From b74715fe1412c905404bd5336d72cbd753c62321 Mon Sep 17 00:00:00 2001
From: Jonathan Swoboda <154711427+swoboda1337@users.noreply.github.com>
Date: Tue, 7 Oct 2025 22:55:59 -0400
Subject: [PATCH 01/14] [esp32] Fix issue when framework source is set (#11106)

---
 esphome/components/esp32/__init__.py | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/esphome/components/esp32/__init__.py b/esphome/components/esp32/__init__.py
index 3fbbf68c71..860f2450e6 100644
--- a/esphome/components/esp32/__init__.py
+++ b/esphome/components/esp32/__init__.py
@@ -386,6 +386,10 @@ def _check_versions(value):
         value[CONF_SOURCE] = value.get(
             CONF_SOURCE, _format_framework_arduino_version(version)
         )
+        if value[CONF_SOURCE].startswith("http"):
+            value[CONF_SOURCE] = (
+                f"pioarduino/framework-arduinoespressif32@{value[CONF_SOURCE]}"
+            )
     else:
         if version < cv.Version(5, 0, 0):
             raise cv.Invalid("Only ESP-IDF 5.0+ is supported.")
@@ -395,6 +399,8 @@ def _check_versions(value):
             CONF_SOURCE,
             _format_framework_espidf_version(version, value.get(CONF_RELEASE, None)),
         )
+        if value[CONF_SOURCE].startswith("http"):
+            value[CONF_SOURCE] = f"pioarduino/framework-espidf@{value[CONF_SOURCE]}"
 
     if CONF_PLATFORM_VERSION not in value:
         if platform_lookup is None:

From a541549d239ad615cd1784188b9695202829bfbd Mon Sep 17 00:00:00 2001
From: Jesse Hills <3060199+jesserockz@users.noreply.github.com>
Date: Wed, 8 Oct 2025 16:05:09 +1300
Subject: [PATCH 02/14] [core] Fix dynamic auto load priority (#11112)

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

diff --git a/esphome/config.py b/esphome/config.py
index 7a083fee33..10a5733575 100644
--- a/esphome/config.py
+++ b/esphome/config.py
@@ -647,7 +647,7 @@ class AddDynamicAutoLoadsValidationStep(ConfigValidationStep):
     """
 
     # Has to happen after normal schema is validated and before final schema validation
-    priority = -10.0
+    priority = -5.0
 
     def __init__(self, path: ConfigPath, comp: ComponentManifest) -> None:
         self.path = path

From a0f4de1bfbda18b9160478fbc4dfd85a8ba670a2 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Wed, 8 Oct 2025 03:35:17 +0000
Subject: [PATCH 03/14] Bump aioesphomeapi from 41.12.0 to 41.13.0 (#11113)

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 requirements.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/requirements.txt b/requirements.txt
index 81d3638c08..7ff4a6eeb2 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -12,7 +12,7 @@ platformio==6.1.18  # When updating platformio, also update /docker/Dockerfile
 esptool==5.1.0
 click==8.1.7
 esphome-dashboard==20250904.0
-aioesphomeapi==41.12.0
+aioesphomeapi==41.13.0
 zeroconf==0.148.0
 puremagic==1.30
 ruamel.yaml==0.18.15 # dashboard_import

From 0fe6e7169c1aa87571d62946ea91a64904382c83 Mon Sep 17 00:00:00 2001
From: carlessolegrau <46353439+carlessole@users.noreply.github.com>
Date: Wed, 8 Oct 2025 05:40:49 +0200
Subject: [PATCH 04/14] [modbus_controller] courtesy response (#10027)

Co-authored-by: Jesse Hills <3060199+jesserockz@users.noreply.github.com>
Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>
---
 esphome/components/modbus/modbus.cpp          | 40 ++++++---
 esphome/components/modbus/modbus.h            |  8 +-
 .../components/modbus/modbus_definitions.h    | 86 +++++++++++++++++++
 .../components/modbus_controller/__init__.py  | 30 ++++++-
 esphome/components/modbus_controller/const.py |  4 +
 .../modbus_controller/modbus_controller.cpp   | 51 ++++++++---
 .../modbus_controller/modbus_controller.h     | 47 ++++------
 .../components/modbus_controller/common.yaml  | 16 ++++
 8 files changed, 223 insertions(+), 59 deletions(-)
 create mode 100644 esphome/components/modbus/modbus_definitions.h

diff --git a/esphome/components/modbus/modbus.cpp b/esphome/components/modbus/modbus.cpp
index 6350f43ef6..20271b4bdb 100644
--- a/esphome/components/modbus/modbus.cpp
+++ b/esphome/components/modbus/modbus.cpp
@@ -66,7 +66,10 @@ bool Modbus::parse_modbus_byte_(uint8_t byte) {
   uint8_t data_offset = 3;
 
   // Per https://modbus.org/docs/Modbus_Application_Protocol_V1_1b3.pdf Ch 5 User-Defined function codes
-  if (((function_code >= 65) && (function_code <= 72)) || ((function_code >= 100) && (function_code <= 110))) {
+  if (((function_code >= FUNCTION_CODE_USER_DEFINED_SPACE_1_INIT) &&
+       (function_code <= FUNCTION_CODE_USER_DEFINED_SPACE_1_END)) ||
+      ((function_code >= FUNCTION_CODE_USER_DEFINED_SPACE_2_INIT) &&
+       (function_code <= FUNCTION_CODE_USER_DEFINED_SPACE_2_END))) {
     // Handle user-defined function, since we don't know how big this ought to be,
     // ideally we should delegate the entire length detection to whatever handler is
     // installed, but wait, there is the CRC, and if we get a hit there is a good
@@ -91,10 +94,14 @@ bool Modbus::parse_modbus_byte_(uint8_t byte) {
   } else {
     // data starts at 2 and length is 4 for read registers commands
     if (this->role == ModbusRole::SERVER) {
-      if (function_code == 0x1 || function_code == 0x3 || function_code == 0x4 || function_code == 0x6) {
+      if (function_code == ModbusFunctionCode::READ_COILS ||
+          function_code == ModbusFunctionCode::READ_DISCRETE_INPUTS ||
+          function_code == ModbusFunctionCode::READ_HOLDING_REGISTERS ||
+          function_code == ModbusFunctionCode::READ_INPUT_REGISTERS ||
+          function_code == ModbusFunctionCode::WRITE_SINGLE_REGISTER) {
         data_offset = 2;
         data_len = 4;
-      } else if (function_code == 0x10) {
+      } else if (function_code == ModbusFunctionCode::WRITE_MULTIPLE_REGISTERS) {
         if (at < 6) {
           return true;
         }
@@ -104,7 +111,10 @@ bool Modbus::parse_modbus_byte_(uint8_t byte) {
       }
     } else {
       // the response for write command mirrors the requests and data starts at offset 2 instead of 3 for read commands
-      if (function_code == 0x5 || function_code == 0x06 || function_code == 0xF || function_code == 0x10) {
+      if (function_code == ModbusFunctionCode::WRITE_SINGLE_COIL ||
+          function_code == ModbusFunctionCode::WRITE_SINGLE_REGISTER ||
+          function_code == ModbusFunctionCode::WRITE_MULTIPLE_COILS ||
+          function_code == ModbusFunctionCode::WRITE_MULTIPLE_REGISTERS) {
         data_offset = 2;
         data_len = 4;
       }
@@ -112,7 +122,7 @@ bool Modbus::parse_modbus_byte_(uint8_t byte) {
 
     // Error ( msb indicates error )
     // response format:  Byte[0] = device address, Byte[1] function code | 0x80 , Byte[2] exception code, Byte[3-4] crc
-    if ((function_code & 0x80) == 0x80) {
+    if ((function_code & FUNCTION_CODE_EXCEPTION_MASK) == FUNCTION_CODE_EXCEPTION_MASK) {
       data_offset = 2;
       data_len = 1;
     }
@@ -143,10 +153,10 @@ bool Modbus::parse_modbus_byte_(uint8_t byte) {
     if (device->address_ == address) {
       found = true;
       // Is it an error response?
-      if ((function_code & 0x80) == 0x80) {
+      if ((function_code & FUNCTION_CODE_EXCEPTION_MASK) == FUNCTION_CODE_EXCEPTION_MASK) {
         ESP_LOGD(TAG, "Modbus error function code: 0x%X exception: %d", function_code, raw[2]);
         if (waiting_for_response != 0) {
-          device->on_modbus_error(function_code & 0x7F, raw[2]);
+          device->on_modbus_error(function_code & FUNCTION_CODE_MASK, raw[2]);
         } else {
           // Ignore modbus exception not related to a pending command
           ESP_LOGD(TAG, "Ignoring Modbus error - not expecting a response");
@@ -154,12 +164,14 @@ bool Modbus::parse_modbus_byte_(uint8_t byte) {
         continue;
       }
       if (this->role == ModbusRole::SERVER) {
-        if (function_code == 0x3 || function_code == 0x4) {
+        if (function_code == ModbusFunctionCode::READ_HOLDING_REGISTERS ||
+            function_code == ModbusFunctionCode::READ_INPUT_REGISTERS) {
           device->on_modbus_read_registers(function_code, uint16_t(data[1]) | (uint16_t(data[0]) << 8),
                                            uint16_t(data[3]) | (uint16_t(data[2]) << 8));
           continue;
         }
-        if (function_code == 0x6 || function_code == 0x10) {
+        if (function_code == ModbusFunctionCode::WRITE_SINGLE_REGISTER ||
+            function_code == ModbusFunctionCode::WRITE_MULTIPLE_REGISTERS) {
           device->on_modbus_write_registers(function_code, data);
           continue;
         }
@@ -199,7 +211,7 @@ void Modbus::send(uint8_t address, uint8_t function_code, uint16_t start_address
 
   // Only check max number of registers for standard function codes
   // Some devices use non standard codes like 0x43
-  if (number_of_entities > MAX_VALUES && function_code <= 0x10) {
+  if (number_of_entities > MAX_VALUES && function_code <= ModbusFunctionCode::WRITE_MULTIPLE_REGISTERS) {
     ESP_LOGE(TAG, "send too many values %d max=%zu", number_of_entities, MAX_VALUES);
     return;
   }
@@ -210,15 +222,17 @@ void Modbus::send(uint8_t address, uint8_t function_code, uint16_t start_address
   if (this->role == ModbusRole::CLIENT) {
     data.push_back(start_address >> 8);
     data.push_back(start_address >> 0);
-    if (function_code != 0x5 && function_code != 0x6) {
+    if (function_code != ModbusFunctionCode::WRITE_SINGLE_COIL &&
+        function_code != ModbusFunctionCode::WRITE_SINGLE_REGISTER) {
       data.push_back(number_of_entities >> 8);
       data.push_back(number_of_entities >> 0);
     }
   }
 
   if (payload != nullptr) {
-    if (this->role == ModbusRole::SERVER || function_code == 0xF || function_code == 0x10) {  // Write multiple
-      data.push_back(payload_len);  // Byte count is required for write
+    if (this->role == ModbusRole::SERVER || function_code == ModbusFunctionCode::WRITE_MULTIPLE_COILS ||
+        function_code == ModbusFunctionCode::WRITE_MULTIPLE_REGISTERS) {  // Write multiple
+      data.push_back(payload_len);                                        // Byte count is required for write
     } else {
       payload_len = 2;  // Write single register or coil
     }
diff --git a/esphome/components/modbus/modbus.h b/esphome/components/modbus/modbus.h
index ec35612690..fac74aaadf 100644
--- a/esphome/components/modbus/modbus.h
+++ b/esphome/components/modbus/modbus.h
@@ -3,6 +3,8 @@
 #include "esphome/core/component.h"
 #include "esphome/components/uart/uart.h"
 
+#include "esphome/components/modbus/modbus_definitions.h"
+
 #include <vector>
 
 namespace esphome {
@@ -65,12 +67,12 @@ class ModbusDevice {
     this->parent_->send(this->address_, function, start_address, number_of_entities, payload_len, payload);
   }
   void send_raw(const std::vector<uint8_t> &payload) { this->parent_->send_raw(payload); }
-  void send_error(uint8_t function_code, uint8_t exception_code) {
+  void send_error(uint8_t function_code, ModbusExceptionCode exception_code) {
     std::vector<uint8_t> error_response;
     error_response.reserve(3);
     error_response.push_back(this->address_);
-    error_response.push_back(function_code | 0x80);
-    error_response.push_back(exception_code);
+    error_response.push_back(function_code | FUNCTION_CODE_EXCEPTION_MASK);
+    error_response.push_back(static_cast<uint8_t>(exception_code));
     this->send_raw(error_response);
   }
   // If more than one device is connected block sending a new command before a response is received
diff --git a/esphome/components/modbus/modbus_definitions.h b/esphome/components/modbus/modbus_definitions.h
new file mode 100644
index 0000000000..07f101ae4c
--- /dev/null
+++ b/esphome/components/modbus/modbus_definitions.h
@@ -0,0 +1,86 @@
+#pragma once
+
+#include "esphome/core/component.h"
+
+namespace esphome {
+namespace modbus {
+
+/// Modbus definitions from specs:
+/// https://modbus.org/docs/Modbus_Application_Protocol_V1_1b3.pdf
+// 5 Function Code Categories
+const uint8_t FUNCTION_CODE_USER_DEFINED_SPACE_1_INIT = 65;  // 0x41
+const uint8_t FUNCTION_CODE_USER_DEFINED_SPACE_1_END = 72;   // 0x48
+
+const uint8_t FUNCTION_CODE_USER_DEFINED_SPACE_2_INIT = 100;  // 0x64
+const uint8_t FUNCTION_CODE_USER_DEFINED_SPACE_2_END = 110;   // 0x6E
+
+enum class ModbusFunctionCode : uint8_t {
+  CUSTOM = 0x00,
+  READ_COILS = 0x01,
+  READ_DISCRETE_INPUTS = 0x02,
+  READ_HOLDING_REGISTERS = 0x03,
+  READ_INPUT_REGISTERS = 0x04,
+  WRITE_SINGLE_COIL = 0x05,
+  WRITE_SINGLE_REGISTER = 0x06,
+  READ_EXCEPTION_STATUS = 0x07,   // not implemented
+  DIAGNOSTICS = 0x08,             // not implemented
+  GET_COMM_EVENT_COUNTER = 0x0B,  // not implemented
+  GET_COMM_EVENT_LOG = 0x0C,      // not implemented
+  WRITE_MULTIPLE_COILS = 0x0F,
+  WRITE_MULTIPLE_REGISTERS = 0x10,
+  REPORT_SERVER_ID = 0x11,               // not implemented
+  READ_FILE_RECORD = 0x14,               // not implemented
+  WRITE_FILE_RECORD = 0x15,              // not implemented
+  MASK_WRITE_REGISTER = 0x16,            // not implemented
+  READ_WRITE_MULTIPLE_REGISTERS = 0x17,  // not implemented
+  READ_FIFO_QUEUE = 0x18,                // not implemented
+};
+
+/*Allow  comparison operators between ModbusFunctionCode and uint8_t*/
+inline bool operator==(ModbusFunctionCode lhs, uint8_t rhs) { return static_cast<uint8_t>(lhs) == rhs; }
+inline bool operator==(uint8_t lhs, ModbusFunctionCode rhs) { return lhs == static_cast<uint8_t>(rhs); }
+inline bool operator!=(ModbusFunctionCode lhs, uint8_t rhs) { return !(static_cast<uint8_t>(lhs) == rhs); }
+inline bool operator!=(uint8_t lhs, ModbusFunctionCode rhs) { return !(lhs == static_cast<uint8_t>(rhs)); }
+inline bool operator<(ModbusFunctionCode lhs, uint8_t rhs) { return static_cast<uint8_t>(lhs) < rhs; }
+inline bool operator<(uint8_t lhs, ModbusFunctionCode rhs) { return lhs < static_cast<uint8_t>(rhs); }
+inline bool operator<=(ModbusFunctionCode lhs, uint8_t rhs) { return static_cast<uint8_t>(lhs) <= rhs; }
+inline bool operator<=(uint8_t lhs, ModbusFunctionCode rhs) { return lhs <= static_cast<uint8_t>(rhs); }
+inline bool operator>(ModbusFunctionCode lhs, uint8_t rhs) { return static_cast<uint8_t>(lhs) > rhs; }
+inline bool operator>(uint8_t lhs, ModbusFunctionCode rhs) { return lhs > static_cast<uint8_t>(rhs); }
+inline bool operator>=(ModbusFunctionCode lhs, uint8_t rhs) { return static_cast<uint8_t>(lhs) >= rhs; }
+inline bool operator>=(uint8_t lhs, ModbusFunctionCode rhs) { return lhs >= static_cast<uint8_t>(rhs); }
+
+// 4.3 MODBUS Data model
+enum class ModbusRegisterType : uint8_t {
+  CUSTOM = 0x00,
+  COIL = 0x01,
+  DISCRETE_INPUT = 0x02,
+  HOLDING = 0x03,
+  READ = 0x04,
+};
+
+// 7 MODBUS Exception Responses:
+const uint8_t FUNCTION_CODE_MASK = 0x7F;
+const uint8_t FUNCTION_CODE_EXCEPTION_MASK = 0x80;
+
+enum class ModbusExceptionCode : uint8_t {
+  ILLEGAL_FUNCTION = 0x01,
+  ILLEGAL_DATA_ADDRESS = 0x02,
+  ILLEGAL_DATA_VALUE = 0x03,
+  SERVICE_DEVICE_FAILURE = 0x04,
+  ACKNOWLEDGE = 0x05,
+  SERVER_DEVICE_BUSY = 0x06,
+  MEMORY_PARITY_ERROR = 0x08,
+  GATEWAY_PATH_UNAVAILABLE = 0x0A,
+  GATEWAY_TARGET_DEVICE_FAILED_TO_RESPOND = 0x0B,
+};
+
+// 6.12 16 (0x10) Write Multiple registers:
+const uint8_t MAX_NUM_OF_REGISTERS_TO_WRITE = 123;  // 0x7B
+
+// 6.3 03 (0x03) Read Holding Registers
+// 6.4 04 (0x04) Read Input Registers
+const uint8_t MAX_NUM_OF_REGISTERS_TO_READ = 125;  // 0x7D
+/// End of Modbus definitions
+}  // namespace modbus
+}  // namespace esphome
diff --git a/esphome/components/modbus_controller/__init__.py b/esphome/components/modbus_controller/__init__.py
index 5ab82f5e17..28f3326c47 100644
--- a/esphome/components/modbus_controller/__init__.py
+++ b/esphome/components/modbus_controller/__init__.py
@@ -20,6 +20,7 @@ from .const import (
     CONF_BYTE_OFFSET,
     CONF_COMMAND_THROTTLE,
     CONF_CUSTOM_COMMAND,
+    CONF_ENABLED,
     CONF_FORCE_NEW_RANGE,
     CONF_MAX_CMD_RETRIES,
     CONF_MODBUS_CONTROLLER_ID,
@@ -28,8 +29,11 @@ from .const import (
     CONF_ON_OFFLINE,
     CONF_ON_ONLINE,
     CONF_REGISTER_COUNT,
+    CONF_REGISTER_LAST_ADDRESS,
     CONF_REGISTER_TYPE,
+    CONF_REGISTER_VALUE,
     CONF_RESPONSE_SIZE,
+    CONF_SERVER_COURTESY_RESPONSE,
     CONF_SKIP_UPDATES,
     CONF_VALUE_TYPE,
 )
@@ -49,6 +53,7 @@ ModbusController = modbus_controller_ns.class_(
 )
 
 SensorItem = modbus_controller_ns.struct("SensorItem")
+ServerCourtesyResponse = modbus_controller_ns.struct("ServerCourtesyResponse")
 ServerRegister = modbus_controller_ns.struct("ServerRegister")
 
 ModbusFunctionCode_ns = modbus_controller_ns.namespace("ModbusFunctionCode")
@@ -143,6 +148,14 @@ ModbusOfflineTrigger = modbus_controller_ns.class_(
 
 _LOGGER = logging.getLogger(__name__)
 
+SERVER_COURTESY_RESPONSE_SCHEMA = cv.Schema(
+    {
+        cv.Optional(CONF_ENABLED, default=False): cv.boolean,
+        cv.Optional(CONF_REGISTER_LAST_ADDRESS, default=0xFFFF): cv.hex_uint16_t,
+        cv.Optional(CONF_REGISTER_VALUE, default=0): cv.hex_uint16_t,
+    }
+)
+
 ModbusServerRegisterSchema = cv.Schema(
     {
         cv.GenerateID(): cv.declare_id(ServerRegister),
@@ -162,6 +175,7 @@ CONFIG_SCHEMA = cv.All(
             cv.Optional(
                 CONF_COMMAND_THROTTLE, default="0ms"
             ): cv.positive_time_period_milliseconds,
+            cv.Optional(CONF_SERVER_COURTESY_RESPONSE): SERVER_COURTESY_RESPONSE_SCHEMA,
             cv.Optional(CONF_MAX_CMD_RETRIES, default=4): cv.positive_int,
             cv.Optional(CONF_OFFLINE_SKIP_UPDATES, default=0): cv.positive_int,
             cv.Optional(
@@ -232,7 +246,7 @@ def validate_modbus_register(config):
 
 
 def _final_validate(config):
-    if CONF_SERVER_REGISTERS in config:
+    if CONF_SERVER_COURTESY_RESPONSE in config or CONF_SERVER_REGISTERS in config:
         return modbus.final_validate_modbus_device("modbus_controller", role="server")(
             config
         )
@@ -299,6 +313,20 @@ async def to_code(config):
     var = cg.new_Pvariable(config[CONF_ID])
     cg.add(var.set_allow_duplicate_commands(config[CONF_ALLOW_DUPLICATE_COMMANDS]))
     cg.add(var.set_command_throttle(config[CONF_COMMAND_THROTTLE]))
+    if server_courtesy_response := config.get(CONF_SERVER_COURTESY_RESPONSE):
+        cg.add(
+            var.set_server_courtesy_response(
+                cg.StructInitializer(
+                    ServerCourtesyResponse,
+                    ("enabled", server_courtesy_response[CONF_ENABLED]),
+                    (
+                        "register_last_address",
+                        server_courtesy_response[CONF_REGISTER_LAST_ADDRESS],
+                    ),
+                    ("register_value", server_courtesy_response[CONF_REGISTER_VALUE]),
+                )
+            )
+        )
     cg.add(var.set_max_cmd_retries(config[CONF_MAX_CMD_RETRIES]))
     cg.add(var.set_offline_skip_updates(config[CONF_OFFLINE_SKIP_UPDATES]))
     if CONF_SERVER_REGISTERS in config:
diff --git a/esphome/components/modbus_controller/const.py b/esphome/components/modbus_controller/const.py
index 4d39e48dcd..ee0b5fc633 100644
--- a/esphome/components/modbus_controller/const.py
+++ b/esphome/components/modbus_controller/const.py
@@ -2,6 +2,7 @@ CONF_ALLOW_DUPLICATE_COMMANDS = "allow_duplicate_commands"
 CONF_BITMASK = "bitmask"
 CONF_BYTE_OFFSET = "byte_offset"
 CONF_COMMAND_THROTTLE = "command_throttle"
+CONF_ENABLED = "enabled"
 CONF_OFFLINE_SKIP_UPDATES = "offline_skip_updates"
 CONF_CUSTOM_COMMAND = "custom_command"
 CONF_FORCE_NEW_RANGE = "force_new_range"
@@ -13,8 +14,11 @@ CONF_ON_ONLINE = "on_online"
 CONF_ON_OFFLINE = "on_offline"
 CONF_RAW_ENCODE = "raw_encode"
 CONF_REGISTER_COUNT = "register_count"
+CONF_REGISTER_LAST_ADDRESS = "register_last_address"
 CONF_REGISTER_TYPE = "register_type"
+CONF_REGISTER_VALUE = "register_value"
 CONF_RESPONSE_SIZE = "response_size"
+CONF_SERVER_COURTESY_RESPONSE = "server_courtesy_response"
 CONF_SKIP_UPDATES = "skip_updates"
 CONF_USE_WRITE_MULTIPLE = "use_write_multiple"
 CONF_VALUE_TYPE = "value_type"
diff --git a/esphome/components/modbus_controller/modbus_controller.cpp b/esphome/components/modbus_controller/modbus_controller.cpp
index 0f3ddf920d..50bd9f45cb 100644
--- a/esphome/components/modbus_controller/modbus_controller.cpp
+++ b/esphome/components/modbus_controller/modbus_controller.cpp
@@ -112,6 +112,12 @@ void ModbusController::on_modbus_read_registers(uint8_t function_code, uint16_t
            "0x%X.",
            this->address_, function_code, start_address, number_of_registers);
 
+  if (number_of_registers == 0 || number_of_registers > modbus::MAX_NUM_OF_REGISTERS_TO_READ) {
+    ESP_LOGW(TAG, "Invalid number of registers %d. Sending exception response.", number_of_registers);
+    this->send_error(function_code, ModbusExceptionCode::ILLEGAL_DATA_ADDRESS);
+    return;
+  }
+
   std::vector<uint16_t> sixteen_bit_response;
   for (uint16_t current_address = start_address; current_address < start_address + number_of_registers;) {
     bool found = false;
@@ -136,9 +142,21 @@ void ModbusController::on_modbus_read_registers(uint8_t function_code, uint16_t
     }
 
     if (!found) {
-      ESP_LOGW(TAG, "Could not match any register to address %02X. Sending exception response.", current_address);
-      send_error(function_code, 0x02);
-      return;
+      if (this->server_courtesy_response_.enabled &&
+          (current_address <= this->server_courtesy_response_.register_last_address)) {
+        ESP_LOGD(TAG,
+                 "Could not match any register to address 0x%02X, but default allowed. "
+                 "Returning default value: %d.",
+                 current_address, this->server_courtesy_response_.register_value);
+        sixteen_bit_response.push_back(this->server_courtesy_response_.register_value);
+        current_address += 1;  // Just increment by 1, as the default response is a single register
+      } else {
+        ESP_LOGW(TAG,
+                 "Could not match any register to address 0x%02X and default not allowed. Sending exception response.",
+                 current_address);
+        this->send_error(function_code, ModbusExceptionCode::ILLEGAL_DATA_ADDRESS);
+        return;
+      }
     }
   }
 
@@ -156,27 +174,27 @@ void ModbusController::on_modbus_write_registers(uint8_t function_code, const st
   uint16_t number_of_registers;
   uint16_t payload_offset;
 
-  if (function_code == 0x10) {
+  if (function_code == ModbusFunctionCode::WRITE_MULTIPLE_REGISTERS) {
     number_of_registers = uint16_t(data[3]) | (uint16_t(data[2]) << 8);
-    if (number_of_registers == 0 || number_of_registers > 0x7B) {
+    if (number_of_registers == 0 || number_of_registers > modbus::MAX_NUM_OF_REGISTERS_TO_WRITE) {
       ESP_LOGW(TAG, "Invalid number of registers %d. Sending exception response.", number_of_registers);
-      send_error(function_code, 3);
+      this->send_error(function_code, ModbusExceptionCode::ILLEGAL_DATA_VALUE);
       return;
     }
     uint16_t payload_size = data[4];
     if (payload_size != number_of_registers * 2) {
       ESP_LOGW(TAG, "Payload size of %d bytes is not 2 times the number of registers (%d). Sending exception response.",
                payload_size, number_of_registers);
-      send_error(function_code, 3);
+      this->send_error(function_code, ModbusExceptionCode::ILLEGAL_DATA_VALUE);
       return;
     }
     payload_offset = 5;
-  } else if (function_code == 0x06) {
+  } else if (function_code == ModbusFunctionCode::WRITE_SINGLE_REGISTER) {
     number_of_registers = 1;
     payload_offset = 2;
   } else {
     ESP_LOGW(TAG, "Invalid function code 0x%X. Sending exception response.", function_code);
-    send_error(function_code, 1);
+    this->send_error(function_code, ModbusExceptionCode::ILLEGAL_FUNCTION);
     return;
   }
 
@@ -211,7 +229,7 @@ void ModbusController::on_modbus_write_registers(uint8_t function_code, const st
   if (!for_each_register([](ServerRegister *server_register, uint16_t offset) -> bool {
         return server_register->write_lambda != nullptr;
       })) {
-    send_error(function_code, 1);
+    this->send_error(function_code, ModbusExceptionCode::ILLEGAL_FUNCTION);
     return;
   }
 
@@ -220,7 +238,7 @@ void ModbusController::on_modbus_write_registers(uint8_t function_code, const st
         int64_t number = payload_to_number(data, server_register->value_type, offset, 0xFFFFFFFF);
         return server_register->write_lambda(number);
       })) {
-    send_error(function_code, 4);
+    this->send_error(function_code, ModbusExceptionCode::SERVICE_DEVICE_FAILURE);
     return;
   }
 
@@ -431,8 +449,15 @@ void ModbusController::dump_config() {
                 "ModbusController:\n"
                 "  Address: 0x%02X\n"
                 "  Max Command Retries: %d\n"
-                "  Offline Skip Updates: %d",
-                this->address_, this->max_cmd_retries_, this->offline_skip_updates_);
+                "  Offline Skip Updates: %d\n"
+                "  Server Courtesy Response:\n"
+                "    Enabled: %s\n"
+                "    Register Last Address: 0x%02X\n"
+                "    Register Value: %d",
+                this->address_, this->max_cmd_retries_, this->offline_skip_updates_,
+                this->server_courtesy_response_.enabled ? "true" : "false",
+                this->server_courtesy_response_.register_last_address, this->server_courtesy_response_.register_value);
+
 #if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_VERBOSE
   ESP_LOGCONFIG(TAG, "sensormap");
   for (auto &it : this->sensorset_) {
diff --git a/esphome/components/modbus_controller/modbus_controller.h b/esphome/components/modbus_controller/modbus_controller.h
index a86ad1ccb5..6ed05715cb 100644
--- a/esphome/components/modbus_controller/modbus_controller.h
+++ b/esphome/components/modbus_controller/modbus_controller.h
@@ -16,35 +16,9 @@ namespace modbus_controller {
 
 class ModbusController;
 
-enum class ModbusFunctionCode {
-  CUSTOM = 0x00,
-  READ_COILS = 0x01,
-  READ_DISCRETE_INPUTS = 0x02,
-  READ_HOLDING_REGISTERS = 0x03,
-  READ_INPUT_REGISTERS = 0x04,
-  WRITE_SINGLE_COIL = 0x05,
-  WRITE_SINGLE_REGISTER = 0x06,
-  READ_EXCEPTION_STATUS = 0x07,   // not implemented
-  DIAGNOSTICS = 0x08,             // not implemented
-  GET_COMM_EVENT_COUNTER = 0x0B,  // not implemented
-  GET_COMM_EVENT_LOG = 0x0C,      // not implemented
-  WRITE_MULTIPLE_COILS = 0x0F,
-  WRITE_MULTIPLE_REGISTERS = 0x10,
-  REPORT_SERVER_ID = 0x11,               // not implemented
-  READ_FILE_RECORD = 0x14,               // not implemented
-  WRITE_FILE_RECORD = 0x15,              // not implemented
-  MASK_WRITE_REGISTER = 0x16,            // not implemented
-  READ_WRITE_MULTIPLE_REGISTERS = 0x17,  // not implemented
-  READ_FIFO_QUEUE = 0x18,                // not implemented
-};
-
-enum class ModbusRegisterType : uint8_t {
-  CUSTOM = 0x0,
-  COIL = 0x01,
-  DISCRETE_INPUT = 0x02,
-  HOLDING = 0x03,
-  READ = 0x04,
-};
+using modbus::ModbusFunctionCode;
+using modbus::ModbusRegisterType;
+using modbus::ModbusExceptionCode;
 
 enum class SensorValueType : uint8_t {
   RAW = 0x00,     // variable length
@@ -256,6 +230,12 @@ class SensorItem {
   bool force_new_range{false};
 };
 
+struct ServerCourtesyResponse {
+  bool enabled{false};
+  uint16_t register_last_address{0xFFFF};
+  uint16_t register_value{0};
+};
+
 class ServerRegister {
   using ReadLambda = std::function<int64_t()>;
   using WriteLambda = std::function<bool(int64_t value)>;
@@ -530,6 +510,12 @@ class ModbusController : public PollingComponent, public modbus::ModbusDevice {
   void set_max_cmd_retries(uint8_t max_cmd_retries) { this->max_cmd_retries_ = max_cmd_retries; }
   /// get how many times a command will be (re)sent if no response is received
   uint8_t get_max_cmd_retries() { return this->max_cmd_retries_; }
+  /// Called by esphome generated code to set the server courtesy response object
+  void set_server_courtesy_response(const ServerCourtesyResponse &server_courtesy_response) {
+    this->server_courtesy_response_ = server_courtesy_response;
+  }
+  /// Get the server courtesy response object
+  ServerCourtesyResponse get_server_courtesy_response() const { return this->server_courtesy_response_; }
 
  protected:
   /// parse sensormap_ and create range of sequential addresses
@@ -572,6 +558,9 @@ class ModbusController : public PollingComponent, public modbus::ModbusDevice {
   CallbackManager<void(int, int)> online_callback_{};
   /// Server offline callback
   CallbackManager<void(int, int)> offline_callback_{};
+  /// Server courtesy response
+  ServerCourtesyResponse server_courtesy_response_{
+      .enabled = false, .register_last_address = 0xFFFF, .register_value = 0};
 };
 
 /** Convert vector<uint8_t> response payload to float.
diff --git a/tests/components/modbus_controller/common.yaml b/tests/components/modbus_controller/common.yaml
index 7d342ee353..c2b5ab737f 100644
--- a/tests/components/modbus_controller/common.yaml
+++ b/tests/components/modbus_controller/common.yaml
@@ -45,6 +45,22 @@ modbus_controller:
           printf("address=%d, value=%d", x);
           return true;
     max_cmd_retries: 0
+  - id: modbus_controller4
+    modbus_id: mod_bus2
+    address: 0x4
+    server_courtesy_response:
+      enabled: true
+      register_last_address: 100
+      register_value: 0
+    server_registers:
+      - address: 0x0001
+        value_type: U_WORD
+        read_lambda: |-
+          return 0x8;
+      - address: 0x0005
+        value_type: U_WORD
+        read_lambda: |-
+          return (random_uint32() % 100);
 binary_sensor:
   - platform: modbus_controller
     modbus_controller_id: modbus_controller1

From ec63247ae0a480348cdef8ae00d9a73b78bd5f20 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Tue, 7 Oct 2025 18:19:29 -1000
Subject: [PATCH 05/14] [mdns] Fix delete/malloc bug and store string constants
 in flash (#11105)

---
 esphome/components/mdns/__init__.py          |  8 ++--
 esphome/components/mdns/mdns_component.cpp   | 43 +++++++++-----------
 esphome/components/mdns/mdns_component.h     | 19 +++++++--
 esphome/components/mdns/mdns_esp32.cpp       | 14 +++----
 esphome/components/mdns/mdns_esp8266.cpp     | 12 +++---
 esphome/components/mdns/mdns_libretiny.cpp   |  6 +--
 esphome/components/mdns/mdns_rp2040.cpp      |  6 +--
 esphome/components/openthread/openthread.cpp |  4 +-
 8 files changed, 61 insertions(+), 51 deletions(-)

diff --git a/esphome/components/mdns/__init__.py b/esphome/components/mdns/__init__.py
index ce0241677d..3fa4d2ebef 100644
--- a/esphome/components/mdns/__init__.py
+++ b/esphome/components/mdns/__init__.py
@@ -61,7 +61,7 @@ CONFIG_SCHEMA = cv.All(
 def mdns_txt_record(key: str, value: str):
     return cg.StructInitializer(
         MDNSTXTRecord,
-        ("key", key),
+        ("key", cg.RawExpression(f"MDNS_STR({cg.safe_exp(key)})")),
         ("value", value),
     )
 
@@ -71,8 +71,8 @@ def mdns_service(
 ):
     return cg.StructInitializer(
         MDNSService,
-        ("service_type", service),
-        ("proto", proto),
+        ("service_type", cg.RawExpression(f"MDNS_STR({cg.safe_exp(service)})")),
+        ("proto", cg.RawExpression(f"MDNS_STR({cg.safe_exp(proto)})")),
         ("port", port),
         ("txt_records", txt_records),
     )
@@ -114,7 +114,7 @@ async def to_code(config):
         txt = [
             cg.StructInitializer(
                 MDNSTXTRecord,
-                ("key", txt_key),
+                ("key", cg.RawExpression(f"MDNS_STR({cg.safe_exp(txt_key)})")),
                 ("value", await cg.templatable(txt_value, [], cg.std_string)),
             )
             for txt_key, txt_value in service[CONF_TXT].items()
diff --git a/esphome/components/mdns/mdns_component.cpp b/esphome/components/mdns/mdns_component.cpp
index eed2516c6a..8945053b7d 100644
--- a/esphome/components/mdns/mdns_component.cpp
+++ b/esphome/components/mdns/mdns_component.cpp
@@ -9,24 +9,21 @@
 #include <pgmspace.h>
 // Macro to define strings in PROGMEM on ESP8266, regular memory on other platforms
 #define MDNS_STATIC_CONST_CHAR(name, value) static const char name[] PROGMEM = value
-// Helper to get string from PROGMEM - returns a temporary std::string
+// Helper to convert PROGMEM string to std::string for TemplatableValue
 // Only define this function if we have services that will use it
 #if defined(USE_API) || defined(USE_PROMETHEUS) || defined(USE_WEBSERVER) || defined(USE_MDNS_EXTRA_SERVICES)
-static std::string mdns_string_p(const char *src) {
+static std::string mdns_str_value(PGM_P str) {
   char buf[64];
-  strncpy_P(buf, src, sizeof(buf) - 1);
+  strncpy_P(buf, str, sizeof(buf) - 1);
   buf[sizeof(buf) - 1] = '\0';
   return std::string(buf);
 }
-#define MDNS_STR(name) mdns_string_p(name)
-#else
-// If no services are configured, we still need the fallback service but it uses string literals
-#define MDNS_STR(name) std::string(name)
+#define MDNS_STR_VALUE(name) mdns_str_value(name)
 #endif
 #else
 // On non-ESP8266 platforms, use regular const char*
-#define MDNS_STATIC_CONST_CHAR(name, value) static constexpr const char *name = value
-#define MDNS_STR(name) name
+#define MDNS_STATIC_CONST_CHAR(name, value) static constexpr const char name[] = value
+#define MDNS_STR_VALUE(name) std::string(name)
 #endif
 
 #ifdef USE_API
@@ -118,31 +115,31 @@ void MDNSComponent::compile_records_() {
     txt_records.push_back({MDNS_STR(TXT_MAC), get_mac_address()});
 
 #ifdef USE_ESP8266
-    txt_records.push_back({MDNS_STR(TXT_PLATFORM), MDNS_STR(PLATFORM_ESP8266)});
+    txt_records.push_back({MDNS_STR(TXT_PLATFORM), MDNS_STR_VALUE(PLATFORM_ESP8266)});
 #elif defined(USE_ESP32)
-    txt_records.push_back({MDNS_STR(TXT_PLATFORM), MDNS_STR(PLATFORM_ESP32)});
+    txt_records.push_back({MDNS_STR(TXT_PLATFORM), MDNS_STR_VALUE(PLATFORM_ESP32)});
 #elif defined(USE_RP2040)
-    txt_records.push_back({MDNS_STR(TXT_PLATFORM), MDNS_STR(PLATFORM_RP2040)});
+    txt_records.push_back({MDNS_STR(TXT_PLATFORM), MDNS_STR_VALUE(PLATFORM_RP2040)});
 #elif defined(USE_LIBRETINY)
-    txt_records.emplace_back(MDNSTXTRecord{"platform", lt_cpu_get_model_name()});
+    txt_records.push_back({MDNS_STR(TXT_PLATFORM), lt_cpu_get_model_name()});
 #endif
 
     txt_records.push_back({MDNS_STR(TXT_BOARD), ESPHOME_BOARD});
 
 #if defined(USE_WIFI)
-    txt_records.push_back({MDNS_STR(TXT_NETWORK), MDNS_STR(NETWORK_WIFI)});
+    txt_records.push_back({MDNS_STR(TXT_NETWORK), MDNS_STR_VALUE(NETWORK_WIFI)});
 #elif defined(USE_ETHERNET)
-    txt_records.push_back({MDNS_STR(TXT_NETWORK), MDNS_STR(NETWORK_ETHERNET)});
+    txt_records.push_back({MDNS_STR(TXT_NETWORK), MDNS_STR_VALUE(NETWORK_ETHERNET)});
 #elif defined(USE_OPENTHREAD)
-    txt_records.push_back({MDNS_STR(TXT_NETWORK), MDNS_STR(NETWORK_THREAD)});
+    txt_records.push_back({MDNS_STR(TXT_NETWORK), MDNS_STR_VALUE(NETWORK_THREAD)});
 #endif
 
 #ifdef USE_API_NOISE
     MDNS_STATIC_CONST_CHAR(NOISE_ENCRYPTION, "Noise_NNpsk0_25519_ChaChaPoly_SHA256");
     if (api::global_api_server->get_noise_ctx()->has_psk()) {
-      txt_records.push_back({MDNS_STR(TXT_API_ENCRYPTION), MDNS_STR(NOISE_ENCRYPTION)});
+      txt_records.push_back({MDNS_STR(TXT_API_ENCRYPTION), MDNS_STR_VALUE(NOISE_ENCRYPTION)});
     } else {
-      txt_records.push_back({MDNS_STR(TXT_API_ENCRYPTION_SUPPORTED), MDNS_STR(NOISE_ENCRYPTION)});
+      txt_records.push_back({MDNS_STR(TXT_API_ENCRYPTION_SUPPORTED), MDNS_STR_VALUE(NOISE_ENCRYPTION)});
     }
 #endif
 
@@ -175,10 +172,10 @@ void MDNSComponent::compile_records_() {
   // Publish "http" service if not using native API or any other services
   // This is just to have *some* mDNS service so that .local resolution works
   auto &fallback_service = this->services_.emplace_next();
-  fallback_service.service_type = "_http";
-  fallback_service.proto = "_tcp";
+  fallback_service.service_type = MDNS_STR(SERVICE_HTTP);
+  fallback_service.proto = MDNS_STR(SERVICE_TCP);
   fallback_service.port = USE_WEBSERVER_PORT;
-  fallback_service.txt_records.emplace_back(MDNSTXTRecord{"version", ESPHOME_VERSION});
+  fallback_service.txt_records.push_back({MDNS_STR(TXT_VERSION), ESPHOME_VERSION});
 #endif
 }
 
@@ -190,10 +187,10 @@ void MDNSComponent::dump_config() {
 #if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_VERBOSE
   ESP_LOGV(TAG, "  Services:");
   for (const auto &service : this->services_) {
-    ESP_LOGV(TAG, "  - %s, %s, %d", service.service_type.c_str(), service.proto.c_str(),
+    ESP_LOGV(TAG, "  - %s, %s, %d", MDNS_STR_ARG(service.service_type), MDNS_STR_ARG(service.proto),
              const_cast<TemplatableValue<uint16_t> &>(service.port).value());
     for (const auto &record : service.txt_records) {
-      ESP_LOGV(TAG, "    TXT: %s = %s", record.key.c_str(),
+      ESP_LOGV(TAG, "    TXT: %s = %s", MDNS_STR_ARG(record.key),
                const_cast<TemplatableValue<std::string> &>(record.value).value().c_str());
     }
   }
diff --git a/esphome/components/mdns/mdns_component.h b/esphome/components/mdns/mdns_component.h
index e0e268c914..b1f73fbb32 100644
--- a/esphome/components/mdns/mdns_component.h
+++ b/esphome/components/mdns/mdns_component.h
@@ -9,21 +9,34 @@
 namespace esphome {
 namespace mdns {
 
+// Helper struct that identifies strings that may be stored in flash storage (similar to LogString)
+struct MDNSString;
+
+// Macro to cast string literals to MDNSString* (works on all platforms)
+#define MDNS_STR(name) (reinterpret_cast<const esphome::mdns::MDNSString *>(name))
+
+#ifdef USE_ESP8266
+#include <pgmspace.h>
+#define MDNS_STR_ARG(s) ((PGM_P) (s))
+#else
+#define MDNS_STR_ARG(s) (reinterpret_cast<const char *>(s))
+#endif
+
 // Service count is calculated at compile time by Python codegen
 // MDNS_SERVICE_COUNT will always be defined
 
 struct MDNSTXTRecord {
-  std::string key;
+  const MDNSString *key;
   TemplatableValue<std::string> value;
 };
 
 struct MDNSService {
   // service name _including_ underscore character prefix
   // as defined in RFC6763 Section 7
-  std::string service_type;
+  const MDNSString *service_type;
   // second label indicating protocol _including_ underscore character prefix
   // as defined in RFC6763 Section 7, like "_tcp" or "_udp"
-  std::string proto;
+  const MDNSString *proto;
   TemplatableValue<uint16_t> port;
   std::vector<MDNSTXTRecord> txt_records;
 };
diff --git a/esphome/components/mdns/mdns_esp32.cpp b/esphome/components/mdns/mdns_esp32.cpp
index ffd86afec1..40d305a1e6 100644
--- a/esphome/components/mdns/mdns_esp32.cpp
+++ b/esphome/components/mdns/mdns_esp32.cpp
@@ -29,23 +29,23 @@ void MDNSComponent::setup() {
     std::vector<mdns_txt_item_t> txt_records;
     for (const auto &record : service.txt_records) {
       mdns_txt_item_t it{};
-      // dup strings to ensure the pointer is valid even after the record loop
-      it.key = strdup(record.key.c_str());
+      // key is a compile-time string literal in flash, no need to strdup
+      it.key = MDNS_STR_ARG(record.key);
+      // value is a temporary from TemplatableValue, must strdup to keep it alive
       it.value = strdup(const_cast<TemplatableValue<std::string> &>(record.value).value().c_str());
       txt_records.push_back(it);
     }
     uint16_t port = const_cast<TemplatableValue<uint16_t> &>(service.port).value();
-    err = mdns_service_add(nullptr, service.service_type.c_str(), service.proto.c_str(), port, txt_records.data(),
-                           txt_records.size());
+    err = mdns_service_add(nullptr, MDNS_STR_ARG(service.service_type), MDNS_STR_ARG(service.proto), port,
+                           txt_records.data(), txt_records.size());
 
     // free records
     for (const auto &it : txt_records) {
-      delete it.key;    // NOLINT(cppcoreguidelines-owning-memory)
-      delete it.value;  // NOLINT(cppcoreguidelines-owning-memory)
+      free((void *) it.value);  // NOLINT(cppcoreguidelines-no-malloc)
     }
 
     if (err != ESP_OK) {
-      ESP_LOGW(TAG, "Failed to register service %s: %s", service.service_type.c_str(), esp_err_to_name(err));
+      ESP_LOGW(TAG, "Failed to register service %s: %s", MDNS_STR_ARG(service.service_type), esp_err_to_name(err));
     }
   }
 }
diff --git a/esphome/components/mdns/mdns_esp8266.cpp b/esphome/components/mdns/mdns_esp8266.cpp
index 2c90d57021..f1c8909807 100644
--- a/esphome/components/mdns/mdns_esp8266.cpp
+++ b/esphome/components/mdns/mdns_esp8266.cpp
@@ -21,18 +21,18 @@ void MDNSComponent::setup() {
     // part of the wire protocol to have an underscore, and for example ESP-IDF
     // expects the underscore to be there, the ESP8266 implementation always adds
     // the underscore itself.
-    auto *proto = service.proto.c_str();
-    while (*proto == '_') {
+    auto *proto = MDNS_STR_ARG(service.proto);
+    while (progmem_read_byte((const uint8_t *) proto) == '_') {
       proto++;
     }
-    auto *service_type = service.service_type.c_str();
-    while (*service_type == '_') {
+    auto *service_type = MDNS_STR_ARG(service.service_type);
+    while (progmem_read_byte((const uint8_t *) service_type) == '_') {
       service_type++;
     }
     uint16_t port = const_cast<TemplatableValue<uint16_t> &>(service.port).value();
-    MDNS.addService(service_type, proto, port);
+    MDNS.addService(FPSTR(service_type), FPSTR(proto), port);
     for (const auto &record : service.txt_records) {
-      MDNS.addServiceTxt(service_type, proto, record.key.c_str(),
+      MDNS.addServiceTxt(FPSTR(service_type), FPSTR(proto), FPSTR(MDNS_STR_ARG(record.key)),
                          const_cast<TemplatableValue<std::string> &>(record.value).value().c_str());
     }
   }
diff --git a/esphome/components/mdns/mdns_libretiny.cpp b/esphome/components/mdns/mdns_libretiny.cpp
index 7a41ec9dce..9010ca2bc6 100644
--- a/esphome/components/mdns/mdns_libretiny.cpp
+++ b/esphome/components/mdns/mdns_libretiny.cpp
@@ -21,18 +21,18 @@ void MDNSComponent::setup() {
     // part of the wire protocol to have an underscore, and for example ESP-IDF
     // expects the underscore to be there, the ESP8266 implementation always adds
     // the underscore itself.
-    auto *proto = service.proto.c_str();
+    auto *proto = MDNS_STR_ARG(service.proto);
     while (*proto == '_') {
       proto++;
     }
-    auto *service_type = service.service_type.c_str();
+    auto *service_type = MDNS_STR_ARG(service.service_type);
     while (*service_type == '_') {
       service_type++;
     }
     uint16_t port_ = const_cast<TemplatableValue<uint16_t> &>(service.port).value();
     MDNS.addService(service_type, proto, port_);
     for (const auto &record : service.txt_records) {
-      MDNS.addServiceTxt(service_type, proto, record.key.c_str(),
+      MDNS.addServiceTxt(service_type, proto, MDNS_STR_ARG(record.key),
                          const_cast<TemplatableValue<std::string> &>(record.value).value().c_str());
     }
   }
diff --git a/esphome/components/mdns/mdns_rp2040.cpp b/esphome/components/mdns/mdns_rp2040.cpp
index 95894323f4..039453f501 100644
--- a/esphome/components/mdns/mdns_rp2040.cpp
+++ b/esphome/components/mdns/mdns_rp2040.cpp
@@ -21,18 +21,18 @@ void MDNSComponent::setup() {
     // part of the wire protocol to have an underscore, and for example ESP-IDF
     // expects the underscore to be there, the ESP8266 implementation always adds
     // the underscore itself.
-    auto *proto = service.proto.c_str();
+    auto *proto = MDNS_STR_ARG(service.proto);
     while (*proto == '_') {
       proto++;
     }
-    auto *service_type = service.service_type.c_str();
+    auto *service_type = MDNS_STR_ARG(service.service_type);
     while (*service_type == '_') {
       service_type++;
     }
     uint16_t port = const_cast<TemplatableValue<uint16_t> &>(service.port).value();
     MDNS.addService(service_type, proto, port);
     for (const auto &record : service.txt_records) {
-      MDNS.addServiceTxt(service_type, proto, record.key.c_str(),
+      MDNS.addServiceTxt(service_type, proto, MDNS_STR_ARG(record.key),
                          const_cast<TemplatableValue<std::string> &>(record.value).value().c_str());
     }
   }
diff --git a/esphome/components/openthread/openthread.cpp b/esphome/components/openthread/openthread.cpp
index 57b972d195..bc5dcadef6 100644
--- a/esphome/components/openthread/openthread.cpp
+++ b/esphome/components/openthread/openthread.cpp
@@ -155,7 +155,7 @@ void OpenThreadSrpComponent::setup() {
 
     // Set service name
     char *string = otSrpClientBuffersGetServiceEntryServiceNameString(entry, &size);
-    std::string full_service = service.service_type + "." + service.proto;
+    std::string full_service = std::string(MDNS_STR_ARG(service.service_type)) + "." + MDNS_STR_ARG(service.proto);
     if (full_service.size() > size) {
       ESP_LOGW(TAG, "Service name too long: %s", full_service.c_str());
       continue;
@@ -181,7 +181,7 @@ void OpenThreadSrpComponent::setup() {
     for (size_t i = 0; i < service.txt_records.size(); i++) {
       const auto &txt = service.txt_records[i];
       auto value = const_cast<TemplatableValue<std::string> &>(txt.value).value();
-      txt_entries[i].mKey = strdup(txt.key.c_str());
+      txt_entries[i].mKey = MDNS_STR_ARG(txt.key);
       txt_entries[i].mValue = reinterpret_cast<const uint8_t *>(strdup(value.c_str()));
       txt_entries[i].mValueLength = value.size();
     }

From 55888b9beeb006c40eee6a6cda80e1bb4545a371 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Tue, 7 Oct 2025 21:19:35 -1000
Subject: [PATCH 06/14] store mdns values in flash

---
 esphome/components/mdns/__init__.py           | 65 +++++++++++++++----
 esphome/components/mdns/mdns_component.cpp    | 50 ++++++--------
 esphome/components/mdns/mdns_component.h      | 10 ++-
 esphome/components/mdns/mdns_esp32.cpp        |  6 +-
 esphome/components/mdns/mdns_esp8266.cpp      |  2 +-
 esphome/components/mdns/mdns_libretiny.cpp    |  3 +-
 esphome/components/mdns/mdns_rp2040.cpp       |  3 +-
 esphome/core/helpers.h                        |  3 +
 .../mdns/test-comprehensive.esp8266-ard.yaml  |  3 +
 9 files changed, 94 insertions(+), 51 deletions(-)

diff --git a/esphome/components/mdns/__init__.py b/esphome/components/mdns/__init__.py
index 3fa4d2ebef..61fc1e196a 100644
--- a/esphome/components/mdns/__init__.py
+++ b/esphome/components/mdns/__init__.py
@@ -58,11 +58,21 @@ CONFIG_SCHEMA = cv.All(
 )
 
 
-def mdns_txt_record(key: str, value: str):
+def mdns_txt_record_static(key: str, value: str):
+    """Create a TXT record with a static (compile-time) value stored in flash."""
     return cg.StructInitializer(
         MDNSTXTRecord,
         ("key", cg.RawExpression(f"MDNS_STR({cg.safe_exp(key)})")),
-        ("value", value),
+        ("value", cg.RawExpression(f"MDNS_STR({cg.safe_exp(value)})")),
+    )
+
+
+def mdns_txt_record_dynamic(key: str, value_expr: str):
+    """Create a TXT record with a dynamic value (will be evaluated and stored in vector)."""
+    return cg.StructInitializer(
+        MDNSTXTRecord,
+        ("key", cg.RawExpression(f"MDNS_STR({cg.safe_exp(key)})")),
+        ("value", cg.RawExpression(f"MDNS_STR({value_expr})")),
     )
 
 
@@ -107,23 +117,56 @@ async def to_code(config):
     # Ensure at least 1 service (fallback service)
     cg.add_define("MDNS_SERVICE_COUNT", max(1, service_count))
 
+    # Calculate compile-time dynamic TXT value count
+    # Dynamic values are those that cannot be stored in flash at compile time
+    dynamic_txt_count = 0
+    if "api" in CORE.config:
+        # Always: get_mac_address()
+        dynamic_txt_count += 1
+        # Conditional: friendly_name (if not empty, but we conservatively count it)
+        dynamic_txt_count += 1
+        # Conditional: dashboard_import_url
+        if "dashboard_import" in CORE.config:
+            dynamic_txt_count += 1
+    # User-provided templatable TXT values (only lambdas, not static strings)
+    dynamic_txt_count += sum(
+        1
+        for service in config[CONF_SERVICES]
+        for txt_value in service[CONF_TXT].values()
+        if cg.is_template(txt_value)
+    )
+
+    # Ensure at least 1 to avoid zero-size array
+    cg.add_define("MDNS_DYNAMIC_TXT_COUNT", max(1, dynamic_txt_count))
+
     var = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(var, config)
 
     for service in config[CONF_SERVICES]:
-        txt = [
-            cg.StructInitializer(
-                MDNSTXTRecord,
-                ("key", cg.RawExpression(f"MDNS_STR({cg.safe_exp(txt_key)})")),
-                ("value", await cg.templatable(txt_value, [], cg.std_string)),
-            )
-            for txt_key, txt_value in service[CONF_TXT].items()
-        ]
+        # Build the txt records list for the service
+        txt_records = []
+        for txt_key, txt_value in service[CONF_TXT].items():
+            if cg.is_template(txt_value):
+                # It's a lambda - evaluate and store using helper
+                templated_value = await cg.templatable(txt_value, [], cg.std_string)
+                txt_records.append(
+                    cg.RawExpression(
+                        f"{{MDNS_STR({cg.safe_exp(txt_key)}), MDNS_STR({var}->add_dynamic_txt_value(({templated_value})()))}}"
+                    )
+                )
+            else:
+                # It's a static string - use directly in flash, no need to store in vector
+                txt_records.append(
+                    cg.RawExpression(
+                        f"{{MDNS_STR({cg.safe_exp(txt_key)}), MDNS_STR({cg.safe_exp(txt_value)})}}"
+                    )
+                )
+
         exp = mdns_service(
             service[CONF_SERVICE],
             service[CONF_PROTOCOL],
             await cg.templatable(service[CONF_PORT], [], cg.uint16),
-            txt,
+            txt_records,
         )
 
         cg.add(var.add_extra_service(exp))
diff --git a/esphome/components/mdns/mdns_component.cpp b/esphome/components/mdns/mdns_component.cpp
index 8945053b7d..15310815fb 100644
--- a/esphome/components/mdns/mdns_component.cpp
+++ b/esphome/components/mdns/mdns_component.cpp
@@ -9,21 +9,9 @@
 #include <pgmspace.h>
 // Macro to define strings in PROGMEM on ESP8266, regular memory on other platforms
 #define MDNS_STATIC_CONST_CHAR(name, value) static const char name[] PROGMEM = value
-// Helper to convert PROGMEM string to std::string for TemplatableValue
-// Only define this function if we have services that will use it
-#if defined(USE_API) || defined(USE_PROMETHEUS) || defined(USE_WEBSERVER) || defined(USE_MDNS_EXTRA_SERVICES)
-static std::string mdns_str_value(PGM_P str) {
-  char buf[64];
-  strncpy_P(buf, str, sizeof(buf) - 1);
-  buf[sizeof(buf) - 1] = '\0';
-  return std::string(buf);
-}
-#define MDNS_STR_VALUE(name) mdns_str_value(name)
-#endif
 #else
 // On non-ESP8266 platforms, use regular const char*
 #define MDNS_STATIC_CONST_CHAR(name, value) static constexpr const char name[] = value
-#define MDNS_STR_VALUE(name) std::string(name)
 #endif
 
 #ifdef USE_API
@@ -109,47 +97,48 @@ void MDNSComponent::compile_records_() {
     txt_records.reserve(txt_count);
 
     if (!friendly_name_empty) {
-      txt_records.push_back({MDNS_STR(TXT_FRIENDLY_NAME), friendly_name});
+      txt_records.push_back({MDNS_STR(TXT_FRIENDLY_NAME), MDNS_STR(this->add_dynamic_txt_value(friendly_name))});
     }
-    txt_records.push_back({MDNS_STR(TXT_VERSION), ESPHOME_VERSION});
-    txt_records.push_back({MDNS_STR(TXT_MAC), get_mac_address()});
+    txt_records.push_back({MDNS_STR(TXT_VERSION), MDNS_STR(ESPHOME_VERSION)});
+    txt_records.push_back({MDNS_STR(TXT_MAC), MDNS_STR(this->add_dynamic_txt_value(get_mac_address()))});
 
 #ifdef USE_ESP8266
-    txt_records.push_back({MDNS_STR(TXT_PLATFORM), MDNS_STR_VALUE(PLATFORM_ESP8266)});
+    txt_records.push_back({MDNS_STR(TXT_PLATFORM), MDNS_STR(PLATFORM_ESP8266)});
 #elif defined(USE_ESP32)
-    txt_records.push_back({MDNS_STR(TXT_PLATFORM), MDNS_STR_VALUE(PLATFORM_ESP32)});
+    txt_records.push_back({MDNS_STR(TXT_PLATFORM), MDNS_STR(PLATFORM_ESP32)});
 #elif defined(USE_RP2040)
-    txt_records.push_back({MDNS_STR(TXT_PLATFORM), MDNS_STR_VALUE(PLATFORM_RP2040)});
+    txt_records.push_back({MDNS_STR(TXT_PLATFORM), MDNS_STR(PLATFORM_RP2040)});
 #elif defined(USE_LIBRETINY)
-    txt_records.push_back({MDNS_STR(TXT_PLATFORM), lt_cpu_get_model_name()});
+    txt_records.push_back({MDNS_STR(TXT_PLATFORM), MDNS_STR(lt_cpu_get_model_name())});
 #endif
 
-    txt_records.push_back({MDNS_STR(TXT_BOARD), ESPHOME_BOARD});
+    txt_records.push_back({MDNS_STR(TXT_BOARD), MDNS_STR(ESPHOME_BOARD)});
 
 #if defined(USE_WIFI)
-    txt_records.push_back({MDNS_STR(TXT_NETWORK), MDNS_STR_VALUE(NETWORK_WIFI)});
+    txt_records.push_back({MDNS_STR(TXT_NETWORK), MDNS_STR(NETWORK_WIFI)});
 #elif defined(USE_ETHERNET)
-    txt_records.push_back({MDNS_STR(TXT_NETWORK), MDNS_STR_VALUE(NETWORK_ETHERNET)});
+    txt_records.push_back({MDNS_STR(TXT_NETWORK), MDNS_STR(NETWORK_ETHERNET)});
 #elif defined(USE_OPENTHREAD)
-    txt_records.push_back({MDNS_STR(TXT_NETWORK), MDNS_STR_VALUE(NETWORK_THREAD)});
+    txt_records.push_back({MDNS_STR(TXT_NETWORK), MDNS_STR(NETWORK_THREAD)});
 #endif
 
 #ifdef USE_API_NOISE
     MDNS_STATIC_CONST_CHAR(NOISE_ENCRYPTION, "Noise_NNpsk0_25519_ChaChaPoly_SHA256");
     if (api::global_api_server->get_noise_ctx()->has_psk()) {
-      txt_records.push_back({MDNS_STR(TXT_API_ENCRYPTION), MDNS_STR_VALUE(NOISE_ENCRYPTION)});
+      txt_records.push_back({MDNS_STR(TXT_API_ENCRYPTION), MDNS_STR(NOISE_ENCRYPTION)});
     } else {
-      txt_records.push_back({MDNS_STR(TXT_API_ENCRYPTION_SUPPORTED), MDNS_STR_VALUE(NOISE_ENCRYPTION)});
+      txt_records.push_back({MDNS_STR(TXT_API_ENCRYPTION_SUPPORTED), MDNS_STR(NOISE_ENCRYPTION)});
     }
 #endif
 
 #ifdef ESPHOME_PROJECT_NAME
-    txt_records.push_back({MDNS_STR(TXT_PROJECT_NAME), ESPHOME_PROJECT_NAME});
-    txt_records.push_back({MDNS_STR(TXT_PROJECT_VERSION), ESPHOME_PROJECT_VERSION});
+    txt_records.push_back({MDNS_STR(TXT_PROJECT_NAME), MDNS_STR(ESPHOME_PROJECT_NAME)});
+    txt_records.push_back({MDNS_STR(TXT_PROJECT_VERSION), MDNS_STR(ESPHOME_PROJECT_VERSION)});
 #endif  // ESPHOME_PROJECT_NAME
 
 #ifdef USE_DASHBOARD_IMPORT
-    txt_records.push_back({MDNS_STR(TXT_PACKAGE_IMPORT_URL), dashboard_import::get_package_import_url()});
+    txt_records.push_back({MDNS_STR(TXT_PACKAGE_IMPORT_URL),
+                           MDNS_STR(this->add_dynamic_txt_value(dashboard_import::get_package_import_url()))});
 #endif
   }
 #endif  // USE_API
@@ -175,7 +164,7 @@ void MDNSComponent::compile_records_() {
   fallback_service.service_type = MDNS_STR(SERVICE_HTTP);
   fallback_service.proto = MDNS_STR(SERVICE_TCP);
   fallback_service.port = USE_WEBSERVER_PORT;
-  fallback_service.txt_records.push_back({MDNS_STR(TXT_VERSION), ESPHOME_VERSION});
+  fallback_service.txt_records.push_back({MDNS_STR(TXT_VERSION), MDNS_STR(ESPHOME_VERSION)});
 #endif
 }
 
@@ -190,8 +179,7 @@ void MDNSComponent::dump_config() {
     ESP_LOGV(TAG, "  - %s, %s, %d", MDNS_STR_ARG(service.service_type), MDNS_STR_ARG(service.proto),
              const_cast<TemplatableValue<uint16_t> &>(service.port).value());
     for (const auto &record : service.txt_records) {
-      ESP_LOGV(TAG, "    TXT: %s = %s", MDNS_STR_ARG(record.key),
-               const_cast<TemplatableValue<std::string> &>(record.value).value().c_str());
+      ESP_LOGV(TAG, "    TXT: %s = %s", MDNS_STR_ARG(record.key), MDNS_STR_ARG(record.value));
     }
   }
 #endif
diff --git a/esphome/components/mdns/mdns_component.h b/esphome/components/mdns/mdns_component.h
index b1f73fbb32..a3684f6f5e 100644
--- a/esphome/components/mdns/mdns_component.h
+++ b/esphome/components/mdns/mdns_component.h
@@ -27,7 +27,7 @@ struct MDNSString;
 
 struct MDNSTXTRecord {
   const MDNSString *key;
-  TemplatableValue<std::string> value;
+  const MDNSString *value;
 };
 
 struct MDNSService {
@@ -59,6 +59,14 @@ class MDNSComponent : public Component {
 
   void on_shutdown() override;
 
+  /// Add a dynamic TXT value and return pointer to it for use in MDNSTXTRecord
+  const char *add_dynamic_txt_value(const std::string &value) {
+    this->dynamic_txt_values_.push_back(value);
+    return this->dynamic_txt_values_.back().c_str();
+  }
+
+  StaticVector<std::string, MDNS_DYNAMIC_TXT_COUNT> dynamic_txt_values_;
+
  protected:
   StaticVector<MDNSService, MDNS_SERVICE_COUNT> services_{};
   std::string hostname_;
diff --git a/esphome/components/mdns/mdns_esp32.cpp b/esphome/components/mdns/mdns_esp32.cpp
index 40d305a1e6..223eeb8e8c 100644
--- a/esphome/components/mdns/mdns_esp32.cpp
+++ b/esphome/components/mdns/mdns_esp32.cpp
@@ -29,10 +29,10 @@ void MDNSComponent::setup() {
     std::vector<mdns_txt_item_t> txt_records;
     for (const auto &record : service.txt_records) {
       mdns_txt_item_t it{};
-      // key is a compile-time string literal in flash, no need to strdup
+      // key and value are either compile-time string literals in flash or pointers to dynamic_txt_values_
+      // ESP-IDF requires strdup for both to keep them alive during mdns operation
       it.key = MDNS_STR_ARG(record.key);
-      // value is a temporary from TemplatableValue, must strdup to keep it alive
-      it.value = strdup(const_cast<TemplatableValue<std::string> &>(record.value).value().c_str());
+      it.value = strdup(MDNS_STR_ARG(record.value));
       txt_records.push_back(it);
     }
     uint16_t port = const_cast<TemplatableValue<uint16_t> &>(service.port).value();
diff --git a/esphome/components/mdns/mdns_esp8266.cpp b/esphome/components/mdns/mdns_esp8266.cpp
index f1c8909807..f3779042ed 100644
--- a/esphome/components/mdns/mdns_esp8266.cpp
+++ b/esphome/components/mdns/mdns_esp8266.cpp
@@ -33,7 +33,7 @@ void MDNSComponent::setup() {
     MDNS.addService(FPSTR(service_type), FPSTR(proto), port);
     for (const auto &record : service.txt_records) {
       MDNS.addServiceTxt(FPSTR(service_type), FPSTR(proto), FPSTR(MDNS_STR_ARG(record.key)),
-                         const_cast<TemplatableValue<std::string> &>(record.value).value().c_str());
+                         FPSTR(MDNS_STR_ARG(record.value)));
     }
   }
 }
diff --git a/esphome/components/mdns/mdns_libretiny.cpp b/esphome/components/mdns/mdns_libretiny.cpp
index 9010ca2bc6..5540bf361a 100644
--- a/esphome/components/mdns/mdns_libretiny.cpp
+++ b/esphome/components/mdns/mdns_libretiny.cpp
@@ -32,8 +32,7 @@ void MDNSComponent::setup() {
     uint16_t port_ = const_cast<TemplatableValue<uint16_t> &>(service.port).value();
     MDNS.addService(service_type, proto, port_);
     for (const auto &record : service.txt_records) {
-      MDNS.addServiceTxt(service_type, proto, MDNS_STR_ARG(record.key),
-                         const_cast<TemplatableValue<std::string> &>(record.value).value().c_str());
+      MDNS.addServiceTxt(service_type, proto, MDNS_STR_ARG(record.key), MDNS_STR_ARG(record.value));
     }
   }
 }
diff --git a/esphome/components/mdns/mdns_rp2040.cpp b/esphome/components/mdns/mdns_rp2040.cpp
index 039453f501..5ad006f5d4 100644
--- a/esphome/components/mdns/mdns_rp2040.cpp
+++ b/esphome/components/mdns/mdns_rp2040.cpp
@@ -32,8 +32,7 @@ void MDNSComponent::setup() {
     uint16_t port = const_cast<TemplatableValue<uint16_t> &>(service.port).value();
     MDNS.addService(service_type, proto, port);
     for (const auto &record : service.txt_records) {
-      MDNS.addServiceTxt(service_type, proto, MDNS_STR_ARG(record.key),
-                         const_cast<TemplatableValue<std::string> &>(record.value).value().c_str());
+      MDNS.addServiceTxt(service_type, proto, MDNS_STR_ARG(record.key), MDNS_STR_ARG(record.value));
     }
   }
 }
diff --git a/esphome/core/helpers.h b/esphome/core/helpers.h
index e06f2d15ef..fe89f0b24f 100644
--- a/esphome/core/helpers.h
+++ b/esphome/core/helpers.h
@@ -146,6 +146,9 @@ template<typename T, size_t N> class StaticVector {
   T &operator[](size_t i) { return data_[i]; }
   const T &operator[](size_t i) const { return data_[i]; }
 
+  T &back() { return data_[count_ - 1]; }
+  const T &back() const { return data_[count_ - 1]; }
+
   // For range-based for loops
   iterator begin() { return data_.begin(); }
   iterator end() { return data_.begin() + count_; }
diff --git a/tests/components/mdns/test-comprehensive.esp8266-ard.yaml b/tests/components/mdns/test-comprehensive.esp8266-ard.yaml
index 02767833a3..3129ca3143 100644
--- a/tests/components/mdns/test-comprehensive.esp8266-ard.yaml
+++ b/tests/components/mdns/test-comprehensive.esp8266-ard.yaml
@@ -25,6 +25,9 @@ mdns:
     - service: _http
       protocol: _tcp
       port: 80
+      txt:
+        version: "1.0"
+        path: "/"
 
 # OTA should run at priority 54 (after mdns)
 ota:

From 52f2826d38db2c63fe15092975821ceb8ba23636 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Tue, 7 Oct 2025 21:21:22 -1000
Subject: [PATCH 07/14] preen

---
 esphome/components/mdns/__init__.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/esphome/components/mdns/__init__.py b/esphome/components/mdns/__init__.py
index 61fc1e196a..3054b76d67 100644
--- a/esphome/components/mdns/__init__.py
+++ b/esphome/components/mdns/__init__.py
@@ -123,8 +123,9 @@ async def to_code(config):
     if "api" in CORE.config:
         # Always: get_mac_address()
         dynamic_txt_count += 1
-        # Conditional: friendly_name (if not empty, but we conservatively count it)
-        dynamic_txt_count += 1
+        # Conditional: friendly_name (if not empty)
+        if CORE.friendly_name:
+            dynamic_txt_count += 1
         # Conditional: dashboard_import_url
         if "dashboard_import" in CORE.config:
             dynamic_txt_count += 1

From ac7bd4137fafc89034c929110a8089559f6e1642 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Tue, 7 Oct 2025 21:22:34 -1000
Subject: [PATCH 08/14] preen

---
 esphome/components/mdns/__init__.py        | 3 ---
 esphome/components/mdns/mdns_component.cpp | 2 +-
 2 files changed, 1 insertion(+), 4 deletions(-)

diff --git a/esphome/components/mdns/__init__.py b/esphome/components/mdns/__init__.py
index 3054b76d67..675620f01e 100644
--- a/esphome/components/mdns/__init__.py
+++ b/esphome/components/mdns/__init__.py
@@ -123,9 +123,6 @@ async def to_code(config):
     if "api" in CORE.config:
         # Always: get_mac_address()
         dynamic_txt_count += 1
-        # Conditional: friendly_name (if not empty)
-        if CORE.friendly_name:
-            dynamic_txt_count += 1
         # Conditional: dashboard_import_url
         if "dashboard_import" in CORE.config:
             dynamic_txt_count += 1
diff --git a/esphome/components/mdns/mdns_component.cpp b/esphome/components/mdns/mdns_component.cpp
index 15310815fb..4cab3e50f6 100644
--- a/esphome/components/mdns/mdns_component.cpp
+++ b/esphome/components/mdns/mdns_component.cpp
@@ -97,7 +97,7 @@ void MDNSComponent::compile_records_() {
     txt_records.reserve(txt_count);
 
     if (!friendly_name_empty) {
-      txt_records.push_back({MDNS_STR(TXT_FRIENDLY_NAME), MDNS_STR(this->add_dynamic_txt_value(friendly_name))});
+      txt_records.push_back({MDNS_STR(TXT_FRIENDLY_NAME), MDNS_STR(friendly_name.c_str())});
     }
     txt_records.push_back({MDNS_STR(TXT_VERSION), MDNS_STR(ESPHOME_VERSION)});
     txt_records.push_back({MDNS_STR(TXT_MAC), MDNS_STR(this->add_dynamic_txt_value(get_mac_address()))});

From 1476dcf5c83bde231341dc9983afb8b019a2bea9 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Tue, 7 Oct 2025 21:24:10 -1000
Subject: [PATCH 09/14] preen

---
 esphome/components/dashboard_import/dashboard_import.cpp | 2 +-
 esphome/components/dashboard_import/dashboard_import.h   | 2 +-
 esphome/components/mdns/__init__.py                      | 3 ---
 esphome/components/mdns/mdns_component.cpp               | 4 ++--
 4 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/esphome/components/dashboard_import/dashboard_import.cpp b/esphome/components/dashboard_import/dashboard_import.cpp
index 6875fd61a5..c04696fd53 100644
--- a/esphome/components/dashboard_import/dashboard_import.cpp
+++ b/esphome/components/dashboard_import/dashboard_import.cpp
@@ -5,7 +5,7 @@ namespace dashboard_import {
 
 static std::string g_package_import_url;  // NOLINT
 
-std::string get_package_import_url() { return g_package_import_url; }
+const std::string &get_package_import_url() { return g_package_import_url; }
 void set_package_import_url(std::string url) { g_package_import_url = std::move(url); }
 
 }  // namespace dashboard_import
diff --git a/esphome/components/dashboard_import/dashboard_import.h b/esphome/components/dashboard_import/dashboard_import.h
index 0ca2994aab..edcda6b803 100644
--- a/esphome/components/dashboard_import/dashboard_import.h
+++ b/esphome/components/dashboard_import/dashboard_import.h
@@ -5,7 +5,7 @@
 namespace esphome {
 namespace dashboard_import {
 
-std::string get_package_import_url();
+const std::string &get_package_import_url();
 void set_package_import_url(std::string url);
 
 }  // namespace dashboard_import
diff --git a/esphome/components/mdns/__init__.py b/esphome/components/mdns/__init__.py
index 675620f01e..05f909b6fd 100644
--- a/esphome/components/mdns/__init__.py
+++ b/esphome/components/mdns/__init__.py
@@ -123,9 +123,6 @@ async def to_code(config):
     if "api" in CORE.config:
         # Always: get_mac_address()
         dynamic_txt_count += 1
-        # Conditional: dashboard_import_url
-        if "dashboard_import" in CORE.config:
-            dynamic_txt_count += 1
     # User-provided templatable TXT values (only lambdas, not static strings)
     dynamic_txt_count += sum(
         1
diff --git a/esphome/components/mdns/mdns_component.cpp b/esphome/components/mdns/mdns_component.cpp
index 4cab3e50f6..4e33fccec5 100644
--- a/esphome/components/mdns/mdns_component.cpp
+++ b/esphome/components/mdns/mdns_component.cpp
@@ -137,8 +137,8 @@ void MDNSComponent::compile_records_() {
 #endif  // ESPHOME_PROJECT_NAME
 
 #ifdef USE_DASHBOARD_IMPORT
-    txt_records.push_back({MDNS_STR(TXT_PACKAGE_IMPORT_URL),
-                           MDNS_STR(this->add_dynamic_txt_value(dashboard_import::get_package_import_url()))});
+    txt_records.push_back(
+        {MDNS_STR(TXT_PACKAGE_IMPORT_URL), MDNS_STR(dashboard_import::get_package_import_url().c_str())});
 #endif
   }
 #endif  // USE_API

From 6c0a0334a8e9f860ea664606b6aea4dd5af544a4 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Tue, 7 Oct 2025 21:26:56 -1000
Subject: [PATCH 10/14] preen

---
 esphome/components/mdns/mdns_component.cpp | 26 +++++++++++++---------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/esphome/components/mdns/mdns_component.cpp b/esphome/components/mdns/mdns_component.cpp
index 4e33fccec5..d1fc28eee6 100644
--- a/esphome/components/mdns/mdns_component.cpp
+++ b/esphome/components/mdns/mdns_component.cpp
@@ -56,6 +56,14 @@ MDNS_STATIC_CONST_CHAR(NETWORK_WIFI, "wifi");
 MDNS_STATIC_CONST_CHAR(NETWORK_ETHERNET, "ethernet");
 MDNS_STATIC_CONST_CHAR(NETWORK_THREAD, "thread");
 
+// Wrap build-time defines into flash storage
+MDNS_STATIC_CONST_CHAR(VALUE_VERSION, ESPHOME_VERSION);
+MDNS_STATIC_CONST_CHAR(VALUE_BOARD, ESPHOME_BOARD);
+#ifdef ESPHOME_PROJECT_NAME
+MDNS_STATIC_CONST_CHAR(VALUE_PROJECT_NAME, ESPHOME_PROJECT_NAME);
+MDNS_STATIC_CONST_CHAR(VALUE_PROJECT_VERSION, ESPHOME_PROJECT_VERSION);
+#endif
+
 void MDNSComponent::compile_records_() {
   this->hostname_ = App.get_name();
 
@@ -99,7 +107,7 @@ void MDNSComponent::compile_records_() {
     if (!friendly_name_empty) {
       txt_records.push_back({MDNS_STR(TXT_FRIENDLY_NAME), MDNS_STR(friendly_name.c_str())});
     }
-    txt_records.push_back({MDNS_STR(TXT_VERSION), MDNS_STR(ESPHOME_VERSION)});
+    txt_records.push_back({MDNS_STR(TXT_VERSION), MDNS_STR(VALUE_VERSION)});
     txt_records.push_back({MDNS_STR(TXT_MAC), MDNS_STR(this->add_dynamic_txt_value(get_mac_address()))});
 
 #ifdef USE_ESP8266
@@ -112,7 +120,7 @@ void MDNSComponent::compile_records_() {
     txt_records.push_back({MDNS_STR(TXT_PLATFORM), MDNS_STR(lt_cpu_get_model_name())});
 #endif
 
-    txt_records.push_back({MDNS_STR(TXT_BOARD), MDNS_STR(ESPHOME_BOARD)});
+    txt_records.push_back({MDNS_STR(TXT_BOARD), MDNS_STR(VALUE_BOARD)});
 
 #if defined(USE_WIFI)
     txt_records.push_back({MDNS_STR(TXT_NETWORK), MDNS_STR(NETWORK_WIFI)});
@@ -124,16 +132,14 @@ void MDNSComponent::compile_records_() {
 
 #ifdef USE_API_NOISE
     MDNS_STATIC_CONST_CHAR(NOISE_ENCRYPTION, "Noise_NNpsk0_25519_ChaChaPoly_SHA256");
-    if (api::global_api_server->get_noise_ctx()->has_psk()) {
-      txt_records.push_back({MDNS_STR(TXT_API_ENCRYPTION), MDNS_STR(NOISE_ENCRYPTION)});
-    } else {
-      txt_records.push_back({MDNS_STR(TXT_API_ENCRYPTION_SUPPORTED), MDNS_STR(NOISE_ENCRYPTION)});
-    }
+    txt_records.push_back({MDNS_STR(api::global_api_server->get_noise_ctx()->has_psk() ? TXT_API_ENCRYPTION
+                                                                                       : TXT_API_ENCRYPTION_SUPPORTED),
+                           MDNS_STR(NOISE_ENCRYPTION)});
 #endif
 
 #ifdef ESPHOME_PROJECT_NAME
-    txt_records.push_back({MDNS_STR(TXT_PROJECT_NAME), MDNS_STR(ESPHOME_PROJECT_NAME)});
-    txt_records.push_back({MDNS_STR(TXT_PROJECT_VERSION), MDNS_STR(ESPHOME_PROJECT_VERSION)});
+    txt_records.push_back({MDNS_STR(TXT_PROJECT_NAME), MDNS_STR(VALUE_PROJECT_NAME)});
+    txt_records.push_back({MDNS_STR(TXT_PROJECT_VERSION), MDNS_STR(VALUE_PROJECT_VERSION)});
 #endif  // ESPHOME_PROJECT_NAME
 
 #ifdef USE_DASHBOARD_IMPORT
@@ -164,7 +170,7 @@ void MDNSComponent::compile_records_() {
   fallback_service.service_type = MDNS_STR(SERVICE_HTTP);
   fallback_service.proto = MDNS_STR(SERVICE_TCP);
   fallback_service.port = USE_WEBSERVER_PORT;
-  fallback_service.txt_records.push_back({MDNS_STR(TXT_VERSION), MDNS_STR(ESPHOME_VERSION)});
+  fallback_service.txt_records.push_back({MDNS_STR(TXT_VERSION), MDNS_STR(VALUE_VERSION)});
 #endif
 }
 

From 328c1a8469b44f1b04bcee71fdf1fdef00cbc475 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Tue, 7 Oct 2025 21:39:04 -1000
Subject: [PATCH 11/14] goodbye strdup

---
 esphome/components/mdns/mdns_esp32.cpp | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/esphome/components/mdns/mdns_esp32.cpp b/esphome/components/mdns/mdns_esp32.cpp
index 223eeb8e8c..e77c0b9b05 100644
--- a/esphome/components/mdns/mdns_esp32.cpp
+++ b/esphome/components/mdns/mdns_esp32.cpp
@@ -2,7 +2,6 @@
 #if defined(USE_ESP32) && defined(USE_MDNS)
 
 #include <mdns.h>
-#include <cstring>
 #include "esphome/core/hal.h"
 #include "esphome/core/log.h"
 #include "mdns_component.h"
@@ -30,20 +29,15 @@ void MDNSComponent::setup() {
     for (const auto &record : service.txt_records) {
       mdns_txt_item_t it{};
       // key and value are either compile-time string literals in flash or pointers to dynamic_txt_values_
-      // ESP-IDF requires strdup for both to keep them alive during mdns operation
+      // Both remain valid for the lifetime of this function, and ESP-IDF makes internal copies
       it.key = MDNS_STR_ARG(record.key);
-      it.value = strdup(MDNS_STR_ARG(record.value));
+      it.value = MDNS_STR_ARG(record.value);
       txt_records.push_back(it);
     }
     uint16_t port = const_cast<TemplatableValue<uint16_t> &>(service.port).value();
     err = mdns_service_add(nullptr, MDNS_STR_ARG(service.service_type), MDNS_STR_ARG(service.proto), port,
                            txt_records.data(), txt_records.size());
 
-    // free records
-    for (const auto &it : txt_records) {
-      free((void *) it.value);  // NOLINT(cppcoreguidelines-no-malloc)
-    }
-
     if (err != ESP_OK) {
       ESP_LOGW(TAG, "Failed to register service %s: %s", MDNS_STR_ARG(service.service_type), esp_err_to_name(err));
     }

From d9c3213ef6c319b3444cf86f52f7e2ba507a893c Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Tue, 7 Oct 2025 21:43:35 -1000
Subject: [PATCH 12/14] goodbye strdup

---
 esphome/components/mdns/mdns_component.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/esphome/components/mdns/mdns_component.h b/esphome/components/mdns/mdns_component.h
index a3684f6f5e..241c32079e 100644
--- a/esphome/components/mdns/mdns_component.h
+++ b/esphome/components/mdns/mdns_component.h
@@ -65,6 +65,9 @@ class MDNSComponent : public Component {
     return this->dynamic_txt_values_.back().c_str();
   }
 
+  /// Storage for runtime-generated TXT values (MAC address, user lambdas)
+  /// Pre-sized at compile time via MDNS_DYNAMIC_TXT_COUNT to avoid heap allocations.
+  /// Static/compile-time values (version, board, etc.) are stored directly in flash and don't use this.
   StaticVector<std::string, MDNS_DYNAMIC_TXT_COUNT> dynamic_txt_values_;
 
  protected:

From f5bb79cbc4ab6650135616204802c92b7b602cc1 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Tue, 7 Oct 2025 21:46:08 -1000
Subject: [PATCH 13/14] goodbye strdup

---
 esphome/components/openthread/openthread.cpp | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/esphome/components/openthread/openthread.cpp b/esphome/components/openthread/openthread.cpp
index bc5dcadef6..b2c2519c08 100644
--- a/esphome/components/openthread/openthread.cpp
+++ b/esphome/components/openthread/openthread.cpp
@@ -180,10 +180,12 @@ void OpenThreadSrpComponent::setup() {
     entry->mService.mNumTxtEntries = service.txt_records.size();
     for (size_t i = 0; i < service.txt_records.size(); i++) {
       const auto &txt = service.txt_records[i];
-      auto value = const_cast<TemplatableValue<std::string> &>(txt.value).value();
+      // Value is either a compile-time string literal in flash or a pointer to dynamic_txt_values_
+      // OpenThread SRP client expects the data to persist, so we strdup it
+      const char *value_str = MDNS_STR_ARG(txt.value);
       txt_entries[i].mKey = MDNS_STR_ARG(txt.key);
-      txt_entries[i].mValue = reinterpret_cast<const uint8_t *>(strdup(value.c_str()));
-      txt_entries[i].mValueLength = value.size();
+      txt_entries[i].mValue = reinterpret_cast<const uint8_t *>(strdup(value_str));
+      txt_entries[i].mValueLength = strlen(value_str);
     }
     entry->mService.mTxtEntries = txt_entries;
     entry->mService.mNumTxtEntries = service.txt_records.size();

From 72087bf6baf9149535c72b0b04ef06b45fe2f423 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Tue, 7 Oct 2025 21:48:18 -1000
Subject: [PATCH 14/14] store mdns values in flash

---
 esphome/components/mdns/__init__.py | 18 ------------------
 1 file changed, 18 deletions(-)

diff --git a/esphome/components/mdns/__init__.py b/esphome/components/mdns/__init__.py
index 05f909b6fd..7625b28408 100644
--- a/esphome/components/mdns/__init__.py
+++ b/esphome/components/mdns/__init__.py
@@ -58,24 +58,6 @@ CONFIG_SCHEMA = cv.All(
 )
 
 
-def mdns_txt_record_static(key: str, value: str):
-    """Create a TXT record with a static (compile-time) value stored in flash."""
-    return cg.StructInitializer(
-        MDNSTXTRecord,
-        ("key", cg.RawExpression(f"MDNS_STR({cg.safe_exp(key)})")),
-        ("value", cg.RawExpression(f"MDNS_STR({cg.safe_exp(value)})")),
-    )
-
-
-def mdns_txt_record_dynamic(key: str, value_expr: str):
-    """Create a TXT record with a dynamic value (will be evaluated and stored in vector)."""
-    return cg.StructInitializer(
-        MDNSTXTRecord,
-        ("key", cg.RawExpression(f"MDNS_STR({cg.safe_exp(key)})")),
-        ("value", cg.RawExpression(f"MDNS_STR({value_expr})")),
-    )
-
-
 def mdns_service(
     service: str, proto: str, port: int, txt_records: list[dict[str, str]]
 ):