
+  void set_template(optional<float> (*f)()) { this->f_ = f; }
 
   void setup() override;
   void update() override;
@@ -28,7 +28,7 @@ class TemplateNumber : public number::Number, public PollingComponent {
   float initial_value_{NAN};
   bool restore_value_{false};
   Trigger<float> *set_trigger_ = new Trigger<float>();
-  optional<std::function<optional<float>()>> f_;
+  optional<optional<float> (*)()> f_;
 
   ESPPreferenceObject pref_;
 };

esphome/components/template/select/template_select.h

@@ -10,7 +10,7 @@ namespace template_ {
 
 class TemplateSelect : public select::Select, public PollingComponent {
  public:
-  void set_template(std::function<optional<std::string>()> &&f) { this->f_ = f; }
+  void set_template(optional<std::string> (*f)()) { this->f_ = f; }
 
   void setup() override;
   void update() override;
@@ -28,7 +28,7 @@ class TemplateSelect : public select::Select, public PollingComponent {
   std::string initial_option_;
   bool restore_value_ = false;
   Trigger<std::string> *set_trigger_ = new Trigger<std::string>();
-  optional<std::function<optional<std::string>()>> f_;
+  optional<optional<std::string> (*)()> f_;
 
   ESPPreferenceObject pref_;
 };

esphome/components/template/sensor/template_sensor.cpp

@@ -17,7 +17,7 @@ void TemplateSensor::update() {
   }
 }
 float TemplateSensor::get_setup_priority() const { return setup_priority::HARDWARE; }
-void TemplateSensor::set_template(std::function<optional<float>()> &&f) { this->f_ = f; }
+void TemplateSensor::set_template(optional<float> (*f)()) { this->f_ = f; }
 void TemplateSensor::dump_config() {
   LOG_SENSOR("", "Template Sensor", this);
   LOG_UPDATE_INTERVAL(this);

esphome/components/template/sensor/template_sensor.h

@@ -8,7 +8,7 @@ namespace template_ {
 
 class TemplateSensor : public sensor::Sensor, public PollingComponent {
  public:
-  void set_template(std::function<optional<float>()> &&f);
+  void set_template(optional<float> (*f)());
 
   void update() override;
 
@@ -17,7 +17,7 @@ class TemplateSensor : public sensor::Sensor, public PollingComponent {
   float get_setup_priority() const override;
 
  protected:
-  optional<std::function<optional<float>()>> f_;
+  optional<optional<float> (*)()> f_;
 };
 
 }  // namespace template_

esphome/components/template/switch/template_switch.cpp

@@ -35,7 +35,7 @@ void TemplateSwitch::write_state(bool state) {
 }
 void TemplateSwitch::set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
 bool TemplateSwitch::assumed_state() { return this->assumed_state_; }
-void TemplateSwitch::set_state_lambda(std::function<optional<bool>()> &&f) { this->f_ = f; }
+void TemplateSwitch::set_state_lambda(optional<bool> (*f)()) { this->f_ = f; }
 float TemplateSwitch::get_setup_priority() const { return setup_priority::HARDWARE - 2.0f; }
 Trigger<> *TemplateSwitch::get_turn_on_trigger() const { return this->turn_on_trigger_; }
 Trigger<> *TemplateSwitch::get_turn_off_trigger() const { return this->turn_off_trigger_; }

esphome/components/template/switch/template_switch.h

@@ -14,7 +14,7 @@ class TemplateSwitch : public switch_::Switch, public Component {
   void setup() override;
   void dump_config() override;
 
-  void set_state_lambda(std::function<optional<bool>()> &&f);
+  void set_state_lambda(optional<bool> (*f)());
   Trigger<> *get_turn_on_trigger() const;
   Trigger<> *get_turn_off_trigger() const;
   void set_optimistic(bool optimistic);
@@ -28,7 +28,7 @@ class TemplateSwitch : public switch_::Switch, public Component {
 
   void write_state(bool state) override;
 
-  optional<std::function<optional<bool>()>> f_;
+  optional<optional<bool> (*)()> f_;
   bool optimistic_{false};
   bool assumed_state_{false};
   Trigger<> *turn_on_trigger_;

esphome/components/template/text/template_text.h

@@ -61,7 +61,7 @@ template<uint8_t SZ> class TextSaver : public TemplateTextSaverBase {
 
 class TemplateText : public text::Text, public PollingComponent {
  public:
-  void set_template(std::function<optional<std::string>()> &&f) { this->f_ = f; }
+  void set_template(optional<std::string> (*f)()) { this->f_ = f; }
 
   void setup() override;
   void update() override;
@@ -78,7 +78,7 @@ class TemplateText : public text::Text, public PollingComponent {
   bool optimistic_ = false;
   std::string initial_value_;
   Trigger<std::string> *set_trigger_ = new Trigger<std::string>();
-  optional<std::function<optional<std::string>()>> f_{nullptr};
+  optional<optional<std::string> (*)()> f_{nullptr};
 
   TemplateTextSaverBase *pref_ = nullptr;
 };

esphome/components/template/text_sensor/template_text_sensor.cpp

@@ -16,7 +16,7 @@ void TemplateTextSensor::update() {
   }
 }
 float TemplateTextSensor::get_setup_priority() const { return setup_priority::HARDWARE; }
-void TemplateTextSensor::set_template(std::function<optional<std::string>()> &&f) { this->f_ = f; }
+void TemplateTextSensor::set_template(optional<std::string> (*f)()) { this->f_ = f; }
 void TemplateTextSensor::dump_config() { LOG_TEXT_SENSOR("", "Template Sensor", this); }
 
 }  // namespace template_

esphome/components/template/text_sensor/template_text_sensor.h

@@ -9,7 +9,7 @@ namespace template_ {
 
 class TemplateTextSensor : public text_sensor::TextSensor, public PollingComponent {
  public:
-  void set_template(std::function<optional<std::string>()> &&f);
+  void set_template(optional<std::string> (*f)());
 
   void update() override;
 
@@ -18,7 +18,7 @@ class TemplateTextSensor : public text_sensor::TextSensor, public PollingCompone
   void dump_config() override;
 
  protected:
-  optional<std::function<optional<std::string>()>> f_{};
+  optional<optional<std::string> (*)()> f_{};
 };
 
 }  // namespace template_

esphome/components/template/valve/template_valve.cpp

@@ -55,7 +55,7 @@ void TemplateValve::loop() {
 
 void TemplateValve::set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
 void TemplateValve::set_assumed_state(bool assumed_state) { this->assumed_state_ = assumed_state; }
-void TemplateValve::set_state_lambda(std::function<optional<float>()> &&f) { this->state_f_ = f; }
+void TemplateValve::set_state_lambda(optional<float> (*f)()) { this->state_f_ = f; }
 float TemplateValve::get_setup_priority() const { return setup_priority::HARDWARE; }
 
 Trigger<> *TemplateValve::get_open_trigger() const { return this->open_trigger_; }

esphome/components/template/valve/template_valve.h

@@ -17,7 +17,7 @@ class TemplateValve : public valve::Valve, public Component {
  public:
   TemplateValve();
 
-  void set_state_lambda(std::function<optional<float>()> &&f);
+  void set_state_lambda(optional<float> (*f)());
   Trigger<> *get_open_trigger() const;
   Trigger<> *get_close_trigger() const;
   Trigger<> *get_stop_trigger() const;
@@ -42,7 +42,7 @@ class TemplateValve : public valve::Valve, public Component {
   void stop_prev_trigger_();
 
   TemplateValveRestoreMode restore_mode_{VALVE_NO_RESTORE};
-  optional<std::function<optional<float>()>> state_f_;
+  optional<optional<float> (*)()> state_f_;
   bool assumed_state_{false};
   bool optimistic_{false};
   Trigger<> *open_trigger_;

esphome/components/text_sensor/__init__.py

@@ -57,6 +57,7 @@ validate_filters = cv.validate_registry("filter", FILTER_REGISTRY)
 # Filters
 Filter = text_sensor_ns.class_("Filter")
 LambdaFilter = text_sensor_ns.class_("LambdaFilter", Filter)
+StatelessLambdaFilter = text_sensor_ns.class_("StatelessLambdaFilter", Filter)
 ToUpperFilter = text_sensor_ns.class_("ToUpperFilter", Filter)
 ToLowerFilter = text_sensor_ns.class_("ToLowerFilter", Filter)
 AppendFilter = text_sensor_ns.class_("AppendFilter", Filter)
@@ -70,7 +71,7 @@ async def lambda_filter_to_code(config, filter_id):
     lambda_ = await cg.process_lambda(
         config, [(cg.std_string, "x")], return_type=cg.optional.template(cg.std_string)
     )
-    return cg.new_Pvariable(filter_id, lambda_)
+    return automation.new_lambda_pvariable(filter_id, lambda_, StatelessLambdaFilter)
 
 
 @FILTER_REGISTRY.register("to_upper", ToUpperFilter, {})

esphome/components/text_sensor/filter.h

@@ -62,6 +62,21 @@ class LambdaFilter : public Filter {
   lambda_filter_t lambda_filter_;
 };
 
+/** Optimized lambda filter for stateless lambdas (no capture).
+ *
+ * Uses function pointer instead of std::function to reduce memory overhead.
+ * Memory: 4 bytes (function pointer on 32-bit) vs 32 bytes (std::function).
+ */
+class StatelessLambdaFilter : public Filter {
+ public:
+  explicit StatelessLambdaFilter(optional<std::string> (*lambda_filter)(std::string)) : lambda_filter_(lambda_filter) {}
+
+  optional<std::string> new_value(std::string value) override { return this->lambda_filter_(value); }
+
+ protected:
+  optional<std::string> (*lambda_filter_)(std::string);
+};
+
 /// A simple filter that converts all text to uppercase
 class ToUpperFilter : public Filter {
  public:

esphome/components/uart/uart_component_esp_idf.cpp

@@ -99,10 +99,26 @@ void IDFUARTComponent::setup() {
 }
 
 void IDFUARTComponent::load_settings(bool dump_config) {
-  uart_config_t uart_config = this->get_config_();
+  esp_err_t err;
-  esp_err_t err = uart_param_config(this->uart_num_, &uart_config);
+
+  if (uart_is_driver_installed(this->uart_num_)) {
+    err = uart_driver_delete(this->uart_num_);
+    if (err != ESP_OK) {
+      ESP_LOGW(TAG, "uart_driver_delete failed: %s", esp_err_to_name(err));
+      this->mark_failed();
+      return;
+    }
+  }
+  err = uart_driver_install(this->uart_num_,        // UART number
+                            this->rx_buffer_size_,  // RX ring buffer size
+                            0,   // TX ring buffer size. If zero, driver will not use a TX buffer and TX function will
+                                 // block task until all data has been sent out
+                            20,  // event queue size/depth
+                            &this->uart_event_queue_,  // event queue
+                            0                          // Flags used to allocate the interrupt
+  );
   if (err != ESP_OK) {
-    ESP_LOGW(TAG, "uart_param_config failed: %s", esp_err_to_name(err));
+    ESP_LOGW(TAG, "uart_driver_install failed: %s", esp_err_to_name(err));
     this->mark_failed();
     return;
   }
@@ -119,10 +135,12 @@ void IDFUARTComponent::load_settings(bool dump_config) {
   int8_t flow_control = this->flow_control_pin_ != nullptr ? this->flow_control_pin_->get_pin() : -1;
 
   uint32_t invert = 0;
-  if (this->tx_pin_ != nullptr && this->tx_pin_->is_inverted())
+  if (this->tx_pin_ != nullptr && this->tx_pin_->is_inverted()) {
     invert |= UART_SIGNAL_TXD_INV;
-  if (this->rx_pin_ != nullptr && this->rx_pin_->is_inverted())
+  }
+  if (this->rx_pin_ != nullptr && this->rx_pin_->is_inverted()) {
     invert |= UART_SIGNAL_RXD_INV;
+  }
 
   err = uart_set_line_inverse(this->uart_num_, invert);
   if (err != ESP_OK) {
@@ -138,26 +156,6 @@ void IDFUARTComponent::load_settings(bool dump_config) {
     return;
   }
 
-  if (uart_is_driver_installed(this->uart_num_)) {
-    uart_driver_delete(this->uart_num_);
-    if (err != ESP_OK) {
-      ESP_LOGW(TAG, "uart_driver_delete failed: %s", esp_err_to_name(err));
-      this->mark_failed();
-      return;
-    }
-  }
-  err = uart_driver_install(this->uart_num_, /* UART RX ring buffer size. */ this->rx_buffer_size_,
-                            /* UART TX ring buffer size. If set to zero, driver will not use TX buffer, TX function will
-                               block task until all data have been sent out.*/
-                            0,
-                            /* UART event queue size/depth. */ 20, &(this->uart_event_queue_),
-                            /* Flags used to allocate the interrupt. */ 0);
-  if (err != ESP_OK) {
-    ESP_LOGW(TAG, "uart_driver_install failed: %s", esp_err_to_name(err));
-    this->mark_failed();
-    return;
-  }
-
   err = uart_set_rx_full_threshold(this->uart_num_, this->rx_full_threshold_);
   if (err != ESP_OK) {
     ESP_LOGW(TAG, "uart_set_rx_full_threshold failed: %s", esp_err_to_name(err));
@@ -173,24 +171,32 @@ void IDFUARTComponent::load_settings(bool dump_config) {
   }
 
   auto mode = this->flow_control_pin_ != nullptr ? UART_MODE_RS485_HALF_DUPLEX : UART_MODE_UART;
-  err = uart_set_mode(this->uart_num_, mode);
+  err = uart_set_mode(this->uart_num_, mode);  // per docs, must be called only after uart_driver_install()
   if (err != ESP_OK) {
     ESP_LOGW(TAG, "uart_set_mode failed: %s", esp_err_to_name(err));
     this->mark_failed();
     return;
   }
 
+  uart_config_t uart_config = this->get_config_();
+  err = uart_param_config(this->uart_num_, &uart_config);
+  if (err != ESP_OK) {
+    ESP_LOGW(TAG, "uart_param_config failed: %s", esp_err_to_name(err));
+    this->mark_failed();
+    return;
+  }
+
   if (dump_config) {
-    ESP_LOGCONFIG(TAG, "UART %u was reloaded.", this->uart_num_);
+    ESP_LOGCONFIG(TAG, "Reloaded UART %u", this->uart_num_);
     this->dump_config();
   }
 }
 
 void IDFUARTComponent::dump_config() {
   ESP_LOGCONFIG(TAG, "UART Bus %u:", this->uart_num_);
-  LOG_PIN("  TX Pin: ", tx_pin_);
+  LOG_PIN("  TX Pin: ", this->tx_pin_);
-  LOG_PIN("  RX Pin: ", rx_pin_);
+  LOG_PIN("  RX Pin: ", this->rx_pin_);
-  LOG_PIN("  Flow Control Pin: ", flow_control_pin_);
+  LOG_PIN("  Flow Control Pin: ", this->flow_control_pin_);
   if (this->rx_pin_ != nullptr) {
     ESP_LOGCONFIG(TAG,
                   "  RX Buffer Size: %u\n"

esphome/components/wifi/__init__.py

@@ -3,7 +3,7 @@ from esphome.automation import Condition
 import esphome.codegen as cg
 from esphome.components.const import CONF_USE_PSRAM
 from esphome.components.esp32 import add_idf_sdkconfig_option, const, get_esp32_variant
-from esphome.components.network import IPAddress
+from esphome.components.network import ip_address_literal
 from esphome.config_helpers import filter_source_files_from_platform
 import esphome.config_validation as cv
 from esphome.config_validation import only_with_esp_idf
@@ -334,9 +334,7 @@ def eap_auth(config):
 
 
 def safe_ip(ip):
-    if ip is None:
+    return ip_address_literal(ip)
-        return IPAddress(0, 0, 0, 0)
-    return IPAddress(str(ip))
 
 
 def manual_ip(config):

esphome/components/zephyr/gpio.h

@@ -26,10 +26,10 @@ class ZephyrGPIOPin : public InternalGPIOPin {
  protected:
   void attach_interrupt(void (*func)(void *), void *arg, gpio::InterruptType type) const override;
   uint8_t pin_;
-  bool inverted_;
+  bool inverted_{};
-  gpio::Flags flags_;
+  gpio::Flags flags_{};
-  const device *gpio_ = nullptr;
+  const device *gpio_{nullptr};
-  bool value_ = false;
+  bool value_{false};
 };
 
 }  // namespace zephyr

esphome/core/automation.h

@@ -4,6 +4,8 @@
 #include "esphome/core/defines.h"
 #include "esphome/core/helpers.h"
 #include "esphome/core/preferences.h"
+#include <concepts>
+#include <functional>
 #include <utility>
 #include <vector>
 
@@ -27,11 +29,20 @@ template<typename T, typename... X> class TemplatableValue {
  public:
   TemplatableValue() : type_(NONE) {}
 
-  template<typename F, enable_if_t<!is_invocable<F, X...>::value, int> = 0> TemplatableValue(F value) : type_(VALUE) {
+  template<typename F> TemplatableValue(F value) requires(!std::invocable<F, X...>) : type_(VALUE) {
     new (&this->value_) T(std::move(value));
   }
 
-  template<typename F, enable_if_t<is_invocable<F, X...>::value, int> = 0> TemplatableValue(F f) : type_(LAMBDA) {
+  // For stateless lambdas (convertible to function pointer): use function pointer
+  template<typename F>
+  TemplatableValue(F f) requires std::invocable<F, X...> && std::convertible_to<F, T (*)(X...)>
+      : type_(STATELESS_LAMBDA) {
+    this->stateless_f_ = f;  // Implicit conversion to function pointer
+  }
+
+  // For stateful lambdas (not convertible to function pointer): use std::function
+  template<typename F>
+  TemplatableValue(F f) requires std::invocable<F, X...> &&(!std::convertible_to<F, T (*)(X...)>) : type_(LAMBDA) {
     this->f_ = new std::function<T(X...)>(std::move(f));
   }
 
@@ -41,6 +52,8 @@ template<typename T, typename... X> class TemplatableValue {
       new (&this->value_) T(other.value_);
     } else if (type_ == LAMBDA) {
       this->f_ = new std::function<T(X...)>(*other.f_);
+    } else if (type_ == STATELESS_LAMBDA) {
+      this->stateless_f_ = other.stateless_f_;
     }
   }
 
@@ -51,6 +64,8 @@ template<typename T, typename... X> class TemplatableValue {
     } else if (type_ == LAMBDA) {
       this->f_ = other.f_;
       other.f_ = nullptr;
+    } else if (type_ == STATELESS_LAMBDA) {
+      this->stateless_f_ = other.stateless_f_;
     }
     other.type_ = NONE;
   }
@@ -78,16 +93,23 @@ template<typename T, typename... X> class TemplatableValue {
     } else if (type_ == LAMBDA) {
       delete this->f_;
     }
+    // STATELESS_LAMBDA/NONE: no cleanup needed (function pointer or empty, not heap-allocated)
   }
 
   bool has_value() { return this->type_ != NONE; }
 
   T value(X... x) {
-    if (this->type_ == LAMBDA) {
+    switch (this->type_) {
-      return (*this->f_)(x...);
+      case STATELESS_LAMBDA:
+        return this->stateless_f_(x...);  // Direct function pointer call
+      case LAMBDA:
+        return (*this->f_)(x...);  // std::function call
+      case VALUE:
+        return this->value_;
+      case NONE:
+      default:
+        return T{};
     }
-    // return value also when none
-    return this->type_ == VALUE ? this->value_ : T{};
   }
 
   optional<T> optional_value(X... x) {
@@ -109,11 +131,13 @@ template<typename T, typename... X> class TemplatableValue {
     NONE,
     VALUE,
     LAMBDA,
+    STATELESS_LAMBDA,
   } type_;
 
   union {
     T value_;
     std::function<T(X...)> *f_;
+    T (*stateless_f_)(X...);
   };
 };
 

esphome/core/base_automation.h

@@ -79,6 +79,18 @@ template<typename... Ts> class LambdaCondition : public Condition<Ts...> {
   std::function<bool(Ts...)> f_;
 };
 
+/// Optimized lambda condition for stateless lambdas (no capture).
+/// Uses function pointer instead of std::function to reduce memory overhead.
+/// Memory: 4 bytes (function pointer on 32-bit) vs 32 bytes (std::function).
+template<typename... Ts> class StatelessLambdaCondition : public Condition<Ts...> {
+ public:
+  explicit StatelessLambdaCondition(bool (*f)(Ts...)) : f_(f) {}
+  bool check(Ts... x) override { return this->f_(x...); }
+
+ protected:
+  bool (*f_)(Ts...);
+};
+
 template<typename... Ts> class ForCondition : public Condition<Ts...>, public Component {
  public:
   explicit ForCondition(Condition<> *condition) : condition_(condition) {}
@@ -190,6 +202,19 @@ template<typename... Ts> class LambdaAction : public Action<Ts...> {
   std::function<void(Ts...)> f_;
 };
 
+/// Optimized lambda action for stateless lambdas (no capture).
+/// Uses function pointer instead of std::function to reduce memory overhead.
+/// Memory: 4 bytes (function pointer on 32-bit) vs 32 bytes (std::function).
+template<typename... Ts> class StatelessLambdaAction : public Action<Ts...> {
+ public:
+  explicit StatelessLambdaAction(void (*f)(Ts...)) : f_(f) {}
+
+  void play(Ts... x) override { this->f_(x...); }
+
+ protected:
+  void (*f_)(Ts...);
+};
+
 template<typename... Ts> class IfAction : public Action<Ts...> {
  public:
   explicit IfAction(Condition<Ts...> *condition) : condition_(condition) {}

esphome/core/defines.h

@@ -123,6 +123,7 @@
 #define USE_API_NOISE
 #define USE_API_PLAINTEXT
 #define USE_API_SERVICES
+#define USE_API_CUSTOM_SERVICES
 #define API_MAX_SEND_QUEUE 8
 #define USE_MD5
 #define USE_SHA256

esphome/cpp_generator.py

@@ -198,6 +198,8 @@ class LambdaExpression(Expression):
         self.return_type = safe_exp(return_type) if return_type is not None else None
 
     def __str__(self):
+        # Stateless lambdas (empty capture) implicitly convert to function pointers
+        # when assigned to function pointer types - no unary + needed
         cpp = f"[{self.capture}]({self.parameters})"
         if self.return_type is not None:
             cpp += f" -> {self.return_type}"
@@ -700,6 +702,12 @@ async def process_lambda(
             parts[i * 3 + 1] = var
         parts[i * 3 + 2] = ""
 
+    # All id() references are global variables in generated C++ code.
+    # Global variables should not be captured - they're accessible everywhere.
+    # Use empty capture instead of capture-by-value.
+    if capture == "=":
+        capture = ""
+
     if isinstance(value, ESPHomeDataBase) and value.esp_range is not None:
         location = value.esp_range.start_mark
         location.line += value.content_offset

esphome/cpp_types.py

@@ -23,6 +23,7 @@ size_t = global_ns.namespace("size_t")
 const_char_ptr = global_ns.namespace("const char *")
 NAN = global_ns.namespace("NAN")
 esphome_ns = global_ns  # using namespace esphome;
+FixedVector = esphome_ns.class_("FixedVector")
 App = esphome_ns.App
 EntityBase = esphome_ns.class_("EntityBase")
 Component = esphome_ns.class_("Component")

pyproject.toml

@@ -19,7 +19,9 @@ classifiers = [
     "Programming Language :: Python :: 3",
     "Topic :: Home Automation",
 ]
-requires-python = ">=3.11.0"
+
+# Python 3.14 is currently not supported by IDF <= 5.5.1, see https://github.com/esphome/esphome/issues/11502
+requires-python = ">=3.11.0,<3.14"
 
 dynamic = ["dependencies", "optional-dependencies", "version"]
 

tests/component_tests/text/test_text.py

@@ -58,7 +58,7 @@ def test_text_config_value_mode_set(generate_main):
 
 def test_text_config_lamda_is_set(generate_main):
     """
-    Test if lambda is set for lambda mode
+    Test if lambda is set for lambda mode (optimized with stateless lambda)
     """
     # Given
 
@@ -66,5 +66,5 @@ def test_text_config_lamda_is_set(generate_main):
     main_cpp = generate_main("tests/component_tests/text/test_text.yaml")
 
     # Then
-    assert "it_4->set_template([=]() -> esphome::optional<std::string> {" in main_cpp
+    assert "it_4->set_template([]() -> esphome::optional<std::string> {" in main_cpp
     assert 'return std::string{"Hello"};' in main_cpp

tests/unit_tests/test_cpp_generator.py

@@ -173,6 +173,61 @@ class TestLambdaExpression:
             "}"
         )
 
+    def test_str__stateless_no_return(self):
+        """Test stateless lambda (empty capture) generates correctly"""
+        target = cg.LambdaExpression(
+            ('ESP_LOGD("main", "Test message");',),
+            (),  # No parameters
+            "",  # Empty capture (stateless)
+        )
+
+        actual = str(target)
+
+        assert actual == ('[]() {\n  ESP_LOGD("main", "Test message");\n}')
+
+    def test_str__stateless_with_return(self):
+        """Test stateless lambda with return type generates correctly"""
+        target = cg.LambdaExpression(
+            ("return global_value > 0;",),
+            (),  # No parameters
+            "",  # Empty capture (stateless)
+            bool,  # Return type
+        )
+
+        actual = str(target)
+
+        assert actual == ("[]() -> bool {\n  return global_value > 0;\n}")
+
+    def test_str__stateless_with_params(self):
+        """Test stateless lambda with parameters generates correctly"""
+        target = cg.LambdaExpression(
+            ("return foo + bar;",),
+            ((int, "foo"), (float, "bar")),
+            "",  # Empty capture (stateless)
+            float,
+        )
+
+        actual = str(target)
+
+        assert actual == (
+            "[](int32_t foo, float bar) -> float {\n  return foo + bar;\n}"
+        )
+
+    def test_str__with_capture(self):
+        """Test lambda with capture generates correctly"""
+        target = cg.LambdaExpression(
+            ("return captured_var + x;",),
+            ((int, "x"),),
+            "captured_var",  # Has capture (not stateless)
+            int,
+        )
+
+        actual = str(target)
+
+        assert actual == (
+            "[captured_var](int32_t x) -> int32_t {\n  return captured_var + x;\n}"
+        )
+
 
 class TestLiterals:
     @pytest.mark.parametrize(

tests/unit_tests/test_substitutions.py

@@ -1,6 +1,7 @@
 import glob
 import logging
 from pathlib import Path
+from typing import Any
 
 from esphome import config as config_module, yaml_util
 from esphome.components import substitutions
@@ -60,6 +61,29 @@ def write_yaml(path: Path, data: dict) -> None:
     path.write_text(yaml_util.dump(data), encoding="utf-8")
 
 
+def verify_database(value: Any, path: str = "") -> str | None:
+    if isinstance(value, list):
+        for i, v in enumerate(value):
+            result = verify_database(v, f"{path}[{i}]")
+            if result is not None:
+                return result
+        return None
+    if isinstance(value, dict):
+        for k, v in value.items():
+            key_result = verify_database(k, f"{path}/{k}")
+            if key_result is not None:
+                return key_result
+            value_result = verify_database(v, f"{path}/{k}")
+            if value_result is not None:
+                return value_result
+        return None
+    if isinstance(value, str):
+        if not isinstance(value, yaml_util.ESPHomeDataBase):
+            return f"{path}: {value!r} is not ESPHomeDataBase"
+        return None
+    return None
+
+
 def test_substitutions_fixtures(fixture_path):
     base_dir = fixture_path / "substitutions"
     sources = sorted(glob.glob(str(base_dir / "*.input.yaml")))
@@ -83,6 +107,9 @@ def test_substitutions_fixtures(fixture_path):
             substitutions.do_substitution_pass(config, None)
 
             resolve_extend_remove(config)
+            verify_database_result = verify_database(config)
+            if verify_database_result is not None:
+                raise AssertionError(verify_database_result)
 
             # Also load expected using ESPHome's loader, or use {} if missing and DEV_MODE
             if expected_path.is_file():