From 51e080c2d33e762ee13f417180a8039ceeee0ee5 Mon Sep 17 00:00:00 2001
From: Javier Peletier <jpeletier@users.noreply.github.com>
Date: Mon, 27 Oct 2025 20:46:26 +0100
Subject: [PATCH 01/13] [substitutions] fix #11077 Preserve ESPHomeDatabase
 (document metadata) in substitutions (#11087)

Co-authored-by: J. Nick Koston <nick+github@koston.org>
Co-authored-by: J. Nick Koston <nick@home-assistant.io>
Co-authored-by: J. Nick Koston <nick@koston.org>
---
 esphome/components/substitutions/__init__.py | 58 +++++++++++++--
 esphome/components/substitutions/jinja.py    | 78 ++++++++++++++++----
 tests/unit_tests/test_substitutions.py       | 27 +++++++
 3 files changed, 140 insertions(+), 23 deletions(-)

diff --git a/esphome/components/substitutions/__init__.py b/esphome/components/substitutions/__init__.py
index 098d56bfad..7e15f714f7 100644
--- a/esphome/components/substitutions/__init__.py
+++ b/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
 
diff --git a/esphome/components/substitutions/jinja.py b/esphome/components/substitutions/jinja.py
index dde0162993..cb3c6dfac5 100644
--- a/esphome/components/substitutions/jinja.py
+++ b/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):
-        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):
+    def expand(self, content_str: str | JinjaStr) -> Any:
         """
         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
diff --git a/tests/unit_tests/test_substitutions.py b/tests/unit_tests/test_substitutions.py
index beb1ebc73e..7d50b44506 100644
--- a/tests/unit_tests/test_substitutions.py
+++ b/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():

From 00f22e5c3644f8c645d5741615271b78423ee453 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Mon, 27 Oct 2025 14:51:08 -0500
Subject: [PATCH 02/13] [network] Eliminate runtime string parsing for IP
 address initialization (#11561)

---
 esphome/components/ethernet/__init__.py | 12 ++++----
 esphome/components/network/__init__.py  | 37 +++++++++++++++++++++++++
 esphome/components/wifi/__init__.py     |  6 ++--
 3 files changed, 45 insertions(+), 10 deletions(-)

diff --git a/esphome/components/ethernet/__init__.py b/esphome/components/ethernet/__init__.py
index 77f70a3630..2f02d227d7 100644
--- a/esphome/components/ethernet/__init__.py
+++ b/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]))),
-        ("gateway", IPAddress(str(config[CONF_GATEWAY]))),
-        ("subnet", IPAddress(str(config[CONF_SUBNET]))),
-        ("dns1", IPAddress(str(config[CONF_DNS1]))),
-        ("dns2", IPAddress(str(config[CONF_DNS2]))),
+        ("static_ip", ip_address_literal(config[CONF_STATIC_IP])),
+        ("gateway", ip_address_literal(config[CONF_GATEWAY])),
+        ("subnet", ip_address_literal(config[CONF_SUBNET])),
+        ("dns1", ip_address_literal(config[CONF_DNS1])),
+        ("dns2", ip_address_literal(config[CONF_DNS2])),
     )
 
 
diff --git a/esphome/components/network/__init__.py b/esphome/components/network/__init__.py
index 1a74350c4c..502803da1e 100644
--- a/esphome/components/network/__init__.py
+++ b/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(
diff --git a/esphome/components/wifi/__init__.py b/esphome/components/wifi/__init__.py
index ba488728b7..b980bab4aa 100644
--- a/esphome/components/wifi/__init__.py
+++ b/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 IPAddress(0, 0, 0, 0)
-    return IPAddress(str(ip))
+    return ip_address_literal(ip)
 
 
 def manual_ip(config):

From e26b5874d76332aa35125e3be434a9d7ab525d3a Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Mon, 27 Oct 2025 15:07:31 -0500
Subject: [PATCH 03/13] [api] Register user services with initializer_list
 (#11545)

---
 esphome/components/api/__init__.py         | 10 +++++++++-
 esphome/components/api/api_server.h        |  6 ++++++
 esphome/components/api/custom_api_device.h | 12 ++++++++++++
 esphome/core/defines.h                     |  1 +
 4 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/esphome/components/api/__init__.py b/esphome/components/api/__init__.py
index e91e922204..363f5b73e1 100644
--- a/esphome/components/api/__init__.py
+++ b/esphome/components/api/__init__.py
@@ -258,6 +258,10 @@ 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 +269,8 @@ 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 +284,10 @@ 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")
diff --git a/esphome/components/api/api_server.h b/esphome/components/api/api_server.h
index e0e23301d0..d29181250e 100644
--- a/esphome/components/api/api_server.h
+++ b/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
diff --git a/esphome/components/api/custom_api_device.h b/esphome/components/api/custom_api_device.h
index 711eba2444..d34ccfa0ce 100644
--- a/esphome/components/api/custom_api_device.h
+++ b/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) {
diff --git a/esphome/core/defines.h b/esphome/core/defines.h
index 8095ffed4a..97e766455a 100644
--- a/esphome/core/defines.h
+++ b/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

From 14b057f54e5f552de9ef1450cea509616bb1b230 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Mon, 27 Oct 2025 15:14:16 -0500
Subject: [PATCH 04/13] [light] Optimize LambdaLightEffect and
 AddressableLambdaLightEffect with function pointers (#11556)

---
 esphome/components/light/addressable_light_effect.h | 6 +++---
 esphome/components/light/base_light_effects.h       | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/esphome/components/light/addressable_light_effect.h b/esphome/components/light/addressable_light_effect.h
index 9840112040..0847db3770 100644
--- a/esphome/components/light/addressable_light_effect.h
+++ b/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_;
diff --git a/esphome/components/light/base_light_effects.h b/esphome/components/light/base_light_effects.h
index 327c243525..515afc5c59 100644
--- a/esphome/components/light/base_light_effects.h
+++ b/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)
-      : LightEffect(name), f_(std::move(f)), update_interval_(update_interval) {}
+  LambdaLightEffect(const char *name, void (*f)(bool initial_run), uint32_t 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_;

From bda4769bd3df0ac81eae0c4dcdcc5dc49e960eb7 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Mon, 27 Oct 2025 16:05:40 -0500
Subject: [PATCH 05/13] [core] Optimize TemplatableValue to use function
 pointers for stateless lambdas (#11554)

---
 esphome/core/automation.h | 36 ++++++++++++++++++++++++++++++------
 1 file changed, 30 insertions(+), 6 deletions(-)

diff --git a/esphome/core/automation.h b/esphome/core/automation.h
index 0512752d50..aace7889f0 100644
--- a/esphome/core/automation.h
+++ b/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) {
-      return (*this->f_)(x...);
+    switch (this->type_) {
+      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...);
   };
 };
 

From f44615cc8daac4ee1b9e7830c2adf8cca91f1667 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Mon, 27 Oct 2025 17:00:02 -0500
Subject: [PATCH 06/13] [template] Optimize all template platforms to use
 function pointers for stateless lambdas (#11555)

---
 esphome/components/template/binary_sensor/__init__.py     | 8 +++++++-
 .../template/binary_sensor/template_binary_sensor.cpp     | 4 ++--
 .../template/binary_sensor/template_binary_sensor.h       | 4 ++--
 esphome/components/template/cover/template_cover.cpp      | 4 ++--
 esphome/components/template/cover/template_cover.h        | 8 ++++----
 esphome/components/template/datetime/template_date.h      | 4 ++--
 esphome/components/template/datetime/template_datetime.h  | 4 ++--
 esphome/components/template/datetime/template_time.h      | 4 ++--
 esphome/components/template/lock/template_lock.cpp        | 2 +-
 esphome/components/template/lock/template_lock.h          | 4 ++--
 esphome/components/template/number/template_number.h      | 4 ++--
 esphome/components/template/select/template_select.h      | 4 ++--
 esphome/components/template/sensor/template_sensor.cpp    | 2 +-
 esphome/components/template/sensor/template_sensor.h      | 4 ++--
 esphome/components/template/switch/template_switch.cpp    | 2 +-
 esphome/components/template/switch/template_switch.h      | 4 ++--
 esphome/components/template/text/template_text.h          | 4 ++--
 .../template/text_sensor/template_text_sensor.cpp         | 2 +-
 .../template/text_sensor/template_text_sensor.h           | 4 ++--
 esphome/components/template/valve/template_valve.cpp      | 2 +-
 esphome/components/template/valve/template_valve.h        | 4 ++--
 21 files changed, 44 insertions(+), 38 deletions(-)

diff --git a/esphome/components/template/binary_sensor/__init__.py b/esphome/components/template/binary_sensor/__init__.py
index c93876380d..9d4208dcca 100644
--- a/esphome/components/template/binary_sensor/__init__.py
+++ b/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_))
 
diff --git a/esphome/components/template/binary_sensor/template_binary_sensor.cpp b/esphome/components/template/binary_sensor/template_binary_sensor.cpp
index d1fb618695..8543dff4dc 100644
--- a/esphome/components/template/binary_sensor/template_binary_sensor.cpp
+++ b/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);
   }
diff --git a/esphome/components/template/binary_sensor/template_binary_sensor.h b/esphome/components/template/binary_sensor/template_binary_sensor.h
index 5e5624d82e..2e0b216eb4 100644
--- a/esphome/components/template/binary_sensor/template_binary_sensor.h
+++ b/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_
diff --git a/esphome/components/template/cover/template_cover.cpp b/esphome/components/template/cover/template_cover.cpp
index 84c687536e..bed3931e78 100644
--- a/esphome/components/template/cover/template_cover.cpp
+++ b/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; }
diff --git a/esphome/components/template/cover/template_cover.h b/esphome/components/template/cover/template_cover.h
index 958c94b0a6..ed1ebf4e43 100644
--- a/esphome/components/template/cover/template_cover.h
+++ b/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<std::function<optional<float>()>> tilt_f_;
+  optional<optional<float> (*)()> state_f_;
+  optional<optional<float> (*)()> tilt_f_;
   bool assumed_state_{false};
   bool optimistic_{false};
   Trigger<> *open_trigger_;
diff --git a/esphome/components/template/datetime/template_date.h b/esphome/components/template/datetime/template_date.h
index 185c7ed49d..2a0967fc94 100644
--- a/esphome/components/template/datetime/template_date.h
+++ b/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_;
 };
diff --git a/esphome/components/template/datetime/template_datetime.h b/esphome/components/template/datetime/template_datetime.h
index ef80ded89a..d917015b67 100644
--- a/esphome/components/template/datetime/template_datetime.h
+++ b/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_;
 };
diff --git a/esphome/components/template/datetime/template_time.h b/esphome/components/template/datetime/template_time.h
index 4a7c0098ec..2f05ba0737 100644
--- a/esphome/components/template/datetime/template_time.h
+++ b/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_;
 };
diff --git a/esphome/components/template/lock/template_lock.cpp b/esphome/components/template/lock/template_lock.cpp
index 87ba1046eb..c2e227c26d 100644
--- a/esphome/components/template/lock/template_lock.cpp
+++ b/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_; }
diff --git a/esphome/components/template/lock/template_lock.h b/esphome/components/template/lock/template_lock.h
index 4f798eca81..428744a66f 100644
--- a/esphome/components/template/lock/template_lock.h
+++ b/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_;
diff --git a/esphome/components/template/number/template_number.h b/esphome/components/template/number/template_number.h
index 9a82e44339..e77b181d25 100644
--- a/esphome/components/template/number/template_number.h
+++ b/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_;
 };
diff --git a/esphome/components/template/select/template_select.h b/esphome/components/template/select/template_select.h
index 2f00765c3d..c1b348b26a 100644
--- a/esphome/components/template/select/template_select.h
+++ b/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_;
 };
diff --git a/esphome/components/template/sensor/template_sensor.cpp b/esphome/components/template/sensor/template_sensor.cpp
index f2d0e7363e..65f2417670 100644
--- a/esphome/components/template/sensor/template_sensor.cpp
+++ b/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);
diff --git a/esphome/components/template/sensor/template_sensor.h b/esphome/components/template/sensor/template_sensor.h
index 2630cb0b14..369313d607 100644
--- a/esphome/components/template/sensor/template_sensor.h
+++ b/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_
diff --git a/esphome/components/template/switch/template_switch.cpp b/esphome/components/template/switch/template_switch.cpp
index fa236f6364..5aaf514b2a 100644
--- a/esphome/components/template/switch/template_switch.cpp
+++ b/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_; }
diff --git a/esphome/components/template/switch/template_switch.h b/esphome/components/template/switch/template_switch.h
index bfe9ac25d6..0fba66b9bd 100644
--- a/esphome/components/template/switch/template_switch.h
+++ b/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_;
diff --git a/esphome/components/template/text/template_text.h b/esphome/components/template/text/template_text.h
index bcfc54a2ba..6c17d2016a 100644
--- a/esphome/components/template/text/template_text.h
+++ b/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;
 };
diff --git a/esphome/components/template/text_sensor/template_text_sensor.cpp b/esphome/components/template/text_sensor/template_text_sensor.cpp
index 885ad47bbf..2b0297d62f 100644
--- a/esphome/components/template/text_sensor/template_text_sensor.cpp
+++ b/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_
diff --git a/esphome/components/template/text_sensor/template_text_sensor.h b/esphome/components/template/text_sensor/template_text_sensor.h
index 07a2bd96fc..48e40c2493 100644
--- a/esphome/components/template/text_sensor/template_text_sensor.h
+++ b/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_
diff --git a/esphome/components/template/valve/template_valve.cpp b/esphome/components/template/valve/template_valve.cpp
index 5fa14a2de7..b27cc00968 100644
--- a/esphome/components/template/valve/template_valve.cpp
+++ b/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_; }
diff --git a/esphome/components/template/valve/template_valve.h b/esphome/components/template/valve/template_valve.h
index 5e3fb6aff3..92c32f3487 100644
--- a/esphome/components/template/valve/template_valve.h
+++ b/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_;

From dfa69173ead5457f23aa6daf49bf85aa3dd59e59 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Mon, 27 Oct 2025 17:03:44 -0500
Subject: [PATCH 07/13] [api] Use FixedVector const references for service
 array arguments (#11546)

---
 esphome/codegen.py                       |  1 +
 esphome/components/api/__init__.py       | 10 +++--
 esphome/components/api/user_services.cpp | 57 ++++++++++++++++++++++--
 esphome/cpp_types.py                     |  1 +
 4 files changed, 61 insertions(+), 8 deletions(-)

diff --git a/esphome/codegen.py b/esphome/codegen.py
index 6decd77c62..6d55c6023d 100644
--- a/esphome/codegen.py
+++ b/esphome/codegen.py
@@ -62,6 +62,7 @@ from esphome.cpp_types import (  # noqa: F401
     EntityBase,
     EntityCategory,
     ESPTime,
+    FixedVector,
     GPIOPin,
     InternalGPIOPin,
     JsonObject,
diff --git a/esphome/components/api/__init__.py b/esphome/components/api/__init__.py
index 363f5b73e1..449572c0e5 100644
--- a/esphome/components/api/__init__.py
+++ b/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),
-    "int[]": cg.std_vector.template(cg.int32),
-    "float[]": cg.std_vector.template(float),
-    "string[]": cg.std_vector.template(cg.std_string),
+    "bool[]": cg.FixedVector.template(bool).operator("const").operator("ref"),
+    "int[]": cg.FixedVector.template(cg.int32).operator("const").operator("ref"),
+    "float[]": cg.FixedVector.template(float).operator("const").operator("ref"),
+    "string[]": cg.FixedVector.template(cg.std_string)
+    .operator("const")
+    .operator("ref"),
 }
 CONF_ENCRYPTION = "encryption"
 CONF_BATCH_DELAY = "batch_delay"
diff --git a/esphome/components/api/user_services.cpp b/esphome/components/api/user_services.cpp
index 3cbf2ab5f9..9c2b4aa79a 100644
--- a/esphome/components/api/user_services.cpp
+++ b/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
diff --git a/esphome/cpp_types.py b/esphome/cpp_types.py
index a0dd62cb4e..0d1813f63b 100644
--- a/esphome/cpp_types.py
+++ b/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")

From d65ad693381b3f2e61e32093577f3322fd9fa5b8 Mon Sep 17 00:00:00 2001
From: Keith Burzinski <kbx81x@gmail.com>
Date: Mon, 27 Oct 2025 17:09:45 -0500
Subject: [PATCH 08/13] [uart] Fix order of initialization calls (#11510)

---
 .../uart/uart_component_esp_idf.cpp           | 66 ++++++++++---------
 1 file changed, 36 insertions(+), 30 deletions(-)

diff --git a/esphome/components/uart/uart_component_esp_idf.cpp b/esphome/components/uart/uart_component_esp_idf.cpp
index cffa3308eb..73813d2d5b 100644
--- a/esphome/components/uart/uart_component_esp_idf.cpp
+++ b/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 = uart_param_config(this->uart_num_, &uart_config);
+  esp_err_t err;
+
+  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("  RX Pin: ", rx_pin_);
-  LOG_PIN("  Flow Control Pin: ", flow_control_pin_);
+  LOG_PIN("  TX Pin: ", this->tx_pin_);
+  LOG_PIN("  RX Pin: ", this->rx_pin_);
+  LOG_PIN("  Flow Control Pin: ", this->flow_control_pin_);
   if (this->rx_pin_ != nullptr) {
     ESP_LOGCONFIG(TAG,
                   "  RX Buffer Size: %u\n"

From 3377080272ea4b6a201cda35e1d97e504d16b247 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Mon, 27 Oct 2025 17:16:09 -0500
Subject: [PATCH 09/13] [core] Simplify ESPTime::strftime() and save 20 bytes
 flash (#11539)

---
 esphome/core/time.cpp | 22 ++++++++--------------
 esphome/core/time.h   | 12 +++++++-----
 2 files changed, 15 insertions(+), 19 deletions(-)

diff --git a/esphome/core/time.cpp b/esphome/core/time.cpp
index 1285ec6448..d30dac4394 100644
--- a/esphome/core/time.cpp
+++ b/esphome/core/time.cpp
@@ -46,24 +46,18 @@ struct tm ESPTime::to_c_tm() {
   return c_tm;
 }
 
-std::string ESPTime::strftime(const std::string &format) {
-  std::string timestr;
-  timestr.resize(format.size() * 4);
+std::string ESPTime::strftime(const char *format) {
   struct tm c_tm = this->to_c_tm();
-  size_t len = ::strftime(&timestr[0], timestr.size(), format.c_str(), &c_tm);
-  while (len == 0) {
-    if (timestr.size() >= 128) {
-      // strftime has failed for reasons unrelated to the size of the buffer
-      // so return a formatting error
-      return "ERROR";
-    }
-    timestr.resize(timestr.size() * 2);
-    len = ::strftime(&timestr[0], timestr.size(), format.c_str(), &c_tm);
+  char buf[128];
+  size_t len = ::strftime(buf, sizeof(buf), format, &c_tm);
+  if (len > 0) {
+    return std::string(buf, len);
   }
-  timestr.resize(len);
-  return timestr;
+  return "ERROR";
 }
 
+std::string ESPTime::strftime(const std::string &format) { return this->strftime(format.c_str()); }
+
 bool ESPTime::strptime(const std::string &time_to_parse, ESPTime &esp_time) {
   uint16_t year;
   uint8_t month;
diff --git a/esphome/core/time.h b/esphome/core/time.h
index a53fca2346..ffcfced418 100644
--- a/esphome/core/time.h
+++ b/esphome/core/time.h
@@ -44,17 +44,19 @@ struct ESPTime {
   size_t strftime(char *buffer, size_t buffer_len, const char *format);
 
   /** Convert this ESPTime struct to a string as specified by the format argument.
-   * @see https://www.gnu.org/software/libc/manual/html_node/Formatting-Calendar-Time.html#index-strftime
+   * @see https://en.cppreference.com/w/c/chrono/strftime
    *
-   * @warning This method uses dynamically allocated strings which can cause heap fragmentation with some
+   * @warning This method returns a dynamically allocated string which can cause heap fragmentation with some
    * microcontrollers.
    *
-   * @warning This method can return "ERROR" when the underlying strftime() call fails, e.g. when the
-   * format string contains unsupported specifiers or when the format string doesn't produce any
-   * output.
+   * @warning This method can return "ERROR" when the underlying strftime() call fails or when the
+   * output exceeds 128 bytes.
    */
   std::string strftime(const std::string &format);
 
+  /// @copydoc strftime(const std::string &format)
+  std::string strftime(const char *format);
+
   /// Check if this ESPTime is valid (all fields in range and year is greater than 2018)
   bool is_valid() const { return this->year >= 2019 && this->fields_in_range(); }
 

From 31b1b50ad9d6811b1077fdedc6ae2df850c30fa0 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Mon, 27 Oct 2025 17:16:38 -0500
Subject: [PATCH 10/13] [number] Skip set_mode call when using default AUTO
 mode (#11537)

---
 esphome/components/number/__init__.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/esphome/components/number/__init__.py b/esphome/components/number/__init__.py
index 230c3aa0c1..ac0329fcc6 100644
--- a/esphome/components/number/__init__.py
+++ b/esphome/components/number/__init__.py
@@ -252,7 +252,10 @@ async def setup_number_core_(
     cg.add(var.traits.set_max_value(max_value))
     cg.add(var.traits.set_step(step))
 
-    cg.add(var.traits.set_mode(config[CONF_MODE]))
+    # Only set if non-default to avoid bloating setup() function
+    # (mode_ is initialized to NUMBER_MODE_AUTO in the header)
+    if config[CONF_MODE] != NumberMode.NUMBER_MODE_AUTO:
+        cg.add(var.traits.set_mode(config[CONF_MODE]))
 
     for conf in config.get(CONF_ON_VALUE, []):
         trigger = cg.new_Pvariable(conf[CONF_TRIGGER_ID], var)

From dfb4b31bf9ee381f5ebe2261b8aeaf1872edebbf Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Mon, 27 Oct 2025 17:37:40 -0500
Subject: [PATCH 11/13] [template] Store initial option as index in template
 select (#11523)

---
 .../components/template/select/__init__.py    | 15 +++++++---
 .../template/select/template_select.cpp       | 28 ++++++++-----------
 .../template/select/template_select.h         |  4 +--
 .../host_mode_empty_string_options.yaml       | 11 ++++++++
 .../test_host_mode_empty_string_options.py    | 28 +++++++++++++++++--
 5 files changed, 61 insertions(+), 25 deletions(-)

diff --git a/esphome/components/template/select/__init__.py b/esphome/components/template/select/__init__.py
index 3282092d63..0e9c240547 100644
--- a/esphome/components/template/select/__init__.py
+++ b/esphome/components/template/select/__init__.py
@@ -73,11 +73,18 @@ async def to_code(config):
         cg.add(var.set_template(template_))
 
     else:
-        cg.add(var.set_optimistic(config[CONF_OPTIMISTIC]))
-        cg.add(var.set_initial_option(config[CONF_INITIAL_OPTION]))
+        # 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))
 
-        if CONF_RESTORE_VALUE in config:
-            cg.add(var.set_restore_value(config[CONF_RESTORE_VALUE]))
+        # 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(
diff --git a/esphome/components/template/select/template_select.cpp b/esphome/components/template/select/template_select.cpp
index 95b0ee0d2b..3765cf02bf 100644
--- a/esphome/components/template/select/template_select.cpp
+++ b/esphome/components/template/select/template_select.cpp
@@ -10,26 +10,21 @@ void TemplateSelect::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() {
@@ -69,7 +64,8 @@ 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_));
 }
 
 }  // namespace template_
diff --git a/esphome/components/template/select/template_select.h b/esphome/components/template/select/template_select.h
index c1b348b26a..e77e4d8f14 100644
--- a/esphome/components/template/select/template_select.h
+++ b/esphome/components/template/select/template_select.h
@@ -19,13 +19,13 @@ class TemplateSelect : public select::Select, public PollingComponent {
 
   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<optional<std::string> (*)()> f_;
diff --git a/tests/integration/fixtures/host_mode_empty_string_options.yaml b/tests/integration/fixtures/host_mode_empty_string_options.yaml
index ab8e6cd005..a170511c46 100644
--- a/tests/integration/fixtures/host_mode_empty_string_options.yaml
+++ b/tests/integration/fixtures/host_mode_empty_string_options.yaml
@@ -41,6 +41,17 @@ select:
       - ""  # Empty string at the end
     initial_option: "Choice X"
 
+  - platform: template
+    name: "Select Initial Option Test"
+    id: select_initial_option_test
+    optimistic: true
+    options:
+      - "First"
+      - "Second"
+      - "Third"
+      - "Fourth"
+    initial_option: "Third"  # Test non-default initial option
+
 # Add a sensor to ensure we have other entities in the list
 sensor:
   - platform: template
diff --git a/tests/integration/test_host_mode_empty_string_options.py b/tests/integration/test_host_mode_empty_string_options.py
index 242db2d40f..1180ce75fc 100644
--- a/tests/integration/test_host_mode_empty_string_options.py
+++ b/tests/integration/test_host_mode_empty_string_options.py
@@ -36,8 +36,8 @@ async def test_host_mode_empty_string_options(
 
         # Find our select entities
         select_entities = [e for e in entity_info if isinstance(e, SelectInfo)]
-        assert len(select_entities) == 3, (
-            f"Expected 3 select entities, got {len(select_entities)}"
+        assert len(select_entities) == 4, (
+            f"Expected 4 select entities, got {len(select_entities)}"
         )
 
         # Verify each select entity by name and check their options
@@ -71,6 +71,15 @@ async def test_host_mode_empty_string_options(
         assert empty_last.options[2] == "Choice Z"
         assert empty_last.options[3] == ""  # Empty string at end
 
+        # Check "Select Initial Option Test" - verify non-default initial option
+        assert "Select Initial Option Test" in selects_by_name
+        initial_option_test = selects_by_name["Select Initial Option Test"]
+        assert len(initial_option_test.options) == 4
+        assert initial_option_test.options[0] == "First"
+        assert initial_option_test.options[1] == "Second"
+        assert initial_option_test.options[2] == "Third"
+        assert initial_option_test.options[3] == "Fourth"
+
         # If we got here without protobuf decoding errors, the fix is working
         # The bug would have caused "Invalid protobuf message" errors with trailing bytes
 
@@ -78,7 +87,12 @@ async def test_host_mode_empty_string_options(
         # This ensures empty strings work properly in state messages too
         states: dict[int, EntityState] = {}
         states_received_future: asyncio.Future[None] = loop.create_future()
-        expected_select_keys = {empty_first.key, empty_middle.key, empty_last.key}
+        expected_select_keys = {
+            empty_first.key,
+            empty_middle.key,
+            empty_last.key,
+            initial_option_test.key,
+        }
         received_select_keys = set()
 
         def on_state(state: EntityState) -> None:
@@ -109,6 +123,14 @@ async def test_host_mode_empty_string_options(
         assert empty_first.key in states
         assert empty_middle.key in states
         assert empty_last.key in states
+        assert initial_option_test.key in states
+
+        # Verify the initial option is set correctly to "Third" (not the default "First")
+        initial_state = states[initial_option_test.key]
+        assert initial_state.state == "Third", (
+            f"Expected initial state 'Third' but got '{initial_state.state}' - "
+            f"initial_option not correctly applied"
+        )
 
         # The main test is that we got here without protobuf errors
         # The select entities with empty string options were properly encoded

From ce8a6a6c438716add8256daf3d2d3b95d51fbacd Mon Sep 17 00:00:00 2001
From: Daniel Herrmann <daniel.herrmann1@gmail.com>
Date: Tue, 28 Oct 2025 00:24:13 +0100
Subject: [PATCH 12/13] fix: load_cert_chain requires the path, not a file
 object (#11543)

---
 esphome/mqtt.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/esphome/mqtt.py b/esphome/mqtt.py
index f1c631697a..093ee64df4 100644
--- a/esphome/mqtt.py
+++ b/esphome/mqtt.py
@@ -120,7 +120,7 @@ def prepare(
                 cert_file.flush()
                 key_file.write(config[CONF_MQTT].get(CONF_CLIENT_CERTIFICATE_KEY))
                 key_file.flush()
-                context.load_cert_chain(cert_file, key_file)
+                context.load_cert_chain(cert_file.name, key_file.name)
         client.tls_set_context(context)
 
     try:

From bdbe9caf3653cec968170d419c02a862f1ee085b Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Mon, 27 Oct 2025 19:11:32 -0500
Subject: [PATCH 13/13] [modbus_controller] Optimize lambdas to use function
 pointers instead of std::function

---
 .../binary_sensor/modbus_binarysensor.h       |  4 +-
 .../modbus_controller/number/modbus_number.h  |  8 +-
 .../modbus_controller/output/modbus_output.h  |  8 +-
 .../modbus_controller/select/modbus_select.h  | 11 ++-
 .../modbus_controller/sensor/modbus_sensor.h  |  4 +-
 .../modbus_controller/switch/modbus_switch.h  |  8 +-
 .../text_sensor/modbus_textsensor.h           |  5 +-
 .../components/modbus_controller/common.yaml  | 83 +++++++++++++++++++
 8 files changed, 106 insertions(+), 25 deletions(-)

diff --git a/esphome/components/modbus_controller/binary_sensor/modbus_binarysensor.h b/esphome/components/modbus_controller/binary_sensor/modbus_binarysensor.h
index 3a017c6f88..119f4fdd5a 100644
--- a/esphome/components/modbus_controller/binary_sensor/modbus_binarysensor.h
+++ b/esphome/components/modbus_controller/binary_sensor/modbus_binarysensor.h
@@ -33,8 +33,8 @@ class ModbusBinarySensor : public Component, public binary_sensor::BinarySensor,
 
   void dump_config() override;
 
-  using transform_func_t = std::function<optional<bool>(ModbusBinarySensor *, bool, const std::vector<uint8_t> &)>;
-  void set_template(transform_func_t &&f) { this->transform_func_ = f; }
+  using transform_func_t = optional<bool> (*)(ModbusBinarySensor *, bool, const std::vector<uint8_t> &);
+  void set_template(transform_func_t f) { this->transform_func_ = f; }
 
  protected:
   optional<transform_func_t> transform_func_{nullopt};
diff --git a/esphome/components/modbus_controller/number/modbus_number.h b/esphome/components/modbus_controller/number/modbus_number.h
index 8f77b2e014..169f85ff36 100644
--- a/esphome/components/modbus_controller/number/modbus_number.h
+++ b/esphome/components/modbus_controller/number/modbus_number.h
@@ -31,10 +31,10 @@ class ModbusNumber : public number::Number, public Component, public SensorItem
   void set_parent(ModbusController *parent) { this->parent_ = parent; }
   void set_write_multiply(float factor) { this->multiply_by_ = factor; }
 
-  using transform_func_t = std::function<optional<float>(ModbusNumber *, float, const std::vector<uint8_t> &)>;
-  using write_transform_func_t = std::function<optional<float>(ModbusNumber *, float, std::vector<uint16_t> &)>;
-  void set_template(transform_func_t &&f) { this->transform_func_ = f; }
-  void set_write_template(write_transform_func_t &&f) { this->write_transform_func_ = f; }
+  using transform_func_t = optional<float> (*)(ModbusNumber *, float, const std::vector<uint8_t> &);
+  using write_transform_func_t = optional<float> (*)(ModbusNumber *, float, std::vector<uint16_t> &);
+  void set_template(transform_func_t f) { this->transform_func_ = f; }
+  void set_write_template(write_transform_func_t f) { this->write_transform_func_ = f; }
   void set_use_write_mutiple(bool use_write_multiple) { this->use_write_multiple_ = use_write_multiple; }
 
  protected:
diff --git a/esphome/components/modbus_controller/output/modbus_output.h b/esphome/components/modbus_controller/output/modbus_output.h
index bceb97affb..0fb4bb89ea 100644
--- a/esphome/components/modbus_controller/output/modbus_output.h
+++ b/esphome/components/modbus_controller/output/modbus_output.h
@@ -29,8 +29,8 @@ class ModbusFloatOutput : public output::FloatOutput, public Component, public S
   // Do nothing
   void parse_and_publish(const std::vector<uint8_t> &data) override{};
 
-  using write_transform_func_t = std::function<optional<float>(ModbusFloatOutput *, float, std::vector<uint16_t> &)>;
-  void set_write_template(write_transform_func_t &&f) { this->write_transform_func_ = f; }
+  using write_transform_func_t = optional<float> (*)(ModbusFloatOutput *, float, std::vector<uint16_t> &);
+  void set_write_template(write_transform_func_t f) { this->write_transform_func_ = f; }
   void set_use_write_mutiple(bool use_write_multiple) { this->use_write_multiple_ = use_write_multiple; }
 
  protected:
@@ -60,8 +60,8 @@ class ModbusBinaryOutput : public output::BinaryOutput, public Component, public
   // Do nothing
   void parse_and_publish(const std::vector<uint8_t> &data) override{};
 
-  using write_transform_func_t = std::function<optional<bool>(ModbusBinaryOutput *, bool, std::vector<uint8_t> &)>;
-  void set_write_template(write_transform_func_t &&f) { this->write_transform_func_ = f; }
+  using write_transform_func_t = optional<bool> (*)(ModbusBinaryOutput *, bool, std::vector<uint8_t> &);
+  void set_write_template(write_transform_func_t f) { this->write_transform_func_ = f; }
   void set_use_write_mutiple(bool use_write_multiple) { this->use_write_multiple_ = use_write_multiple; }
 
  protected:
diff --git a/esphome/components/modbus_controller/select/modbus_select.h b/esphome/components/modbus_controller/select/modbus_select.h
index 55fb2107dd..e6b98aead2 100644
--- a/esphome/components/modbus_controller/select/modbus_select.h
+++ b/esphome/components/modbus_controller/select/modbus_select.h
@@ -26,16 +26,15 @@ class ModbusSelect : public Component, public select::Select, public SensorItem
     this->mapping_ = std::move(mapping);
   }
 
-  using transform_func_t =
-      std::function<optional<std::string>(ModbusSelect *const, int64_t, const std::vector<uint8_t> &)>;
-  using write_transform_func_t =
-      std::function<optional<int64_t>(ModbusSelect *const, const std::string &, int64_t, std::vector<uint16_t> &)>;
+  using transform_func_t = optional<std::string> (*)(ModbusSelect *const, int64_t, const std::vector<uint8_t> &);
+  using write_transform_func_t = optional<int64_t> (*)(ModbusSelect *const, const std::string &, int64_t,
+                                                       std::vector<uint16_t> &);
 
   void set_parent(ModbusController *const parent) { this->parent_ = parent; }
   void set_use_write_mutiple(bool use_write_multiple) { this->use_write_multiple_ = use_write_multiple; }
   void set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
-  void set_template(transform_func_t &&f) { this->transform_func_ = f; }
-  void set_write_template(write_transform_func_t &&f) { this->write_transform_func_ = f; }
+  void set_template(transform_func_t f) { this->transform_func_ = f; }
+  void set_write_template(write_transform_func_t f) { this->write_transform_func_ = f; }
 
   void dump_config() override;
   void parse_and_publish(const std::vector<uint8_t> &data) override;
diff --git a/esphome/components/modbus_controller/sensor/modbus_sensor.h b/esphome/components/modbus_controller/sensor/modbus_sensor.h
index 65eb487c1c..ba943c873c 100644
--- a/esphome/components/modbus_controller/sensor/modbus_sensor.h
+++ b/esphome/components/modbus_controller/sensor/modbus_sensor.h
@@ -25,9 +25,9 @@ class ModbusSensor : public Component, public sensor::Sensor, public SensorItem
 
   void parse_and_publish(const std::vector<uint8_t> &data) override;
   void dump_config() override;
-  using transform_func_t = std::function<optional<float>(ModbusSensor *, float, const std::vector<uint8_t> &)>;
+  using transform_func_t = optional<float> (*)(ModbusSensor *, float, const std::vector<uint8_t> &);
 
-  void set_template(transform_func_t &&f) { this->transform_func_ = f; }
+  void set_template(transform_func_t f) { this->transform_func_ = f; }
 
  protected:
   optional<transform_func_t> transform_func_{nullopt};
diff --git a/esphome/components/modbus_controller/switch/modbus_switch.h b/esphome/components/modbus_controller/switch/modbus_switch.h
index 0098076ef4..301c2bf548 100644
--- a/esphome/components/modbus_controller/switch/modbus_switch.h
+++ b/esphome/components/modbus_controller/switch/modbus_switch.h
@@ -34,10 +34,10 @@ class ModbusSwitch : public Component, public switch_::Switch, public SensorItem
   void parse_and_publish(const std::vector<uint8_t> &data) override;
   void set_parent(ModbusController *parent) { this->parent_ = parent; }
 
-  using transform_func_t = std::function<optional<bool>(ModbusSwitch *, bool, const std::vector<uint8_t> &)>;
-  using write_transform_func_t = std::function<optional<bool>(ModbusSwitch *, bool, std::vector<uint8_t> &)>;
-  void set_template(transform_func_t &&f) { this->publish_transform_func_ = f; }
-  void set_write_template(write_transform_func_t &&f) { this->write_transform_func_ = f; }
+  using transform_func_t = optional<bool> (*)(ModbusSwitch *, bool, const std::vector<uint8_t> &);
+  using write_transform_func_t = optional<bool> (*)(ModbusSwitch *, bool, std::vector<uint8_t> &);
+  void set_template(transform_func_t f) { this->publish_transform_func_ = f; }
+  void set_write_template(write_transform_func_t f) { this->write_transform_func_ = f; }
   void set_use_write_mutiple(bool use_write_multiple) { this->use_write_multiple_ = use_write_multiple; }
 
  protected:
diff --git a/esphome/components/modbus_controller/text_sensor/modbus_textsensor.h b/esphome/components/modbus_controller/text_sensor/modbus_textsensor.h
index d6eb5fd230..6666aea976 100644
--- a/esphome/components/modbus_controller/text_sensor/modbus_textsensor.h
+++ b/esphome/components/modbus_controller/text_sensor/modbus_textsensor.h
@@ -30,9 +30,8 @@ class ModbusTextSensor : public Component, public text_sensor::TextSensor, publi
   void dump_config() override;
 
   void parse_and_publish(const std::vector<uint8_t> &data) override;
-  using transform_func_t =
-      std::function<optional<std::string>(ModbusTextSensor *, std::string, const std::vector<uint8_t> &)>;
-  void set_template(transform_func_t &&f) { this->transform_func_ = f; }
+  using transform_func_t = optional<std::string> (*)(ModbusTextSensor *, std::string, const std::vector<uint8_t> &);
+  void set_template(transform_func_t f) { this->transform_func_ = f; }
 
  protected:
   optional<transform_func_t> transform_func_{nullopt};
diff --git a/tests/components/modbus_controller/common.yaml b/tests/components/modbus_controller/common.yaml
index ae5520e57d..ffaa1491c5 100644
--- a/tests/components/modbus_controller/common.yaml
+++ b/tests/components/modbus_controller/common.yaml
@@ -56,6 +56,14 @@ binary_sensor:
     register_type: read
     address: 0x3200
     bitmask: 0x80
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller1
+    id: modbus_binary_sensor2
+    name: Test Binary Sensor with Lambda
+    register_type: read
+    address: 0x3201
+    lambda: |-
+      return x;
 
 number:
   - platform: modbus_controller
@@ -65,6 +73,16 @@ number:
     address: 0x9001
     value_type: U_WORD
     multiply: 1.0
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller1
+    id: modbus_number2
+    name: Test Number with Lambda
+    address: 0x9002
+    value_type: U_WORD
+    lambda: |-
+      return x * 2.0;
+    write_lambda: |-
+      return x / 2.0;
 
 output:
   - platform: modbus_controller
@@ -74,6 +92,14 @@ output:
     register_type: holding
     value_type: U_WORD
     multiply: 1000
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller1
+    id: modbus_output2
+    address: 2049
+    register_type: holding
+    value_type: U_WORD
+    write_lambda: |-
+      return x * 100.0;
 
 select:
   - platform: modbus_controller
@@ -87,6 +113,34 @@ select:
       "One": 1
       "Two": 2
       "Three": 3
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller1
+    id: modbus_select2
+    name: Test Select with Lambda
+    address: 1001
+    value_type: U_WORD
+    optionsmap:
+      "Off": 0
+      "On": 1
+      "Two": 2
+    lambda: |-
+      ESP_LOGD("Reg1001", "Received value %lld", x);
+      if (x > 1) {
+        return std::string("Two");
+      } else if (x == 1) {
+        return std::string("On");
+      }
+      return std::string("Off");
+    write_lambda: |-
+      ESP_LOGD("Reg1001", "Set option to %s (%lld)", x.c_str(), value);
+      if (x == "On") {
+        return 1;
+      }
+      if (x == "Two") {
+        payload.push_back(0x0002);
+        return 0;
+      }
+      return value;
 
 sensor:
   - platform: modbus_controller
@@ -97,6 +151,15 @@ sensor:
     address: 0x9001
     unit_of_measurement: "AH"
     value_type: U_WORD
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller1
+    id: modbus_sensor2
+    name: Test Sensor with Lambda
+    register_type: holding
+    address: 0x9002
+    value_type: U_WORD
+    lambda: |-
+      return x / 10.0;
 
 switch:
   - platform: modbus_controller
@@ -106,6 +169,16 @@ switch:
     register_type: coil
     address: 0x15
     bitmask: 1
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller1
+    id: modbus_switch2
+    name: Test Switch with Lambda
+    register_type: coil
+    address: 0x16
+    lambda: |-
+      return !x;
+    write_lambda: |-
+      return !x;
 
 text_sensor:
   - platform: modbus_controller
@@ -117,3 +190,13 @@ text_sensor:
     register_count: 3
     raw_encode: HEXBYTES
     response_size: 6
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller1
+    id: modbus_text_sensor2
+    name: Test Text Sensor with Lambda
+    register_type: holding
+    address: 0x9014
+    register_count: 2
+    response_size: 4
+    lambda: |-
+      return "Modified: " + x;