Merge branch 'dev' into ard_debug_no_heap

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

esphome/components/api/api_connection.cpp

@@ -1712,17 +1712,16 @@ 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, 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
+    // 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);
     }
-    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));
+    state_buf[state_len] = '\0';
+    it.callback(StringRef(state_buf, state_len));
   }
 }
 #endif

esphome/components/api/proto.cpp

@@ -48,14 +48,14 @@ uint32_t ProtoDecodableMessage::count_repeated_field(const uint8_t *buffer, size
         }
         uint32_t field_length = res->as_uint32();
         ptr += consumed;
-        if (ptr + field_length > end) {
+        if (field_length > static_cast<size_t>(end - ptr)) {
           return count;  // Out of bounds
         }
         ptr += field_length;
         break;
       }
       case WIRE_TYPE_FIXED32: {  // 32-bit - skip 4 bytes
-        if (ptr + 4 > end) {
+        if (end - ptr < 4) {
           return count;
         }
         ptr += 4;
@@ -110,7 +110,7 @@ void ProtoDecodableMessage::decode(const uint8_t *buffer, size_t length) {
         }
         uint32_t field_length = res->as_uint32();
         ptr += consumed;
-        if (ptr + field_length > end) {
+        if (field_length > static_cast<size_t>(end - ptr)) {
           ESP_LOGV(TAG, "Out-of-bounds Length Delimited at offset %ld", (long) (ptr - buffer));
           return;
         }
@@ -121,7 +121,7 @@ void ProtoDecodableMessage::decode(const uint8_t *buffer, size_t length) {
         break;
       }
       case WIRE_TYPE_FIXED32: {  // 32-bit
-        if (ptr + 4 > end) {
+        if (end - ptr < 4) {
           ESP_LOGV(TAG, "Out-of-bounds Fixed32-bit at offset %ld", (long) (ptr - buffer));
           return;
         }

esphome/components/atm90e32/atm90e32.cpp

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

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

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
-    sprintf(version, "%d.%d.%d (0x%02x)", (application_version >> 12 & 15), (application_version >> 8 & 15),
-            (application_version >> 4 & 15), application_version);
+    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);
     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 snprintf(buffer, len, "EXIO%u via CH422G", this->pin_);
+  return buf_append_printf(buffer, len, 0, "EXIO%u via CH422G", this->pin_);
 }
 void CH422GGPIOPin::set_flags(gpio::Flags flags) {
   flags_ = flags;

esphome/components/cse7766/cse7766.cpp

@@ -207,20 +207,24 @@ void CSE7766Component::parse_data_() {
 
 #if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_VERY_VERBOSE
   {
-    std::string buf = "Parsed:";
+    // 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:");
     if (have_voltage) {
-      buf += str_sprintf(" V=%fV", voltage);
+      pos = buf_append_printf(buf, sizeof(buf), pos, " V=%.4fV", voltage);
     }
     if (have_current) {
-      buf += str_sprintf(" I=%fmA (~%fmA)", current * 1000.0f, calculated_current * 1000.0f);
+      pos = buf_append_printf(buf, sizeof(buf), pos, " I=%.4fmA (~%.4fmA)", current * 1000.0f,
+                              calculated_current * 1000.0f);
     }
     if (have_power) {
-      buf += str_sprintf(" P=%fW", power);
+      pos = buf_append_printf(buf, sizeof(buf), pos, " P=%.4fW", power);
     }
     if (energy != 0.0f) {
-      buf += str_sprintf(" E=%fkWh (%u)", energy, cf_pulses);
+      buf_append_printf(buf, sizeof(buf), pos, " E=%.4fkWh (%u)", energy, cf_pulses);
     }
-    ESP_LOGVV(TAG, "%s", buf.c_str());
+    ESP_LOGVV(TAG, "%s", buf);
   }
 #endif
 }

esphome/components/daikin_arc/daikin_arc.cpp

@@ -258,8 +258,9 @@ 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++) {
-    sprintf(buf, "%s%02x ", buf, frame[i]);
+    pos = buf_append_printf(buf, sizeof(buf), pos, "%02x ", frame[i]);
   }
   ESP_LOGD(TAG, "FRAME %s", buf);
 
@@ -349,8 +350,9 @@ 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;
-    std::unique_ptr<char[]> buf(new char[bytes_count * 3 + 1]);
-    buf[0] = '\0';
+    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;
     for (size_t i = 0; i < bytes_count; i++) {
       uint8_t byte = 0;
       for (int8_t bit = 0; bit < 8; bit++) {
@@ -361,19 +363,19 @@ bool DaikinArcClimate::on_receive(remote_base::RemoteReceiveData data) {
           break;
         }
       }
-      sprintf(buf.get(), "%s%02x ", buf.get(), byte);
+      buf_pos = buf_append_printf(buf.get(), buf_size, buf_pos, "%02x ", byte);
     }
     ESP_LOGD(TAG, "WHOLE FRAME %s  size: %d", buf.get(), data.size());
   }
   if (!valid_daikin_frame) {
-    char sbuf[16 * 10 + 1];
-    sbuf[0] = '\0';
+    char sbuf[16 * 10 + 1] = {0};
+    size_t sbuf_pos = 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[0] = '\0';
+        sbuf_pos = 0;
       }
       char type_ch = ' ';
       // debug_tolerance = 25%
@@ -401,9 +403,10 @@ bool DaikinArcClimate::on_receive(remote_base::RemoteReceiveData data) {
         type_ch = '0';
 
       if (abs(data[j]) > 100000) {
-        sprintf(sbuf, "%s%-5d[%c] ", sbuf, data[j] > 0 ? 99999 : -99999, type_ch);
+        sbuf_pos = buf_append_printf(sbuf, sizeof(sbuf), sbuf_pos, "%-5d[%c] ", data[j] > 0 ? 99999 : -99999, type_ch);
       } else {
-        sprintf(sbuf, "%s%-5d[%c] ", sbuf, (int) (round(data[j] / 10.) * 10), type_ch);
+        sbuf_pos =
+            buf_append_printf(sbuf, sizeof(sbuf), sbuf_pos, "%-5d[%c] ", (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/debug/debug_esp8266.cpp

@@ -3,21 +3,80 @@
 #include "esphome/core/log.h"
 #include <Esp.h>
 
+extern "C" {
+#include <user_interface.h>
+
+// Global reset info struct populated by SDK at boot
+extern struct rst_info resetInfo;
+
+// Core version - either a string pointer or a version number to format as hex
+extern uint32_t core_version;
+extern const char *core_release;
+}
+
 namespace esphome {
 namespace debug {
 
 static const char *const TAG = "debug";
 
+// Get reset reason string from reason code (no heap allocation)
+// Returns LogString* pointing to flash (PROGMEM) on ESP8266
+static const LogString *get_reset_reason_str(uint32_t reason) {
+  switch (reason) {
+    case REASON_DEFAULT_RST:
+      return LOG_STR("Power On");
+    case REASON_WDT_RST:
+      return LOG_STR("Hardware Watchdog");
+    case REASON_EXCEPTION_RST:
+      return LOG_STR("Exception");
+    case REASON_SOFT_WDT_RST:
+      return LOG_STR("Software Watchdog");
+    case REASON_SOFT_RESTART:
+      return LOG_STR("Software/System restart");
+    case REASON_DEEP_SLEEP_AWAKE:
+      return LOG_STR("Deep-Sleep Wake");
+    case REASON_EXT_SYS_RST:
+      return LOG_STR("External System");
+    default:
+      return LOG_STR("Unknown");
+  }
+}
+
+// Size for core version hex buffer
+static constexpr size_t CORE_VERSION_BUFFER_SIZE = 12;
+
+// Get core version string (no heap allocation)
+// Returns either core_release directly or formats core_version as hex into provided buffer
+static const char *get_core_version_str(std::span<char, CORE_VERSION_BUFFER_SIZE> buffer) {
+  if (core_release != nullptr) {
+    return core_release;
+  }
+  snprintf_P(buffer.data(), CORE_VERSION_BUFFER_SIZE, PSTR("%08x"), core_version);
+  return buffer.data();
+}
+
+// Size for reset info buffer
+static constexpr size_t RESET_INFO_BUFFER_SIZE = 200;
+
+// Get detailed reset info string (no heap allocation)
+// For watchdog/exception resets, includes detailed exception info
+static const char *get_reset_info_str(std::span<char, RESET_INFO_BUFFER_SIZE> buffer, uint32_t reason) {
+  if (reason >= REASON_WDT_RST && reason <= REASON_SOFT_WDT_RST) {
+    snprintf_P(buffer.data(), RESET_INFO_BUFFER_SIZE,
+               PSTR("Fatal exception:%d flag:%d (%s) epc1:0x%08x epc2:0x%08x epc3:0x%08x excvaddr:0x%08x depc:0x%08x"),
+               static_cast<int>(resetInfo.exccause), static_cast<int>(reason),
+               LOG_STR_ARG(get_reset_reason_str(reason)), resetInfo.epc1, resetInfo.epc2, resetInfo.epc3,
+               resetInfo.excvaddr, resetInfo.depc);
+    return buffer.data();
+  }
+  return LOG_STR_ARG(get_reset_reason_str(reason));
+}
+
 const char *DebugComponent::get_reset_reason_(std::span<char, RESET_REASON_BUFFER_SIZE> buffer) {
-  char *buf = buffer.data();
-#if !defined(CLANG_TIDY)
-  String reason = ESP.getResetReason();  // NOLINT
-  snprintf_P(buf, RESET_REASON_BUFFER_SIZE, PSTR("%s"), reason.c_str());
-  return buf;
-#else
-  buf[0] = '\0';
-  return buf;
-#endif
+  // Copy from flash to provided buffer
+  strncpy_P(buffer.data(), (PGM_P) get_reset_reason_str(resetInfo.reason), RESET_REASON_BUFFER_SIZE - 1);
+  buffer[RESET_REASON_BUFFER_SIZE - 1] = '\0';
+  return buffer.data();
 }
 
 const char *DebugComponent::get_wakeup_cause_(std::span<char, RESET_REASON_BUFFER_SIZE> buffer) {
@@ -33,37 +92,42 @@ size_t DebugComponent::get_device_info_(std::span<char, DEVICE_INFO_BUFFER_SIZE>
   constexpr size_t size = DEVICE_INFO_BUFFER_SIZE;
   char *buf = buffer.data();
 
-  const char *flash_mode;
+  const LogString *flash_mode;
   switch (ESP.getFlashChipMode()) {  // NOLINT(readability-static-accessed-through-instance)
     case FM_QIO:
-      flash_mode = "QIO";
+      flash_mode = LOG_STR("QIO");
       break;
     case FM_QOUT:
-      flash_mode = "QOUT";
+      flash_mode = LOG_STR("QOUT");
       break;
     case FM_DIO:
-      flash_mode = "DIO";
+      flash_mode = LOG_STR("DIO");
       break;
     case FM_DOUT:
-      flash_mode = "DOUT";
+      flash_mode = LOG_STR("DOUT");
       break;
     default:
-      flash_mode = "UNKNOWN";
+      flash_mode = LOG_STR("UNKNOWN");
   }
-  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);
+  uint32_t flash_size = ESP.getFlashChipSize() / 1024;       // NOLINT(readability-static-accessed-through-instance)
+  uint32_t flash_speed = ESP.getFlashChipSpeed() / 1000000;  // NOLINT(readability-static-accessed-through-instance)
+  ESP_LOGD(TAG, "Flash Chip: Size=%" PRIu32 "kB Speed=%" PRIu32 "MHz Mode=%s", flash_size, flash_speed,
+           LOG_STR_ARG(flash_mode));
+  pos = buf_append_printf(buf, size, pos, "|Flash: %" PRIu32 "kB Speed:%" PRIu32 "MHz Mode:%s", flash_size, flash_speed,
+                          LOG_STR_ARG(flash_mode));
 
-#if !defined(CLANG_TIDY)
   char reason_buffer[RESET_REASON_BUFFER_SIZE];
-  const char *reset_reason = get_reset_reason_(std::span<char, RESET_REASON_BUFFER_SIZE>(reason_buffer));
+  const char *reset_reason = get_reset_reason_(reason_buffer);
+  char core_version_buffer[CORE_VERSION_BUFFER_SIZE];
+  char reset_info_buffer[RESET_INFO_BUFFER_SIZE];
+  // NOLINTBEGIN(readability-static-accessed-through-instance)
   uint32_t chip_id = ESP.getChipId();
   uint8_t boot_version = ESP.getBootVersion();
   uint8_t boot_mode = ESP.getBootMode();
   uint8_t cpu_freq = ESP.getCpuFreqMHz();
   uint32_t flash_chip_id = ESP.getFlashChipId();
+  const char *sdk_version = ESP.getSdkVersion();
+  // NOLINTEND(readability-static-accessed-through-instance)
 
   ESP_LOGD(TAG,
            "Chip ID: 0x%08" PRIX32 "\n"
@@ -74,19 +138,18 @@ size_t DebugComponent::get_device_info_(std::span<char, DEVICE_INFO_BUFFER_SIZE>
            "Flash Chip ID=0x%08" PRIX32 "\n"
            "Reset Reason: %s\n"
            "Reset Info: %s",
-           chip_id, ESP.getSdkVersion(), ESP.getCoreVersion().c_str(), boot_version, boot_mode, cpu_freq, flash_chip_id,
-           reset_reason, ESP.getResetInfo().c_str());
+           chip_id, sdk_version, get_core_version_str(core_version_buffer), boot_version, boot_mode, cpu_freq,
+           flash_chip_id, reset_reason, get_reset_info_str(reset_info_buffer, resetInfo.reason));
 
-  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());
-#endif
+  pos = buf_append_printf(buf, size, pos, "|Chip: 0x%08" PRIX32, chip_id);
+  pos = buf_append_printf(buf, size, pos, "|SDK: %s", sdk_version);
+  pos = buf_append_printf(buf, size, pos, "|Core: %s", get_core_version_str(core_version_buffer));
+  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", get_reset_info_str(reset_info_buffer, resetInfo.reason));
 
   return pos;
 }

esphome/components/dfrobot_sen0395/commands.cpp

@@ -127,7 +127,9 @@ 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;
 
-    this->cmd_ = str_sprintf("detRangeCfg -1 %.0f %.0f", min1 / 0.15, max1 / 0.15);
+    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;
   } else if (min3 < 0 || max3 < 0) {
     this->min1_ = min1 = round(min1 / 0.15) * 0.15;
     this->max1_ = max1 = round(max1 / 0.15) * 0.15;
@@ -135,7 +137,10 @@ 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;
 
-    this->cmd_ = str_sprintf("detRangeCfg -1 %.0f %.0f %.0f %.0f", min1 / 0.15, max1 / 0.15, min2 / 0.15, max2 / 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", min1 / 0.15, max1 / 0.15, min2 / 0.15,
+             max2 / 0.15);
+    this->cmd_ = buf;
   } else if (min4 < 0 || max4 < 0) {
     this->min1_ = min1 = round(min1 / 0.15) * 0.15;
     this->max1_ = max1 = round(max1 / 0.15) * 0.15;
@@ -145,9 +150,10 @@ 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;
 
-    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);
+    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;
   } else {
     this->min1_ = min1 = round(min1 / 0.15) * 0.15;
     this->max1_ = max1 = round(max1 / 0.15) * 0.15;
@@ -158,10 +164,10 @@ 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;
 
-    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);
+    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->min1_ = min1;
@@ -203,7 +209,10 @@ 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);
-  this->cmd_ = str_sprintf("setLatency %.03f %.03f", this->delay_after_detection_, this->delay_after_disappear_);
+  // 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;
 };
 
 uint8_t SetLatencyCommand::on_message(std::string &message) {

esphome/components/esp32_hosted/update/esp32_hosted_update.cpp

@@ -69,7 +69,10 @@ void Esp32HostedUpdate::setup() {
   // Get coprocessor version
   esp_hosted_coprocessor_fwver_t ver_info;
   if (esp_hosted_get_coprocessor_fwversion(&ver_info) == ESP_OK) {
-    this->update_info_.current_version = str_sprintf("%d.%d.%d", ver_info.major1, ver_info.minor1, ver_info.patch1);
+    // 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;
   } else {
     this->update_info_.current_version = "unknown";
   }

esphome/components/esp8266/core.cpp

@@ -6,7 +6,11 @@
 #include "esphome/core/helpers.h"
 #include "preferences.h"
 #include <Arduino.h>
-#include <Esp.h>
+#include <core_esp8266_features.h>
+
+extern "C" {
+#include <user_interface.h>
+}
 
 namespace esphome {
 
@@ -16,23 +20,19 @@ 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() {
-  ESP.restart();  // NOLINT(readability-static-accessed-through-instance)
+  system_restart();
   // restart() doesn't always end execution
   while (true) {  // NOLINT(clang-diagnostic-unreachable-code)
     yield();
   }
 }
 void arch_init() {}
-void IRAM_ATTR HOT arch_feed_wdt() {
-  ESP.wdtFeed();  // NOLINT(readability-static-accessed-through-instance)
-}
+void IRAM_ATTR HOT arch_feed_wdt() { system_soft_wdt_feed(); }
 
 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.getCycleCount();  // NOLINT(readability-static-accessed-through-instance)
-}
+uint32_t IRAM_ATTR HOT arch_get_cpu_cycle_count() { return esp_get_cycle_count(); }
 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 snprintf(buffer, len, "GPIO%u", this->pin_);
+  return buf_append_printf(buffer, len, 0, "GPIO%u", this->pin_);
 }
 
 bool ESP8266GPIOPin::digital_read() {

esphome/components/ezo/ezo.cpp

@@ -160,7 +160,7 @@ void EZOSensor::loop() {
   this->commands_.pop_front();
 }
 
-void EZOSensor::add_command_(const std::string &command, EzoCommandType command_type, uint16_t delay_ms) {
+void EZOSensor::add_command_(const char *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;
@@ -169,13 +169,17 @@ void EZOSensor::add_command_(const std::string &command, EzoCommandType command_
 }
 
 void EZOSensor::set_calibration_point_(EzoCalibrationType type, float value) {
-  std::string payload = str_sprintf("Cal,%s,%0.2f", EZO_CALIBRATION_TYPE_STRINGS[type], 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);
   this->add_command_(payload, EzoCommandType::EZO_CALIBRATION, 900);
 }
 
 void EZOSensor::set_address(uint8_t address) {
   if (address > 0 && address < 128) {
-    std::string payload = str_sprintf("I2C,%u", address);
+    // max 8: "I2C,"(4) + uint8(3) + null
+    char payload[8];
+    snprintf(payload, sizeof(payload), "I2C,%u", address);
     this->new_address_ = address;
     this->add_command_(payload, EzoCommandType::EZO_I2C);
   } else {
@@ -194,7 +198,9 @@ 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) {
-  std::string payload = str_sprintf("T,%0.2f", 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);
   this->add_command_(payload, EzoCommandType::EZO_T);
 }
 
@@ -215,7 +221,9 @@ void EZOSensor::set_calibration_point_high(float value) {
 }
 
 void EZOSensor::set_calibration_generic(float value) {
-  std::string payload = str_sprintf("Cal,%0.2f", 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);
   this->add_command_(payload, EzoCommandType::EZO_CALIBRATION, 900);
 }
 
@@ -223,13 +231,11 @@ 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) {
-  std::string to_send = "L,";
-  to_send += on ? "1" : "0";
-  this->add_command_(to_send, 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, EzoCommandType::EZO_CUSTOM); }
+void EZOSensor::send_custom(const std::string &to_send) {
+  this->add_command_(to_send.c_str(), 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 std::string &command, EzoCommandType command_type, uint16_t delay_ms = 300);
+  void add_command_(const char *command, EzoCommandType command_type, uint16_t delay_ms = 300);
 
   void set_calibration_point_(EzoCalibrationType type, float value);
 

esphome/components/gdk101/gdk101.cpp

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

esphome/components/hmac_sha256/hmac_sha256.cpp

@@ -1,4 +1,3 @@
-#include <cstdio>
 #include <cstring>
 #include "hmac_sha256.h"
 #if defined(USE_ESP32) || defined(USE_ESP8266) || defined(USE_RP2040) || defined(USE_LIBRETINY) || defined(USE_HOST)
@@ -26,9 +25,7 @@ void HmacSHA256::calculate() { mbedtls_md_hmac_finish(&this->ctx_, this->digest_
 void HmacSHA256::get_bytes(uint8_t *output) { memcpy(output, this->digest_, SHA256_DIGEST_SIZE); }
 
 void HmacSHA256::get_hex(char *output) {
-  for (size_t i = 0; i < SHA256_DIGEST_SIZE; i++) {
-    sprintf(output + (i * 2), "%02x", this->digest_[i]);
-  }
+  format_hex_to(output, SHA256_DIGEST_SIZE * 2 + 1, this->digest_, SHA256_DIGEST_SIZE);
 }
 
 bool HmacSHA256::equals_bytes(const uint8_t *expected) {

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];
-  snprintf(value_buf, sizeof(value_buf), "%g", value);
+  buf_append_printf(value_buf, sizeof(value_buf), 0, "%g", value);
   entity_value.value = StringRef(value_buf);
 
   api::global_api_server->send_homeassistant_action(resp);

esphome/components/http_request/http_request.h

@@ -242,9 +242,7 @@ template<typename... Ts> class HttpRequestSendAction : public Action<Ts...> {
       return;
     }
 
-    size_t content_length = container->content_length;
-    size_t max_length = std::min(content_length, this->max_response_buffer_size_);
-
+    size_t max_length = this->max_response_buffer_size_;
 #ifdef USE_HTTP_REQUEST_RESPONSE
     if (this->capture_response_.value(x...)) {
       std::string response_body;

esphome/components/http_request/http_request_idf.cpp

@@ -213,18 +213,12 @@ int HttpContainerIDF::read(uint8_t *buf, size_t max_len) {
   const uint32_t start = millis();
   watchdog::WatchdogManager wdm(this->parent_->get_watchdog_timeout());
 
-  int bufsize = std::min(max_len, this->content_length - this->bytes_read_);
-
-  if (bufsize == 0) {
-    this->duration_ms += (millis() - start);
-    return 0;
+  this->feed_wdt();
+  int read_len = esp_http_client_read(this->client_, (char *) buf, max_len);
+  this->feed_wdt();
+  if (read_len > 0) {
+    this->bytes_read_ += read_len;
   }
-
-  this->feed_wdt();
-  int read_len = esp_http_client_read(this->client_, (char *) buf, bufsize);
-  this->feed_wdt();
-  this->bytes_read_ += read_len;
-
   this->duration_ms += (millis() - start);
 
   return read_len;

esphome/components/hub75/display.py

@@ -1,3 +1,4 @@
+import logging
 from typing import Any
 
 from esphome import automation, pins
@@ -18,13 +19,16 @@ from esphome.const import (
     CONF_ROTATION,
     CONF_UPDATE_INTERVAL,
 )
-from esphome.core import ID
+from esphome.core import ID, EnumValue
 from esphome.cpp_generator import MockObj, TemplateArgsType
 import esphome.final_validate as fv
+from esphome.helpers import add_class_to_obj
 from esphome.types import ConfigType
 
 from . import boards, hub75_ns
 
+_LOGGER = logging.getLogger(__name__)
+
 DEPENDENCIES = ["esp32"]
 CODEOWNERS = ["@stuartparmenter"]
 
@@ -120,13 +124,51 @@ PANEL_LAYOUTS = {
 }
 
 Hub75ScanWiring = cg.global_ns.enum("Hub75ScanWiring", is_class=True)
-SCAN_PATTERNS = {
+SCAN_WIRINGS = {
     "STANDARD_TWO_SCAN": Hub75ScanWiring.STANDARD_TWO_SCAN,
-    "FOUR_SCAN_16PX_HIGH": Hub75ScanWiring.FOUR_SCAN_16PX_HIGH,
-    "FOUR_SCAN_32PX_HIGH": Hub75ScanWiring.FOUR_SCAN_32PX_HIGH,
-    "FOUR_SCAN_64PX_HIGH": Hub75ScanWiring.FOUR_SCAN_64PX_HIGH,
+    "SCAN_1_4_16PX_HIGH": Hub75ScanWiring.SCAN_1_4_16PX_HIGH,
+    "SCAN_1_8_32PX_HIGH": Hub75ScanWiring.SCAN_1_8_32PX_HIGH,
+    "SCAN_1_8_40PX_HIGH": Hub75ScanWiring.SCAN_1_8_40PX_HIGH,
+    "SCAN_1_8_64PX_HIGH": Hub75ScanWiring.SCAN_1_8_64PX_HIGH,
 }
 
+# Deprecated scan wiring names - mapped to new names
+DEPRECATED_SCAN_WIRINGS = {
+    "FOUR_SCAN_16PX_HIGH": "SCAN_1_4_16PX_HIGH",
+    "FOUR_SCAN_32PX_HIGH": "SCAN_1_8_32PX_HIGH",
+    "FOUR_SCAN_64PX_HIGH": "SCAN_1_8_64PX_HIGH",
+}
+
+
+def _validate_scan_wiring(value):
+    """Validate scan_wiring with deprecation warnings for old names."""
+    value = cv.string(value).upper().replace(" ", "_")
+
+    # Check if using deprecated name
+    # Remove deprecated names in 2026.7.0
+    if value in DEPRECATED_SCAN_WIRINGS:
+        new_name = DEPRECATED_SCAN_WIRINGS[value]
+        _LOGGER.warning(
+            "Scan wiring '%s' is deprecated and will be removed in ESPHome 2026.7.0. "
+            "Please use '%s' instead.",
+            value,
+            new_name,
+        )
+        value = new_name
+
+    # Validate against allowed values
+    if value not in SCAN_WIRINGS:
+        raise cv.Invalid(
+            f"Unknown scan wiring '{value}'. "
+            f"Valid options are: {', '.join(sorted(SCAN_WIRINGS.keys()))}"
+        )
+
+    # Return as EnumValue like cv.enum does
+    result = add_class_to_obj(value, EnumValue)
+    result.enum_value = SCAN_WIRINGS[value]
+    return result
+
+
 Hub75ClockSpeed = cg.global_ns.enum("Hub75ClockSpeed", is_class=True)
 CLOCK_SPEEDS = {
     "8MHZ": Hub75ClockSpeed.HZ_8M,
@@ -382,9 +424,7 @@ CONFIG_SCHEMA = cv.All(
             cv.Optional(CONF_LAYOUT_COLS): cv.positive_int,
             cv.Optional(CONF_LAYOUT): cv.enum(PANEL_LAYOUTS, upper=True, space="_"),
             # Panel hardware configuration
-            cv.Optional(CONF_SCAN_WIRING): cv.enum(
-                SCAN_PATTERNS, upper=True, space="_"
-            ),
+            cv.Optional(CONF_SCAN_WIRING): _validate_scan_wiring,
             cv.Optional(CONF_SHIFT_DRIVER): cv.enum(SHIFT_DRIVERS, upper=True),
             # Display configuration
             cv.Optional(CONF_DOUBLE_BUFFER): cv.boolean,
@@ -547,7 +587,7 @@ def _build_config_struct(
 async def to_code(config: ConfigType) -> None:
     add_idf_component(
         name="esphome/esp-hub75",
-        ref="0.2.2",
+        ref="0.3.0",
     )
 
     # Set compile-time configuration via build flags (so external library sees them)

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;  // Most I2C writes are <= 16 bytes
-  uint8_t *buffer = buffer_alloc.get(len + 1);
+  SmallBufferWithHeapFallback<17> buffer_alloc(len + 1);  // Most I2C writes are <= 16 bytes
+  uint8_t *buffer = buffer_alloc.get();
 
   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;  // Most I2C writes are <= 16 bytes + 2 for register
-  uint8_t *buffer = buffer_alloc.get(len + 2);
+  SmallBufferWithHeapFallback<18> buffer_alloc(len + 2);  // Most I2C writes are <= 16 bytes + 2 for register
+  uint8_t *buffer = buffer_alloc.get();
 
   buffer[0] = a_register >> 8;
   buffer[1] = a_register;

esphome/components/i2c/i2c_bus.h

@@ -11,22 +11,6 @@
 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
@@ -92,8 +76,8 @@ class I2CBus {
       total_len += read_buffers[i].len;
     }
 
-    SmallBufferWithHeapFallback<128> buffer_alloc;  // Most I2C reads are small
-    uint8_t *buffer = buffer_alloc.get(total_len);
+    SmallBufferWithHeapFallback<128> buffer_alloc(total_len);  // Most I2C reads are small
+    uint8_t *buffer = buffer_alloc.get();
 
     auto err = this->write_readv(address, nullptr, 0, buffer, total_len);
     if (err != ERROR_OK)
@@ -116,8 +100,8 @@ class I2CBus {
       total_len += write_buffers[i].len;
     }
 
-    SmallBufferWithHeapFallback<128> buffer_alloc;  // Most I2C writes are small
-    uint8_t *buffer = buffer_alloc.get(total_len);
+    SmallBufferWithHeapFallback<128> buffer_alloc(total_len);  // Most I2C writes are small
+    uint8_t *buffer = buffer_alloc.get();
 
     size_t pos = 0;
     for (size_t i = 0; i != count; i++) {

esphome/components/infrared/infrared.cpp

@@ -19,12 +19,12 @@ InfraredCall &InfraredCall::set_carrier_frequency(uint32_t frequency) {
 InfraredCall &InfraredCall::set_raw_timings(const std::vector<int32_t> &timings) {
   this->raw_timings_ = &timings;
   this->packed_data_ = nullptr;
-  this->base85_ptr_ = nullptr;
+  this->base64url_ptr_ = nullptr;
   return *this;
 }
 
-InfraredCall &InfraredCall::set_raw_timings_base85(const std::string &base85) {
-  this->base85_ptr_ = &base85;
+InfraredCall &InfraredCall::set_raw_timings_base64url(const std::string &base64url) {
+  this->base64url_ptr_ = &base64url;
   this->raw_timings_ = nullptr;
   this->packed_data_ = nullptr;
   return *this;
@@ -35,7 +35,7 @@ InfraredCall &InfraredCall::set_raw_timings_packed(const uint8_t *data, uint16_t
   this->packed_length_ = length;
   this->packed_count_ = count;
   this->raw_timings_ = nullptr;
-  this->base85_ptr_ = nullptr;
+  this->base64url_ptr_ = nullptr;
   return *this;
 }
 
@@ -101,13 +101,22 @@ void Infrared::control(const InfraredCall &call) {
                                                call.get_packed_count());
     ESP_LOGD(TAG, "Transmitting packed raw timings: count=%u, repeat=%u", call.get_packed_count(),
              call.get_repeat_count());
-  } else if (call.is_base85()) {
-    // Decode base85 directly into transmit buffer (zero heap allocations)
-    if (!transmit_data->set_data_from_base85(call.get_base85_data())) {
-      ESP_LOGE(TAG, "Invalid base85 data");
+  } else if (call.is_base64url()) {
+    // Decode base64url (URL-safe) into transmit buffer
+    if (!transmit_data->set_data_from_base64url(call.get_base64url_data())) {
+      ESP_LOGE(TAG, "Invalid base64url data");
       return;
     }
-    ESP_LOGD(TAG, "Transmitting base85 raw timings: count=%zu, repeat=%u", transmit_data->get_data().size(),
+    // Sanity check: validate timing values are within reasonable bounds
+    constexpr int32_t max_timing_us = 500000;  // 500ms absolute max
+    for (int32_t timing : transmit_data->get_data()) {
+      int32_t abs_timing = timing < 0 ? -timing : timing;
+      if (abs_timing > max_timing_us) {
+        ESP_LOGE(TAG, "Invalid timing value: %d µs (max %d)", timing, max_timing_us);
+        return;
+      }
+    }
+    ESP_LOGD(TAG, "Transmitting base64url raw timings: count=%zu, repeat=%u", transmit_data->get_data().size(),
              call.get_repeat_count());
   } else {
     // From vector (lambdas/automations)

esphome/components/infrared/infrared.h

@@ -40,11 +40,11 @@ class InfraredCall {
   /// @note Usage: Primarily for lambdas/automations where the vector is in scope.
   InfraredCall &set_raw_timings(const std::vector<int32_t> &timings);
 
-  /// Set the raw timings from base85-encoded int32 data
+  /// Set the raw timings from base64url-encoded little-endian int32 data
   /// @note Lifetime: Stores a pointer to the string. The string must outlive perform().
-  /// @note Usage: For web_server where the encoded string is on the stack.
+  /// @note Usage: For web_server - base64url is fully URL-safe (uses '-' and '_').
   /// @note Decoding happens at perform() time, directly into the transmit buffer.
-  InfraredCall &set_raw_timings_base85(const std::string &base85);
+  InfraredCall &set_raw_timings_base64url(const std::string &base64url);
 
   /// Set the raw timings from packed protobuf sint32 data (zigzag + varint encoded)
   /// @note Lifetime: Stores a pointer to the buffer. The buffer must outlive perform().
@@ -59,18 +59,18 @@ class InfraredCall {
 
   /// Get the carrier frequency
   const optional<uint32_t> &get_carrier_frequency() const { return this->carrier_frequency_; }
-  /// Get the raw timings (only valid if set via set_raw_timings, not packed or base85)
+  /// Get the raw timings (only valid if set via set_raw_timings)
   const std::vector<int32_t> &get_raw_timings() const { return *this->raw_timings_; }
-  /// Check if raw timings have been set (vector, packed, or base85)
+  /// Check if raw timings have been set (any format)
   bool has_raw_timings() const {
-    return this->raw_timings_ != nullptr || this->packed_data_ != nullptr || this->base85_ptr_ != nullptr;
+    return this->raw_timings_ != nullptr || this->packed_data_ != nullptr || this->base64url_ptr_ != nullptr;
   }
   /// Check if using packed data format
   bool is_packed() const { return this->packed_data_ != nullptr; }
-  /// Check if using base85 data format
-  bool is_base85() const { return this->base85_ptr_ != nullptr; }
-  /// Get the base85 data string
-  const std::string &get_base85_data() const { return *this->base85_ptr_; }
+  /// Check if using base64url data format
+  bool is_base64url() const { return this->base64url_ptr_ != nullptr; }
+  /// Get the base64url data string
+  const std::string &get_base64url_data() const { return *this->base64url_ptr_; }
   /// Get packed data (only valid if set via set_raw_timings_packed)
   const uint8_t *get_packed_data() const { return this->packed_data_; }
   uint16_t get_packed_length() const { return this->packed_length_; }
@@ -84,8 +84,8 @@ class InfraredCall {
   optional<uint32_t> carrier_frequency_;
   // Pointer to vector-based timings (caller-owned, must outlive perform())
   const std::vector<int32_t> *raw_timings_{nullptr};
-  // Pointer to base85-encoded string (caller-owned, must outlive perform())
-  const std::string *base85_ptr_{nullptr};
+  // Pointer to base64url-encoded string (caller-owned, must outlive perform())
+  const std::string *base64url_ptr_{nullptr};
   // Pointer to packed protobuf buffer (caller-owned, must outlive perform())
   const uint8_t *packed_data_{nullptr};
   uint16_t packed_length_{0};

esphome/components/light/light_json_schema.cpp

@@ -1,4 +1,5 @@
 #include "light_json_schema.h"
+#include "color_mode.h"
 #include "light_output.h"
 #include "esphome/core/progmem.h"
 
@@ -8,29 +9,32 @@ namespace esphome::light {
 
 // See https://www.home-assistant.io/integrations/light.mqtt/#json-schema for documentation on the schema
 
-// Get JSON string for color mode using linear search (avoids large switch jump table)
-static const char *get_color_mode_json_str(ColorMode mode) {
-  // Parallel arrays: mode values and their corresponding strings
-  // Uses less RAM than a switch jump table on sparse enum values
-  static constexpr ColorMode MODES[] = {
-      ColorMode::ON_OFF,
-      ColorMode::BRIGHTNESS,
-      ColorMode::WHITE,
-      ColorMode::COLOR_TEMPERATURE,
-      ColorMode::COLD_WARM_WHITE,
-      ColorMode::RGB,
-      ColorMode::RGB_WHITE,
-      ColorMode::RGB_COLOR_TEMPERATURE,
-      ColorMode::RGB_COLD_WARM_WHITE,
-  };
-  static constexpr const char *STRINGS[] = {
-      "onoff", "brightness", "white", "color_temp", "cwww", "rgb", "rgbw", "rgbct", "rgbww",
-  };
-  for (size_t i = 0; i < sizeof(MODES) / sizeof(MODES[0]); i++) {
-    if (MODES[i] == mode)
-      return STRINGS[i];
+// Get JSON string for color mode.
+// ColorMode enum values are sparse bitmasks (0, 1, 3, 7, 11, 19, 35, 39, 47, 51) which would
+// generate a large jump table. Converting to bit index (0-9) allows a compact switch.
+static ProgmemStr get_color_mode_json_str(ColorMode mode) {
+  switch (ColorModeBitPolicy::to_bit(mode)) {
+    case 1:
+      return ESPHOME_F("onoff");
+    case 2:
+      return ESPHOME_F("brightness");
+    case 3:
+      return ESPHOME_F("white");
+    case 4:
+      return ESPHOME_F("color_temp");
+    case 5:
+      return ESPHOME_F("cwww");
+    case 6:
+      return ESPHOME_F("rgb");
+    case 7:
+      return ESPHOME_F("rgbw");
+    case 8:
+      return ESPHOME_F("rgbct");
+    case 9:
+      return ESPHOME_F("rgbww");
+    default:
+      return nullptr;
   }
-  return nullptr;
 }
 
 void LightJSONSchema::dump_json(LightState &state, JsonObject root) {
@@ -44,7 +48,7 @@ void LightJSONSchema::dump_json(LightState &state, JsonObject root) {
   auto values = state.remote_values;
 
   const auto color_mode = values.get_color_mode();
-  const char *mode_str = get_color_mode_json_str(color_mode);
+  const auto *mode_str = get_color_mode_json_str(color_mode);
   if (mode_str != nullptr) {
     root[ESPHOME_F("color_mode")] = mode_str;
   }

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 snprintf(buffer, len, "%u via Max6956", this->pin_);
+  return buf_append_printf(buffer, len, 0, "%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 snprintf(buffer, len, "%u via MCP23016", this->pin_);
+  return buf_append_printf(buffer, len, 0, "%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 snprintf(buffer, len, "%u via MCP23XXX", this->pin_);
+  return buf_append_printf(buffer, len, 0, "%u via MCP23XXX", this->pin_);
 }
 
 template class MCP23XXXGPIOPin<8>;

esphome/components/modbus_controller/modbus_controller.h

@@ -271,24 +271,31 @@ 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:
-        return std::to_string(static_cast<uint64_t>(value));
+        buf_append_printf(buf, sizeof(buf), 0, "%" PRIu64, static_cast<uint64_t>(value));
+        return buf;
       case SensorValueType::S_WORD:
       case SensorValueType::S_DWORD:
       case SensorValueType::S_DWORD_R:
       case SensorValueType::S_QWORD:
       case SensorValueType::S_QWORD_R:
-        return std::to_string(value);
+        buf_append_printf(buf, sizeof(buf), 0, "%" PRId64, value);
+        return buf;
       case SensorValueType::FP32_R:
       case SensorValueType::FP32:
-        return str_sprintf("%.1f", bit_cast<float>(static_cast<uint32_t>(value)));
+        buf_append_printf(buf, sizeof(buf), 0, "%.1f", bit_cast<float>(static_cast<uint32_t>(value)));
+        return buf;
       default:
-        return std::to_string(value);
+        buf_append_printf(buf, sizeof(buf), 0, "%" PRId64, value);
+        return buf;
     }
   }
 

esphome/components/modbus_controller/text_sensor/modbus_textsensor.cpp

@@ -16,12 +16,20 @@ 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:
-        output_str += str_snprintf("%02x", 2, b);
+      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;
         break;
-      case RawEncoding::COMMA:
-        output_str += str_sprintf(index != this->offset ? ",%d" : "%d", b);
+      }
+      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;
         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 snprintf(buffer, len, "ELE%u on MPR121", this->pin_);
+  return buf_append_printf(buffer, len, 0, "ELE%u on MPR121", this->pin_);
 }
 
 }  // namespace mpr121

esphome/components/mqtt/mqtt_client.cpp

@@ -635,7 +635,8 @@ 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)) {
-    this->topic_prefix_ = str_sanitize(App.get_name());
+    char buf[ESPHOME_DEVICE_NAME_MAX_LEN + 1];
+    this->topic_prefix_ = str_sanitize_to(buf, App.get_name().c_str());
   } else {
     this->topic_prefix_ = topic_prefix;
   }

esphome/components/mqtt/mqtt_component.cpp

@@ -48,7 +48,8 @@ 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 {
-  std::string sanitized_name = str_sanitize(App.get_name());
+  char sanitized_name[ESPHOME_DEVICE_NAME_MAX_LEN + 1];
+  str_sanitize_to(sanitized_name, App.get_name().c_str());
   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);
@@ -60,7 +61,7 @@ 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.data(), sanitized_name.size());
+  p = append_str(p, sanitized_name, strlen(sanitized_name));
   p = append_char(p, '/');
   p = append_str(p, object_id.c_str(), object_id.size());
   p = append_str(p, "/config", 7);

esphome/components/network/ip_address.h

@@ -43,6 +43,14 @@ 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
@@ -52,10 +60,15 @@ 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 { return str_lower_case(inet_ntoa(ip_addr_)); }
+  std::string str() const {
+    char buf[IP_ADDRESS_BUFFER_SIZE];
+    this->str_to(buf);
+    return buf;
+  }
   /// Write IP address to buffer. Buffer must be at least IP_ADDRESS_BUFFER_SIZE bytes.
   char *str_to(char *buf) const {
-    return const_cast<char *>(inet_ntop(AF_INET, &ip_addr_, buf, IP_ADDRESS_BUFFER_SIZE));
+    inet_ntop(AF_INET, &ip_addr_, buf, IP_ADDRESS_BUFFER_SIZE);
+    return buf;  // IPv4 only, no hex letters to lowercase
   }
 #else
   IPAddress() { ip_addr_set_zero(&ip_addr_); }
@@ -134,9 +147,18 @@ 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 { return str_lower_case(ipaddr_ntoa(&ip_addr_)); }
+  std::string str() const {
+    char buf[IP_ADDRESS_BUFFER_SIZE];
+    this->str_to(buf);
+    return buf;
+  }
   /// Write IP address to buffer. Buffer must be at least IP_ADDRESS_BUFFER_SIZE bytes.
-  char *str_to(char *buf) const { return ipaddr_ntoa_r(&ip_addr_, buf, IP_ADDRESS_BUFFER_SIZE); }
+  /// 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;
+  }
   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

@@ -1,6 +1,7 @@
 #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"
 
@@ -1283,8 +1284,9 @@ 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
 
-  std::string command = "addt " + to_string(component->get_component_id()) + "," +
-                        to_string(component->get_wave_channel_id()) + "," + to_string(buffer_to_send);
+  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);
   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];
-  sprintf(range_header, "bytes=%" PRIu32 "-%" PRIu32, range_start, range_end);
+  buf_append_printf(range_header, sizeof(range_header), 0, "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];
-  sprintf(range_header, "bytes=%" PRIu32 "-%" PRIu32, range_start, range_end);
+  buf_append_printf(range_header, sizeof(range_header), 0, "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/opentherm/opentherm.cpp

@@ -561,8 +561,9 @@ const char *OpenTherm::message_id_to_str(MessageId id) {
 }
 
 void OpenTherm::debug_data(OpenthermData &data) {
-  ESP_LOGD(TAG, "%s %s %s %s", format_bin(data.type).c_str(), format_bin(data.id).c_str(),
-           format_bin(data.valueHB).c_str(), format_bin(data.valueLB).c_str());
+  char type_buf[9], id_buf[9], hb_buf[9], lb_buf[9];
+  ESP_LOGD(TAG, "%s %s %s %s", format_bin_to(type_buf, data.type), format_bin_to(id_buf, data.id),
+           format_bin_to(hb_buf, data.valueHB), format_bin_to(lb_buf, data.valueLB));
   ESP_LOGD(TAG, "type: %s; id: %u; HB: %u; LB: %u; uint_16: %u; float: %f",
            this->message_type_to_str((MessageType) data.type), data.id, data.valueHB, data.valueLB, data.u16(),
            data.f88());

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 snprintf(buffer, len, "%u via PCA6416A", this->pin_);
+  return buf_append_printf(buffer, len, 0, "%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 snprintf(buffer, len, "%u via PCA9554", this->pin_);
+  return buf_append_printf(buffer, len, 0, "%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 snprintf(buffer, len, "%u via PCF8574", this->pin_);
+  return buf_append_printf(buffer, len, 0, "%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 snprintf(buffer, len, "%u via PI4IOE5V6408", this->pin_);
+  return buf_append_printf(buffer, len, 0, "%u via PI4IOE5V6408", this->pin_);
 }
 
 }  // namespace pi4ioe5v6408

esphome/components/pipsolar/output/pipsolar_output.cpp

@@ -9,7 +9,7 @@ static const char *const TAG = "pipsolar.output";
 
 void PipsolarOutput::write_state(float state) {
   char tmp[10];
-  sprintf(tmp, this->set_command_.c_str(), state);
+  snprintf(tmp, sizeof(tmp), this->set_command_, 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

@@ -15,13 +15,15 @@ class PipsolarOutput : public output::FloatOutput {
  public:
   PipsolarOutput() {}
   void set_parent(Pipsolar *parent) { this->parent_ = parent; }
-  void set_set_command(const std::string &command) { this->set_command_ = command; };
+  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_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;
-  std::string set_command_;
+  const char *set_command_{nullptr};
   Pipsolar *parent_;
   std::vector<float> possible_values_;
 };

esphome/components/pipsolar/switch/pipsolar_switch.cpp

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

esphome/components/pipsolar/switch/pipsolar_switch.h

@@ -9,15 +9,18 @@ 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 std::string &command) { this->on_command_ = command; };
-  void set_off_command(const std::string &command) { this->off_command_ = command; };
+  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 dump_config() override;
 
  protected:
   void write_state(bool state) override;
-  std::string on_command_;
-  std::string off_command_;
+  const char *on_command_{nullptr};
+  const char *off_command_{nullptr};
   Pipsolar *parent_;
 };
 

esphome/components/rc522_spi/rc522_spi.cpp

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

esphome/components/remote_base/remote_base.cpp

@@ -2,8 +2,6 @@
 #include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 
-#include <cinttypes>
-
 namespace esphome {
 namespace remote_base {
 
@@ -160,8 +158,8 @@ void RemoteTransmitData::set_data_from_packed_sint32(const uint8_t *data, size_t
   }
 }
 
-bool RemoteTransmitData::set_data_from_base85(const std::string &base85) {
-  return base85_decode_int32_vector(base85, this->data_);
+bool RemoteTransmitData::set_data_from_base64url(const std::string &base64url) {
+  return base64_decode_int32_vector(base64url, this->data_);
 }
 
 /* RemoteTransmitterBase */

esphome/components/remote_base/remote_base.h

@@ -36,11 +36,11 @@ class RemoteTransmitData {
   /// @param len Length of the buffer in bytes
   /// @param count Number of values (for reserve optimization)
   void set_data_from_packed_sint32(const uint8_t *data, size_t len, size_t count);
-  /// Set data from base85-encoded int32 values
-  /// Decodes directly into internal buffer (zero heap allocations)
-  /// @param base85 Base85-encoded string (5 chars per int32 value)
+  /// Set data from base64url-encoded little-endian int32 values
+  /// Base64url is URL-safe: uses '-' instead of '+', '_' instead of '/'
+  /// @param base64url Base64url-encoded string of little-endian int32 values
   /// @return true if successful, false if decode failed or invalid size
-  bool set_data_from_base85(const std::string &base85);
+  bool set_data_from_base64url(const std::string &base64url);
   void reset() {
     this->data_.clear();
     this->carrier_frequency_ = 0;

esphome/components/sml/sml_parser.cpp

@@ -104,7 +104,10 @@ std::vector<ObisInfo> SmlFile::get_obis_info() {
 std::string bytes_repr(const BytesView &buffer) {
   std::string repr;
   for (auto const value : buffer) {
-    repr += str_sprintf("%02x", value & 0xff);
+    // 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;
   }
   return repr;
 }
@@ -146,7 +149,11 @@ ObisInfo::ObisInfo(const BytesView &server_id, const SmlNode &val_list_entry) :
 }
 
 std::string ObisInfo::code_repr() const {
-  return str_sprintf("%d-%d:%d.%d.%d", this->code[0], this->code[1], this->code[2], this->code[3], this->code[4]);
+  // 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;
 }
 
 }  // 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 snprintf(buffer, len, "%u via SN74HC165", this->pin_);
+  return buf_append_printf(buffer, len, 0, "%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 snprintf(buffer, len, "%u via SN74HC595", this->pin_);
+  return buf_append_printf(buffer, len, 0, "%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 std::string &ip_address, uint16_t port) {
+socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const char *ip_address, uint16_t port) {
 #if USE_NETWORK_IPV6
-  if (ip_address.find(':') != std::string::npos) {
+  if (strchr(ip_address, ':') != nullptr) {
     if (addrlen < sizeof(sockaddr_in6)) {
       errno = EINVAL;
       return 0;
@@ -121,14 +121,14 @@ socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const std::stri
 
 #ifdef USE_SOCKET_IMPL_BSD_SOCKETS
     // Use standard inet_pton for BSD sockets
-    if (inet_pton(AF_INET6, ip_address.c_str(), &server->sin6_addr) != 1) {
+    if (inet_pton(AF_INET6, ip_address, &server->sin6_addr) != 1) {
       errno = EINVAL;
       return 0;
     }
 #else
     // Use LWIP-specific functions
     ip6_addr_t ip6;
-    inet6_aton(ip_address.c_str(), &ip6);
+    inet6_aton(ip_address, &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 std::stri
   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.c_str());
+  server->sin_addr.s_addr = inet_addr(ip_address);
   server->sin_port = htons(port);
   return sizeof(sockaddr_in);
 }

esphome/components/socket/socket.h

@@ -87,7 +87,17 @@ 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().
-socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const std::string &ip_address, uint16_t port);
+/// @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);
+}
 
 /// 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.Component
+    "StatusBinarySensor", binary_sensor.BinarySensor, cg.PollingComponent
 )
 
 CONFIG_SCHEMA = binary_sensor.binary_sensor_schema(
     StatusBinarySensor,
     device_class=DEVICE_CLASS_CONNECTIVITY,
     entity_category=ENTITY_CATEGORY_DIAGNOSTIC,
-).extend(cv.COMPONENT_SCHEMA)
+).extend(cv.polling_component_schema("1s"))
 
 
 async def to_code(config):

esphome/components/status/status_binary_sensor.cpp

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

esphome/components/status/status_binary_sensor.h

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

esphome/components/sun/text_sensor/sun_text_sensor.h

@@ -14,7 +14,9 @@ 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 std::string &format) { format_ = format; }
+  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 update() override {
     optional<ESPTime> res;
@@ -29,14 +31,14 @@ class SunTextSensor : public text_sensor::TextSensor, public PollingComponent {
     }
 
     char buf[ESPTime::STRFTIME_BUFFER_SIZE];
-    size_t len = res->strftime_to(buf, this->format_.c_str());
+    size_t len = res->strftime_to(buf, this->format_);
     this->publish_state(buf, len);
   }
 
   void dump_config() override;
 
  protected:
-  std::string format_{};
+  const char *format_{nullptr};
   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 snprintf(buffer, len, "%u via sx1509", this->pin_);
+  return buf_append_printf(buffer, len, 0, "%u via sx1509", this->pin_);
 }
 
 }  // namespace sx1509

esphome/components/syslog/esphome_syslog.cpp

@@ -47,29 +47,27 @@ 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
-  int ret = snprintf(packet, remaining, "<%d>", pri);
-  if (ret <= 0 || static_cast<size_t>(ret) >= remaining) {
-    return;
+  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
   }
-  offset = ret;
-  remaining -= ret;
+  remaining -= offset;
 
   // 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
-  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);
+  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;
   }
 
   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 snprintf(buffer, len, "%u via TCA9555", this->pin_);
+  return buf_append_printf(buffer, len, 0, "%u via TCA9555", this->pin_);
 }
 
 }  // namespace tca9555

esphome/components/template/alarm_control_panel/__init__.py

@@ -118,8 +118,7 @@ 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:
-        for acode in config[CONF_CODES]:
-            cg.add(var.add_code(acode))
+        cg.add(var.set_codes(config[CONF_CODES]))
         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

@@ -206,7 +206,13 @@ 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());
-      return (std::count(this->codes_.begin(), this->codes_.end(), code.value()) == 1);
+      // 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;
     }
     ESP_LOGD(TAG, "No code provided");
     return false;

esphome/components/template/alarm_control_panel/template_alarm_control_panel.h

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

esphome/components/template/text/template_text.cpp

@@ -8,16 +8,23 @@ static const char *const TAG = "template.text";
 void TemplateText::setup() {
   if (this->f_.has_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);
+
+  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;
   }
+
+  // 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

@@ -70,13 +70,15 @@ 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 std::string &initial_value) { this->initial_value_ = initial_value; }
+  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_value_saver(TemplateTextSaverBase *restore_value_saver) { this->pref_ = restore_value_saver; }
 
  protected:
   void control(const std::string &value) override;
   bool optimistic_ = false;
-  std::string initial_value_;
+  const char *initial_value_{nullptr};
   Trigger<std::string> *set_trigger_ = new Trigger<std::string>();
   TemplateLambda<std::string> f_{};
 

esphome/components/tormatic/tormatic_protocol.h

@@ -55,6 +55,7 @@ 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:
@@ -83,7 +84,11 @@ struct MessageHeader {
   }
 
   std::string print() {
-    return str_sprintf("MessageHeader: seq %d, len %d, type %s", this->seq, this->len, message_type_to_str(this->type));
+    // 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;
   }
 
   void byteswap() {
@@ -131,6 +136,7 @@ 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:
@@ -170,7 +176,12 @@ struct StatusReply {
   GateStatus state;
   uint8_t trailer = 0x0;
 
-  std::string print() { return str_sprintf("StatusReply: state %s", gate_status_to_str(this->state)); }
+  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;
+  }
 
   void byteswap(){};
 } __attribute__((packed));
@@ -202,7 +213,12 @@ struct CommandRequestReply {
   CommandRequestReply() = default;
   CommandRequestReply(GateStatus state) { this->state = state; }
 
-  std::string print() { return str_sprintf("CommandRequestReply: state %s", gate_status_to_str(this->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;
+  }
 
   void byteswap() { this->type = convert_big_endian(this->type); }
 } __attribute__((packed));

esphome/components/toshiba/toshiba.cpp

@@ -1,5 +1,6 @@
 #include "toshiba.h"
 #include "esphome/components/remote_base/toshiba_ac_protocol.h"
+#include "esphome/core/helpers.h"
 
 #include <vector>
 
@@ -427,10 +428,17 @@ 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
-  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",
+  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,
            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";
-        sprintf(buffer, format_str, int(red * 255), int(green * 255), int(blue * 255));
+        snprintf(buffer, sizeof(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";
-        sprintf(buffer, format_str, hue, int(saturation * 1000), int(value * 1000));
+        snprintf(buffer, sizeof(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";
-        sprintf(buffer, format_str, int(red * 255), int(green * 255), int(blue * 255), hue, int(saturation * 255),
-                int(value * 255));
+        snprintf(buffer, sizeof(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
-        snprintf(buf, sizeof(buf), "%u", datapoint.value_enum);
+        buf_append_printf(buf, sizeof(buf), 0, "%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;
     }
-    sprintf(buf, "%02X", bytes[i]);
+    buf_append_printf(buf, sizeof(buf), 0, "%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) {
-      sprintf(buf, "\\x%02X", bytes[i]);
+      buf_append_printf(buf, sizeof(buf), 0, "\\x%02X", bytes[i]);
       res += buf;
     } else {
       res += bytes[i];
@@ -166,11 +166,13 @@ 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;
     }
-    res += to_string(bytes[i]);
+    buf_append_printf(buf, sizeof(buf), 0, "%u", bytes[i]);
+    res += buf;
   }
   ESP_LOGD(TAG, "%s", res.c_str());
   delay(10);
@@ -189,7 +191,7 @@ void UARTDebug::log_binary(UARTDirection direction, std::vector<uint8_t> bytes,
     if (i > 0) {
       res += separator;
     }
-    sprintf(buf, "0b" BYTE_TO_BINARY_PATTERN " (0x%02X)", BYTE_TO_BINARY(bytes[i]), bytes[i]);
+    buf_append_printf(buf, sizeof(buf), 0, "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

@@ -108,8 +108,7 @@ 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))
-    for address in config[CONF_ADDRESSES]:
-        cg.add(var.add_address(str(address)))
+    cg.add(var.set_addresses([str(addr) for addr in config[CONF_ADDRESSES]]))
     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

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

esphome/components/udp/udp_component.h

@@ -2,6 +2,7 @@
 
 #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"
@@ -9,15 +10,17 @@
 #ifdef USE_SOCKET_IMPL_LWIP_TCP
 #include <WiFiUdp.h>
 #endif
+#include <initializer_list>
 #include <vector>
 
-namespace esphome {
-namespace udp {
+namespace esphome::udp {
 
 static const size_t MAX_PACKET_SIZE = 508;
 class UDPComponent : public Component {
  public:
-  void add_address(const char *addr) { this->addresses_.emplace_back(addr); }
+  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 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; }
@@ -49,11 +52,10 @@ class UDPComponent : public Component {
   std::vector<IPAddress> ipaddrs_{};
   WiFiUDP udp_client_{};
 #endif
-  std::vector<std::string> addresses_{};
+  FixedVector<const char *> addresses_{};
 
   optional<network::IPAddress> listen_address_{};
 };
 
-}  // namespace udp
-}  // namespace esphome
+}  // namespace esphome::udp
 #endif

esphome/components/uptime/text_sensor/uptime_text_sensor.cpp

@@ -9,17 +9,12 @@ 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 += snprintf(buf + pos, buf_size - pos, "%s", separator);
-    pos = clamp_buffer_pos(pos, buf_size);
+    pos = buf_append_printf(buf, buf_size, pos, "%s", separator);
   }
-  pos += snprintf(buf + pos, buf_size - pos, "%u%s", value, label);
-  pos = clamp_buffer_pos(pos, buf_size);
+  pos = buf_append_printf(buf, buf_size, pos, "%u%s", value, label);
 }
 
 void UptimeTextSensor::setup() {

esphome/components/web_server/list_entities.cpp

@@ -143,7 +143,7 @@ bool ListEntitiesIterator::on_water_heater(water_heater::WaterHeater *obj) {
 
 #ifdef USE_INFRARED
 bool ListEntitiesIterator::on_infrared(infrared::Infrared *obj) {
-  // Infrared web_server support not yet implemented - this stub acknowledges the entity
+  this->events_->deferrable_send_state(obj, "state_detail_all", WebServer::infrared_all_json_generator);
   return true;
 }
 #endif

esphome/components/web_server/web_server.cpp

@@ -33,6 +33,10 @@
 #include "esphome/components/water_heater/water_heater.h"
 #endif
 
+#ifdef USE_INFRARED
+#include "esphome/components/infrared/infrared.h"
+#endif
+
 #ifdef USE_WEBSERVER_LOCAL
 #if USE_WEBSERVER_VERSION == 2
 #include "server_index_v2.h"
@@ -658,6 +662,24 @@ std::string WebServer::text_sensor_json_(text_sensor::TextSensor *obj, const std
 #endif
 
 #ifdef USE_SWITCH
+enum SwitchAction : uint8_t { SWITCH_ACTION_NONE, SWITCH_ACTION_TOGGLE, SWITCH_ACTION_TURN_ON, SWITCH_ACTION_TURN_OFF };
+
+static void execute_switch_action(switch_::Switch *obj, SwitchAction action) {
+  switch (action) {
+    case SWITCH_ACTION_TOGGLE:
+      obj->toggle();
+      break;
+    case SWITCH_ACTION_TURN_ON:
+      obj->turn_on();
+      break;
+    case SWITCH_ACTION_TURN_OFF:
+      obj->turn_off();
+      break;
+    default:
+      break;
+  }
+}
+
 void WebServer::on_switch_update(switch_::Switch *obj) {
   if (!this->include_internal_ && obj->is_internal())
     return;
@@ -676,34 +698,22 @@ void WebServer::handle_switch_request(AsyncWebServerRequest *request, const UrlM
       return;
     }
 
-    // Handle action methods with single defer and response
-    enum SwitchAction { NONE, TOGGLE, TURN_ON, TURN_OFF };
-    SwitchAction action = NONE;
+    SwitchAction action = SWITCH_ACTION_NONE;
 
     if (match.method_equals(ESPHOME_F("toggle"))) {
-      action = TOGGLE;
+      action = SWITCH_ACTION_TOGGLE;
     } else if (match.method_equals(ESPHOME_F("turn_on"))) {
-      action = TURN_ON;
+      action = SWITCH_ACTION_TURN_ON;
     } else if (match.method_equals(ESPHOME_F("turn_off"))) {
-      action = TURN_OFF;
+      action = SWITCH_ACTION_TURN_OFF;
     }
 
-    if (action != NONE) {
-      this->defer([obj, action]() {
-        switch (action) {
-          case TOGGLE:
-            obj->toggle();
-            break;
-          case TURN_ON:
-            obj->turn_on();
-            break;
-          case TURN_OFF:
-            obj->turn_off();
-            break;
-          default:
-            break;
-        }
-      });
+    if (action != SWITCH_ACTION_NONE) {
+#ifdef USE_ESP8266
+      execute_switch_action(obj, action);
+#else
+      this->defer([obj, action]() { execute_switch_action(obj, action); });
+#endif
       request->send(200);
     } else {
       request->send(404);
@@ -743,7 +753,7 @@ void WebServer::handle_button_request(AsyncWebServerRequest *request, const UrlM
       std::string data = this->button_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
     } else if (match.method_equals(ESPHOME_F("press"))) {
-      this->defer([obj]() { obj->press(); });
+      DEFER_ACTION(obj, obj->press());
       request->send(200);
       return;
     } else {
@@ -828,7 +838,7 @@ void WebServer::handle_fan_request(AsyncWebServerRequest *request, const UrlMatc
       std::string data = this->fan_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
     } else if (match.method_equals(ESPHOME_F("toggle"))) {
-      this->defer([obj]() { obj->toggle().perform(); });
+      DEFER_ACTION(obj, obj->toggle().perform());
       request->send(200);
     } else {
       bool is_on = match.method_equals(ESPHOME_F("turn_on"));
@@ -859,7 +869,7 @@ void WebServer::handle_fan_request(AsyncWebServerRequest *request, const UrlMatc
             return;
         }
       }
-      this->defer([call]() mutable { call.perform(); });
+      DEFER_ACTION(call, call.perform());
       request->send(200);
     }
     return;
@@ -909,7 +919,7 @@ void WebServer::handle_light_request(AsyncWebServerRequest *request, const UrlMa
       std::string data = this->light_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
     } else if (match.method_equals(ESPHOME_F("toggle"))) {
-      this->defer([obj]() { obj->toggle().perform(); });
+      DEFER_ACTION(obj, obj->toggle().perform());
       request->send(200);
     } else {
       bool is_on = match.method_equals(ESPHOME_F("turn_on"));
@@ -938,7 +948,7 @@ void WebServer::handle_light_request(AsyncWebServerRequest *request, const UrlMa
         parse_string_param_(request, ESPHOME_F("effect"), call, &decltype(call)::set_effect);
       }
 
-      this->defer([call]() mutable { call.perform(); });
+      DEFER_ACTION(call, call.perform());
       request->send(200);
     }
     return;
@@ -1027,7 +1037,7 @@ void WebServer::handle_cover_request(AsyncWebServerRequest *request, const UrlMa
     parse_float_param_(request, ESPHOME_F("position"), call, &decltype(call)::set_position);
     parse_float_param_(request, ESPHOME_F("tilt"), call, &decltype(call)::set_tilt);
 
-    this->defer([call]() mutable { call.perform(); });
+    DEFER_ACTION(call, call.perform());
     request->send(200);
     return;
   }
@@ -1086,7 +1096,7 @@ void WebServer::handle_number_request(AsyncWebServerRequest *request, const UrlM
     auto call = obj->make_call();
     parse_float_param_(request, ESPHOME_F("value"), call, &decltype(call)::set_value);
 
-    this->defer([call]() mutable { call.perform(); });
+    DEFER_ACTION(call, call.perform());
     request->send(200);
     return;
   }
@@ -1159,7 +1169,7 @@ void WebServer::handle_date_request(AsyncWebServerRequest *request, const UrlMat
 
     parse_string_param_(request, ESPHOME_F("value"), call, &decltype(call)::set_date);
 
-    this->defer([call]() mutable { call.perform(); });
+    DEFER_ACTION(call, call.perform());
     request->send(200);
     return;
   }
@@ -1178,11 +1188,7 @@ std::string WebServer::date_json_(datetime::DateEntity *obj, JsonDetail start_co
 
   // Format: YYYY-MM-DD (max 10 chars + null)
   char value[12];
-#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
+  buf_append_printf(value, sizeof(value), 0, "%d-%02d-%02d", obj->year, obj->month, obj->day);
   set_json_icon_state_value(root, obj, "date", value, value, start_config);
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
@@ -1223,7 +1229,7 @@ void WebServer::handle_time_request(AsyncWebServerRequest *request, const UrlMat
 
     parse_string_param_(request, ESPHOME_F("value"), call, &decltype(call)::set_time);
 
-    this->defer([call]() mutable { call.perform(); });
+    DEFER_ACTION(call, call.perform());
     request->send(200);
     return;
   }
@@ -1241,11 +1247,7 @@ std::string WebServer::time_json_(datetime::TimeEntity *obj, JsonDetail start_co
 
   // Format: HH:MM:SS (8 chars + null)
   char value[12];
-#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
+  buf_append_printf(value, sizeof(value), 0, "%02d:%02d:%02d", obj->hour, obj->minute, obj->second);
   set_json_icon_state_value(root, obj, "time", value, value, start_config);
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
@@ -1286,7 +1288,7 @@ void WebServer::handle_datetime_request(AsyncWebServerRequest *request, const Ur
 
     parse_string_param_(request, ESPHOME_F("value"), call, &decltype(call)::set_datetime);
 
-    this->defer([call]() mutable { call.perform(); });
+    DEFER_ACTION(call, call.perform());
     request->send(200);
     return;
   }
@@ -1304,13 +1306,8 @@ std::string WebServer::datetime_json_(datetime::DateTimeEntity *obj, JsonDetail
 
   // Format: YYYY-MM-DD HH:MM:SS (max 19 chars + null)
   char value[24];
-#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
+  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);
   set_json_icon_state_value(root, obj, "datetime", value, value, start_config);
   if (start_config == DETAIL_ALL) {
     this->add_sorting_info_(root, obj);
@@ -1346,7 +1343,7 @@ void WebServer::handle_text_request(AsyncWebServerRequest *request, const UrlMat
     auto call = obj->make_call();
     parse_string_param_(request, ESPHOME_F("value"), call, &decltype(call)::set_value);
 
-    this->defer([call]() mutable { call.perform(); });
+    DEFER_ACTION(call, call.perform());
     request->send(200);
     return;
   }
@@ -1404,7 +1401,7 @@ void WebServer::handle_select_request(AsyncWebServerRequest *request, const UrlM
     auto call = obj->make_call();
     parse_string_param_(request, ESPHOME_F("option"), call, &decltype(call)::set_option);
 
-    this->defer([call]() mutable { call.perform(); });
+    DEFER_ACTION(call, call.perform());
     request->send(200);
     return;
   }
@@ -1473,7 +1470,7 @@ void WebServer::handle_climate_request(AsyncWebServerRequest *request, const Url
     parse_float_param_(request, ESPHOME_F("target_temperature_low"), call, &decltype(call)::set_target_temperature_low);
     parse_float_param_(request, ESPHOME_F("target_temperature"), call, &decltype(call)::set_target_temperature);
 
-    this->defer([call]() mutable { call.perform(); });
+    DEFER_ACTION(call, call.perform());
     request->send(200);
     return;
   }
@@ -1589,6 +1586,24 @@ std::string WebServer::climate_json_(climate::Climate *obj, JsonDetail start_con
 #endif
 
 #ifdef USE_LOCK
+enum LockAction : uint8_t { LOCK_ACTION_NONE, LOCK_ACTION_LOCK, LOCK_ACTION_UNLOCK, LOCK_ACTION_OPEN };
+
+static void execute_lock_action(lock::Lock *obj, LockAction action) {
+  switch (action) {
+    case LOCK_ACTION_LOCK:
+      obj->lock();
+      break;
+    case LOCK_ACTION_UNLOCK:
+      obj->unlock();
+      break;
+    case LOCK_ACTION_OPEN:
+      obj->open();
+      break;
+    default:
+      break;
+  }
+}
+
 void WebServer::on_lock_update(lock::Lock *obj) {
   if (!this->include_internal_ && obj->is_internal())
     return;
@@ -1607,34 +1622,22 @@ void WebServer::handle_lock_request(AsyncWebServerRequest *request, const UrlMat
       return;
     }
 
-    // Handle action methods with single defer and response
-    enum LockAction { NONE, LOCK, UNLOCK, OPEN };
-    LockAction action = NONE;
+    LockAction action = LOCK_ACTION_NONE;
 
     if (match.method_equals(ESPHOME_F("lock"))) {
-      action = LOCK;
+      action = LOCK_ACTION_LOCK;
     } else if (match.method_equals(ESPHOME_F("unlock"))) {
-      action = UNLOCK;
+      action = LOCK_ACTION_UNLOCK;
     } else if (match.method_equals(ESPHOME_F("open"))) {
-      action = OPEN;
+      action = LOCK_ACTION_OPEN;
     }
 
-    if (action != NONE) {
-      this->defer([obj, action]() {
-        switch (action) {
-          case LOCK:
-            obj->lock();
-            break;
-          case UNLOCK:
-            obj->unlock();
-            break;
-          case OPEN:
-            obj->open();
-            break;
-          default:
-            break;
-        }
-      });
+    if (action != LOCK_ACTION_NONE) {
+#ifdef USE_ESP8266
+      execute_lock_action(obj, action);
+#else
+      this->defer([obj, action]() { execute_lock_action(obj, action); });
+#endif
       request->send(200);
     } else {
       request->send(404);
@@ -1717,7 +1720,7 @@ void WebServer::handle_valve_request(AsyncWebServerRequest *request, const UrlMa
 
     parse_float_param_(request, ESPHOME_F("position"), call, &decltype(call)::set_position);
 
-    this->defer([call]() mutable { call.perform(); });
+    DEFER_ACTION(call, call.perform());
     request->send(200);
     return;
   }
@@ -1796,7 +1799,7 @@ void WebServer::handle_alarm_control_panel_request(AsyncWebServerRequest *reques
       return;
     }
 
-    this->defer([call]() mutable { call.perform(); });
+    DEFER_ACTION(call, call.perform());
     request->send(200);
     return;
   }
@@ -1872,7 +1875,7 @@ void WebServer::handle_water_heater_request(AsyncWebServerRequest *request, cons
     // Parse on/off parameter
     parse_bool_param_(request, ESPHOME_F("is_on"), base_call, &water_heater::WaterHeaterCall::set_on);
 
-    this->defer([call]() mutable { call.perform(); });
+    DEFER_ACTION(call, call.perform());
     request->send(200);
     return;
   }
@@ -1940,6 +1943,110 @@ std::string WebServer::water_heater_json_(water_heater::WaterHeater *obj, JsonDe
 }
 #endif
 
+#ifdef USE_INFRARED
+void WebServer::handle_infrared_request(AsyncWebServerRequest *request, const UrlMatch &match) {
+  for (infrared::Infrared *obj : App.get_infrareds()) {
+    auto entity_match = match.match_entity(obj);
+    if (!entity_match.matched)
+      continue;
+
+    if (request->method() == HTTP_GET && entity_match.action_is_empty) {
+      auto detail = get_request_detail(request);
+      std::string data = this->infrared_json_(obj, detail);
+      request->send(200, ESPHOME_F("application/json"), data.c_str());
+      return;
+    }
+    if (!match.method_equals(ESPHOME_F("transmit"))) {
+      request->send(404);
+      return;
+    }
+
+    // Only allow transmit if the device supports it
+    if (!obj->has_transmitter()) {
+      request->send(400, ESPHOME_F("text/plain"), "Device does not support transmission");
+      return;
+    }
+
+    // Parse parameters
+    auto call = obj->make_call();
+
+    // Parse carrier frequency (optional)
+    if (request->hasParam(ESPHOME_F("carrier_frequency"))) {
+      auto value = parse_number<uint32_t>(request->getParam(ESPHOME_F("carrier_frequency"))->value().c_str());
+      if (value.has_value()) {
+        call.set_carrier_frequency(*value);
+      }
+    }
+
+    // Parse repeat count (optional, defaults to 1)
+    if (request->hasParam(ESPHOME_F("repeat_count"))) {
+      auto value = parse_number<uint32_t>(request->getParam(ESPHOME_F("repeat_count"))->value().c_str());
+      if (value.has_value()) {
+        call.set_repeat_count(*value);
+      }
+    }
+
+    // Parse base64url-encoded raw timings (required)
+    // Base64url is URL-safe: uses A-Za-z0-9-_ (no special characters needing escaping)
+    if (!request->hasParam(ESPHOME_F("data"))) {
+      request->send(400, ESPHOME_F("text/plain"), "Missing 'data' parameter");
+      return;
+    }
+
+    // .c_str() is required for Arduino framework where value() returns Arduino String instead of std::string
+    std::string encoded =
+        request->getParam(ESPHOME_F("data"))->value().c_str();  // NOLINT(readability-redundant-string-cstr)
+
+    // Validate base64url is not empty
+    if (encoded.empty()) {
+      request->send(400, ESPHOME_F("text/plain"), "Empty 'data' parameter");
+      return;
+    }
+
+#ifdef USE_ESP8266
+    // ESP8266 is single-threaded, call directly
+    call.set_raw_timings_base64url(encoded);
+    call.perform();
+#else
+    // Defer to main loop for thread safety. Move encoded string into lambda to ensure
+    // it outlives the call - set_raw_timings_base64url stores a pointer, so the string
+    // must remain valid until perform() completes.
+    this->defer([call, encoded = std::move(encoded)]() mutable {
+      call.set_raw_timings_base64url(encoded);
+      call.perform();
+    });
+#endif
+
+    request->send(200);
+    return;
+  }
+  request->send(404);
+}
+
+std::string WebServer::infrared_all_json_generator(WebServer *web_server, void *source) {
+  // NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
+  return web_server->infrared_json_(static_cast<infrared::Infrared *>(source), DETAIL_ALL);
+}
+
+std::string WebServer::infrared_json_(infrared::Infrared *obj, JsonDetail start_config) {
+  json::JsonBuilder builder;
+  JsonObject root = builder.root();
+
+  set_json_icon_state_value(root, obj, "infrared", "", 0, start_config);
+
+  auto traits = obj->get_traits();
+
+  root[ESPHOME_F("supports_transmitter")] = traits.get_supports_transmitter();
+  root[ESPHOME_F("supports_receiver")] = traits.get_supports_receiver();
+
+  if (start_config == DETAIL_ALL) {
+    this->add_sorting_info_(root, obj);
+  }
+
+  return builder.serialize();
+}
+#endif
+
 #ifdef USE_EVENT
 void WebServer::on_event(event::Event *obj) {
   if (!this->include_internal_ && obj->is_internal())
@@ -2032,7 +2139,7 @@ void WebServer::handle_update_request(AsyncWebServerRequest *request, const UrlM
       return;
     }
 
-    this->defer([obj]() mutable { obj->perform(); });
+    DEFER_ACTION(obj, obj->perform());
     request->send(200);
     return;
   }
@@ -2071,24 +2178,21 @@ bool WebServer::canHandle(AsyncWebServerRequest *request) const {
   const auto &url = request->url();
   const auto method = request->method();
 
-  // Static URL checks
-  static const char *const STATIC_URLS[] = {
-    "/",
+  // Static URL checks - use ESPHOME_F to keep strings in flash on ESP8266
+  if (url == ESPHOME_F("/"))
+    return true;
 #if !defined(USE_ESP32) && defined(USE_ARDUINO)
-    "/events",
+  if (url == ESPHOME_F("/events"))
+    return true;
 #endif
 #ifdef USE_WEBSERVER_CSS_INCLUDE
-    "/0.css",
+  if (url == ESPHOME_F("/0.css"))
+    return true;
 #endif
 #ifdef USE_WEBSERVER_JS_INCLUDE
-    "/0.js",
+  if (url == ESPHOME_F("/0.js"))
+    return true;
 #endif
-  };
-
-  for (const auto &static_url : STATIC_URLS) {
-    if (url == static_url)
-      return true;
-  }
 
 #ifdef USE_WEBSERVER_PRIVATE_NETWORK_ACCESS
   if (method == HTTP_OPTIONS && request->hasHeader(ESPHOME_F("Access-Control-Request-Private-Network")))
@@ -2108,90 +2212,100 @@ bool WebServer::canHandle(AsyncWebServerRequest *request) const {
   if (!is_get_or_post)
     return false;
 
-  // Use lookup tables for domain checks
-  static const char *const GET_ONLY_DOMAINS[] = {
+  // Check GET-only domains - use ESPHOME_F to keep strings in flash on ESP8266
+  if (is_get) {
 #ifdef USE_SENSOR
-      "sensor",
+    if (match.domain_equals(ESPHOME_F("sensor")))
+      return true;
 #endif
 #ifdef USE_BINARY_SENSOR
-      "binary_sensor",
+    if (match.domain_equals(ESPHOME_F("binary_sensor")))
+      return true;
 #endif
 #ifdef USE_TEXT_SENSOR
-      "text_sensor",
+    if (match.domain_equals(ESPHOME_F("text_sensor")))
+      return true;
 #endif
 #ifdef USE_EVENT
-      "event",
+    if (match.domain_equals(ESPHOME_F("event")))
+      return true;
 #endif
-  };
-
-  static const char *const GET_POST_DOMAINS[] = {
-#ifdef USE_SWITCH
-      "switch",
-#endif
-#ifdef USE_BUTTON
-      "button",
-#endif
-#ifdef USE_FAN
-      "fan",
-#endif
-#ifdef USE_LIGHT
-      "light",
-#endif
-#ifdef USE_COVER
-      "cover",
-#endif
-#ifdef USE_NUMBER
-      "number",
-#endif
-#ifdef USE_DATETIME_DATE
-      "date",
-#endif
-#ifdef USE_DATETIME_TIME
-      "time",
-#endif
-#ifdef USE_DATETIME_DATETIME
-      "datetime",
-#endif
-#ifdef USE_TEXT
-      "text",
-#endif
-#ifdef USE_SELECT
-      "select",
-#endif
-#ifdef USE_CLIMATE
-      "climate",
-#endif
-#ifdef USE_LOCK
-      "lock",
-#endif
-#ifdef USE_VALVE
-      "valve",
-#endif
-#ifdef USE_ALARM_CONTROL_PANEL
-      "alarm_control_panel",
-#endif
-#ifdef USE_UPDATE
-      "update",
-#endif
-#ifdef USE_WATER_HEATER
-      "water_heater",
-#endif
-  };
-
-  // Check GET-only domains
-  if (is_get) {
-    for (const auto &domain : GET_ONLY_DOMAINS) {
-      if (match.domain_equals(domain))
-        return true;
-    }
   }
 
   // Check GET+POST domains
   if (is_get_or_post) {
-    for (const auto &domain : GET_POST_DOMAINS) {
-      if (match.domain_equals(domain))
-        return true;
-    }
+#ifdef USE_SWITCH
+    if (match.domain_equals(ESPHOME_F("switch")))
+      return true;
+#endif
+#ifdef USE_BUTTON
+    if (match.domain_equals(ESPHOME_F("button")))
+      return true;
+#endif
+#ifdef USE_FAN
+    if (match.domain_equals(ESPHOME_F("fan")))
+      return true;
+#endif
+#ifdef USE_LIGHT
+    if (match.domain_equals(ESPHOME_F("light")))
+      return true;
+#endif
+#ifdef USE_COVER
+    if (match.domain_equals(ESPHOME_F("cover")))
+      return true;
+#endif
+#ifdef USE_NUMBER
+    if (match.domain_equals(ESPHOME_F("number")))
+      return true;
+#endif
+#ifdef USE_DATETIME_DATE
+    if (match.domain_equals(ESPHOME_F("date")))
+      return true;
+#endif
+#ifdef USE_DATETIME_TIME
+    if (match.domain_equals(ESPHOME_F("time")))
+      return true;
+#endif
+#ifdef USE_DATETIME_DATETIME
+    if (match.domain_equals(ESPHOME_F("datetime")))
+      return true;
+#endif
+#ifdef USE_TEXT
+    if (match.domain_equals(ESPHOME_F("text")))
+      return true;
+#endif
+#ifdef USE_SELECT
+    if (match.domain_equals(ESPHOME_F("select")))
+      return true;
+#endif
+#ifdef USE_CLIMATE
+    if (match.domain_equals(ESPHOME_F("climate")))
+      return true;
+#endif
+#ifdef USE_LOCK
+    if (match.domain_equals(ESPHOME_F("lock")))
+      return true;
+#endif
+#ifdef USE_VALVE
+    if (match.domain_equals(ESPHOME_F("valve")))
+      return true;
+#endif
+#ifdef USE_ALARM_CONTROL_PANEL
+    if (match.domain_equals(ESPHOME_F("alarm_control_panel")))
+      return true;
+#endif
+#ifdef USE_UPDATE
+    if (match.domain_equals(ESPHOME_F("update")))
+      return true;
+#endif
+#ifdef USE_WATER_HEATER
+    if (match.domain_equals(ESPHOME_F("water_heater")))
+      return true;
+#endif
+#ifdef USE_INFRARED
+    if (match.domain_equals(ESPHOME_F("infrared")))
+      return true;
+#endif
   }
 
   return false;
@@ -2340,6 +2454,11 @@ void WebServer::handleRequest(AsyncWebServerRequest *request) {
   else if (match.domain_equals(ESPHOME_F("water_heater"))) {
     this->handle_water_heater_request(request, match);
   }
+#endif
+#ifdef USE_INFRARED
+  else if (match.domain_equals(ESPHOME_F("infrared"))) {
+    this->handle_infrared_request(request, match);
+  }
 #endif
   else {
     // No matching handler found - send 404

esphome/components/web_server/web_server.h

@@ -42,6 +42,14 @@ using ParamNameType = const __FlashStringHelper *;
 using ParamNameType = const char *;
 #endif
 
+// ESP8266 is single-threaded, so actions can execute directly in request context.
+// Multi-core platforms need to defer to main loop thread for thread safety.
+#ifdef USE_ESP8266
+#define DEFER_ACTION(capture, action) action
+#else
+#define DEFER_ACTION(capture, action) this->defer([capture]() mutable { action; })
+#endif
+
 /// Result of matching a URL against an entity
 struct EntityMatchResult {
   bool matched;          ///< True if entity matched the URL
@@ -452,6 +460,13 @@ class WebServer : public Controller,
   static std::string water_heater_all_json_generator(WebServer *web_server, void *source);
 #endif
 
+#ifdef USE_INFRARED
+  /// Handle an infrared request under '/infrared/<id>/transmit'.
+  void handle_infrared_request(AsyncWebServerRequest *request, const UrlMatch &match);
+
+  static std::string infrared_all_json_generator(WebServer *web_server, void *source);
+#endif
+
 #ifdef USE_EVENT
   void on_event(event::Event *obj) override;
 
@@ -654,6 +669,9 @@ class WebServer : public Controller,
 #ifdef USE_WATER_HEATER
   std::string water_heater_json_(water_heater::WaterHeater *obj, JsonDetail start_config);
 #endif
+#ifdef USE_INFRARED
+  std::string infrared_json_(infrared::Infrared *obj, JsonDetail start_config);
+#endif
 #ifdef USE_UPDATE
   std::string update_json_(update::UpdateEntity *obj, JsonDetail start_config);
 #endif

esphome/components/weikai/weikai.cpp

@@ -4,19 +4,13 @@
 /// @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
@@ -170,17 +164,18 @@ 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, I2S2CS(state));
+    ESP_LOGI(TAG, "initial input data state = %02X (%s)", state, format_bin_to(bin_buf, state));
   }
   value = this->reg(WKREG_GPDAT, 0);
   if (value != state) {
-    ESP_LOGI(TAG, "Input data changed from %02X to %02X (%s)", state, value, I2S2CS(value));
+    ESP_LOGI(TAG, "Input data changed from %02X to %02X (%s)", state, value, format_bin_to(bin_buf, value));
     state = value;
   }
 }
@@ -188,6 +183,7 @@ 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
@@ -198,7 +194,7 @@ void WeikaiComponent::test_gpio_output_() {
   }
   state = ~state;
   this->reg(WKREG_GPDAT, 0) = state;
-  ESP_LOGI(TAG, "Flipping all outputs to %02X (%s)", state, I2S2CS(state));
+  ESP_LOGI(TAG, "Flipping all outputs to %02X (%s)", state, format_bin_to(bin_buf, state));
   delay(100);  // NOLINT
 }
 #endif
@@ -208,7 +204,9 @@ void WeikaiComponent::test_gpio_output_() {
 ///////////////////////////////////////////////////////////////////////////////
 bool WeikaiComponent::read_pin_val_(uint8_t pin) {
   this->input_state_ = this->reg(WKREG_GPDAT, 0);
-  ESP_LOGVV(TAG, "reading input pin %u = %u in_state %s", pin, this->input_state_ & (1 << pin), I2S2CS(input_state_));
+  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_));
   return this->input_state_ & (1 << pin);
 }
 
@@ -218,7 +216,9 @@ void WeikaiComponent::write_pin_val_(uint8_t pin, bool value) {
   } else {
     this->output_state_ &= ~(1 << pin);
   }
-  ESP_LOGVV(TAG, "writing output pin %d with %d out_state %s", pin, uint8_t(value), I2S2CS(this->output_state_));
+  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_));
   this->reg(WKREG_GPDAT, 0) = this->output_state_;
 }
 
@@ -232,7 +232,8 @@ void WeikaiComponent::set_pin_direction_(uint8_t pin, gpio::Flags flags) {
       ESP_LOGE(TAG, "pin %d direction invalid", pin);
     }
   }
-  ESP_LOGVV(TAG, "setting pin %d direction to %d pin_config=%s", pin, flags, I2S2CS(this->pin_config_));
+  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_));
   this->reg(WKREG_GPDIR, 0) = this->pin_config_;  // TODO check ~
 }
 
@@ -241,12 +242,11 @@ 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 snprintf(buffer, len, "%u via WeiKai %s", this->pin_, this->parent_->get_name());
+  return buf_append_printf(buffer, len, 0, "%u via WeiKai %s", this->pin_, this->parent_->get_name());
 }
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -297,8 +297,9 @@ 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_), I2S2CS(lcr));
+           this->stop_bits_, p2s(this->parity_), format_bin_to(bin_buf, lcr));
 }
 
 void WeikaiChannel::set_baudrate_() {
@@ -334,7 +335,8 @@ size_t WeikaiChannel::tx_in_fifo_() {
   if (tfcnt == 0) {
     uint8_t const fsr = this->reg(WKREG_FSR);
     if (fsr & FSR_TFFULL) {
-      ESP_LOGVV(TAG, "tx FIFO full FSR=%s", I2S2CS(fsr));
+      char bin_buf[9];
+      ESP_LOGVV(TAG, "tx FIFO full FSR=%s", format_bin_to(bin_buf, fsr));
       tfcnt = FIFO_SIZE;
     }
   }
@@ -346,14 +348,15 @@ 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", I2S2CS(fsr));
+      ESP_LOGE(TAG, "Receive data overflow FSR=%s", format_bin_to(bin_buf, fsr));
     if (fsr & FSR_RFLB)
-      ESP_LOGE(TAG, "Receive line break FSR=%s", I2S2CS(fsr));
+      ESP_LOGE(TAG, "Receive line break FSR=%s", format_bin_to(bin_buf, fsr));
     if (fsr & FSR_RFFE)
-      ESP_LOGE(TAG, "Receive frame error FSR=%s", I2S2CS(fsr));
+      ESP_LOGE(TAG, "Receive frame error FSR=%s", format_bin_to(bin_buf, fsr));
     if (fsr & FSR_RFPE)
-      ESP_LOGE(TAG, "Receive parity error FSR=%s", I2S2CS(fsr));
+      ESP_LOGE(TAG, "Receive parity error FSR=%s", format_bin_to(bin_buf, fsr));
   }
   if ((available == 0) && (fsr & FSR_RFDAT)) {
     // here we should be very careful because we can have something like this:
@@ -362,11 +365,13 @@ 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 ?
-      ESP_LOGV(TAG, "rx FIFO is full FSR=%s", I2S2CS(fsr));
+      char bin_buf[9];
+      ESP_LOGV(TAG, "rx FIFO is full FSR=%s", format_bin_to(bin_buf, fsr));
       available = FIFO_SIZE;
     }
   }
-  ESP_LOGVV(TAG, "rx FIFO contain %d bytes - FSR status=%s", available, I2S2CS(fsr));
+  char bin_buf2[9];
+  ESP_LOGVV(TAG, "rx FIFO contain %d bytes - FSR status=%s", available, format_bin_to(bin_buf2, fsr));
   return available;
 }
 

esphome/components/weikai/weikai.h

@@ -8,7 +8,6 @@
 ///                 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

@@ -10,13 +10,6 @@ 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
@@ -107,7 +100,8 @@ uint8_t WeikaiRegisterSPI::read_reg() const {
   spi_comp->write_byte(cmd);
   uint8_t val = spi_comp->read_byte();
   spi_comp->disable();
-  ESP_LOGVV(TAG, "WeikaiRegisterSPI::read_reg() cmd=%s(%02X) reg=%s ch=%d buf=%02X", I2S2CS(cmd), cmd,
+  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,
             reg_to_str(this->register_, this->comp_->page1()), this->channel_, val);
   return val;
 }
@@ -120,8 +114,9 @@ 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
-  ESP_LOGVV(TAG, "WeikaiRegisterSPI::read_fifo() cmd=%s(%02X) ch=%d len=%d buffer", I2S2CS(cmd), cmd, this->channel_,
-            length);
+  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);
   print_buffer(data, length);
 #endif
 }
@@ -132,8 +127,9 @@ void WeikaiRegisterSPI::write_reg(uint8_t value) {
   spi_comp->enable();
   spi_comp->write_array(buf, 2);
   spi_comp->disable();
-  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]);
+  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]);
 }
 
 void WeikaiRegisterSPI::write_fifo(uint8_t *data, size_t length) {
@@ -145,8 +141,9 @@ void WeikaiRegisterSPI::write_fifo(uint8_t *data, size_t length) {
   spi_comp->disable();
 
 #ifdef ESPHOME_LOG_HAS_VERY_VERBOSE
-  ESP_LOGVV(TAG, "WeikaiRegisterSPI::write_fifo() cmd=%s(%02X) ch=%d len=%d buffer", I2S2CS(cmd), cmd, this->channel_,
-            length);
+  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);
   print_buffer(data, length);
 #endif
 }

esphome/components/weikai_spi/weikai_spi.h

@@ -6,7 +6,6 @@
 ///          wk2124_spi, wk2132_spi, wk2168_spi, wk2204_spi, wk2212_spi,
 
 #pragma once
-#include <bitset>
 #include <memory>
 #include "esphome/core/component.h"
 #include "esphome/components/uart/uart.h"

esphome/components/wiegand/wiegand.cpp

@@ -1,4 +1,5 @@
 #include "wiegand.h"
+#include <cinttypes>
 #include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 
@@ -69,32 +70,35 @@ void Wiegand::loop() {
   for (auto *trigger : this->raw_triggers_)
     trigger->trigger(count, value);
   if (count == 26) {
-    std::string tag = to_string((value >> 1) & 0xffffff);
-    ESP_LOGD(TAG, "received 26-bit tag: %s", tag.c_str());
+    char tag_buf[12];  // max 8 digits for 24-bit value + null
+    buf_append_printf(tag_buf, sizeof(tag_buf), 0, "%" PRIu32, static_cast<uint32_t>((value >> 1) & 0xffffff));
+    ESP_LOGD(TAG, "received 26-bit tag: %s", tag_buf);
     if (!check_eparity(value, 13, 13) || !check_oparity(value, 0, 13)) {
       ESP_LOGW(TAG, "invalid parity");
       return;
     }
     for (auto *trigger : this->tag_triggers_)
-      trigger->trigger(tag);
+      trigger->trigger(tag_buf);
   } else if (count == 34) {
-    std::string tag = to_string((value >> 1) & 0xffffffff);
-    ESP_LOGD(TAG, "received 34-bit tag: %s", tag.c_str());
+    char tag_buf[12];  // max 10 digits for 32-bit value + null
+    buf_append_printf(tag_buf, sizeof(tag_buf), 0, "%" PRIu32, static_cast<uint32_t>((value >> 1) & 0xffffffff));
+    ESP_LOGD(TAG, "received 34-bit tag: %s", tag_buf);
     if (!check_eparity(value, 17, 17) || !check_oparity(value, 0, 17)) {
       ESP_LOGW(TAG, "invalid parity");
       return;
     }
     for (auto *trigger : this->tag_triggers_)
-      trigger->trigger(tag);
+      trigger->trigger(tag_buf);
   } else if (count == 37) {
-    std::string tag = to_string((value >> 1) & 0x7ffffffff);
-    ESP_LOGD(TAG, "received 37-bit tag: %s", tag.c_str());
+    char tag_buf[12];  // max 11 digits for 35-bit value + null
+    buf_append_printf(tag_buf, sizeof(tag_buf), 0, "%" PRIu64, static_cast<uint64_t>((value >> 1) & 0x7ffffffff));
+    ESP_LOGD(TAG, "received 37-bit tag: %s", tag_buf);
     if (!check_eparity(value, 18, 19) || !check_oparity(value, 0, 19)) {
       ESP_LOGW(TAG, "invalid parity");
       return;
     }
     for (auto *trigger : this->tag_triggers_)
-      trigger->trigger(tag);
+      trigger->trigger(tag_buf);
   } else if (count == 4) {
     for (auto *trigger : this->key_triggers_)
       trigger->trigger(value);

esphome/components/wireguard/__init__.py

@@ -30,6 +30,7 @@ _WG_KEY_REGEX = re.compile(r"^[A-Za-z0-9+/]{42}[AEIMQUYcgkosw480]=$")
 
 wireguard_ns = cg.esphome_ns.namespace("wireguard")
 Wireguard = wireguard_ns.class_("Wireguard", cg.Component, cg.PollingComponent)
+AllowedIP = wireguard_ns.struct("AllowedIP")
 WireguardPeerOnlineCondition = wireguard_ns.class_(
     "WireguardPeerOnlineCondition", automation.Condition
 )
@@ -108,8 +109,18 @@ async def to_code(config):
         )
     )
 
-    for ip in allowed_ips:
-        cg.add(var.add_allowed_ip(str(ip.network_address), str(ip.netmask)))
+    cg.add(
+        var.set_allowed_ips(
+            [
+                cg.StructInitializer(
+                    AllowedIP,
+                    ("ip", str(ip.network_address)),
+                    ("netmask", str(ip.netmask)),
+                )
+                for ip in allowed_ips
+            ]
+        )
+    )
 
     cg.add(var.set_srctime(await cg.get_variable(config[CONF_TIME_ID])))
 

esphome/components/wireguard/wireguard.cpp

@@ -13,8 +13,7 @@
 #include <esp_wireguard.h>
 #include <esp_wireguard_err.h>
 
-namespace esphome {
-namespace wireguard {
+namespace esphome::wireguard {
 
 static const char *const TAG = "wireguard";
 
@@ -28,16 +27,16 @@ static const char *const LOGMSG_ONLINE = "online";
 static const char *const LOGMSG_OFFLINE = "offline";
 
 void Wireguard::setup() {
-  this->wg_config_.address = this->address_.c_str();
-  this->wg_config_.private_key = this->private_key_.c_str();
-  this->wg_config_.endpoint = this->peer_endpoint_.c_str();
-  this->wg_config_.public_key = this->peer_public_key_.c_str();
+  this->wg_config_.address = this->address_;
+  this->wg_config_.private_key = this->private_key_;
+  this->wg_config_.endpoint = this->peer_endpoint_;
+  this->wg_config_.public_key = this->peer_public_key_;
   this->wg_config_.port = this->peer_port_;
-  this->wg_config_.netmask = this->netmask_.c_str();
+  this->wg_config_.netmask = this->netmask_;
   this->wg_config_.persistent_keepalive = this->keepalive_;
 
-  if (!this->preshared_key_.empty())
-    this->wg_config_.preshared_key = this->preshared_key_.c_str();
+  if (this->preshared_key_ != nullptr)
+    this->wg_config_.preshared_key = this->preshared_key_;
 
   this->publish_enabled_state();
 
@@ -131,6 +130,10 @@ void Wireguard::update() {
 }
 
 void Wireguard::dump_config() {
+  char private_key_masked[MASK_KEY_BUFFER_SIZE];
+  char preshared_key_masked[MASK_KEY_BUFFER_SIZE];
+  mask_key_to(private_key_masked, sizeof(private_key_masked), this->private_key_);
+  mask_key_to(preshared_key_masked, sizeof(preshared_key_masked), this->preshared_key_);
   // clang-format off
   ESP_LOGCONFIG(
       TAG,
@@ -142,13 +145,13 @@ void Wireguard::dump_config() {
       "  Peer Port: " LOG_SECRET("%d") "\n"
       "  Peer Public Key: " LOG_SECRET("%s") "\n"
       "  Peer Pre-shared Key: " LOG_SECRET("%s"),
-      this->address_.c_str(), this->netmask_.c_str(), mask_key(this->private_key_).c_str(),
-      this->peer_endpoint_.c_str(), this->peer_port_, this->peer_public_key_.c_str(),
-      (!this->preshared_key_.empty() ? mask_key(this->preshared_key_).c_str() : "NOT IN USE"));
+      this->address_, this->netmask_, private_key_masked,
+      this->peer_endpoint_, this->peer_port_, this->peer_public_key_,
+      (this->preshared_key_ != nullptr ? preshared_key_masked : "NOT IN USE"));
   // clang-format on
   ESP_LOGCONFIG(TAG, "  Peer Allowed IPs:");
-  for (auto &allowed_ip : this->allowed_ips_) {
-    ESP_LOGCONFIG(TAG, "    - %s/%s", std::get<0>(allowed_ip).c_str(), std::get<1>(allowed_ip).c_str());
+  for (const AllowedIP &allowed_ip : this->allowed_ips_) {
+    ESP_LOGCONFIG(TAG, "    - %s/%s", allowed_ip.ip, allowed_ip.netmask);
   }
   ESP_LOGCONFIG(TAG, "  Peer Persistent Keepalive: %d%s", this->keepalive_,
                 (this->keepalive_ > 0 ? "s" : " (DISABLED)"));
@@ -176,18 +179,6 @@ time_t Wireguard::get_latest_handshake() const {
   return result;
 }
 
-void Wireguard::set_address(const std::string &address) { this->address_ = address; }
-void Wireguard::set_netmask(const std::string &netmask) { this->netmask_ = netmask; }
-void Wireguard::set_private_key(const std::string &key) { this->private_key_ = key; }
-void Wireguard::set_peer_endpoint(const std::string &endpoint) { this->peer_endpoint_ = endpoint; }
-void Wireguard::set_peer_public_key(const std::string &key) { this->peer_public_key_ = key; }
-void Wireguard::set_peer_port(const uint16_t port) { this->peer_port_ = port; }
-void Wireguard::set_preshared_key(const std::string &key) { this->preshared_key_ = key; }
-
-void Wireguard::add_allowed_ip(const std::string &ip, const std::string &netmask) {
-  this->allowed_ips_.emplace_back(ip, netmask);
-}
-
 void Wireguard::set_keepalive(const uint16_t seconds) { this->keepalive_ = seconds; }
 void Wireguard::set_reboot_timeout(const uint32_t seconds) { this->reboot_timeout_ = seconds; }
 void Wireguard::set_srctime(time::RealTimeClock *srctime) { this->srctime_ = srctime; }
@@ -274,9 +265,8 @@ void Wireguard::start_connection_() {
 
   ESP_LOGD(TAG, "Configuring allowed IPs list");
   bool allowed_ips_ok = true;
-  for (std::tuple<std::string, std::string> ip : this->allowed_ips_) {
-    allowed_ips_ok &=
-        (esp_wireguard_add_allowed_ip(&(this->wg_ctx_), std::get<0>(ip).c_str(), std::get<1>(ip).c_str()) == ESP_OK);
+  for (const AllowedIP &ip : this->allowed_ips_) {
+    allowed_ips_ok &= (esp_wireguard_add_allowed_ip(&(this->wg_ctx_), ip.ip, ip.netmask) == ESP_OK);
   }
 
   if (allowed_ips_ok) {
@@ -299,8 +289,25 @@ void Wireguard::stop_connection_() {
   }
 }
 
-std::string mask_key(const std::string &key) { return (key.substr(0, 5) + "[...]="); }
+void mask_key_to(char *buffer, size_t len, const char *key) {
+  // Format: "XXXXX[...]=\0" = MASK_KEY_BUFFER_SIZE chars minimum
+  if (len < MASK_KEY_BUFFER_SIZE || key == nullptr) {
+    if (len > 0)
+      buffer[0] = '\0';
+    return;
+  }
+  // Copy first 5 characters of the key
+  size_t i = 0;
+  for (; i < 5 && key[i] != '\0'; ++i) {
+    buffer[i] = key[i];
+  }
+  // Append "[...]="
+  const char *suffix = "[...]=";
+  for (size_t j = 0; suffix[j] != '\0' && (i + j) < len - 1; ++j) {
+    buffer[i + j] = suffix[j];
+  }
+  buffer[i + 6] = '\0';
+}
 
-}  // namespace wireguard
-}  // namespace esphome
+}  // namespace esphome::wireguard
 #endif

esphome/components/wireguard/wireguard.h

@@ -2,10 +2,10 @@
 #include "esphome/core/defines.h"
 #ifdef USE_WIREGUARD
 #include <ctime>
-#include <vector>
-#include <tuple>
+#include <initializer_list>
 
 #include "esphome/core/component.h"
+#include "esphome/core/helpers.h"
 #include "esphome/components/time/real_time_clock.h"
 
 #ifdef USE_BINARY_SENSOR
@@ -22,8 +22,13 @@
 
 #include <esp_wireguard.h>
 
-namespace esphome {
-namespace wireguard {
+namespace esphome::wireguard {
+
+/// Allowed IP entry for WireGuard peer configuration.
+struct AllowedIP {
+  const char *ip;
+  const char *netmask;
+};
 
 /// Main Wireguard component class.
 class Wireguard : public PollingComponent {
@@ -37,15 +42,25 @@ class Wireguard : public PollingComponent {
 
   float get_setup_priority() const override { return esphome::setup_priority::BEFORE_CONNECTION; }
 
-  void set_address(const std::string &address);
-  void set_netmask(const std::string &netmask);
-  void set_private_key(const std::string &key);
-  void set_peer_endpoint(const std::string &endpoint);
-  void set_peer_public_key(const std::string &key);
-  void set_peer_port(uint16_t port);
-  void set_preshared_key(const std::string &key);
+  void set_address(const char *address) { this->address_ = address; }
+  void set_netmask(const char *netmask) { this->netmask_ = netmask; }
+  void set_private_key(const char *key) { this->private_key_ = key; }
+  void set_peer_endpoint(const char *endpoint) { this->peer_endpoint_ = endpoint; }
+  void set_peer_public_key(const char *key) { this->peer_public_key_ = key; }
+  void set_peer_port(uint16_t port) { this->peer_port_ = port; }
+  void set_preshared_key(const char *key) { this->preshared_key_ = key; }
 
-  void add_allowed_ip(const std::string &ip, const std::string &netmask);
+  /// Prevent accidental use of std::string which would dangle
+  void set_address(const std::string &address) = delete;
+  void set_netmask(const std::string &netmask) = delete;
+  void set_private_key(const std::string &key) = delete;
+  void set_peer_endpoint(const std::string &endpoint) = delete;
+  void set_peer_public_key(const std::string &key) = delete;
+  void set_preshared_key(const std::string &key) = delete;
+
+  void set_allowed_ips(std::initializer_list<AllowedIP> ips) { this->allowed_ips_ = ips; }
+  /// Prevent accidental use of std::string which would dangle
+  void set_allowed_ips(std::initializer_list<std::tuple<std::string, std::string>> ips) = delete;
 
   void set_keepalive(uint16_t seconds);
   void set_reboot_timeout(uint32_t seconds);
@@ -83,14 +98,14 @@ class Wireguard : public PollingComponent {
   time_t get_latest_handshake() const;
 
  protected:
-  std::string address_;
-  std::string netmask_;
-  std::string private_key_;
-  std::string peer_endpoint_;
-  std::string peer_public_key_;
-  std::string preshared_key_;
+  const char *address_{nullptr};
+  const char *netmask_{nullptr};
+  const char *private_key_{nullptr};
+  const char *peer_endpoint_{nullptr};
+  const char *peer_public_key_{nullptr};
+  const char *preshared_key_{nullptr};
 
-  std::vector<std::tuple<std::string, std::string>> allowed_ips_;
+  FixedVector<AllowedIP> allowed_ips_;
 
   uint16_t peer_port_;
   uint16_t keepalive_;
@@ -142,8 +157,11 @@ class Wireguard : public PollingComponent {
 void suspend_wdt();
 void resume_wdt();
 
+/// Size of buffer required for mask_key_to: 5 chars + "[...]=" + null = 12
+static constexpr size_t MASK_KEY_BUFFER_SIZE = 12;
+
 /// Strip most part of the key only for secure printing
-std::string mask_key(const std::string &key);
+void mask_key_to(char *buffer, size_t len, const char *key);
 
 /// Condition to check if remote peer is online.
 template<typename... Ts> class WireguardPeerOnlineCondition : public Condition<Ts...>, public Parented<Wireguard> {
@@ -169,6 +187,5 @@ template<typename... Ts> class WireguardDisableAction : public Action<Ts...>, pu
   void play(const Ts &...x) override { this->parent_->disable(); }
 };
 
-}  // namespace wireguard
-}  // namespace esphome
+}  // namespace esphome::wireguard
 #endif

esphome/components/xl9535/xl9535.cpp

@@ -111,7 +111,7 @@ void XL9535Component::pin_mode(uint8_t pin, gpio::Flags mode) {
 void XL9535GPIOPin::setup() { this->pin_mode(this->flags_); }
 
 size_t XL9535GPIOPin::dump_summary(char *buffer, size_t len) const {
-  return snprintf(buffer, len, "%u via XL9535", this->pin_);
+  return buf_append_printf(buffer, len, 0, "%u via XL9535", this->pin_);
 }
 
 void XL9535GPIOPin::pin_mode(gpio::Flags flags) { this->parent_->pin_mode(this->pin_, flags); }

esphome/components/zephyr/preferences.cpp

@@ -5,6 +5,8 @@
 #include "esphome/core/preferences.h"
 #include "esphome/core/log.h"
 #include <zephyr/settings/settings.h>
+#include <cinttypes>
+#include <cstring>
 
 namespace esphome {
 namespace zephyr {
@@ -13,6 +15,9 @@ static const char *const TAG = "zephyr.preferences";
 
 #define ESPHOME_SETTINGS_KEY "esphome"
 
+// Buffer size for key: "esphome/" (8) + max hex uint32 (8) + null terminator (1) = 17; use 20 for safety margin
+static constexpr size_t KEY_BUFFER_SIZE = 20;
+
 class ZephyrPreferenceBackend : public ESPPreferenceBackend {
  public:
   ZephyrPreferenceBackend(uint32_t type) { this->type_ = type; }
@@ -27,7 +32,9 @@ class ZephyrPreferenceBackend : public ESPPreferenceBackend {
 
   bool load(uint8_t *data, size_t len) override {
     if (len != this->data.size()) {
-      ESP_LOGE(TAG, "size of setting key %s changed, from: %u, to: %u", get_key().c_str(), this->data.size(), len);
+      char key_buf[KEY_BUFFER_SIZE];
+      this->format_key(key_buf, sizeof(key_buf));
+      ESP_LOGE(TAG, "size of setting key %s changed, from: %u, to: %u", key_buf, this->data.size(), len);
       return false;
     }
     std::memcpy(data, this->data.data(), len);
@@ -36,7 +43,7 @@ class ZephyrPreferenceBackend : public ESPPreferenceBackend {
   }
 
   uint32_t get_type() const { return this->type_; }
-  std::string get_key() const { return str_sprintf(ESPHOME_SETTINGS_KEY "/%" PRIx32, this->type_); }
+  void format_key(char *buf, size_t size) const { snprintf(buf, size, ESPHOME_SETTINGS_KEY "/%" PRIx32, this->type_); }
 
   std::vector<uint8_t> data;
 
@@ -85,7 +92,9 @@ class ZephyrPreferences : public ESPPreferences {
     }
     printf("type %u size %u\n", type, this->backends_.size());
     auto *pref = new ZephyrPreferenceBackend(type);  // NOLINT(cppcoreguidelines-owning-memory)
-    ESP_LOGD(TAG, "Add new setting %s.", pref->get_key().c_str());
+    char key_buf[KEY_BUFFER_SIZE];
+    pref->format_key(key_buf, sizeof(key_buf));
+    ESP_LOGD(TAG, "Add new setting %s.", key_buf);
     this->backends_.push_back(pref);
     return ESPPreferenceObject(pref);
   }
@@ -134,9 +143,10 @@ class ZephyrPreferences : public ESPPreferences {
 
   static int export_settings(int (*cb)(const char *name, const void *value, size_t val_len)) {
     for (auto *backend : static_cast<ZephyrPreferences *>(global_preferences)->backends_) {
-      auto name = backend->get_key();
-      int err = cb(name.c_str(), backend->data.data(), backend->data.size());
-      ESP_LOGD(TAG, "save in flash, name %s, len %u, err %d", name.c_str(), backend->data.size(), err);
+      char name[KEY_BUFFER_SIZE];
+      backend->format_key(name, sizeof(name));
+      int err = cb(name, backend->data.data(), backend->data.size());
+      ESP_LOGD(TAG, "save in flash, name %s, len %u, err %d", name, backend->data.size(), err);
     }
     return 0;
   }

esphome/core/helpers.cpp

@@ -174,6 +174,13 @@ bool str_endswith(const std::string &str, const std::string &end) {
   return str.rfind(end) == (str.size() - end.size());
 }
 #endif
+
+bool str_endswith_ignore_case(const char *str, size_t str_len, const char *suffix, size_t suffix_len) {
+  if (suffix_len > str_len)
+    return false;
+  return strncasecmp(str + str_len - suffix_len, suffix, suffix_len) == 0;
+}
+
 std::string str_truncate(const std::string &str, size_t length) {
   return str.length() > length ? str.substr(0, length) : str;
 }
@@ -199,11 +206,22 @@ std::string str_snake_case(const std::string &str) {
   }
   return result;
 }
-std::string str_sanitize(const std::string &str) {
-  std::string result = str;
-  for (char &c : result) {
-    c = to_sanitized_char(c);
+char *str_sanitize_to(char *buffer, size_t buffer_size, const char *str) {
+  if (buffer_size == 0) {
+    return buffer;
   }
+  size_t i = 0;
+  while (*str && i < buffer_size - 1) {
+    buffer[i++] = to_sanitized_char(*str++);
+  }
+  buffer[i] = '\0';
+  return buffer;
+}
+
+std::string str_sanitize(const std::string &str) {
+  std::string result;
+  result.resize(str.size());
+  str_sanitize_to(&result[0], str.size() + 1, str.c_str());
   return result;
 }
 std::string str_snprintf(const char *fmt, size_t len, ...) {
@@ -404,15 +422,31 @@ std::string format_hex_pretty(const std::string &data, char separator, bool show
   return format_hex_pretty_uint8(reinterpret_cast<const uint8_t *>(data.data()), data.length(), separator, show_length);
 }
 
+char *format_bin_to(char *buffer, size_t buffer_size, const uint8_t *data, size_t length) {
+  if (buffer_size == 0) {
+    return buffer;
+  }
+  // Calculate max bytes we can format: each byte needs 8 chars
+  size_t max_bytes = (buffer_size - 1) / 8;
+  if (max_bytes == 0 || length == 0) {
+    buffer[0] = '\0';
+    return buffer;
+  }
+  size_t bytes_to_format = std::min(length, max_bytes);
+
+  for (size_t byte_idx = 0; byte_idx < bytes_to_format; byte_idx++) {
+    for (size_t bit_idx = 0; bit_idx < 8; bit_idx++) {
+      buffer[byte_idx * 8 + bit_idx] = ((data[byte_idx] >> (7 - bit_idx)) & 1) + '0';
+    }
+  }
+  buffer[bytes_to_format * 8] = '\0';
+  return buffer;
+}
+
 std::string format_bin(const uint8_t *data, size_t length) {
   std::string result;
   result.resize(length * 8);
-  for (size_t byte_idx = 0; byte_idx < length; byte_idx++) {
-    for (size_t bit_idx = 0; bit_idx < 8; bit_idx++) {
-      result[byte_idx * 8 + bit_idx] = ((data[byte_idx] >> (7 - bit_idx)) & 1) + '0';
-    }
-  }
-
+  format_bin_to(&result[0], length * 8 + 1, data, length);
   return result;
 }
 
@@ -624,53 +658,44 @@ std::vector<uint8_t> base64_decode(const std::string &encoded_string) {
   return ret;
 }
 
-/// Encode int32 to 5 base85 characters + null terminator
-/// Standard ASCII85 alphabet: '!' (33) = 0 through 'u' (117) = 84
-inline void base85_encode_int32(int32_t value, std::span<char, BASE85_INT32_ENCODED_SIZE> output) {
-  uint32_t v = static_cast<uint32_t>(value);
-  // Encode least significant digit first, then reverse
-  for (int i = 4; i >= 0; i--) {
-    output[i] = static_cast<char>('!' + (v % 85));
-    v /= 85;
-  }
-  output[5] = '\0';
-}
-
-/// Decode 5 base85 characters to int32
-inline bool base85_decode_int32(const char *input, int32_t &out) {
-  uint8_t c0 = static_cast<uint8_t>(input[0] - '!');
-  uint8_t c1 = static_cast<uint8_t>(input[1] - '!');
-  uint8_t c2 = static_cast<uint8_t>(input[2] - '!');
-  uint8_t c3 = static_cast<uint8_t>(input[3] - '!');
-  uint8_t c4 = static_cast<uint8_t>(input[4] - '!');
-
-  // Each digit must be 0-84. Since uint8_t wraps, chars below '!' become > 84
-  if (c0 > 84 || c1 > 84 || c2 > 84 || c3 > 84 || c4 > 84)
-    return false;
-
-  // 85^4 = 52200625, 85^3 = 614125, 85^2 = 7225, 85^1 = 85
-  out = static_cast<int32_t>(c0 * 52200625u + c1 * 614125u + c2 * 7225u + c3 * 85u + c4);
-  return true;
-}
-
-/// Decode base85 string directly into vector (no intermediate buffer)
-bool base85_decode_int32_vector(const std::string &base85, std::vector<int32_t> &out) {
-  size_t len = base85.size();
-  if (len % 5 != 0)
-    return false;
+/// Decode base64/base64url string directly into vector of little-endian int32 values
+/// @param base64 Base64 or base64url encoded string (both +/ and -_ accepted)
+/// @param out Output vector (cleared and filled with decoded int32 values)
+/// @return true if successful, false if decode failed or invalid size
+bool base64_decode_int32_vector(const std::string &base64, std::vector<int32_t> &out) {
+  // Decode in chunks to minimize stack usage
+  constexpr size_t chunk_bytes = 48;  // 12 int32 values
+  constexpr size_t chunk_chars = 64;  // 48 * 4/3 = 64 chars
+  uint8_t chunk[chunk_bytes];
 
   out.clear();
-  const char *ptr = base85.data();
-  const char *end = ptr + len;
 
-  while (ptr < end) {
-    int32_t value;
-    if (!base85_decode_int32(ptr, value))
+  const uint8_t *input = reinterpret_cast<const uint8_t *>(base64.data());
+  size_t remaining = base64.size();
+  size_t pos = 0;
+
+  while (remaining > 0) {
+    size_t chars_to_decode = std::min(remaining, chunk_chars);
+    size_t decoded_len = base64_decode(input + pos, chars_to_decode, chunk, chunk_bytes);
+
+    if (decoded_len == 0)
       return false;
-    out.push_back(value);
-    ptr += 5;
+
+    // Parse little-endian int32 values
+    for (size_t i = 0; i + 3 < decoded_len; i += 4) {
+      int32_t timing = static_cast<int32_t>(encode_uint32(chunk[i + 3], chunk[i + 2], chunk[i + 1], chunk[i]));
+      out.push_back(timing);
+    }
+
+    // Check for incomplete int32 in last chunk
+    if (remaining <= chunk_chars && (decoded_len % 4) != 0)
+      return false;
+
+    pos += chars_to_decode;
+    remaining -= chars_to_decode;
   }
-  return true;
+
+  return !out.empty();
 }
 
 // Colors

esphome/core/helpers.h

@@ -366,6 +366,35 @@ template<typename T> class FixedVector {
   const T *end() const { return data_ + size_; }
 };
 
+/// @brief Helper class for efficient buffer allocation - uses stack for small sizes, heap for large
+/// This is useful when most operations need a small buffer but occasionally need larger ones.
+/// The stack buffer avoids heap allocation in the common case, while heap fallback handles edge cases.
+template<size_t STACK_SIZE> class SmallBufferWithHeapFallback {
+ public:
+  explicit SmallBufferWithHeapFallback(size_t size) {
+    if (size <= STACK_SIZE) {
+      this->buffer_ = this->stack_buffer_;
+    } else {
+      this->heap_buffer_ = new uint8_t[size];
+      this->buffer_ = this->heap_buffer_;
+    }
+  }
+  ~SmallBufferWithHeapFallback() { delete[] this->heap_buffer_; }
+
+  // Delete copy and move operations to prevent double-delete
+  SmallBufferWithHeapFallback(const SmallBufferWithHeapFallback &) = delete;
+  SmallBufferWithHeapFallback &operator=(const SmallBufferWithHeapFallback &) = delete;
+  SmallBufferWithHeapFallback(SmallBufferWithHeapFallback &&) = delete;
+  SmallBufferWithHeapFallback &operator=(SmallBufferWithHeapFallback &&) = delete;
+
+  uint8_t *get() { return this->buffer_; }
+
+ private:
+  uint8_t stack_buffer_[STACK_SIZE];
+  uint8_t *heap_buffer_{nullptr};
+  uint8_t *buffer_;
+};
+
 ///@}
 
 /// @name Mathematics
@@ -395,6 +424,28 @@ constexpr uint32_t FNV1_OFFSET_BASIS = 2166136261UL;
 /// FNV-1 32-bit prime
 constexpr uint32_t FNV1_PRIME = 16777619UL;
 
+/// Extend a FNV-1 hash with an integer (hashes each byte).
+template<std::integral T> constexpr uint32_t fnv1_hash_extend(uint32_t hash, T value) {
+  using UnsignedT = std::make_unsigned_t<T>;
+  UnsignedT uvalue = static_cast<UnsignedT>(value);
+  for (size_t i = 0; i < sizeof(T); i++) {
+    hash *= FNV1_PRIME;
+    hash ^= (uvalue >> (i * 8)) & 0xFF;
+  }
+  return hash;
+}
+/// Extend a FNV-1 hash with additional string data.
+constexpr uint32_t fnv1_hash_extend(uint32_t hash, const char *str) {
+  if (str) {
+    while (*str) {
+      hash *= FNV1_PRIME;
+      hash ^= *str++;
+    }
+  }
+  return hash;
+}
+inline uint32_t fnv1_hash_extend(uint32_t hash, const std::string &str) { return fnv1_hash_extend(hash, str.c_str()); }
+
 /// Extend a FNV-1a hash with additional string data.
 constexpr uint32_t fnv1a_hash_extend(uint32_t hash, const char *str) {
   if (str) {
@@ -523,6 +574,15 @@ bool str_startswith(const std::string &str, const std::string &start);
 /// Check whether a string ends with a value.
 bool str_endswith(const std::string &str, const std::string &end);
 
+/// Case-insensitive check if string ends with suffix (no heap allocation).
+bool str_endswith_ignore_case(const char *str, size_t str_len, const char *suffix, size_t suffix_len);
+inline bool str_endswith_ignore_case(const char *str, const char *suffix) {
+  return str_endswith_ignore_case(str, strlen(str), suffix, strlen(suffix));
+}
+inline bool str_endswith_ignore_case(const std::string &str, const char *suffix) {
+  return str_endswith_ignore_case(str.c_str(), str.size(), suffix, strlen(suffix));
+}
+
 /// Truncate a string to a specific length.
 /// @warning Allocates heap memory. Avoid in new code - causes heap fragmentation on long-running devices.
 std::string str_truncate(const std::string &str, size_t length);
@@ -549,7 +609,25 @@ std::string str_snake_case(const std::string &str);
 constexpr char to_sanitized_char(char c) {
   return (c == '-' || c == '_' || (c >= '0' && c <= '9') || (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')) ? c : '_';
 }
+
+/** Sanitize a string to buffer, keeping only alphanumerics, dashes, and underscores.
+ *
+ * @param buffer Output buffer to write to.
+ * @param buffer_size Size of the output buffer.
+ * @param str Input string to sanitize.
+ * @return Pointer to buffer.
+ *
+ * Buffer size needed: strlen(str) + 1.
+ */
+char *str_sanitize_to(char *buffer, size_t buffer_size, const char *str);
+
+/// Sanitize a string to buffer. Automatically deduces buffer size.
+template<size_t N> inline char *str_sanitize_to(char (&buffer)[N], const char *str) {
+  return str_sanitize_to(buffer, N, str);
+}
+
 /// Sanitizes the input string by removing all characters but alphanumerics, dashes and underscores.
+/// @warning Allocates heap memory. Use str_sanitize_to() with a stack buffer instead.
 std::string str_sanitize(const std::string &str);
 
 /// Calculate FNV-1 hash of a string while applying snake_case + sanitize transformations.
@@ -1096,9 +1174,66 @@ std::string format_hex_pretty(T val, char separator = '.', bool show_length = tr
   return format_hex_pretty(reinterpret_cast<uint8_t *>(&val), sizeof(T), separator, show_length);
 }
 
+/// Calculate buffer size needed for format_bin_to: "01234567...\0" = bytes * 8 + 1
+constexpr size_t format_bin_size(size_t byte_count) { return byte_count * 8 + 1; }
+
+/** Format byte array as binary string to buffer.
+ *
+ * Each byte is formatted as 8 binary digits (MSB first).
+ * Truncates output if data exceeds buffer capacity.
+ *
+ * @param buffer Output buffer to write to.
+ * @param buffer_size Size of the output buffer.
+ * @param data Pointer to the byte array to format.
+ * @param length Number of bytes in the array.
+ * @return Pointer to buffer.
+ *
+ * Buffer size needed: length * 8 + 1 (use format_bin_size()).
+ *
+ * Example:
+ * @code
+ * char buf[9];  // format_bin_size(1)
+ * format_bin_to(buf, sizeof(buf), data, 1);  // "10101011"
+ * @endcode
+ */
+char *format_bin_to(char *buffer, size_t buffer_size, const uint8_t *data, size_t length);
+
+/// Format byte array as binary to buffer. Automatically deduces buffer size.
+template<size_t N> inline char *format_bin_to(char (&buffer)[N], const uint8_t *data, size_t length) {
+  static_assert(N >= 9, "Buffer must hold at least one binary byte (9 chars)");
+  return format_bin_to(buffer, N, data, length);
+}
+
+/** Format an unsigned integer in binary to buffer, MSB first.
+ *
+ * @tparam N Buffer size (must be >= sizeof(T) * 8 + 1).
+ * @tparam T Unsigned integer type.
+ * @param buffer Output buffer to write to.
+ * @param val The unsigned integer value to format.
+ * @return Pointer to buffer.
+ *
+ * Example:
+ * @code
+ * char buf[9];  // format_bin_size(sizeof(uint8_t))
+ * format_bin_to(buf, uint8_t{0xAA});  // "10101010"
+ * char buf16[17];  // format_bin_size(sizeof(uint16_t))
+ * format_bin_to(buf16, uint16_t{0x1234});  // "0001001000110100"
+ * @endcode
+ */
+template<size_t N, typename T, enable_if_t<std::is_unsigned<T>::value, int> = 0>
+inline char *format_bin_to(char (&buffer)[N], T val) {
+  static_assert(N >= sizeof(T) * 8 + 1, "Buffer too small for type");
+  val = convert_big_endian(val);
+  return format_bin_to(buffer, reinterpret_cast<const uint8_t *>(&val), sizeof(T));
+}
+
 /// Format the byte array \p data of length \p len in binary.
+/// @warning Allocates heap memory. Use format_bin_to() with a stack buffer instead.
+/// Causes heap fragmentation on long-running devices.
 std::string format_bin(const uint8_t *data, size_t length);
 /// Format an unsigned integer in binary, starting with the most significant byte.
+/// @warning Allocates heap memory. Use format_bin_to() with a stack buffer instead.
+/// Causes heap fragmentation on long-running devices.
 template<typename T, enable_if_t<std::is_unsigned<T>::value, int> = 0> std::string format_bin(T val) {
   val = convert_big_endian(val);
   return format_bin(reinterpret_cast<uint8_t *>(&val), sizeof(T));
@@ -1137,13 +1272,11 @@ std::vector<uint8_t> base64_decode(const std::string &encoded_string);
 size_t base64_decode(std::string const &encoded_string, uint8_t *buf, size_t buf_len);
 size_t base64_decode(const uint8_t *encoded_data, size_t encoded_len, uint8_t *buf, size_t buf_len);
 
-/// Size of buffer needed for base85 encoded int32 (5 chars + null terminator)
-static constexpr size_t BASE85_INT32_ENCODED_SIZE = 6;
-
-void base85_encode_int32(int32_t value, std::span<char, BASE85_INT32_ENCODED_SIZE> output);
-
-bool base85_decode_int32(const char *input, int32_t &out);
-bool base85_decode_int32_vector(const std::string &base85, std::vector<int32_t> &out);
+/// Decode base64/base64url string directly into vector of little-endian int32 values
+/// @param base64 Base64 or base64url encoded string (both +/ and -_ accepted)
+/// @param out Output vector (cleared and filled with decoded int32 values)
+/// @return true if successful, false if decode failed or invalid size
+bool base64_decode_int32_vector(const std::string &base64, std::vector<int32_t> &out);
 
 ///@}
 

esphome/core/progmem.h

@@ -12,6 +12,8 @@
 #define ESPHOME_strncpy_P strncpy_P
 #define ESPHOME_strncat_P strncat_P
 #define ESPHOME_snprintf_P snprintf_P
+// Type for pointers to PROGMEM strings (for use with ESPHOME_F return values)
+using ProgmemStr = const __FlashStringHelper *;
 #else
 #define ESPHOME_F(string_literal) (string_literal)
 #define ESPHOME_PGM_P const char *
@@ -19,4 +21,6 @@
 #define ESPHOME_strncpy_P strncpy
 #define ESPHOME_strncat_P strncat
 #define ESPHOME_snprintf_P snprintf
+// Type for pointers to strings (no PROGMEM on non-ESP8266 platforms)
+using ProgmemStr = const char *;
 #endif

esphome/core/scheduler.h

@@ -403,7 +403,9 @@ class Scheduler {
       for (size_t i = 0; i < remaining; i++) {
         this->defer_queue_[i] = std::move(this->defer_queue_[this->defer_queue_front_ + i]);
       }
-      this->defer_queue_.resize(remaining);
+      // Use erase() instead of resize() to avoid instantiating _M_default_append
+      // (saves ~156 bytes flash). Erasing from the end is O(1) - no shifting needed.
+      this->defer_queue_.erase(this->defer_queue_.begin() + remaining, this->defer_queue_.end());
     }
     this->defer_queue_front_ = 0;
   }

esphome/idf_component.yml

@@ -28,8 +28,8 @@ dependencies:
     rules:
       - if: "target in [esp32s2, esp32s3, esp32p4]"
   esphome/esp-hub75:
-    version: 0.2.2
+    version: 0.3.0
     rules:
-      - if: "target in [esp32, esp32s2, esp32s3, esp32p4]"
+      - if: "target in [esp32, esp32s2, esp32s3, esp32c6, esp32p4]"
   esp32async/asynctcp:
     version: 3.4.91

script/ci-custom.py

@@ -682,11 +682,13 @@ def lint_trailing_whitespace(fname, match):
 # Heap-allocating helpers that cause fragmentation on long-running embedded devices.
 # These return std::string and should be replaced with stack-based alternatives.
 HEAP_ALLOCATING_HELPERS = {
+    "format_bin": "format_bin_to() with a stack buffer",
     "format_hex": "format_hex_to() with a stack buffer",
     "format_hex_pretty": "format_hex_pretty_to() with a stack buffer",
     "format_mac_address_pretty": "format_mac_addr_upper() with a stack buffer",
     "get_mac_address": "get_mac_address_into_buffer() with a stack buffer",
     "get_mac_address_pretty": "get_mac_address_pretty_into_buffer() with a stack buffer",
+    "str_sanitize": "str_sanitize_to() with a stack buffer",
     "str_truncate": "removal (function is unused)",
     "str_upper_case": "removal (function is unused)",
     "str_snake_case": "removal (function is unused)",
@@ -699,11 +701,13 @@ HEAP_ALLOCATING_HELPERS = {
     # get_mac_address(?!_) ensures we don't match get_mac_address_into_buffer, etc.
     # CPP_RE_EOL captures rest of line so NOLINT comments are detected
     r"[^\w]("
+    r"format_bin(?!_)|"
     r"format_hex(?!_)|"
     r"format_hex_pretty(?!_)|"
     r"format_mac_address_pretty|"
     r"get_mac_address_pretty(?!_)|"
     r"get_mac_address(?!_)|"
+    r"str_sanitize(?!_)|"
     r"str_truncate|"
     r"str_upper_case|"
     r"str_snake_case"

tests/components/alarm_control_panel/common.yaml

@@ -9,6 +9,8 @@ alarm_control_panel:
     name: Alarm Panel
     codes:
       - "1234"
+      - "5678"
+      - "0000"
     requires_code_to_arm: true
     arming_home_time: 1s
     arming_night_time: 1s
@@ -29,6 +31,7 @@ alarm_control_panel:
     name: Alarm Panel 2
     codes:
       - "1234"
+      - "9999"
     requires_code_to_arm: true
     arming_home_time: 1s
     arming_night_time: 1s

tests/components/udp/common.yaml

@@ -5,7 +5,10 @@ wifi:
 udp:
   id: my_udp
   listen_address: 239.0.60.53
-  addresses: ["239.0.60.53"]
+  addresses:
+    - "239.0.60.53"
+    - "192.168.1.255"
+    - "10.0.0.255"
   on_receive:
     - logger.log:
         format: "Received %d bytes"

tests/integration/fixtures/api_homeassistant.yaml

@@ -108,6 +108,25 @@ text_sensor:
             format: "HA Empty state updated: %s"
             args: ['x.c_str()']
 
+  # Test long attribute handling (>255 characters)
+  # HA states are limited to 255 chars, but attributes are not
+  - platform: homeassistant
+    name: "HA Long Attribute"
+    entity_id: sensor.long_data
+    attribute: long_value
+    id: ha_long_attribute
+    on_value:
+      then:
+        - logger.log:
+            format: "HA Long attribute received, length: %d"
+            args: ['x.size()']
+        # Log the first 50 and last 50 chars to verify no truncation
+        - lambda: |-
+            if (x.size() >= 100) {
+              ESP_LOGI("test", "Long attribute first 50 chars: %.50s", x.c_str());
+              ESP_LOGI("test", "Long attribute last 50 chars: %s", x.c_str() + x.size() - 50);
+            }
+
 # Number component for testing HA number control
 number:
   - platform: template

tests/integration/fixtures/udp_send_receive.yaml

@@ -0,0 +1,33 @@
+esphome:
+  name: udp-test
+
+host:
+
+api:
+  services:
+    - service: send_udp_message
+      then:
+        - udp.write:
+            id: test_udp
+            data: "HELLO_UDP_TEST"
+    - service: send_udp_bytes
+      then:
+        - udp.write:
+            id: test_udp
+            data: [0x55, 0x44, 0x50, 0x5F, 0x42, 0x59, 0x54, 0x45, 0x53]  # "UDP_BYTES"
+
+logger:
+  level: DEBUG
+
+udp:
+  - id: test_udp
+    addresses:
+      - "127.0.0.1"
+      - "127.0.0.2"
+    port:
+      listen_port: UDP_LISTEN_PORT_PLACEHOLDER
+      broadcast_port: UDP_BROADCAST_PORT_PLACEHOLDER
+    on_receive:
+      - logger.log:
+          format: "Received UDP: %d bytes"
+          args: [data.size()]

tests/integration/test_api_homeassistant.py

@@ -40,6 +40,7 @@ async def test_api_homeassistant(
     humidity_update_future = loop.create_future()
     motion_update_future = loop.create_future()
     weather_update_future = loop.create_future()
+    long_attr_future = loop.create_future()
 
     # Number future
     ha_number_future = loop.create_future()
@@ -58,6 +59,7 @@ async def test_api_homeassistant(
     humidity_update_pattern = re.compile(r"HA Humidity state updated: ([\d.]+)")
     motion_update_pattern = re.compile(r"HA Motion state changed: (ON|OFF)")
     weather_update_pattern = re.compile(r"HA Weather condition updated: (\w+)")
+    long_attr_pattern = re.compile(r"HA Long attribute received, length: (\d+)")
 
     # Number pattern
     ha_number_pattern = re.compile(r"Setting HA number to: ([\d.]+)")
@@ -143,8 +145,14 @@ async def test_api_homeassistant(
         elif not weather_update_future.done() and weather_update_pattern.search(line):
             weather_update_future.set_result(line)
 
-        # Check number pattern
-        elif not ha_number_future.done() and ha_number_pattern.search(line):
+        # Check long attribute pattern - separate if since it can come at different times
+        if not long_attr_future.done():
+            match = long_attr_pattern.search(line)
+            if match:
+                long_attr_future.set_result(int(match.group(1)))
+
+        # Check number pattern - separate if since it can come at different times
+        if not ha_number_future.done():
             match = ha_number_pattern.search(line)
             if match:
                 ha_number_future.set_result(match.group(1))
@@ -179,6 +187,14 @@ async def test_api_homeassistant(
         client.send_home_assistant_state("binary_sensor.external_motion", "", "ON")
         client.send_home_assistant_state("weather.home", "condition", "sunny")
 
+        # Send a long attribute (300 characters) to test that attributes aren't truncated
+        # HA states are limited to 255 chars, but attributes are NOT limited
+        # This tests the fix for the 256-byte buffer truncation bug
+        long_attr_value = "X" * 300  # 300 chars - enough to expose truncation bug
+        client.send_home_assistant_state(
+            "sensor.long_data", "long_value", long_attr_value
+        )
+
         # Test edge cases for zero-copy implementation safety
         # Empty entity_id should be silently ignored (no crash)
         client.send_home_assistant_state("", "", "should_be_ignored")
@@ -225,6 +241,13 @@ async def test_api_homeassistant(
             number_value = await asyncio.wait_for(ha_number_future, timeout=5.0)
             assert number_value == "42.5", f"Unexpected number value: {number_value}"
 
+            # Long attribute test - verify 300 chars weren't truncated to 255
+            long_attr_len = await asyncio.wait_for(long_attr_future, timeout=5.0)
+            assert long_attr_len == 300, (
+                f"Long attribute was truncated! Expected 300 chars, got {long_attr_len}. "
+                "This indicates the 256-byte truncation bug."
+            )
+
             # Wait for completion
             await asyncio.wait_for(tests_complete_future, timeout=5.0)