Merge branch 'dev' into dep_sprintf

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

esphome/__main__.py

@@ -1,5 +1,6 @@
 # PYTHON_ARGCOMPLETE_OK
 import argparse
+from collections.abc import Callable
 from datetime import datetime
 import functools
 import getpass
@@ -936,11 +937,21 @@ def command_dashboard(args: ArgsProtocol) -> int | None:
     return dashboard.start_dashboard(args)
 
 
-def command_update_all(args: ArgsProtocol) -> int | None:
+def run_multiple_configs(
+    files: list, command_builder: Callable[[str], list[str]]
+) -> int:
+    """Run a command for each configuration file in a subprocess.
+
+    Args:
+        files: List of configuration files to process.
+        command_builder: Callable that takes a file path and returns a command list.
+
+    Returns:
+        Number of failed files.
+    """
     import click
 
     success = {}
-    files = list_yaml_files(args.configuration)
     twidth = 60
 
     def print_bar(middle_text):
@@ -950,17 +961,19 @@ def command_update_all(args: ArgsProtocol) -> int | None:
         safe_print(f"{half_line}{middle_text}{half_line}")
 
     for f in files:
-        safe_print(f"Updating {color(AnsiFore.CYAN, str(f))}")
+        f_path = Path(f) if not isinstance(f, Path) else f
+
+        if any(f_path.name == x for x in SECRETS_FILES):
+            _LOGGER.warning("Skipping secrets file %s", f_path)
+            continue
+
+        safe_print(f"Processing {color(AnsiFore.CYAN, str(f))}")
         safe_print("-" * twidth)
         safe_print()
-        if CORE.dashboard:
-            rc = run_external_process(
-                "esphome", "--dashboard", "run", f, "--no-logs", "--device", "OTA"
-            )
-        else:
-            rc = run_external_process(
-                "esphome", "run", f, "--no-logs", "--device", "OTA"
-            )
+
+        cmd = command_builder(f)
+        rc = run_external_process(*cmd)
+
         if rc == 0:
             print_bar(f"[{color(AnsiFore.BOLD_GREEN, 'SUCCESS')}] {str(f)}")
             success[f] = True
@@ -975,6 +988,8 @@ def command_update_all(args: ArgsProtocol) -> int | None:
     print_bar(f"[{color(AnsiFore.BOLD_WHITE, 'SUMMARY')}]")
     failed = 0
     for f in files:
+        if f not in success:
+            continue  # Skipped file
         if success[f]:
             safe_print(f"  - {str(f)}: {color(AnsiFore.GREEN, 'SUCCESS')}")
         else:
@@ -983,6 +998,17 @@ def command_update_all(args: ArgsProtocol) -> int | None:
     return failed
 
 
+def command_update_all(args: ArgsProtocol) -> int | None:
+    files = list_yaml_files(args.configuration)
+
+    def build_command(f):
+        if CORE.dashboard:
+            return ["esphome", "--dashboard", "run", f, "--no-logs", "--device", "OTA"]
+        return ["esphome", "run", f, "--no-logs", "--device", "OTA"]
+
+    return run_multiple_configs(files, build_command)
+
+
 def command_idedata(args: ArgsProtocol, config: ConfigType) -> int:
     import json
 
@@ -1533,38 +1559,48 @@ def run_esphome(argv):
 
     _LOGGER.info("ESPHome %s", const.__version__)
 
-    for conf_path in args.configuration:
-        conf_path = Path(conf_path)
-        if any(conf_path.name == x for x in SECRETS_FILES):
-            _LOGGER.warning("Skipping secrets file %s", conf_path)
-            continue
+    # Multiple configurations: use subprocesses to avoid state leakage
+    # between compilations (e.g., LVGL touchscreen state in module globals)
+    if len(args.configuration) > 1:
+        # Build command by reusing argv, replacing all configs with single file
+        # argv[0] is the program path, skip it since we prefix with "esphome"
+        def build_command(f):
+            return (
+                ["esphome"]
+                + [arg for arg in argv[1:] if arg not in args.configuration]
+                + [str(f)]
+            )
 
-        CORE.config_path = conf_path
-        CORE.dashboard = args.dashboard
+        return run_multiple_configs(args.configuration, build_command)
 
-        # For logs command, skip updating external components
-        skip_external = args.command == "logs"
-        config = read_config(
-            dict(args.substitution) if args.substitution else {},
-            skip_external_update=skip_external,
-        )
-        if config is None:
-            return 2
-        CORE.config = config
+    # Single configuration
+    conf_path = Path(args.configuration[0])
+    if any(conf_path.name == x for x in SECRETS_FILES):
+        _LOGGER.warning("Skipping secrets file %s", conf_path)
+        return 0
 
-        if args.command not in POST_CONFIG_ACTIONS:
-            safe_print(f"Unknown command {args.command}")
+    CORE.config_path = conf_path
+    CORE.dashboard = args.dashboard
 
-        try:
-            rc = POST_CONFIG_ACTIONS[args.command](args, config)
-        except EsphomeError as e:
-            _LOGGER.error(e, exc_info=args.verbose)
-            return 1
-        if rc != 0:
-            return rc
+    # For logs command, skip updating external components
+    skip_external = args.command == "logs"
+    config = read_config(
+        dict(args.substitution) if args.substitution else {},
+        skip_external_update=skip_external,
+    )
+    if config is None:
+        return 2
+    CORE.config = config
 
-        CORE.reset()
-    return 0
+    if args.command not in POST_CONFIG_ACTIONS:
+        safe_print(f"Unknown command {args.command}")
+        return 1
+
+    try:
+        return POST_CONFIG_ACTIONS[args.command](args, config)
+    except EsphomeError as e:
+        _LOGGER.error(e, exc_info=args.verbose)
+        return 1
 
 
 def main():

esphome/codegen.py

@@ -69,6 +69,7 @@ from esphome.cpp_types import (  # noqa: F401
     JsonObjectConst,
     Parented,
     PollingComponent,
+    StringRef,
     arduino_json_ns,
     bool_,
     const_char_ptr,

esphome/components/alarm_control_panel/alarm_control_panel.cpp

@@ -67,29 +67,52 @@ void AlarmControlPanel::add_on_ready_callback(std::function<void()> &&callback)
   this->ready_callback_.add(std::move(callback));
 }
 
-void AlarmControlPanel::arm_with_code_(AlarmControlPanelCall &(AlarmControlPanelCall::*arm_method)(),
-                                       const char *code) {
+void AlarmControlPanel::arm_away(optional<std::string> code) {
   auto call = this->make_call();
-  (call.*arm_method)();
-  if (code != nullptr)
-    call.set_code(code);
+  call.arm_away();
+  if (code.has_value())
+    call.set_code(code.value());
   call.perform();
 }
 
-void AlarmControlPanel::arm_away(const char *code) { this->arm_with_code_(&AlarmControlPanelCall::arm_away, code); }
-
-void AlarmControlPanel::arm_home(const char *code) { this->arm_with_code_(&AlarmControlPanelCall::arm_home, code); }
-
-void AlarmControlPanel::arm_night(const char *code) { this->arm_with_code_(&AlarmControlPanelCall::arm_night, code); }
-
-void AlarmControlPanel::arm_vacation(const char *code) {
-  this->arm_with_code_(&AlarmControlPanelCall::arm_vacation, code);
+void AlarmControlPanel::arm_home(optional<std::string> code) {
+  auto call = this->make_call();
+  call.arm_home();
+  if (code.has_value())
+    call.set_code(code.value());
+  call.perform();
 }
 
-void AlarmControlPanel::arm_custom_bypass(const char *code) {
-  this->arm_with_code_(&AlarmControlPanelCall::arm_custom_bypass, code);
+void AlarmControlPanel::arm_night(optional<std::string> code) {
+  auto call = this->make_call();
+  call.arm_night();
+  if (code.has_value())
+    call.set_code(code.value());
+  call.perform();
 }
 
-void AlarmControlPanel::disarm(const char *code) { this->arm_with_code_(&AlarmControlPanelCall::disarm, code); }
+void AlarmControlPanel::arm_vacation(optional<std::string> code) {
+  auto call = this->make_call();
+  call.arm_vacation();
+  if (code.has_value())
+    call.set_code(code.value());
+  call.perform();
+}
+
+void AlarmControlPanel::arm_custom_bypass(optional<std::string> code) {
+  auto call = this->make_call();
+  call.arm_custom_bypass();
+  if (code.has_value())
+    call.set_code(code.value());
+  call.perform();
+}
+
+void AlarmControlPanel::disarm(optional<std::string> code) {
+  auto call = this->make_call();
+  call.disarm();
+  if (code.has_value())
+    call.set_code(code.value());
+  call.perform();
+}
 
 }  // namespace esphome::alarm_control_panel

esphome/components/alarm_control_panel/alarm_control_panel.h

@@ -76,53 +76,37 @@ class AlarmControlPanel : public EntityBase {
    *
    * @param code The code
    */
-  void arm_away(const char *code = nullptr);
-  void arm_away(const optional<std::string> &code) {
-    this->arm_away(code.has_value() ? code.value().c_str() : nullptr);
-  }
+  void arm_away(optional<std::string> code = nullopt);
 
   /** arm the alarm in home mode
    *
    * @param code The code
    */
-  void arm_home(const char *code = nullptr);
-  void arm_home(const optional<std::string> &code) {
-    this->arm_home(code.has_value() ? code.value().c_str() : nullptr);
-  }
+  void arm_home(optional<std::string> code = nullopt);
 
   /** arm the alarm in night mode
    *
    * @param code The code
    */
-  void arm_night(const char *code = nullptr);
-  void arm_night(const optional<std::string> &code) {
-    this->arm_night(code.has_value() ? code.value().c_str() : nullptr);
-  }
+  void arm_night(optional<std::string> code = nullopt);
 
   /** arm the alarm in vacation mode
    *
    * @param code The code
    */
-  void arm_vacation(const char *code = nullptr);
-  void arm_vacation(const optional<std::string> &code) {
-    this->arm_vacation(code.has_value() ? code.value().c_str() : nullptr);
-  }
+  void arm_vacation(optional<std::string> code = nullopt);
 
   /** arm the alarm in custom bypass mode
    *
    * @param code The code
    */
-  void arm_custom_bypass(const char *code = nullptr);
-  void arm_custom_bypass(const optional<std::string> &code) {
-    this->arm_custom_bypass(code.has_value() ? code.value().c_str() : nullptr);
-  }
+  void arm_custom_bypass(optional<std::string> code = nullopt);
 
   /** disarm the alarm
    *
    * @param code The code
    */
-  void disarm(const char *code = nullptr);
-  void disarm(const optional<std::string> &code) { this->disarm(code.has_value() ? code.value().c_str() : nullptr); }
+  void disarm(optional<std::string> code = nullopt);
 
   /** Get the state
    *
@@ -134,8 +118,6 @@ class AlarmControlPanel : public EntityBase {
 
  protected:
   friend AlarmControlPanelCall;
-  // Helper to reduce code duplication for arm/disarm methods
-  void arm_with_code_(AlarmControlPanelCall &(AlarmControlPanelCall::*arm_method)(), const char *code);
   // in order to store last panel state in flash
   ESPPreferenceObject pref_;
   // current state

esphome/components/alarm_control_panel/alarm_control_panel_call.cpp

@@ -10,10 +10,8 @@ static const char *const TAG = "alarm_control_panel";
 
 AlarmControlPanelCall::AlarmControlPanelCall(AlarmControlPanel *parent) : parent_(parent) {}
 
-AlarmControlPanelCall &AlarmControlPanelCall::set_code(const char *code) {
-  if (code != nullptr) {
-    this->code_ = std::string(code);
-  }
+AlarmControlPanelCall &AlarmControlPanelCall::set_code(const std::string &code) {
+  this->code_ = code;
   return *this;
 }
 

esphome/components/alarm_control_panel/alarm_control_panel_call.h

@@ -14,8 +14,7 @@ class AlarmControlPanelCall {
  public:
   AlarmControlPanelCall(AlarmControlPanel *parent);
 
-  AlarmControlPanelCall &set_code(const char *code);
-  AlarmControlPanelCall &set_code(const std::string &code) { return this->set_code(code.c_str()); }
+  AlarmControlPanelCall &set_code(const std::string &code);
   AlarmControlPanelCall &arm_away();
   AlarmControlPanelCall &arm_home();
   AlarmControlPanelCall &arm_night();

esphome/components/alarm_control_panel/automation.h

@@ -66,7 +66,15 @@ template<typename... Ts> class ArmAwayAction : public Action<Ts...> {
 
   TEMPLATABLE_VALUE(std::string, code)
 
-  void play(const Ts &...x) override { this->alarm_control_panel_->arm_away(this->code_.optional_value(x...)); }
+  void play(const Ts &...x) override {
+    auto call = this->alarm_control_panel_->make_call();
+    auto code = this->code_.optional_value(x...);
+    if (code.has_value()) {
+      call.set_code(code.value());
+    }
+    call.arm_away();
+    call.perform();
+  }
 
  protected:
   AlarmControlPanel *alarm_control_panel_;
@@ -78,7 +86,15 @@ template<typename... Ts> class ArmHomeAction : public Action<Ts...> {
 
   TEMPLATABLE_VALUE(std::string, code)
 
-  void play(const Ts &...x) override { this->alarm_control_panel_->arm_home(this->code_.optional_value(x...)); }
+  void play(const Ts &...x) override {
+    auto call = this->alarm_control_panel_->make_call();
+    auto code = this->code_.optional_value(x...);
+    if (code.has_value()) {
+      call.set_code(code.value());
+    }
+    call.arm_home();
+    call.perform();
+  }
 
  protected:
   AlarmControlPanel *alarm_control_panel_;
@@ -90,7 +106,15 @@ template<typename... Ts> class ArmNightAction : public Action<Ts...> {
 
   TEMPLATABLE_VALUE(std::string, code)
 
-  void play(const Ts &...x) override { this->alarm_control_panel_->arm_night(this->code_.optional_value(x...)); }
+  void play(const Ts &...x) override {
+    auto call = this->alarm_control_panel_->make_call();
+    auto code = this->code_.optional_value(x...);
+    if (code.has_value()) {
+      call.set_code(code.value());
+    }
+    call.arm_night();
+    call.perform();
+  }
 
  protected:
   AlarmControlPanel *alarm_control_panel_;

esphome/components/am43/am43_base.cpp

@@ -1,21 +1,12 @@
 #include "am43_base.h"
+#include "esphome/core/helpers.h"
 #include <cstring>
-#include <cstdio>
 
 namespace esphome {
 namespace am43 {
 
 const uint8_t START_PACKET[5] = {0x00, 0xff, 0x00, 0x00, 0x9a};
 
-std::string pkt_to_hex(const uint8_t *data, uint16_t len) {
-  char buf[64];
-  memset(buf, 0, 64);
-  for (int i = 0; i < len; i++)
-    sprintf(&buf[i * 2], "%02x", data[i]);
-  std::string ret = buf;
-  return ret;
-}
-
 Am43Packet *Am43Encoder::get_battery_level_request() {
   uint8_t data = 0x1;
   return this->encode_(0xA2, &data, 1);
@@ -73,7 +64,9 @@ Am43Packet *Am43Encoder::encode_(uint8_t command, uint8_t *data, uint8_t length)
   memcpy(&this->packet_.data[7], data, length);
   this->packet_.length = length + 7;
   this->checksum_();
-  ESP_LOGV("am43", "ENC(%d): 0x%s", packet_.length, pkt_to_hex(packet_.data, packet_.length).c_str());
+  char hex_buf[format_hex_size(sizeof(this->packet_.data))];
+  ESP_LOGV("am43", "ENC(%d): 0x%s", this->packet_.length,
+           format_hex_to(hex_buf, this->packet_.data, this->packet_.length));
   return &this->packet_;
 }
 
@@ -88,7 +81,8 @@ void Am43Decoder::decode(const uint8_t *data, uint16_t length) {
   this->has_set_state_response_ = false;
   this->has_position_ = false;
   this->has_pin_response_ = false;
-  ESP_LOGV("am43", "DEC(%d): 0x%s", length, pkt_to_hex(data, length).c_str());
+  char hex_buf[format_hex_size(24)];  // Max expected packet size
+  ESP_LOGV("am43", "DEC(%d): 0x%s", length, format_hex_to(hex_buf, data, length));
 
   if (length < 2 || data[0] != 0x9a)
     return;

esphome/components/anova/anova_base.cpp

@@ -18,31 +18,31 @@ AnovaPacket *AnovaCodec::clean_packet_() {
 
 AnovaPacket *AnovaCodec::get_read_device_status_request() {
   this->current_query_ = READ_DEVICE_STATUS;
-  sprintf((char *) this->packet_.data, "%s", CMD_READ_DEVICE_STATUS);
+  snprintf((char *) this->packet_.data, sizeof(this->packet_.data), "%s", CMD_READ_DEVICE_STATUS);
   return this->clean_packet_();
 }
 
 AnovaPacket *AnovaCodec::get_read_target_temp_request() {
   this->current_query_ = READ_TARGET_TEMPERATURE;
-  sprintf((char *) this->packet_.data, "%s", CMD_READ_TARGET_TEMP);
+  snprintf((char *) this->packet_.data, sizeof(this->packet_.data), "%s", CMD_READ_TARGET_TEMP);
   return this->clean_packet_();
 }
 
 AnovaPacket *AnovaCodec::get_read_current_temp_request() {
   this->current_query_ = READ_CURRENT_TEMPERATURE;
-  sprintf((char *) this->packet_.data, "%s", CMD_READ_CURRENT_TEMP);
+  snprintf((char *) this->packet_.data, sizeof(this->packet_.data), "%s", CMD_READ_CURRENT_TEMP);
   return this->clean_packet_();
 }
 
 AnovaPacket *AnovaCodec::get_read_unit_request() {
   this->current_query_ = READ_UNIT;
-  sprintf((char *) this->packet_.data, "%s", CMD_READ_UNIT);
+  snprintf((char *) this->packet_.data, sizeof(this->packet_.data), "%s", CMD_READ_UNIT);
   return this->clean_packet_();
 }
 
 AnovaPacket *AnovaCodec::get_read_data_request() {
   this->current_query_ = READ_DATA;
-  sprintf((char *) this->packet_.data, "%s", CMD_READ_DATA);
+  snprintf((char *) this->packet_.data, sizeof(this->packet_.data), "%s", CMD_READ_DATA);
   return this->clean_packet_();
 }
 
@@ -50,25 +50,25 @@ AnovaPacket *AnovaCodec::get_set_target_temp_request(float temperature) {
   this->current_query_ = SET_TARGET_TEMPERATURE;
   if (this->fahrenheit_)
     temperature = ctof(temperature);
-  sprintf((char *) this->packet_.data, CMD_SET_TARGET_TEMP, temperature);
+  snprintf((char *) this->packet_.data, sizeof(this->packet_.data), CMD_SET_TARGET_TEMP, temperature);
   return this->clean_packet_();
 }
 
 AnovaPacket *AnovaCodec::get_set_unit_request(char unit) {
   this->current_query_ = SET_UNIT;
-  sprintf((char *) this->packet_.data, CMD_SET_TEMP_UNIT, unit);
+  snprintf((char *) this->packet_.data, sizeof(this->packet_.data), CMD_SET_TEMP_UNIT, unit);
   return this->clean_packet_();
 }
 
 AnovaPacket *AnovaCodec::get_start_request() {
   this->current_query_ = START;
-  sprintf((char *) this->packet_.data, CMD_START);
+  snprintf((char *) this->packet_.data, sizeof(this->packet_.data), "%s", CMD_START);
   return this->clean_packet_();
 }
 
 AnovaPacket *AnovaCodec::get_stop_request() {
   this->current_query_ = STOP;
-  sprintf((char *) this->packet_.data, CMD_STOP);
+  snprintf((char *) this->packet_.data, sizeof(this->packet_.data), "%s", CMD_STOP);
   return this->clean_packet_();
 }
 

esphome/components/api/api_connection.cpp

@@ -1715,7 +1715,7 @@ void APIConnection::on_home_assistant_state_response(const HomeAssistantStateRes
     // HA state max length is 255 characters, but attributes can be much longer
     // Use stack buffer for common case (states), heap fallback for large attributes
     size_t state_len = msg.state.size();
-    SmallBufferWithHeapFallback<256> state_buf_alloc(state_len + 1);
+    SmallBufferWithHeapFallback<MAX_STATE_LEN + 1> state_buf_alloc(state_len + 1);
     char *state_buf = reinterpret_cast<char *>(state_buf_alloc.get());
     if (state_len > 0) {
       memcpy(state_buf, msg.state.c_str(), state_len);

esphome/components/dfrobot_sen0395/commands.h

@@ -75,8 +75,8 @@ class SetLatencyCommand : public Command {
 class SensorCfgStartCommand : public Command {
  public:
   SensorCfgStartCommand(bool startup_mode) : startup_mode_(startup_mode) {
-    char tmp_cmd[20] = {0};
-    sprintf(tmp_cmd, "sensorCfgStart %d", startup_mode);
+    char tmp_cmd[20];  // "sensorCfgStart " (15) + "0/1" (1) + null = 17
+    buf_append_printf(tmp_cmd, sizeof(tmp_cmd), 0, "sensorCfgStart %d", startup_mode);
     cmd_ = std::string(tmp_cmd);
   }
   uint8_t on_message(std::string &message) override;
@@ -142,8 +142,8 @@ class SensitivityCommand : public Command {
   SensitivityCommand(uint8_t sensitivity) : sensitivity_(sensitivity) {
     if (sensitivity > 9)
       sensitivity_ = sensitivity = 9;
-    char tmp_cmd[20] = {0};
-    sprintf(tmp_cmd, "setSensitivity %d", sensitivity);
+    char tmp_cmd[20];  // "setSensitivity " (15) + "0-9" (1) + null = 17
+    buf_append_printf(tmp_cmd, sizeof(tmp_cmd), 0, "setSensitivity %d", sensitivity);
     cmd_ = std::string(tmp_cmd);
   };
   uint8_t on_message(std::string &message) override;

esphome/components/dsmr/__init__.py

@@ -25,29 +25,13 @@ dsmr_ns = cg.esphome_ns.namespace("esphome::dsmr")
 Dsmr = dsmr_ns.class_("Dsmr", cg.Component, uart.UARTDevice)
 
 
-def _validate_key(value):
-    value = cv.string_strict(value)
-    parts = [value[i : i + 2] for i in range(0, len(value), 2)]
-    if len(parts) != 16:
-        raise cv.Invalid("Decryption key must consist of 16 hexadecimal numbers")
-    parts_int = []
-    if any(len(part) != 2 for part in parts):
-        raise cv.Invalid("Decryption key must be format XX")
-    for part in parts:
-        try:
-            parts_int.append(int(part, 16))
-        except ValueError:
-            # pylint: disable=raise-missing-from
-            raise cv.Invalid("Decryption key must be hex values from 00 to FF")
-
-    return "".join(f"{part:02X}" for part in parts_int)
-
-
 CONFIG_SCHEMA = cv.All(
     cv.Schema(
         {
             cv.GenerateID(): cv.declare_id(Dsmr),
-            cv.Optional(CONF_DECRYPTION_KEY): _validate_key,
+            cv.Optional(CONF_DECRYPTION_KEY): lambda value: cv.bind_key(
+                value, name="Decryption key"
+            ),
             cv.Optional(CONF_CRC_CHECK, default=True): cv.boolean,
             cv.Optional(CONF_GAS_MBUS_ID, default=1): cv.int_,
             cv.Optional(CONF_WATER_MBUS_ID, default=2): cv.int_,

esphome/components/dsmr/dsmr.cpp

@@ -1,4 +1,5 @@
 #include "dsmr.h"
+#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 
 #include <AES.h>
@@ -294,8 +295,8 @@ void Dsmr::dump_config() {
   DSMR_TEXT_SENSOR_LIST(DSMR_LOG_TEXT_SENSOR, )
 }
 
-void Dsmr::set_decryption_key(const std::string &decryption_key) {
-  if (decryption_key.empty()) {
+void Dsmr::set_decryption_key(const char *decryption_key) {
+  if (decryption_key == nullptr || decryption_key[0] == '\0') {
     ESP_LOGI(TAG, "Disabling decryption");
     this->decryption_key_.clear();
     if (this->crypt_telegram_ != nullptr) {
@@ -305,21 +306,15 @@ void Dsmr::set_decryption_key(const std::string &decryption_key) {
     return;
   }
 
-  if (decryption_key.length() != 32) {
-    ESP_LOGE(TAG, "Error, decryption key must be 32 character long");
+  if (!parse_hex(decryption_key, this->decryption_key_, 16)) {
+    ESP_LOGE(TAG, "Error, decryption key must be 32 hex characters");
+    this->decryption_key_.clear();
     return;
   }
-  this->decryption_key_.clear();
 
   ESP_LOGI(TAG, "Decryption key is set");
   // Verbose level prints decryption key
-  ESP_LOGV(TAG, "Using decryption key: %s", decryption_key.c_str());
-
-  char temp[3] = {0};
-  for (int i = 0; i < 16; i++) {
-    strncpy(temp, &(decryption_key.c_str()[i * 2]), 2);
-    this->decryption_key_.push_back(std::strtoul(temp, nullptr, 16));
-  }
+  ESP_LOGV(TAG, "Using decryption key: %s", decryption_key);
 
   if (this->crypt_telegram_ == nullptr) {
     this->crypt_telegram_ = new uint8_t[this->max_telegram_len_];  // NOLINT

esphome/components/dsmr/dsmr.h

@@ -63,7 +63,7 @@ class Dsmr : public Component, public uart::UARTDevice {
 
   void dump_config() override;
 
-  void set_decryption_key(const std::string &decryption_key);
+  void set_decryption_key(const char *decryption_key);
   void set_max_telegram_length(size_t length) { this->max_telegram_len_ = length; }
   void set_request_pin(GPIOPin *request_pin) { this->request_pin_ = request_pin; }
   void set_request_interval(uint32_t interval) { this->request_interval_ = interval; }

esphome/components/esp32_ble/ble_uuid.h

@@ -46,6 +46,8 @@ class ESPBTUUID {
 
   esp_bt_uuid_t get_uuid() const;
 
+  // Remove before 2026.8.0
+  ESPDEPRECATED("Use to_str() instead. Removed in 2026.8.0", "2026.2.0")
   std::string to_string() const;
   const char *to_str(std::span<char, UUID_STR_LEN> output) const;
 

esphome/components/event/__init__.py

@@ -90,9 +90,7 @@ async def setup_event_core_(var, config, *, event_types: list[str]):
 
     for conf in config.get(CONF_ON_EVENT, []):
         trigger = cg.new_Pvariable(conf[CONF_TRIGGER_ID], var)
-        await automation.build_automation(
-            trigger, [(cg.std_string, "event_type")], conf
-        )
+        await automation.build_automation(trigger, [(cg.StringRef, "event_type")], conf)
 
     cg.add(var.set_event_types(event_types))
 

esphome/components/event/automation.h

@@ -14,10 +14,10 @@ template<typename... Ts> class TriggerEventAction : public Action<Ts...>, public
   void play(const Ts &...x) override { this->parent_->trigger(this->event_type_.value(x...)); }
 };
 
-class EventTrigger : public Trigger<std::string> {
+class EventTrigger : public Trigger<StringRef> {
  public:
   EventTrigger(Event *event) {
-    event->add_on_event_callback([this](const std::string &event_type) { this->trigger(event_type); });
+    event->add_on_event_callback([this](StringRef event_type) { this->trigger(event_type); });
   }
 };
 

esphome/components/event/event.cpp

@@ -23,7 +23,7 @@ void Event::trigger(const std::string &event_type) {
   }
   this->last_event_type_ = found;
   ESP_LOGD(TAG, "'%s' >> '%s'", this->get_name().c_str(), this->last_event_type_);
-  this->event_callback_.call(event_type);
+  this->event_callback_.call(StringRef(found));
 #if defined(USE_EVENT) && defined(USE_CONTROLLER_REGISTRY)
   ControllerRegistry::notify_event(this);
 #endif
@@ -45,7 +45,7 @@ void Event::set_event_types(const std::vector<const char *> &event_types) {
   this->last_event_type_ = nullptr;  // Reset when types change
 }
 
-void Event::add_on_event_callback(std::function<void(const std::string &event_type)> &&callback) {
+void Event::add_on_event_callback(std::function<void(StringRef event_type)> &&callback) {
   this->event_callback_.add(std::move(callback));
 }
 

esphome/components/event/event.h

@@ -70,10 +70,10 @@ class Event : public EntityBase, public EntityBase_DeviceClass {
   /// Check if an event has been triggered.
   bool has_event() const { return this->last_event_type_ != nullptr; }
 
-  void add_on_event_callback(std::function<void(const std::string &event_type)> &&callback);
+  void add_on_event_callback(std::function<void(StringRef event_type)> &&callback);
 
  protected:
-  LazyCallbackManager<void(const std::string &event_type)> event_callback_;
+  LazyCallbackManager<void(StringRef event_type)> event_callback_;
   FixedVector<const char *> types_;
 
  private:

esphome/components/ezo_pmp/ezo_pmp.cpp

@@ -318,90 +318,93 @@ void EzoPMP::send_next_command_() {
   switch (this->next_command_) {
     // Read Commands
     case EZO_PMP_COMMAND_READ_DOSING:  // Page 54
-      command_buffer_length = sprintf((char *) command_buffer, "D,?");
+      command_buffer_length = snprintf((char *) command_buffer, sizeof(command_buffer), "D,?");
       break;
 
     case EZO_PMP_COMMAND_READ_SINGLE_REPORT:  // Single Report (page 53)
-      command_buffer_length = sprintf((char *) command_buffer, "R");
+      command_buffer_length = snprintf((char *) command_buffer, sizeof(command_buffer), "R");
       break;
 
     case EZO_PMP_COMMAND_READ_MAX_FLOW_RATE:
-      command_buffer_length = sprintf((char *) command_buffer, "DC,?");
+      command_buffer_length = snprintf((char *) command_buffer, sizeof(command_buffer), "DC,?");
       break;
 
     case EZO_PMP_COMMAND_READ_PAUSE_STATUS:
-      command_buffer_length = sprintf((char *) command_buffer, "P,?");
+      command_buffer_length = snprintf((char *) command_buffer, sizeof(command_buffer), "P,?");
       break;
 
     case EZO_PMP_COMMAND_READ_TOTAL_VOLUME_DOSED:
-      command_buffer_length = sprintf((char *) command_buffer, "TV,?");
+      command_buffer_length = snprintf((char *) command_buffer, sizeof(command_buffer), "TV,?");
       break;
 
     case EZO_PMP_COMMAND_READ_ABSOLUTE_TOTAL_VOLUME_DOSED:
-      command_buffer_length = sprintf((char *) command_buffer, "ATV,?");
+      command_buffer_length = snprintf((char *) command_buffer, sizeof(command_buffer), "ATV,?");
       break;
 
     case EZO_PMP_COMMAND_READ_CALIBRATION_STATUS:
-      command_buffer_length = sprintf((char *) command_buffer, "Cal,?");
+      command_buffer_length = snprintf((char *) command_buffer, sizeof(command_buffer), "Cal,?");
       break;
 
     case EZO_PMP_COMMAND_READ_PUMP_VOLTAGE:
-      command_buffer_length = sprintf((char *) command_buffer, "PV,?");
+      command_buffer_length = snprintf((char *) command_buffer, sizeof(command_buffer), "PV,?");
       break;
 
       // Non-Read Commands
 
     case EZO_PMP_COMMAND_FIND:  // Find (page 52)
-      command_buffer_length = sprintf((char *) command_buffer, "Find");
+      command_buffer_length = snprintf((char *) command_buffer, sizeof(command_buffer), "Find");
       wait_time_for_command = 60000;  // This command will block all updates for a minute
       break;
 
     case EZO_PMP_COMMAND_DOSE_CONTINUOUSLY:  // Continuous Dispensing (page 54)
-      command_buffer_length = sprintf((char *) command_buffer, "D,*");
+      command_buffer_length = snprintf((char *) command_buffer, sizeof(command_buffer), "D,*");
       break;
 
     case EZO_PMP_COMMAND_CLEAR_TOTAL_VOLUME_DOSED:  // Clear Total Volume Dosed (page 64)
-      command_buffer_length = sprintf((char *) command_buffer, "Clear");
+      command_buffer_length = snprintf((char *) command_buffer, sizeof(command_buffer), "Clear");
       break;
 
     case EZO_PMP_COMMAND_CLEAR_CALIBRATION:  // Clear Calibration (page 65)
-      command_buffer_length = sprintf((char *) command_buffer, "Cal,clear");
+      command_buffer_length = snprintf((char *) command_buffer, sizeof(command_buffer), "Cal,clear");
       break;
 
     case EZO_PMP_COMMAND_PAUSE_DOSING:  // Pause (page 61)
-      command_buffer_length = sprintf((char *) command_buffer, "P");
+      command_buffer_length = snprintf((char *) command_buffer, sizeof(command_buffer), "P");
       break;
 
     case EZO_PMP_COMMAND_STOP_DOSING:  // Stop (page 62)
-      command_buffer_length = sprintf((char *) command_buffer, "X");
+      command_buffer_length = snprintf((char *) command_buffer, sizeof(command_buffer), "X");
       break;
 
       // Non-Read commands with parameters
 
     case EZO_PMP_COMMAND_DOSE_VOLUME:  // Volume Dispensing (page 55)
-      command_buffer_length = sprintf((char *) command_buffer, "D,%0.1f", this->next_command_volume_);
+      command_buffer_length =
+          snprintf((char *) command_buffer, sizeof(command_buffer), "D,%0.1f", this->next_command_volume_);
       break;
 
     case EZO_PMP_COMMAND_DOSE_VOLUME_OVER_TIME:  // Dose over time (page 56)
-      command_buffer_length =
-          sprintf((char *) command_buffer, "D,%0.1f,%i", this->next_command_volume_, this->next_command_duration_);
+      command_buffer_length = snprintf((char *) command_buffer, sizeof(command_buffer), "D,%0.1f,%i",
+                                       this->next_command_volume_, this->next_command_duration_);
       break;
 
     case EZO_PMP_COMMAND_DOSE_WITH_CONSTANT_FLOW_RATE:  // Constant Flow Rate (page 57)
-      command_buffer_length =
-          sprintf((char *) command_buffer, "DC,%0.1f,%i", this->next_command_volume_, this->next_command_duration_);
+      command_buffer_length = snprintf((char *) command_buffer, sizeof(command_buffer), "DC,%0.1f,%i",
+                                       this->next_command_volume_, this->next_command_duration_);
       break;
 
     case EZO_PMP_COMMAND_SET_CALIBRATION_VOLUME:  // Set Calibration Volume (page 65)
-      command_buffer_length = sprintf((char *) command_buffer, "Cal,%0.2f", this->next_command_volume_);
+      command_buffer_length =
+          snprintf((char *) command_buffer, sizeof(command_buffer), "Cal,%0.2f", this->next_command_volume_);
       break;
 
     case EZO_PMP_COMMAND_CHANGE_I2C_ADDRESS:  // Change I2C Address (page 73)
-      command_buffer_length = sprintf((char *) command_buffer, "I2C,%i", this->next_command_duration_);
+      command_buffer_length =
+          snprintf((char *) command_buffer, sizeof(command_buffer), "I2C,%i", this->next_command_duration_);
       break;
 
     case EZO_PMP_COMMAND_EXEC_ARBITRARY_COMMAND_ADDRESS:  // Run an arbitrary command
-      command_buffer_length = sprintf((char *) command_buffer, this->arbitrary_command_, this->next_command_duration_);
+      command_buffer_length = snprintf((char *) command_buffer, sizeof(command_buffer), "%s", this->arbitrary_command_);
       ESP_LOGI(TAG, "Sending arbitrary command: %s", (char *) command_buffer);
       break;
 

esphome/components/fan/__init__.py

@@ -77,7 +77,7 @@ FanSpeedSetTrigger = fan_ns.class_(
     "FanSpeedSetTrigger", automation.Trigger.template(cg.int_)
 )
 FanPresetSetTrigger = fan_ns.class_(
-    "FanPresetSetTrigger", automation.Trigger.template(cg.std_string)
+    "FanPresetSetTrigger", automation.Trigger.template(cg.StringRef)
 )
 
 FanIsOnCondition = fan_ns.class_("FanIsOnCondition", automation.Condition.template())
@@ -287,7 +287,7 @@ async def setup_fan_core_(var, config):
         await automation.build_automation(trigger, [(cg.int_, "x")], conf)
     for conf in config.get(CONF_ON_PRESET_SET, []):
         trigger = cg.new_Pvariable(conf[CONF_TRIGGER_ID], var)
-        await automation.build_automation(trigger, [(cg.std_string, "x")], conf)
+        await automation.build_automation(trigger, [(cg.StringRef, "x")], conf)
 
 
 async def register_fan(var, config):

esphome/components/fan/automation.h

@@ -208,7 +208,7 @@ class FanSpeedSetTrigger : public Trigger<int> {
   int last_speed_;
 };
 
-class FanPresetSetTrigger : public Trigger<std::string> {
+class FanPresetSetTrigger : public Trigger<StringRef> {
  public:
   FanPresetSetTrigger(Fan *state) {
     state->add_on_state_callback([this, state]() {
@@ -216,7 +216,7 @@ class FanPresetSetTrigger : public Trigger<std::string> {
       auto should_trigger = preset_mode != this->last_preset_mode_;
       this->last_preset_mode_ = preset_mode;
       if (should_trigger) {
-        this->trigger(std::string(preset_mode));
+        this->trigger(preset_mode);
       }
     });
     this->last_preset_mode_ = state->get_preset_mode();

esphome/components/lightwaverf/lightwaverf.cpp

@@ -1,3 +1,4 @@
+#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 
 #ifdef USE_ESP8266
@@ -44,13 +45,16 @@ void LightWaveRF::send_rx(const std::vector<uint8_t> &msg, uint8_t repeats, bool
 }
 
 void LightWaveRF::print_msg_(uint8_t *msg, uint8_t len) {
-  char buffer[65];
+#if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_DEBUG
+  char buffer[65];  // max 10 entries * 6 chars + null
   ESP_LOGD(TAG, " Received code (len:%i): ", len);
 
+  size_t pos = 0;
   for (int i = 0; i < len; i++) {
-    sprintf(&buffer[i * 6], "0x%02x, ", msg[i]);
+    pos = buf_append_printf(buffer, sizeof(buffer), pos, "0x%02x, ", msg[i]);
   }
   ESP_LOGD(TAG, "[%s]", buffer);
+#endif
 }
 
 void LightWaveRF::dump_config() {

esphome/components/mipi_spi/mipi_spi.h

@@ -224,12 +224,9 @@ class MipiSpi : public display::Display,
                     this->madctl_ & MADCTL_BGR ? "BGR" : "RGB", DISPLAYPIXEL * 8, IS_BIG_ENDIAN ? "Big" : "Little");
     if (this->brightness_.has_value())
       esph_log_config(TAG, "  Brightness: %u", this->brightness_.value());
-    if (this->cs_ != nullptr)
-      esph_log_config(TAG, "  CS Pin: %s", this->cs_->dump_summary().c_str());
-    if (this->reset_pin_ != nullptr)
-      esph_log_config(TAG, "  Reset Pin: %s", this->reset_pin_->dump_summary().c_str());
-    if (this->dc_pin_ != nullptr)
-      esph_log_config(TAG, "  DC Pin: %s", this->dc_pin_->dump_summary().c_str());
+    log_pin(TAG, "  CS Pin: ", this->cs_);
+    log_pin(TAG, "  Reset Pin: ", this->reset_pin_);
+    log_pin(TAG, "  DC Pin: ", this->dc_pin_);
     esph_log_config(TAG,
                     "  SPI Mode: %d\n"
                     "  SPI Data rate: %dMHz\n"

esphome/components/mipi_spi/models/adafruit.py

@@ -26,5 +26,3 @@ ST7789V.extend(
     reset_pin=40,
     invert_colors=True,
 )
-
-models = {}

esphome/components/mipi_spi/models/amoled.py

@@ -105,6 +105,3 @@ CO5300 = DriverChip(
         (WCE, 0x00),
     ),
 )
-
-
-models = {}

esphome/components/mipi_spi/models/cyd.py

@@ -1,10 +1,45 @@
-from .ili import ILI9341
+from .ili import ILI9341, ILI9342, ST7789V
 
 ILI9341.extend(
+    # ESP32-2432S028 CYD board with Micro USB, has ILI9341 controller
     "ESP32-2432S028",
     data_rate="40MHz",
-    cs_pin=15,
-    dc_pin=2,
+    cs_pin={"number": 15, "ignore_strapping_warning": True},
+    dc_pin={"number": 2, "ignore_strapping_warning": True},
 )
 
-models = {}
+ST7789V.extend(
+    # ESP32-2432S028 CYD board with USB C + Micro USB, has ST7789V controller
+    "ESP32-2432S028-7789",
+    data_rate="40MHz",
+    cs_pin={"number": 15, "ignore_strapping_warning": True},
+    dc_pin={"number": 2, "ignore_strapping_warning": True},
+)
+
+# fmt: off
+
+ILI9342.extend(
+    # ESP32-2432S028 CYD board with USB C + Micro USB, has ILI9342 controller
+    "ESP32-2432S028-9342",
+    data_rate="40MHz",
+    cs_pin={"number": 15, "ignore_strapping_warning": True},
+    dc_pin={"number": 2, "ignore_strapping_warning": True},
+    initsequence=(
+        (0xCB, 0x39, 0x2C, 0x00, 0x34, 0x02),  # Power Control A
+        (0xCF, 0x00, 0xC1, 0x30),  # Power Control B
+        (0xE8, 0x85, 0x00, 0x78),  # Driver timing control A
+        (0xEA, 0x00, 0x00),  # Driver timing control B
+        (0xED, 0x64, 0x03, 0x12, 0x81),  # Power on sequence control
+        (0xF7, 0x20),  # Pump ratio control
+        (0xC0, 0x23),  # Power Control 1
+        (0xC1, 0x10),  # Power Control 2
+        (0xC5, 0x3E, 0x28),  # VCOM Control 1
+        (0xC7, 0x86),  # VCOM Control 2
+        (0xB1, 0x00, 0x1B),  # Frame Rate Control
+        (0xB6, 0x0A, 0xA2, 0x27, 0x00),  # Display Function Control
+        (0xF2, 0x00),  # Enable 3G
+        (0x26, 0x01),  # Gamma Set
+        (0xE0, 0x00, 0x0C, 0x11, 0x04, 0x11, 0x08, 0x37, 0x89, 0x4C, 0x06, 0x0C, 0x0A, 0x2E, 0x34, 0x0F),  # Positive Gamma Correction
+        (0xE1, 0x00, 0x0B, 0x11, 0x05, 0x13, 0x09, 0x33, 0x67, 0x48, 0x07, 0x0E, 0x0B, 0x23, 0x33, 0x0F),  # Negative Gamma Correction
+    )
+)

esphome/components/mipi_spi/models/ili.py

@@ -148,6 +148,34 @@ ILI9341 = DriverChip(
         ),
     ),
 )
+
+# fmt: off
+
+ILI9342 = DriverChip(
+    "ILI9342",
+    width=320,
+    height=240,
+    mirror_x=True,
+    initsequence=(
+        (0xCB, 0x39, 0x2C, 0x00, 0x34, 0x02),  # Power Control A
+        (0xCF, 0x00, 0xC1, 0x30),  # Power Control B
+        (0xE8, 0x85, 0x00, 0x78),  # Driver timing control A
+        (0xEA, 0x00, 0x00),  # Driver timing control B
+        (0xED, 0x64, 0x03, 0x12, 0x81),  # Power on sequence control
+        (0xF7, 0x20),  # Pump ratio control
+        (0xC0, 0x23),  # Power Control 1
+        (0xC1, 0x10),  # Power Control 2
+        (0xC5, 0x3E, 0x28),  # VCOM Control 1
+        (0xC7, 0x86),  # VCOM Control 2
+        (0xB1, 0x00, 0x1B),  # Frame Rate Control
+        (0xB6, 0x0A, 0xA2, 0x27, 0x00),  # Display Function Control
+        (0xF2, 0x00),  # Enable 3G
+        (0x26, 0x01),  # Gamma Set
+        (0xE0, 0x0F, 0x1F, 0x1C, 0x0C, 0x0F, 0x08, 0x48, 0x98, 0x37, 0x0A, 0x13, 0x04, 0x11, 0x0D, 0x00),  # Positive Gamma
+        (0xE1, 0x0F, 0x32, 0x2E, 0x0B, 0x0D, 0x05, 0x47, 0x75, 0x37, 0x06, 0x10, 0x03, 0x24, 0x20, 0x00),  # Negative Gamma
+    ),
+)
+
 # M5Stack Core2 uses ILI9341 chip - mirror_x disabled for correct orientation
 ILI9341.extend(
     "M5CORE2",
@@ -758,5 +786,3 @@ ST7796.extend(
     dc_pin=0,
     invert_colors=True,
 )
-
-models = {}

esphome/components/mipi_spi/models/jc.py

@@ -588,5 +588,3 @@ DriverChip(
         (0x29, 0x00),
     ),
 )
-
-models = {}

esphome/components/mipi_spi/models/lanbon.py

@@ -11,5 +11,3 @@ ST7789V.extend(
     dc_pin=21,
     reset_pin=18,
 )
-
-models = {}

esphome/components/mipi_spi/models/lilygo.py

@@ -56,5 +56,3 @@ ST7796.extend(
     backlight_pin=48,
     invert_colors=True,
 )
-
-models = {}

esphome/components/mqtt/mqtt_client.cpp

@@ -5,6 +5,7 @@
 #include <utility>
 #include "esphome/components/network/util.h"
 #include "esphome/core/application.h"
+#include "esphome/core/entity_base.h"
 #include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 #include "esphome/core/version.h"
@@ -66,10 +67,13 @@ void MQTTClientComponent::setup() {
         "esphome/discover", [this](const std::string &topic, const std::string &payload) { this->send_device_info_(); },
         2);
 
-    std::string topic = "esphome/ping/";
-    topic.append(App.get_name());
+    // Format topic on stack - subscribe() copies it
+    // "esphome/ping/" (13) + name (ESPHOME_DEVICE_NAME_MAX_LEN) + null (1)
+    constexpr size_t ping_topic_buffer_size = 13 + ESPHOME_DEVICE_NAME_MAX_LEN + 1;
+    char ping_topic[ping_topic_buffer_size];
+    buf_append_printf(ping_topic, sizeof(ping_topic), 0, "esphome/ping/%s", App.get_name().c_str());
     this->subscribe(
-        topic, [this](const std::string &topic, const std::string &payload) { this->send_device_info_(); }, 2);
+        ping_topic, [this](const std::string &topic, const std::string &payload) { this->send_device_info_(); }, 2);
   }
 
   if (this->enable_on_boot_) {
@@ -81,8 +85,11 @@ void MQTTClientComponent::send_device_info_() {
   if (!this->is_connected() or !this->is_discovery_ip_enabled()) {
     return;
   }
-  std::string topic = "esphome/discover/";
-  topic.append(App.get_name());
+  // Format topic on stack to avoid heap allocation
+  // "esphome/discover/" (17) + name (ESPHOME_DEVICE_NAME_MAX_LEN) + null (1)
+  constexpr size_t topic_buffer_size = 17 + ESPHOME_DEVICE_NAME_MAX_LEN + 1;
+  char topic[topic_buffer_size];
+  buf_append_printf(topic, sizeof(topic), 0, "esphome/discover/%s", App.get_name().c_str());
 
   // NOLINTBEGIN(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
   this->publish_json(
@@ -500,39 +507,49 @@ bool MQTTClientComponent::publish(const std::string &topic, const std::string &p
 
 bool MQTTClientComponent::publish(const std::string &topic, const char *payload, size_t payload_length, uint8_t qos,
                                   bool retain) {
-  return publish({.topic = topic, .payload = std::string(payload, payload_length), .qos = qos, .retain = retain});
+  return this->publish(topic.c_str(), payload, payload_length, qos, retain);
 }
 
 bool MQTTClientComponent::publish(const MQTTMessage &message) {
+  return this->publish(message.topic.c_str(), message.payload.c_str(), message.payload.length(), message.qos,
+                       message.retain);
+}
+bool MQTTClientComponent::publish_json(const std::string &topic, const json::json_build_t &f, uint8_t qos,
+                                       bool retain) {
+  return this->publish_json(topic.c_str(), f, qos, retain);
+}
+
+bool MQTTClientComponent::publish(const char *topic, const char *payload, size_t payload_length, uint8_t qos,
+                                  bool retain) {
   if (!this->is_connected()) {
-    // critical components will re-transmit their messages
     return false;
   }
-  bool logging_topic = this->log_message_.topic == message.topic;
-  bool ret = this->mqtt_backend_.publish(message);
+  size_t topic_len = strlen(topic);
+  bool logging_topic = (topic_len == this->log_message_.topic.size()) &&
+                       (memcmp(this->log_message_.topic.c_str(), topic, topic_len) == 0);
+  bool ret = this->mqtt_backend_.publish(topic, payload, payload_length, qos, retain);
   delay(0);
   if (!ret && !logging_topic && this->is_connected()) {
     delay(0);
-    ret = this->mqtt_backend_.publish(message);
+    ret = this->mqtt_backend_.publish(topic, payload, payload_length, qos, retain);
     delay(0);
   }
 
   if (!logging_topic) {
     if (ret) {
-      ESP_LOGV(TAG, "Publish(topic='%s' payload='%s' retain=%d qos=%d)", message.topic.c_str(), message.payload.c_str(),
-               message.retain, message.qos);
+      ESP_LOGV(TAG, "Publish(topic='%s' retain=%d qos=%d)", topic, retain, qos);
+      ESP_LOGVV(TAG, "Publish payload (len=%u): '%.*s'", payload_length, static_cast<int>(payload_length), payload);
     } else {
-      ESP_LOGV(TAG, "Publish failed for topic='%s' (len=%u). Will retry", message.topic.c_str(),
-               message.payload.length());
+      ESP_LOGV(TAG, "Publish failed for topic='%s' (len=%u). Will retry", topic, payload_length);
       this->status_momentary_warning("publish", 1000);
     }
   }
   return ret != 0;
 }
-bool MQTTClientComponent::publish_json(const std::string &topic, const json::json_build_t &f, uint8_t qos,
-                                       bool retain) {
+
+bool MQTTClientComponent::publish_json(const char *topic, const json::json_build_t &f, uint8_t qos, bool retain) {
   std::string message = json::build_json(f);
-  return this->publish(topic, message, qos, retain);
+  return this->publish(topic, message.c_str(), message.length(), qos, retain);
 }
 
 void MQTTClientComponent::enable() {
@@ -610,18 +627,10 @@ static bool topic_match(const char *message, const char *subscription) {
 }
 
 void MQTTClientComponent::on_message(const std::string &topic, const std::string &payload) {
-#ifdef USE_ESP8266
-  // on ESP8266, this is called in lwIP/AsyncTCP task; some components do not like running
-  // from a different task.
-  this->defer([this, topic, payload]() {
-#endif
-    for (auto &subscription : this->subscriptions_) {
-      if (topic_match(topic.c_str(), subscription.topic.c_str()))
-        subscription.callback(topic, payload);
-    }
-#ifdef USE_ESP8266
-  });
-#endif
+  for (auto &subscription : this->subscriptions_) {
+    if (topic_match(topic.c_str(), subscription.topic.c_str()))
+      subscription.callback(topic, payload);
+  }
 }
 
 // Setters

esphome/components/mqtt/mqtt_client.h

@@ -229,6 +229,9 @@ class MQTTClientComponent : public Component
   bool publish(const std::string &topic, const char *payload, size_t payload_length, uint8_t qos = 0,
                bool retain = false);
 
+  /// Publish directly without creating MQTTMessage (avoids heap allocation for topic)
+  bool publish(const char *topic, const char *payload, size_t payload_length, uint8_t qos = 0, bool retain = false);
+
   /** Construct and send a JSON MQTT message.
    *
    * @param topic The topic.
@@ -237,6 +240,9 @@ class MQTTClientComponent : public Component
    */
   bool publish_json(const std::string &topic, const json::json_build_t &f, uint8_t qos = 0, bool retain = false);
 
+  /// Publish JSON directly without heap allocation for topic
+  bool publish_json(const char *topic, const json::json_build_t &f, uint8_t qos = 0, bool retain = false);
+
   /// Setup the MQTT client, registering a bunch of callbacks and attempting to connect.
   void setup() override;
   void dump_config() override;

esphome/components/network/ip_address.h

@@ -60,6 +60,8 @@ struct IPAddress {
   }
   IPAddress(const std::string &in_address) { inet_aton(in_address.c_str(), &ip_addr_); }
   IPAddress(const ip_addr_t *other_ip) { ip_addr_ = *other_ip; }
+  // Remove before 2026.8.0
+  ESPDEPRECATED("Use str_to() instead. Removed in 2026.8.0", "2026.2.0")
   std::string str() const {
     char buf[IP_ADDRESS_BUFFER_SIZE];
     this->str_to(buf);
@@ -147,6 +149,8 @@ struct IPAddress {
   bool is_ip4() const { return IP_IS_V4(&ip_addr_); }
   bool is_ip6() const { return IP_IS_V6(&ip_addr_); }
   bool is_multicast() const { return ip_addr_ismulticast(&ip_addr_); }
+  // Remove before 2026.8.0
+  ESPDEPRECATED("Use str_to() instead. Removed in 2026.8.0", "2026.2.0")
   std::string str() const {
     char buf[IP_ADDRESS_BUFFER_SIZE];
     this->str_to(buf);

esphome/components/pipsolar/output/pipsolar_output.cpp

@@ -8,7 +8,7 @@ namespace pipsolar {
 static const char *const TAG = "pipsolar.output";
 
 void PipsolarOutput::write_state(float state) {
-  char tmp[10];
+  char tmp[16];
   snprintf(tmp, sizeof(tmp), this->set_command_, state);
 
   if (std::find(this->possible_values_.begin(), this->possible_values_.end(), state) != this->possible_values_.end()) {

esphome/components/rf_bridge/rf_bridge.cpp

@@ -1,6 +1,7 @@
 #include "rf_bridge.h"
-#include "esphome/core/log.h"
 #include "esphome/core/application.h"
+#include "esphome/core/helpers.h"
+#include "esphome/core/log.h"
 #include <cinttypes>
 #include <cstring>
 
@@ -72,9 +73,9 @@ bool RFBridgeComponent::parse_bridge_byte_(uint8_t byte) {
 
       data.length = raw[2];
       data.protocol = raw[3];
-      char next_byte[3];
+      char next_byte[3];  // 2 hex chars + null
       for (uint8_t i = 0; i < data.length - 1; i++) {
-        sprintf(next_byte, "%02X", raw[4 + i]);
+        buf_append_printf(next_byte, sizeof(next_byte), 0, "%02X", raw[4 + i]);
         data.code += next_byte;
       }
 
@@ -90,10 +91,10 @@ bool RFBridgeComponent::parse_bridge_byte_(uint8_t byte) {
 
       uint8_t buckets = raw[2] << 1;
       std::string str;
-      char next_byte[3];
+      char next_byte[3];  // 2 hex chars + null
 
       for (uint32_t i = 0; i <= at; i++) {
-        sprintf(next_byte, "%02X", raw[i]);
+        buf_append_printf(next_byte, sizeof(next_byte), 0, "%02X", raw[i]);
         str += next_byte;
         if ((i > 3) && buckets) {
           buckets--;

esphome/components/select/__init__.py

@@ -33,7 +33,7 @@ SelectPtr = Select.operator("ptr")
 # Triggers
 SelectStateTrigger = select_ns.class_(
     "SelectStateTrigger",
-    automation.Trigger.template(cg.std_string, cg.size_t),
+    automation.Trigger.template(cg.StringRef, cg.size_t),
 )
 
 # Actions
@@ -100,7 +100,7 @@ async def setup_select_core_(var, config, *, options: list[str]):
     for conf in config.get(CONF_ON_VALUE, []):
         trigger = cg.new_Pvariable(conf[CONF_TRIGGER_ID], var)
         await automation.build_automation(
-            trigger, [(cg.std_string, "x"), (cg.size_t, "i")], conf
+            trigger, [(cg.StringRef, "x"), (cg.size_t, "i")], conf
         )
 
     if (mqtt_id := config.get(CONF_MQTT_ID)) is not None:

esphome/components/select/automation.h

@@ -6,11 +6,11 @@
 
 namespace esphome::select {
 
-class SelectStateTrigger : public Trigger<std::string, size_t> {
+class SelectStateTrigger : public Trigger<StringRef, size_t> {
  public:
   explicit SelectStateTrigger(Select *parent) : parent_(parent) {
     parent->add_on_state_callback(
-        [this](size_t index) { this->trigger(std::string(this->parent_->option_at(index)), index); });
+        [this](size_t index) { this->trigger(StringRef(this->parent_->option_at(index)), index); });
   }
 
  protected:

esphome/components/shtcx/shtcx.cpp

@@ -13,14 +13,14 @@ static const uint16_t SHTCX_COMMAND_READ_ID_REGISTER = 0xEFC8;
 static const uint16_t SHTCX_COMMAND_SOFT_RESET = 0x805D;
 static const uint16_t SHTCX_COMMAND_POLLING_H = 0x7866;
 
-inline const char *to_string(SHTCXType type) {
+static const LogString *shtcx_type_to_string(SHTCXType type) {
   switch (type) {
     case SHTCX_TYPE_SHTC3:
-      return "SHTC3";
+      return LOG_STR("SHTC3");
     case SHTCX_TYPE_SHTC1:
-      return "SHTC1";
+      return LOG_STR("SHTC1");
     default:
-      return "UNKNOWN";
+      return LOG_STR("UNKNOWN");
   }
 }
 
@@ -52,7 +52,7 @@ void SHTCXComponent::dump_config() {
   ESP_LOGCONFIG(TAG,
                 "SHTCx:\n"
                 "  Model: %s (%04x)",
-                to_string(this->type_), this->sensor_id_);
+                LOG_STR_ARG(shtcx_type_to_string(this->type_)), this->sensor_id_);
   LOG_I2C_DEVICE(this);
   if (this->is_failed()) {
     ESP_LOGE(TAG, ESP_LOG_MSG_COMM_FAIL);

esphome/components/sim800l/sim800l.cpp

@@ -1,4 +1,5 @@
 #include "sim800l.h"
+#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 #include <cstring>
 
@@ -50,8 +51,8 @@ void Sim800LComponent::update() {
   } else if (state_ == STATE_RECEIVED_SMS) {
     // Serial Buffer should have flushed.
     // Send cmd to delete received sms
-    char delete_cmd[20];
-    sprintf(delete_cmd, "AT+CMGD=%d", this->parse_index_);
+    char delete_cmd[20];  // "AT+CMGD=" (8) + uint8_t (max 3) + null = 12 <= 20
+    buf_append_printf(delete_cmd, sizeof(delete_cmd), 0, "AT+CMGD=%d", this->parse_index_);
     this->send_cmd_(delete_cmd);
     this->state_ = STATE_CHECK_SMS;
     this->expect_ack_ = true;

esphome/components/spi_led_strip/spi_led_strip.cpp

@@ -1,4 +1,5 @@
 #include "spi_led_strip.h"
+#include "esphome/core/helpers.h"
 
 namespace esphome {
 namespace spi_led_strip {
@@ -47,15 +48,14 @@ void SpiLedStrip::dump_config() {
 void SpiLedStrip::write_state(light::LightState *state) {
   if (this->is_failed())
     return;
-  if (ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_VERBOSE) {
-    char strbuf[49];
-    size_t len = std::min(this->buffer_size_, (size_t) (sizeof(strbuf) - 1) / 3);
-    memset(strbuf, 0, sizeof(strbuf));
-    for (size_t i = 0; i != len; i++) {
-      sprintf(strbuf + i * 3, "%02X ", this->buf_[i]);
-    }
+#if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_VERBOSE
+  {
+    char strbuf[49];  // format_hex_pretty_size(16) = 48, fits 16 bytes
+    size_t len = std::min(this->buffer_size_, (size_t) 16);
+    format_hex_pretty_to(strbuf, sizeof(strbuf), this->buf_, len, ' ');
     esph_log_v(TAG, "write_state: buf = %s", strbuf);
   }
+#endif
   this->enable();
   this->write_array(this->buf_, this->buffer_size_);
   this->disable();

esphome/components/sprinkler/sprinkler.cpp

@@ -43,13 +43,11 @@ SprinklerControllerSwitch::SprinklerControllerSwitch()
     : turn_on_trigger_(new Trigger<>()), turn_off_trigger_(new Trigger<>()) {}
 
 void SprinklerControllerSwitch::loop() {
-  if (!this->f_.has_value())
-    return;
+  // Loop is only enabled when f_ has a value (see setup())
   auto s = (*this->f_)();
-  if (!s.has_value())
-    return;
-
-  this->publish_state(*s);
+  if (s.has_value()) {
+    this->publish_state(*s);
+  }
 }
 
 void SprinklerControllerSwitch::write_state(bool state) {
@@ -74,7 +72,13 @@ float SprinklerControllerSwitch::get_setup_priority() const { return setup_prior
 Trigger<> *SprinklerControllerSwitch::get_turn_on_trigger() const { return this->turn_on_trigger_; }
 Trigger<> *SprinklerControllerSwitch::get_turn_off_trigger() const { return this->turn_off_trigger_; }
 
-void SprinklerControllerSwitch::setup() { this->state = this->get_initial_state_with_restore_mode().value_or(false); }
+void SprinklerControllerSwitch::setup() {
+  this->state = this->get_initial_state_with_restore_mode().value_or(false);
+  // Disable loop if no state lambda is set - nothing to poll
+  if (!this->f_.has_value()) {
+    this->disable_loop();
+  }
+}
 
 void SprinklerControllerSwitch::dump_config() { LOG_SWITCH("", "Sprinkler Switch", this); }
 
@@ -327,25 +331,32 @@ SprinklerValveOperator *SprinklerValveRunRequest::valve_operator() { return this
 
 SprinklerValveRunRequestOrigin SprinklerValveRunRequest::request_is_from() { return this->origin_; }
 
-Sprinkler::Sprinkler() {}
-Sprinkler::Sprinkler(const std::string &name) {
-  // The `name` is needed to set timers up, hence non-default constructor
-  // replaces `set_name()` method previously existed
-  this->name_ = name;
+Sprinkler::Sprinkler() : Sprinkler("") {}
+Sprinkler::Sprinkler(const char *name) : name_(name) {
+  // The `name` is stored for dump_config logging
   this->timer_.init(2);
-  this->timer_.push_back({this->name_ + "sm", false, 0, 0, std::bind(&Sprinkler::sm_timer_callback_, this)});
-  this->timer_.push_back({this->name_ + "vs", false, 0, 0, std::bind(&Sprinkler::valve_selection_callback_, this)});
+  // Timer names only need to be unique within this component instance
+  this->timer_.push_back({"sm", false, 0, 0, std::bind(&Sprinkler::sm_timer_callback_, this)});
+  this->timer_.push_back({"vs", false, 0, 0, std::bind(&Sprinkler::valve_selection_callback_, this)});
 }
 
-void Sprinkler::setup() { this->all_valves_off_(true); }
+void Sprinkler::setup() {
+  this->all_valves_off_(true);
+  // Start with loop disabled - nothing to do when idle
+  this->disable_loop();
+}
 
 void Sprinkler::loop() {
   for (auto &vo : this->valve_op_) {
     vo.loop();
   }
-  if (this->prev_req_.has_request() && this->prev_req_.has_valve_operator() &&
-      this->prev_req_.valve_operator()->state() == IDLE) {
-    this->prev_req_.reset();
+  if (this->prev_req_.has_request()) {
+    if (this->prev_req_.has_valve_operator() && this->prev_req_.valve_operator()->state() == IDLE) {
+      this->prev_req_.reset();
+    }
+  } else if (this->state_ == IDLE) {
+    // Nothing more to do - disable loop until next activation
+    this->disable_loop();
   }
 }
 
@@ -1333,6 +1344,8 @@ void Sprinkler::start_valve_(SprinklerValveRunRequest *req) {
   if (!this->is_a_valid_valve(req->valve())) {
     return;  // we can't do anything if the valve number isn't valid
   }
+  // Enable loop to monitor valve operator states
+  this->enable_loop();
   for (auto &vo : this->valve_op_) {  // find the first available SprinklerValveOperator, load it and start it up
     if (vo.state() == IDLE) {
       auto run_duration = req->run_duration() ? req->run_duration() : this->valve_run_duration_adjusted(req->valve());
@@ -1575,8 +1588,7 @@ const LogString *Sprinkler::state_as_str_(SprinklerState state) {
 
 void Sprinkler::start_timer_(const SprinklerTimerIndex timer_index) {
   if (this->timer_duration_(timer_index) > 0) {
-    // FixedVector ensures timer_ can't be resized, so .c_str() pointers remain valid
-    this->set_timeout(this->timer_[timer_index].name.c_str(), this->timer_duration_(timer_index),
+    this->set_timeout(this->timer_[timer_index].name, this->timer_duration_(timer_index),
                       this->timer_cbf_(timer_index));
     this->timer_[timer_index].start_time = millis();
     this->timer_[timer_index].active = true;
@@ -1587,7 +1599,7 @@ void Sprinkler::start_timer_(const SprinklerTimerIndex timer_index) {
 
 bool Sprinkler::cancel_timer_(const SprinklerTimerIndex timer_index) {
   this->timer_[timer_index].active = false;
-  return this->cancel_timeout(this->timer_[timer_index].name.c_str());
+  return this->cancel_timeout(this->timer_[timer_index].name);
 }
 
 bool Sprinkler::timer_active_(const SprinklerTimerIndex timer_index) { return this->timer_[timer_index].active; }
@@ -1618,7 +1630,7 @@ void Sprinkler::sm_timer_callback_() {
 }
 
 void Sprinkler::dump_config() {
-  ESP_LOGCONFIG(TAG, "Sprinkler Controller -- %s", this->name_.c_str());
+  ESP_LOGCONFIG(TAG, "Sprinkler Controller -- %s", this->name_);
   if (this->manual_selection_delay_.has_value()) {
     ESP_LOGCONFIG(TAG, "  Manual Selection Delay: %" PRIu32 " seconds", this->manual_selection_delay_.value_or(0));
   }

esphome/components/sprinkler/sprinkler.h

@@ -11,7 +11,7 @@
 
 namespace esphome::sprinkler {
 
-const std::string MIN_STR = "min";
+inline constexpr const char *MIN_STR = "min";
 
 enum SprinklerState : uint8_t {
   // NOTE: these states are used by both SprinklerValveOperator and Sprinkler (the controller)!
@@ -49,7 +49,7 @@ struct SprinklerQueueItem {
 };
 
 struct SprinklerTimer {
-  const std::string name;
+  const char *name;
   bool active;
   uint32_t time;
   uint32_t start_time;
@@ -176,7 +176,7 @@ class SprinklerValveRunRequest {
 class Sprinkler : public Component {
  public:
   Sprinkler();
-  Sprinkler(const std::string &name);
+  Sprinkler(const char *name);
   void setup() override;
   void loop() override;
   void dump_config() override;
@@ -504,7 +504,7 @@ class Sprinkler : public Component {
   uint32_t start_delay_{0};
   uint32_t stop_delay_{0};
 
-  std::string name_;
+  const char *name_{""};
 
   /// Sprinkler controller state
   SprinklerState state_{IDLE};

esphome/components/template/select/__init__.py

@@ -88,5 +88,5 @@ async def to_code(config):
 
     if CONF_SET_ACTION in config:
         await automation.build_automation(
-            var.get_set_trigger(), [(cg.std_string, "x")], config[CONF_SET_ACTION]
+            var.get_set_trigger(), [(cg.StringRef, "x")], config[CONF_SET_ACTION]
         )

esphome/components/template/select/template_select.cpp

@@ -41,7 +41,7 @@ void TemplateSelect::update() {
 }
 
 void TemplateSelect::control(size_t index) {
-  this->set_trigger_->trigger(std::string(this->option_at(index)));
+  this->set_trigger_->trigger(StringRef(this->option_at(index)));
 
   if (this->optimistic_)
     this->publish_state(index);

esphome/components/template/select/template_select.h

@@ -4,6 +4,7 @@
 #include "esphome/core/automation.h"
 #include "esphome/core/component.h"
 #include "esphome/core/preferences.h"
+#include "esphome/core/string_ref.h"
 #include "esphome/core/template_lambda.h"
 
 namespace esphome::template_ {
@@ -17,7 +18,7 @@ class TemplateSelect final : public select::Select, public PollingComponent {
   void dump_config() override;
   float get_setup_priority() const override { return setup_priority::HARDWARE; }
 
-  Trigger<std::string> *get_set_trigger() const { return this->set_trigger_; }
+  Trigger<StringRef> *get_set_trigger() const { return this->set_trigger_; }
   void set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
   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; }
@@ -27,7 +28,7 @@ class TemplateSelect final : public select::Select, public PollingComponent {
   bool optimistic_ = false;
   size_t initial_option_index_{0};
   bool restore_value_ = false;
-  Trigger<std::string> *set_trigger_ = new Trigger<std::string>();
+  Trigger<StringRef> *set_trigger_ = new Trigger<StringRef>();
   TemplateLambda<std::string> f_;
 
   ESPPreferenceObject pref_;

esphome/components/voice_assistant/voice_assistant.h

@@ -81,6 +81,8 @@ struct Timer {
              this->id.c_str(), this->name.c_str(), this->total_seconds, this->seconds_left, YESNO(this->is_active));
     return buffer.data();
   }
+  // Remove before 2026.8.0
+  ESPDEPRECATED("Use to_str() instead. Removed in 2026.8.0", "2026.2.0")
   std::string to_string() const {
     char buffer[TO_STR_BUFFER_SIZE];
     return this->to_str(buffer);

esphome/components/wl_134/wl_134.cpp

@@ -1,4 +1,5 @@
 #include "wl_134.h"
+#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 
 #include <cinttypes>
@@ -78,8 +79,8 @@ Wl134Component::Rfid134Error Wl134Component::read_packet_() {
            reading.id, reading.country, reading.isData ? "true" : "false", reading.isAnimal ? "true" : "false",
            reading.reserved0, reading.reserved1);
 
-  char buf[20];
-  sprintf(buf, "%03d%012lld", reading.country, reading.id);
+  char buf[20];  // "%03d" (3) + "%012" PRId64 (12) + null = 16 max
+  buf_append_printf(buf, sizeof(buf), 0, "%03d%012" PRId64, reading.country, reading.id);
   this->publish_state(buf);
   if (this->do_reset_) {
     this->set_timeout(1000, [this]() { this->publish_state(""); });

esphome/config_validation.py

@@ -1046,20 +1046,20 @@ def mac_address(value):
     return core.MACAddress(*parts_int)
 
 
-def bind_key(value):
+def bind_key(value, *, name="Bind key"):
     value = string_strict(value)
     parts = [value[i : i + 2] for i in range(0, len(value), 2)]
     if len(parts) != 16:
-        raise Invalid("Bind key must consist of 16 hexadecimal numbers")
+        raise Invalid(f"{name} must consist of 16 hexadecimal numbers")
     parts_int = []
     if any(len(part) != 2 for part in parts):
-        raise Invalid("Bind key must be format XX")
+        raise Invalid(f"{name} must be format XX")
     for part in parts:
         try:
             parts_int.append(int(part, 16))
         except ValueError:
             # pylint: disable=raise-missing-from
-            raise Invalid("Bind key must be hex values from 00 to FF")
+            raise Invalid(f"{name} must be hex values from 00 to FF")
 
     return "".join(f"{part:02X}" for part in parts_int)
 

esphome/core/string_ref.h

@@ -72,6 +72,7 @@ class StringRef {
 
   constexpr const char *c_str() const { return base_; }
   constexpr size_type size() const { return len_; }
+  constexpr size_type length() const { return len_; }
   constexpr bool empty() const { return len_ == 0; }
   constexpr const_reference operator[](size_type pos) const { return *(base_ + pos); }
 
@@ -80,6 +81,32 @@ class StringRef {
 
   operator std::string() const { return str(); }
 
+  /// Find first occurrence of substring, returns std::string::npos if not found.
+  /// Note: Requires the underlying string to be null-terminated.
+  size_type find(const char *s, size_type pos = 0) const {
+    if (pos >= len_)
+      return std::string::npos;
+    const char *result = std::strstr(base_ + pos, s);
+    // Verify entire match is within bounds (strstr searches to null terminator)
+    if (result && result + std::strlen(s) <= base_ + len_)
+      return static_cast<size_type>(result - base_);
+    return std::string::npos;
+  }
+  size_type find(char c, size_type pos = 0) const {
+    if (pos >= len_)
+      return std::string::npos;
+    const void *result = std::memchr(base_ + pos, static_cast<unsigned char>(c), len_ - pos);
+    return result ? static_cast<size_type>(static_cast<const char *>(result) - base_) : std::string::npos;
+  }
+
+  /// Return substring as std::string
+  std::string substr(size_type pos = 0, size_type count = std::string::npos) const {
+    if (pos >= len_)
+      return std::string();
+    size_type actual_count = (count == std::string::npos || pos + count > len_) ? len_ - pos : count;
+    return std::string(base_ + pos, actual_count);
+  }
+
  private:
   const char *base_;
   size_type len_;
@@ -160,6 +187,43 @@ inline std::string operator+(const std::string &lhs, const StringRef &rhs) {
   str.append(rhs.c_str(), rhs.size());
   return str;
 }
+// String conversion functions for ADL compatibility (allows stoi(x) where x is StringRef)
+// Must be in esphome namespace for ADL to find them. Uses strtol/strtod directly to avoid heap allocation.
+namespace internal {
+// NOLINTBEGIN(google-runtime-int)
+template<typename R, typename F> inline R parse_number(const StringRef &str, size_t *pos, F conv) {
+  char *end;
+  R result = conv(str.c_str(), &end);
+  // Set pos to 0 on conversion failure (when no characters consumed), otherwise index after number
+  if (pos)
+    *pos = (end == str.c_str()) ? 0 : static_cast<size_t>(end - str.c_str());
+  return result;
+}
+template<typename R, typename F> inline R parse_number(const StringRef &str, size_t *pos, int base, F conv) {
+  char *end;
+  R result = conv(str.c_str(), &end, base);
+  // Set pos to 0 on conversion failure (when no characters consumed), otherwise index after number
+  if (pos)
+    *pos = (end == str.c_str()) ? 0 : static_cast<size_t>(end - str.c_str());
+  return result;
+}
+// NOLINTEND(google-runtime-int)
+}  // namespace internal
+// NOLINTBEGIN(readability-identifier-naming,google-runtime-int)
+inline int stoi(const StringRef &str, size_t *pos = nullptr, int base = 10) {
+  return static_cast<int>(internal::parse_number<long>(str, pos, base, std::strtol));
+}
+inline long stol(const StringRef &str, size_t *pos = nullptr, int base = 10) {
+  return internal::parse_number<long>(str, pos, base, std::strtol);
+}
+inline float stof(const StringRef &str, size_t *pos = nullptr) {
+  return internal::parse_number<float>(str, pos, std::strtof);
+}
+inline double stod(const StringRef &str, size_t *pos = nullptr) {
+  return internal::parse_number<double>(str, pos, std::strtod);
+}
+// NOLINTEND(readability-identifier-naming,google-runtime-int)
+
 #ifdef USE_JSON
 // NOLINTNEXTLINE(readability-identifier-naming)
 inline void convertToJson(const StringRef &src, JsonVariant dst) { dst.set(src.c_str()); }

esphome/cpp_types.py

@@ -44,3 +44,4 @@ gpio_Flags = gpio_ns.enum("Flags", is_class=True)
 EntityCategory = esphome_ns.enum("EntityCategory")
 Parented = esphome_ns.class_("Parented")
 ESPTime = esphome_ns.struct("ESPTime")
+StringRef = esphome_ns.class_("StringRef")

script/ci-custom.py

@@ -732,6 +732,26 @@ def lint_no_heap_allocating_helpers(fname, match):
     )
 
 
+@lint_re_check(
+    # Match sprintf/vsprintf but not snprintf/vsnprintf
+    # [^\w] ensures we don't match the safe variants
+    r"[^\w](v?sprintf)\s*\(" + CPP_RE_EOL,
+    include=cpp_include,
+)
+def lint_no_sprintf(fname, match):
+    func = match.group(1)
+    safe_func = func.replace("sprintf", "snprintf")
+    return (
+        f"{highlight(func + '()')} is not allowed in ESPHome. It has no buffer size limit "
+        f"and can cause buffer overflows.\n"
+        f"Please use one of these alternatives:\n"
+        f"  - {highlight(safe_func + '(buf, sizeof(buf), fmt, ...)')} for general formatting\n"
+        f"  - {highlight('buf_append_printf(buf, sizeof(buf), pos, fmt, ...)')} for "
+        f"offset-based formatting (also stores format strings in flash on ESP8266)\n"
+        f"(If strictly necessary, add `// NOLINT` to the end of the line)"
+    )
+
+
 @lint_content_find_check(
     "ESP_LOG",
     include=["*.h", "*.tcc"],

tests/integration/fixtures/select_stringref_trigger.yaml

@@ -0,0 +1,85 @@
+esphome:
+  name: select-stringref-test
+  friendly_name: Select StringRef Test
+
+host:
+
+logger:
+  level: DEBUG
+
+api:
+
+select:
+  - platform: template
+    name: "Test Select"
+    id: test_select
+    optimistic: true
+    options:
+      - "Option A"
+      - "Option B"
+      - "Option C"
+    initial_option: "Option A"
+    on_value:
+      then:
+        # Test 1: Log the value directly (StringRef -> const char* via c_str())
+        - logger.log:
+            format: "Select value: %s"
+            args: ['x.c_str()']
+        # Test 2: String concatenation (StringRef + const char* -> std::string)
+        - lambda: |-
+            std::string with_suffix = x + " selected";
+            ESP_LOGI("test", "Concatenated: %s", with_suffix.c_str());
+        # Test 3: Comparison (StringRef == const char*)
+        - lambda: |-
+            if (x == "Option B") {
+              ESP_LOGI("test", "Option B was selected");
+            }
+        # Test 4: Use index parameter (variable name is 'i')
+        - lambda: |-
+            ESP_LOGI("test", "Select index: %d", (int)i);
+        # Test 5: StringRef.length() method
+        - lambda: |-
+            ESP_LOGI("test", "Length: %d", (int)x.length());
+        # Test 6: StringRef.find() method with substring
+        - lambda: |-
+            if (x.find("Option") != std::string::npos) {
+              ESP_LOGI("test", "Found 'Option' in value");
+            }
+        # Test 7: StringRef.find() method with character
+        - lambda: |-
+            size_t space_pos = x.find(' ');
+            if (space_pos != std::string::npos) {
+              ESP_LOGI("test", "Space at position: %d", (int)space_pos);
+            }
+        # Test 8: StringRef.substr() method
+        - lambda: |-
+            std::string prefix = x.substr(0, 6);
+            ESP_LOGI("test", "Substr prefix: %s", prefix.c_str());
+
+  # Second select with numeric options to test ADL functions
+  - platform: template
+    name: "Baud Rate"
+    id: baud_select
+    optimistic: true
+    options:
+      - "9600"
+      - "115200"
+    initial_option: "9600"
+    on_value:
+      then:
+        # Test 9: stoi via ADL
+        - lambda: |-
+            int baud = stoi(x);
+            ESP_LOGI("test", "stoi result: %d", baud);
+        # Test 10: stol via ADL
+        - lambda: |-
+            long baud_long = stol(x);
+            ESP_LOGI("test", "stol result: %ld", baud_long);
+        # Test 11: stof via ADL
+        - lambda: |-
+            float baud_float = stof(x);
+            ESP_LOGI("test", "stof result: %.0f", baud_float);
+        # Test 12: stod via ADL
+        - lambda: |-
+            double baud_double = stod(x);
+            ESP_LOGI("test", "stod result: %.0f", baud_double);

tests/integration/test_select_stringref_trigger.py

@@ -0,0 +1,143 @@
+"""Integration test for select on_value trigger with StringRef parameter."""
+
+from __future__ import annotations
+
+import asyncio
+import re
+
+import pytest
+
+from .types import APIClientConnectedFactory, RunCompiledFunction
+
+
+@pytest.mark.asyncio
+async def test_select_stringref_trigger(
+    yaml_config: str,
+    run_compiled: RunCompiledFunction,
+    api_client_connected: APIClientConnectedFactory,
+) -> None:
+    """Test select on_value trigger passes StringRef that works with string operations."""
+    loop = asyncio.get_running_loop()
+
+    # Track log messages to verify StringRef operations work
+    value_logged_future = loop.create_future()
+    concatenated_future = loop.create_future()
+    comparison_future = loop.create_future()
+    index_logged_future = loop.create_future()
+    length_future = loop.create_future()
+    find_substr_future = loop.create_future()
+    find_char_future = loop.create_future()
+    substr_future = loop.create_future()
+    # ADL functions
+    stoi_future = loop.create_future()
+    stol_future = loop.create_future()
+    stof_future = loop.create_future()
+    stod_future = loop.create_future()
+
+    # Patterns to match in logs
+    value_pattern = re.compile(r"Select value: Option B")
+    concatenated_pattern = re.compile(r"Concatenated: Option B selected")
+    comparison_pattern = re.compile(r"Option B was selected")
+    index_pattern = re.compile(r"Select index: 1")
+    length_pattern = re.compile(r"Length: 8")  # "Option B" is 8 chars
+    find_substr_pattern = re.compile(r"Found 'Option' in value")
+    find_char_pattern = re.compile(r"Space at position: 6")  # space at index 6
+    substr_pattern = re.compile(r"Substr prefix: Option")
+    # ADL function patterns (115200 from baud rate select)
+    stoi_pattern = re.compile(r"stoi result: 115200")
+    stol_pattern = re.compile(r"stol result: 115200")
+    stof_pattern = re.compile(r"stof result: 115200")
+    stod_pattern = re.compile(r"stod result: 115200")
+
+    def check_output(line: str) -> None:
+        """Check log output for expected messages."""
+        if not value_logged_future.done() and value_pattern.search(line):
+            value_logged_future.set_result(True)
+        if not concatenated_future.done() and concatenated_pattern.search(line):
+            concatenated_future.set_result(True)
+        if not comparison_future.done() and comparison_pattern.search(line):
+            comparison_future.set_result(True)
+        if not index_logged_future.done() and index_pattern.search(line):
+            index_logged_future.set_result(True)
+        if not length_future.done() and length_pattern.search(line):
+            length_future.set_result(True)
+        if not find_substr_future.done() and find_substr_pattern.search(line):
+            find_substr_future.set_result(True)
+        if not find_char_future.done() and find_char_pattern.search(line):
+            find_char_future.set_result(True)
+        if not substr_future.done() and substr_pattern.search(line):
+            substr_future.set_result(True)
+        # ADL functions
+        if not stoi_future.done() and stoi_pattern.search(line):
+            stoi_future.set_result(True)
+        if not stol_future.done() and stol_pattern.search(line):
+            stol_future.set_result(True)
+        if not stof_future.done() and stof_pattern.search(line):
+            stof_future.set_result(True)
+        if not stod_future.done() and stod_pattern.search(line):
+            stod_future.set_result(True)
+
+    async with (
+        run_compiled(yaml_config, line_callback=check_output),
+        api_client_connected() as client,
+    ):
+        # Verify device info
+        device_info = await client.device_info()
+        assert device_info is not None
+        assert device_info.name == "select-stringref-test"
+
+        # List entities to find our select
+        entities, _ = await client.list_entities_services()
+
+        select_entity = next(
+            (e for e in entities if hasattr(e, "options") and e.name == "Test Select"),
+            None,
+        )
+        assert select_entity is not None, "Test Select entity not found"
+
+        baud_entity = next(
+            (e for e in entities if hasattr(e, "options") and e.name == "Baud Rate"),
+            None,
+        )
+        assert baud_entity is not None, "Baud Rate entity not found"
+
+        # Change select to Option B - this should trigger on_value with StringRef
+        client.select_command(select_entity.key, "Option B")
+        # Change baud to 115200 - this tests ADL functions (stoi, stol, stof, stod)
+        client.select_command(baud_entity.key, "115200")
+
+        # Wait for all log messages confirming StringRef operations work
+        try:
+            await asyncio.wait_for(
+                asyncio.gather(
+                    value_logged_future,
+                    concatenated_future,
+                    comparison_future,
+                    index_logged_future,
+                    length_future,
+                    find_substr_future,
+                    find_char_future,
+                    substr_future,
+                    stoi_future,
+                    stol_future,
+                    stof_future,
+                    stod_future,
+                ),
+                timeout=5.0,
+            )
+        except TimeoutError:
+            results = {
+                "value_logged": value_logged_future.done(),
+                "concatenated": concatenated_future.done(),
+                "comparison": comparison_future.done(),
+                "index_logged": index_logged_future.done(),
+                "length": length_future.done(),
+                "find_substr": find_substr_future.done(),
+                "find_char": find_char_future.done(),
+                "substr": substr_future.done(),
+                "stoi": stoi_future.done(),
+                "stol": stol_future.done(),
+                "stof": stof_future.done(),
+                "stod": stod_future.done(),
+            }
+            pytest.fail(f"StringRef operations failed - received: {results}")

tests/unit_tests/test_main.py

@@ -34,6 +34,7 @@ from esphome.__main__ import (
     has_non_ip_address,
     has_resolvable_address,
     mqtt_get_ip,
+    run_esphome,
     run_miniterm,
     show_logs,
     upload_program,
@@ -1988,7 +1989,7 @@ esp32:
     clean_output = strip_ansi_codes(captured.out)
 
     assert "test-device_123.yaml" in clean_output
-    assert "Updating" in clean_output
+    assert "Processing" in clean_output
     assert "SUCCESS" in clean_output
     assert "SUMMARY" in clean_output
 
@@ -3172,3 +3173,66 @@ def test_run_miniterm_buffer_limit_prevents_unbounded_growth() -> None:
     x_count = printed_line.count("X")
     assert x_count < 150, f"Expected truncation but got {x_count} X's"
     assert x_count == 95, f"Expected 95 X's after truncation but got {x_count}"
+
+
+def test_run_esphome_multiple_configs_with_secrets(
+    tmp_path: Path,
+    mock_run_external_process: Mock,
+    capfd: CaptureFixture[str],
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    """Test run_esphome with multiple configs and secrets file.
+
+    Verifies:
+    - Multiple configs use subprocess isolation
+    - Secrets files are skipped with warning
+    - Secrets files don't appear in summary
+    """
+    # Create two config files and a secrets file
+    yaml_file1 = tmp_path / "device1.yaml"
+    yaml_file1.write_text("""
+esphome:
+  name: device1
+
+esp32:
+  board: nodemcu-32s
+""")
+    yaml_file2 = tmp_path / "device2.yaml"
+    yaml_file2.write_text("""
+esphome:
+  name: device2
+
+esp32:
+  board: nodemcu-32s
+""")
+    secrets_file = tmp_path / "secrets.yaml"
+    secrets_file.write_text("wifi_password: secret123\n")
+
+    setup_core(tmp_path=tmp_path)
+    mock_run_external_process.return_value = 0
+
+    # run_esphome expects argv[0] to be the program name (gets sliced off by parse_args)
+    with caplog.at_level(logging.WARNING):
+        result = run_esphome(
+            ["esphome", "compile", str(yaml_file1), str(secrets_file), str(yaml_file2)]
+        )
+
+    assert result == 0
+
+    # Check secrets file was skipped with warning
+    assert "Skipping secrets file" in caplog.text
+    assert "secrets.yaml" in caplog.text
+
+    captured = capfd.readouterr()
+    clean_output = strip_ansi_codes(captured.out)
+
+    # Both config files should be processed
+    assert "device1.yaml" in clean_output
+    assert "device2.yaml" in clean_output
+    assert "SUMMARY" in clean_output
+
+    # Secrets should not appear in summary
+    summary_section = (
+        clean_output.split("SUMMARY")[1] if "SUMMARY" in clean_output else ""
+    )
+    assert "secrets.yaml" not in summary_section