Apply suggestions from code review

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

esphome/components/api/homeassistant_service.h

@@ -25,7 +25,9 @@ template<typename... X> class TemplatableStringValue : public TemplatableValue<s
 
  private:
   // Helper to convert value to string - handles the case where value is already a string
-  template<typename T> static std::string value_to_string(T &&val) { return to_string(std::forward<T>(val)); }
+  template<typename T> static std::string value_to_string(T &&val) {
+    return to_string(std::forward<T>(val));  // NOLINT
+  }
 
   // Overloads for string types - needed because std::to_string doesn't support them
   static std::string value_to_string(char *val) {

esphome/components/cs5460a/cs5460a.h

@@ -76,7 +76,6 @@ class CS5460AComponent : public Component,
   void restart() { restart_(); }
 
   void setup() override;
-  void loop() override {}
   void dump_config() override;
 
  protected:

esphome/components/debug/debug_component.cpp

@@ -30,7 +30,7 @@ void DebugComponent::dump_config() {
 
   char device_info_buffer[DEVICE_INFO_BUFFER_SIZE];
   ESP_LOGD(TAG, "ESPHome version %s", ESPHOME_VERSION);
-  size_t pos = buf_append(device_info_buffer, DEVICE_INFO_BUFFER_SIZE, 0, "%s", ESPHOME_VERSION);
+  size_t pos = buf_append_printf(device_info_buffer, DEVICE_INFO_BUFFER_SIZE, 0, "%s", ESPHOME_VERSION);
 
   this->free_heap_ = get_free_heap_();
   ESP_LOGD(TAG, "Free Heap Size: %" PRIu32 " bytes", this->free_heap_);

esphome/components/debug/debug_component.h

@@ -5,12 +5,6 @@
 #include "esphome/core/helpers.h"
 #include "esphome/core/macros.h"
 #include <span>
-#include <cstdarg>
-#include <cstdio>
-#include <algorithm>
-#ifdef USE_ESP8266
-#include <pgmspace.h>
-#endif
 
 #ifdef USE_SENSOR
 #include "esphome/components/sensor/sensor.h"
@@ -25,40 +19,7 @@ namespace debug {
 static constexpr size_t DEVICE_INFO_BUFFER_SIZE = 256;
 static constexpr size_t RESET_REASON_BUFFER_SIZE = 128;
 
-#ifdef USE_ESP8266
-// ESP8266: Use vsnprintf_P to keep format strings in flash (PROGMEM)
-// Format strings must be wrapped with PSTR() macro
-inline size_t buf_append_p(char *buf, size_t size, size_t pos, PGM_P fmt, ...) {
-  if (pos >= size) {
-    return size;
-  }
-  va_list args;
-  va_start(args, fmt);
-  int written = vsnprintf_P(buf + pos, size - pos, fmt, args);
-  va_end(args);
-  if (written < 0) {
-    return pos;  // encoding error
-  }
-  return std::min(pos + static_cast<size_t>(written), size);
-}
-#define buf_append(buf, size, pos, fmt, ...) buf_append_p(buf, size, pos, PSTR(fmt), ##__VA_ARGS__)
-#else
-/// Safely append formatted string to buffer, returning new position (capped at size)
-__attribute__((format(printf, 4, 5))) inline size_t buf_append(char *buf, size_t size, size_t pos, const char *fmt,
-                                                               ...) {
-  if (pos >= size) {
-    return size;
-  }
-  va_list args;
-  va_start(args, fmt);
-  int written = vsnprintf(buf + pos, size - pos, fmt, args);
-  va_end(args);
-  if (written < 0) {
-    return pos;  // encoding error
-  }
-  return std::min(pos + static_cast<size_t>(written), size);
-}
-#endif
+// buf_append_printf is now provided by esphome/core/helpers.h
 
 class DebugComponent : public PollingComponent {
  public:

esphome/components/debug/debug_esp32.cpp

@@ -173,8 +173,8 @@ size_t DebugComponent::get_device_info_(std::span<char, DEVICE_INFO_BUFFER_SIZE>
   uint32_t flash_size = ESP.getFlashChipSize() / 1024;       // NOLINT
   uint32_t flash_speed = ESP.getFlashChipSpeed() / 1000000;  // NOLINT
   ESP_LOGD(TAG, "Flash Chip: Size=%" PRIu32 "kB Speed=%" PRIu32 "MHz Mode=%s", flash_size, flash_speed, flash_mode);
-  pos = buf_append(buf, size, pos, "|Flash: %" PRIu32 "kB Speed:%" PRIu32 "MHz Mode:%s", flash_size, flash_speed,
-                   flash_mode);
+  pos = buf_append_printf(buf, size, pos, "|Flash: %" PRIu32 "kB Speed:%" PRIu32 "MHz Mode:%s", flash_size, flash_speed,
+                          flash_mode);
 #endif
 
   esp_chip_info_t info;
@@ -182,52 +182,52 @@ size_t DebugComponent::get_device_info_(std::span<char, DEVICE_INFO_BUFFER_SIZE>
   const char *model = ESPHOME_VARIANT;
 
   // Build features string
-  pos = buf_append(buf, size, pos, "|Chip: %s Features:", model);
+  pos = buf_append_printf(buf, size, pos, "|Chip: %s Features:", model);
   bool first_feature = true;
   for (const auto &feature : CHIP_FEATURES) {
     if (info.features & feature.bit) {
-      pos = buf_append(buf, size, pos, "%s%s", first_feature ? "" : ", ", feature.name);
+      pos = buf_append_printf(buf, size, pos, "%s%s", first_feature ? "" : ", ", feature.name);
       first_feature = false;
       info.features &= ~feature.bit;
     }
   }
   if (info.features != 0) {
-    pos = buf_append(buf, size, pos, "%sOther:0x%" PRIx32, first_feature ? "" : ", ", info.features);
+    pos = buf_append_printf(buf, size, pos, "%sOther:0x%" PRIx32, first_feature ? "" : ", ", info.features);
   }
   ESP_LOGD(TAG, "Chip: Model=%s, Cores=%u, Revision=%u", model, info.cores, info.revision);
-  pos = buf_append(buf, size, pos, " Cores:%u Revision:%u", info.cores, info.revision);
+  pos = buf_append_printf(buf, size, pos, " Cores:%u Revision:%u", info.cores, info.revision);
 
   uint32_t cpu_freq_mhz = arch_get_cpu_freq_hz() / 1000000;
   ESP_LOGD(TAG, "CPU Frequency: %" PRIu32 " MHz", cpu_freq_mhz);
-  pos = buf_append(buf, size, pos, "|CPU Frequency: %" PRIu32 " MHz", cpu_freq_mhz);
+  pos = buf_append_printf(buf, size, pos, "|CPU Frequency: %" PRIu32 " MHz", cpu_freq_mhz);
 
   // Framework detection
 #ifdef USE_ARDUINO
   ESP_LOGD(TAG, "Framework: Arduino");
-  pos = buf_append(buf, size, pos, "|Framework: Arduino");
+  pos = buf_append_printf(buf, size, pos, "|Framework: Arduino");
 #elif defined(USE_ESP32)
   ESP_LOGD(TAG, "Framework: ESP-IDF");
-  pos = buf_append(buf, size, pos, "|Framework: ESP-IDF");
+  pos = buf_append_printf(buf, size, pos, "|Framework: ESP-IDF");
 #else
   ESP_LOGW(TAG, "Framework: UNKNOWN");
-  pos = buf_append(buf, size, pos, "|Framework: UNKNOWN");
+  pos = buf_append_printf(buf, size, pos, "|Framework: UNKNOWN");
 #endif
 
   ESP_LOGD(TAG, "ESP-IDF Version: %s", esp_get_idf_version());
-  pos = buf_append(buf, size, pos, "|ESP-IDF: %s", esp_get_idf_version());
+  pos = buf_append_printf(buf, size, pos, "|ESP-IDF: %s", esp_get_idf_version());
 
   uint8_t mac[6];
   get_mac_address_raw(mac);
   ESP_LOGD(TAG, "EFuse MAC: %02X:%02X:%02X:%02X:%02X:%02X", mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
-  pos = buf_append(buf, size, pos, "|EFuse MAC: %02X:%02X:%02X:%02X:%02X:%02X", mac[0], mac[1], mac[2], mac[3], mac[4],
-                   mac[5]);
+  pos = buf_append_printf(buf, size, pos, "|EFuse MAC: %02X:%02X:%02X:%02X:%02X:%02X", mac[0], mac[1], mac[2], mac[3],
+                          mac[4], mac[5]);
 
   char reason_buffer[RESET_REASON_BUFFER_SIZE];
   const char *reset_reason = get_reset_reason_(std::span<char, RESET_REASON_BUFFER_SIZE>(reason_buffer));
-  pos = buf_append(buf, size, pos, "|Reset: %s", reset_reason);
+  pos = buf_append_printf(buf, size, pos, "|Reset: %s", reset_reason);
 
   const char *wakeup_cause = get_wakeup_cause_(std::span<char, RESET_REASON_BUFFER_SIZE>(reason_buffer));
-  pos = buf_append(buf, size, pos, "|Wakeup: %s", wakeup_cause);
+  pos = buf_append_printf(buf, size, pos, "|Wakeup: %s", wakeup_cause);
 
   return pos;
 }

esphome/components/debug/debug_esp8266.cpp

@@ -53,8 +53,8 @@ size_t DebugComponent::get_device_info_(std::span<char, DEVICE_INFO_BUFFER_SIZE>
   uint32_t flash_size = ESP.getFlashChipSize() / 1024;       // NOLINT
   uint32_t flash_speed = ESP.getFlashChipSpeed() / 1000000;  // NOLINT
   ESP_LOGD(TAG, "Flash Chip: Size=%" PRIu32 "kB Speed=%" PRIu32 "MHz Mode=%s", flash_size, flash_speed, flash_mode);
-  pos = buf_append(buf, size, pos, "|Flash: %" PRIu32 "kB Speed:%" PRIu32 "MHz Mode:%s", flash_size, flash_speed,
-                   flash_mode);
+  pos = buf_append_printf(buf, size, pos, "|Flash: %" PRIu32 "kB Speed:%" PRIu32 "MHz Mode:%s", flash_size, flash_speed,
+                          flash_mode);
 
 #if !defined(CLANG_TIDY)
   char reason_buffer[RESET_REASON_BUFFER_SIZE];
@@ -77,15 +77,15 @@ size_t DebugComponent::get_device_info_(std::span<char, DEVICE_INFO_BUFFER_SIZE>
            chip_id, ESP.getSdkVersion(), ESP.getCoreVersion().c_str(), boot_version, boot_mode, cpu_freq, flash_chip_id,
            reset_reason, ESP.getResetInfo().c_str());
 
-  pos = buf_append(buf, size, pos, "|Chip: 0x%08" PRIX32, chip_id);
-  pos = buf_append(buf, size, pos, "|SDK: %s", ESP.getSdkVersion());
-  pos = buf_append(buf, size, pos, "|Core: %s", ESP.getCoreVersion().c_str());
-  pos = buf_append(buf, size, pos, "|Boot: %u", boot_version);
-  pos = buf_append(buf, size, pos, "|Mode: %u", boot_mode);
-  pos = buf_append(buf, size, pos, "|CPU: %u", cpu_freq);
-  pos = buf_append(buf, size, pos, "|Flash: 0x%08" PRIX32, flash_chip_id);
-  pos = buf_append(buf, size, pos, "|Reset: %s", reset_reason);
-  pos = buf_append(buf, size, pos, "|%s", ESP.getResetInfo().c_str());
+  pos = buf_append_printf(buf, size, pos, "|Chip: 0x%08" PRIX32, chip_id);
+  pos = buf_append_printf(buf, size, pos, "|SDK: %s", ESP.getSdkVersion());
+  pos = buf_append_printf(buf, size, pos, "|Core: %s", ESP.getCoreVersion().c_str());
+  pos = buf_append_printf(buf, size, pos, "|Boot: %u", boot_version);
+  pos = buf_append_printf(buf, size, pos, "|Mode: %u", boot_mode);
+  pos = buf_append_printf(buf, size, pos, "|CPU: %u", cpu_freq);
+  pos = buf_append_printf(buf, size, pos, "|Flash: 0x%08" PRIX32, flash_chip_id);
+  pos = buf_append_printf(buf, size, pos, "|Reset: %s", reset_reason);
+  pos = buf_append_printf(buf, size, pos, "|%s", ESP.getResetInfo().c_str());
 #endif
 
   return pos;

esphome/components/debug/debug_libretiny.cpp

@@ -36,12 +36,12 @@ size_t DebugComponent::get_device_info_(std::span<char, DEVICE_INFO_BUFFER_SIZE>
            lt_get_version(), lt_cpu_get_model_name(), lt_cpu_get_model(), lt_cpu_get_freq_mhz(), mac_id,
            lt_get_board_code(), flash_kib, ram_kib, reset_reason);
 
-  pos = buf_append(buf, size, pos, "|Version: %s", LT_BANNER_STR + 10);
-  pos = buf_append(buf, size, pos, "|Reset Reason: %s", reset_reason);
-  pos = buf_append(buf, size, pos, "|Chip Name: %s", lt_cpu_get_model_name());
-  pos = buf_append(buf, size, pos, "|Chip ID: 0x%06" PRIX32, mac_id);
-  pos = buf_append(buf, size, pos, "|Flash: %" PRIu32 " KiB", flash_kib);
-  pos = buf_append(buf, size, pos, "|RAM: %" PRIu32 " KiB", ram_kib);
+  pos = buf_append_printf(buf, size, pos, "|Version: %s", LT_BANNER_STR + 10);
+  pos = buf_append_printf(buf, size, pos, "|Reset Reason: %s", reset_reason);
+  pos = buf_append_printf(buf, size, pos, "|Chip Name: %s", lt_cpu_get_model_name());
+  pos = buf_append_printf(buf, size, pos, "|Chip ID: 0x%06" PRIX32, mac_id);
+  pos = buf_append_printf(buf, size, pos, "|Flash: %" PRIu32 " KiB", flash_kib);
+  pos = buf_append_printf(buf, size, pos, "|RAM: %" PRIu32 " KiB", ram_kib);
 
   return pos;
 }

esphome/components/debug/debug_rp2040.cpp

@@ -19,7 +19,7 @@ size_t DebugComponent::get_device_info_(std::span<char, DEVICE_INFO_BUFFER_SIZE>
 
   uint32_t cpu_freq = rp2040.f_cpu();
   ESP_LOGD(TAG, "CPU Frequency: %" PRIu32, cpu_freq);
-  pos = buf_append(buf, size, pos, "|CPU Frequency: %" PRIu32, cpu_freq);
+  pos = buf_append_printf(buf, size, pos, "|CPU Frequency: %" PRIu32, cpu_freq);
 
   return pos;
 }

esphome/components/debug/debug_zephyr.cpp

@@ -20,9 +20,9 @@ static size_t append_reset_reason(char *buf, size_t size, size_t pos, bool set,
     return pos;
   }
   if (pos > 0) {
-    pos = buf_append(buf, size, pos, ", ");
+    pos = buf_append_printf(buf, size, pos, ", ");
   }
-  return buf_append(buf, size, pos, "%s", reason);
+  return buf_append_printf(buf, size, pos, "%s", reason);
 }
 
 static inline uint32_t read_mem_u32(uintptr_t addr) {
@@ -140,7 +140,7 @@ size_t DebugComponent::get_device_info_(std::span<char, DEVICE_INFO_BUFFER_SIZE>
   const char *supply_status =
       (nrf_power_mainregstatus_get(NRF_POWER) == NRF_POWER_MAINREGSTATUS_NORMAL) ? "Normal voltage." : "High voltage.";
   ESP_LOGD(TAG, "Main supply status: %s", supply_status);
-  pos = buf_append(buf, size, pos, "|Main supply status: %s", supply_status);
+  pos = buf_append_printf(buf, size, pos, "|Main supply status: %s", supply_status);
 
   // Regulator stage 0
   if (nrf_power_mainregstatus_get(NRF_POWER) == NRF_POWER_MAINREGSTATUS_HIGH) {
@@ -172,16 +172,16 @@ size_t DebugComponent::get_device_info_(std::span<char, DEVICE_INFO_BUFFER_SIZE>
         reg0_voltage = "???V";
     }
     ESP_LOGD(TAG, "Regulator stage 0: %s, %s", reg0_type, reg0_voltage);
-    pos = buf_append(buf, size, pos, "|Regulator stage 0: %s, %s", reg0_type, reg0_voltage);
+    pos = buf_append_printf(buf, size, pos, "|Regulator stage 0: %s, %s", reg0_type, reg0_voltage);
   } else {
     ESP_LOGD(TAG, "Regulator stage 0: disabled");
-    pos = buf_append(buf, size, pos, "|Regulator stage 0: disabled");
+    pos = buf_append_printf(buf, size, pos, "|Regulator stage 0: disabled");
   }
 
   // Regulator stage 1
   const char *reg1_type = nrf_power_dcdcen_get(NRF_POWER) ? "DC/DC" : "LDO";
   ESP_LOGD(TAG, "Regulator stage 1: %s", reg1_type);
-  pos = buf_append(buf, size, pos, "|Regulator stage 1: %s", reg1_type);
+  pos = buf_append_printf(buf, size, pos, "|Regulator stage 1: %s", reg1_type);
 
   // USB power state
   const char *usb_state;
@@ -195,7 +195,7 @@ size_t DebugComponent::get_device_info_(std::span<char, DEVICE_INFO_BUFFER_SIZE>
     usb_state = "disconnected";
   }
   ESP_LOGD(TAG, "USB power state: %s", usb_state);
-  pos = buf_append(buf, size, pos, "|USB power state: %s", usb_state);
+  pos = buf_append_printf(buf, size, pos, "|USB power state: %s", usb_state);
 
   // Power-fail comparator
   bool enabled;
@@ -300,14 +300,14 @@ size_t DebugComponent::get_device_info_(std::span<char, DEVICE_INFO_BUFFER_SIZE>
           break;
       }
       ESP_LOGD(TAG, "Power-fail comparator: %s, VDDH: %s", pof_voltage, vddh_voltage);
-      pos = buf_append(buf, size, pos, "|Power-fail comparator: %s, VDDH: %s", pof_voltage, vddh_voltage);
+      pos = buf_append_printf(buf, size, pos, "|Power-fail comparator: %s, VDDH: %s", pof_voltage, vddh_voltage);
     } else {
       ESP_LOGD(TAG, "Power-fail comparator: %s", pof_voltage);
-      pos = buf_append(buf, size, pos, "|Power-fail comparator: %s", pof_voltage);
+      pos = buf_append_printf(buf, size, pos, "|Power-fail comparator: %s", pof_voltage);
     }
   } else {
     ESP_LOGD(TAG, "Power-fail comparator: disabled");
-    pos = buf_append(buf, size, pos, "|Power-fail comparator: disabled");
+    pos = buf_append_printf(buf, size, pos, "|Power-fail comparator: disabled");
   }
 
   auto package = [](uint32_t value) {

esphome/components/esp32_ble/ble_uuid.h

@@ -48,7 +48,7 @@ class ESPBTUUID {
 
   // Remove before 2026.8.0
   ESPDEPRECATED("Use to_str() instead. Removed in 2026.8.0", "2026.2.0")
-  std::string to_string() const;
+  std::string to_string() const;  // NOLINT
   const char *to_str(std::span<char, UUID_STR_LEN> output) const;
 
  protected:

esphome/components/lock/lock.cpp

@@ -28,16 +28,14 @@ const LogString *lock_state_to_string(LockState state) {
 Lock::Lock() : state(LOCK_STATE_NONE) {}
 LockCall Lock::make_call() { return LockCall(this); }
 
-void Lock::lock() {
+void Lock::set_state_(LockState state) {
   auto call = this->make_call();
-  call.set_state(LOCK_STATE_LOCKED);
-  this->control(call);
-}
-void Lock::unlock() {
-  auto call = this->make_call();
-  call.set_state(LOCK_STATE_UNLOCKED);
+  call.set_state(state);
   this->control(call);
 }
+
+void Lock::lock() { this->set_state_(LOCK_STATE_LOCKED); }
+void Lock::unlock() { this->set_state_(LOCK_STATE_UNLOCKED); }
 void Lock::open() {
   if (traits.get_supports_open()) {
     ESP_LOGD(TAG, "'%s' Opening.", this->get_name().c_str());

esphome/components/lock/lock.h

@@ -156,6 +156,9 @@ class Lock : public EntityBase {
  protected:
   friend LockCall;
 
+  /// Helper for lock/unlock convenience methods
+  void set_state_(LockState state);
+
   /** Perform the open latch action with hardware. This method is optional to implement
    * when creating a new lock.
    *

esphome/components/mapping/mapping.h

@@ -2,6 +2,7 @@
 
 #include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
+#include <cinttypes>
 #include <map>
 #include <string>
 
@@ -43,8 +44,17 @@ template<typename K, typename V> class Mapping {
       esph_log_e(TAG, "Key '%p' not found in mapping", key);
     } else if constexpr (std::is_same_v<K, std::string>) {
       esph_log_e(TAG, "Key '%s' not found in mapping", key.c_str());
+    } else if constexpr (std::is_integral_v<K>) {
+      char buf[24];  // enough for 64-bit integer
+      if constexpr (std::is_unsigned_v<K>) {
+        buf_append_printf(buf, sizeof(buf), 0, "%" PRIu64, static_cast<uint64_t>(key));
+      } else {
+        buf_append_printf(buf, sizeof(buf), 0, "%" PRId64, static_cast<int64_t>(key));
+      }
+      esph_log_e(TAG, "Key '%s' not found in mapping", buf);
     } else {
-      esph_log_e(TAG, "Key '%s' not found in mapping", to_string(key).c_str());
+      // All supported key types are handled above - this should never be reached
+      static_assert(sizeof(K) == 0, "Unsupported key type for Mapping error logging");
     }
     return {};
   }

esphome/components/mqtt/mqtt_client.cpp

@@ -403,6 +403,12 @@ void MQTTClientComponent::loop() {
 
         this->last_connected_ = now;
         this->resubscribe_subscriptions_();
+
+        // Process pending resends for all MQTT components centrally
+        // This is more efficient than each component polling in its own loop
+        for (MQTTComponent *component : this->children_) {
+          component->process_resend();
+        }
       }
       break;
   }

esphome/components/mqtt/mqtt_component.cpp

@@ -308,16 +308,12 @@ void MQTTComponent::call_setup() {
   }
 }
 
-void MQTTComponent::call_loop() {
-  if (this->is_internal())
+void MQTTComponent::process_resend() {
+  // Called by MQTTClientComponent when connected to process pending resends
+  // Note: is_internal() check not needed - internal components are never registered
+  if (!this->resend_state_)
     return;
 
-  this->loop();
-
-  if (!this->resend_state_ || !this->is_connected_()) {
-    return;
-  }
-
   this->resend_state_ = false;
   if (this->is_discovery_enabled()) {
     if (!this->send_discovery_()) {

esphome/components/mqtt/mqtt_component.h

@@ -81,8 +81,6 @@ class MQTTComponent : public Component {
   /// Override setup_ so that we can call send_discovery() when needed.
   void call_setup() override;
 
-  void call_loop() override;
-
   void call_dump_config() override;
 
   /// Send discovery info the Home Assistant, override this.
@@ -133,6 +131,9 @@ class MQTTComponent : public Component {
   /// Internal method for the MQTT client base to schedule a resend of the state on reconnect.
   void schedule_resend_state();
 
+  /// Process pending resend if needed (called by MQTTClientComponent)
+  void process_resend();
+
   /** Send a MQTT message.
    *
    * @param topic The topic.

esphome/components/statsd/statsd.cpp

@@ -114,14 +114,22 @@ void StatsdComponent::update() {
     // This implies you can't explicitly set a gauge to a negative number without first setting it to zero.
     if (val < 0) {
       if (this->prefix_) {
-        out.append(str_sprintf("%s.", this->prefix_));
+        out.append(this->prefix_);
+        out.append(".");
       }
-      out.append(str_sprintf("%s:0|g\n", s.name));
+      out.append(s.name);
+      out.append(":0|g\n");
     }
     if (this->prefix_) {
-      out.append(str_sprintf("%s.", this->prefix_));
+      out.append(this->prefix_);
+      out.append(".");
     }
-    out.append(str_sprintf("%s:%f|g\n", s.name, val));
+    out.append(s.name);
+    // Buffer for ":" + value + "|g\n".
+    // %f with -DBL_MAX can produce up to 321 chars, plus ":" and "|g\n" (4) + null = 326
+    char val_buf[330];
+    buf_append_printf(val_buf, sizeof(val_buf), 0, ":%f|g\n", val);
+    out.append(val_buf);
 
     if (out.length() > SEND_THRESHOLD) {
       this->send_(&out);

esphome/components/voice_assistant/voice_assistant.h

@@ -83,7 +83,7 @@ struct Timer {
   }
   // Remove before 2026.8.0
   ESPDEPRECATED("Use to_str() instead. Removed in 2026.8.0", "2026.2.0")
-  std::string to_string() const {
+  std::string to_string() const {  // NOLINT
     char buffer[TO_STR_BUFFER_SIZE];
     return this->to_str(buffer);
   }

script/ci-custom.py

@@ -732,6 +732,47 @@ def lint_no_heap_allocating_helpers(fname, match):
     )
 
 
+@lint_re_check(
+    # Match std::to_string() or unqualified to_string() calls
+    # The esphome namespace has "using std::to_string;" so unqualified calls resolve to std::to_string
+    # Use negative lookbehind to avoid matching:
+    #   - Function definitions: "const char *to_string(" or "std::string to_string("
+    #   - Method definitions: "Class::to_string("
+    #   - Method calls: ".to_string(" or "->to_string("
+    #   - Other identifiers: "_to_string("
+    r"(?<![*&.\w>:])to_string\s*\(" + CPP_RE_EOL,
+    include=cpp_include,
+    exclude=[
+        # Vendored library
+        "esphome/components/http_request/httplib.h",
+        # Deprecated helpers that return std::string
+        "esphome/core/helpers.cpp",
+        # The using declaration itself
+        "esphome/core/helpers.h",
+        # Test fixtures - not production embedded code
+        "tests/integration/fixtures/*",
+    ],
+)
+def lint_no_std_to_string(fname, match):
+    return (
+        f"{highlight('std::to_string()')} allocates heap memory. On long-running embedded "
+        f"devices, repeated heap allocations fragment memory over time.\n"
+        f"Please use {highlight('snprintf()')} with a stack buffer instead.\n"
+        f"\n"
+        f"Buffer sizes and format specifiers:\n"
+        f"  uint8_t/int8_t:   4 chars   - %u / %d (or PRIu8/PRId8)\n"
+        f"  uint16_t/int16_t: 6 chars   - %u / %d (or PRIu16/PRId16)\n"
+        f"  uint32_t/int32_t: 11 chars  - %" + "PRIu32 / %" + "PRId32\n"
+        "  uint64_t/int64_t: 21 chars  - %" + "PRIu64 / %" + "PRId64\n"
+        f"  float/double:     24 chars  - %.8g (15 digits + sign + decimal + e+XXX)\n"
+        f"                    317 chars - %f (for DBL_MAX: 309 int digits + decimal + 6 frac + sign)\n"
+        f"\n"
+        f"For sensor values, use value_accuracy_to_buf() from helpers.h.\n"
+        f'Example: char buf[11]; snprintf(buf, sizeof(buf), "%" PRIu32, value);\n'
+        f"(If strictly necessary, add `{highlight('// NOLINT')}` to the end of the line)"
+    )
+
+
 @lint_content_find_check(
     "ESP_LOG",
     include=["*.h", "*.tcc"],