diff --git a/esphome/components/mdns/mdns_component.cpp b/esphome/components/mdns/mdns_component.cpp
index cdd24015f5..9bf27e71e4 100644
--- a/esphome/components/mdns/mdns_component.cpp
+++ b/esphome/components/mdns/mdns_component.cpp
@@ -39,6 +39,37 @@ MDNS_STATIC_CONST_CHAR(SERVICE_TCP, "_tcp");
 // Wrap build-time defines into flash storage
 MDNS_STATIC_CONST_CHAR(VALUE_VERSION, ESPHOME_VERSION);
 
+void MDNSComponent::setup_buffers_and_register_(PlatformRegisterFn platform_register) {
+#ifdef USE_MDNS_STORE_SERVICES
+  auto &services = this->services_;
+#else
+  StaticVector<MDNSService, MDNS_SERVICE_COUNT> services_storage;
+  auto &services = services_storage;
+#endif
+
+#ifdef USE_API
+#ifdef USE_MDNS_STORE_SERVICES
+  get_mac_address_into_buffer(this->mac_address_);
+  char *mac_ptr = this->mac_address_;
+  format_hex_to(this->config_hash_str_, App.get_config_hash());
+  char *cfg_ptr = this->config_hash_str_;
+#else
+  char mac_address[MAC_ADDRESS_BUFFER_SIZE];
+  char config_hash_str[CONFIG_HASH_STR_SIZE];
+  get_mac_address_into_buffer(mac_address);
+  format_hex_to(config_hash_str, App.get_config_hash());
+  char *mac_ptr = mac_address;
+  char *cfg_ptr = config_hash_str;
+#endif
+#else
+  char *mac_ptr = nullptr;
+  char *cfg_ptr = nullptr;
+#endif
+
+  this->compile_records_(services, mac_ptr, cfg_ptr);
+  platform_register(this, services);
+}
+
 void MDNSComponent::compile_records_(StaticVector<MDNSService, MDNS_SERVICE_COUNT> &services, char *mac_address_buf,
                                      char *config_hash_buf) {
   // IMPORTANT: The #ifdef blocks below must match COMPONENTS_WITH_MDNS_SERVICES
diff --git a/esphome/components/mdns/mdns_component.h b/esphome/components/mdns/mdns_component.h
index a4aedab5fe..e981a65941 100644
--- a/esphome/components/mdns/mdns_component.h
+++ b/esphome/components/mdns/mdns_component.h
@@ -1,10 +1,7 @@
 #pragma once
 #include "esphome/core/defines.h"
 #ifdef USE_MDNS
-#include <cinttypes>
-#include <cstdio>
 #include <string>
-#include "esphome/core/application.h"
 #include "esphome/core/automation.h"
 #include "esphome/core/component.h"
 #include "esphome/core/helpers.h"
@@ -74,7 +71,7 @@ class MDNSComponent final : public Component
   void dump_config() override;
 
   /// Size of buffer required for config hash hex string (8 hex chars + null terminator)
-  static constexpr size_t CONFIG_HASH_STR_SIZE = 9;
+  static constexpr size_t CONFIG_HASH_STR_SIZE = format_hex_size(sizeof(uint32_t));
 
 #ifdef USE_MDNS_EVENT_DRIVEN_POLLING
   // LEAmDNS has meaningful work only during the probe+announce phase (3×250ms probes +
@@ -130,35 +127,7 @@ class MDNSComponent final : public Component
   /// Helper to set up services and MAC buffers, then call platform-specific registration
   using PlatformRegisterFn = void (*)(MDNSComponent *, StaticVector<MDNSService, MDNS_SERVICE_COUNT> &);
 
-  void setup_buffers_and_register_(PlatformRegisterFn platform_register) {
-#ifdef USE_MDNS_STORE_SERVICES
-    auto &services = this->services_;
-#else
-    StaticVector<MDNSService, MDNS_SERVICE_COUNT> services_storage;
-    auto &services = services_storage;
-#endif
-
-#ifdef USE_API
-#ifdef USE_MDNS_STORE_SERVICES
-    get_mac_address_into_buffer(this->mac_address_);
-    char *mac_ptr = this->mac_address_;
-    char *cfg_ptr = this->config_hash_str_;
-#else
-    char mac_address[MAC_ADDRESS_BUFFER_SIZE];
-    char config_hash_str[CONFIG_HASH_STR_SIZE];
-    get_mac_address_into_buffer(mac_address);
-    char *mac_ptr = mac_address;
-    char *cfg_ptr = config_hash_str;
-#endif
-    snprintf(cfg_ptr, CONFIG_HASH_STR_SIZE, "%08" PRIx32, App.get_config_hash());
-#else
-    char *mac_ptr = nullptr;
-    char *cfg_ptr = nullptr;
-#endif
-
-    this->compile_records_(services, mac_ptr, cfg_ptr);
-    platform_register(this, services);
-  }
+  void setup_buffers_and_register_(PlatformRegisterFn platform_register);
 
 #ifdef USE_MDNS_DYNAMIC_TXT
   /// Storage for runtime-generated TXT values from user lambdas
diff --git a/esphome/components/sx126x/__init__.py b/esphome/components/sx126x/__init__.py
index b8696158fe..a4ba5c34f3 100644
--- a/esphome/components/sx126x/__init__.py
+++ b/esphome/components/sx126x/__init__.py
@@ -1,3 +1,5 @@
+from typing import Any
+
 from esphome import automation, pins
 import esphome.codegen as cg
 from esphome.components import spi
@@ -5,6 +7,8 @@ from esphome.components.const import CONF_CRC_ENABLE, CONF_ON_PACKET
 import esphome.config_validation as cv
 from esphome.const import CONF_BUSY_PIN, CONF_DATA, CONF_FREQUENCY, CONF_ID
 from esphome.core import ID, TimePeriod
+from esphome.cpp_generator import MockObj
+from esphome.types import ConfigType, TemplateArgsType
 
 MULTI_CONF = True
 CODEOWNERS = ["@swoboda1337"]
@@ -15,6 +19,7 @@ CONF_SX126X_ID = "sx126x_id"
 CONF_BANDWIDTH = "bandwidth"
 CONF_BITRATE = "bitrate"
 CONF_CODING_RATE = "coding_rate"
+CONF_COLD = "cold"
 CONF_CRC_INVERTED = "crc_inverted"
 CONF_CRC_SIZE = "crc_size"
 CONF_CRC_POLYNOMIAL = "crc_polynomial"
@@ -144,7 +149,7 @@ SetModeStandbyAction = sx126x_ns.class_(
 )
 
 
-def validate_raw_data(value):
+def validate_raw_data(value: Any) -> bytes | list[int]:
     if isinstance(value, str):
         return value.encode("utf-8")
     if isinstance(value, list):
@@ -154,7 +159,7 @@ def validate_raw_data(value):
     )
 
 
-def validate_config(config):
+def validate_config(config: ConfigType) -> ConfigType:
     lora_bws = [
         "7_8kHz",
         "10_4kHz",
@@ -235,7 +240,7 @@ CONFIG_SCHEMA = (
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(var, config)
     await spi.register_spi_device(var, config)
@@ -307,24 +312,50 @@ NO_ARGS_ACTION_SCHEMA = automation.maybe_simple_id(
     NO_ARGS_ACTION_SCHEMA,
     synchronous=True,
 )
-@automation.register_action(
-    "sx126x.set_mode_sleep",
-    SetModeSleepAction,
-    NO_ARGS_ACTION_SCHEMA,
-    synchronous=True,
-)
 @automation.register_action(
     "sx126x.set_mode_standby",
     SetModeStandbyAction,
     NO_ARGS_ACTION_SCHEMA,
     synchronous=True,
 )
-async def no_args_action_to_code(config, action_id, template_arg, args):
+async def no_args_action_to_code(
+    config: ConfigType,
+    action_id: ID,
+    template_arg: cg.TemplateArguments,
+    args: TemplateArgsType,
+) -> MockObj:
     var = cg.new_Pvariable(action_id, template_arg)
     await cg.register_parented(var, config[CONF_ID])
     return var
 
 
+SET_MODE_SLEEP_ACTION_SCHEMA = automation.maybe_simple_id(
+    {
+        cv.GenerateID(): cv.use_id(SX126x),
+        cv.Optional(CONF_COLD, default=False): cv.templatable(cv.boolean),
+    }
+)
+
+
+@automation.register_action(
+    "sx126x.set_mode_sleep",
+    SetModeSleepAction,
+    SET_MODE_SLEEP_ACTION_SCHEMA,
+    synchronous=True,
+)
+async def set_mode_sleep_action_to_code(
+    config: ConfigType,
+    action_id: ID,
+    template_arg: cg.TemplateArguments,
+    args: TemplateArgsType,
+) -> MockObj:
+    var = cg.new_Pvariable(action_id, template_arg)
+    await cg.register_parented(var, config[CONF_ID])
+    template_ = await cg.templatable(config[CONF_COLD], args, bool)
+    cg.add(var.set_cold(template_))
+    return var
+
+
 SEND_PACKET_ACTION_SCHEMA = cv.maybe_simple_value(
     {
         cv.GenerateID(): cv.use_id(SX126x),
@@ -340,7 +371,12 @@ SEND_PACKET_ACTION_SCHEMA = cv.maybe_simple_value(
     SEND_PACKET_ACTION_SCHEMA,
     synchronous=True,
 )
-async def send_packet_action_to_code(config, action_id, template_arg, args):
+async def send_packet_action_to_code(
+    config: ConfigType,
+    action_id: ID,
+    template_arg: cg.TemplateArguments,
+    args: TemplateArgsType,
+) -> MockObj:
     var = cg.new_Pvariable(action_id, template_arg)
     await cg.register_parented(var, config[CONF_ID])
     data = config[CONF_DATA]
diff --git a/esphome/components/sx126x/automation.h b/esphome/components/sx126x/automation.h
index 2282c583cb..ed5986e097 100644
--- a/esphome/components/sx126x/automation.h
+++ b/esphome/components/sx126x/automation.h
@@ -56,7 +56,8 @@ template<typename... Ts> class SetModeRxAction : public Action<Ts...>, public Pa
 
 template<typename... Ts> class SetModeSleepAction : public Action<Ts...>, public Parented<SX126x> {
  public:
-  void play(const Ts &...x) override { this->parent_->set_mode_sleep(); }
+  TEMPLATABLE_VALUE(bool, cold)
+  void play(const Ts &...x) override { this->parent_->set_mode_sleep(this->cold_.value(x...)); }
 };
 
 template<typename... Ts> class SetModeStandbyAction : public Action<Ts...>, public Parented<SX126x> {
diff --git a/esphome/components/sx126x/sx126x.cpp b/esphome/components/sx126x/sx126x.cpp
index 6ea09e3a9e..02f7d972a9 100644
--- a/esphome/components/sx126x/sx126x.cpp
+++ b/esphome/components/sx126x/sx126x.cpp
@@ -459,9 +459,10 @@ void SX126x::set_mode_tx() {
   this->write_opcode_(RADIO_SET_TX, buf, 3);
 }
 
-void SX126x::set_mode_sleep() {
+void SX126x::set_mode_sleep(bool cold) {
+  // 0x04 = warm start (config retained), 0x00 = cold start (config lost, lowest power)
   uint8_t buf[1];
-  buf[0] = 0x05;
+  buf[0] = cold ? 0x00 : 0x04;
   this->write_opcode_(RADIO_SET_SLEEP, buf, 1);
 }
 
diff --git a/esphome/components/sx126x/sx126x.h b/esphome/components/sx126x/sx126x.h
index edc00e3727..87bbf18c79 100644
--- a/esphome/components/sx126x/sx126x.h
+++ b/esphome/components/sx126x/sx126x.h
@@ -79,7 +79,7 @@ class SX126x : public Component,
   void set_mode_rx();
   void set_mode_tx();
   void set_mode_standby(SX126xStandbyMode mode);
-  void set_mode_sleep();
+  void set_mode_sleep(bool cold = false);
   void set_modulation(uint8_t modulation) { this->modulation_ = modulation; }
   void set_pa_power(int8_t power) { this->pa_power_ = power; }
   void set_pa_ramp(uint8_t ramp) { this->pa_ramp_ = ramp; }