remove

Add STATELESS_LAMBDA support to TemplatableValue class using C++20 concepts:
- Automatically detects stateless lambdas (convertible to function pointers)
- Uses 4-byte function pointer instead of 32-byte std::function
- Falls back to std::function for stateful lambdas

Add StatelessLambdaAction and StatelessLambdaCondition classes for automation:
- Memory: 4 bytes vs 32 bytes per lambda
- Direct function pointer calls (no std::function overhead)

This infrastructure enables template platforms to use function pointers for
stateless lambdas, saving ~28 bytes per lambda instance.

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
@@ -100,6 +105,36 @@ LambdaCondition = cg.esphome_ns.class_("LambdaCondition", 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 = {}

esphome/components/template/binary_sensor/__init__.py

@@ -10,6 +10,9 @@ from .. import template_ns
 TemplateBinarySensor = template_ns.class_(
     "TemplateBinarySensor", binary_sensor.BinarySensor, cg.Component
 )
+StatelessTemplateBinarySensor = template_ns.class_(
+    "StatelessTemplateBinarySensor", binary_sensor.BinarySensor, cg.Component
+)
 
 CONFIG_SCHEMA = (
     binary_sensor.binary_sensor_schema(TemplateBinarySensor)
@@ -26,15 +29,22 @@ CONFIG_SCHEMA = (
 
 
 async def to_code(config):
-    var = await binary_sensor.new_binary_sensor(config)
-    await cg.register_component(var, config)
-
+    # Check if we have a lambda first - determines which class to instantiate
     if lamb := config.get(CONF_LAMBDA):
+        # Use new_lambda_pvariable to create either TemplateBinarySensor or StatelessTemplateBinarySensor
         template_ = await cg.process_lambda(
             lamb, [], return_type=cg.optional.template(bool)
         )
-        cg.add(var.set_template(template_))
-    if condition := config.get(CONF_CONDITION):
+        var = automation.new_lambda_pvariable(
+            config[CONF_ID], template_, StatelessTemplateBinarySensor
+        )
+        # Manually register as binary sensor since we didn't use new_binary_sensor
+        await binary_sensor.register_binary_sensor(var, config)
+        await cg.register_component(var, config)
+    elif condition := config.get(CONF_CONDITION):
+        # For conditions, create stateful version and set template
+        var = await binary_sensor.new_binary_sensor(config)
+        await cg.register_component(var, config)
         condition = await automation.build_condition(
             condition, cg.TemplateArguments(), []
         )
@@ -42,6 +52,10 @@ async def to_code(config):
             f"return {condition.check()};", [], return_type=cg.optional.template(bool)
         )
         cg.add(var.set_template(template_))
+    else:
+        # No lambda or condition - just create the base template sensor
+        var = await binary_sensor.new_binary_sensor(config)
+        await cg.register_component(var, config)
 
 
 @automation.register_action(

esphome/components/template/binary_sensor/template_binary_sensor.cpp

@@ -6,18 +6,13 @@ namespace template_ {
 
 static const char *const TAG = "template.binary_sensor";
 
-void TemplateBinarySensor::setup() { this->loop(); }
-
-void TemplateBinarySensor::loop() {
-  if (this->f_ == nullptr)
-    return;
-
-  auto s = this->f_();
-  if (s.has_value()) {
-    this->publish_state(*s);
-  }
+// Template instantiations
+template<typename F> void TemplateBinarySensorBase<F>::dump_config() {
+  LOG_BINARY_SENSOR("", "Template Binary Sensor", this);
 }
-void TemplateBinarySensor::dump_config() { LOG_BINARY_SENSOR("", "Template Binary Sensor", this); }
+
+template class TemplateBinarySensorBase<std::function<optional<bool>()>>;
+template class TemplateBinarySensorBase<optional<bool> (*)()>;
 
 }  // namespace template_
 }  // namespace esphome

esphome/components/template/binary_sensor/template_binary_sensor.h

@@ -6,18 +6,41 @@
 namespace esphome {
 namespace template_ {
 
-class TemplateBinarySensor : public Component, public binary_sensor::BinarySensor {
+template<typename F> class TemplateBinarySensorBase : public Component, public binary_sensor::BinarySensor {
  public:
-  void set_template(std::function<optional<bool>()> &&f) { this->f_ = f; }
+  void setup() override { this->loop(); }
+
+  void loop() override {
+    if (this->f_ == nullptr)
+      return;
+    auto s = this->f_();
+    if (s.has_value()) {
+      this->publish_state(*s);
+    }
+  }
 
-  void setup() override;
-  void loop() override;
   void dump_config() override;
 
   float get_setup_priority() const override { return setup_priority::HARDWARE; }
 
  protected:
-  std::function<optional<bool>()> f_{nullptr};
+  F f_;
+};
+
+class TemplateBinarySensor : public TemplateBinarySensorBase<std::function<optional<bool>()>> {
+ public:
+  TemplateBinarySensor() { this->f_ = nullptr; }
+  void set_template(std::function<optional<bool>()> &&f) { this->f_ = f; }
+};
+
+/** Optimized template binary sensor 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 StatelessTemplateBinarySensor : public TemplateBinarySensorBase<optional<bool> (*)()> {
+ public:
+  explicit StatelessTemplateBinarySensor(optional<bool> (*f)()) { this->f_ = f; }
 };
 
 }  // namespace template_

esphome/components/template/cover/__init__.py

@@ -23,6 +23,9 @@ from esphome.const import (
 from .. import template_ns
 
 TemplateCover = template_ns.class_("TemplateCover", cover.Cover, cg.Component)
+StatelessTemplateCover = template_ns.class_(
+    "StatelessTemplateCover", cover.Cover, cg.Component
+)
 
 TemplateCoverRestoreMode = template_ns.enum("TemplateCoverRestoreMode")
 RESTORE_MODES = {
@@ -63,13 +66,22 @@ CONFIG_SCHEMA = (
 
 
 async def to_code(config):
-    var = await cover.new_cover(config)
-    await cg.register_component(var, config)
     if CONF_LAMBDA in config:
+        # Use new_lambda_pvariable to create either TemplateCover or StatelessTemplateCover
         template_ = await cg.process_lambda(
             config[CONF_LAMBDA], [], return_type=cg.optional.template(float)
         )
-        cg.add(var.set_state_lambda(template_))
+        var = automation.new_lambda_pvariable(
+            config[CONF_ID], template_, StatelessTemplateCover
+        )
+        # Manually register as cover since we didn't use new_cover
+        await cover.register_cover(var, config)
+        await cg.register_component(var, config)
+    else:
+        # No state lambda - just create the base template cover
+        var = await cover.new_cover(config)
+        await cg.register_component(var, config)
+
     if CONF_OPEN_ACTION in config:
         await automation.build_automation(
             var.get_open_trigger(), [], config[CONF_OPEN_ACTION]

esphome/components/template/cover/template_cover.cpp

@@ -8,14 +8,8 @@ using namespace esphome::cover;
 
 static const char *const TAG = "template.cover";
 
-TemplateCover::TemplateCover()
-    : open_trigger_(new Trigger<>()),
-      close_trigger_(new Trigger<>),
-      stop_trigger_(new Trigger<>()),
-      toggle_trigger_(new Trigger<>()),
-      position_trigger_(new Trigger<float>()),
-      tilt_trigger_(new Trigger<float>()) {}
-void TemplateCover::setup() {
+// Template instantiations
+template<typename StateF, typename TiltF> void TemplateCoverBase<StateF, TiltF>::setup() {
   switch (this->restore_mode_) {
     case COVER_NO_RESTORE:
       break;
@@ -34,43 +28,12 @@ void TemplateCover::setup() {
     }
   }
 }
-void TemplateCover::loop() {
-  bool changed = false;
 
-  if (this->state_f_.has_value()) {
-    auto s = (*this->state_f_)();
-    if (s.has_value()) {
-      auto pos = clamp(*s, 0.0f, 1.0f);
-      if (pos != this->position) {
-        this->position = pos;
-        changed = true;
-      }
-    }
-  }
-  if (this->tilt_f_.has_value()) {
-    auto s = (*this->tilt_f_)();
-    if (s.has_value()) {
-      auto tilt = clamp(*s, 0.0f, 1.0f);
-      if (tilt != this->tilt) {
-        this->tilt = tilt;
-        changed = true;
-      }
-    }
-  }
-
-  if (changed)
-    this->publish_state();
+template<typename StateF, typename TiltF> void TemplateCoverBase<StateF, TiltF>::dump_config() {
+  LOG_COVER("", "Template Cover", this);
 }
-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; }
-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_; }
-Trigger<> *TemplateCover::get_stop_trigger() const { return this->stop_trigger_; }
-Trigger<> *TemplateCover::get_toggle_trigger() const { return this->toggle_trigger_; }
-void TemplateCover::dump_config() { LOG_COVER("", "Template Cover", this); }
-void TemplateCover::control(const CoverCall &call) {
+
+template<typename StateF, typename TiltF> void TemplateCoverBase<StateF, TiltF>::control(const CoverCall &call) {
   if (call.get_stop()) {
     this->stop_prev_trigger_();
     this->stop_trigger_->trigger();
@@ -113,7 +76,8 @@ void TemplateCover::control(const CoverCall &call) {
 
   this->publish_state();
 }
-CoverTraits TemplateCover::get_traits() {
+
+template<typename StateF, typename TiltF> CoverTraits TemplateCoverBase<StateF, TiltF>::get_traits() {
   auto traits = CoverTraits();
   traits.set_is_assumed_state(this->assumed_state_);
   traits.set_supports_stop(this->has_stop_);
@@ -122,19 +86,16 @@ CoverTraits TemplateCover::get_traits() {
   traits.set_supports_tilt(this->has_tilt_);
   return 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_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; }
-void TemplateCover::set_has_tilt(bool has_tilt) { this->has_tilt_ = has_tilt; }
-void TemplateCover::stop_prev_trigger_() {
+
+template<typename StateF, typename TiltF> void TemplateCoverBase<StateF, TiltF>::stop_prev_trigger_() {
   if (this->prev_command_trigger_ != nullptr) {
     this->prev_command_trigger_->stop_action();
     this->prev_command_trigger_ = nullptr;
   }
 }
 
+template class TemplateCoverBase<std::function<optional<float>()>, std::function<optional<float>()>>;
+template class TemplateCoverBase<optional<float> (*)(), optional<float> (*)()>;
+
 }  // namespace template_
 }  // namespace esphome

esphome/components/template/cover/template_cover.h

@@ -13,31 +13,59 @@ enum TemplateCoverRestoreMode {
   COVER_RESTORE_AND_CALL,
 };
 
-class TemplateCover : public cover::Cover, public Component {
+template<typename StateF, typename TiltF> class TemplateCoverBase : public cover::Cover, public Component {
  public:
-  TemplateCover();
+  TemplateCoverBase()
+      : open_trigger_(new Trigger<>()),
+        close_trigger_(new Trigger<>()),
+        stop_trigger_(new Trigger<>()),
+        toggle_trigger_(new Trigger<>()),
+        position_trigger_(new Trigger<float>()),
+        tilt_trigger_(new Trigger<float>()) {}
 
-  void set_state_lambda(std::function<optional<float>()> &&f);
-  Trigger<> *get_open_trigger() const;
-  Trigger<> *get_close_trigger() const;
-  Trigger<> *get_stop_trigger() const;
-  Trigger<> *get_toggle_trigger() const;
-  Trigger<float> *get_position_trigger() const;
-  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_has_stop(bool has_stop);
-  void set_has_position(bool has_position);
-  void set_has_tilt(bool has_tilt);
-  void set_has_toggle(bool has_toggle);
-  void set_restore_mode(TemplateCoverRestoreMode restore_mode) { restore_mode_ = restore_mode; }
+  void loop() override {
+    bool changed = false;
+    if (this->state_f_.has_value()) {
+      auto s = (*this->state_f_)();
+      if (s.has_value()) {
+        auto pos = clamp(*s, 0.0f, 1.0f);
+        if (pos != this->position) {
+          this->position = pos;
+          changed = true;
+        }
+      }
+    }
+    if (this->tilt_f_.has_value()) {
+      auto s = (*this->tilt_f_)();
+      if (s.has_value()) {
+        auto tilt = clamp(*s, 0.0f, 1.0f);
+        if (tilt != this->tilt) {
+          this->tilt = tilt;
+          changed = true;
+        }
+      }
+    }
+    if (changed)
+      this->publish_state();
+  }
 
   void setup() override;
-  void loop() override;
   void dump_config() override;
+  float get_setup_priority() const override { return setup_priority::HARDWARE; }
 
-  float get_setup_priority() const override;
+  Trigger<> *get_open_trigger() const { return this->open_trigger_; }
+  Trigger<> *get_close_trigger() const { return this->close_trigger_; }
+  Trigger<> *get_stop_trigger() const { return this->stop_trigger_; }
+  Trigger<> *get_toggle_trigger() const { return this->toggle_trigger_; }
+  Trigger<float> *get_position_trigger() const { return this->position_trigger_; }
+  Trigger<float> *get_tilt_trigger() const { return this->tilt_trigger_; }
+  void set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
+  void set_assumed_state(bool assumed_state) { this->assumed_state_ = assumed_state; }
+  void set_has_stop(bool has_stop) { this->has_stop_ = has_stop; }
+  void set_has_position(bool has_position) { this->has_position_ = has_position; }
+  void set_has_tilt(bool has_tilt) { this->has_tilt_ = has_tilt; }
+  void set_has_toggle(bool has_toggle) { this->has_toggle_ = has_toggle; }
+  void set_restore_mode(TemplateCoverRestoreMode restore_mode) { restore_mode_ = restore_mode; }
 
  protected:
   void control(const cover::CoverCall &call) override;
@@ -45,8 +73,8 @@ class TemplateCover : public cover::Cover, public Component {
   void stop_prev_trigger_();
 
   TemplateCoverRestoreMode restore_mode_{COVER_RESTORE};
-  optional<std::function<optional<float>()>> state_f_;
-  optional<std::function<optional<float>()>> tilt_f_;
+  optional<StateF> state_f_;
+  optional<TiltF> tilt_f_;
   bool assumed_state_{false};
   bool optimistic_{false};
   Trigger<> *open_trigger_;
@@ -62,5 +90,22 @@ class TemplateCover : public cover::Cover, public Component {
   bool has_tilt_{false};
 };
 
+class TemplateCover : public TemplateCoverBase<std::function<optional<float>()>, std::function<optional<float>()>> {
+ public:
+  void set_state_lambda(std::function<optional<float>()> &&f) { this->state_f_ = f; }
+  void set_tilt_lambda(std::function<optional<float>()> &&tilt_f) { this->tilt_f_ = tilt_f; }
+};
+
+/** Optimized template cover for stateless lambdas (no capture).
+ *
+ * Uses function pointers instead of std::function to reduce memory overhead.
+ * Memory: 4 bytes (function pointer on 32-bit) vs 32 bytes (std::function) per lambda.
+ */
+class StatelessTemplateCover : public TemplateCoverBase<optional<float> (*)(), optional<float> (*)()> {
+ public:
+  explicit StatelessTemplateCover(optional<float> (*state_f)()) { this->state_f_ = state_f; }
+  void set_tilt_lambda(optional<float> (*tilt_f)()) { this->tilt_f_ = tilt_f; }
+};
+
 }  // namespace template_
 }  // namespace esphome

esphome/components/template/datetime/__init__.py

@@ -5,6 +5,7 @@ import esphome.config_validation as cv
 from esphome.const import (
     CONF_DAY,
     CONF_HOUR,
+    CONF_ID,
     CONF_INITIAL_VALUE,
     CONF_LAMBDA,
     CONF_MINUTE,
@@ -25,14 +26,23 @@ CODEOWNERS = ["@rfdarter"]
 TemplateDate = template_ns.class_(
     "TemplateDate", datetime.DateEntity, cg.PollingComponent
 )
+StatelessTemplateDate = template_ns.class_(
+    "StatelessTemplateDate", datetime.DateEntity, cg.PollingComponent
+)
 
 TemplateTime = template_ns.class_(
     "TemplateTime", datetime.TimeEntity, cg.PollingComponent
 )
+StatelessTemplateTime = template_ns.class_(
+    "StatelessTemplateTime", datetime.TimeEntity, cg.PollingComponent
+)
 
 TemplateDateTime = template_ns.class_(
     "TemplateDateTime", datetime.DateTimeEntity, cg.PollingComponent
 )
+StatelessTemplateDateTime = template_ns.class_(
+    "StatelessTemplateDateTime", datetime.DateTimeEntity, cg.PollingComponent
+)
 
 
 def validate(config):
@@ -99,15 +109,30 @@ CONFIG_SCHEMA = cv.All(
 
 
 async def to_code(config):
-    var = await datetime.new_datetime(config)
-
     if CONF_LAMBDA in config:
+        # Use new_lambda_pvariable to create either Template* or StatelessTemplate*
         template_ = await cg.process_lambda(
             config[CONF_LAMBDA], [], return_type=cg.optional.template(cg.ESPTime)
         )
-        cg.add(var.set_template(template_))
+        # Determine the appropriate stateless class based on type
+        if config[CONF_TYPE] == "DATE":
+            stateless_class = StatelessTemplateDate
+        elif config[CONF_TYPE] == "TIME":
+            stateless_class = StatelessTemplateTime
+        else:  # DATETIME
+            stateless_class = StatelessTemplateDateTime
 
+        var = automation.new_lambda_pvariable(
+            config[CONF_ID], template_, stateless_class
+        )
+        # Manually register as datetime since we didn't use new_datetime
+        await datetime.register_datetime(var, config)
+        await cg.register_component(var, config)
     else:
+        # No lambda - just create the base template datetime
+        var = await datetime.new_datetime(config)
+        await cg.register_component(var, config)
+
         cg.add(var.set_optimistic(config[CONF_OPTIMISTIC]))
         cg.add(var.set_restore_value(config[CONF_RESTORE_VALUE]))
 
@@ -146,5 +171,3 @@ async def to_code(config):
             [(cg.ESPTime, "x")],
             config[CONF_SET_ACTION],
         )
-
-    await cg.register_component(var, config)

esphome/components/template/datetime/template_date.cpp

@@ -9,7 +9,8 @@ namespace template_ {
 
 static const char *const TAG = "template.date";
 
-void TemplateDate::setup() {
+// Template instantiations
+template<typename F> void TemplateDateBase<F>::setup() {
   if (this->f_.has_value())
     return;
 
@@ -36,21 +37,7 @@ void TemplateDate::setup() {
   this->publish_state();
 }
 
-void TemplateDate::update() {
-  if (!this->f_.has_value())
-    return;
-
-  auto val = (*this->f_)();
-  if (!val.has_value())
-    return;
-
-  this->year_ = val->year;
-  this->month_ = val->month;
-  this->day_ = val->day_of_month;
-  this->publish_state();
-}
-
-void TemplateDate::control(const datetime::DateCall &call) {
+template<typename F> void TemplateDateBase<F>::control(const datetime::DateCall &call) {
   bool has_year = call.get_year().has_value();
   bool has_month = call.get_month().has_value();
   bool has_day = call.get_day().has_value();
@@ -99,12 +86,15 @@ void TemplateDate::control(const datetime::DateCall &call) {
   }
 }
 
-void TemplateDate::dump_config() {
+template<typename F> void TemplateDateBase<F>::dump_config() {
   LOG_DATETIME_DATE("", "Template Date", this);
   ESP_LOGCONFIG(TAG, "  Optimistic: %s", YESNO(this->optimistic_));
   LOG_UPDATE_INTERVAL(this);
 }
 
+template class TemplateDateBase<std::function<optional<ESPTime>()>>;
+template class TemplateDateBase<optional<ESPTime> (*)()>;
+
 }  // namespace template_
 }  // namespace esphome
 

esphome/components/template/datetime/template_date.h

@@ -13,12 +13,23 @@
 namespace esphome {
 namespace template_ {
 
-class TemplateDate : public datetime::DateEntity, public PollingComponent {
+template<typename F> class TemplateDateBase : public datetime::DateEntity, public PollingComponent {
  public:
-  void set_template(std::function<optional<ESPTime>()> &&f) { this->f_ = f; }
+  void update() override {
+    if (!this->f_.has_value())
+      return;
+
+    auto val = (*this->f_)();
+    if (!val.has_value())
+      return;
+
+    this->year_ = val->year;
+    this->month_ = val->month;
+    this->day_ = val->day_of_month;
+    this->publish_state();
+  }
 
   void setup() override;
-  void update() override;
   void dump_config() override;
   float get_setup_priority() const override { return setup_priority::HARDWARE; }
 
@@ -35,11 +46,26 @@ 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<F> f_;
 
   ESPPreferenceObject pref_;
 };
 
+class TemplateDate : public TemplateDateBase<std::function<optional<ESPTime>()>> {
+ public:
+  void set_template(std::function<optional<ESPTime>()> &&f) { this->f_ = f; }
+};
+
+/** Optimized template date for stateless lambdas (no capture).
+ *
+ * Uses function pointers instead of std::function to reduce memory overhead.
+ * Memory: 4 bytes (function pointer on 32-bit) vs 32 bytes (std::function) per lambda.
+ */
+class StatelessTemplateDate : public TemplateDateBase<optional<ESPTime> (*)()> {
+ public:
+  explicit StatelessTemplateDate(optional<ESPTime> (*f)()) { this->f_ = f; }
+};
+
 }  // namespace template_
 }  // namespace esphome
 

esphome/components/template/datetime/template_datetime.cpp

@@ -9,7 +9,8 @@ namespace template_ {
 
 static const char *const TAG = "template.datetime";
 
-void TemplateDateTime::setup() {
+// Template instantiations
+template<typename F> void TemplateDateTimeBase<F>::setup() {
   if (this->f_.has_value())
     return;
 
@@ -39,24 +40,7 @@ void TemplateDateTime::setup() {
   this->publish_state();
 }
 
-void TemplateDateTime::update() {
-  if (!this->f_.has_value())
-    return;
-
-  auto val = (*this->f_)();
-  if (!val.has_value())
-    return;
-
-  this->year_ = val->year;
-  this->month_ = val->month;
-  this->day_ = val->day_of_month;
-  this->hour_ = val->hour;
-  this->minute_ = val->minute;
-  this->second_ = val->second;
-  this->publish_state();
-}
-
-void TemplateDateTime::control(const datetime::DateTimeCall &call) {
+template<typename F> void TemplateDateTimeBase<F>::control(const datetime::DateTimeCall &call) {
   bool has_year = call.get_year().has_value();
   bool has_month = call.get_month().has_value();
   bool has_day = call.get_day().has_value();
@@ -138,12 +122,15 @@ void TemplateDateTime::control(const datetime::DateTimeCall &call) {
   }
 }
 
-void TemplateDateTime::dump_config() {
+template<typename F> void TemplateDateTimeBase<F>::dump_config() {
   LOG_DATETIME_DATETIME("", "Template DateTime", this);
   ESP_LOGCONFIG(TAG, "  Optimistic: %s", YESNO(this->optimistic_));
   LOG_UPDATE_INTERVAL(this);
 }
 
+template class TemplateDateTimeBase<std::function<optional<ESPTime>()>>;
+template class TemplateDateTimeBase<optional<ESPTime> (*)()>;
+
 }  // namespace template_
 }  // namespace esphome
 

esphome/components/template/datetime/template_datetime.h

@@ -13,12 +13,26 @@
 namespace esphome {
 namespace template_ {
 
-class TemplateDateTime : public datetime::DateTimeEntity, public PollingComponent {
+template<typename F> class TemplateDateTimeBase : public datetime::DateTimeEntity, public PollingComponent {
  public:
-  void set_template(std::function<optional<ESPTime>()> &&f) { this->f_ = f; }
+  void update() override {
+    if (!this->f_.has_value())
+      return;
+
+    auto val = (*this->f_)();
+    if (!val.has_value())
+      return;
+
+    this->year_ = val->year;
+    this->month_ = val->month;
+    this->day_ = val->day_of_month;
+    this->hour_ = val->hour;
+    this->minute_ = val->minute;
+    this->second_ = val->second;
+    this->publish_state();
+  }
 
   void setup() override;
-  void update() override;
   void dump_config() override;
   float get_setup_priority() const override { return setup_priority::HARDWARE; }
 
@@ -35,11 +49,26 @@ 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<F> f_;
 
   ESPPreferenceObject pref_;
 };
 
+class TemplateDateTime : public TemplateDateTimeBase<std::function<optional<ESPTime>()>> {
+ public:
+  void set_template(std::function<optional<ESPTime>()> &&f) { this->f_ = f; }
+};
+
+/** Optimized template datetime for stateless lambdas (no capture).
+ *
+ * Uses function pointers instead of std::function to reduce memory overhead.
+ * Memory: 4 bytes (function pointer on 32-bit) vs 32 bytes (std::function) per lambda.
+ */
+class StatelessTemplateDateTime : public TemplateDateTimeBase<optional<ESPTime> (*)()> {
+ public:
+  explicit StatelessTemplateDateTime(optional<ESPTime> (*f)()) { this->f_ = f; }
+};
+
 }  // namespace template_
 }  // namespace esphome
 

esphome/components/template/datetime/template_time.cpp

@@ -9,7 +9,8 @@ namespace template_ {
 
 static const char *const TAG = "template.time";
 
-void TemplateTime::setup() {
+// Template instantiations
+template<typename F> void TemplateTimeBase<F>::setup() {
   if (this->f_.has_value())
     return;
 
@@ -36,21 +37,7 @@ void TemplateTime::setup() {
   this->publish_state();
 }
 
-void TemplateTime::update() {
-  if (!this->f_.has_value())
-    return;
-
-  auto val = (*this->f_)();
-  if (!val.has_value())
-    return;
-
-  this->hour_ = val->hour;
-  this->minute_ = val->minute;
-  this->second_ = val->second;
-  this->publish_state();
-}
-
-void TemplateTime::control(const datetime::TimeCall &call) {
+template<typename F> void TemplateTimeBase<F>::control(const datetime::TimeCall &call) {
   bool has_hour = call.get_hour().has_value();
   bool has_minute = call.get_minute().has_value();
   bool has_second = call.get_second().has_value();
@@ -99,12 +86,15 @@ void TemplateTime::control(const datetime::TimeCall &call) {
   }
 }
 
-void TemplateTime::dump_config() {
+template<typename F> void TemplateTimeBase<F>::dump_config() {
   LOG_DATETIME_TIME("", "Template Time", this);
   ESP_LOGCONFIG(TAG, "  Optimistic: %s", YESNO(this->optimistic_));
   LOG_UPDATE_INTERVAL(this);
 }
 
+template class TemplateTimeBase<std::function<optional<ESPTime>()>>;
+template class TemplateTimeBase<optional<ESPTime> (*)()>;
+
 }  // namespace template_
 }  // namespace esphome
 

esphome/components/template/datetime/template_time.h

@@ -13,12 +13,23 @@
 namespace esphome {
 namespace template_ {
 
-class TemplateTime : public datetime::TimeEntity, public PollingComponent {
+template<typename F> class TemplateTimeBase : public datetime::TimeEntity, public PollingComponent {
  public:
-  void set_template(std::function<optional<ESPTime>()> &&f) { this->f_ = f; }
+  void update() override {
+    if (!this->f_.has_value())
+      return;
+
+    auto val = (*this->f_)();
+    if (!val.has_value())
+      return;
+
+    this->hour_ = val->hour;
+    this->minute_ = val->minute;
+    this->second_ = val->second;
+    this->publish_state();
+  }
 
   void setup() override;
-  void update() override;
   void dump_config() override;
   float get_setup_priority() const override { return setup_priority::HARDWARE; }
 
@@ -35,11 +46,26 @@ 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<F> f_;
 
   ESPPreferenceObject pref_;
 };
 
+class TemplateTime : public TemplateTimeBase<std::function<optional<ESPTime>()>> {
+ public:
+  void set_template(std::function<optional<ESPTime>()> &&f) { this->f_ = f; }
+};
+
+/** Optimized template time for stateless lambdas (no capture).
+ *
+ * Uses function pointers instead of std::function to reduce memory overhead.
+ * Memory: 4 bytes (function pointer on 32-bit) vs 32 bytes (std::function) per lambda.
+ */
+class StatelessTemplateTime : public TemplateTimeBase<optional<ESPTime> (*)()> {
+ public:
+  explicit StatelessTemplateTime(optional<ESPTime> (*f)()) { this->f_ = f; }
+};
+
 }  // namespace template_
 }  // namespace esphome
 

esphome/components/template/fan/template_fan.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include <set>
+#include <vector>
 
 #include "esphome/core/component.h"
 #include "esphome/components/fan/fan.h"
@@ -16,7 +16,7 @@ class TemplateFan : public Component, public fan::Fan {
   void set_has_direction(bool has_direction) { this->has_direction_ = has_direction; }
   void set_has_oscillating(bool has_oscillating) { this->has_oscillating_ = has_oscillating; }
   void set_speed_count(int count) { this->speed_count_ = count; }
-  void set_preset_modes(const std::set<std::string> &presets) { this->preset_modes_ = presets; }
+  void set_preset_modes(const std::initializer_list<std::string> &presets) { this->preset_modes_ = presets; }
   fan::FanTraits get_traits() override { return this->traits_; }
 
  protected:
@@ -26,7 +26,7 @@ class TemplateFan : public Component, public fan::Fan {
   bool has_direction_{false};
   int speed_count_{0};
   fan::FanTraits traits_;
-  std::set<std::string> preset_modes_{};
+  std::vector<std::string> preset_modes_{};
 };
 
 }  // namespace template_

esphome/components/template/lock/__init__.py

@@ -16,6 +16,9 @@ from esphome.const import (
 from .. import template_ns
 
 TemplateLock = template_ns.class_("TemplateLock", lock.Lock, cg.Component)
+StatelessTemplateLock = template_ns.class_(
+    "StatelessTemplateLock", lock.Lock, cg.Component
+)
 
 TemplateLockPublishAction = template_ns.class_(
     "TemplateLockPublishAction",
@@ -55,14 +58,22 @@ CONFIG_SCHEMA = cv.All(
 
 
 async def to_code(config):
-    var = await lock.new_lock(config)
-    await cg.register_component(var, config)
-
     if CONF_LAMBDA in config:
+        # Use new_lambda_pvariable to create either TemplateLock or StatelessTemplateLock
         template_ = await cg.process_lambda(
             config[CONF_LAMBDA], [], return_type=cg.optional.template(lock.LockState)
         )
-        cg.add(var.set_state_lambda(template_))
+        var = automation.new_lambda_pvariable(
+            config[CONF_ID], template_, StatelessTemplateLock
+        )
+        # Manually register as lock since we didn't use new_lock
+        await lock.register_lock(var, config)
+        await cg.register_component(var, config)
+    else:
+        # No lambda - just create the base template lock
+        var = await lock.new_lock(config)
+        await cg.register_component(var, config)
+
     if CONF_UNLOCK_ACTION in config:
         await automation.build_automation(
             var.get_unlock_trigger(), [], config[CONF_UNLOCK_ACTION]

esphome/components/template/lock/template_lock.cpp

@@ -8,19 +8,8 @@ using namespace esphome::lock;
 
 static const char *const TAG = "template.lock";
 
-TemplateLock::TemplateLock()
-    : lock_trigger_(new Trigger<>()), unlock_trigger_(new Trigger<>()), open_trigger_(new Trigger<>()) {}
-
-void TemplateLock::loop() {
-  if (!this->f_.has_value())
-    return;
-  auto val = (*this->f_)();
-  if (!val.has_value())
-    return;
-
-  this->publish_state(*val);
-}
-void TemplateLock::control(const lock::LockCall &call) {
+// Template instantiations
+template<typename F> void TemplateLockBase<F>::control(const lock::LockCall &call) {
   if (this->prev_trigger_ != nullptr) {
     this->prev_trigger_->stop_action();
   }
@@ -37,23 +26,22 @@ void TemplateLock::control(const lock::LockCall &call) {
   if (this->optimistic_)
     this->publish_state(state);
 }
-void TemplateLock::open_latch() {
+
+template<typename F> void TemplateLockBase<F>::open_latch() {
   if (this->prev_trigger_ != nullptr) {
     this->prev_trigger_->stop_action();
   }
   this->prev_trigger_ = this->open_trigger_;
   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; }
-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_; }
-Trigger<> *TemplateLock::get_open_trigger() const { return this->open_trigger_; }
-void TemplateLock::dump_config() {
+
+template<typename F> void TemplateLockBase<F>::dump_config() {
   LOG_LOCK("", "Template Lock", this);
   ESP_LOGCONFIG(TAG, "  Optimistic: %s", YESNO(this->optimistic_));
 }
 
+template class TemplateLockBase<std::function<optional<lock::LockState>()>>;
+template class TemplateLockBase<optional<lock::LockState> (*)()>;
+
 }  // namespace template_
 }  // namespace esphome

esphome/components/template/lock/template_lock.h

@@ -7,26 +7,35 @@
 namespace esphome {
 namespace template_ {
 
-class TemplateLock : public lock::Lock, public Component {
+template<typename F> class TemplateLockBase : public lock::Lock, public Component {
  public:
-  TemplateLock();
+  TemplateLockBase()
+      : lock_trigger_(new Trigger<>()), unlock_trigger_(new Trigger<>()), open_trigger_(new Trigger<>()) {}
+
+  void loop() override {
+    if (!this->f_.has_value())
+      return;
+    auto val = (*this->f_)();
+    if (!val.has_value())
+      return;
+
+    this->publish_state(*val);
+  }
 
   void dump_config() override;
 
-  void set_state_lambda(std::function<optional<lock::LockState>()> &&f);
-  Trigger<> *get_lock_trigger() const;
-  Trigger<> *get_unlock_trigger() const;
-  Trigger<> *get_open_trigger() const;
-  void set_optimistic(bool optimistic);
-  void loop() override;
+  Trigger<> *get_lock_trigger() const { return this->lock_trigger_; }
+  Trigger<> *get_unlock_trigger() const { return this->unlock_trigger_; }
+  Trigger<> *get_open_trigger() const { return this->open_trigger_; }
+  void set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
 
-  float get_setup_priority() const override;
+  float get_setup_priority() const override { return setup_priority::HARDWARE; }
 
  protected:
   void control(const lock::LockCall &call) override;
   void open_latch() override;
 
-  optional<std::function<optional<lock::LockState>()>> f_;
+  optional<F> f_;
   bool optimistic_{false};
   Trigger<> *lock_trigger_;
   Trigger<> *unlock_trigger_;
@@ -34,5 +43,20 @@ class TemplateLock : public lock::Lock, public Component {
   Trigger<> *prev_trigger_{nullptr};
 };
 
+class TemplateLock : public TemplateLockBase<std::function<optional<lock::LockState>()>> {
+ public:
+  void set_state_lambda(std::function<optional<lock::LockState>()> &&f) { this->f_ = f; }
+};
+
+/** Optimized template lock for stateless lambdas (no capture).
+ *
+ * Uses function pointers instead of std::function to reduce memory overhead.
+ * Memory: 4 bytes (function pointer on 32-bit) vs 32 bytes (std::function) per lambda.
+ */
+class StatelessTemplateLock : public TemplateLockBase<optional<lock::LockState> (*)()> {
+ public:
+  explicit StatelessTemplateLock(optional<lock::LockState> (*f)()) { this->f_ = f; }
+};
+
 }  // namespace template_
 }  // namespace esphome

esphome/components/template/number/__init__.py

@@ -19,6 +19,9 @@ from .. import template_ns
 TemplateNumber = template_ns.class_(
     "TemplateNumber", number.Number, cg.PollingComponent
 )
+StatelessTemplateNumber = template_ns.class_(
+    "StatelessTemplateNumber", number.Number, cg.PollingComponent
+)
 
 
 def validate_min_max(config):
@@ -66,23 +69,33 @@ CONFIG_SCHEMA = cv.All(
 
 
 async def to_code(config):
-    var = cg.new_Pvariable(config[CONF_ID])
-    await cg.register_component(var, config)
-    await number.register_number(
-        var,
-        config,
-        min_value=config[CONF_MIN_VALUE],
-        max_value=config[CONF_MAX_VALUE],
-        step=config[CONF_STEP],
-    )
-
     if CONF_LAMBDA in config:
+        # Use new_lambda_pvariable to create either TemplateNumber or StatelessTemplateNumber
         template_ = await cg.process_lambda(
             config[CONF_LAMBDA], [], return_type=cg.optional.template(float)
         )
-        cg.add(var.set_template(template_))
-
+        var = automation.new_lambda_pvariable(
+            config[CONF_ID], template_, StatelessTemplateNumber
+        )
+        await cg.register_component(var, config)
+        await number.register_number(
+            var,
+            config,
+            min_value=config[CONF_MIN_VALUE],
+            max_value=config[CONF_MAX_VALUE],
+            step=config[CONF_STEP],
+        )
     else:
+        # No lambda - just create the base template number
+        var = cg.new_Pvariable(config[CONF_ID])
+        await cg.register_component(var, config)
+        await number.register_number(
+            var,
+            config,
+            min_value=config[CONF_MIN_VALUE],
+            max_value=config[CONF_MAX_VALUE],
+            step=config[CONF_STEP],
+        )
         cg.add(var.set_optimistic(config[CONF_OPTIMISTIC]))
         cg.add(var.set_initial_value(config[CONF_INITIAL_VALUE]))
         if CONF_RESTORE_VALUE in config:

esphome/components/template/number/template_number.cpp

@@ -6,7 +6,8 @@ namespace template_ {
 
 static const char *const TAG = "template.number";
 
-void TemplateNumber::setup() {
+// Template instantiations
+template<typename F> void TemplateNumberBase<F>::setup() {
   if (this->f_.has_value())
     return;
 
@@ -26,18 +27,7 @@ void TemplateNumber::setup() {
   this->publish_state(value);
 }
 
-void TemplateNumber::update() {
-  if (!this->f_.has_value())
-    return;
-
-  auto val = (*this->f_)();
-  if (!val.has_value())
-    return;
-
-  this->publish_state(*val);
-}
-
-void TemplateNumber::control(float value) {
+template<typename F> void TemplateNumberBase<F>::control(float value) {
   this->set_trigger_->trigger(value);
 
   if (this->optimistic_)
@@ -46,11 +36,15 @@ void TemplateNumber::control(float value) {
   if (this->restore_value_)
     this->pref_.save(&value);
 }
-void TemplateNumber::dump_config() {
+
+template<typename F> void TemplateNumberBase<F>::dump_config() {
   LOG_NUMBER("", "Template Number", this);
   ESP_LOGCONFIG(TAG, "  Optimistic: %s", YESNO(this->optimistic_));
   LOG_UPDATE_INTERVAL(this);
 }
 
+template class TemplateNumberBase<std::function<optional<float>()>>;
+template class TemplateNumberBase<optional<float> (*)()>;
+
 }  // namespace template_
 }  // namespace esphome

esphome/components/template/number/template_number.h

@@ -8,13 +8,22 @@
 namespace esphome {
 namespace template_ {
 
-class TemplateNumber : public number::Number, public PollingComponent {
+template<typename F> class TemplateNumberBase : public number::Number, public PollingComponent {
  public:
-  void set_template(std::function<optional<float>()> &&f) { this->f_ = f; }
+  TemplateNumberBase() : set_trigger_(new Trigger<float>()) {}
 
   void setup() override;
-  void update() override;
   void dump_config() override;
+
+  void update() override {
+    if (!this->f_.has_value())
+      return;
+    auto val = (*this->f_)();
+    if (!val.has_value())
+      return;
+    this->publish_state(*val);
+  }
+
   float get_setup_priority() const override { return setup_priority::HARDWARE; }
 
   Trigger<float> *get_set_trigger() const { return set_trigger_; }
@@ -27,11 +36,26 @@ class TemplateNumber : public number::Number, public PollingComponent {
   bool optimistic_{false};
   float initial_value_{NAN};
   bool restore_value_{false};
-  Trigger<float> *set_trigger_ = new Trigger<float>();
-  optional<std::function<optional<float>()>> f_;
+  Trigger<float> *set_trigger_;
+  optional<F> f_;
 
   ESPPreferenceObject pref_;
 };
 
+class TemplateNumber : public TemplateNumberBase<std::function<optional<float>()>> {
+ public:
+  void set_template(std::function<optional<float>()> &&f) { this->f_ = f; }
+};
+
+/** Optimized template number 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 StatelessTemplateNumber : public TemplateNumberBase<optional<float> (*)()> {
+ public:
+  explicit StatelessTemplateNumber(optional<float> (*f)()) { this->f_ = f; }
+};
+
 }  // namespace template_
 }  // namespace esphome

esphome/components/template/select/__init__.py

@@ -17,6 +17,9 @@ from .. import template_ns
 TemplateSelect = template_ns.class_(
     "TemplateSelect", select.Select, cg.PollingComponent
 )
+StatelessTemplateSelect = template_ns.class_(
+    "StatelessTemplateSelect", select.Select, cg.PollingComponent
+)
 
 
 def validate(config):
@@ -62,22 +65,34 @@ CONFIG_SCHEMA = cv.All(
 
 
 async def to_code(config):
-    var = cg.new_Pvariable(config[CONF_ID])
-    await cg.register_component(var, config)
-    await select.register_select(var, config, options=config[CONF_OPTIONS])
-
     if CONF_LAMBDA in config:
+        # Use new_lambda_pvariable to create either TemplateSelect or StatelessTemplateSelect
         template_ = await cg.process_lambda(
             config[CONF_LAMBDA], [], return_type=cg.optional.template(cg.std_string)
         )
-        cg.add(var.set_template(template_))
-
+        var = automation.new_lambda_pvariable(
+            config[CONF_ID], template_, StatelessTemplateSelect
+        )
+        await cg.register_component(var, config)
+        await select.register_select(var, config, options=config[CONF_OPTIONS])
     else:
-        cg.add(var.set_optimistic(config[CONF_OPTIMISTIC]))
-        cg.add(var.set_initial_option(config[CONF_INITIAL_OPTION]))
+        # No lambda - just create the base template select
+        var = cg.new_Pvariable(config[CONF_ID])
+        await cg.register_component(var, config)
+        await select.register_select(var, config, options=config[CONF_OPTIONS])
 
-        if CONF_RESTORE_VALUE in config:
-            cg.add(var.set_restore_value(config[CONF_RESTORE_VALUE]))
+        # Only set if non-default to avoid bloating setup() function
+        if config[CONF_OPTIMISTIC]:
+            cg.add(var.set_optimistic(True))
+        initial_option_index = config[CONF_OPTIONS].index(config[CONF_INITIAL_OPTION])
+        # Only set if non-zero to avoid bloating setup() function
+        # (initial_option_index_ is zero-initialized in the header)
+        if initial_option_index != 0:
+            cg.add(var.set_initial_option_index(initial_option_index))
+
+        # Only set if True (default is False)
+        if config.get(CONF_RESTORE_VALUE):
+            cg.add(var.set_restore_value(True))
 
     if CONF_SET_ACTION in config:
         await automation.build_automation(

esphome/components/template/select/template_select.cpp

@@ -6,49 +6,29 @@ namespace template_ {
 
 static const char *const TAG = "template.select";
 
-void TemplateSelect::setup() {
+// Template instantiations
+template<typename F> void TemplateSelectBase<F>::setup() {
   if (this->f_.has_value())
     return;
 
-  std::string value;
-  if (!this->restore_value_) {
-    value = this->initial_option_;
-    ESP_LOGD(TAG, "State from initial: %s", value.c_str());
-  } else {
-    size_t index;
+  size_t index = this->initial_option_index_;
+  if (this->restore_value_) {
     this->pref_ = global_preferences->make_preference<size_t>(this->get_preference_hash());
-    if (!this->pref_.load(&index)) {
-      value = this->initial_option_;
-      ESP_LOGD(TAG, "State from initial (could not load stored index): %s", value.c_str());
-    } else if (!this->has_index(index)) {
-      value = this->initial_option_;
-      ESP_LOGD(TAG, "State from initial (restored index %d out of bounds): %s", index, value.c_str());
+    size_t restored_index;
+    if (this->pref_.load(&restored_index) && this->has_index(restored_index)) {
+      index = restored_index;
+      ESP_LOGD(TAG, "State from restore: %s", this->at(index).value().c_str());
     } else {
-      value = this->at(index).value();
-      ESP_LOGD(TAG, "State from restore: %s", value.c_str());
+      ESP_LOGD(TAG, "State from initial (could not load or invalid stored index): %s", this->at(index).value().c_str());
     }
+  } else {
+    ESP_LOGD(TAG, "State from initial: %s", this->at(index).value().c_str());
   }
 
-  this->publish_state(value);
+  this->publish_state(this->at(index).value());
 }
 
-void TemplateSelect::update() {
-  if (!this->f_.has_value())
-    return;
-
-  auto val = (*this->f_)();
-  if (!val.has_value())
-    return;
-
-  if (!this->has_option(*val)) {
-    ESP_LOGE(TAG, "Lambda returned an invalid option: %s", (*val).c_str());
-    return;
-  }
-
-  this->publish_state(*val);
-}
-
-void TemplateSelect::control(const std::string &value) {
+template<typename F> void TemplateSelectBase<F>::control(const std::string &value) {
   this->set_trigger_->trigger(value);
 
   if (this->optimistic_)
@@ -60,7 +40,7 @@ void TemplateSelect::control(const std::string &value) {
   }
 }
 
-void TemplateSelect::dump_config() {
+template<typename F> void TemplateSelectBase<F>::dump_config() {
   LOG_SELECT("", "Template Select", this);
   LOG_UPDATE_INTERVAL(this);
   if (this->f_.has_value())
@@ -69,8 +49,12 @@ void TemplateSelect::dump_config() {
                 "  Optimistic: %s\n"
                 "  Initial Option: %s\n"
                 "  Restore Value: %s",
-                YESNO(this->optimistic_), this->initial_option_.c_str(), YESNO(this->restore_value_));
+                YESNO(this->optimistic_), this->at(this->initial_option_index_).value().c_str(),
+                YESNO(this->restore_value_));
 }
 
+template class TemplateSelectBase<std::function<optional<std::string>()>>;
+template class TemplateSelectBase<optional<std::string> (*)()>;
+
 }  // namespace template_
 }  // namespace esphome

esphome/components/template/select/template_select.h

@@ -8,30 +8,58 @@
 namespace esphome {
 namespace template_ {
 
-class TemplateSelect : public select::Select, public PollingComponent {
+template<typename F> class TemplateSelectBase : public select::Select, public PollingComponent {
  public:
-  void set_template(std::function<optional<std::string>()> &&f) { this->f_ = f; }
+  TemplateSelectBase() : set_trigger_(new Trigger<std::string>()) {}
 
   void setup() override;
-  void update() override;
   void dump_config() override;
+
+  void update() override {
+    if (!this->f_.has_value())
+      return;
+    auto val = (*this->f_)();
+    if (!val.has_value())
+      return;
+    if (!this->has_option(*val)) {
+      ESP_LOGE("template.select", "Lambda returned an invalid option: %s", (*val).c_str());
+      return;
+    }
+    this->publish_state(*val);
+  }
+
   float get_setup_priority() const override { return setup_priority::HARDWARE; }
 
   Trigger<std::string> *get_set_trigger() const { return this->set_trigger_; }
   void set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
-  void set_initial_option(const std::string &initial_option) { this->initial_option_ = initial_option; }
+  void set_initial_option_index(size_t initial_option_index) { this->initial_option_index_ = initial_option_index; }
   void set_restore_value(bool restore_value) { this->restore_value_ = restore_value; }
 
  protected:
   void control(const std::string &value) override;
   bool optimistic_ = false;
-  std::string initial_option_;
+  size_t initial_option_index_{0};
   bool restore_value_ = false;
-  Trigger<std::string> *set_trigger_ = new Trigger<std::string>();
-  optional<std::function<optional<std::string>()>> f_;
+  Trigger<std::string> *set_trigger_;
+  optional<F> f_;
 
   ESPPreferenceObject pref_;
 };
 
+class TemplateSelect : public TemplateSelectBase<std::function<optional<std::string>()>> {
+ public:
+  void set_template(std::function<optional<std::string>()> &&f) { this->f_ = f; }
+};
+
+/** Optimized template select 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 StatelessTemplateSelect : public TemplateSelectBase<optional<std::string> (*)()> {
+ public:
+  explicit StatelessTemplateSelect(optional<std::string> (*f)()) { this->f_ = f; }
+};
+
 }  // namespace template_
 }  // namespace esphome

esphome/components/template/sensor/__init__.py

@@ -9,6 +9,9 @@ from .. import template_ns
 TemplateSensor = template_ns.class_(
     "TemplateSensor", sensor.Sensor, cg.PollingComponent
 )
+StatelessTemplateSensor = template_ns.class_(
+    "StatelessTemplateSensor", sensor.Sensor, cg.PollingComponent
+)
 
 CONFIG_SCHEMA = (
     sensor.sensor_schema(
@@ -25,14 +28,21 @@ CONFIG_SCHEMA = (
 
 
 async def to_code(config):
-    var = await sensor.new_sensor(config)
-    await cg.register_component(var, config)
-
     if CONF_LAMBDA in config:
+        # Use new_lambda_pvariable to create either TemplateSensor or StatelessTemplateSensor
         template_ = await cg.process_lambda(
             config[CONF_LAMBDA], [], return_type=cg.optional.template(float)
         )
-        cg.add(var.set_template(template_))
+        var = automation.new_lambda_pvariable(
+            config[CONF_ID], template_, StatelessTemplateSensor
+        )
+        # Manually register as sensor since we didn't use new_sensor
+        await sensor.register_sensor(var, config)
+        await cg.register_component(var, config)
+    else:
+        # No lambda - just create the base template sensor
+        var = await sensor.new_sensor(config)
+        await cg.register_component(var, config)
 
 
 @automation.register_action(

esphome/components/template/sensor/template_sensor.cpp

@@ -7,21 +7,14 @@ namespace template_ {
 
 static const char *const TAG = "template.sensor";
 
-void TemplateSensor::update() {
-  if (!this->f_.has_value())
-    return;
-
-  auto val = (*this->f_)();
-  if (val.has_value()) {
-    this->publish_state(*val);
-  }
-}
-float TemplateSensor::get_setup_priority() const { return setup_priority::HARDWARE; }
-void TemplateSensor::set_template(std::function<optional<float>()> &&f) { this->f_ = f; }
-void TemplateSensor::dump_config() {
+// Template instantiations
+template<typename F> void TemplateSensorBase<F>::dump_config() {
   LOG_SENSOR("", "Template Sensor", this);
   LOG_UPDATE_INTERVAL(this);
 }
 
+template class TemplateSensorBase<std::function<optional<float>()>>;
+template class TemplateSensorBase<optional<float> (*)()>;
+
 }  // namespace template_
 }  // namespace esphome

esphome/components/template/sensor/template_sensor.h

@@ -6,18 +6,38 @@
 namespace esphome {
 namespace template_ {
 
-class TemplateSensor : public sensor::Sensor, public PollingComponent {
+template<typename F> class TemplateSensorBase : public sensor::Sensor, public PollingComponent {
  public:
-  void set_template(std::function<optional<float>()> &&f);
-
-  void update() override;
+  void update() override {
+    if (!this->f_.has_value())
+      return;
+    auto val = (*this->f_)();
+    if (val.has_value()) {
+      this->publish_state(*val);
+    }
+  }
 
   void dump_config() override;
 
-  float get_setup_priority() const override;
+  float get_setup_priority() const override { return setup_priority::HARDWARE; }
 
  protected:
-  optional<std::function<optional<float>()>> f_;
+  optional<F> f_;
+};
+
+class TemplateSensor : public TemplateSensorBase<std::function<optional<float>()>> {
+ public:
+  void set_template(std::function<optional<float>()> &&f) { this->f_ = f; }
+};
+
+/** Optimized template sensor 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 StatelessTemplateSensor : public TemplateSensorBase<optional<float> (*)()> {
+ public:
+  explicit StatelessTemplateSensor(optional<float> (*f)()) { this->f_ = f; }
 };
 
 }  // namespace template_

esphome/components/template/switch/__init__.py

@@ -16,6 +16,9 @@ from esphome.const import (
 from .. import template_ns
 
 TemplateSwitch = template_ns.class_("TemplateSwitch", switch.Switch, cg.Component)
+StatelessTemplateSwitch = template_ns.class_(
+    "StatelessTemplateSwitch", switch.Switch, cg.Component
+)
 
 
 def validate(config):
@@ -55,14 +58,22 @@ CONFIG_SCHEMA = cv.All(
 
 
 async def to_code(config):
-    var = await switch.new_switch(config)
-    await cg.register_component(var, config)
-
     if CONF_LAMBDA in config:
+        # Use new_lambda_pvariable to create either TemplateSwitch or StatelessTemplateSwitch
         template_ = await cg.process_lambda(
             config[CONF_LAMBDA], [], return_type=cg.optional.template(bool)
         )
-        cg.add(var.set_state_lambda(template_))
+        var = automation.new_lambda_pvariable(
+            config[CONF_ID], template_, StatelessTemplateSwitch
+        )
+        # Manually register as switch since we didn't use new_switch
+        await switch.register_switch(var, config)
+        await cg.register_component(var, config)
+    else:
+        # No lambda - just create the base template switch
+        var = await switch.new_switch(config)
+        await cg.register_component(var, config)
+
     if CONF_TURN_OFF_ACTION in config:
         await automation.build_automation(
             var.get_turn_off_trigger(), [], config[CONF_TURN_OFF_ACTION]

esphome/components/template/switch/template_switch.cpp

@@ -6,18 +6,8 @@ namespace template_ {
 
 static const char *const TAG = "template.switch";
 
-TemplateSwitch::TemplateSwitch() : turn_on_trigger_(new Trigger<>()), turn_off_trigger_(new Trigger<>()) {}
-
-void TemplateSwitch::loop() {
-  if (!this->f_.has_value())
-    return;
-  auto s = (*this->f_)();
-  if (!s.has_value())
-    return;
-
-  this->publish_state(*s);
-}
-void TemplateSwitch::write_state(bool state) {
+// Template instantiations
+template<typename F> void TemplateSwitchBase<F>::write_state(bool state) {
   if (this->prev_trigger_ != nullptr) {
     this->prev_trigger_->stop_action();
   }
@@ -33,13 +23,8 @@ void TemplateSwitch::write_state(bool state) {
   if (this->optimistic_)
     this->publish_state(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; }
-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_; }
-void TemplateSwitch::setup() {
+
+template<typename F> void TemplateSwitchBase<F>::setup() {
   optional<bool> initial_state = this->get_initial_state_with_restore_mode();
 
   if (initial_state.has_value()) {
@@ -52,11 +37,14 @@ void TemplateSwitch::setup() {
     }
   }
 }
-void TemplateSwitch::dump_config() {
+
+template<typename F> void TemplateSwitchBase<F>::dump_config() {
   LOG_SWITCH("", "Template Switch", this);
   ESP_LOGCONFIG(TAG, "  Optimistic: %s", YESNO(this->optimistic_));
 }
-void TemplateSwitch::set_assumed_state(bool assumed_state) { this->assumed_state_ = assumed_state; }
+
+template class TemplateSwitchBase<std::function<optional<bool>()>>;
+template class TemplateSwitchBase<optional<bool> (*)()>;
 
 }  // namespace template_
 }  // namespace esphome

esphome/components/template/switch/template_switch.h

@@ -7,28 +7,35 @@
 namespace esphome {
 namespace template_ {
 
-class TemplateSwitch : public switch_::Switch, public Component {
+template<typename F> class TemplateSwitchBase : public switch_::Switch, public Component {
  public:
-  TemplateSwitch();
+  TemplateSwitchBase() : turn_on_trigger_(new Trigger<>()), turn_off_trigger_(new Trigger<>()) {}
 
   void setup() override;
   void dump_config() override;
 
-  void set_state_lambda(std::function<optional<bool>()> &&f);
-  Trigger<> *get_turn_on_trigger() const;
-  Trigger<> *get_turn_off_trigger() const;
-  void set_optimistic(bool optimistic);
-  void set_assumed_state(bool assumed_state);
-  void loop() override;
+  void loop() override {
+    if (!this->f_.has_value())
+      return;
+    auto s = (*this->f_)();
+    if (!s.has_value())
+      return;
+    this->publish_state(*s);
+  }
 
-  float get_setup_priority() const override;
+  Trigger<> *get_turn_on_trigger() const { return this->turn_on_trigger_; }
+  Trigger<> *get_turn_off_trigger() const { return this->turn_off_trigger_; }
+  void set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
+  void set_assumed_state(bool assumed_state) { this->assumed_state_ = assumed_state; }
+
+  float get_setup_priority() const override { return setup_priority::HARDWARE - 2.0f; }
 
  protected:
-  bool assumed_state() override;
+  bool assumed_state() override { return this->assumed_state_; }
 
   void write_state(bool state) override;
 
-  optional<std::function<optional<bool>()>> f_;
+  optional<F> f_;
   bool optimistic_{false};
   bool assumed_state_{false};
   Trigger<> *turn_on_trigger_;
@@ -36,5 +43,20 @@ class TemplateSwitch : public switch_::Switch, public Component {
   Trigger<> *prev_trigger_{nullptr};
 };
 
+class TemplateSwitch : public TemplateSwitchBase<std::function<optional<bool>()>> {
+ public:
+  void set_state_lambda(std::function<optional<bool>()> &&f) { this->f_ = f; }
+};
+
+/** Optimized template switch 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 StatelessTemplateSwitch : public TemplateSwitchBase<optional<bool> (*)()> {
+ public:
+  explicit StatelessTemplateSwitch(optional<bool> (*f)()) { this->f_ = f; }
+};
+
 }  // namespace template_
 }  // namespace esphome

esphome/components/template/text/__init__.py

@@ -3,6 +3,7 @@ import esphome.codegen as cg
 from esphome.components import text
 import esphome.config_validation as cv
 from esphome.const import (
+    CONF_ID,
     CONF_INITIAL_VALUE,
     CONF_LAMBDA,
     CONF_MAX_LENGTH,
@@ -16,6 +17,9 @@ from esphome.const import (
 from .. import template_ns
 
 TemplateText = template_ns.class_("TemplateText", text.Text, cg.PollingComponent)
+StatelessTemplateText = template_ns.class_(
+    "StatelessTemplateText", text.Text, cg.PollingComponent
+)
 
 TextSaverBase = template_ns.class_("TemplateTextSaverBase")
 TextSaverTemplate = template_ns.class_("TextSaver", TextSaverBase)
@@ -65,21 +69,31 @@ CONFIG_SCHEMA = cv.All(
 
 
 async def to_code(config):
-    var = await text.new_text(
-        config,
-        min_length=config[CONF_MIN_LENGTH],
-        max_length=config[CONF_MAX_LENGTH],
-        pattern=config.get(CONF_PATTERN),
-    )
-    await cg.register_component(var, config)
-
     if CONF_LAMBDA in config:
+        # Use new_lambda_pvariable to create either TemplateText or StatelessTemplateText
         template_ = await cg.process_lambda(
             config[CONF_LAMBDA], [], return_type=cg.optional.template(cg.std_string)
         )
-        cg.add(var.set_template(template_))
-
+        var = automation.new_lambda_pvariable(
+            config[CONF_ID], template_, StatelessTemplateText
+        )
+        await cg.register_component(var, config)
+        await text.register_text(
+            var,
+            config,
+            min_length=config[CONF_MIN_LENGTH],
+            max_length=config[CONF_MAX_LENGTH],
+            pattern=config.get(CONF_PATTERN),
+        )
     else:
+        # No lambda - just create the base template text
+        var = await text.new_text(
+            config,
+            min_length=config[CONF_MIN_LENGTH],
+            max_length=config[CONF_MAX_LENGTH],
+            pattern=config.get(CONF_PATTERN),
+        )
+        await cg.register_component(var, config)
         cg.add(var.set_optimistic(config[CONF_OPTIMISTIC]))
         if initial_value_config := config.get(CONF_INITIAL_VALUE):
             cg.add(var.set_initial_value(initial_value_config))

esphome/components/template/text/template_text.cpp

@@ -6,7 +6,8 @@ namespace template_ {
 
 static const char *const TAG = "template.text";
 
-void TemplateText::setup() {
+// Template instantiations
+template<typename F> void TemplateTextBase<F>::setup() {
   if (!(this->f_ == nullptr)) {
     if (this->f_.has_value())
       return;
@@ -25,21 +26,7 @@ void TemplateText::setup() {
     this->publish_state(value);
 }
 
-void TemplateText::update() {
-  if (this->f_ == nullptr)
-    return;
-
-  if (!this->f_.has_value())
-    return;
-
-  auto val = (*this->f_)();
-  if (!val.has_value())
-    return;
-
-  this->publish_state(*val);
-}
-
-void TemplateText::control(const std::string &value) {
+template<typename F> void TemplateTextBase<F>::control(const std::string &value) {
   this->set_trigger_->trigger(value);
 
   if (this->optimistic_)
@@ -51,11 +38,15 @@ void TemplateText::control(const std::string &value) {
     }
   }
 }
-void TemplateText::dump_config() {
+
+template<typename F> void TemplateTextBase<F>::dump_config() {
   LOG_TEXT("", "Template Text Input", this);
   ESP_LOGCONFIG(TAG, "  Optimistic: %s", YESNO(this->optimistic_));
   LOG_UPDATE_INTERVAL(this);
 }
 
+template class TemplateTextBase<std::function<optional<std::string>()>>;
+template class TemplateTextBase<optional<std::string> (*)()>;
+
 }  // namespace template_
 }  // namespace esphome

esphome/components/template/text/template_text.h

@@ -59,13 +59,24 @@ template<uint8_t SZ> class TextSaver : public TemplateTextSaverBase {
   }
 };
 
-class TemplateText : public text::Text, public PollingComponent {
+template<typename F> class TemplateTextBase : public text::Text, public PollingComponent {
  public:
-  void set_template(std::function<optional<std::string>()> &&f) { this->f_ = f; }
+  TemplateTextBase() : set_trigger_(new Trigger<std::string>()) {}
 
   void setup() override;
-  void update() override;
   void dump_config() override;
+
+  void update() override {
+    if (this->f_ == nullptr)
+      return;
+    if (!this->f_.has_value())
+      return;
+    auto val = (*this->f_)();
+    if (!val.has_value())
+      return;
+    this->publish_state(*val);
+  }
+
   float get_setup_priority() const override { return setup_priority::HARDWARE; }
 
   Trigger<std::string> *get_set_trigger() const { return this->set_trigger_; }
@@ -77,11 +88,26 @@ class TemplateText : public text::Text, public PollingComponent {
   void control(const std::string &value) override;
   bool optimistic_ = false;
   std::string initial_value_;
-  Trigger<std::string> *set_trigger_ = new Trigger<std::string>();
-  optional<std::function<optional<std::string>()>> f_{nullptr};
+  Trigger<std::string> *set_trigger_;
+  optional<F> f_{nullptr};
 
   TemplateTextSaverBase *pref_ = nullptr;
 };
 
+class TemplateText : public TemplateTextBase<std::function<optional<std::string>()>> {
+ public:
+  void set_template(std::function<optional<std::string>()> &&f) { this->f_ = f; }
+};
+
+/** Optimized template text 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 StatelessTemplateText : public TemplateTextBase<optional<std::string> (*)()> {
+ public:
+  explicit StatelessTemplateText(optional<std::string> (*f)()) { this->f_ = f; }
+};
+
 }  // namespace template_
 }  // namespace esphome

esphome/components/template/text_sensor/__init__.py

@@ -10,6 +10,9 @@ from .. import template_ns
 TemplateTextSensor = template_ns.class_(
     "TemplateTextSensor", text_sensor.TextSensor, cg.PollingComponent
 )
+StatelessTemplateTextSensor = template_ns.class_(
+    "StatelessTemplateTextSensor", text_sensor.TextSensor, cg.PollingComponent
+)
 
 CONFIG_SCHEMA = (
     text_sensor.text_sensor_schema()
@@ -24,14 +27,21 @@ CONFIG_SCHEMA = (
 
 
 async def to_code(config):
-    var = await text_sensor.new_text_sensor(config)
-    await cg.register_component(var, config)
-
     if CONF_LAMBDA in config:
+        # Use new_lambda_pvariable to create either TemplateTextSensor or StatelessTemplateTextSensor
         template_ = await cg.process_lambda(
             config[CONF_LAMBDA], [], return_type=cg.optional.template(cg.std_string)
         )
-        cg.add(var.set_template(template_))
+        var = automation.new_lambda_pvariable(
+            config[CONF_ID], template_, StatelessTemplateTextSensor
+        )
+        # Manually register as text sensor since we didn't use new_text_sensor
+        await text_sensor.register_text_sensor(var, config)
+        await cg.register_component(var, config)
+    else:
+        # No lambda - just create the base template text sensor
+        var = await text_sensor.new_text_sensor(config)
+        await cg.register_component(var, config)
 
 
 @automation.register_action(

esphome/components/template/text_sensor/template_text_sensor.cpp

@@ -6,18 +6,11 @@ namespace template_ {
 
 static const char *const TAG = "template.text_sensor";
 
-void TemplateTextSensor::update() {
-  if (!this->f_.has_value())
-    return;
+// Template instantiations
+template<typename F> void TemplateTextSensorBase<F>::dump_config() { LOG_TEXT_SENSOR("", "Template Sensor", this); }
 
-  auto val = (*this->f_)();
-  if (val.has_value()) {
-    this->publish_state(*val);
-  }
-}
-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::dump_config() { LOG_TEXT_SENSOR("", "Template Sensor", this); }
+template class TemplateTextSensorBase<std::function<optional<std::string>()>>;
+template class TemplateTextSensorBase<optional<std::string> (*)()>;
 
 }  // namespace template_
 }  // namespace esphome

esphome/components/template/text_sensor/template_text_sensor.h

@@ -7,18 +7,38 @@
 namespace esphome {
 namespace template_ {
 
-class TemplateTextSensor : public text_sensor::TextSensor, public PollingComponent {
+template<typename F> class TemplateTextSensorBase : public text_sensor::TextSensor, public PollingComponent {
  public:
-  void set_template(std::function<optional<std::string>()> &&f);
+  void update() override {
+    if (!this->f_.has_value())
+      return;
+    auto val = (*this->f_)();
+    if (val.has_value()) {
+      this->publish_state(*val);
+    }
+  }
 
-  void update() override;
-
-  float get_setup_priority() const override;
+  float get_setup_priority() const override { return setup_priority::HARDWARE; }
 
   void dump_config() override;
 
  protected:
-  optional<std::function<optional<std::string>()>> f_{};
+  optional<F> f_;
+};
+
+class TemplateTextSensor : public TemplateTextSensorBase<std::function<optional<std::string>()>> {
+ public:
+  void set_template(std::function<optional<std::string>()> &&f) { this->f_ = f; }
+};
+
+/** Optimized template text sensor 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 StatelessTemplateTextSensor : public TemplateTextSensorBase<optional<std::string> (*)()> {
+ public:
+  explicit StatelessTemplateTextSensor(optional<std::string> (*f)()) { this->f_ = f; }
 };
 
 }  // namespace template_

esphome/components/template/valve/__init__.py

@@ -20,6 +20,9 @@ from esphome.const import (
 from .. import template_ns
 
 TemplateValve = template_ns.class_("TemplateValve", valve.Valve, cg.Component)
+StatelessTemplateValve = template_ns.class_(
+    "StatelessTemplateValve", valve.Valve, cg.Component
+)
 
 TemplateValvePublishAction = template_ns.class_(
     "TemplateValvePublishAction", automation.Action, cg.Parented.template(TemplateValve)
@@ -62,13 +65,22 @@ CONFIG_SCHEMA = (
 
 
 async def to_code(config):
-    var = await valve.new_valve(config)
-    await cg.register_component(var, config)
     if lambda_config := config.get(CONF_LAMBDA):
+        # Use new_lambda_pvariable to create either TemplateValve or StatelessTemplateValve
         template_ = await cg.process_lambda(
             lambda_config, [], return_type=cg.optional.template(float)
         )
-        cg.add(var.set_state_lambda(template_))
+        var = automation.new_lambda_pvariable(
+            config[CONF_ID], template_, StatelessTemplateValve
+        )
+        # Manually register as valve since we didn't use new_valve
+        await valve.register_valve(var, config)
+        await cg.register_component(var, config)
+    else:
+        # No lambda - just create the base template valve
+        var = await valve.new_valve(config)
+        await cg.register_component(var, config)
+
     if open_action_config := config.get(CONF_OPEN_ACTION):
         await automation.build_automation(
             var.get_open_trigger(), [], open_action_config

esphome/components/template/valve/template_valve.cpp

@@ -8,14 +8,8 @@ using namespace esphome::valve;
 
 static const char *const TAG = "template.valve";
 
-TemplateValve::TemplateValve()
-    : open_trigger_(new Trigger<>()),
-      close_trigger_(new Trigger<>),
-      stop_trigger_(new Trigger<>()),
-      toggle_trigger_(new Trigger<>()),
-      position_trigger_(new Trigger<float>()) {}
-
-void TemplateValve::setup() {
+// Template instantiations
+template<typename F> void TemplateValveBase<F>::setup() {
   switch (this->restore_mode_) {
     case VALVE_NO_RESTORE:
       break;
@@ -35,35 +29,7 @@ void TemplateValve::setup() {
   }
 }
 
-void TemplateValve::loop() {
-  bool changed = false;
-
-  if (this->state_f_.has_value()) {
-    auto s = (*this->state_f_)();
-    if (s.has_value()) {
-      auto pos = clamp(*s, 0.0f, 1.0f);
-      if (pos != this->position) {
-        this->position = pos;
-        changed = true;
-      }
-    }
-  }
-
-  if (changed)
-    this->publish_state();
-}
-
-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; }
-float TemplateValve::get_setup_priority() const { return setup_priority::HARDWARE; }
-
-Trigger<> *TemplateValve::get_open_trigger() const { return this->open_trigger_; }
-Trigger<> *TemplateValve::get_close_trigger() const { return this->close_trigger_; }
-Trigger<> *TemplateValve::get_stop_trigger() const { return this->stop_trigger_; }
-Trigger<> *TemplateValve::get_toggle_trigger() const { return this->toggle_trigger_; }
-
-void TemplateValve::dump_config() {
+template<typename F> void TemplateValveBase<F>::dump_config() {
   LOG_VALVE("", "Template Valve", this);
   ESP_LOGCONFIG(TAG,
                 "  Has position: %s\n"
@@ -71,7 +37,7 @@ void TemplateValve::dump_config() {
                 YESNO(this->has_position_), YESNO(this->optimistic_));
 }
 
-void TemplateValve::control(const ValveCall &call) {
+template<typename F> void TemplateValveBase<F>::control(const ValveCall &call) {
   if (call.get_stop()) {
     this->stop_prev_trigger_();
     this->stop_trigger_->trigger();
@@ -106,7 +72,7 @@ void TemplateValve::control(const ValveCall &call) {
   this->publish_state();
 }
 
-ValveTraits TemplateValve::get_traits() {
+template<typename F> valve::ValveTraits TemplateValveBase<F>::get_traits() {
   auto traits = ValveTraits();
   traits.set_is_assumed_state(this->assumed_state_);
   traits.set_supports_stop(this->has_stop_);
@@ -115,18 +81,15 @@ ValveTraits TemplateValve::get_traits() {
   return traits;
 }
 
-Trigger<float> *TemplateValve::get_position_trigger() const { return this->position_trigger_; }
-
-void TemplateValve::set_has_stop(bool has_stop) { this->has_stop_ = has_stop; }
-void TemplateValve::set_has_toggle(bool has_toggle) { this->has_toggle_ = has_toggle; }
-void TemplateValve::set_has_position(bool has_position) { this->has_position_ = has_position; }
-
-void TemplateValve::stop_prev_trigger_() {
+template<typename F> void TemplateValveBase<F>::stop_prev_trigger_() {
   if (this->prev_command_trigger_ != nullptr) {
     this->prev_command_trigger_->stop_action();
     this->prev_command_trigger_ = nullptr;
   }
 }
 
+template class TemplateValveBase<std::function<optional<float>()>>;
+template class TemplateValveBase<optional<float> (*)()>;
+
 }  // namespace template_
 }  // namespace esphome

esphome/components/template/valve/template_valve.h

@@ -13,28 +13,48 @@ enum TemplateValveRestoreMode {
   VALVE_RESTORE_AND_CALL,
 };
 
-class TemplateValve : public valve::Valve, public Component {
+template<typename F> class TemplateValveBase : public valve::Valve, public Component {
  public:
-  TemplateValve();
+  TemplateValveBase()
+      : open_trigger_(new Trigger<>()),
+        close_trigger_(new Trigger<>()),
+        stop_trigger_(new Trigger<>()),
+        toggle_trigger_(new Trigger<>()),
+        position_trigger_(new Trigger<float>()) {}
 
-  void set_state_lambda(std::function<optional<float>()> &&f);
-  Trigger<> *get_open_trigger() const;
-  Trigger<> *get_close_trigger() const;
-  Trigger<> *get_stop_trigger() const;
-  Trigger<> *get_toggle_trigger() const;
-  Trigger<float> *get_position_trigger() const;
-  void set_optimistic(bool optimistic);
-  void set_assumed_state(bool assumed_state);
-  void set_has_stop(bool has_stop);
-  void set_has_position(bool has_position);
-  void set_has_toggle(bool has_toggle);
-  void set_restore_mode(TemplateValveRestoreMode restore_mode) { restore_mode_ = restore_mode; }
+  void loop() override {
+    bool changed = false;
+
+    if (this->state_f_.has_value()) {
+      auto s = (*this->state_f_)();
+      if (s.has_value()) {
+        auto pos = clamp(*s, 0.0f, 1.0f);
+        if (pos != this->position) {
+          this->position = pos;
+          changed = true;
+        }
+      }
+    }
+
+    if (changed)
+      this->publish_state();
+  }
 
   void setup() override;
-  void loop() override;
   void dump_config() override;
+  float get_setup_priority() const override { return setup_priority::HARDWARE; }
 
-  float get_setup_priority() const override;
+  Trigger<> *get_open_trigger() const { return this->open_trigger_; }
+  Trigger<> *get_close_trigger() const { return this->close_trigger_; }
+  Trigger<> *get_stop_trigger() const { return this->stop_trigger_; }
+  Trigger<> *get_toggle_trigger() const { return this->toggle_trigger_; }
+  Trigger<float> *get_position_trigger() const { return this->position_trigger_; }
+  void set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
+  void set_assumed_state(bool assumed_state) { this->assumed_state_ = assumed_state; }
+  void set_has_stop(bool has_stop) { this->has_stop_ = has_stop; }
+  void set_has_position(bool has_position) { this->has_position_ = has_position; }
+  void set_has_toggle(bool has_toggle) { this->has_toggle_ = has_toggle; }
+  void set_restore_mode(TemplateValveRestoreMode restore_mode) { restore_mode_ = restore_mode; }
 
  protected:
   void control(const valve::ValveCall &call) override;
@@ -42,7 +62,7 @@ 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<F> state_f_;
   bool assumed_state_{false};
   bool optimistic_{false};
   Trigger<> *open_trigger_;
@@ -56,5 +76,20 @@ class TemplateValve : public valve::Valve, public Component {
   bool has_position_{false};
 };
 
+class TemplateValve : public TemplateValveBase<std::function<optional<float>()>> {
+ public:
+  void set_state_lambda(std::function<optional<float>()> &&f) { this->state_f_ = f; }
+};
+
+/** Optimized template valve for stateless lambdas (no capture).
+ *
+ * Uses function pointers instead of std::function to reduce memory overhead.
+ * Memory: 4 bytes (function pointer on 32-bit) vs 32 bytes (std::function) per lambda.
+ */
+class StatelessTemplateValve : public TemplateValveBase<optional<float> (*)()> {
+ public:
+  explicit StatelessTemplateValve(optional<float> (*f)()) { this->state_f_ = f; }
+};
+
 }  // namespace template_
 }  // namespace esphome

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/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

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(