improve comment

esphome/codegen.py

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

esphome/components/api/api_connection.cpp

@@ -1712,16 +1712,17 @@ void APIConnection::on_home_assistant_state_response(const HomeAssistantStateRes
     }
 
     // Create null-terminated state for callback (parse_number needs null-termination)
-    // 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);
-    char *state_buf = reinterpret_cast<char *>(state_buf_alloc.get());
-    if (state_len > 0) {
-      memcpy(state_buf, msg.state.c_str(), state_len);
+    // HA state max length is 255, so 256 byte buffer covers all cases
+    char state_buf[256];
+    size_t copy_len = msg.state.size();
+    if (copy_len >= sizeof(state_buf)) {
+      copy_len = sizeof(state_buf) - 1;  // Truncate to leave space for null terminator
     }
-    state_buf[state_len] = '\0';
-    it.callback(StringRef(state_buf, state_len));
+    if (copy_len > 0) {
+      memcpy(state_buf, msg.state.c_str(), copy_len);
+    }
+    state_buf[copy_len] = '\0';
+    it.callback(StringRef(state_buf, copy_len));
   }
 }
 #endif

esphome/components/atm90e32/atm90e32.cpp

@@ -158,14 +158,12 @@ void ATM90E32Component::setup() {
 
   if (this->enable_offset_calibration_) {
     // Initialize flash storage for offset calibrations
-    uint32_t o_hash = fnv1_hash("_offset_calibration_");
-    o_hash = fnv1_hash_extend(o_hash, this->cs_summary_);
+    uint32_t o_hash = fnv1_hash(std::string("_offset_calibration_") + this->cs_summary_);
     this->offset_pref_ = global_preferences->make_preference<OffsetCalibration[3]>(o_hash, true);
     this->restore_offset_calibrations_();
 
     // Initialize flash storage for power offset calibrations
-    uint32_t po_hash = fnv1_hash("_power_offset_calibration_");
-    po_hash = fnv1_hash_extend(po_hash, this->cs_summary_);
+    uint32_t po_hash = fnv1_hash(std::string("_power_offset_calibration_") + this->cs_summary_);
     this->power_offset_pref_ = global_preferences->make_preference<PowerOffsetCalibration[3]>(po_hash, true);
     this->restore_power_offset_calibrations_();
   } else {
@@ -185,8 +183,7 @@ void ATM90E32Component::setup() {
 
   if (this->enable_gain_calibration_) {
     // Initialize flash storage for gain calibration
-    uint32_t g_hash = fnv1_hash("_gain_calibration_");
-    g_hash = fnv1_hash_extend(g_hash, this->cs_summary_);
+    uint32_t g_hash = fnv1_hash(std::string("_gain_calibration_") + this->cs_summary_);
     this->gain_calibration_pref_ = global_preferences->make_preference<GainCalibration[3]>(g_hash, true);
     this->restore_gain_calibrations_();
 

esphome/components/audio/audio_reader.cpp

@@ -185,16 +185,18 @@ esp_err_t AudioReader::start(const std::string &uri, AudioFileType &file_type) {
       return err;
     }
 
-    if (str_endswith_ignore_case(url, ".wav")) {
+    std::string url_string = str_lower_case(url);
+
+    if (str_endswith(url_string, ".wav")) {
       file_type = AudioFileType::WAV;
     }
 #ifdef USE_AUDIO_MP3_SUPPORT
-    else if (str_endswith_ignore_case(url, ".mp3")) {
+    else if (str_endswith(url_string, ".mp3")) {
       file_type = AudioFileType::MP3;
     }
 #endif
 #ifdef USE_AUDIO_FLAC_SUPPORT
-    else if (str_endswith_ignore_case(url, ".flac")) {
+    else if (str_endswith(url_string, ".flac")) {
       file_type = AudioFileType::FLAC;
     }
 #endif

esphome/components/bluetooth_proxy/bluetooth_connection.cpp

@@ -135,8 +135,8 @@ void BluetoothConnection::loop() {
   // - For V3_WITH_CACHE: Services are never sent, disable after INIT state
   // - For V3_WITHOUT_CACHE: Disable only after service discovery is complete
   //   (send_service_ == DONE_SENDING_SERVICES, which is only set after services are sent)
-  if (this->state_ != espbt::ClientState::INIT && (this->connection_type_ == espbt::ConnectionType::V3_WITH_CACHE ||
-                                                   this->send_service_ == DONE_SENDING_SERVICES)) {
+  if (this->state() != espbt::ClientState::INIT && (this->connection_type_ == espbt::ConnectionType::V3_WITH_CACHE ||
+                                                    this->send_service_ == DONE_SENDING_SERVICES)) {
     this->disable_loop();
   }
 }

esphome/components/ccs811/ccs811.cpp

@@ -81,8 +81,8 @@ void CCS811Component::setup() {
            bootloader_version, application_version);
   if (this->version_ != nullptr) {
     char version[20];  // "15.15.15 (0xffff)" is 17 chars, plus NUL, plus wiggle room
-    buf_append_printf(version, sizeof(version), 0, "%d.%d.%d (0x%02x)", (application_version >> 12 & 15),
-                      (application_version >> 8 & 15), (application_version >> 4 & 15), application_version);
+    sprintf(version, "%d.%d.%d (0x%02x)", (application_version >> 12 & 15), (application_version >> 8 & 15),
+            (application_version >> 4 & 15), application_version);
     ESP_LOGD(TAG, "publishing version state: %s", version);
     this->version_->publish_state(version);
   }

esphome/components/ch422g/ch422g.cpp

@@ -133,7 +133,7 @@ bool CH422GGPIOPin::digital_read() { return this->parent_->digital_read(this->pi
 
 void CH422GGPIOPin::digital_write(bool value) { this->parent_->digital_write(this->pin_, value ^ this->inverted_); }
 size_t CH422GGPIOPin::dump_summary(char *buffer, size_t len) const {
-  return buf_append_printf(buffer, len, 0, "EXIO%u via CH422G", this->pin_);
+  return snprintf(buffer, len, "EXIO%u via CH422G", this->pin_);
 }
 void CH422GGPIOPin::set_flags(gpio::Flags flags) {
   flags_ = flags;

esphome/components/cse7766/cse7766.cpp

@@ -207,24 +207,20 @@ void CSE7766Component::parse_data_() {
 
 #if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_VERY_VERBOSE
   {
-    // Buffer: 7 + 15 + 33 + 15 + 25 = 95 chars max + null, rounded to 128 for safety margin.
-    // Float sizes with %.4f can be up to 11 chars for large values (e.g., 999999.9999).
-    char buf[128];
-    size_t pos = buf_append_printf(buf, sizeof(buf), 0, "Parsed:");
+    std::string buf = "Parsed:";
     if (have_voltage) {
-      pos = buf_append_printf(buf, sizeof(buf), pos, " V=%.4fV", voltage);
+      buf += str_sprintf(" V=%fV", voltage);
     }
     if (have_current) {
-      pos = buf_append_printf(buf, sizeof(buf), pos, " I=%.4fmA (~%.4fmA)", current * 1000.0f,
-                              calculated_current * 1000.0f);
+      buf += str_sprintf(" I=%fmA (~%fmA)", current * 1000.0f, calculated_current * 1000.0f);
     }
     if (have_power) {
-      pos = buf_append_printf(buf, sizeof(buf), pos, " P=%.4fW", power);
+      buf += str_sprintf(" P=%fW", power);
     }
     if (energy != 0.0f) {
-      buf_append_printf(buf, sizeof(buf), pos, " E=%.4fkWh (%u)", energy, cf_pulses);
+      buf += str_sprintf(" E=%fkWh (%u)", energy, cf_pulses);
     }
-    ESP_LOGVV(TAG, "%s", buf);
+    ESP_LOGVV(TAG, "%s", buf.c_str());
   }
 #endif
 }

esphome/components/daikin_arc/daikin_arc.cpp

@@ -258,9 +258,8 @@ bool DaikinArcClimate::parse_state_frame_(const uint8_t frame[]) {
   }
 
   char buf[DAIKIN_STATE_FRAME_SIZE * 3 + 1] = {0};
-  size_t pos = 0;
   for (size_t i = 0; i < DAIKIN_STATE_FRAME_SIZE; i++) {
-    pos = buf_append_printf(buf, sizeof(buf), pos, "%02x ", frame[i]);
+    sprintf(buf, "%s%02x ", buf, frame[i]);
   }
   ESP_LOGD(TAG, "FRAME %s", buf);
 
@@ -350,9 +349,8 @@ bool DaikinArcClimate::on_receive(remote_base::RemoteReceiveData data) {
   if (data.expect_item(DAIKIN_HEADER_MARK, DAIKIN_HEADER_SPACE)) {
     valid_daikin_frame = true;
     size_t bytes_count = data.size() / 2 / 8;
-    size_t buf_size = bytes_count * 3 + 1;
-    std::unique_ptr<char[]> buf(new char[buf_size]());  // value-initialize (zero-fill)
-    size_t buf_pos = 0;
+    std::unique_ptr<char[]> buf(new char[bytes_count * 3 + 1]);
+    buf[0] = '\0';
     for (size_t i = 0; i < bytes_count; i++) {
       uint8_t byte = 0;
       for (int8_t bit = 0; bit < 8; bit++) {
@@ -363,19 +361,19 @@ bool DaikinArcClimate::on_receive(remote_base::RemoteReceiveData data) {
           break;
         }
       }
-      buf_pos = buf_append_printf(buf.get(), buf_size, buf_pos, "%02x ", byte);
+      sprintf(buf.get(), "%s%02x ", buf.get(), byte);
     }
     ESP_LOGD(TAG, "WHOLE FRAME %s  size: %d", buf.get(), data.size());
   }
   if (!valid_daikin_frame) {
-    char sbuf[16 * 10 + 1] = {0};
-    size_t sbuf_pos = 0;
+    char sbuf[16 * 10 + 1];
+    sbuf[0] = '\0';
     for (size_t j = 0; j < static_cast<size_t>(data.size()); j++) {
       if ((j - 2) % 16 == 0) {
         if (j > 0) {
           ESP_LOGD(TAG, "DATA %04x: %s", (j - 16 > 0xffff ? 0 : j - 16), sbuf);
         }
-        sbuf_pos = 0;
+        sbuf[0] = '\0';
       }
       char type_ch = ' ';
       // debug_tolerance = 25%
@@ -403,10 +401,9 @@ bool DaikinArcClimate::on_receive(remote_base::RemoteReceiveData data) {
         type_ch = '0';
 
       if (abs(data[j]) > 100000) {
-        sbuf_pos = buf_append_printf(sbuf, sizeof(sbuf), sbuf_pos, "%-5d[%c] ", data[j] > 0 ? 99999 : -99999, type_ch);
+        sprintf(sbuf, "%s%-5d[%c] ", sbuf, data[j] > 0 ? 99999 : -99999, type_ch);
       } else {
-        sbuf_pos =
-            buf_append_printf(sbuf, sizeof(sbuf), sbuf_pos, "%-5d[%c] ", (int) (round(data[j] / 10.) * 10), type_ch);
+        sprintf(sbuf, "%s%-5d[%c] ", sbuf, (int) (round(data[j] / 10.) * 10), type_ch);
       }
       if (j + 1 == static_cast<size_t>(data.size())) {
         ESP_LOGD(TAG, "DATA %04x: %s", (j - 8 > 0xffff ? 0 : j - 8), sbuf);

esphome/components/dfrobot_sen0395/commands.cpp

@@ -127,9 +127,7 @@ DetRangeCfgCommand::DetRangeCfgCommand(float min1, float max1, float min2, float
     this->min2_ = min2 = this->max2_ = max2 = this->min3_ = min3 = this->max3_ = max3 = this->min4_ = min4 =
         this->max4_ = max4 = -1;
 
-    char buf[72];  // max 72: "detRangeCfg -1 "(15) + 8 * (float(5) + space(1)) + null
-    snprintf(buf, sizeof(buf), "detRangeCfg -1 %.0f %.0f", min1 / 0.15, max1 / 0.15);
-    this->cmd_ = buf;
+    this->cmd_ = str_sprintf("detRangeCfg -1 %.0f %.0f", min1 / 0.15, max1 / 0.15);
   } else if (min3 < 0 || max3 < 0) {
     this->min1_ = min1 = round(min1 / 0.15) * 0.15;
     this->max1_ = max1 = round(max1 / 0.15) * 0.15;
@@ -137,10 +135,7 @@ DetRangeCfgCommand::DetRangeCfgCommand(float min1, float max1, float min2, float
     this->max2_ = max2 = round(max2 / 0.15) * 0.15;
     this->min3_ = min3 = this->max3_ = max3 = this->min4_ = min4 = this->max4_ = max4 = -1;
 
-    char buf[72];  // max 72: "detRangeCfg -1 "(15) + 8 * (float(5) + space(1)) + null
-    snprintf(buf, sizeof(buf), "detRangeCfg -1 %.0f %.0f %.0f %.0f", min1 / 0.15, max1 / 0.15, min2 / 0.15,
-             max2 / 0.15);
-    this->cmd_ = buf;
+    this->cmd_ = str_sprintf("detRangeCfg -1 %.0f %.0f %.0f %.0f", min1 / 0.15, max1 / 0.15, min2 / 0.15, max2 / 0.15);
   } else if (min4 < 0 || max4 < 0) {
     this->min1_ = min1 = round(min1 / 0.15) * 0.15;
     this->max1_ = max1 = round(max1 / 0.15) * 0.15;
@@ -150,10 +145,9 @@ DetRangeCfgCommand::DetRangeCfgCommand(float min1, float max1, float min2, float
     this->max3_ = max3 = round(max3 / 0.15) * 0.15;
     this->min4_ = min4 = this->max4_ = max4 = -1;
 
-    char buf[72];  // max 72: "detRangeCfg -1 "(15) + 8 * (float(5) + space(1)) + null
-    snprintf(buf, sizeof(buf), "detRangeCfg -1 %.0f %.0f %.0f %.0f %.0f %.0f", min1 / 0.15, max1 / 0.15, min2 / 0.15,
-             max2 / 0.15, min3 / 0.15, max3 / 0.15);
-    this->cmd_ = buf;
+    this->cmd_ = str_sprintf("detRangeCfg -1 "
+                             "%.0f %.0f %.0f %.0f %.0f %.0f",
+                             min1 / 0.15, max1 / 0.15, min2 / 0.15, max2 / 0.15, min3 / 0.15, max3 / 0.15);
   } else {
     this->min1_ = min1 = round(min1 / 0.15) * 0.15;
     this->max1_ = max1 = round(max1 / 0.15) * 0.15;
@@ -164,10 +158,10 @@ DetRangeCfgCommand::DetRangeCfgCommand(float min1, float max1, float min2, float
     this->min4_ = min4 = round(min4 / 0.15) * 0.15;
     this->max4_ = max4 = round(max4 / 0.15) * 0.15;
 
-    char buf[72];  // max 72: "detRangeCfg -1 "(15) + 8 * (float(5) + space(1)) + null
-    snprintf(buf, sizeof(buf), "detRangeCfg -1 %.0f %.0f %.0f %.0f %.0f %.0f %.0f %.0f", min1 / 0.15, max1 / 0.15,
-             min2 / 0.15, max2 / 0.15, min3 / 0.15, max3 / 0.15, min4 / 0.15, max4 / 0.15);
-    this->cmd_ = buf;
+    this->cmd_ = str_sprintf("detRangeCfg -1 "
+                             "%.0f %.0f %.0f %.0f %.0f %.0f %.0f %.0f",
+                             min1 / 0.15, max1 / 0.15, min2 / 0.15, max2 / 0.15, min3 / 0.15, max3 / 0.15, min4 / 0.15,
+                             max4 / 0.15);
   }
 
   this->min1_ = min1;
@@ -209,10 +203,7 @@ SetLatencyCommand::SetLatencyCommand(float delay_after_detection, float delay_af
   delay_after_disappear = std::round(delay_after_disappear / 0.025f) * 0.025f;
   this->delay_after_detection_ = clamp(delay_after_detection, 0.0f, 1638.375f);
   this->delay_after_disappear_ = clamp(delay_after_disappear, 0.0f, 1638.375f);
-  // max 32: "setLatency "(11) + float(8) + " "(1) + float(8) + null, rounded to 32
-  char buf[32];
-  snprintf(buf, sizeof(buf), "setLatency %.03f %.03f", this->delay_after_detection_, this->delay_after_disappear_);
-  this->cmd_ = buf;
+  this->cmd_ = str_sprintf("setLatency %.03f %.03f", this->delay_after_detection_, this->delay_after_disappear_);
 };
 
 uint8_t SetLatencyCommand::on_message(std::string &message) {

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];  // "sensorCfgStart " (15) + "0/1" (1) + null = 17
-    buf_append_printf(tmp_cmd, sizeof(tmp_cmd), 0, "sensorCfgStart %d", startup_mode);
+    char tmp_cmd[20] = {0};
+    sprintf(tmp_cmd, "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];  // "setSensitivity " (15) + "0-9" (1) + null = 17
-    buf_append_printf(tmp_cmd, sizeof(tmp_cmd), 0, "setSensitivity %d", sensitivity);
+    char tmp_cmd[20] = {0};
+    sprintf(tmp_cmd, "setSensitivity %d", sensitivity);
     cmd_ = std::string(tmp_cmd);
   };
   uint8_t on_message(std::string &message) override;

esphome/components/esp32_ble_client/ble_client_base.cpp

@@ -50,7 +50,7 @@ void BLEClientBase::loop() {
     this->set_state(espbt::ClientState::INIT);
     return;
   }
-  if (this->state_ == espbt::ClientState::INIT) {
+  if (this->state() == espbt::ClientState::INIT) {
     auto ret = esp_ble_gattc_app_register(this->app_id);
     if (ret) {
       ESP_LOGE(TAG, "gattc app register failed. app_id=%d code=%d", this->app_id, ret);
@@ -60,7 +60,7 @@ void BLEClientBase::loop() {
   }
   // If idle, we can disable the loop as connect()
   // will enable it again when a connection is needed.
-  else if (this->state_ == espbt::ClientState::IDLE) {
+  else if (this->state() == espbt::ClientState::IDLE) {
     this->disable_loop();
   }
 }
@@ -86,7 +86,7 @@ bool BLEClientBase::parse_device(const espbt::ESPBTDevice &device) {
     return false;
   if (this->address_ == 0 || device.address_uint64() != this->address_)
     return false;
-  if (this->state_ != espbt::ClientState::IDLE)
+  if (this->state() != espbt::ClientState::IDLE)
     return false;
 
   this->log_event_("Found device");
@@ -102,10 +102,10 @@ bool BLEClientBase::parse_device(const espbt::ESPBTDevice &device) {
 
 void BLEClientBase::connect() {
   // Prevent duplicate connection attempts
-  if (this->state_ == espbt::ClientState::CONNECTING || this->state_ == espbt::ClientState::CONNECTED ||
-      this->state_ == espbt::ClientState::ESTABLISHED) {
+  if (this->state() == espbt::ClientState::CONNECTING || this->state() == espbt::ClientState::CONNECTED ||
+      this->state() == espbt::ClientState::ESTABLISHED) {
     ESP_LOGW(TAG, "[%d] [%s] Connection already in progress, state=%s", this->connection_index_, this->address_str_,
-             espbt::client_state_to_string(this->state_));
+             espbt::client_state_to_string(this->state()));
     return;
   }
   ESP_LOGI(TAG, "[%d] [%s] 0x%02x Connecting", this->connection_index_, this->address_str_, this->remote_addr_type_);
@@ -133,12 +133,12 @@ void BLEClientBase::connect() {
 esp_err_t BLEClientBase::pair() { return esp_ble_set_encryption(this->remote_bda_, ESP_BLE_SEC_ENCRYPT); }
 
 void BLEClientBase::disconnect() {
-  if (this->state_ == espbt::ClientState::IDLE || this->state_ == espbt::ClientState::DISCONNECTING) {
+  if (this->state() == espbt::ClientState::IDLE || this->state() == espbt::ClientState::DISCONNECTING) {
     ESP_LOGI(TAG, "[%d] [%s] Disconnect requested, but already %s", this->connection_index_, this->address_str_,
-             espbt::client_state_to_string(this->state_));
+             espbt::client_state_to_string(this->state()));
     return;
   }
-  if (this->state_ == espbt::ClientState::CONNECTING || this->conn_id_ == UNSET_CONN_ID) {
+  if (this->state() == espbt::ClientState::CONNECTING || this->conn_id_ == UNSET_CONN_ID) {
     ESP_LOGD(TAG, "[%d] [%s] Disconnect before connected, disconnect scheduled", this->connection_index_,
              this->address_str_);
     this->want_disconnect_ = true;
@@ -150,7 +150,7 @@ void BLEClientBase::disconnect() {
 void BLEClientBase::unconditional_disconnect() {
   // Disconnect without checking the state.
   ESP_LOGI(TAG, "[%d] [%s] Disconnecting (conn_id: %d).", this->connection_index_, this->address_str_, this->conn_id_);
-  if (this->state_ == espbt::ClientState::DISCONNECTING) {
+  if (this->state() == espbt::ClientState::DISCONNECTING) {
     this->log_error_("Already disconnecting");
     return;
   }
@@ -170,7 +170,7 @@ void BLEClientBase::unconditional_disconnect() {
     this->log_gattc_warning_("esp_ble_gattc_close", err);
   }
 
-  if (this->state_ == espbt::ClientState::DISCOVERED) {
+  if (this->state() == espbt::ClientState::DISCOVERED) {
     this->set_address(0);
     this->set_state(espbt::ClientState::IDLE);
   } else {
@@ -295,18 +295,18 @@ bool BLEClientBase::gattc_event_handler(esp_gattc_cb_event_t event, esp_gatt_if_
       // ESP-IDF's BLE stack may send ESP_GATTC_OPEN_EVT after esp_ble_gattc_open() returns an
       // error, if the error occurred at the BTA/GATT layer. This can result in the event
       // arriving after we've already transitioned to IDLE state.
-      if (this->state_ == espbt::ClientState::IDLE) {
+      if (this->state() == espbt::ClientState::IDLE) {
         ESP_LOGD(TAG, "[%d] [%s] ESP_GATTC_OPEN_EVT in IDLE state (status=%d), ignoring", this->connection_index_,
                  this->address_str_, param->open.status);
         break;
       }
 
-      if (this->state_ != espbt::ClientState::CONNECTING) {
+      if (this->state() != espbt::ClientState::CONNECTING) {
         // This should not happen but lets log it in case it does
         // because it means we have a bad assumption about how the
         // ESP BT stack works.
         ESP_LOGE(TAG, "[%d] [%s] ESP_GATTC_OPEN_EVT in %s state (status=%d)", this->connection_index_,
-                 this->address_str_, espbt::client_state_to_string(this->state_), param->open.status);
+                 this->address_str_, espbt::client_state_to_string(this->state()), param->open.status);
       }
       if (param->open.status != ESP_GATT_OK && param->open.status != ESP_GATT_ALREADY_OPEN) {
         this->log_gattc_warning_("Connection open", param->open.status);
@@ -327,7 +327,7 @@ bool BLEClientBase::gattc_event_handler(esp_gattc_cb_event_t event, esp_gatt_if_
       if (this->connection_type_ == espbt::ConnectionType::V3_WITH_CACHE) {
         // Cached connections already connected with medium parameters, no update needed
         // only set our state, subclients might have more stuff to do yet.
-        this->state_ = espbt::ClientState::ESTABLISHED;
+        this->set_state_internal_(espbt::ClientState::ESTABLISHED);
         break;
       }
       // For V3_WITHOUT_CACHE, we already set fast params before connecting
@@ -356,7 +356,7 @@ bool BLEClientBase::gattc_event_handler(esp_gattc_cb_event_t event, esp_gatt_if_
         return false;
       // Check if we were disconnected while waiting for service discovery
       if (param->disconnect.reason == ESP_GATT_CONN_TERMINATE_PEER_USER &&
-          this->state_ == espbt::ClientState::CONNECTED) {
+          this->state() == espbt::ClientState::CONNECTED) {
         this->log_warning_("Remote closed during discovery");
       } else {
         ESP_LOGD(TAG, "[%d] [%s] ESP_GATTC_DISCONNECT_EVT, reason 0x%02x", this->connection_index_, this->address_str_,
@@ -433,7 +433,7 @@ bool BLEClientBase::gattc_event_handler(esp_gattc_cb_event_t event, esp_gatt_if_
 #endif
       }
       ESP_LOGI(TAG, "[%d] [%s] Service discovery complete", this->connection_index_, this->address_str_);
-      this->state_ = espbt::ClientState::ESTABLISHED;
+      this->set_state_internal_(espbt::ClientState::ESTABLISHED);
       break;
     }
     case ESP_GATTC_READ_DESCR_EVT: {

esphome/components/esp32_ble_client/ble_client_base.h

@@ -44,7 +44,7 @@ class BLEClientBase : public espbt::ESPBTClient, public Component {
   void unconditional_disconnect();
   void release_services();
 
-  bool connected() { return this->state_ == espbt::ClientState::ESTABLISHED; }
+  bool connected() { return this->state() == espbt::ClientState::ESTABLISHED; }
 
   void set_auto_connect(bool auto_connect) { this->auto_connect_ = auto_connect; }
 

esphome/components/esp32_ble_tracker/esp32_ble_tracker.cpp

@@ -105,15 +105,13 @@ void ESP32BLETracker::loop() {
   }
 
   // Check for scan timeout - moved here from scheduler to avoid false reboots
-  // when the loop is blocked
+  // when the loop is blocked. This must run every iteration for safety.
   if (this->scanner_state_ == ScannerState::RUNNING) {
     switch (this->scan_timeout_state_) {
       case ScanTimeoutState::MONITORING: {
-        uint32_t now = App.get_loop_component_start_time();
-        uint32_t timeout_ms = this->scan_duration_ * 2000;
         // Robust time comparison that handles rollover correctly
         // This works because unsigned arithmetic wraps around predictably
-        if ((now - this->scan_start_time_) > timeout_ms) {
+        if ((App.get_loop_component_start_time() - this->scan_start_time_) > this->scan_timeout_ms_) {
           // First time we've seen the timeout exceeded - wait one more loop iteration
           // This ensures all components have had a chance to process pending events
           // This is because esp32_ble may not have run yet and called
@@ -128,13 +126,31 @@ void ESP32BLETracker::loop() {
         ESP_LOGE(TAG, "Scan never terminated, rebooting");
         App.reboot();
         break;
-
       case ScanTimeoutState::INACTIVE:
-        // This case should be unreachable - scanner and timeout states are always synchronized
         break;
     }
   }
 
+  // Fast path: skip expensive client state counting and processing
+  // if no state has changed since last loop iteration.
+  //
+  // How state changes ensure we reach the code below:
+  // - handle_scanner_failure_(): scanner_state_ becomes FAILED via set_scanner_state_(), or
+  //   scan_set_param_failed_ requires scanner_state_==RUNNING which can only be reached via
+  //   set_scanner_state_(RUNNING) in gap_scan_start_complete_() (scan params are set during
+  //   STARTING, not RUNNING, so version is always incremented before this condition is true)
+  // - start_scan_(): scanner_state_ becomes IDLE via set_scanner_state_() in cleanup_scan_state_()
+  // - try_promote_discovered_clients_(): client enters DISCOVERED via set_state(), or
+  //   connecting client finishes (state change), or scanner reaches RUNNING/IDLE
+  //
+  // All conditions that affect the logic below are tied to state changes that increment
+  // state_version_, so the fast path is safe.
+  if (this->state_version_ == this->last_processed_version_) {
+    return;
+  }
+  this->last_processed_version_ = this->state_version_;
+
+  // State changed - do full processing
   ClientStateCounts counts = this->count_client_states_();
   if (counts != this->client_state_counts_) {
     this->client_state_counts_ = counts;
@@ -142,6 +158,7 @@ void ESP32BLETracker::loop() {
              this->client_state_counts_.discovered, this->client_state_counts_.disconnecting);
   }
 
+  // Scanner failure: reached when set_scanner_state_(FAILED) or scan_set_param_failed_ set
   if (this->scanner_state_ == ScannerState::FAILED ||
       (this->scan_set_param_failed_ && this->scanner_state_ == ScannerState::RUNNING)) {
     this->handle_scanner_failure_();
@@ -160,6 +177,8 @@ void ESP32BLETracker::loop() {
 
   */
 
+  // Start scan: reached when scanner_state_ becomes IDLE (via set_scanner_state_()) and
+  // all clients are idle (their state changes increment version when they finish)
   if (this->scanner_state_ == ScannerState::IDLE && !counts.connecting && !counts.disconnecting && !counts.discovered) {
 #ifdef USE_ESP32_BLE_SOFTWARE_COEXISTENCE
     this->update_coex_preference_(false);
@@ -168,8 +187,9 @@ void ESP32BLETracker::loop() {
       this->start_scan_(false);  // first = false
     }
   }
-  // If there is a discovered client and no connecting
-  // clients, then promote the discovered client to ready to connect.
+  // Promote discovered clients: reached when a client's state becomes DISCOVERED (via set_state()),
+  // or when a blocking condition clears (connecting client finishes, scanner reaches RUNNING/IDLE).
+  // All these trigger state_version_ increment, so we'll process and check promotion eligibility.
   // We check both RUNNING and IDLE states because:
   // - RUNNING: gap_scan_event_handler initiates stop_scan_() but promotion can happen immediately
   // - IDLE: Scanner has already stopped (naturally or by gap_scan_event_handler)
@@ -236,6 +256,7 @@ void ESP32BLETracker::start_scan_(bool first) {
   // Start timeout monitoring in loop() instead of using scheduler
   // This prevents false reboots when the loop is blocked
   this->scan_start_time_ = App.get_loop_component_start_time();
+  this->scan_timeout_ms_ = this->scan_duration_ * 2000;
   this->scan_timeout_state_ = ScanTimeoutState::MONITORING;
 
   esp_err_t err = esp_ble_gap_set_scan_params(&this->scan_params_);
@@ -253,6 +274,10 @@ void ESP32BLETracker::start_scan_(bool first) {
 void ESP32BLETracker::register_client(ESPBTClient *client) {
 #ifdef ESPHOME_ESP32_BLE_TRACKER_CLIENT_COUNT
   client->app_id = ++this->app_id_;
+  // Give client a pointer to our state_version_ so it can notify us of state changes.
+  // This enables loop() fast-path optimization - we skip expensive work when no state changed.
+  // Safe because ESP32BLETracker (singleton) outlives all registered clients.
+  client->set_tracker_state_version(&this->state_version_);
   this->clients_.push_back(client);
   this->recalculate_advertisement_parser_types();
 #endif
@@ -382,6 +407,7 @@ void ESP32BLETracker::gattc_event_handler(esp_gattc_cb_event_t event, esp_gatt_i
 
 void ESP32BLETracker::set_scanner_state_(ScannerState state) {
   this->scanner_state_ = state;
+  this->state_version_++;
   for (auto *listener : this->scanner_state_listeners_) {
     listener->on_scanner_state(state);
   }

esphome/components/esp32_ble_tracker/esp32_ble_tracker.h

@@ -216,6 +216,19 @@ enum class ConnectionType : uint8_t {
   V3_WITHOUT_CACHE
 };
 
+/// Base class for BLE GATT clients that connect to remote devices.
+///
+/// State Change Tracking Design:
+/// -----------------------------
+/// ESP32BLETracker::loop() needs to know when client states change to avoid
+/// expensive polling. Rather than checking all clients every iteration (~7000/min),
+/// we use a version counter owned by ESP32BLETracker that clients increment on
+/// state changes. The tracker compares versions to skip work when nothing changed.
+///
+/// Ownership: ESP32BLETracker owns state_version_. Clients hold a non-owning
+/// pointer (tracker_state_version_) set during register_client(). Clients
+/// increment the counter through this pointer when their state changes.
+/// The pointer may be null if the client is not registered with a tracker.
 class ESPBTClient : public ESPBTDeviceListener {
  public:
   virtual bool gattc_event_handler(esp_gattc_cb_event_t event, esp_gatt_if_t gattc_if,
@@ -225,26 +238,49 @@ class ESPBTClient : public ESPBTDeviceListener {
   virtual void disconnect() = 0;
   bool disconnect_pending() const { return this->want_disconnect_; }
   void cancel_pending_disconnect() { this->want_disconnect_ = false; }
+
+  /// Set the client state with IDLE handling (clears want_disconnect_).
+  /// Notifies the tracker of state change for loop optimization.
   virtual void set_state(ClientState st) {
-    this->state_ = st;
+    this->set_state_internal_(st);
     if (st == ClientState::IDLE) {
       this->want_disconnect_ = false;
     }
   }
-  ClientState state() const { return state_; }
+  ClientState state() const { return this->state_; }
+
+  /// Called by ESP32BLETracker::register_client() to enable state change notifications.
+  /// The pointer must remain valid for the lifetime of the client (guaranteed since
+  /// ESP32BLETracker is a singleton that outlives all clients).
+  void set_tracker_state_version(uint8_t *version) { this->tracker_state_version_ = version; }
 
   // Memory optimized layout
   uint8_t app_id;  // App IDs are small integers assigned sequentially
 
  protected:
-  // Group 1: 1-byte types
-  ClientState state_{ClientState::INIT};
+  /// Set state without IDLE handling - use for direct state transitions.
+  /// Increments the tracker's state version counter to signal that loop()
+  /// should do full processing on the next iteration.
+  void set_state_internal_(ClientState st) {
+    this->state_ = st;
+    // Notify tracker that state changed (tracker_state_version_ is owned by ESP32BLETracker)
+    if (this->tracker_state_version_ != nullptr) {
+      (*this->tracker_state_version_)++;
+    }
+  }
+
   // want_disconnect_ is set to true when a disconnect is requested
   // while the client is connecting. This is used to disconnect the
   // client as soon as we get the connection id (conn_id_) from the
   // ESP_GATTC_OPEN_EVT event.
   bool want_disconnect_{false};
-  // 2 bytes used, 2 bytes padding
+
+ private:
+  ClientState state_{ClientState::INIT};
+  /// Non-owning pointer to ESP32BLETracker::state_version_. When this client's
+  /// state changes, we increment the tracker's counter to signal that loop()
+  /// should perform full processing. Null if client not registered with tracker.
+  uint8_t *tracker_state_version_{nullptr};
 };
 
 class ESP32BLETracker : public Component,
@@ -380,6 +416,16 @@ class ESP32BLETracker : public Component,
   // Group 4: 1-byte types (enums, uint8_t, bool)
   uint8_t app_id_{0};
   uint8_t scan_start_fail_count_{0};
+  /// Version counter for loop() fast-path optimization. Incremented when:
+  /// - Scanner state changes (via set_scanner_state_())
+  /// - Any registered client's state changes (clients hold pointer to this counter)
+  /// Owned by this class; clients receive non-owning pointer via register_client().
+  /// When loop() sees state_version_ == last_processed_version_, it skips expensive
+  /// client state counting and takes the fast path (just timeout check + return).
+  uint8_t state_version_{0};
+  /// Last state_version_ value when loop() did full processing. Compared against
+  /// state_version_ to detect if any state changed since last iteration.
+  uint8_t last_processed_version_{0};
   ScannerState scanner_state_{ScannerState::IDLE};
   bool scan_continuous_;
   bool scan_active_;
@@ -396,6 +442,8 @@ class ESP32BLETracker : public Component,
     EXCEEDED_WAIT,  // Timeout exceeded, waiting one loop before reboot
   };
   uint32_t scan_start_time_{0};
+  /// Precomputed timeout value: scan_duration_ * 2000
+  uint32_t scan_timeout_ms_{0};
   ScanTimeoutState scan_timeout_state_{ScanTimeoutState::INACTIVE};
 };
 

esphome/components/esp32_hosted/update/esp32_hosted_update.cpp

@@ -69,10 +69,7 @@ void Esp32HostedUpdate::setup() {
   // Get coprocessor version
   esp_hosted_coprocessor_fwver_t ver_info;
   if (esp_hosted_get_coprocessor_fwversion(&ver_info) == ESP_OK) {
-    // 16 bytes: "255.255.255" (11 chars) + null + safety margin
-    char buf[16];
-    snprintf(buf, sizeof(buf), "%d.%d.%d", ver_info.major1, ver_info.minor1, ver_info.patch1);
-    this->update_info_.current_version = buf;
+    this->update_info_.current_version = str_sprintf("%d.%d.%d", ver_info.major1, ver_info.minor1, ver_info.patch1);
   } else {
     this->update_info_.current_version = "unknown";
   }

esphome/components/esp8266/core.cpp

@@ -6,11 +6,7 @@
 #include "esphome/core/helpers.h"
 #include "preferences.h"
 #include <Arduino.h>
-#include <core_esp8266_features.h>
-
-extern "C" {
-#include <user_interface.h>
-}
+#include <Esp.h>
 
 namespace esphome {
 
@@ -20,19 +16,23 @@ void IRAM_ATTR HOT delay(uint32_t ms) { ::delay(ms); }
 uint32_t IRAM_ATTR HOT micros() { return ::micros(); }
 void IRAM_ATTR HOT delayMicroseconds(uint32_t us) { delay_microseconds_safe(us); }
 void arch_restart() {
-  system_restart();
+  ESP.restart();  // NOLINT(readability-static-accessed-through-instance)
   // restart() doesn't always end execution
   while (true) {  // NOLINT(clang-diagnostic-unreachable-code)
     yield();
   }
 }
 void arch_init() {}
-void IRAM_ATTR HOT arch_feed_wdt() { system_soft_wdt_feed(); }
+void IRAM_ATTR HOT arch_feed_wdt() {
+  ESP.wdtFeed();  // NOLINT(readability-static-accessed-through-instance)
+}
 
 uint8_t progmem_read_byte(const uint8_t *addr) {
   return pgm_read_byte(addr);  // NOLINT
 }
-uint32_t IRAM_ATTR HOT arch_get_cpu_cycle_count() { return esp_get_cycle_count(); }
+uint32_t IRAM_ATTR HOT arch_get_cpu_cycle_count() {
+  return ESP.getCycleCount();  // NOLINT(readability-static-accessed-through-instance)
+}
 uint32_t arch_get_cpu_freq_hz() { return F_CPU; }
 
 void force_link_symbols() {

esphome/components/esp8266/gpio.cpp

@@ -99,7 +99,7 @@ void ESP8266GPIOPin::pin_mode(gpio::Flags flags) {
 }
 
 size_t ESP8266GPIOPin::dump_summary(char *buffer, size_t len) const {
-  return buf_append_printf(buffer, len, 0, "GPIO%u", this->pin_);
+  return snprintf(buffer, len, "GPIO%u", this->pin_);
 }
 
 bool ESP8266GPIOPin::digital_read() {

esphome/components/event/__init__.py

@@ -90,7 +90,9 @@ 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.StringRef, "event_type")], conf)
+        await automation.build_automation(
+            trigger, [(cg.std_string, "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<StringRef> {
+class EventTrigger : public Trigger<std::string> {
  public:
   EventTrigger(Event *event) {
-    event->add_on_event_callback([this](StringRef event_type) { this->trigger(event_type); });
+    event->add_on_event_callback([this](const std::string &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(StringRef(found));
+  this->event_callback_.call(event_type);
 #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(StringRef event_type)> &&callback) {
+void Event::add_on_event_callback(std::function<void(const std::string &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(StringRef event_type)> &&callback);
+  void add_on_event_callback(std::function<void(const std::string &event_type)> &&callback);
 
  protected:
-  LazyCallbackManager<void(StringRef event_type)> event_callback_;
+  LazyCallbackManager<void(const std::string &event_type)> event_callback_;
   FixedVector<const char *> types_;
 
  private:

esphome/components/ezo/ezo.cpp

@@ -160,7 +160,7 @@ void EZOSensor::loop() {
   this->commands_.pop_front();
 }
 
-void EZOSensor::add_command_(const char *command, EzoCommandType command_type, uint16_t delay_ms) {
+void EZOSensor::add_command_(const std::string &command, EzoCommandType command_type, uint16_t delay_ms) {
   std::unique_ptr<EzoCommand> ezo_command(new EzoCommand);
   ezo_command->command = command;
   ezo_command->command_type = command_type;
@@ -169,17 +169,13 @@ void EZOSensor::add_command_(const char *command, EzoCommandType command_type, u
 }
 
 void EZOSensor::set_calibration_point_(EzoCalibrationType type, float value) {
-  // max 21: "Cal,"(4) + type(4) + ","(1) + float(11) + null; use 24 for safety
-  char payload[24];
-  snprintf(payload, sizeof(payload), "Cal,%s,%0.2f", EZO_CALIBRATION_TYPE_STRINGS[type], value);
+  std::string payload = str_sprintf("Cal,%s,%0.2f", EZO_CALIBRATION_TYPE_STRINGS[type], value);
   this->add_command_(payload, EzoCommandType::EZO_CALIBRATION, 900);
 }
 
 void EZOSensor::set_address(uint8_t address) {
   if (address > 0 && address < 128) {
-    // max 8: "I2C,"(4) + uint8(3) + null
-    char payload[8];
-    snprintf(payload, sizeof(payload), "I2C,%u", address);
+    std::string payload = str_sprintf("I2C,%u", address);
     this->new_address_ = address;
     this->add_command_(payload, EzoCommandType::EZO_I2C);
   } else {
@@ -198,9 +194,7 @@ void EZOSensor::get_slope() { this->add_command_("Slope,?", EzoCommandType::EZO_
 void EZOSensor::get_t() { this->add_command_("T,?", EzoCommandType::EZO_T); }
 
 void EZOSensor::set_t(float value) {
-  // max 14 bytes: "T,"(2) + float with "%0.2f" (up to 11 chars) + null(1); use 16 for alignment
-  char payload[16];
-  snprintf(payload, sizeof(payload), "T,%0.2f", value);
+  std::string payload = str_sprintf("T,%0.2f", value);
   this->add_command_(payload, EzoCommandType::EZO_T);
 }
 
@@ -221,9 +215,7 @@ void EZOSensor::set_calibration_point_high(float value) {
 }
 
 void EZOSensor::set_calibration_generic(float value) {
-  // exact 16 bytes: "Cal," (4) + float with "%0.2f" (up to 11 chars, e.g. "-9999999.99") + null (1) = 16
-  char payload[16];
-  snprintf(payload, sizeof(payload), "Cal,%0.2f", value);
+  std::string payload = str_sprintf("Cal,%0.2f", value);
   this->add_command_(payload, EzoCommandType::EZO_CALIBRATION, 900);
 }
 
@@ -231,11 +223,13 @@ void EZOSensor::clear_calibration() { this->add_command_("Cal,clear", EzoCommand
 
 void EZOSensor::get_led_state() { this->add_command_("L,?", EzoCommandType::EZO_LED); }
 
-void EZOSensor::set_led_state(bool on) { this->add_command_(on ? "L,1" : "L,0", EzoCommandType::EZO_LED); }
-
-void EZOSensor::send_custom(const std::string &to_send) {
-  this->add_command_(to_send.c_str(), EzoCommandType::EZO_CUSTOM);
+void EZOSensor::set_led_state(bool on) {
+  std::string to_send = "L,";
+  to_send += on ? "1" : "0";
+  this->add_command_(to_send, EzoCommandType::EZO_LED);
 }
 
+void EZOSensor::send_custom(const std::string &to_send) { this->add_command_(to_send, EzoCommandType::EZO_CUSTOM); }
+
 }  // namespace ezo
 }  // namespace esphome

esphome/components/ezo/ezo.h

@@ -92,7 +92,7 @@ class EZOSensor : public sensor::Sensor, public PollingComponent, public i2c::I2
   std::deque<std::unique_ptr<EzoCommand>> commands_;
   int new_address_;
 
-  void add_command_(const char *command, EzoCommandType command_type, uint16_t delay_ms = 300);
+  void add_command_(const std::string &command, EzoCommandType command_type, uint16_t delay_ms = 300);
 
   void set_calibration_point_(EzoCalibrationType type, float value);
 

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.StringRef)
+    "FanPresetSetTrigger", automation.Trigger.template(cg.std_string)
 )
 
 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.StringRef, "x")], conf)
+        await automation.build_automation(trigger, [(cg.std_string, "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<StringRef> {
+class FanPresetSetTrigger : public Trigger<std::string> {
  public:
   FanPresetSetTrigger(Fan *state) {
     state->add_on_state_callback([this, state]() {
@@ -216,7 +216,7 @@ class FanPresetSetTrigger : public Trigger<StringRef> {
       auto should_trigger = preset_mode != this->last_preset_mode_;
       this->last_preset_mode_ = preset_mode;
       if (should_trigger) {
-        this->trigger(preset_mode);
+        this->trigger(std::string(preset_mode));
       }
     });
     this->last_preset_mode_ = state->get_preset_mode();

esphome/components/gdk101/gdk101.cpp

@@ -163,10 +163,9 @@ bool GDK101Component::read_fw_version_(uint8_t *data) {
       return false;
     }
 
-    // max 8: "255.255" (7 chars) + null
-    char buf[8];
-    snprintf(buf, sizeof(buf), "%d.%d", data[0], data[1]);
-    this->fw_version_text_sensor_->publish_state(buf);
+    const std::string fw_version_str = str_sprintf("%d.%d", data[0], data[1]);
+
+    this->fw_version_text_sensor_->publish_state(fw_version_str);
   }
 #endif  // USE_TEXT_SENSOR
   return true;

esphome/components/homeassistant/number/homeassistant_number.cpp

@@ -97,7 +97,7 @@ void HomeassistantNumber::control(float value) {
   entity_value.key = VALUE_KEY;
   // Stack buffer - no heap allocation; %g produces shortest representation
   char value_buf[16];
-  buf_append_printf(value_buf, sizeof(value_buf), 0, "%g", value);
+  snprintf(value_buf, sizeof(value_buf), "%g", value);
   entity_value.value = StringRef(value_buf);
 
   api::global_api_server->send_homeassistant_action(resp);

esphome/components/i2c/i2c.cpp

@@ -42,8 +42,8 @@ ErrorCode I2CDevice::read_register16(uint16_t a_register, uint8_t *data, size_t
 }
 
 ErrorCode I2CDevice::write_register(uint8_t a_register, const uint8_t *data, size_t len) const {
-  SmallBufferWithHeapFallback<17> buffer_alloc(len + 1);  // Most I2C writes are <= 16 bytes
-  uint8_t *buffer = buffer_alloc.get();
+  SmallBufferWithHeapFallback<17> buffer_alloc;  // Most I2C writes are <= 16 bytes
+  uint8_t *buffer = buffer_alloc.get(len + 1);
 
   buffer[0] = a_register;
   std::copy(data, data + len, buffer + 1);
@@ -51,8 +51,8 @@ ErrorCode I2CDevice::write_register(uint8_t a_register, const uint8_t *data, siz
 }
 
 ErrorCode I2CDevice::write_register16(uint16_t a_register, const uint8_t *data, size_t len) const {
-  SmallBufferWithHeapFallback<18> buffer_alloc(len + 2);  // Most I2C writes are <= 16 bytes + 2 for register
-  uint8_t *buffer = buffer_alloc.get();
+  SmallBufferWithHeapFallback<18> buffer_alloc;  // Most I2C writes are <= 16 bytes + 2 for register
+  uint8_t *buffer = buffer_alloc.get(len + 2);
 
   buffer[0] = a_register >> 8;
   buffer[1] = a_register;

esphome/components/i2c/i2c_bus.h

@@ -11,6 +11,22 @@
 namespace esphome {
 namespace i2c {
 
+/// @brief Helper class for efficient buffer allocation - uses stack for small sizes, heap for large
+template<size_t STACK_SIZE> class SmallBufferWithHeapFallback {
+ public:
+  uint8_t *get(size_t size) {
+    if (size <= STACK_SIZE) {
+      return this->stack_buffer_;
+    }
+    this->heap_buffer_ = std::unique_ptr<uint8_t[]>(new uint8_t[size]);
+    return this->heap_buffer_.get();
+  }
+
+ private:
+  uint8_t stack_buffer_[STACK_SIZE];
+  std::unique_ptr<uint8_t[]> heap_buffer_;
+};
+
 /// @brief Error codes returned by I2CBus and I2CDevice methods
 enum ErrorCode {
   NO_ERROR = 0,                ///< No error found during execution of method
@@ -76,8 +92,8 @@ class I2CBus {
       total_len += read_buffers[i].len;
     }
 
-    SmallBufferWithHeapFallback<128> buffer_alloc(total_len);  // Most I2C reads are small
-    uint8_t *buffer = buffer_alloc.get();
+    SmallBufferWithHeapFallback<128> buffer_alloc;  // Most I2C reads are small
+    uint8_t *buffer = buffer_alloc.get(total_len);
 
     auto err = this->write_readv(address, nullptr, 0, buffer, total_len);
     if (err != ERROR_OK)
@@ -100,8 +116,8 @@ class I2CBus {
       total_len += write_buffers[i].len;
     }
 
-    SmallBufferWithHeapFallback<128> buffer_alloc(total_len);  // Most I2C writes are small
-    uint8_t *buffer = buffer_alloc.get();
+    SmallBufferWithHeapFallback<128> buffer_alloc;  // Most I2C writes are small
+    uint8_t *buffer = buffer_alloc.get(total_len);
 
     size_t pos = 0;
     for (size_t i = 0; i != count; i++) {

esphome/components/max6956/max6956.cpp

@@ -162,7 +162,7 @@ void MAX6956GPIOPin::pin_mode(gpio::Flags flags) { this->parent_->pin_mode(this-
 bool MAX6956GPIOPin::digital_read() { return this->parent_->digital_read(this->pin_) != this->inverted_; }
 void MAX6956GPIOPin::digital_write(bool value) { this->parent_->digital_write(this->pin_, value != this->inverted_); }
 size_t MAX6956GPIOPin::dump_summary(char *buffer, size_t len) const {
-  return buf_append_printf(buffer, len, 0, "%u via Max6956", this->pin_);
+  return snprintf(buffer, len, "%u via Max6956", this->pin_);
 }
 
 }  // namespace max6956

esphome/components/mcp23016/mcp23016.cpp

@@ -100,7 +100,7 @@ void MCP23016GPIOPin::pin_mode(gpio::Flags flags) { this->parent_->pin_mode(this
 bool MCP23016GPIOPin::digital_read() { return this->parent_->digital_read(this->pin_) != this->inverted_; }
 void MCP23016GPIOPin::digital_write(bool value) { this->parent_->digital_write(this->pin_, value != this->inverted_); }
 size_t MCP23016GPIOPin::dump_summary(char *buffer, size_t len) const {
-  return buf_append_printf(buffer, len, 0, "%u via MCP23016", this->pin_);
+  return snprintf(buffer, len, "%u via MCP23016", this->pin_);
 }
 
 }  // namespace mcp23016

esphome/components/mcp23xxx_base/mcp23xxx_base.cpp

@@ -17,7 +17,7 @@ template<uint8_t N> void MCP23XXXGPIOPin<N>::digital_write(bool value) {
   this->parent_->digital_write(this->pin_, value != this->inverted_);
 }
 template<uint8_t N> size_t MCP23XXXGPIOPin<N>::dump_summary(char *buffer, size_t len) const {
-  return buf_append_printf(buffer, len, 0, "%u via MCP23XXX", this->pin_);
+  return snprintf(buffer, len, "%u via MCP23XXX", this->pin_);
 }
 
 template class MCP23XXXGPIOPin<8>;

esphome/components/modbus_controller/modbus_controller.h

@@ -271,31 +271,24 @@ class ServerRegister {
 
   // Formats a raw value into a string representation based on the value type for debugging
   std::string format_value(int64_t value) const {
-    // max 44: float with %.1f can be up to 42 chars (3.4e38 → 39 integer digits + sign + decimal + 1 digit)
-    // plus null terminator = 43, rounded to 44 for 4-byte alignment
-    char buf[44];
     switch (this->value_type) {
       case SensorValueType::U_WORD:
       case SensorValueType::U_DWORD:
       case SensorValueType::U_DWORD_R:
       case SensorValueType::U_QWORD:
       case SensorValueType::U_QWORD_R:
-        buf_append_printf(buf, sizeof(buf), 0, "%" PRIu64, static_cast<uint64_t>(value));
-        return buf;
+        return std::to_string(static_cast<uint64_t>(value));
       case SensorValueType::S_WORD:
       case SensorValueType::S_DWORD:
       case SensorValueType::S_DWORD_R:
       case SensorValueType::S_QWORD:
       case SensorValueType::S_QWORD_R:
-        buf_append_printf(buf, sizeof(buf), 0, "%" PRId64, value);
-        return buf;
+        return std::to_string(value);
       case SensorValueType::FP32_R:
       case SensorValueType::FP32:
-        buf_append_printf(buf, sizeof(buf), 0, "%.1f", bit_cast<float>(static_cast<uint32_t>(value)));
-        return buf;
+        return str_sprintf("%.1f", bit_cast<float>(static_cast<uint32_t>(value)));
       default:
-        buf_append_printf(buf, sizeof(buf), 0, "%" PRId64, value);
-        return buf;
+        return std::to_string(value);
     }
   }
 

esphome/components/modbus_controller/text_sensor/modbus_textsensor.cpp

@@ -16,20 +16,12 @@ void ModbusTextSensor::parse_and_publish(const std::vector<uint8_t> &data) {
   while ((items_left > 0) && index < data.size()) {
     uint8_t b = data[index];
     switch (this->encode_) {
-      case RawEncoding::HEXBYTES: {
-        // max 3: 2 hex digits + null
-        char hex_buf[3];
-        snprintf(hex_buf, sizeof(hex_buf), "%02x", b);
-        output_str += hex_buf;
+      case RawEncoding::HEXBYTES:
+        output_str += str_snprintf("%02x", 2, b);
         break;
-      }
-      case RawEncoding::COMMA: {
-        // max 5: optional ','(1) + uint8(3) + null, for both ",%d" and "%d"
-        char dec_buf[5];
-        snprintf(dec_buf, sizeof(dec_buf), index != this->offset ? ",%d" : "%d", b);
-        output_str += dec_buf;
+      case RawEncoding::COMMA:
+        output_str += str_sprintf(index != this->offset ? ",%d" : "%d", b);
         break;
-      }
       case RawEncoding::ANSI:
         if (b < 0x20)
           break;

esphome/components/mpr121/mpr121.cpp

@@ -154,7 +154,7 @@ void MPR121GPIOPin::digital_write(bool value) {
 }
 
 size_t MPR121GPIOPin::dump_summary(char *buffer, size_t len) const {
-  return buf_append_printf(buffer, len, 0, "ELE%u on MPR121", this->pin_);
+  return snprintf(buffer, len, "ELE%u on MPR121", this->pin_);
 }
 
 }  // namespace mpr121

esphome/components/mqtt/mqtt_alarm_control_panel.cpp

@@ -43,7 +43,7 @@ void MQTTAlarmControlPanelComponent::setup() {
 
 void MQTTAlarmControlPanelComponent::dump_config() {
   ESP_LOGCONFIG(TAG, "MQTT alarm_control_panel '%s':", this->alarm_control_panel_->get_name().c_str());
-  LOG_MQTT_COMPONENT(true, true);
+  LOG_MQTT_COMPONENT(true, true)
   ESP_LOGCONFIG(TAG,
                 "  Supported Features: %" PRIu32 "\n"
                 "  Requires Code to Disarm: %s\n"

esphome/components/mqtt/mqtt_binary_sensor.cpp

@@ -19,7 +19,7 @@ void MQTTBinarySensorComponent::setup() {
 
 void MQTTBinarySensorComponent::dump_config() {
   ESP_LOGCONFIG(TAG, "MQTT Binary Sensor '%s':", this->binary_sensor_->get_name().c_str());
-  LOG_MQTT_COMPONENT(true, false);
+  LOG_MQTT_COMPONENT(true, false)
 }
 MQTTBinarySensorComponent::MQTTBinarySensorComponent(binary_sensor::BinarySensor *binary_sensor)
     : binary_sensor_(binary_sensor) {

esphome/components/mqtt/mqtt_client.cpp

@@ -635,8 +635,7 @@ void MQTTClientComponent::set_log_message_template(MQTTMessage &&message) { this
 const MQTTDiscoveryInfo &MQTTClientComponent::get_discovery_info() const { return this->discovery_info_; }
 void MQTTClientComponent::set_topic_prefix(const std::string &topic_prefix, const std::string &check_topic_prefix) {
   if (App.is_name_add_mac_suffix_enabled() && (topic_prefix == check_topic_prefix)) {
-    char buf[ESPHOME_DEVICE_NAME_MAX_LEN + 1];
-    this->topic_prefix_ = str_sanitize_to(buf, App.get_name().c_str());
+    this->topic_prefix_ = str_sanitize(App.get_name());
   } else {
     this->topic_prefix_ = topic_prefix;
   }

esphome/components/mqtt/mqtt_component.cpp

@@ -27,23 +27,20 @@ inline char *append_char(char *p, char c) {
 // Max lengths for stack-based topic building.
 // These limits are enforced at Python config validation time in mqtt/__init__.py
 // using cv.Length() validators for topic_prefix and discovery_prefix.
-// MQTT_COMPONENT_TYPE_MAX_LEN, MQTT_SUFFIX_MAX_LEN, and MQTT_DEFAULT_TOPIC_MAX_LEN are in mqtt_component.h.
+// MQTT_COMPONENT_TYPE_MAX_LEN and MQTT_SUFFIX_MAX_LEN are defined in mqtt_component.h.
 // ESPHOME_DEVICE_NAME_MAX_LEN and OBJECT_ID_MAX_LEN are defined in entity_base.h.
 // This ensures the stack buffers below are always large enough.
+static constexpr size_t TOPIC_PREFIX_MAX_LEN = 64;      // Validated in Python: cv.Length(max=64)
 static constexpr size_t DISCOVERY_PREFIX_MAX_LEN = 64;  // Validated in Python: cv.Length(max=64)
+
+// Stack buffer sizes - safe because all inputs are length-validated at config time
+// Format: prefix + "/" + type + "/" + object_id + "/" + suffix + null
+static constexpr size_t DEFAULT_TOPIC_MAX_LEN =
+    TOPIC_PREFIX_MAX_LEN + 1 + MQTT_COMPONENT_TYPE_MAX_LEN + 1 + OBJECT_ID_MAX_LEN + 1 + MQTT_SUFFIX_MAX_LEN + 1;
 // Format: prefix + "/" + type + "/" + name + "/" + object_id + "/config" + null
 static constexpr size_t DISCOVERY_TOPIC_MAX_LEN = DISCOVERY_PREFIX_MAX_LEN + 1 + MQTT_COMPONENT_TYPE_MAX_LEN + 1 +
                                                   ESPHOME_DEVICE_NAME_MAX_LEN + 1 + OBJECT_ID_MAX_LEN + 7 + 1;
 
-// Function implementation of LOG_MQTT_COMPONENT macro to reduce code size
-void log_mqtt_component(const char *tag, MQTTComponent *obj, bool state_topic, bool command_topic) {
-  char buf[MQTT_DEFAULT_TOPIC_MAX_LEN];
-  if (state_topic)
-    ESP_LOGCONFIG(tag, "  State Topic: '%s'", obj->get_state_topic_to_(buf).c_str());
-  if (command_topic)
-    ESP_LOGCONFIG(tag, "  Command Topic: '%s'", obj->get_command_topic_to_(buf).c_str());
-}
-
 void MQTTComponent::set_qos(uint8_t qos) { this->qos_ = qos; }
 
 void MQTTComponent::set_subscribe_qos(uint8_t qos) { this->subscribe_qos_ = qos; }
@@ -51,8 +48,7 @@ void MQTTComponent::set_subscribe_qos(uint8_t qos) { this->subscribe_qos_ = qos;
 void MQTTComponent::set_retain(bool retain) { this->retain_ = retain; }
 
 std::string MQTTComponent::get_discovery_topic_(const MQTTDiscoveryInfo &discovery_info) const {
-  char sanitized_name[ESPHOME_DEVICE_NAME_MAX_LEN + 1];
-  str_sanitize_to(sanitized_name, App.get_name().c_str());
+  std::string sanitized_name = str_sanitize(App.get_name());
   const char *comp_type = this->component_type();
   char object_id_buf[OBJECT_ID_MAX_LEN];
   StringRef object_id = this->get_default_object_id_to_(object_id_buf);
@@ -64,7 +60,7 @@ std::string MQTTComponent::get_discovery_topic_(const MQTTDiscoveryInfo &discove
   p = append_char(p, '/');
   p = append_str(p, comp_type, strlen(comp_type));
   p = append_char(p, '/');
-  p = append_str(p, sanitized_name, strlen(sanitized_name));
+  p = append_str(p, sanitized_name.data(), sanitized_name.size());
   p = append_char(p, '/');
   p = append_str(p, object_id.c_str(), object_id.size());
   p = append_str(p, "/config", 7);
@@ -72,18 +68,19 @@ std::string MQTTComponent::get_discovery_topic_(const MQTTDiscoveryInfo &discove
   return std::string(buf, p - buf);
 }
 
-StringRef MQTTComponent::get_default_topic_for_to_(std::span<char, MQTT_DEFAULT_TOPIC_MAX_LEN> buf, const char *suffix,
-                                                   size_t suffix_len) const {
+std::string MQTTComponent::get_default_topic_for_(const std::string &suffix) const {
   const std::string &topic_prefix = global_mqtt_client->get_topic_prefix();
   if (topic_prefix.empty()) {
-    return StringRef();  // Empty topic_prefix means no default topic
+    // If the topic_prefix is null, the default topic should be null
+    return "";
   }
 
   const char *comp_type = this->component_type();
   char object_id_buf[OBJECT_ID_MAX_LEN];
   StringRef object_id = this->get_default_object_id_to_(object_id_buf);
 
-  char *p = buf.data();
+  char buf[DEFAULT_TOPIC_MAX_LEN];
+  char *p = buf;
 
   p = append_str(p, topic_prefix.data(), topic_prefix.size());
   p = append_char(p, '/');
@@ -91,44 +88,21 @@ StringRef MQTTComponent::get_default_topic_for_to_(std::span<char, MQTT_DEFAULT_
   p = append_char(p, '/');
   p = append_str(p, object_id.c_str(), object_id.size());
   p = append_char(p, '/');
-  p = append_str(p, suffix, suffix_len);
-  *p = '\0';
+  p = append_str(p, suffix.data(), suffix.size());
 
-  return StringRef(buf.data(), p - buf.data());
-}
-
-std::string MQTTComponent::get_default_topic_for_(const std::string &suffix) const {
-  char buf[MQTT_DEFAULT_TOPIC_MAX_LEN];
-  StringRef ref = this->get_default_topic_for_to_(buf, suffix.data(), suffix.size());
-  return std::string(ref.c_str(), ref.size());
-}
-
-StringRef MQTTComponent::get_state_topic_to_(std::span<char, MQTT_DEFAULT_TOPIC_MAX_LEN> buf) const {
-  if (this->custom_state_topic_.has_value()) {
-    // Returns ref to existing data for static/value, uses buf only for lambda case
-    return this->custom_state_topic_.ref_or_copy_to(buf.data(), buf.size());
-  }
-  return this->get_default_topic_for_to_(buf, "state", 5);
-}
-
-StringRef MQTTComponent::get_command_topic_to_(std::span<char, MQTT_DEFAULT_TOPIC_MAX_LEN> buf) const {
-  if (this->custom_command_topic_.has_value()) {
-    // Returns ref to existing data for static/value, uses buf only for lambda case
-    return this->custom_command_topic_.ref_or_copy_to(buf.data(), buf.size());
-  }
-  return this->get_default_topic_for_to_(buf, "command", 7);
+  return std::string(buf, p - buf);
 }
 
 std::string MQTTComponent::get_state_topic_() const {
-  char buf[MQTT_DEFAULT_TOPIC_MAX_LEN];
-  StringRef ref = this->get_state_topic_to_(buf);
-  return std::string(ref.c_str(), ref.size());
+  if (this->custom_state_topic_.has_value())
+    return this->custom_state_topic_.value();
+  return this->get_default_topic_for_("state");
 }
 
 std::string MQTTComponent::get_command_topic_() const {
-  char buf[MQTT_DEFAULT_TOPIC_MAX_LEN];
-  StringRef ref = this->get_command_topic_to_(buf);
-  return std::string(ref.c_str(), ref.size());
+  if (this->custom_command_topic_.has_value())
+    return this->custom_command_topic_.value();
+  return this->get_default_topic_for_("command");
 }
 
 bool MQTTComponent::publish(const std::string &topic, const std::string &payload) {
@@ -193,14 +167,10 @@ bool MQTTComponent::send_discovery_() {
             break;
         }
 
-        if (config.state_topic) {
-          char state_topic_buf[MQTT_DEFAULT_TOPIC_MAX_LEN];
-          root[MQTT_STATE_TOPIC] = this->get_state_topic_to_(state_topic_buf);
-        }
-        if (config.command_topic) {
-          char command_topic_buf[MQTT_DEFAULT_TOPIC_MAX_LEN];
-          root[MQTT_COMMAND_TOPIC] = this->get_command_topic_to_(command_topic_buf);
-        }
+        if (config.state_topic)
+          root[MQTT_STATE_TOPIC] = this->get_state_topic_();
+        if (config.command_topic)
+          root[MQTT_COMMAND_TOPIC] = this->get_command_topic_();
         if (this->command_retain_)
           root[MQTT_COMMAND_RETAIN] = true;
 
@@ -317,9 +287,7 @@ void MQTTComponent::set_availability(std::string topic, std::string payload_avai
 }
 void MQTTComponent::disable_availability() { this->set_availability("", "", ""); }
 void MQTTComponent::call_setup() {
-  // Cache is_internal result once during setup - topics don't change after this
-  this->is_internal_ = this->compute_is_internal_();
-  if (this->is_internal_)
+  if (this->is_internal())
     return;
 
   this->setup();
@@ -375,28 +343,26 @@ StringRef MQTTComponent::get_default_object_id_to_(std::span<char, OBJECT_ID_MAX
 }
 StringRef MQTTComponent::get_icon_ref_() const { return this->get_entity()->get_icon_ref(); }
 bool MQTTComponent::is_disabled_by_default_() const { return this->get_entity()->is_disabled_by_default(); }
-bool MQTTComponent::compute_is_internal_() {
+bool MQTTComponent::is_internal() {
   if (this->custom_state_topic_.has_value()) {
-    // If the custom state_topic is empty, return true as it is internal and should not publish
+    // If the custom state_topic is null, return true as it is internal and should not publish
     // else, return false, as it is explicitly set to a topic, so it is not internal and should publish
-    // Using is_empty() avoids heap allocation for non-lambda cases
-    return this->custom_state_topic_.is_empty();
+    return this->get_state_topic_().empty();
   }
 
   if (this->custom_command_topic_.has_value()) {
-    // If the custom command_topic is empty, return true as it is internal and should not publish
+    // If the custom command_topic is null, return true as it is internal and should not publish
     // else, return false, as it is explicitly set to a topic, so it is not internal and should publish
-    // Using is_empty() avoids heap allocation for non-lambda cases
-    return this->custom_command_topic_.is_empty();
+    return this->get_command_topic_().empty();
   }
 
-  // No custom topics have been set - check topic_prefix directly to avoid allocation
-  if (global_mqtt_client->get_topic_prefix().empty()) {
-    // If the default topic prefix is empty, then the component, by default, is internal and should not publish
+  // No custom topics have been set
+  if (this->get_default_topic_for_("").empty()) {
+    // If the default topic prefix is null, then the component, by default, is internal and should not publish
     return true;
   }
 
-  // Use ESPHome's component internal state if topic_prefix is not empty with no custom state_topic or command_topic
+  // Use ESPHome's component internal state if topic_prefix is not null with no custom state_topic or command_topic
   return this->get_entity()->is_internal();
 }
 

esphome/components/mqtt/mqtt_component.h

@@ -20,22 +20,17 @@ struct SendDiscoveryConfig {
   bool command_topic{true};  ///< If the command topic should be included. Default to true.
 };
 
-// Max lengths for stack-based topic building.
-// These limits are enforced at Python config validation time in mqtt/__init__.py
-// using cv.Length() validators for topic_prefix and discovery_prefix.
-// This ensures the stack buffers are always large enough.
+// Max lengths for stack-based topic building (must match mqtt_component.cpp)
 static constexpr size_t MQTT_COMPONENT_TYPE_MAX_LEN = 20;
 static constexpr size_t MQTT_SUFFIX_MAX_LEN = 32;
-static constexpr size_t MQTT_TOPIC_PREFIX_MAX_LEN = 64;  // Validated in Python: cv.Length(max=64)
-// Stack buffer size - safe because all inputs are length-validated at config time
-// Format: prefix + "/" + type + "/" + object_id + "/" + suffix + null
-static constexpr size_t MQTT_DEFAULT_TOPIC_MAX_LEN =
-    MQTT_TOPIC_PREFIX_MAX_LEN + 1 + MQTT_COMPONENT_TYPE_MAX_LEN + 1 + OBJECT_ID_MAX_LEN + 1 + MQTT_SUFFIX_MAX_LEN + 1;
 
-class MQTTComponent;  // Forward declaration
-void log_mqtt_component(const char *tag, MQTTComponent *obj, bool state_topic, bool command_topic);
-
-#define LOG_MQTT_COMPONENT(state_topic, command_topic) log_mqtt_component(TAG, this, state_topic, command_topic)
+#define LOG_MQTT_COMPONENT(state_topic, command_topic) \
+  if (state_topic) { \
+    ESP_LOGCONFIG(TAG, "  State Topic: '%s'", this->get_state_topic_().c_str()); \
+  } \
+  if (command_topic) { \
+    ESP_LOGCONFIG(TAG, "  Command Topic: '%s'", this->get_command_topic_().c_str()); \
+  }
 
 // Macro to define component_type() with compile-time length verification
 // Usage: MQTT_COMPONENT_TYPE(MQTTSensorComponent, "sensor")
@@ -79,8 +74,6 @@ void log_mqtt_component(const char *tag, MQTTComponent *obj, bool state_topic, b
  * a clean separation.
  */
 class MQTTComponent : public Component {
-  friend void log_mqtt_component(const char *tag, MQTTComponent *obj, bool state_topic, bool command_topic);
-
  public:
   /// Constructs a MQTTComponent.
   explicit MQTTComponent();
@@ -97,8 +90,7 @@ class MQTTComponent : public Component {
 
   virtual bool send_initial_state() = 0;
 
-  /// Returns cached is_internal result (computed once during setup).
-  bool is_internal() const { return this->is_internal_; }
+  virtual bool is_internal();
 
   /// Set QOS for state messages.
   void set_qos(uint8_t qos);
@@ -186,16 +178,7 @@ class MQTTComponent : public Component {
   /// Helper method to get the discovery topic for this component.
   std::string get_discovery_topic_(const MQTTDiscoveryInfo &discovery_info) const;
 
-  /** Get this components state/command/... topic into a buffer.
-   *
-   * @param buf The buffer to write to (must be exactly MQTT_DEFAULT_TOPIC_MAX_LEN).
-   * @param suffix The suffix/key such as "state" or "command".
-   * @return StringRef pointing to the buffer with the topic.
-   */
-  StringRef get_default_topic_for_to_(std::span<char, MQTT_DEFAULT_TOPIC_MAX_LEN> buf, const char *suffix,
-                                      size_t suffix_len) const;
-
-  /** Get this components state/command/... topic (allocates std::string).
+  /** Get this components state/command/... topic.
    *
    * @param suffix The suffix/key such as "state" or "command".
    * @return The full topic.
@@ -216,20 +199,10 @@ class MQTTComponent : public Component {
   /// Get whether the underlying Entity is disabled by default
   bool is_disabled_by_default_() const;
 
-  /// Get the MQTT state topic into a buffer (no heap allocation for non-lambda custom topics).
-  /// @param buf Buffer of exactly MQTT_DEFAULT_TOPIC_MAX_LEN bytes.
-  /// @return StringRef pointing to the topic in the buffer.
-  StringRef get_state_topic_to_(std::span<char, MQTT_DEFAULT_TOPIC_MAX_LEN> buf) const;
-
-  /// Get the MQTT command topic into a buffer (no heap allocation for non-lambda custom topics).
-  /// @param buf Buffer of exactly MQTT_DEFAULT_TOPIC_MAX_LEN bytes.
-  /// @return StringRef pointing to the topic in the buffer.
-  StringRef get_command_topic_to_(std::span<char, MQTT_DEFAULT_TOPIC_MAX_LEN> buf) const;
-
-  /// Get the MQTT topic that new states will be shared to (allocates std::string).
+  /// Get the MQTT topic that new states will be shared to.
   std::string get_state_topic_() const;
 
-  /// Get the MQTT topic for listening to commands (allocates std::string).
+  /// Get the MQTT topic for listening to commands.
   std::string get_command_topic_() const;
 
   bool is_connected_() const;
@@ -247,18 +220,12 @@ class MQTTComponent : public Component {
 
   std::unique_ptr<Availability> availability_;
 
-  // Packed bitfields - QoS values are 0-2, bools are flags
-  uint8_t qos_ : 2 {0};
-  uint8_t subscribe_qos_ : 2 {0};
-  bool command_retain_ : 1 {false};
-  bool retain_ : 1 {true};
-  bool discovery_enabled_ : 1 {true};
-  bool resend_state_ : 1 {false};
-  bool is_internal_ : 1 {false};  ///< Cached result of compute_is_internal_(), set during setup
-
-  /// Compute is_internal status based on topics and entity state.
-  /// Called once during setup to cache the result.
-  bool compute_is_internal_();
+  bool command_retain_{false};
+  bool retain_{true};
+  uint8_t qos_{0};
+  uint8_t subscribe_qos_{0};
+  bool discovery_enabled_{true};
+  bool resend_state_{false};
 };
 
 }  // namespace esphome::mqtt

esphome/components/mqtt/mqtt_cover.cpp

@@ -51,7 +51,7 @@ void MQTTCoverComponent::dump_config() {
   ESP_LOGCONFIG(TAG, "MQTT cover '%s':", this->cover_->get_name().c_str());
   auto traits = this->cover_->get_traits();
   bool has_command_topic = traits.get_supports_position() || !traits.get_supports_tilt();
-  LOG_MQTT_COMPONENT(true, has_command_topic);
+  LOG_MQTT_COMPONENT(true, has_command_topic)
   if (traits.get_supports_position()) {
     ESP_LOGCONFIG(TAG,
                   "  Position State Topic: '%s'\n"

esphome/components/mqtt/mqtt_date.cpp

@@ -36,7 +36,7 @@ void MQTTDateComponent::setup() {
 
 void MQTTDateComponent::dump_config() {
   ESP_LOGCONFIG(TAG, "MQTT Date '%s':", this->date_->get_name().c_str());
-  LOG_MQTT_COMPONENT(true, true);
+  LOG_MQTT_COMPONENT(true, true)
 }
 
 MQTT_COMPONENT_TYPE(MQTTDateComponent, "date")

esphome/components/mqtt/mqtt_datetime.cpp

@@ -47,7 +47,7 @@ void MQTTDateTimeComponent::setup() {
 
 void MQTTDateTimeComponent::dump_config() {
   ESP_LOGCONFIG(TAG, "MQTT DateTime '%s':", this->datetime_->get_name().c_str());
-  LOG_MQTT_COMPONENT(true, true);
+  LOG_MQTT_COMPONENT(true, true)
 }
 
 MQTT_COMPONENT_TYPE(MQTTDateTimeComponent, "datetime")

esphome/components/mqtt/mqtt_light.cpp

@@ -90,7 +90,7 @@ void MQTTJSONLightComponent::send_discovery(JsonObject root, mqtt::SendDiscovery
 bool MQTTJSONLightComponent::send_initial_state() { return this->publish_state_(); }
 void MQTTJSONLightComponent::dump_config() {
   ESP_LOGCONFIG(TAG, "MQTT Light '%s':", this->state_->get_name().c_str());
-  LOG_MQTT_COMPONENT(true, true);
+  LOG_MQTT_COMPONENT(true, true)
 }
 
 }  // namespace esphome::mqtt

esphome/components/mqtt/mqtt_number.cpp

@@ -30,7 +30,7 @@ void MQTTNumberComponent::setup() {
 
 void MQTTNumberComponent::dump_config() {
   ESP_LOGCONFIG(TAG, "MQTT Number '%s':", this->number_->get_name().c_str());
-  LOG_MQTT_COMPONENT(true, false);
+  LOG_MQTT_COMPONENT(true, false)
 }
 
 MQTT_COMPONENT_TYPE(MQTTNumberComponent, "number")

esphome/components/mqtt/mqtt_select.cpp

@@ -25,7 +25,7 @@ void MQTTSelectComponent::setup() {
 
 void MQTTSelectComponent::dump_config() {
   ESP_LOGCONFIG(TAG, "MQTT Select '%s':", this->select_->get_name().c_str());
-  LOG_MQTT_COMPONENT(true, false);
+  LOG_MQTT_COMPONENT(true, false)
 }
 
 MQTT_COMPONENT_TYPE(MQTTSelectComponent, "select")

esphome/components/mqtt/mqtt_sensor.cpp

@@ -28,7 +28,7 @@ void MQTTSensorComponent::dump_config() {
   if (this->get_expire_after() > 0) {
     ESP_LOGCONFIG(TAG, "  Expire After: %" PRIu32 "s", this->get_expire_after() / 1000);
   }
-  LOG_MQTT_COMPONENT(true, false);
+  LOG_MQTT_COMPONENT(true, false)
 }
 
 MQTT_COMPONENT_TYPE(MQTTSensorComponent, "sensor")

esphome/components/mqtt/mqtt_text.cpp

@@ -26,7 +26,7 @@ void MQTTTextComponent::setup() {
 
 void MQTTTextComponent::dump_config() {
   ESP_LOGCONFIG(TAG, "MQTT text '%s':", this->text_->get_name().c_str());
-  LOG_MQTT_COMPONENT(true, true);
+  LOG_MQTT_COMPONENT(true, true)
 }
 
 MQTT_COMPONENT_TYPE(MQTTTextComponent, "text")

esphome/components/mqtt/mqtt_time.cpp

@@ -36,7 +36,7 @@ void MQTTTimeComponent::setup() {
 
 void MQTTTimeComponent::dump_config() {
   ESP_LOGCONFIG(TAG, "MQTT Time '%s':", this->time_->get_name().c_str());
-  LOG_MQTT_COMPONENT(true, true);
+  LOG_MQTT_COMPONENT(true, true)
 }
 
 MQTT_COMPONENT_TYPE(MQTTTimeComponent, "time")

esphome/components/mqtt/mqtt_valve.cpp

@@ -39,7 +39,7 @@ void MQTTValveComponent::dump_config() {
   ESP_LOGCONFIG(TAG, "MQTT valve '%s':", this->valve_->get_name().c_str());
   auto traits = this->valve_->get_traits();
   bool has_command_topic = traits.get_supports_position();
-  LOG_MQTT_COMPONENT(true, has_command_topic);
+  LOG_MQTT_COMPONENT(true, has_command_topic)
   if (traits.get_supports_position()) {
     ESP_LOGCONFIG(TAG,
                   "  Position State Topic: '%s'\n"

esphome/components/network/ip_address.h

@@ -43,14 +43,6 @@ namespace network {
 /// Buffer size for IP address string (IPv6 max: 39 chars + null)
 static constexpr size_t IP_ADDRESS_BUFFER_SIZE = 40;
 
-/// Lowercase hex digits in IP address string (A-F -> a-f for IPv6 per RFC 5952)
-inline void lowercase_ip_str(char *buf) {
-  for (char *p = buf; *p; ++p) {
-    if (*p >= 'A' && *p <= 'F')
-      *p += 32;
-  }
-}
-
 struct IPAddress {
  public:
 #ifdef USE_HOST
@@ -60,15 +52,10 @@ 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; }
-  std::string str() const {
-    char buf[IP_ADDRESS_BUFFER_SIZE];
-    this->str_to(buf);
-    return buf;
-  }
+  std::string str() const { return str_lower_case(inet_ntoa(ip_addr_)); }
   /// Write IP address to buffer. Buffer must be at least IP_ADDRESS_BUFFER_SIZE bytes.
   char *str_to(char *buf) const {
-    inet_ntop(AF_INET, &ip_addr_, buf, IP_ADDRESS_BUFFER_SIZE);
-    return buf;  // IPv4 only, no hex letters to lowercase
+    return const_cast<char *>(inet_ntop(AF_INET, &ip_addr_, buf, IP_ADDRESS_BUFFER_SIZE));
   }
 #else
   IPAddress() { ip_addr_set_zero(&ip_addr_); }
@@ -147,18 +134,9 @@ 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_); }
-  std::string str() const {
-    char buf[IP_ADDRESS_BUFFER_SIZE];
-    this->str_to(buf);
-    return buf;
-  }
+  std::string str() const { return str_lower_case(ipaddr_ntoa(&ip_addr_)); }
   /// Write IP address to buffer. Buffer must be at least IP_ADDRESS_BUFFER_SIZE bytes.
-  /// Output is lowercased per RFC 5952 (IPv6 hex digits a-f).
-  char *str_to(char *buf) const {
-    ipaddr_ntoa_r(&ip_addr_, buf, IP_ADDRESS_BUFFER_SIZE);
-    lowercase_ip_str(buf);
-    return buf;
-  }
+  char *str_to(char *buf) const { return ipaddr_ntoa_r(&ip_addr_, buf, IP_ADDRESS_BUFFER_SIZE); }
   bool operator==(const IPAddress &other) const { return ip_addr_cmp(&ip_addr_, &other.ip_addr_); }
   bool operator!=(const IPAddress &other) const { return !ip_addr_cmp(&ip_addr_, &other.ip_addr_); }
   IPAddress &operator+=(uint8_t increase) {

esphome/components/nextion/nextion.cpp

@@ -1,7 +1,6 @@
 #include "nextion.h"
 #include <cinttypes>
 #include "esphome/core/application.h"
-#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 #include "esphome/core/util.h"
 
@@ -1284,9 +1283,8 @@ void Nextion::check_pending_waveform_() {
   size_t buffer_to_send = component->get_wave_buffer_size() < 255 ? component->get_wave_buffer_size()
                                                                   : 255;  // ADDT command can only send 255
 
-  char command[24];  // "addt " + uint8 + "," + uint8 + "," + uint8 + null = max 17 chars
-  buf_append_printf(command, sizeof(command), 0, "addt %u,%u,%zu", component->get_component_id(),
-                    component->get_wave_channel_id(), buffer_to_send);
+  std::string command = "addt " + to_string(component->get_component_id()) + "," +
+                        to_string(component->get_wave_channel_id()) + "," + to_string(buffer_to_send);
   if (!this->send_command_(command)) {
     delete nb;  // NOLINT(cppcoreguidelines-owning-memory)
     this->waveform_queue_.pop_front();

esphome/components/nextion/nextion_upload_arduino.cpp

@@ -34,7 +34,7 @@ int Nextion::upload_by_chunks_(HTTPClient &http_client, uint32_t &range_start) {
   }
 
   char range_header[32];
-  buf_append_printf(range_header, sizeof(range_header), 0, "bytes=%" PRIu32 "-%" PRIu32, range_start, range_end);
+  sprintf(range_header, "bytes=%" PRIu32 "-%" PRIu32, range_start, range_end);
   ESP_LOGV(TAG, "Range: %s", range_header);
   http_client.addHeader("Range", range_header);
   int code = http_client.GET();

esphome/components/nextion/nextion_upload_esp32.cpp

@@ -36,7 +36,7 @@ int Nextion::upload_by_chunks_(esp_http_client_handle_t http_client, uint32_t &r
   }
 
   char range_header[32];
-  buf_append_printf(range_header, sizeof(range_header), 0, "bytes=%" PRIu32 "-%" PRIu32, range_start, range_end);
+  sprintf(range_header, "bytes=%" PRIu32 "-%" PRIu32, range_start, range_end);
   ESP_LOGV(TAG, "Range: %s", range_header);
   esp_http_client_set_header(http_client, "Range", range_header);
   ESP_LOGV(TAG, "Open HTTP");

esphome/components/pca6416a/pca6416a.cpp

@@ -181,7 +181,7 @@ void PCA6416AGPIOPin::pin_mode(gpio::Flags flags) { this->parent_->pin_mode(this
 bool PCA6416AGPIOPin::digital_read() { return this->parent_->digital_read(this->pin_) != this->inverted_; }
 void PCA6416AGPIOPin::digital_write(bool value) { this->parent_->digital_write(this->pin_, value != this->inverted_); }
 size_t PCA6416AGPIOPin::dump_summary(char *buffer, size_t len) const {
-  return buf_append_printf(buffer, len, 0, "%u via PCA6416A", this->pin_);
+  return snprintf(buffer, len, "%u via PCA6416A", this->pin_);
 }
 
 }  // namespace pca6416a

esphome/components/pca9554/pca9554.cpp

@@ -130,7 +130,7 @@ void PCA9554GPIOPin::pin_mode(gpio::Flags flags) { this->parent_->pin_mode(this-
 bool PCA9554GPIOPin::digital_read() { return this->parent_->digital_read(this->pin_) != this->inverted_; }
 void PCA9554GPIOPin::digital_write(bool value) { this->parent_->digital_write(this->pin_, value != this->inverted_); }
 size_t PCA9554GPIOPin::dump_summary(char *buffer, size_t len) const {
-  return buf_append_printf(buffer, len, 0, "%u via PCA9554", this->pin_);
+  return snprintf(buffer, len, "%u via PCA9554", this->pin_);
 }
 
 }  // namespace pca9554

esphome/components/pcf8574/pcf8574.cpp

@@ -107,7 +107,7 @@ void PCF8574GPIOPin::pin_mode(gpio::Flags flags) { this->parent_->pin_mode(this-
 bool PCF8574GPIOPin::digital_read() { return this->parent_->digital_read(this->pin_) != this->inverted_; }
 void PCF8574GPIOPin::digital_write(bool value) { this->parent_->digital_write(this->pin_, value != this->inverted_); }
 size_t PCF8574GPIOPin::dump_summary(char *buffer, size_t len) const {
-  return buf_append_printf(buffer, len, 0, "%u via PCF8574", this->pin_);
+  return snprintf(buffer, len, "%u via PCF8574", this->pin_);
 }
 
 }  // namespace pcf8574

esphome/components/pi4ioe5v6408/pi4ioe5v6408.cpp

@@ -165,7 +165,7 @@ void PI4IOE5V6408GPIOPin::digital_write(bool value) {
   this->parent_->digital_write(this->pin_, value != this->inverted_);
 }
 size_t PI4IOE5V6408GPIOPin::dump_summary(char *buffer, size_t len) const {
-  return buf_append_printf(buffer, len, 0, "%u via PI4IOE5V6408", this->pin_);
+  return snprintf(buffer, len, "%u via PI4IOE5V6408", this->pin_);
 }
 
 }  // namespace pi4ioe5v6408

esphome/components/pipsolar/output/pipsolar_output.cpp

@@ -8,8 +8,8 @@ namespace pipsolar {
 static const char *const TAG = "pipsolar.output";
 
 void PipsolarOutput::write_state(float state) {
-  char tmp[16];
-  snprintf(tmp, sizeof(tmp), this->set_command_, state);
+  char tmp[10];
+  sprintf(tmp, this->set_command_.c_str(), state);
 
   if (std::find(this->possible_values_.begin(), this->possible_values_.end(), state) != this->possible_values_.end()) {
     ESP_LOGD(TAG, "Will write: %s out of value %f / %02.0f", tmp, state, state);

esphome/components/pipsolar/output/pipsolar_output.h

@@ -15,15 +15,13 @@ class PipsolarOutput : public output::FloatOutput {
  public:
   PipsolarOutput() {}
   void set_parent(Pipsolar *parent) { this->parent_ = parent; }
-  void set_set_command(const char *command) { this->set_command_ = command; }
-  /// Prevent accidental use of std::string which would dangle
-  void set_set_command(const std::string &command) = delete;
+  void set_set_command(const std::string &command) { this->set_command_ = command; };
   void set_possible_values(std::vector<float> possible_values) { this->possible_values_ = std::move(possible_values); }
-  void set_value(float value) { this->write_state(value); }
+  void set_value(float value) { this->write_state(value); };
 
  protected:
   void write_state(float state) override;
-  const char *set_command_{nullptr};
+  std::string set_command_;
   Pipsolar *parent_;
   std::vector<float> possible_values_;
 };

esphome/components/pipsolar/switch/pipsolar_switch.cpp

@@ -9,9 +9,14 @@ static const char *const TAG = "pipsolar.switch";
 
 void PipsolarSwitch::dump_config() { LOG_SWITCH("", "Pipsolar Switch", this); }
 void PipsolarSwitch::write_state(bool state) {
-  const char *command = state ? this->on_command_ : this->off_command_;
-  if (command != nullptr) {
-    this->parent_->queue_command(command);
+  if (state) {
+    if (!this->on_command_.empty()) {
+      this->parent_->queue_command(this->on_command_);
+    }
+  } else {
+    if (!this->off_command_.empty()) {
+      this->parent_->queue_command(this->off_command_);
+    }
   }
 }
 

esphome/components/pipsolar/switch/pipsolar_switch.h

@@ -9,18 +9,15 @@ namespace pipsolar {
 class Pipsolar;
 class PipsolarSwitch : public switch_::Switch, public Component {
  public:
-  void set_parent(Pipsolar *parent) { this->parent_ = parent; }
-  void set_on_command(const char *command) { this->on_command_ = command; }
-  void set_off_command(const char *command) { this->off_command_ = command; }
-  /// Prevent accidental use of std::string which would dangle
-  void set_on_command(const std::string &command) = delete;
-  void set_off_command(const std::string &command) = delete;
+  void set_parent(Pipsolar *parent) { this->parent_ = parent; };
+  void set_on_command(const std::string &command) { this->on_command_ = command; };
+  void set_off_command(const std::string &command) { this->off_command_ = command; };
   void dump_config() override;
 
  protected:
   void write_state(bool state) override;
-  const char *on_command_{nullptr};
-  const char *off_command_{nullptr};
+  std::string on_command_;
+  std::string off_command_;
   Pipsolar *parent_;
 };
 

esphome/components/rc522_spi/rc522_spi.cpp

@@ -1,5 +1,4 @@
 #include "rc522_spi.h"
-#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 
 // Based on:
@@ -71,7 +70,7 @@ void RC522Spi::pcd_read_register(PcdRegister reg,  ///< The register to read fro
     index++;
 
 #ifdef ESPHOME_LOG_HAS_VERY_VERBOSE
-    buf_append_printf(cstrb, sizeof(cstrb), 0, " %x", values[0]);
+    sprintf(cstrb, " %x", values[0]);
     buf.append(cstrb);
 #endif
   }
@@ -79,7 +78,7 @@ void RC522Spi::pcd_read_register(PcdRegister reg,  ///< The register to read fro
     values[index] = transfer_byte(address);  // Read value and tell that we want to read the same address again.
 
 #ifdef ESPHOME_LOG_HAS_VERY_VERBOSE
-    buf_append_printf(cstrb, sizeof(cstrb), 0, " %x", values[index]);
+    sprintf(cstrb, " %x", values[index]);
     buf.append(cstrb);
 #endif
 
@@ -89,7 +88,7 @@ void RC522Spi::pcd_read_register(PcdRegister reg,  ///< The register to read fro
 
 #ifdef ESPHOME_LOG_HAS_VERY_VERBOSE
   buf = buf + " ";
-  buf_append_printf(cstrb, sizeof(cstrb), 0, "%x", values[index]);
+  sprintf(cstrb, "%x", values[index]);
   buf.append(cstrb);
 
   ESP_LOGVV(TAG, "read_register_array_(%x, %d, , %d) -> %s", reg, count, rx_align, buf.c_str());
@@ -128,7 +127,7 @@ void RC522Spi::pcd_write_register(PcdRegister reg,  ///< The register to write t
     transfer_byte(values[index]);
 
 #ifdef ESPHOME_LOG_HAS_VERY_VERBOSE
-    buf_append_printf(cstrb, sizeof(cstrb), 0, " %x", values[index]);
+    sprintf(cstrb, " %x", values[index]);
     buf.append(cstrb);
 #endif
   }

esphome/components/select/__init__.py

@@ -33,7 +33,7 @@ SelectPtr = Select.operator("ptr")
 # Triggers
 SelectStateTrigger = select_ns.class_(
     "SelectStateTrigger",
-    automation.Trigger.template(cg.StringRef, cg.size_t),
+    automation.Trigger.template(cg.std_string, 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.StringRef, "x"), (cg.size_t, "i")], conf
+            trigger, [(cg.std_string, "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<StringRef, size_t> {
+class SelectStateTrigger : public Trigger<std::string, size_t> {
  public:
   explicit SelectStateTrigger(Select *parent) : parent_(parent) {
     parent->add_on_state_callback(
-        [this](size_t index) { this->trigger(StringRef(this->parent_->option_at(index)), index); });
+        [this](size_t index) { this->trigger(std::string(this->parent_->option_at(index)), index); });
   }
 
  protected:

esphome/components/sim800l/sim800l.cpp

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

esphome/components/sml/sml_parser.cpp

@@ -104,10 +104,7 @@ std::vector<ObisInfo> SmlFile::get_obis_info() {
 std::string bytes_repr(const BytesView &buffer) {
   std::string repr;
   for (auto const value : buffer) {
-    // max 3: 2 hex digits + null
-    char hex_buf[3];
-    snprintf(hex_buf, sizeof(hex_buf), "%02x", static_cast<unsigned int>(value));
-    repr += hex_buf;
+    repr += str_sprintf("%02x", value & 0xff);
   }
   return repr;
 }
@@ -149,11 +146,7 @@ ObisInfo::ObisInfo(const BytesView &server_id, const SmlNode &val_list_entry) :
 }
 
 std::string ObisInfo::code_repr() const {
-  // max 20: "255-255:255.255.255" (19 chars) + null
-  char buf[20];
-  snprintf(buf, sizeof(buf), "%d-%d:%d.%d.%d", this->code[0], this->code[1], this->code[2], this->code[3],
-           this->code[4]);
-  return buf;
+  return str_sprintf("%d-%d:%d.%d.%d", this->code[0], this->code[1], this->code[2], this->code[3], this->code[4]);
 }
 
 }  // namespace sml

esphome/components/sn74hc165/sn74hc165.cpp

@@ -65,7 +65,7 @@ float SN74HC165Component::get_setup_priority() const { return setup_priority::IO
 bool SN74HC165GPIOPin::digital_read() { return this->parent_->digital_read_(this->pin_) != this->inverted_; }
 
 size_t SN74HC165GPIOPin::dump_summary(char *buffer, size_t len) const {
-  return buf_append_printf(buffer, len, 0, "%u via SN74HC165", this->pin_);
+  return snprintf(buffer, len, "%u via SN74HC165", this->pin_);
 }
 
 }  // namespace sn74hc165

esphome/components/sn74hc595/sn74hc595.cpp

@@ -94,7 +94,7 @@ void SN74HC595GPIOPin::digital_write(bool value) {
   this->parent_->digital_write_(this->pin_, value != this->inverted_);
 }
 size_t SN74HC595GPIOPin::dump_summary(char *buffer, size_t len) const {
-  return buf_append_printf(buffer, len, 0, "%u via SN74HC595", this->pin_);
+  return snprintf(buffer, len, "%u via SN74HC595", this->pin_);
 }
 
 }  // namespace sn74hc595

esphome/components/socket/socket.cpp

@@ -107,9 +107,9 @@ std::unique_ptr<Socket> socket_ip_loop_monitored(int type, int protocol) {
 #endif /* USE_NETWORK_IPV6 */
 }
 
-socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const char *ip_address, uint16_t port) {
+socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const std::string &ip_address, uint16_t port) {
 #if USE_NETWORK_IPV6
-  if (strchr(ip_address, ':') != nullptr) {
+  if (ip_address.find(':') != std::string::npos) {
     if (addrlen < sizeof(sockaddr_in6)) {
       errno = EINVAL;
       return 0;
@@ -121,14 +121,14 @@ socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const char *ip_
 
 #ifdef USE_SOCKET_IMPL_BSD_SOCKETS
     // Use standard inet_pton for BSD sockets
-    if (inet_pton(AF_INET6, ip_address, &server->sin6_addr) != 1) {
+    if (inet_pton(AF_INET6, ip_address.c_str(), &server->sin6_addr) != 1) {
       errno = EINVAL;
       return 0;
     }
 #else
     // Use LWIP-specific functions
     ip6_addr_t ip6;
-    inet6_aton(ip_address, &ip6);
+    inet6_aton(ip_address.c_str(), &ip6);
     memcpy(server->sin6_addr.un.u32_addr, ip6.addr, sizeof(ip6.addr));
 #endif
     return sizeof(sockaddr_in6);
@@ -141,7 +141,7 @@ socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const char *ip_
   auto *server = reinterpret_cast<sockaddr_in *>(addr);
   memset(server, 0, sizeof(sockaddr_in));
   server->sin_family = AF_INET;
-  server->sin_addr.s_addr = inet_addr(ip_address);
+  server->sin_addr.s_addr = inet_addr(ip_address.c_str());
   server->sin_port = htons(port);
   return sizeof(sockaddr_in);
 }

esphome/components/socket/socket.h

@@ -87,17 +87,7 @@ std::unique_ptr<Socket> socket_loop_monitored(int domain, int type, int protocol
 std::unique_ptr<Socket> socket_ip_loop_monitored(int type, int protocol);
 
 /// Set a sockaddr to the specified address and port for the IP version used by socket_ip().
-/// @param addr Destination sockaddr structure
-/// @param addrlen Size of the addr buffer
-/// @param ip_address Null-terminated IP address string (IPv4 or IPv6)
-/// @param port Port number in host byte order
-/// @return Size of the sockaddr structure used, or 0 on error
-socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const char *ip_address, uint16_t port);
-
-/// Convenience overload for std::string (backward compatible).
-inline socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const std::string &ip_address, uint16_t port) {
-  return set_sockaddr(addr, addrlen, ip_address.c_str(), port);
-}
+socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const std::string &ip_address, uint16_t port);
 
 /// Set a sockaddr to the any address and specified port for the IP version used by socket_ip().
 socklen_t set_sockaddr_any(struct sockaddr *addr, socklen_t addrlen, uint16_t port);

esphome/components/status/binary_sensor.py

@@ -7,14 +7,14 @@ DEPENDENCIES = ["network"]
 
 status_ns = cg.esphome_ns.namespace("status")
 StatusBinarySensor = status_ns.class_(
-    "StatusBinarySensor", binary_sensor.BinarySensor, cg.PollingComponent
+    "StatusBinarySensor", binary_sensor.BinarySensor, cg.Component
 )
 
 CONFIG_SCHEMA = binary_sensor.binary_sensor_schema(
     StatusBinarySensor,
     device_class=DEVICE_CLASS_CONNECTIVITY,
     entity_category=ENTITY_CATEGORY_DIAGNOSTIC,
-).extend(cv.polling_component_schema("1s"))
+).extend(cv.COMPONENT_SCHEMA)
 
 
 async def to_code(config):

esphome/components/status/status_binary_sensor.cpp

@@ -10,11 +10,12 @@
 #include "esphome/components/api/api_server.h"
 #endif
 
-namespace esphome::status {
+namespace esphome {
+namespace status {
 
 static const char *const TAG = "status";
 
-void StatusBinarySensor::update() {
+void StatusBinarySensor::loop() {
   bool status = network::is_connected();
 #ifdef USE_MQTT
   if (mqtt::global_mqtt_client != nullptr) {
@@ -32,4 +33,5 @@ void StatusBinarySensor::update() {
 void StatusBinarySensor::setup() { this->publish_initial_state(false); }
 void StatusBinarySensor::dump_config() { LOG_BINARY_SENSOR("", "Status Binary Sensor", this); }
 
-}  // namespace esphome::status
+}  // namespace status
+}  // namespace esphome

esphome/components/status/status_binary_sensor.h

@@ -3,11 +3,12 @@
 #include "esphome/core/component.h"
 #include "esphome/components/binary_sensor/binary_sensor.h"
 
-namespace esphome::status {
+namespace esphome {
+namespace status {
 
-class StatusBinarySensor : public binary_sensor::BinarySensor, public PollingComponent {
+class StatusBinarySensor : public binary_sensor::BinarySensor, public Component {
  public:
-  void update() override;
+  void loop() override;
 
   void setup() override;
   void dump_config() override;
@@ -15,4 +16,5 @@ class StatusBinarySensor : public binary_sensor::BinarySensor, public PollingCom
   bool is_status_binary_sensor() const override { return true; }
 };
 
-}  // namespace esphome::status
+}  // namespace status
+}  // namespace esphome

esphome/components/sun/text_sensor/sun_text_sensor.h

@@ -14,9 +14,7 @@ class SunTextSensor : public text_sensor::TextSensor, public PollingComponent {
   void set_parent(Sun *parent) { parent_ = parent; }
   void set_elevation(double elevation) { elevation_ = elevation; }
   void set_sunrise(bool sunrise) { sunrise_ = sunrise; }
-  void set_format(const char *format) { this->format_ = format; }
-  /// Prevent accidental use of std::string which would dangle
-  void set_format(const std::string &format) = delete;
+  void set_format(const std::string &format) { format_ = format; }
 
   void update() override {
     optional<ESPTime> res;
@@ -31,14 +29,14 @@ class SunTextSensor : public text_sensor::TextSensor, public PollingComponent {
     }
 
     char buf[ESPTime::STRFTIME_BUFFER_SIZE];
-    size_t len = res->strftime_to(buf, this->format_);
+    size_t len = res->strftime_to(buf, this->format_.c_str());
     this->publish_state(buf, len);
   }
 
   void dump_config() override;
 
  protected:
-  const char *format_{nullptr};
+  std::string format_{};
   Sun *parent_;
   double elevation_;
   bool sunrise_;

esphome/components/sx1509/sx1509_gpio_pin.cpp

@@ -13,7 +13,7 @@ void SX1509GPIOPin::pin_mode(gpio::Flags flags) { this->parent_->pin_mode(this->
 bool SX1509GPIOPin::digital_read() { return this->parent_->digital_read(this->pin_) != this->inverted_; }
 void SX1509GPIOPin::digital_write(bool value) { this->parent_->digital_write(this->pin_, value != this->inverted_); }
 size_t SX1509GPIOPin::dump_summary(char *buffer, size_t len) const {
-  return buf_append_printf(buffer, len, 0, "%u via sx1509", this->pin_);
+  return snprintf(buffer, len, "%u via sx1509", this->pin_);
 }
 
 }  // namespace sx1509

esphome/components/syslog/esphome_syslog.cpp

@@ -47,27 +47,29 @@ void Syslog::log_(const int level, const char *tag, const char *message, size_t
   size_t remaining = sizeof(packet);
 
   // Write PRI - abort if this fails as packet would be malformed
-  offset = buf_append_printf(packet, sizeof(packet), 0, "<%d>", pri);
-  if (offset == 0) {
-    return;  // PRI always produces at least "<0>" (3 chars), so 0 means error
+  int ret = snprintf(packet, remaining, "<%d>", pri);
+  if (ret <= 0 || static_cast<size_t>(ret) >= remaining) {
+    return;
   }
-  remaining -= offset;
+  offset = ret;
+  remaining -= ret;
 
   // Write timestamp directly into packet (RFC 5424: use "-" if time not valid or strftime fails)
   auto now = this->time_->now();
   size_t ts_written = now.is_valid() ? now.strftime(packet + offset, remaining, "%b %e %H:%M:%S") : 0;
   if (ts_written > 0) {
     offset += ts_written;
+    remaining -= ts_written;
   } else if (remaining > 0) {
     packet[offset++] = '-';
+    remaining--;
   }
 
   // Write hostname, tag, and message
-  offset = buf_append_printf(packet, sizeof(packet), offset, " %s %s: %.*s", App.get_name().c_str(), tag, (int) len,
-                             message);
-  // Clamp to exclude null terminator position if buffer was filled
-  if (offset >= sizeof(packet)) {
-    offset = sizeof(packet) - 1;
+  ret = snprintf(packet + offset, remaining, " %s %s: %.*s", App.get_name().c_str(), tag, (int) len, message);
+  if (ret > 0) {
+    // snprintf returns chars that would be written; clamp to actual buffer space
+    offset += std::min(static_cast<size_t>(ret), remaining > 0 ? remaining - 1 : 0);
   }
 
   if (offset > 0) {

esphome/components/tca9555/tca9555.cpp

@@ -139,7 +139,7 @@ void TCA9555GPIOPin::pin_mode(gpio::Flags flags) { this->parent_->pin_mode(this-
 bool TCA9555GPIOPin::digital_read() { return this->parent_->digital_read(this->pin_) != this->inverted_; }
 void TCA9555GPIOPin::digital_write(bool value) { this->parent_->digital_write(this->pin_, value != this->inverted_); }
 size_t TCA9555GPIOPin::dump_summary(char *buffer, size_t len) const {
-  return buf_append_printf(buffer, len, 0, "%u via TCA9555", this->pin_);
+  return snprintf(buffer, len, "%u via TCA9555", this->pin_);
 }
 
 }  // namespace tca9555

esphome/components/template/alarm_control_panel/__init__.py

@@ -118,7 +118,8 @@ async def to_code(config):
     var = await alarm_control_panel.new_alarm_control_panel(config)
     await cg.register_component(var, config)
     if CONF_CODES in config:
-        cg.add(var.set_codes(config[CONF_CODES]))
+        for acode in config[CONF_CODES]:
+            cg.add(var.add_code(acode))
         if CONF_REQUIRES_CODE_TO_ARM in config:
             cg.add(var.set_requires_code_to_arm(config[CONF_REQUIRES_CODE_TO_ARM]))
 

esphome/components/template/alarm_control_panel/template_alarm_control_panel.cpp

@@ -206,13 +206,7 @@ bool TemplateAlarmControlPanel::is_code_valid_(optional<std::string> code) {
   if (!this->codes_.empty()) {
     if (code.has_value()) {
       ESP_LOGVV(TAG, "Checking code: %s", code.value().c_str());
-      // Use strcmp for const char* comparison
-      const char *code_cstr = code.value().c_str();
-      for (const char *stored_code : this->codes_) {
-        if (strcmp(stored_code, code_cstr) == 0)
-          return true;
-      }
-      return false;
+      return (std::count(this->codes_.begin(), this->codes_.end(), code.value()) == 1);
     }
     ESP_LOGD(TAG, "No code provided");
     return false;

esphome/components/template/alarm_control_panel/template_alarm_control_panel.h

@@ -1,7 +1,6 @@
 #pragma once
 
 #include <cinttypes>
-#include <cstring>
 #include <vector>
 
 #include "esphome/core/automation.h"
@@ -87,14 +86,11 @@ class TemplateAlarmControlPanel final : public alarm_control_panel::AlarmControl
                   AlarmSensorType type = ALARM_SENSOR_TYPE_DELAYED);
 #endif
 
-  /** Set the codes (from initializer list).
+  /** add a code
    *
-   * @param codes The list of valid codes
+   * @param code The code
    */
-  void set_codes(std::initializer_list<const char *> codes) { this->codes_ = codes; }
-
-  // Deleted overload to catch incorrect std::string usage at compile time
-  void set_codes(std::initializer_list<std::string> codes) = delete;
+  void add_code(const std::string &code) { this->codes_.push_back(code); }
 
   /** set requires a code to arm
    *
@@ -159,8 +155,8 @@ class TemplateAlarmControlPanel final : public alarm_control_panel::AlarmControl
   uint32_t pending_time_;
   // the time in trigger
   uint32_t trigger_time_;
-  // a list of codes (const char* pointers to string literals in flash)
-  FixedVector<const char *> codes_;
+  // a list of codes
+  std::vector<std::string> codes_;
   // requires a code to arm
   bool requires_code_to_arm_ = false;
   bool supports_arm_home_ = false;

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.StringRef, "x")], config[CONF_SET_ACTION]
+            var.get_set_trigger(), [(cg.std_string, "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(StringRef(this->option_at(index)));
+  this->set_trigger_->trigger(std::string(this->option_at(index)));
 
   if (this->optimistic_)
     this->publish_state(index);

esphome/components/template/select/template_select.h

@@ -4,7 +4,6 @@
 #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_ {
@@ -18,7 +17,7 @@ class TemplateSelect final : public select::Select, public PollingComponent {
   void dump_config() override;
   float get_setup_priority() const override { return setup_priority::HARDWARE; }
 
-  Trigger<StringRef> *get_set_trigger() const { return this->set_trigger_; }
+  Trigger<std::string> *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; }
@@ -28,7 +27,7 @@ class TemplateSelect final : public select::Select, public PollingComponent {
   bool optimistic_ = false;
   size_t initial_option_index_{0};
   bool restore_value_ = false;
-  Trigger<StringRef> *set_trigger_ = new Trigger<StringRef>();
+  Trigger<std::string> *set_trigger_ = new Trigger<std::string>();
   TemplateLambda<std::string> f_;
 
   ESPPreferenceObject pref_;

esphome/components/template/text/template_text.cpp

@@ -8,23 +8,16 @@ static const char *const TAG = "template.text";
 void TemplateText::setup() {
   if (this->f_.has_value())
     return;
-
-  if (this->pref_ == nullptr) {
-    // No restore - use const char* directly, no heap allocation needed
-    if (this->initial_value_ != nullptr && this->initial_value_[0] != '\0') {
-      ESP_LOGD(TAG, "State from initial: %s", this->initial_value_);
-      this->publish_state(this->initial_value_);
-    }
-    return;
+  std::string value = this->initial_value_;
+  if (!this->pref_) {
+    ESP_LOGD(TAG, "State from initial: %s", value.c_str());
+  } else {
+    uint32_t key = this->get_preference_hash();
+    key += this->traits.get_min_length() << 2;
+    key += this->traits.get_max_length() << 4;
+    key += fnv1_hash(this->traits.get_pattern_c_str()) << 6;
+    this->pref_->setup(key, value);
   }
-
-  // Need std::string for pref_->setup() to fill from flash
-  std::string value{this->initial_value_ != nullptr ? this->initial_value_ : ""};
-  uint32_t key = this->get_preference_hash();
-  key += this->traits.get_min_length() << 2;
-  key += this->traits.get_max_length() << 4;
-  key += fnv1_hash(this->traits.get_pattern_c_str()) << 6;
-  this->pref_->setup(key, value);
   if (!value.empty())
     this->publish_state(value);
 }

esphome/components/template/text/template_text.h

@@ -70,15 +70,13 @@ class TemplateText final : public text::Text, public PollingComponent {
 
   Trigger<std::string> *get_set_trigger() const { return this->set_trigger_; }
   void set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
-  void set_initial_value(const char *initial_value) { this->initial_value_ = initial_value; }
-  /// Prevent accidental use of std::string which would dangle
-  void set_initial_value(const std::string &initial_value) = delete;
+  void set_initial_value(const std::string &initial_value) { this->initial_value_ = initial_value; }
   void set_value_saver(TemplateTextSaverBase *restore_value_saver) { this->pref_ = restore_value_saver; }
 
  protected:
   void control(const std::string &value) override;
   bool optimistic_ = false;
-  const char *initial_value_{nullptr};
+  std::string initial_value_;
   Trigger<std::string> *set_trigger_ = new Trigger<std::string>();
   TemplateLambda<std::string> f_{};
 

esphome/components/tormatic/tormatic_protocol.h

@@ -55,7 +55,6 @@ enum MessageType : uint16_t {
   COMMAND = 0x0106,
 };
 
-// Max string length: 7 ("Unknown"/"Command"). Update print() buffer sizes if adding longer strings.
 inline const char *message_type_to_str(MessageType t) {
   switch (t) {
     case STATUS:
@@ -84,11 +83,7 @@ struct MessageHeader {
   }
 
   std::string print() {
-    // 64 bytes: "MessageHeader: seq " + uint16 + ", len " + uint32 + ", type " + type + safety margin
-    char buf[64];
-    buf_append_printf(buf, sizeof(buf), 0, "MessageHeader: seq %d, len %d, type %s", this->seq, this->len,
-                      message_type_to_str(this->type));
-    return buf;
+    return str_sprintf("MessageHeader: seq %d, len %d, type %s", this->seq, this->len, message_type_to_str(this->type));
   }
 
   void byteswap() {
@@ -136,7 +131,6 @@ inline CoverOperation gate_status_to_cover_operation(GateStatus s) {
   return COVER_OPERATION_IDLE;
 }
 
-// Max string length: 11 ("Ventilating"). Update print() buffer sizes if adding longer strings.
 inline const char *gate_status_to_str(GateStatus s) {
   switch (s) {
     case PAUSED:
@@ -176,12 +170,7 @@ struct StatusReply {
   GateStatus state;
   uint8_t trailer = 0x0;
 
-  std::string print() {
-    // 48 bytes: "StatusReply: state " (19) + state (11) + safety margin
-    char buf[48];
-    buf_append_printf(buf, sizeof(buf), 0, "StatusReply: state %s", gate_status_to_str(this->state));
-    return buf;
-  }
+  std::string print() { return str_sprintf("StatusReply: state %s", gate_status_to_str(this->state)); }
 
   void byteswap(){};
 } __attribute__((packed));
@@ -213,12 +202,7 @@ struct CommandRequestReply {
   CommandRequestReply() = default;
   CommandRequestReply(GateStatus state) { this->state = state; }
 
-  std::string print() {
-    // 56 bytes: "CommandRequestReply: state " (27) + state (11) + safety margin
-    char buf[56];
-    buf_append_printf(buf, sizeof(buf), 0, "CommandRequestReply: state %s", gate_status_to_str(this->state));
-    return buf;
-  }
+  std::string print() { return str_sprintf("CommandRequestReply: state %s", gate_status_to_str(this->state)); }
 
   void byteswap() { this->type = convert_big_endian(this->type); }
 } __attribute__((packed));

esphome/components/toshiba/toshiba.cpp

@@ -1,6 +1,5 @@
 #include "toshiba.h"
 #include "esphome/components/remote_base/toshiba_ac_protocol.h"
-#include "esphome/core/helpers.h"
 
 #include <vector>
 
@@ -428,17 +427,10 @@ void ToshibaClimate::setup() {
   // Never send nan to HA
   if (std::isnan(this->target_temperature))
     this->target_temperature = 24;
-#if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_VERBOSE
   // Log final state for debugging HA errors
-  const char *fan_mode_str = "NONE";
-  char fan_mode_buf[4];  // max 3 digits for fan mode enum + null
-  if (this->fan_mode.has_value()) {
-    buf_append_printf(fan_mode_buf, sizeof(fan_mode_buf), 0, "%d", static_cast<int>(this->fan_mode.value()));
-    fan_mode_str = fan_mode_buf;
-  }
-  ESP_LOGV(TAG, "Setup complete - Mode: %d, Fan: %s, Swing: %d, Temp: %.1f", static_cast<int>(this->mode), fan_mode_str,
+  ESP_LOGV(TAG, "Setup complete - Mode: %d, Fan: %s, Swing: %d, Temp: %.1f", static_cast<int>(this->mode),
+           this->fan_mode.has_value() ? std::to_string(static_cast<int>(this->fan_mode.value())).c_str() : "NONE",
            static_cast<int>(this->swing_mode), this->target_temperature);
-#endif
 }
 
 void ToshibaClimate::transmit_state() {

esphome/components/tuya/light/tuya_light.cpp

@@ -191,7 +191,7 @@ void TuyaLight::write_state(light::LightState *state) {
       case TuyaColorType::RGB: {
         char buffer[7];
         const char *format_str = this->color_type_lowercase_ ? "%02x%02x%02x" : "%02X%02X%02X";
-        snprintf(buffer, sizeof(buffer), format_str, int(red * 255), int(green * 255), int(blue * 255));
+        sprintf(buffer, format_str, int(red * 255), int(green * 255), int(blue * 255));
         color_value = buffer;
         break;
       }
@@ -201,7 +201,7 @@ void TuyaLight::write_state(light::LightState *state) {
         rgb_to_hsv(red, green, blue, hue, saturation, value);
         char buffer[13];
         const char *format_str = this->color_type_lowercase_ ? "%04x%04x%04x" : "%04X%04X%04X";
-        snprintf(buffer, sizeof(buffer), format_str, hue, int(saturation * 1000), int(value * 1000));
+        sprintf(buffer, format_str, hue, int(saturation * 1000), int(value * 1000));
         color_value = buffer;
         break;
       }
@@ -211,8 +211,8 @@ void TuyaLight::write_state(light::LightState *state) {
         rgb_to_hsv(red, green, blue, hue, saturation, value);
         char buffer[15];
         const char *format_str = this->color_type_lowercase_ ? "%02x%02x%02x%04x%02x%02x" : "%02X%02X%02X%04X%02X%02X";
-        snprintf(buffer, sizeof(buffer), format_str, int(red * 255), int(green * 255), int(blue * 255), hue,
-                 int(saturation * 255), int(value * 255));
+        sprintf(buffer, format_str, int(red * 255), int(green * 255), int(blue * 255), hue, int(saturation * 255),
+                int(value * 255));
         color_value = buffer;
         break;
       }

esphome/components/tuya/text_sensor/tuya_text_sensor.cpp

@@ -24,7 +24,7 @@ void TuyaTextSensor::setup() {
       }
       case TuyaDatapointType::ENUM: {
         char buf[4];  // uint8_t max is 3 digits + null
-        buf_append_printf(buf, sizeof(buf), 0, "%u", datapoint.value_enum);
+        snprintf(buf, sizeof(buf), "%u", datapoint.value_enum);
         ESP_LOGD(TAG, "MCU reported text sensor %u is: %s", datapoint.id, buf);
         this->publish_state(buf);
         break;

esphome/components/uart/uart_debugger.cpp

@@ -107,7 +107,7 @@ void UARTDebug::log_hex(UARTDirection direction, std::vector<uint8_t> bytes, uin
     if (i > 0) {
       res += separator;
     }
-    buf_append_printf(buf, sizeof(buf), 0, "%02X", bytes[i]);
+    sprintf(buf, "%02X", bytes[i]);
     res += buf;
   }
   ESP_LOGD(TAG, "%s", res.c_str());
@@ -147,7 +147,7 @@ void UARTDebug::log_string(UARTDirection direction, std::vector<uint8_t> bytes)
     } else if (bytes[i] == 92) {
       res += "\\\\";
     } else if (bytes[i] < 32 || bytes[i] > 127) {
-      buf_append_printf(buf, sizeof(buf), 0, "\\x%02X", bytes[i]);
+      sprintf(buf, "\\x%02X", bytes[i]);
       res += buf;
     } else {
       res += bytes[i];
@@ -166,13 +166,11 @@ void UARTDebug::log_int(UARTDirection direction, std::vector<uint8_t> bytes, uin
   } else {
     res += ">>> ";
   }
-  char buf[4];  // max 3 digits for uint8_t (255) + null
   for (size_t i = 0; i < len; i++) {
     if (i > 0) {
       res += separator;
     }
-    buf_append_printf(buf, sizeof(buf), 0, "%u", bytes[i]);
-    res += buf;
+    res += to_string(bytes[i]);
   }
   ESP_LOGD(TAG, "%s", res.c_str());
   delay(10);
@@ -191,7 +189,7 @@ void UARTDebug::log_binary(UARTDirection direction, std::vector<uint8_t> bytes,
     if (i > 0) {
       res += separator;
     }
-    buf_append_printf(buf, sizeof(buf), 0, "0b" BYTE_TO_BINARY_PATTERN " (0x%02X)", BYTE_TO_BINARY(bytes[i]), bytes[i]);
+    sprintf(buf, "0b" BYTE_TO_BINARY_PATTERN " (0x%02X)", BYTE_TO_BINARY(bytes[i]), bytes[i]);
     res += buf;
   }
   ESP_LOGD(TAG, "%s", res.c_str());

esphome/components/udp/__init__.py

@@ -108,7 +108,8 @@ async def to_code(config):
         cg.add(var.set_broadcast_port(conf_port[CONF_BROADCAST_PORT]))
     if (listen_address := str(config[CONF_LISTEN_ADDRESS])) != "255.255.255.255":
         cg.add(var.set_listen_address(listen_address))
-    cg.add(var.set_addresses([str(addr) for addr in config[CONF_ADDRESSES]]))
+    for address in config[CONF_ADDRESSES]:
+        cg.add(var.add_address(str(address)))
     if on_receive := config.get(CONF_ON_RECEIVE):
         on_receive = on_receive[0]
         trigger = cg.new_Pvariable(on_receive[CONF_TRIGGER_ID])

esphome/components/udp/udp_component.cpp

@@ -5,7 +5,8 @@
 #include "esphome/components/network/util.h"
 #include "udp_component.h"
 
-namespace esphome::udp {
+namespace esphome {
+namespace udp {
 
 static const char *const TAG = "udp";
 
@@ -94,7 +95,7 @@ void UDPComponent::setup() {
   // 8266 and RP2040 `Duino
   for (const auto &address : this->addresses_) {
     auto ipaddr = IPAddress();
-    ipaddr.fromString(address);
+    ipaddr.fromString(address.c_str());
     this->ipaddrs_.push_back(ipaddr);
   }
   if (this->should_listen_)
@@ -129,8 +130,8 @@ void UDPComponent::dump_config() {
                 "  Listen Port: %u\n"
                 "  Broadcast Port: %u",
                 this->listen_port_, this->broadcast_port_);
-  for (const char *address : this->addresses_)
-    ESP_LOGCONFIG(TAG, "  Address: %s", address);
+  for (const auto &address : this->addresses_)
+    ESP_LOGCONFIG(TAG, "  Address: %s", address.c_str());
   if (this->listen_address_.has_value()) {
     char addr_buf[network::IP_ADDRESS_BUFFER_SIZE];
     ESP_LOGCONFIG(TAG, "  Listen address: %s", this->listen_address_.value().str_to(addr_buf));
@@ -161,6 +162,7 @@ void UDPComponent::send_packet(const uint8_t *data, size_t size) {
   }
 #endif
 }
-}  // namespace esphome::udp
+}  // namespace udp
+}  // namespace esphome
 
 #endif

esphome/components/udp/udp_component.h

@@ -2,7 +2,6 @@
 
 #include "esphome/core/defines.h"
 #ifdef USE_NETWORK
-#include "esphome/core/helpers.h"
 #include "esphome/components/network/ip_address.h"
 #if defined(USE_SOCKET_IMPL_BSD_SOCKETS) || defined(USE_SOCKET_IMPL_LWIP_SOCKETS)
 #include "esphome/components/socket/socket.h"
@@ -10,17 +9,15 @@
 #ifdef USE_SOCKET_IMPL_LWIP_TCP
 #include <WiFiUdp.h>
 #endif
-#include <initializer_list>
 #include <vector>
 
-namespace esphome::udp {
+namespace esphome {
+namespace udp {
 
 static const size_t MAX_PACKET_SIZE = 508;
 class UDPComponent : public Component {
  public:
-  void set_addresses(std::initializer_list<const char *> addresses) { this->addresses_ = addresses; }
-  /// Prevent accidental use of std::string which would dangle
-  void set_addresses(std::initializer_list<std::string> addresses) = delete;
+  void add_address(const char *addr) { this->addresses_.emplace_back(addr); }
   void set_listen_address(const char *listen_addr) { this->listen_address_ = network::IPAddress(listen_addr); }
   void set_listen_port(uint16_t port) { this->listen_port_ = port; }
   void set_broadcast_port(uint16_t port) { this->broadcast_port_ = port; }
@@ -52,10 +49,11 @@ class UDPComponent : public Component {
   std::vector<IPAddress> ipaddrs_{};
   WiFiUDP udp_client_{};
 #endif
-  FixedVector<const char *> addresses_{};
+  std::vector<std::string> addresses_{};
 
   optional<network::IPAddress> listen_address_{};
 };
 
-}  // namespace esphome::udp
+}  // namespace udp
+}  // namespace esphome
 #endif

esphome/components/uptime/text_sensor/uptime_text_sensor.cpp

@@ -9,12 +9,17 @@ namespace uptime {
 
 static const char *const TAG = "uptime.sensor";
 
+// Clamp position to valid buffer range when snprintf indicates truncation
+static size_t clamp_buffer_pos(size_t pos, size_t buf_size) { return pos < buf_size ? pos : buf_size - 1; }
+
 static void append_unit(char *buf, size_t buf_size, size_t &pos, const char *separator, unsigned value,
                         const char *label) {
   if (pos > 0) {
-    pos = buf_append_printf(buf, buf_size, pos, "%s", separator);
+    pos += snprintf(buf + pos, buf_size - pos, "%s", separator);
+    pos = clamp_buffer_pos(pos, buf_size);
   }
-  pos = buf_append_printf(buf, buf_size, pos, "%u%s", value, label);
+  pos += snprintf(buf + pos, buf_size - pos, "%u%s", value, label);
+  pos = clamp_buffer_pos(pos, buf_size);
 }
 
 void UptimeTextSensor::setup() {

esphome/components/web_server/web_server.cpp

@@ -1188,7 +1188,11 @@ std::string WebServer::date_json_(datetime::DateEntity *obj, JsonDetail start_co
 
   // Format: YYYY-MM-DD (max 10 chars + null)
   char value[12];
-  buf_append_printf(value, sizeof(value), 0, "%d-%02d-%02d", obj->year, obj->month, obj->day);
+#ifdef USE_ESP8266
+  snprintf_P(value, sizeof(value), PSTR("%d-%02d-%02d"), obj->year, obj->month, obj->day);
+#else
+  snprintf(value, sizeof(value), "%d-%02d-%02d", obj->year, obj->month, obj->day);
+#endif
   set_json_icon_state_value(root, obj, "date", value, value, start_config);
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
@@ -1247,7 +1251,11 @@ std::string WebServer::time_json_(datetime::TimeEntity *obj, JsonDetail start_co
 
   // Format: HH:MM:SS (8 chars + null)
   char value[12];
-  buf_append_printf(value, sizeof(value), 0, "%02d:%02d:%02d", obj->hour, obj->minute, obj->second);
+#ifdef USE_ESP8266
+  snprintf_P(value, sizeof(value), PSTR("%02d:%02d:%02d"), obj->hour, obj->minute, obj->second);
+#else
+  snprintf(value, sizeof(value), "%02d:%02d:%02d", obj->hour, obj->minute, obj->second);
+#endif
   set_json_icon_state_value(root, obj, "time", value, value, start_config);
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
@@ -1306,8 +1314,13 @@ std::string WebServer::datetime_json_(datetime::DateTimeEntity *obj, JsonDetail
 
   // Format: YYYY-MM-DD HH:MM:SS (max 19 chars + null)
   char value[24];
-  buf_append_printf(value, sizeof(value), 0, "%d-%02d-%02d %02d:%02d:%02d", obj->year, obj->month, obj->day, obj->hour,
-                    obj->minute, obj->second);
+#ifdef USE_ESP8266
+  snprintf_P(value, sizeof(value), PSTR("%d-%02d-%02d %02d:%02d:%02d"), obj->year, obj->month, obj->day, obj->hour,
+             obj->minute, obj->second);
+#else
+  snprintf(value, sizeof(value), "%d-%02d-%02d %02d:%02d:%02d", obj->year, obj->month, obj->day, obj->hour, obj->minute,
+           obj->second);
+#endif
   set_json_icon_state_value(root, obj, "datetime", value, value, start_config);
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);

esphome/components/weikai/weikai.cpp

@@ -4,13 +4,19 @@
 /// @details The classes declared in this file can be used by the Weikai family
 
 #include "weikai.h"
-#include "esphome/core/helpers.h"
 
 namespace esphome {
 namespace weikai {
 
 static const char *const TAG = "weikai";
 
+/// @brief convert an int to binary representation as C++ std::string
+/// @param val integer to convert
+/// @return a std::string
+inline std::string i2s(uint8_t val) { return std::bitset<8>(val).to_string(); }
+/// Convert std::string to C string
+#define I2S2CS(val) (i2s(val).c_str())
+
 /// @brief measure the time elapsed between two calls
 /// @param last_time time of the previous call
 /// @return the elapsed time in milliseconds
@@ -164,18 +170,17 @@ void WeikaiComponent::test_gpio_input_() {
   static bool init_input{false};
   static uint8_t state{0};
   uint8_t value;
-  char bin_buf[9];  // 8 binary digits + null
   if (!init_input) {
     init_input = true;
     // set all pins in input mode
     this->reg(WKREG_GPDIR, 0) = 0x00;
     ESP_LOGI(TAG, "initializing all pins to input mode");
     state = this->reg(WKREG_GPDAT, 0);
-    ESP_LOGI(TAG, "initial input data state = %02X (%s)", state, format_bin_to(bin_buf, state));
+    ESP_LOGI(TAG, "initial input data state = %02X (%s)", state, I2S2CS(state));
   }
   value = this->reg(WKREG_GPDAT, 0);
   if (value != state) {
-    ESP_LOGI(TAG, "Input data changed from %02X to %02X (%s)", state, value, format_bin_to(bin_buf, value));
+    ESP_LOGI(TAG, "Input data changed from %02X to %02X (%s)", state, value, I2S2CS(value));
     state = value;
   }
 }
@@ -183,7 +188,6 @@ void WeikaiComponent::test_gpio_input_() {
 void WeikaiComponent::test_gpio_output_() {
   static bool init_output{false};
   static uint8_t state{0};
-  char bin_buf[9];  // 8 binary digits + null
   if (!init_output) {
     init_output = true;
     // set all pins in output mode
@@ -194,7 +198,7 @@ void WeikaiComponent::test_gpio_output_() {
   }
   state = ~state;
   this->reg(WKREG_GPDAT, 0) = state;
-  ESP_LOGI(TAG, "Flipping all outputs to %02X (%s)", state, format_bin_to(bin_buf, state));
+  ESP_LOGI(TAG, "Flipping all outputs to %02X (%s)", state, I2S2CS(state));
   delay(100);  // NOLINT
 }
 #endif
@@ -204,9 +208,7 @@ void WeikaiComponent::test_gpio_output_() {
 ///////////////////////////////////////////////////////////////////////////////
 bool WeikaiComponent::read_pin_val_(uint8_t pin) {
   this->input_state_ = this->reg(WKREG_GPDAT, 0);
-  char bin_buf[9];
-  ESP_LOGVV(TAG, "reading input pin %u = %u in_state %s", pin, this->input_state_ & (1 << pin),
-            format_bin_to(bin_buf, this->input_state_));
+  ESP_LOGVV(TAG, "reading input pin %u = %u in_state %s", pin, this->input_state_ & (1 << pin), I2S2CS(input_state_));
   return this->input_state_ & (1 << pin);
 }
 
@@ -216,9 +218,7 @@ void WeikaiComponent::write_pin_val_(uint8_t pin, bool value) {
   } else {
     this->output_state_ &= ~(1 << pin);
   }
-  char bin_buf[9];
-  ESP_LOGVV(TAG, "writing output pin %d with %d out_state %s", pin, uint8_t(value),
-            format_bin_to(bin_buf, this->output_state_));
+  ESP_LOGVV(TAG, "writing output pin %d with %d out_state %s", pin, uint8_t(value), I2S2CS(this->output_state_));
   this->reg(WKREG_GPDAT, 0) = this->output_state_;
 }
 
@@ -232,8 +232,7 @@ void WeikaiComponent::set_pin_direction_(uint8_t pin, gpio::Flags flags) {
       ESP_LOGE(TAG, "pin %d direction invalid", pin);
     }
   }
-  char bin_buf[9];
-  ESP_LOGVV(TAG, "setting pin %d direction to %d pin_config=%s", pin, flags, format_bin_to(bin_buf, this->pin_config_));
+  ESP_LOGVV(TAG, "setting pin %d direction to %d pin_config=%s", pin, flags, I2S2CS(this->pin_config_));
   this->reg(WKREG_GPDIR, 0) = this->pin_config_;  // TODO check ~
 }
 
@@ -242,11 +241,12 @@ void WeikaiGPIOPin::setup() {
                 flags_ == gpio::FLAG_INPUT          ? "Input"
                 : this->flags_ == gpio::FLAG_OUTPUT ? "Output"
                                                     : "NOT SPECIFIED");
+  // ESP_LOGCONFIG(TAG, "Setting GPIO pins mode to '%s' %02X", I2S2CS(this->flags_), this->flags_);
   this->pin_mode(this->flags_);
 }
 
 size_t WeikaiGPIOPin::dump_summary(char *buffer, size_t len) const {
-  return buf_append_printf(buffer, len, 0, "%u via WeiKai %s", this->pin_, this->parent_->get_name());
+  return snprintf(buffer, len, "%u via WeiKai %s", this->pin_, this->parent_->get_name());
 }
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -297,9 +297,8 @@ void WeikaiChannel::set_line_param_() {
       break;  // no parity 000x
   }
   this->reg(WKREG_LCR) = lcr;  // write LCR
-  char bin_buf[9];
   ESP_LOGV(TAG, "    line config: %d data_bits, %d stop_bits, parity %s register [%s]", this->data_bits_,
-           this->stop_bits_, p2s(this->parity_), format_bin_to(bin_buf, lcr));
+           this->stop_bits_, p2s(this->parity_), I2S2CS(lcr));
 }
 
 void WeikaiChannel::set_baudrate_() {
@@ -335,8 +334,7 @@ size_t WeikaiChannel::tx_in_fifo_() {
   if (tfcnt == 0) {
     uint8_t const fsr = this->reg(WKREG_FSR);
     if (fsr & FSR_TFFULL) {
-      char bin_buf[9];
-      ESP_LOGVV(TAG, "tx FIFO full FSR=%s", format_bin_to(bin_buf, fsr));
+      ESP_LOGVV(TAG, "tx FIFO full FSR=%s", I2S2CS(fsr));
       tfcnt = FIFO_SIZE;
     }
   }
@@ -348,15 +346,14 @@ size_t WeikaiChannel::rx_in_fifo_() {
   size_t available = this->reg(WKREG_RFCNT);
   uint8_t const fsr = this->reg(WKREG_FSR);
   if (fsr & (FSR_RFOE | FSR_RFLB | FSR_RFFE | FSR_RFPE)) {
-    char bin_buf[9];
     if (fsr & FSR_RFOE)
-      ESP_LOGE(TAG, "Receive data overflow FSR=%s", format_bin_to(bin_buf, fsr));
+      ESP_LOGE(TAG, "Receive data overflow FSR=%s", I2S2CS(fsr));
     if (fsr & FSR_RFLB)
-      ESP_LOGE(TAG, "Receive line break FSR=%s", format_bin_to(bin_buf, fsr));
+      ESP_LOGE(TAG, "Receive line break FSR=%s", I2S2CS(fsr));
     if (fsr & FSR_RFFE)
-      ESP_LOGE(TAG, "Receive frame error FSR=%s", format_bin_to(bin_buf, fsr));
+      ESP_LOGE(TAG, "Receive frame error FSR=%s", I2S2CS(fsr));
     if (fsr & FSR_RFPE)
-      ESP_LOGE(TAG, "Receive parity error FSR=%s", format_bin_to(bin_buf, fsr));
+      ESP_LOGE(TAG, "Receive parity error FSR=%s", I2S2CS(fsr));
   }
   if ((available == 0) && (fsr & FSR_RFDAT)) {
     // here we should be very careful because we can have something like this:
@@ -365,13 +362,11 @@ size_t WeikaiChannel::rx_in_fifo_() {
     // -  so to be sure we need to do another read of RFCNT and if it is still zero -> buffer full
     available = this->reg(WKREG_RFCNT);
     if (available == 0) {  // still zero ?
-      char bin_buf[9];
-      ESP_LOGV(TAG, "rx FIFO is full FSR=%s", format_bin_to(bin_buf, fsr));
+      ESP_LOGV(TAG, "rx FIFO is full FSR=%s", I2S2CS(fsr));
       available = FIFO_SIZE;
     }
   }
-  char bin_buf2[9];
-  ESP_LOGVV(TAG, "rx FIFO contain %d bytes - FSR status=%s", available, format_bin_to(bin_buf2, fsr));
+  ESP_LOGVV(TAG, "rx FIFO contain %d bytes - FSR status=%s", available, I2S2CS(fsr));
   return available;
 }
 

esphome/components/weikai/weikai.h

@@ -8,6 +8,7 @@
 ///                 wk2132_i2c, wk2168_i2c, wk2204_i2c, wk2212_i2c
 
 #pragma once
+#include <bitset>
 #include <memory>
 #include <cinttypes>
 #include "esphome/core/component.h"

esphome/components/weikai_spi/weikai_spi.cpp

@@ -10,6 +10,13 @@ namespace weikai_spi {
 using namespace weikai;
 static const char *const TAG = "weikai_spi";
 
+/// @brief convert an int to binary representation as C++ std::string
+/// @param val integer to convert
+/// @return a std::string
+inline std::string i2s(uint8_t val) { return std::bitset<8>(val).to_string(); }
+/// Convert std::string to C string
+#define I2S2CS(val) (i2s(val).c_str())
+
 /// @brief measure the time elapsed between two calls
 /// @param last_time time of the previous call
 /// @return the elapsed time in microseconds
@@ -100,8 +107,7 @@ uint8_t WeikaiRegisterSPI::read_reg() const {
   spi_comp->write_byte(cmd);
   uint8_t val = spi_comp->read_byte();
   spi_comp->disable();
-  char bin_buf[9];
-  ESP_LOGVV(TAG, "WeikaiRegisterSPI::read_reg() cmd=%s(%02X) reg=%s ch=%d buf=%02X", format_bin_to(bin_buf, cmd), cmd,
+  ESP_LOGVV(TAG, "WeikaiRegisterSPI::read_reg() cmd=%s(%02X) reg=%s ch=%d buf=%02X", I2S2CS(cmd), cmd,
             reg_to_str(this->register_, this->comp_->page1()), this->channel_, val);
   return val;
 }
@@ -114,9 +120,8 @@ void WeikaiRegisterSPI::read_fifo(uint8_t *data, size_t length) const {
   spi_comp->read_array(data, length);
   spi_comp->disable();
 #ifdef ESPHOME_LOG_HAS_VERY_VERBOSE
-  char bin_buf[9];
-  ESP_LOGVV(TAG, "WeikaiRegisterSPI::read_fifo() cmd=%s(%02X) ch=%d len=%d buffer", format_bin_to(bin_buf, cmd), cmd,
-            this->channel_, length);
+  ESP_LOGVV(TAG, "WeikaiRegisterSPI::read_fifo() cmd=%s(%02X) ch=%d len=%d buffer", I2S2CS(cmd), cmd, this->channel_,
+            length);
   print_buffer(data, length);
 #endif
 }
@@ -127,9 +132,8 @@ void WeikaiRegisterSPI::write_reg(uint8_t value) {
   spi_comp->enable();
   spi_comp->write_array(buf, 2);
   spi_comp->disable();
-  char bin_buf[9];
-  ESP_LOGVV(TAG, "WeikaiRegisterSPI::write_reg() cmd=%s(%02X) reg=%s ch=%d buf=%02X", format_bin_to(bin_buf, buf[0]),
-            buf[0], reg_to_str(this->register_, this->comp_->page1()), this->channel_, buf[1]);
+  ESP_LOGVV(TAG, "WeikaiRegisterSPI::write_reg() cmd=%s(%02X) reg=%s ch=%d buf=%02X", I2S2CS(buf[0]), buf[0],
+            reg_to_str(this->register_, this->comp_->page1()), this->channel_, buf[1]);
 }
 
 void WeikaiRegisterSPI::write_fifo(uint8_t *data, size_t length) {
@@ -141,9 +145,8 @@ void WeikaiRegisterSPI::write_fifo(uint8_t *data, size_t length) {
   spi_comp->disable();
 
 #ifdef ESPHOME_LOG_HAS_VERY_VERBOSE
-  char bin_buf[9];
-  ESP_LOGVV(TAG, "WeikaiRegisterSPI::write_fifo() cmd=%s(%02X) ch=%d len=%d buffer", format_bin_to(bin_buf, cmd), cmd,
-            this->channel_, length);
+  ESP_LOGVV(TAG, "WeikaiRegisterSPI::write_fifo() cmd=%s(%02X) ch=%d len=%d buffer", I2S2CS(cmd), cmd, this->channel_,
+            length);
   print_buffer(data, length);
 #endif
 }