Merge branch 'dev' into json_web_server_stack

esphome/components/api/user_services.h

@@ -264,9 +264,9 @@ template<typename... Ts> class APIRespondAction : public Action<Ts...> {
       // Build and send JSON response
       json::JsonBuilder builder;
       this->json_builder_(x..., builder.root());
-      std::string json_str = builder.serialize();
+      auto json_buf = builder.serialize();
       this->parent_->send_action_response(call_id, success, StringRef(error_message),
-                                          reinterpret_cast<const uint8_t *>(json_str.data()), json_str.size());
+                                          reinterpret_cast<const uint8_t *>(json_buf.data()), json_buf.size());
       return;
     }
 #endif

esphome/components/esp32/__init__.py

@@ -739,10 +739,9 @@ CONF_DISABLE_REGI2C_IN_IRAM = "disable_regi2c_in_iram"
 CONF_DISABLE_FATFS = "disable_fatfs"
 
 # VFS requirement tracking
-# Components that need VFS features can call require_vfs_*() functions
+# Components that need VFS features can call require_vfs_select() or require_vfs_dir()
 KEY_VFS_SELECT_REQUIRED = "vfs_select_required"
 KEY_VFS_DIR_REQUIRED = "vfs_dir_required"
-KEY_VFS_TERMIOS_REQUIRED = "vfs_termios_required"
 # Feature requirement tracking - components can call require_* functions to re-enable
 # These are stored in CORE.data[KEY_ESP32] dict
 KEY_USB_SERIAL_JTAG_SECONDARY_REQUIRED = "usb_serial_jtag_secondary_required"
@@ -769,15 +768,6 @@ def require_vfs_dir() -> None:
     CORE.data[KEY_VFS_DIR_REQUIRED] = True
 
 
-def require_vfs_termios() -> None:
-    """Mark that VFS termios support is required by a component.
-
-    Call this from components that use terminal I/O functions (usb_serial_jtag_vfs_*, etc.).
-    This prevents CONFIG_VFS_SUPPORT_TERMIOS from being disabled.
-    """
-    CORE.data[KEY_VFS_TERMIOS_REQUIRED] = True
-
-
 def require_full_certificate_bundle() -> None:
     """Request the full certificate bundle instead of the common-CAs-only bundle.
 
@@ -1382,18 +1372,11 @@ async def to_code(config):
         add_idf_sdkconfig_option("CONFIG_LIBC_LOCKS_PLACE_IN_IRAM", False)
 
     # Disable VFS support for termios (terminal I/O functions)
-    # USB Serial JTAG VFS functions require termios support.
-    # Components that need it (e.g., logger when USB_SERIAL_JTAG is supported but not selected
-    # as the logger output) call require_vfs_termios().
+    # ESPHome doesn't use termios functions on ESP32 (only used in host UART driver).
     # Saves approximately 1.8KB of flash when disabled (default).
-    if CORE.data.get(KEY_VFS_TERMIOS_REQUIRED, False):
-        # Component requires VFS termios - force enable regardless of user setting
-        add_idf_sdkconfig_option("CONFIG_VFS_SUPPORT_TERMIOS", True)
-    else:
-        # No component needs it - allow user to control (default: disabled)
-        add_idf_sdkconfig_option(
-            "CONFIG_VFS_SUPPORT_TERMIOS", not advanced[CONF_DISABLE_VFS_SUPPORT_TERMIOS]
-        )
+    add_idf_sdkconfig_option(
+        "CONFIG_VFS_SUPPORT_TERMIOS", not advanced[CONF_DISABLE_VFS_SUPPORT_TERMIOS]
+    )
 
     # Disable VFS support for select() with file descriptors
     # ESPHome only uses select() with sockets via lwip_select(), which still works.

esphome/components/json/json_util.cpp

@@ -15,7 +15,7 @@ static const char *const TAG = "json";
 static SpiRamAllocator global_json_allocator;
 #endif
 
-std::string build_json(const json_build_t &f) {
+SerializationBuffer<> build_json(const json_build_t &f) {
   // NOLINTBEGIN(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
   JsonBuilder builder;
   JsonObject root = builder.root();
@@ -61,14 +61,62 @@ JsonDocument parse_json(const uint8_t *data, size_t len) {
   // NOLINTEND(clang-analyzer-cplusplus.NewDeleteLeaks)
 }
 
-std::string JsonBuilder::serialize() {
+SerializationBuffer<> JsonBuilder::serialize() {
+  // ===========================================================================================
+  // CRITICAL: NRVO (Named Return Value Optimization) - DO NOT REFACTOR WITHOUT UNDERSTANDING
+  // ===========================================================================================
+  //
+  // This function is carefully structured to enable NRVO. The compiler constructs `result`
+  // directly in the caller's stack frame, eliminating the move constructor call entirely.
+  //
+  // WITHOUT NRVO: Each return would trigger SerializationBuffer's move constructor, which
+  // must memcpy up to 768 bytes of stack buffer content. This happens on EVERY JSON
+  // serialization (sensor updates, web server responses, MQTT publishes, etc.).
+  //
+  // WITH NRVO: Zero memcpy, zero move constructor overhead. The buffer lives directly
+  // where the caller needs it.
+  //
+  // Requirements for NRVO to work:
+  //   1. Single named variable (`result`) returned from ALL paths
+  //   2. All paths must return the SAME variable (not different variables)
+  //   3. No std::move() on the return statement
+  //
+  // If you must modify this function:
+  //   - Keep a single `result` variable declared at the top
+  //   - All code paths must return `result` (not a different variable)
+  //   - Verify NRVO still works by checking the disassembly for move constructor calls
+  //   - Test: objdump -d -C firmware.elf | grep "SerializationBuffer.*SerializationBuffer"
+  //     Should show only destructor, NOT move constructor
+  //
+  // Why we avoid measureJson(): It instantiates DummyWriter templates adding ~1KB flash.
+  // Instead, try stack buffer first. 768 bytes covers 99.9% of JSON payloads (sensors ~200B,
+  // lights ~170B, climate ~700B). Only entities with 40+ options exceed this.
+  //
+  // ===========================================================================================
+  constexpr size_t buf_size = SerializationBuffer<>::BUFFER_SIZE;
+  SerializationBuffer<> result(buf_size - 1);  // Max content size (reserve 1 for null)
+
   if (doc_.overflowed()) {
     ESP_LOGE(TAG, "JSON document overflow");
-    return "{}";
+    auto *buf = result.data_writable_();
+    buf[0] = '{';
+    buf[1] = '}';
+    buf[2] = '\0';
+    result.set_size_(2);
+    return result;
   }
-  std::string output;
-  serializeJson(doc_, output);
-  return output;
+
+  size_t size = serializeJson(doc_, result.data_writable_(), buf_size);
+  if (size < buf_size) {
+    // Fits in stack buffer - update size to actual length
+    result.set_size_(size);
+    return result;
+  }
+
+  // Needs heap allocation - reallocate and serialize again with exact size
+  result.reallocate_heap_(size);
+  serializeJson(doc_, result.data_writable_(), size + 1);
+  return result;
 }
 
 }  // namespace json

esphome/components/json/json_util.h

@@ -1,5 +1,7 @@
 #pragma once
 
+#include <cstring>
+#include <string>
 #include <vector>
 
 #include "esphome/core/defines.h"
@@ -14,6 +16,108 @@
 namespace esphome {
 namespace json {
 
+/// Buffer for JSON serialization that uses stack allocation for small payloads.
+/// Template parameter STACK_SIZE specifies the stack buffer size (default 768 bytes).
+/// Supports move semantics for efficient return-by-value.
+template<size_t STACK_SIZE = 768> class SerializationBuffer {
+ public:
+  static constexpr size_t BUFFER_SIZE = STACK_SIZE;  ///< Stack buffer size for this instantiation
+
+  /// Construct with known size (typically from measureJson)
+  explicit SerializationBuffer(size_t size) : size_(size) {
+    if (size + 1 <= STACK_SIZE) {
+      buffer_ = stack_buffer_;
+    } else {
+      heap_buffer_ = new char[size + 1];
+      buffer_ = heap_buffer_;
+    }
+    buffer_[0] = '\0';
+  }
+
+  ~SerializationBuffer() { delete[] heap_buffer_; }
+
+  // Move constructor - works with same template instantiation
+  SerializationBuffer(SerializationBuffer &&other) noexcept : heap_buffer_(other.heap_buffer_), size_(other.size_) {
+    if (other.buffer_ == other.stack_buffer_) {
+      // Stack buffer - must copy content
+      std::memcpy(stack_buffer_, other.stack_buffer_, size_ + 1);
+      buffer_ = stack_buffer_;
+    } else {
+      // Heap buffer - steal ownership
+      buffer_ = heap_buffer_;
+      other.heap_buffer_ = nullptr;
+    }
+    // Leave moved-from object in valid empty state
+    other.stack_buffer_[0] = '\0';
+    other.buffer_ = other.stack_buffer_;
+    other.size_ = 0;
+  }
+
+  // Move assignment
+  SerializationBuffer &operator=(SerializationBuffer &&other) noexcept {
+    if (this != &other) {
+      delete[] heap_buffer_;
+      heap_buffer_ = other.heap_buffer_;
+      size_ = other.size_;
+      if (other.buffer_ == other.stack_buffer_) {
+        std::memcpy(stack_buffer_, other.stack_buffer_, size_ + 1);
+        buffer_ = stack_buffer_;
+      } else {
+        buffer_ = heap_buffer_;
+        other.heap_buffer_ = nullptr;
+      }
+      // Leave moved-from object in valid empty state
+      other.stack_buffer_[0] = '\0';
+      other.buffer_ = other.stack_buffer_;
+      other.size_ = 0;
+    }
+    return *this;
+  }
+
+  // Delete copy operations
+  SerializationBuffer(const SerializationBuffer &) = delete;
+  SerializationBuffer &operator=(const SerializationBuffer &) = delete;
+
+  /// Get null-terminated C string
+  const char *c_str() const { return buffer_; }
+  /// Get data pointer
+  const char *data() const { return buffer_; }
+  /// Get string length (excluding null terminator)
+  size_t size() const { return size_; }
+
+  /// Implicit conversion to std::string for backward compatibility
+  /// WARNING: This allocates a new std::string on the heap. Prefer using
+  /// c_str() or data()/size() directly when possible to avoid allocation.
+  operator std::string() const { return std::string(buffer_, size_); }  // NOLINT(google-explicit-constructor)
+
+ private:
+  friend class JsonBuilder;  ///< Allows JsonBuilder::serialize() to call private methods
+
+  /// Get writable buffer (for serialization)
+  char *data_writable_() { return buffer_; }
+  /// Set actual size after serialization (must not exceed allocated size)
+  /// Also ensures null termination for c_str() safety
+  void set_size_(size_t size) {
+    size_ = size;
+    buffer_[size] = '\0';
+  }
+
+  /// Reallocate to heap buffer with new size (for when stack buffer is too small)
+  /// This invalidates any previous buffer content. Used by JsonBuilder::serialize().
+  void reallocate_heap_(size_t size) {
+    delete[] heap_buffer_;
+    heap_buffer_ = new char[size + 1];
+    buffer_ = heap_buffer_;
+    size_ = size;
+    buffer_[0] = '\0';
+  }
+
+  char stack_buffer_[STACK_SIZE];
+  char *heap_buffer_{nullptr};
+  char *buffer_;
+  size_t size_;
+};
+
 #ifdef USE_PSRAM
 // Build an allocator for the JSON Library using the RAMAllocator class
 // This is only compiled when PSRAM is enabled
@@ -46,7 +150,8 @@ using json_parse_t = std::function<bool(JsonObject)>;
 using json_build_t = std::function<void(JsonObject)>;
 
 /// Build a JSON string with the provided json build function.
-std::string build_json(const json_build_t &f);
+/// Returns SerializationBuffer for stack-first allocation; implicitly converts to std::string.
+SerializationBuffer<> build_json(const json_build_t &f);
 
 /// Parse a JSON string and run the provided json parse function if it's valid.
 bool parse_json(const std::string &data, const json_parse_t &f);
@@ -69,7 +174,9 @@ class JsonBuilder {
     return root_;
   }
 
-  std::string serialize();
+  /// Serialize the JSON document to a SerializationBuffer (stack-first allocation)
+  /// Uses 768-byte stack buffer by default, falls back to heap for larger JSON
+  SerializationBuffer<> serialize();
 
  private:
 #ifdef USE_PSRAM

esphome/components/logger/__init__.py

@@ -16,8 +16,6 @@ from esphome.components.esp32 import (
     VARIANT_ESP32S3,
     add_idf_sdkconfig_option,
     get_esp32_variant,
-    require_usb_serial_jtag_secondary,
-    require_vfs_termios,
 )
 from esphome.components.libretiny import get_libretiny_component, get_libretiny_family
 from esphome.components.libretiny.const import (
@@ -399,15 +397,9 @@ async def to_code(config):
         elif config[CONF_HARDWARE_UART] == USB_SERIAL_JTAG:
             add_idf_sdkconfig_option("CONFIG_ESP_CONSOLE_USB_SERIAL_JTAG", True)
             cg.add_define("USE_LOGGER_UART_SELECTION_USB_SERIAL_JTAG")
-    # Define platform support flags for components that need auto-detection
     try:
         uart_selection(USB_SERIAL_JTAG)
         cg.add_define("USE_LOGGER_USB_SERIAL_JTAG")
-        # USB Serial JTAG code is compiled when platform supports it.
-        # Enable secondary USB serial JTAG console so the VFS functions are available.
-        if CORE.is_esp32 and config[CONF_HARDWARE_UART] != USB_SERIAL_JTAG:
-            require_usb_serial_jtag_secondary()
-            require_vfs_termios()
     except cv.Invalid:
         pass
     try:

esphome/components/mqtt/mqtt_client.cpp

@@ -564,8 +564,8 @@ bool MQTTClientComponent::publish(const char *topic, const char *payload, size_t
 }
 
 bool MQTTClientComponent::publish_json(const char *topic, const json::json_build_t &f, uint8_t qos, bool retain) {
-  std::string message = json::build_json(f);
-  return this->publish(topic, message.c_str(), message.length(), qos, retain);
+  auto message = json::build_json(f);
+  return this->publish(topic, message.c_str(), message.size(), qos, retain);
 }
 
 void MQTTClientComponent::enable() {

esphome/components/pmsx003/pmsx003.cpp

@@ -2,20 +2,21 @@
 #include "esphome/core/log.h"
 #include "esphome/core/application.h"
 
-namespace esphome::pmsx003 {
+namespace esphome {
+namespace pmsx003 {
 
 static const char *const TAG = "pmsx003";
 
 static const uint8_t START_CHARACTER_1 = 0x42;
 static const uint8_t START_CHARACTER_2 = 0x4D;
 
-static const uint16_t STABILISING_MS = 30000;  // time taken for the sensor to become stable after power on in ms
+static const uint16_t PMS_STABILISING_MS = 30000;  // time taken for the sensor to become stable after power on in ms
 
-static const uint16_t CMD_MEASUREMENT_MODE_PASSIVE =
-    0x0000;  // use `Command::MANUAL_MEASUREMENT` to trigger a measurement
-static const uint16_t CMD_MEASUREMENT_MODE_ACTIVE = 0x0001;  // automatically perform measurements
-static const uint16_t CMD_SLEEP_MODE_SLEEP = 0x0000;         // go to sleep mode
-static const uint16_t CMD_SLEEP_MODE_WAKEUP = 0x0001;        // wake up from sleep mode
+static const uint16_t PMS_CMD_MEASUREMENT_MODE_PASSIVE =
+    0x0000;  // use `PMS_CMD_MANUAL_MEASUREMENT` to trigger a measurement
+static const uint16_t PMS_CMD_MEASUREMENT_MODE_ACTIVE = 0x0001;  // automatically perform measurements
+static const uint16_t PMS_CMD_SLEEP_MODE_SLEEP = 0x0000;         // go to sleep mode
+static const uint16_t PMS_CMD_SLEEP_MODE_WAKEUP = 0x0001;        // wake up from sleep mode
 
 void PMSX003Component::setup() {}
 
@@ -41,7 +42,7 @@ void PMSX003Component::dump_config() {
   LOG_SENSOR("  ", "Temperature", this->temperature_sensor_);
   LOG_SENSOR("  ", "Humidity", this->humidity_sensor_);
 
-  if (this->update_interval_ <= STABILISING_MS) {
+  if (this->update_interval_ <= PMS_STABILISING_MS) {
     ESP_LOGCONFIG(TAG, "  Mode: active continuous (sensor default)");
   } else {
     ESP_LOGCONFIG(TAG, "  Mode: passive with sleep/wake cycles");
@@ -54,44 +55,44 @@ void PMSX003Component::loop() {
   const uint32_t now = App.get_loop_component_start_time();
 
   // Initialize sensor mode on first loop
-  if (!this->initialised_) {
-    if (this->update_interval_ > STABILISING_MS) {
+  if (this->initialised_ == 0) {
+    if (this->update_interval_ > PMS_STABILISING_MS) {
       // Long update interval: use passive mode with sleep/wake cycles
-      this->send_command_(Command::MEASUREMENT_MODE, CMD_MEASUREMENT_MODE_PASSIVE);
-      this->send_command_(Command::SLEEP_MODE, CMD_SLEEP_MODE_WAKEUP);
+      this->send_command_(PMS_CMD_MEASUREMENT_MODE, PMS_CMD_MEASUREMENT_MODE_PASSIVE);
+      this->send_command_(PMS_CMD_SLEEP_MODE, PMS_CMD_SLEEP_MODE_WAKEUP);
     } else {
       // Short/zero update interval: use active continuous mode
-      this->send_command_(Command::MEASUREMENT_MODE, CMD_MEASUREMENT_MODE_ACTIVE);
+      this->send_command_(PMS_CMD_MEASUREMENT_MODE, PMS_CMD_MEASUREMENT_MODE_ACTIVE);
     }
-    this->initialised_ = true;
+    this->initialised_ = 1;
   }
 
   // If we update less often than it takes the device to stabilise, spin the fan down
   // rather than running it constantly. It does take some time to stabilise, so we
   // need to keep track of what state we're in.
-  if (this->update_interval_ > STABILISING_MS) {
+  if (this->update_interval_ > PMS_STABILISING_MS) {
     switch (this->state_) {
-      case State::IDLE:
+      case PMSX003_STATE_IDLE:
         // Power on the sensor now so it'll be ready when we hit the update time
-        if (now - this->last_update_ < (this->update_interval_ - STABILISING_MS))
+        if (now - this->last_update_ < (this->update_interval_ - PMS_STABILISING_MS))
           return;
 
-        this->state_ = State::STABILISING;
-        this->send_command_(Command::SLEEP_MODE, CMD_SLEEP_MODE_WAKEUP);
+        this->state_ = PMSX003_STATE_STABILISING;
+        this->send_command_(PMS_CMD_SLEEP_MODE, PMS_CMD_SLEEP_MODE_WAKEUP);
         this->fan_on_time_ = now;
         return;
-      case State::STABILISING:
+      case PMSX003_STATE_STABILISING:
         // wait for the sensor to be stable
-        if (now - this->fan_on_time_ < STABILISING_MS)
+        if (now - this->fan_on_time_ < PMS_STABILISING_MS)
           return;
         // consume any command responses that are in the serial buffer
         while (this->available())
           this->read_byte(&this->data_[0]);
         // Trigger a new read
-        this->send_command_(Command::MANUAL_MEASUREMENT, 0);
-        this->state_ = State::WAITING;
+        this->send_command_(PMS_CMD_MANUAL_MEASUREMENT, 0);
+        this->state_ = PMSX003_STATE_WAITING;
         break;
-      case State::WAITING:
+      case PMSX003_STATE_WAITING:
         // Just go ahead and read stuff
         break;
     }
@@ -179,28 +180,27 @@ optional<bool> PMSX003Component::check_byte_() {
 }
 
 bool PMSX003Component::check_payload_length_(uint16_t payload_length) {
-  // https://avaldebe.github.io/PyPMS/sensors/Plantower/
   switch (this->type_) {
-    case Type::PMSX003:
+    case PMSX003_TYPE_X003:
       // The expected payload length is typically 28 bytes.
       // However, a 20-byte payload check was already present in the code.
       // No official documentation was found confirming this.
       // Retaining this check to avoid breaking existing behavior.
       return payload_length == 28 || payload_length == 20;  // 2*13+2
-    case Type::PMS5003S:
-    case Type::PMS5003T:
+    case PMSX003_TYPE_5003T:
+    case PMSX003_TYPE_5003S:
       return payload_length == 28;  // 2*13+2 (Data 13 not set/reserved)
-    case Type::PMS5003ST:
+    case PMSX003_TYPE_5003ST:
       return payload_length == 36;  // 2*17+2 (Data 16 not set/reserved)
   }
   return false;
 }
 
-void PMSX003Component::send_command_(Command cmd, uint16_t data) {
+void PMSX003Component::send_command_(PMSX0003Command cmd, uint16_t data) {
   uint8_t send_data[7] = {
       START_CHARACTER_1,            // Start Byte 1
       START_CHARACTER_2,            // Start Byte 2
-      static_cast<uint8_t>(cmd),    // Command
+      cmd,                          // Command
       uint8_t((data >> 8) & 0xFF),  // Data 1
       uint8_t((data >> 0) & 0xFF),  // Data 2
       0,                            // Verify Byte 1
@@ -265,7 +265,7 @@ void PMSX003Component::parse_data_() {
   if (this->pm_particles_25um_sensor_ != nullptr)
     this->pm_particles_25um_sensor_->publish_state(pm_particles_25um);
 
-  if (this->type_ == Type::PMS5003T) {
+  if (this->type_ == PMSX003_TYPE_5003T) {
     ESP_LOGD(TAG,
              "Got PM0.3 Particles: %u Count/0.1L, PM0.5 Particles: %u Count/0.1L, PM1.0 Particles: %u Count/0.1L, "
              "PM2.5 Particles %u Count/0.1L",
@@ -289,7 +289,7 @@ void PMSX003Component::parse_data_() {
   }
 
   // Formaldehyde
-  if (this->type_ == Type::PMS5003S || this->type_ == Type::PMS5003ST) {
+  if (this->type_ == PMSX003_TYPE_5003ST || this->type_ == PMSX003_TYPE_5003S) {
     const uint16_t formaldehyde = this->get_16_bit_uint_(28);
 
     ESP_LOGD(TAG, "Got Formaldehyde: %u µg/m^3", formaldehyde);
@@ -299,8 +299,8 @@ void PMSX003Component::parse_data_() {
   }
 
   // Temperature and Humidity
-  if (this->type_ == Type::PMS5003T || this->type_ == Type::PMS5003ST) {
-    const uint8_t temperature_offset = (this->type_ == Type::PMS5003T) ? 24 : 30;
+  if (this->type_ == PMSX003_TYPE_5003ST || this->type_ == PMSX003_TYPE_5003T) {
+    const uint8_t temperature_offset = (this->type_ == PMSX003_TYPE_5003T) ? 24 : 30;
 
     const float temperature = static_cast<int16_t>(this->get_16_bit_uint_(temperature_offset)) / 10.0f;
     const float humidity = this->get_16_bit_uint_(temperature_offset + 2) / 10.0f;
@@ -314,7 +314,7 @@ void PMSX003Component::parse_data_() {
   }
 
   // Firmware Version and Error Code
-  if (this->type_ == Type::PMS5003ST) {
+  if (this->type_ == PMSX003_TYPE_5003ST) {
     const uint8_t firmware_version = this->data_[36];
     const uint8_t error_code = this->data_[37];
 
@@ -323,12 +323,13 @@ void PMSX003Component::parse_data_() {
 
   // Spin down the sensor again if we aren't going to need it until more time has
   // passed than it takes to stabilise
-  if (this->update_interval_ > STABILISING_MS) {
-    this->send_command_(Command::SLEEP_MODE, CMD_SLEEP_MODE_SLEEP);
-    this->state_ = State::IDLE;
+  if (this->update_interval_ > PMS_STABILISING_MS) {
+    this->send_command_(PMS_CMD_SLEEP_MODE, PMS_CMD_SLEEP_MODE_SLEEP);
+    this->state_ = PMSX003_STATE_IDLE;
   }
 
   this->status_clear_warning();
 }
 
-}  // namespace esphome::pmsx003
+}  // namespace pmsx003
+}  // namespace esphome

esphome/components/pmsx003/pmsx003.h

@@ -5,25 +5,27 @@
 #include "esphome/components/sensor/sensor.h"
 #include "esphome/components/uart/uart.h"
 
-namespace esphome::pmsx003 {
+namespace esphome {
+namespace pmsx003 {
 
-enum class Type : uint8_t {
-  PMSX003 = 0,
-  PMS5003S,
-  PMS5003T,
-  PMS5003ST,
+enum PMSX0003Command : uint8_t {
+  PMS_CMD_MEASUREMENT_MODE =
+      0xE1,  // Data Options: `PMS_CMD_MEASUREMENT_MODE_PASSIVE`, `PMS_CMD_MEASUREMENT_MODE_ACTIVE`
+  PMS_CMD_MANUAL_MEASUREMENT = 0xE2,
+  PMS_CMD_SLEEP_MODE = 0xE4,  // Data Options: `PMS_CMD_SLEEP_MODE_SLEEP`, `PMS_CMD_SLEEP_MODE_WAKEUP`
 };
 
-enum class Command : uint8_t {
-  MEASUREMENT_MODE = 0xE1,  // Data Options: `CMD_MEASUREMENT_MODE_PASSIVE`, `CMD_MEASUREMENT_MODE_ACTIVE`
-  MANUAL_MEASUREMENT = 0xE2,
-  SLEEP_MODE = 0xE4,  // Data Options: `CMD_SLEEP_MODE_SLEEP`, `CMD_SLEEP_MODE_WAKEUP`
+enum PMSX003Type {
+  PMSX003_TYPE_X003 = 0,
+  PMSX003_TYPE_5003T,
+  PMSX003_TYPE_5003ST,
+  PMSX003_TYPE_5003S,
 };
 
-enum class State : uint8_t {
-  IDLE = 0,
-  STABILISING,
-  WAITING,
+enum PMSX003State {
+  PMSX003_STATE_IDLE = 0,
+  PMSX003_STATE_STABILISING,
+  PMSX003_STATE_WAITING,
 };
 
 class PMSX003Component : public uart::UARTDevice, public Component {
@@ -35,7 +37,7 @@ class PMSX003Component : public uart::UARTDevice, public Component {
 
   void set_update_interval(uint32_t update_interval) { this->update_interval_ = update_interval; }
 
-  void set_type(Type type) { this->type_ = type; }
+  void set_type(PMSX003Type type) { this->type_ = type; }
 
   void set_pm_1_0_std_sensor(sensor::Sensor *pm_1_0_std_sensor) { this->pm_1_0_std_sensor_ = pm_1_0_std_sensor; }
   void set_pm_2_5_std_sensor(sensor::Sensor *pm_2_5_std_sensor) { this->pm_2_5_std_sensor_ = pm_2_5_std_sensor; }
@@ -75,20 +77,20 @@ class PMSX003Component : public uart::UARTDevice, public Component {
   optional<bool> check_byte_();
   void parse_data_();
   bool check_payload_length_(uint16_t payload_length);
-  void send_command_(Command cmd, uint16_t data);
+  void send_command_(PMSX0003Command cmd, uint16_t data);
   uint16_t get_16_bit_uint_(uint8_t start_index) const {
     return encode_uint16(this->data_[start_index], this->data_[start_index + 1]);
   }
 
-  Type type_;
-  State state_{State::IDLE};
-  bool initialised_{false};
   uint8_t data_[64];
   uint8_t data_index_{0};
+  uint8_t initialised_{0};
   uint32_t fan_on_time_{0};
   uint32_t last_update_{0};
   uint32_t last_transmission_{0};
   uint32_t update_interval_{0};
+  PMSX003State state_{PMSX003_STATE_IDLE};
+  PMSX003Type type_;
 
   // "Standard Particle"
   sensor::Sensor *pm_1_0_std_sensor_{nullptr};
@@ -116,4 +118,5 @@ class PMSX003Component : public uart::UARTDevice, public Component {
   sensor::Sensor *humidity_sensor_{nullptr};
 };
 
-}  // namespace esphome::pmsx003
+}  // namespace pmsx003
+}  // namespace esphome

esphome/components/pmsx003/sensor.py

@@ -41,33 +41,33 @@ PMSX003Component = pmsx003_ns.class_("PMSX003Component", uart.UARTDevice, cg.Com
 PMSX003Sensor = pmsx003_ns.class_("PMSX003Sensor", sensor.Sensor)
 
 TYPE_PMSX003 = "PMSX003"
-TYPE_PMS5003S = "PMS5003S"
 TYPE_PMS5003T = "PMS5003T"
 TYPE_PMS5003ST = "PMS5003ST"
+TYPE_PMS5003S = "PMS5003S"
 
-Type = pmsx003_ns.enum("Type", is_class=True)
+PMSX003Type = pmsx003_ns.enum("PMSX003Type")
 
 PMSX003_TYPES = {
-    TYPE_PMSX003: Type.PMSX003,
-    TYPE_PMS5003S: Type.PMS5003S,
-    TYPE_PMS5003T: Type.PMS5003T,
-    TYPE_PMS5003ST: Type.PMS5003ST,
+    TYPE_PMSX003: PMSX003Type.PMSX003_TYPE_X003,
+    TYPE_PMS5003T: PMSX003Type.PMSX003_TYPE_5003T,
+    TYPE_PMS5003ST: PMSX003Type.PMSX003_TYPE_5003ST,
+    TYPE_PMS5003S: PMSX003Type.PMSX003_TYPE_5003S,
 }
 
 SENSORS_TO_TYPE = {
-    CONF_PM_1_0_STD: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
-    CONF_PM_2_5_STD: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
-    CONF_PM_10_0_STD: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
-    CONF_PM_1_0: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
-    CONF_PM_2_5: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
-    CONF_PM_10_0: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
-    CONF_PM_0_3UM: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
-    CONF_PM_0_5UM: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
-    CONF_PM_1_0UM: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
-    CONF_PM_2_5UM: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
-    CONF_PM_5_0UM: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003ST],
-    CONF_PM_10_0UM: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003ST],
-    CONF_FORMALDEHYDE: [TYPE_PMS5003S, TYPE_PMS5003ST],
+    CONF_PM_1_0: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
+    CONF_PM_2_5: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
+    CONF_PM_10_0: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
+    CONF_PM_1_0_STD: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
+    CONF_PM_2_5_STD: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
+    CONF_PM_10_0_STD: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
+    CONF_PM_0_3UM: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
+    CONF_PM_0_5UM: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
+    CONF_PM_1_0UM: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
+    CONF_PM_2_5UM: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
+    CONF_PM_5_0UM: [TYPE_PMSX003, TYPE_PMS5003ST, TYPE_PMS5003S],
+    CONF_PM_10_0UM: [TYPE_PMSX003, TYPE_PMS5003ST, TYPE_PMS5003S],
+    CONF_FORMALDEHYDE: [TYPE_PMS5003ST, TYPE_PMS5003S],
     CONF_TEMPERATURE: [TYPE_PMS5003T, TYPE_PMS5003ST],
     CONF_HUMIDITY: [TYPE_PMS5003T, TYPE_PMS5003ST],
 }

esphome/components/time/posix_tz.cpp

@@ -1,481 +0,0 @@
-#include "esphome/core/defines.h"
-
-#ifdef USE_TIME_TIMEZONE
-
-#include "posix_tz.h"
-#include <cctype>
-
-namespace esphome::time {
-
-// Global timezone - set once at startup, rarely changes
-// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables) - intentional mutable state
-static ParsedTimezone global_tz_{};
-
-void set_global_tz(const ParsedTimezone &tz) { global_tz_ = tz; }
-
-const ParsedTimezone &get_global_tz() { return global_tz_; }
-
-namespace internal {
-
-// Helper to parse an unsigned integer from string, updating pointer
-static uint32_t parse_uint(const char *&p) {
-  uint32_t value = 0;
-  while (std::isdigit(static_cast<unsigned char>(*p))) {
-    value = value * 10 + (*p - '0');
-    p++;
-  }
-  return value;
-}
-
-bool is_leap_year(int year) { return (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0); }
-
-// Get days in year (avoids duplicate is_leap_year calls)
-static inline int days_in_year(int year) { return is_leap_year(year) ? 366 : 365; }
-
-// Convert days since epoch to year, updating days to remainder
-static int __attribute__((noinline)) days_to_year(int64_t &days) {
-  int year = 1970;
-  int diy;
-  while (days >= (diy = days_in_year(year))) {
-    days -= diy;
-    year++;
-  }
-  while (days < 0) {
-    year--;
-    days += days_in_year(year);
-  }
-  return year;
-}
-
-// Extract just the year from a UTC epoch
-static int epoch_to_year(time_t epoch) {
-  int64_t days = epoch / 86400;
-  if (epoch < 0 && epoch % 86400 != 0)
-    days--;
-  return days_to_year(days);
-}
-
-int days_in_month(int year, int month) {
-  switch (month) {
-    case 2:
-      return is_leap_year(year) ? 29 : 28;
-    case 4:
-    case 6:
-    case 9:
-    case 11:
-      return 30;
-    default:
-      return 31;
-  }
-}
-
-// Zeller-like algorithm for day of week (0 = Sunday)
-int __attribute__((noinline)) day_of_week(int year, int month, int day) {
-  // Adjust for January/February
-  if (month < 3) {
-    month += 12;
-    year--;
-  }
-  int k = year % 100;
-  int j = year / 100;
-  int h = (day + (13 * (month + 1)) / 5 + k + k / 4 + j / 4 - 2 * j) % 7;
-  // Convert from Zeller (0=Sat) to standard (0=Sun)
-  return ((h + 6) % 7);
-}
-
-void __attribute__((noinline)) epoch_to_tm_utc(time_t epoch, struct tm *out_tm) {
-  // Days since epoch
-  int64_t days = epoch / 86400;
-  int32_t remaining_secs = epoch % 86400;
-  if (remaining_secs < 0) {
-    days--;
-    remaining_secs += 86400;
-  }
-
-  out_tm->tm_sec = remaining_secs % 60;
-  remaining_secs /= 60;
-  out_tm->tm_min = remaining_secs % 60;
-  out_tm->tm_hour = remaining_secs / 60;
-
-  // Day of week (Jan 1, 1970 was Thursday = 4)
-  out_tm->tm_wday = static_cast<int>((days + 4) % 7);
-  if (out_tm->tm_wday < 0)
-    out_tm->tm_wday += 7;
-
-  // Calculate year (updates days to day-of-year)
-  int year = days_to_year(days);
-  out_tm->tm_year = year - 1900;
-  out_tm->tm_yday = static_cast<int>(days);
-
-  // Calculate month and day
-  int month = 1;
-  int dim;
-  while (days >= (dim = days_in_month(year, month))) {
-    days -= dim;
-    month++;
-  }
-
-  out_tm->tm_mon = month - 1;
-  out_tm->tm_mday = static_cast<int>(days) + 1;
-  out_tm->tm_isdst = 0;
-}
-
-bool skip_tz_name(const char *&p) {
-  if (*p == '<') {
-    // Angle-bracket quoted name: <+07>, <-03>, <AEST>
-    p++;  // skip '<'
-    while (*p && *p != '>') {
-      p++;
-    }
-    if (*p == '>') {
-      p++;  // skip '>'
-      return true;
-    }
-    return false;  // Unterminated
-  }
-
-  // Standard name: 3+ letters
-  const char *start = p;
-  while (*p && std::isalpha(static_cast<unsigned char>(*p))) {
-    p++;
-  }
-  return (p - start) >= 3;
-}
-
-int32_t __attribute__((noinline)) parse_offset(const char *&p) {
-  int sign = 1;
-  if (*p == '-') {
-    sign = -1;
-    p++;
-  } else if (*p == '+') {
-    p++;
-  }
-
-  int hours = parse_uint(p);
-  int minutes = 0;
-  int seconds = 0;
-
-  if (*p == ':') {
-    p++;
-    minutes = parse_uint(p);
-    if (*p == ':') {
-      p++;
-      seconds = parse_uint(p);
-    }
-  }
-
-  return sign * (hours * 3600 + minutes * 60 + seconds);
-}
-
-// Helper to parse the optional /time suffix (reuses parse_offset logic)
-static void parse_transition_time(const char *&p, DSTRule &rule) {
-  rule.time_seconds = 2 * 3600;  // Default 02:00
-  if (*p == '/') {
-    p++;
-    rule.time_seconds = parse_offset(p);
-  }
-}
-
-void __attribute__((noinline)) julian_to_month_day(int julian_day, int &out_month, int &out_day) {
-  // J format: day 1-365, Feb 29 is NOT counted even in leap years
-  // So day 60 is always March 1
-  // Iterate forward through months (no array needed)
-  int remaining = julian_day;
-  out_month = 1;
-  while (out_month <= 12) {
-    // Days in month for non-leap year (J format ignores leap years)
-    int dim = days_in_month(2001, out_month);  // 2001 is non-leap year
-    if (remaining <= dim) {
-      out_day = remaining;
-      return;
-    }
-    remaining -= dim;
-    out_month++;
-  }
-  out_day = remaining;
-}
-
-void __attribute__((noinline)) day_of_year_to_month_day(int day_of_year, int year, int &out_month, int &out_day) {
-  // Plain format: day 0-365, Feb 29 IS counted in leap years
-  // Day 0 = Jan 1
-  int remaining = day_of_year;
-  out_month = 1;
-
-  while (out_month <= 12) {
-    int days_this_month = days_in_month(year, out_month);
-    if (remaining < days_this_month) {
-      out_day = remaining + 1;
-      return;
-    }
-    remaining -= days_this_month;
-    out_month++;
-  }
-
-  // Shouldn't reach here with valid input
-  out_month = 12;
-  out_day = 31;
-}
-
-bool parse_dst_rule(const char *&p, DSTRule &rule) {
-  rule = {};  // Zero initialize
-
-  if (*p == 'M' || *p == 'm') {
-    // M format: Mm.w.d (month.week.day)
-    rule.type = DSTRuleType::MONTH_WEEK_DAY;
-    p++;
-
-    rule.month = parse_uint(p);
-    if (rule.month < 1 || rule.month > 12)
-      return false;
-
-    if (*p++ != '.')
-      return false;
-
-    rule.week = parse_uint(p);
-    if (rule.week < 1 || rule.week > 5)
-      return false;
-
-    if (*p++ != '.')
-      return false;
-
-    rule.day_of_week = parse_uint(p);
-    if (rule.day_of_week > 6)
-      return false;
-
-  } else if (*p == 'J' || *p == 'j') {
-    // J format: Jn (Julian day 1-365, not counting Feb 29)
-    rule.type = DSTRuleType::JULIAN_NO_LEAP;
-    p++;
-
-    rule.day = parse_uint(p);
-    if (rule.day < 1 || rule.day > 365)
-      return false;
-
-  } else if (std::isdigit(static_cast<unsigned char>(*p))) {
-    // Plain number format: n (day 0-365, counting Feb 29)
-    rule.type = DSTRuleType::DAY_OF_YEAR;
-
-    rule.day = parse_uint(p);
-    if (rule.day > 365)
-      return false;
-
-  } else {
-    return false;
-  }
-
-  // Parse optional /time suffix
-  parse_transition_time(p, rule);
-
-  return true;
-}
-
-// Calculate days from Jan 1 of given year to given month/day
-static int __attribute__((noinline)) days_from_year_start(int year, int month, int day) {
-  int days = day - 1;
-  for (int m = 1; m < month; m++) {
-    days += days_in_month(year, m);
-  }
-  return days;
-}
-
-// Calculate days from epoch to Jan 1 of given year (for DST transition calculations)
-// Only supports years >= 1970. Timezone is either compiled in from YAML or set by
-// Home Assistant, so pre-1970 dates are not a concern.
-static int64_t __attribute__((noinline)) days_to_year_start(int year) {
-  int64_t days = 0;
-  for (int y = 1970; y < year; y++) {
-    days += days_in_year(y);
-  }
-  return days;
-}
-
-time_t __attribute__((noinline)) calculate_dst_transition(int year, const DSTRule &rule, int32_t base_offset_seconds) {
-  int month, day;
-
-  switch (rule.type) {
-    case DSTRuleType::MONTH_WEEK_DAY: {
-      // Find the nth occurrence of day_of_week in the given month
-      int first_dow = day_of_week(year, rule.month, 1);
-
-      // Days until first occurrence of target day
-      int days_until_first = (rule.day_of_week - first_dow + 7) % 7;
-      int first_occurrence = 1 + days_until_first;
-
-      if (rule.week == 5) {
-        // "Last" occurrence - find the last one in the month
-        int dim = days_in_month(year, rule.month);
-        day = first_occurrence;
-        while (day + 7 <= dim) {
-          day += 7;
-        }
-      } else {
-        // nth occurrence
-        day = first_occurrence + (rule.week - 1) * 7;
-      }
-      month = rule.month;
-      break;
-    }
-
-    case DSTRuleType::JULIAN_NO_LEAP:
-      // J format: day 1-365, Feb 29 not counted
-      julian_to_month_day(rule.day, month, day);
-      break;
-
-    case DSTRuleType::DAY_OF_YEAR:
-      // Plain format: day 0-365, Feb 29 counted
-      day_of_year_to_month_day(rule.day, year, month, day);
-      break;
-
-    case DSTRuleType::NONE:
-      // Should never be called with NONE, but handle it gracefully
-      month = 1;
-      day = 1;
-      break;
-  }
-
-  // Calculate days from epoch to this date
-  int64_t days = days_to_year_start(year) + days_from_year_start(year, month, day);
-
-  // Convert to epoch and add transition time and base offset
-  return days * 86400 + rule.time_seconds + base_offset_seconds;
-}
-
-}  // namespace internal
-
-bool __attribute__((noinline)) is_in_dst(time_t utc_epoch, const ParsedTimezone &tz) {
-  if (!tz.has_dst()) {
-    return false;
-  }
-
-  int year = internal::epoch_to_year(utc_epoch);
-
-  // Calculate DST start and end for this year
-  // DST start transition happens in standard time
-  time_t dst_start = internal::calculate_dst_transition(year, tz.dst_start, tz.std_offset_seconds);
-  // DST end transition happens in daylight time
-  time_t dst_end = internal::calculate_dst_transition(year, tz.dst_end, tz.dst_offset_seconds);
-
-  if (dst_start < dst_end) {
-    // Northern hemisphere: DST is between start and end
-    return (utc_epoch >= dst_start && utc_epoch < dst_end);
-  } else {
-    // Southern hemisphere: DST is outside the range (wraps around year)
-    return (utc_epoch >= dst_start || utc_epoch < dst_end);
-  }
-}
-
-bool parse_posix_tz(const char *tz_string, ParsedTimezone &result) {
-  if (!tz_string || !*tz_string) {
-    return false;
-  }
-
-  const char *p = tz_string;
-
-  // Initialize result (dst_start/dst_end default to type=NONE, so has_dst() returns false)
-  result.std_offset_seconds = 0;
-  result.dst_offset_seconds = 0;
-  result.dst_start = {};
-  result.dst_end = {};
-
-  // Skip standard timezone name
-  if (!internal::skip_tz_name(p)) {
-    return false;
-  }
-
-  // Parse standard offset (required)
-  if (!*p || (!std::isdigit(static_cast<unsigned char>(*p)) && *p != '+' && *p != '-')) {
-    return false;
-  }
-  result.std_offset_seconds = internal::parse_offset(p);
-
-  // Check for DST name
-  if (!*p) {
-    return true;  // No DST
-  }
-
-  // If next char is comma, there's no DST name but there are rules (invalid)
-  if (*p == ',') {
-    return false;
-  }
-
-  // Check if there's something that looks like a DST name start
-  // (letter or angle bracket). If not, treat as trailing garbage and return success.
-  if (!std::isalpha(static_cast<unsigned char>(*p)) && *p != '<') {
-    return true;  // No DST, trailing characters ignored
-  }
-
-  if (!internal::skip_tz_name(p)) {
-    return false;  // Invalid DST name (started but malformed)
-  }
-
-  // Optional DST offset (default is std - 1 hour)
-  if (*p && *p != ',' && (std::isdigit(static_cast<unsigned char>(*p)) || *p == '+' || *p == '-')) {
-    result.dst_offset_seconds = internal::parse_offset(p);
-  } else {
-    result.dst_offset_seconds = result.std_offset_seconds - 3600;
-  }
-
-  // Parse DST rules (required when DST name is present)
-  if (*p != ',') {
-    // DST name without rules - treat as no DST since we can't determine transitions
-    return true;
-  }
-
-  p++;
-  if (!internal::parse_dst_rule(p, result.dst_start)) {
-    return false;
-  }
-
-  // Second rule is required per POSIX
-  if (*p != ',') {
-    return false;
-  }
-  p++;
-  // has_dst() now returns true since dst_start.type was set by parse_dst_rule
-  return internal::parse_dst_rule(p, result.dst_end);
-}
-
-bool epoch_to_local_tm(time_t utc_epoch, const ParsedTimezone &tz, struct tm *out_tm) {
-  if (!out_tm) {
-    return false;
-  }
-
-  // Determine DST status once (avoids duplicate is_in_dst calculation)
-  bool in_dst = is_in_dst(utc_epoch, tz);
-  int32_t offset = in_dst ? tz.dst_offset_seconds : tz.std_offset_seconds;
-
-  // Apply offset (POSIX offset is positive west, so subtract to get local)
-  time_t local_epoch = utc_epoch - offset;
-
-  internal::epoch_to_tm_utc(local_epoch, out_tm);
-  out_tm->tm_isdst = in_dst ? 1 : 0;
-
-  return true;
-}
-
-}  // namespace esphome::time
-
-#ifndef USE_HOST
-// Override libc's localtime functions to use our timezone on embedded platforms.
-// This allows user lambdas calling ::localtime() to get correct local time
-// without needing the TZ environment variable (which pulls in scanf bloat).
-// On host, we use the normal TZ mechanism since there's no memory constraint.
-
-// Thread-safe version
-extern "C" struct tm *localtime_r(const time_t *timer, struct tm *result) {
-  if (timer == nullptr || result == nullptr) {
-    return nullptr;
-  }
-  esphome::time::epoch_to_local_tm(*timer, esphome::time::get_global_tz(), result);
-  return result;
-}
-
-// Non-thread-safe version (uses static buffer, standard libc behavior)
-extern "C" struct tm *localtime(const time_t *timer) {
-  // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
-  static struct tm localtime_buf;
-  return localtime_r(timer, &localtime_buf);
-}
-#endif  // !USE_HOST
-
-#endif  // USE_TIME_TIMEZONE

esphome/components/time/posix_tz.h

@@ -1,132 +0,0 @@
-#pragma once
-
-#ifdef USE_TIME_TIMEZONE
-
-#include <cstdint>
-#include <ctime>
-
-namespace esphome::time {
-
-/// Type of DST transition rule
-enum class DSTRuleType : uint8_t {
-  NONE = 0,        ///< No DST rule (used to indicate no DST)
-  MONTH_WEEK_DAY,  ///< M format: Mm.w.d (e.g., M3.2.0 = 2nd Sunday of March)
-  JULIAN_NO_LEAP,  ///< J format: Jn (day 1-365, Feb 29 not counted)
-  DAY_OF_YEAR,     ///< Plain number: n (day 0-365, Feb 29 counted in leap years)
-};
-
-/// Rule for DST transition (packed for 32-bit: 12 bytes)
-struct DSTRule {
-  int32_t time_seconds;  ///< Seconds after midnight (default 7200 = 2:00 AM)
-  uint16_t day;          ///< Day of year (for JULIAN_NO_LEAP and DAY_OF_YEAR)
-  DSTRuleType type;      ///< Type of rule
-  uint8_t month;         ///< Month 1-12 (for MONTH_WEEK_DAY)
-  uint8_t week;          ///< Week 1-5, 5 = last (for MONTH_WEEK_DAY)
-  uint8_t day_of_week;   ///< Day 0-6, 0 = Sunday (for MONTH_WEEK_DAY)
-};
-
-/// Parsed POSIX timezone information (packed for 32-bit: 32 bytes)
-struct ParsedTimezone {
-  int32_t std_offset_seconds;  ///< Standard time offset from UTC in seconds (positive = west)
-  int32_t dst_offset_seconds;  ///< DST offset from UTC in seconds
-  DSTRule dst_start;           ///< When DST starts
-  DSTRule dst_end;             ///< When DST ends
-
-  /// Check if this timezone has DST rules
-  bool has_dst() const { return this->dst_start.type != DSTRuleType::NONE; }
-};
-
-/// Parse a POSIX TZ string into a ParsedTimezone struct.
-/// Supports formats like:
-///   - "EST5" (simple offset, no DST)
-///   - "EST5EDT,M3.2.0,M11.1.0" (with DST, M-format rules)
-///   - "CST6CDT,M3.2.0/2,M11.1.0/2" (with transition times)
-///   - "<+07>-7" (angle-bracket notation for special names)
-///   - "IST-5:30" (half-hour offsets)
-///   - "EST5EDT,J60,J300" (J-format: Julian day without leap day)
-///   - "EST5EDT,60,300" (plain day number: day of year with leap day)
-/// @param tz_string The POSIX TZ string to parse
-/// @param result Output: the parsed timezone data
-/// @return true if parsing succeeded, false on error
-bool parse_posix_tz(const char *tz_string, ParsedTimezone &result);
-
-/// Convert a UTC epoch to local time using the parsed timezone.
-/// This replaces libc's localtime() to avoid scanf dependency.
-/// @param utc_epoch Unix timestamp in UTC
-/// @param tz The parsed timezone
-/// @param[out] out_tm Output tm struct with local time
-/// @return true on success
-bool epoch_to_local_tm(time_t utc_epoch, const ParsedTimezone &tz, struct tm *out_tm);
-
-/// Set the global timezone used by epoch_to_local_tm() when called without a timezone.
-/// This is called by RealTimeClock::apply_timezone_() to enable ESPTime::from_epoch_local()
-/// to work without libc's localtime().
-void set_global_tz(const ParsedTimezone &tz);
-
-/// Get the global timezone.
-const ParsedTimezone &get_global_tz();
-
-/// Check if a given UTC epoch falls within DST for the parsed timezone.
-/// @param utc_epoch Unix timestamp in UTC
-/// @param tz The parsed timezone
-/// @return true if DST is in effect at the given time
-bool is_in_dst(time_t utc_epoch, const ParsedTimezone &tz);
-
-// Internal helper functions exposed for testing
-
-namespace internal {
-
-/// Skip a timezone name (letters or <...> quoted format)
-/// @param p Pointer to current position, updated on return
-/// @return true if a valid name was found
-bool skip_tz_name(const char *&p);
-
-/// Parse an offset in format [-]hh[:mm[:ss]]
-/// @param p Pointer to current position, updated on return
-/// @return Offset in seconds
-int32_t parse_offset(const char *&p);
-
-/// Parse a DST rule in format Mm.w.d[/time], Jn[/time], or n[/time]
-/// @param p Pointer to current position, updated on return
-/// @param rule Output: the parsed rule
-/// @return true if parsing succeeded
-bool parse_dst_rule(const char *&p, DSTRule &rule);
-
-/// Convert Julian day (J format, 1-365 not counting Feb 29) to month/day
-/// @param julian_day Day number 1-365
-/// @param[out] month Output: month 1-12
-/// @param[out] day Output: day of month
-void julian_to_month_day(int julian_day, int &month, int &day);
-
-/// Convert day of year (plain format, 0-365 counting Feb 29) to month/day
-/// @param day_of_year Day number 0-365
-/// @param year The year (for leap year calculation)
-/// @param[out] month Output: month 1-12
-/// @param[out] day Output: day of month
-void day_of_year_to_month_day(int day_of_year, int year, int &month, int &day);
-
-/// Calculate day of week for any date (0 = Sunday)
-/// Uses a simplified algorithm that works for years 1970-2099
-int day_of_week(int year, int month, int day);
-
-/// Get the number of days in a month
-int days_in_month(int year, int month);
-
-/// Check if a year is a leap year
-bool is_leap_year(int year);
-
-/// Convert epoch to year/month/day/hour/min/sec (UTC)
-void epoch_to_tm_utc(time_t epoch, struct tm *out_tm);
-
-/// Calculate the epoch timestamp for a DST transition in a given year.
-/// @param year The year (e.g., 2026)
-/// @param rule The DST rule (month, week, day_of_week, time)
-/// @param base_offset_seconds The timezone offset to apply (std or dst depending on context)
-/// @return Unix epoch timestamp of the transition
-time_t calculate_dst_transition(int year, const DSTRule &rule, int32_t base_offset_seconds);
-
-}  // namespace internal
-
-}  // namespace esphome::time
-
-#endif  // USE_TIME_TIMEZONE

esphome/components/time/real_time_clock.cpp

@@ -14,8 +14,8 @@
 #include <sys/time.h>
 #endif
 #include <cerrno>
+
 #include <cinttypes>
-#include <cstdlib>
 
 namespace esphome::time {
 
@@ -23,33 +23,9 @@ static const char *const TAG = "time";
 
 RealTimeClock::RealTimeClock() = default;
 
-ESPTime __attribute__((noinline)) RealTimeClock::now() {
-#ifdef USE_TIME_TIMEZONE
-  time_t epoch = this->timestamp_now();
-  struct tm local_tm;
-  if (epoch_to_local_tm(epoch, get_global_tz(), &local_tm)) {
-    return ESPTime::from_c_tm(&local_tm, epoch);
-  }
-  // Fallback to UTC if parsing failed
-  return ESPTime::from_epoch_utc(epoch);
-#else
-  return ESPTime::from_epoch_local(this->timestamp_now());
-#endif
-}
-
 void RealTimeClock::dump_config() {
 #ifdef USE_TIME_TIMEZONE
-  const auto &tz = get_global_tz();
-  // POSIX offset is positive west, negate for conventional UTC+X display
-  int std_h = -tz.std_offset_seconds / 3600;
-  int std_m = (std::abs(tz.std_offset_seconds) % 3600) / 60;
-  if (tz.has_dst()) {
-    int dst_h = -tz.dst_offset_seconds / 3600;
-    int dst_m = (std::abs(tz.dst_offset_seconds) % 3600) / 60;
-    ESP_LOGCONFIG(TAG, "Timezone: UTC%+d:%02d (DST UTC%+d:%02d)", std_h, std_m, dst_h, dst_m);
-  } else {
-    ESP_LOGCONFIG(TAG, "Timezone: UTC%+d:%02d", std_h, std_m);
-  }
+  ESP_LOGCONFIG(TAG, "Timezone: '%s'", this->timezone_.c_str());
 #endif
   auto time = this->now();
   ESP_LOGCONFIG(TAG, "Current time: %04d-%02d-%02d %02d:%02d:%02d", time.year, time.month, time.day_of_month, time.hour,
@@ -96,6 +72,11 @@ void RealTimeClock::synchronize_epoch_(uint32_t epoch) {
     ret = settimeofday(&timev, nullptr);
   }
 
+#ifdef USE_TIME_TIMEZONE
+  // Move timezone back to local timezone.
+  this->apply_timezone_();
+#endif
+
   if (ret != 0) {
     ESP_LOGW(TAG, "setimeofday() failed with code %d", ret);
   }
@@ -108,29 +89,9 @@ void RealTimeClock::synchronize_epoch_(uint32_t epoch) {
 }
 
 #ifdef USE_TIME_TIMEZONE
-void RealTimeClock::apply_timezone_(const char *tz) {
-  ParsedTimezone parsed{};
-
-  // Handle null or empty input - use UTC
-  if (tz == nullptr || *tz == '\0') {
-    set_global_tz(parsed);
-    return;
-  }
-
-#ifdef USE_HOST
-  // On host platform, also set TZ environment variable for libc compatibility
-  setenv("TZ", tz, 1);
+void RealTimeClock::apply_timezone_() {
+  setenv("TZ", this->timezone_.c_str(), 1);
   tzset();
-#endif
-
-  // Parse the POSIX TZ string using our custom parser
-  if (!parse_posix_tz(tz, parsed)) {
-    ESP_LOGW(TAG, "Failed to parse timezone: %s", tz);
-    // parsed stays as default (UTC) on failure
-  }
-
-  // Set global timezone for all time conversions
-  set_global_tz(parsed);
 }
 #endif
 

esphome/components/time/real_time_clock.h

@@ -6,9 +6,6 @@
 #include "esphome/core/component.h"
 #include "esphome/core/helpers.h"
 #include "esphome/core/time.h"
-#ifdef USE_TIME_TIMEZONE
-#include "posix_tz.h"
-#endif
 
 namespace esphome::time {
 
@@ -23,31 +20,26 @@ class RealTimeClock : public PollingComponent {
   explicit RealTimeClock();
 
 #ifdef USE_TIME_TIMEZONE
-  /// Set the time zone from a POSIX TZ string.
-  void set_timezone(const char *tz) { this->apply_timezone_(tz); }
-
-  /// Set the time zone from a character buffer with known length.
-  /// The buffer does not need to be null-terminated.
-  void set_timezone(const char *tz, size_t len) {
-    if (tz == nullptr) {
-      this->apply_timezone_(nullptr);
-      return;
-    }
-    // Stack buffer - TZ strings from tzdata are typically short (< 50 chars)
-    char buf[128];
-    if (len >= sizeof(buf))
-      len = sizeof(buf) - 1;
-    memcpy(buf, tz, len);
-    buf[len] = '\0';
-    this->apply_timezone_(buf);
+  /// Set the time zone.
+  void set_timezone(const std::string &tz) {
+    this->timezone_ = tz;
+    this->apply_timezone_();
   }
 
-  /// Set the time zone from a std::string.
-  void set_timezone(const std::string &tz) { this->apply_timezone_(tz.c_str()); }
+  /// Set the time zone from raw buffer, only if it differs from the current one.
+  void set_timezone(const char *tz, size_t len) {
+    if (this->timezone_.length() != len || memcmp(this->timezone_.c_str(), tz, len) != 0) {
+      this->timezone_.assign(tz, len);
+      this->apply_timezone_();
+    }
+  }
+
+  /// Get the time zone currently in use.
+  std::string get_timezone() { return this->timezone_; }
 #endif
 
   /// Get the time in the currently defined timezone.
-  ESPTime now();
+  ESPTime now() { return ESPTime::from_epoch_local(this->timestamp_now()); }
 
   /// Get the time without any time zone or DST corrections.
   ESPTime utcnow() { return ESPTime::from_epoch_utc(this->timestamp_now()); }
@@ -66,7 +58,8 @@ class RealTimeClock : public PollingComponent {
   void synchronize_epoch_(uint32_t epoch);
 
 #ifdef USE_TIME_TIMEZONE
-  void apply_timezone_(const char *tz);
+  std::string timezone_{};
+  void apply_timezone_();
 #endif
 
   CallbackManager<void()> time_sync_callback_;

esphome/components/web_server/web_server.cpp

@@ -209,7 +209,7 @@ void DeferredUpdateEventSource::deq_push_back_with_dedup_(void *source, message_
 void DeferredUpdateEventSource::process_deferred_queue_() {
   while (!deferred_queue_.empty()) {
     DeferredEvent &de = deferred_queue_.front();
-    std::string message = de.message_generator_(web_server_, de.source_);
+    auto message = de.message_generator_(web_server_, de.source_);
     if (this->send(message.c_str(), "state") != DISCARDED) {
       // O(n) but memory efficiency is more important than speed here which is why std::vector was chosen
       deferred_queue_.erase(deferred_queue_.begin());
@@ -266,7 +266,7 @@ void DeferredUpdateEventSource::deferrable_send_state(void *source, const char *
     // deferred queue still not empty which means downstream event queue full, no point trying to send first
     deq_push_back_with_dedup_(source, message_generator);
   } else {
-    std::string message = message_generator(web_server_, source);
+    auto message = message_generator(web_server_, source);
     if (this->send(message.c_str(), "state") == DISCARDED) {
       deq_push_back_with_dedup_(source, message_generator);
     } else {
@@ -320,7 +320,7 @@ void DeferredUpdateEventSourceList::on_client_connect_(DeferredUpdateEventSource
   ws->defer([ws, source]() {
     // Configure reconnect timeout and send config
     // this should always go through since the AsyncEventSourceClient event queue is empty on connect
-    std::string message = ws->get_config_json();
+    auto message = ws->get_config_json();
     source->try_send_nodefer(message.c_str(), "ping", millis(), 30000);
 
 #ifdef USE_WEBSERVER_SORTING
@@ -329,10 +329,10 @@ void DeferredUpdateEventSourceList::on_client_connect_(DeferredUpdateEventSource
       JsonObject root = builder.root();
       root[ESPHOME_F("name")] = group.second.name;
       root[ESPHOME_F("sorting_weight")] = group.second.weight;
-      message = builder.serialize();
+      auto group_msg = builder.serialize();
 
       // up to 31 groups should be able to be queued initially without defer
-      source->try_send_nodefer(message.c_str(), "sorting_group");
+      source->try_send_nodefer(group_msg.c_str(), "sorting_group");
     }
 #endif
 
@@ -365,7 +365,7 @@ void WebServer::set_css_include(const char *css_include) { this->css_include_ =
 void WebServer::set_js_include(const char *js_include) { this->js_include_ = js_include; }
 #endif
 
-std::string WebServer::get_config_json() {
+json::SerializationBuffer<> WebServer::get_config_json() {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -597,20 +597,20 @@ void WebServer::handle_sensor_request(AsyncWebServerRequest *request, const UrlM
     // Note: request->method() is always HTTP_GET here (canHandle ensures this)
     if (entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->sensor_json_(obj, obj->state, detail);
+      auto data = this->sensor_json_(obj, obj->state, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
   }
   request->send(404);
 }
-std::string WebServer::sensor_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::sensor_state_json_generator(WebServer *web_server, void *source) {
   return web_server->sensor_json_((sensor::Sensor *) (source), ((sensor::Sensor *) (source))->state, DETAIL_STATE);
 }
-std::string WebServer::sensor_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::sensor_all_json_generator(WebServer *web_server, void *source) {
   return web_server->sensor_json_((sensor::Sensor *) (source), ((sensor::Sensor *) (source))->state, DETAIL_ALL);
 }
-std::string WebServer::sensor_json_(sensor::Sensor *obj, float value, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::sensor_json_(sensor::Sensor *obj, float value, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -644,23 +644,23 @@ void WebServer::handle_text_sensor_request(AsyncWebServerRequest *request, const
     // Note: request->method() is always HTTP_GET here (canHandle ensures this)
     if (entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->text_sensor_json_(obj, obj->state, detail);
+      auto data = this->text_sensor_json_(obj, obj->state, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
   }
   request->send(404);
 }
-std::string WebServer::text_sensor_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::text_sensor_state_json_generator(WebServer *web_server, void *source) {
   return web_server->text_sensor_json_((text_sensor::TextSensor *) (source),
                                        ((text_sensor::TextSensor *) (source))->state, DETAIL_STATE);
 }
-std::string WebServer::text_sensor_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::text_sensor_all_json_generator(WebServer *web_server, void *source) {
   return web_server->text_sensor_json_((text_sensor::TextSensor *) (source),
                                        ((text_sensor::TextSensor *) (source))->state, DETAIL_ALL);
 }
-std::string WebServer::text_sensor_json_(text_sensor::TextSensor *obj, const std::string &value,
-                                         JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::text_sensor_json_(text_sensor::TextSensor *obj, const std::string &value,
+                                                         JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -705,7 +705,7 @@ void WebServer::handle_switch_request(AsyncWebServerRequest *request, const UrlM
 
     if (request->method() == HTTP_GET && entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->switch_json_(obj, obj->state, detail);
+      auto data = this->switch_json_(obj, obj->state, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -734,13 +734,13 @@ void WebServer::handle_switch_request(AsyncWebServerRequest *request, const UrlM
   }
   request->send(404);
 }
-std::string WebServer::switch_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::switch_state_json_generator(WebServer *web_server, void *source) {
   return web_server->switch_json_((switch_::Switch *) (source), ((switch_::Switch *) (source))->state, DETAIL_STATE);
 }
-std::string WebServer::switch_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::switch_all_json_generator(WebServer *web_server, void *source) {
   return web_server->switch_json_((switch_::Switch *) (source), ((switch_::Switch *) (source))->state, DETAIL_ALL);
 }
-std::string WebServer::switch_json_(switch_::Switch *obj, bool value, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::switch_json_(switch_::Switch *obj, bool value, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -762,7 +762,7 @@ void WebServer::handle_button_request(AsyncWebServerRequest *request, const UrlM
       continue;
     if (request->method() == HTTP_GET && entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->button_json_(obj, detail);
+      auto data = this->button_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
     } else if (match.method_equals(ESPHOME_F("press"))) {
       DEFER_ACTION(obj, obj->press());
@@ -775,10 +775,10 @@ void WebServer::handle_button_request(AsyncWebServerRequest *request, const UrlM
   }
   request->send(404);
 }
-std::string WebServer::button_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::button_all_json_generator(WebServer *web_server, void *source) {
   return web_server->button_json_((button::Button *) (source), DETAIL_ALL);
 }
-std::string WebServer::button_json_(button::Button *obj, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::button_json_(button::Button *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -805,22 +805,23 @@ void WebServer::handle_binary_sensor_request(AsyncWebServerRequest *request, con
     // Note: request->method() is always HTTP_GET here (canHandle ensures this)
     if (entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->binary_sensor_json_(obj, obj->state, detail);
+      auto data = this->binary_sensor_json_(obj, obj->state, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
   }
   request->send(404);
 }
-std::string WebServer::binary_sensor_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::binary_sensor_state_json_generator(WebServer *web_server, void *source) {
   return web_server->binary_sensor_json_((binary_sensor::BinarySensor *) (source),
                                          ((binary_sensor::BinarySensor *) (source))->state, DETAIL_STATE);
 }
-std::string WebServer::binary_sensor_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::binary_sensor_all_json_generator(WebServer *web_server, void *source) {
   return web_server->binary_sensor_json_((binary_sensor::BinarySensor *) (source),
                                          ((binary_sensor::BinarySensor *) (source))->state, DETAIL_ALL);
 }
-std::string WebServer::binary_sensor_json_(binary_sensor::BinarySensor *obj, bool value, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::binary_sensor_json_(binary_sensor::BinarySensor *obj, bool value,
+                                                           JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -847,7 +848,7 @@ void WebServer::handle_fan_request(AsyncWebServerRequest *request, const UrlMatc
 
     if (request->method() == HTTP_GET && entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->fan_json_(obj, detail);
+      auto data = this->fan_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
     } else if (match.method_equals(ESPHOME_F("toggle"))) {
       DEFER_ACTION(obj, obj->toggle().perform());
@@ -888,13 +889,13 @@ void WebServer::handle_fan_request(AsyncWebServerRequest *request, const UrlMatc
   }
   request->send(404);
 }
-std::string WebServer::fan_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::fan_state_json_generator(WebServer *web_server, void *source) {
   return web_server->fan_json_((fan::Fan *) (source), DETAIL_STATE);
 }
-std::string WebServer::fan_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::fan_all_json_generator(WebServer *web_server, void *source) {
   return web_server->fan_json_((fan::Fan *) (source), DETAIL_ALL);
 }
-std::string WebServer::fan_json_(fan::Fan *obj, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::fan_json_(fan::Fan *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -928,7 +929,7 @@ void WebServer::handle_light_request(AsyncWebServerRequest *request, const UrlMa
 
     if (request->method() == HTTP_GET && entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->light_json_(obj, detail);
+      auto data = this->light_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
     } else if (match.method_equals(ESPHOME_F("toggle"))) {
       DEFER_ACTION(obj, obj->toggle().perform());
@@ -967,13 +968,13 @@ void WebServer::handle_light_request(AsyncWebServerRequest *request, const UrlMa
   }
   request->send(404);
 }
-std::string WebServer::light_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::light_state_json_generator(WebServer *web_server, void *source) {
   return web_server->light_json_((light::LightState *) (source), DETAIL_STATE);
 }
-std::string WebServer::light_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::light_all_json_generator(WebServer *web_server, void *source) {
   return web_server->light_json_((light::LightState *) (source), DETAIL_ALL);
 }
-std::string WebServer::light_json_(light::LightState *obj, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::light_json_(light::LightState *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1007,7 +1008,7 @@ void WebServer::handle_cover_request(AsyncWebServerRequest *request, const UrlMa
 
     if (request->method() == HTTP_GET && entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->cover_json_(obj, detail);
+      auto data = this->cover_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1055,13 +1056,13 @@ void WebServer::handle_cover_request(AsyncWebServerRequest *request, const UrlMa
   }
   request->send(404);
 }
-std::string WebServer::cover_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::cover_state_json_generator(WebServer *web_server, void *source) {
   return web_server->cover_json_((cover::Cover *) (source), DETAIL_STATE);
 }
-std::string WebServer::cover_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::cover_all_json_generator(WebServer *web_server, void *source) {
   return web_server->cover_json_((cover::Cover *) (source), DETAIL_ALL);
 }
-std::string WebServer::cover_json_(cover::Cover *obj, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::cover_json_(cover::Cover *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1096,7 +1097,7 @@ void WebServer::handle_number_request(AsyncWebServerRequest *request, const UrlM
 
     if (request->method() == HTTP_GET && entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->number_json_(obj, obj->state, detail);
+      auto data = this->number_json_(obj, obj->state, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1115,13 +1116,13 @@ void WebServer::handle_number_request(AsyncWebServerRequest *request, const UrlM
   request->send(404);
 }
 
-std::string WebServer::number_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::number_state_json_generator(WebServer *web_server, void *source) {
   return web_server->number_json_((number::Number *) (source), ((number::Number *) (source))->state, DETAIL_STATE);
 }
-std::string WebServer::number_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::number_all_json_generator(WebServer *web_server, void *source) {
   return web_server->number_json_((number::Number *) (source), ((number::Number *) (source))->state, DETAIL_ALL);
 }
-std::string WebServer::number_json_(number::Number *obj, float value, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::number_json_(number::Number *obj, float value, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1163,7 +1164,7 @@ void WebServer::handle_date_request(AsyncWebServerRequest *request, const UrlMat
       continue;
     if (request->method() == HTTP_GET && entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->date_json_(obj, detail);
+      auto data = this->date_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1188,13 +1189,13 @@ void WebServer::handle_date_request(AsyncWebServerRequest *request, const UrlMat
   request->send(404);
 }
 
-std::string WebServer::date_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::date_state_json_generator(WebServer *web_server, void *source) {
   return web_server->date_json_((datetime::DateEntity *) (source), DETAIL_STATE);
 }
-std::string WebServer::date_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::date_all_json_generator(WebServer *web_server, void *source) {
   return web_server->date_json_((datetime::DateEntity *) (source), DETAIL_ALL);
 }
-std::string WebServer::date_json_(datetime::DateEntity *obj, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::date_json_(datetime::DateEntity *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1223,7 +1224,7 @@ void WebServer::handle_time_request(AsyncWebServerRequest *request, const UrlMat
       continue;
     if (request->method() == HTTP_GET && entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->time_json_(obj, detail);
+      auto data = this->time_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1247,13 +1248,13 @@ void WebServer::handle_time_request(AsyncWebServerRequest *request, const UrlMat
   }
   request->send(404);
 }
-std::string WebServer::time_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::time_state_json_generator(WebServer *web_server, void *source) {
   return web_server->time_json_((datetime::TimeEntity *) (source), DETAIL_STATE);
 }
-std::string WebServer::time_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::time_all_json_generator(WebServer *web_server, void *source) {
   return web_server->time_json_((datetime::TimeEntity *) (source), DETAIL_ALL);
 }
-std::string WebServer::time_json_(datetime::TimeEntity *obj, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::time_json_(datetime::TimeEntity *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1282,7 +1283,7 @@ void WebServer::handle_datetime_request(AsyncWebServerRequest *request, const Ur
       continue;
     if (request->method() == HTTP_GET && entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->datetime_json_(obj, detail);
+      auto data = this->datetime_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1306,13 +1307,13 @@ void WebServer::handle_datetime_request(AsyncWebServerRequest *request, const Ur
   }
   request->send(404);
 }
-std::string WebServer::datetime_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::datetime_state_json_generator(WebServer *web_server, void *source) {
   return web_server->datetime_json_((datetime::DateTimeEntity *) (source), DETAIL_STATE);
 }
-std::string WebServer::datetime_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::datetime_all_json_generator(WebServer *web_server, void *source) {
   return web_server->datetime_json_((datetime::DateTimeEntity *) (source), DETAIL_ALL);
 }
-std::string WebServer::datetime_json_(datetime::DateTimeEntity *obj, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::datetime_json_(datetime::DateTimeEntity *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1343,7 +1344,7 @@ void WebServer::handle_text_request(AsyncWebServerRequest *request, const UrlMat
 
     if (request->method() == HTTP_GET && entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->text_json_(obj, obj->state, detail);
+      auto data = this->text_json_(obj, obj->state, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1362,13 +1363,13 @@ void WebServer::handle_text_request(AsyncWebServerRequest *request, const UrlMat
   request->send(404);
 }
 
-std::string WebServer::text_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::text_state_json_generator(WebServer *web_server, void *source) {
   return web_server->text_json_((text::Text *) (source), ((text::Text *) (source))->state, DETAIL_STATE);
 }
-std::string WebServer::text_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::text_all_json_generator(WebServer *web_server, void *source) {
   return web_server->text_json_((text::Text *) (source), ((text::Text *) (source))->state, DETAIL_ALL);
 }
-std::string WebServer::text_json_(text::Text *obj, const std::string &value, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::text_json_(text::Text *obj, const std::string &value, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1400,7 +1401,7 @@ void WebServer::handle_select_request(AsyncWebServerRequest *request, const UrlM
 
     if (request->method() == HTTP_GET && entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->select_json_(obj, obj->has_state() ? obj->current_option() : StringRef(), detail);
+      auto data = this->select_json_(obj, obj->has_state() ? obj->current_option() : StringRef(), detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1419,15 +1420,15 @@ void WebServer::handle_select_request(AsyncWebServerRequest *request, const UrlM
   }
   request->send(404);
 }
-std::string WebServer::select_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::select_state_json_generator(WebServer *web_server, void *source) {
   auto *obj = (select::Select *) (source);
   return web_server->select_json_(obj, obj->has_state() ? obj->current_option() : StringRef(), DETAIL_STATE);
 }
-std::string WebServer::select_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::select_all_json_generator(WebServer *web_server, void *source) {
   auto *obj = (select::Select *) (source);
   return web_server->select_json_(obj, obj->has_state() ? obj->current_option() : StringRef(), DETAIL_ALL);
 }
-std::string WebServer::select_json_(select::Select *obj, StringRef value, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::select_json_(select::Select *obj, StringRef value, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1459,7 +1460,7 @@ void WebServer::handle_climate_request(AsyncWebServerRequest *request, const Url
 
     if (request->method() == HTTP_GET && entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->climate_json_(obj, detail);
+      auto data = this->climate_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1488,15 +1489,15 @@ void WebServer::handle_climate_request(AsyncWebServerRequest *request, const Url
   }
   request->send(404);
 }
-std::string WebServer::climate_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::climate_state_json_generator(WebServer *web_server, void *source) {
   // NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
   return web_server->climate_json_((climate::Climate *) (source), DETAIL_STATE);
 }
-std::string WebServer::climate_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::climate_all_json_generator(WebServer *web_server, void *source) {
   // NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
   return web_server->climate_json_((climate::Climate *) (source), DETAIL_ALL);
 }
-std::string WebServer::climate_json_(climate::Climate *obj, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::climate_json_(climate::Climate *obj, JsonDetail start_config) {
   // NOLINTBEGIN(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
   json::JsonBuilder builder;
   JsonObject root = builder.root();
@@ -1629,7 +1630,7 @@ void WebServer::handle_lock_request(AsyncWebServerRequest *request, const UrlMat
 
     if (request->method() == HTTP_GET && entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->lock_json_(obj, obj->state, detail);
+      auto data = this->lock_json_(obj, obj->state, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1658,13 +1659,13 @@ void WebServer::handle_lock_request(AsyncWebServerRequest *request, const UrlMat
   }
   request->send(404);
 }
-std::string WebServer::lock_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::lock_state_json_generator(WebServer *web_server, void *source) {
   return web_server->lock_json_((lock::Lock *) (source), ((lock::Lock *) (source))->state, DETAIL_STATE);
 }
-std::string WebServer::lock_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::lock_all_json_generator(WebServer *web_server, void *source) {
   return web_server->lock_json_((lock::Lock *) (source), ((lock::Lock *) (source))->state, DETAIL_ALL);
 }
-std::string WebServer::lock_json_(lock::Lock *obj, lock::LockState value, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::lock_json_(lock::Lock *obj, lock::LockState value, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1692,7 +1693,7 @@ void WebServer::handle_valve_request(AsyncWebServerRequest *request, const UrlMa
 
     if (request->method() == HTTP_GET && entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->valve_json_(obj, detail);
+      auto data = this->valve_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1738,13 +1739,13 @@ void WebServer::handle_valve_request(AsyncWebServerRequest *request, const UrlMa
   }
   request->send(404);
 }
-std::string WebServer::valve_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::valve_state_json_generator(WebServer *web_server, void *source) {
   return web_server->valve_json_((valve::Valve *) (source), DETAIL_STATE);
 }
-std::string WebServer::valve_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::valve_all_json_generator(WebServer *web_server, void *source) {
   return web_server->valve_json_((valve::Valve *) (source), DETAIL_ALL);
 }
-std::string WebServer::valve_json_(valve::Valve *obj, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::valve_json_(valve::Valve *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1777,7 +1778,7 @@ void WebServer::handle_alarm_control_panel_request(AsyncWebServerRequest *reques
 
     if (request->method() == HTTP_GET && entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->alarm_control_panel_json_(obj, obj->get_state(), detail);
+      auto data = this->alarm_control_panel_json_(obj, obj->get_state(), detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1817,19 +1818,19 @@ void WebServer::handle_alarm_control_panel_request(AsyncWebServerRequest *reques
   }
   request->send(404);
 }
-std::string WebServer::alarm_control_panel_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::alarm_control_panel_state_json_generator(WebServer *web_server, void *source) {
   return web_server->alarm_control_panel_json_((alarm_control_panel::AlarmControlPanel *) (source),
                                                ((alarm_control_panel::AlarmControlPanel *) (source))->get_state(),
                                                DETAIL_STATE);
 }
-std::string WebServer::alarm_control_panel_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::alarm_control_panel_all_json_generator(WebServer *web_server, void *source) {
   return web_server->alarm_control_panel_json_((alarm_control_panel::AlarmControlPanel *) (source),
                                                ((alarm_control_panel::AlarmControlPanel *) (source))->get_state(),
                                                DETAIL_ALL);
 }
-std::string WebServer::alarm_control_panel_json_(alarm_control_panel::AlarmControlPanel *obj,
-                                                 alarm_control_panel::AlarmControlPanelState value,
-                                                 JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::alarm_control_panel_json_(alarm_control_panel::AlarmControlPanel *obj,
+                                                                 alarm_control_panel::AlarmControlPanelState value,
+                                                                 JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1858,7 +1859,7 @@ void WebServer::handle_water_heater_request(AsyncWebServerRequest *request, cons
 
     if (request->method() == HTTP_GET && entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->water_heater_json_(obj, detail);
+      auto data = this->water_heater_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1894,14 +1895,14 @@ void WebServer::handle_water_heater_request(AsyncWebServerRequest *request, cons
   request->send(404);
 }
 
-std::string WebServer::water_heater_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::water_heater_state_json_generator(WebServer *web_server, void *source) {
   return web_server->water_heater_json_(static_cast<water_heater::WaterHeater *>(source), DETAIL_STATE);
 }
-std::string WebServer::water_heater_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::water_heater_all_json_generator(WebServer *web_server, void *source) {
   // NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
   return web_server->water_heater_json_(static_cast<water_heater::WaterHeater *>(source), DETAIL_ALL);
 }
-std::string WebServer::water_heater_json_(water_heater::WaterHeater *obj, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::water_heater_json_(water_heater::WaterHeater *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
   char buf[PSTR_LOCAL_SIZE];
@@ -1964,7 +1965,7 @@ void WebServer::handle_infrared_request(AsyncWebServerRequest *request, const Ur
 
     if (request->method() == HTTP_GET && entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->infrared_json_(obj, detail);
+      auto data = this->infrared_json_(obj, detail);
       request->send(200, ESPHOME_F("application/json"), data.c_str());
       return;
     }
@@ -2035,12 +2036,12 @@ void WebServer::handle_infrared_request(AsyncWebServerRequest *request, const Ur
   request->send(404);
 }
 
-std::string WebServer::infrared_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> 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::SerializationBuffer<> WebServer::infrared_json_(infrared::Infrared *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -2075,7 +2076,7 @@ void WebServer::handle_event_request(AsyncWebServerRequest *request, const UrlMa
     // Note: request->method() is always HTTP_GET here (canHandle ensures this)
     if (entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->event_json_(obj, StringRef(), detail);
+      auto data = this->event_json_(obj, StringRef(), detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -2085,16 +2086,16 @@ void WebServer::handle_event_request(AsyncWebServerRequest *request, const UrlMa
 
 static StringRef get_event_type(event::Event *event) { return event ? event->get_last_event_type() : StringRef(); }
 
-std::string WebServer::event_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::event_state_json_generator(WebServer *web_server, void *source) {
   auto *event = static_cast<event::Event *>(source);
   return web_server->event_json_(event, get_event_type(event), DETAIL_STATE);
 }
 // NOLINTBEGIN(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
-std::string WebServer::event_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::event_all_json_generator(WebServer *web_server, void *source) {
   auto *event = static_cast<event::Event *>(source);
   return web_server->event_json_(event, get_event_type(event), DETAIL_ALL);
 }
-std::string WebServer::event_json_(event::Event *obj, StringRef event_type, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::event_json_(event::Event *obj, StringRef event_type, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -2141,7 +2142,7 @@ void WebServer::handle_update_request(AsyncWebServerRequest *request, const UrlM
 
     if (request->method() == HTTP_GET && entity_match.action_is_empty) {
       auto detail = get_request_detail(request);
-      std::string data = this->update_json_(obj, detail);
+      auto data = this->update_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -2157,15 +2158,15 @@ void WebServer::handle_update_request(AsyncWebServerRequest *request, const UrlM
   }
   request->send(404);
 }
-std::string WebServer::update_state_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::update_state_json_generator(WebServer *web_server, void *source) {
   // NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
   return web_server->update_json_((update::UpdateEntity *) (source), DETAIL_STATE);
 }
-std::string WebServer::update_all_json_generator(WebServer *web_server, void *source) {
+json::SerializationBuffer<> WebServer::update_all_json_generator(WebServer *web_server, void *source) {
   // NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
   return web_server->update_json_((update::UpdateEntity *) (source), DETAIL_STATE);
 }
-std::string WebServer::update_json_(update::UpdateEntity *obj, JsonDetail start_config) {
+json::SerializationBuffer<> WebServer::update_json_(update::UpdateEntity *obj, JsonDetail start_config) {
   // NOLINTBEGIN(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
   json::JsonBuilder builder;
   JsonObject root = builder.root();

esphome/components/web_server/web_server.h

@@ -2,6 +2,7 @@
 
 #include "list_entities.h"
 
+#include "esphome/components/json/json_util.h"
 #include "esphome/components/web_server_base/web_server_base.h"
 #ifdef USE_WEBSERVER
 #include "esphome/core/component.h"
@@ -104,7 +105,7 @@ enum JsonDetail { DETAIL_ALL, DETAIL_STATE };
   can be forgotten.
 */
 #if !defined(USE_ESP32) && defined(USE_ARDUINO)
-using message_generator_t = std::string(WebServer *, void *);
+using message_generator_t = json::SerializationBuffer<>(WebServer *, void *);
 
 class DeferredUpdateEventSourceList;
 class DeferredUpdateEventSource : public AsyncEventSource {
@@ -263,7 +264,7 @@ class WebServer : public Controller,
   void handle_index_request(AsyncWebServerRequest *request);
 
   /// Return the webserver configuration as JSON.
-  std::string get_config_json();
+  json::SerializationBuffer<> get_config_json();
 
 #ifdef USE_WEBSERVER_CSS_INCLUDE
   /// Handle included css request under '/0.css'.
@@ -285,8 +286,8 @@ class WebServer : public Controller,
   /// Handle a sensor request under '/sensor/<id>'.
   void handle_sensor_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string sensor_state_json_generator(WebServer *web_server, void *source);
-  static std::string sensor_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> sensor_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> sensor_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_SWITCH
@@ -295,8 +296,8 @@ class WebServer : public Controller,
   /// Handle a switch request under '/switch/<id>/</turn_on/turn_off/toggle>'.
   void handle_switch_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string switch_state_json_generator(WebServer *web_server, void *source);
-  static std::string switch_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> switch_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> switch_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_BUTTON
@@ -304,7 +305,7 @@ class WebServer : public Controller,
   void handle_button_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
   // Buttons are stateless, so there is no button_state_json_generator
-  static std::string button_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> button_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_BINARY_SENSOR
@@ -313,8 +314,8 @@ class WebServer : public Controller,
   /// Handle a binary sensor request under '/binary_sensor/<id>'.
   void handle_binary_sensor_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string binary_sensor_state_json_generator(WebServer *web_server, void *source);
-  static std::string binary_sensor_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> binary_sensor_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> binary_sensor_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_FAN
@@ -323,8 +324,8 @@ class WebServer : public Controller,
   /// Handle a fan request under '/fan/<id>/</turn_on/turn_off/toggle>'.
   void handle_fan_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string fan_state_json_generator(WebServer *web_server, void *source);
-  static std::string fan_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> fan_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> fan_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_LIGHT
@@ -333,8 +334,8 @@ class WebServer : public Controller,
   /// Handle a light request under '/light/<id>/</turn_on/turn_off/toggle>'.
   void handle_light_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string light_state_json_generator(WebServer *web_server, void *source);
-  static std::string light_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> light_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> light_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_TEXT_SENSOR
@@ -343,8 +344,8 @@ class WebServer : public Controller,
   /// Handle a text sensor request under '/text_sensor/<id>'.
   void handle_text_sensor_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string text_sensor_state_json_generator(WebServer *web_server, void *source);
-  static std::string text_sensor_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> text_sensor_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> text_sensor_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_COVER
@@ -353,8 +354,8 @@ class WebServer : public Controller,
   /// Handle a cover request under '/cover/<id>/<open/close/stop/set>'.
   void handle_cover_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string cover_state_json_generator(WebServer *web_server, void *source);
-  static std::string cover_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> cover_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> cover_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_NUMBER
@@ -362,8 +363,8 @@ class WebServer : public Controller,
   /// Handle a number request under '/number/<id>'.
   void handle_number_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string number_state_json_generator(WebServer *web_server, void *source);
-  static std::string number_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> number_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> number_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_DATETIME_DATE
@@ -371,8 +372,8 @@ class WebServer : public Controller,
   /// Handle a date request under '/date/<id>'.
   void handle_date_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string date_state_json_generator(WebServer *web_server, void *source);
-  static std::string date_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> date_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> date_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_DATETIME_TIME
@@ -380,8 +381,8 @@ class WebServer : public Controller,
   /// Handle a time request under '/time/<id>'.
   void handle_time_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string time_state_json_generator(WebServer *web_server, void *source);
-  static std::string time_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> time_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> time_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_DATETIME_DATETIME
@@ -389,8 +390,8 @@ class WebServer : public Controller,
   /// Handle a datetime request under '/datetime/<id>'.
   void handle_datetime_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string datetime_state_json_generator(WebServer *web_server, void *source);
-  static std::string datetime_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> datetime_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> datetime_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_TEXT
@@ -398,8 +399,8 @@ class WebServer : public Controller,
   /// Handle a text input request under '/text/<id>'.
   void handle_text_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string text_state_json_generator(WebServer *web_server, void *source);
-  static std::string text_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> text_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> text_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_SELECT
@@ -407,8 +408,8 @@ class WebServer : public Controller,
   /// Handle a select request under '/select/<id>'.
   void handle_select_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string select_state_json_generator(WebServer *web_server, void *source);
-  static std::string select_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> select_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> select_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_CLIMATE
@@ -416,8 +417,8 @@ class WebServer : public Controller,
   /// Handle a climate request under '/climate/<id>'.
   void handle_climate_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string climate_state_json_generator(WebServer *web_server, void *source);
-  static std::string climate_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> climate_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> climate_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_LOCK
@@ -426,8 +427,8 @@ class WebServer : public Controller,
   /// Handle a lock request under '/lock/<id>/</lock/unlock/open>'.
   void handle_lock_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string lock_state_json_generator(WebServer *web_server, void *source);
-  static std::string lock_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> lock_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> lock_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_VALVE
@@ -436,8 +437,8 @@ class WebServer : public Controller,
   /// Handle a valve request under '/valve/<id>/<open/close/stop/set>'.
   void handle_valve_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string valve_state_json_generator(WebServer *web_server, void *source);
-  static std::string valve_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> valve_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> valve_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_ALARM_CONTROL_PANEL
@@ -446,8 +447,8 @@ class WebServer : public Controller,
   /// Handle a alarm_control_panel request under '/alarm_control_panel/<id>'.
   void handle_alarm_control_panel_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string alarm_control_panel_state_json_generator(WebServer *web_server, void *source);
-  static std::string alarm_control_panel_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> alarm_control_panel_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> alarm_control_panel_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_WATER_HEATER
@@ -456,22 +457,22 @@ class WebServer : public Controller,
   /// Handle a water_heater request under '/water_heater/<id>/<mode/set>'.
   void handle_water_heater_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string water_heater_state_json_generator(WebServer *web_server, void *source);
-  static std::string water_heater_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> water_heater_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> 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);
+  static json::SerializationBuffer<> infrared_all_json_generator(WebServer *web_server, void *source);
 #endif
 
 #ifdef USE_EVENT
   void on_event(event::Event *obj) override;
 
-  static std::string event_state_json_generator(WebServer *web_server, void *source);
-  static std::string event_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> event_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> event_all_json_generator(WebServer *web_server, void *source);
 
   /// Handle a event request under '/event<id>'.
   void handle_event_request(AsyncWebServerRequest *request, const UrlMatch &match);
@@ -483,8 +484,8 @@ class WebServer : public Controller,
   /// Handle a update request under '/update/<id>'.
   void handle_update_request(AsyncWebServerRequest *request, const UrlMatch &match);
 
-  static std::string update_state_json_generator(WebServer *web_server, void *source);
-  static std::string update_all_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> update_state_json_generator(WebServer *web_server, void *source);
+  static json::SerializationBuffer<> update_all_json_generator(WebServer *web_server, void *source);
 #endif
 
   /// Override the web handler's canHandle method.
@@ -609,71 +610,74 @@ class WebServer : public Controller,
 
  private:
 #ifdef USE_SENSOR
-  std::string sensor_json_(sensor::Sensor *obj, float value, JsonDetail start_config);
+  json::SerializationBuffer<> sensor_json_(sensor::Sensor *obj, float value, JsonDetail start_config);
 #endif
 #ifdef USE_SWITCH
-  std::string switch_json_(switch_::Switch *obj, bool value, JsonDetail start_config);
+  json::SerializationBuffer<> switch_json_(switch_::Switch *obj, bool value, JsonDetail start_config);
 #endif
 #ifdef USE_BUTTON
-  std::string button_json_(button::Button *obj, JsonDetail start_config);
+  json::SerializationBuffer<> button_json_(button::Button *obj, JsonDetail start_config);
 #endif
 #ifdef USE_BINARY_SENSOR
-  std::string binary_sensor_json_(binary_sensor::BinarySensor *obj, bool value, JsonDetail start_config);
+  json::SerializationBuffer<> binary_sensor_json_(binary_sensor::BinarySensor *obj, bool value,
+                                                  JsonDetail start_config);
 #endif
 #ifdef USE_FAN
-  std::string fan_json_(fan::Fan *obj, JsonDetail start_config);
+  json::SerializationBuffer<> fan_json_(fan::Fan *obj, JsonDetail start_config);
 #endif
 #ifdef USE_LIGHT
-  std::string light_json_(light::LightState *obj, JsonDetail start_config);
+  json::SerializationBuffer<> light_json_(light::LightState *obj, JsonDetail start_config);
 #endif
 #ifdef USE_TEXT_SENSOR
-  std::string text_sensor_json_(text_sensor::TextSensor *obj, const std::string &value, JsonDetail start_config);
+  json::SerializationBuffer<> text_sensor_json_(text_sensor::TextSensor *obj, const std::string &value,
+                                                JsonDetail start_config);
 #endif
 #ifdef USE_COVER
-  std::string cover_json_(cover::Cover *obj, JsonDetail start_config);
+  json::SerializationBuffer<> cover_json_(cover::Cover *obj, JsonDetail start_config);
 #endif
 #ifdef USE_NUMBER
-  std::string number_json_(number::Number *obj, float value, JsonDetail start_config);
+  json::SerializationBuffer<> number_json_(number::Number *obj, float value, JsonDetail start_config);
 #endif
 #ifdef USE_DATETIME_DATE
-  std::string date_json_(datetime::DateEntity *obj, JsonDetail start_config);
+  json::SerializationBuffer<> date_json_(datetime::DateEntity *obj, JsonDetail start_config);
 #endif
 #ifdef USE_DATETIME_TIME
-  std::string time_json_(datetime::TimeEntity *obj, JsonDetail start_config);
+  json::SerializationBuffer<> time_json_(datetime::TimeEntity *obj, JsonDetail start_config);
 #endif
 #ifdef USE_DATETIME_DATETIME
-  std::string datetime_json_(datetime::DateTimeEntity *obj, JsonDetail start_config);
+  json::SerializationBuffer<> datetime_json_(datetime::DateTimeEntity *obj, JsonDetail start_config);
 #endif
 #ifdef USE_TEXT
-  std::string text_json_(text::Text *obj, const std::string &value, JsonDetail start_config);
+  json::SerializationBuffer<> text_json_(text::Text *obj, const std::string &value, JsonDetail start_config);
 #endif
 #ifdef USE_SELECT
-  std::string select_json_(select::Select *obj, StringRef value, JsonDetail start_config);
+  json::SerializationBuffer<> select_json_(select::Select *obj, StringRef value, JsonDetail start_config);
 #endif
 #ifdef USE_CLIMATE
-  std::string climate_json_(climate::Climate *obj, JsonDetail start_config);
+  json::SerializationBuffer<> climate_json_(climate::Climate *obj, JsonDetail start_config);
 #endif
 #ifdef USE_LOCK
-  std::string lock_json_(lock::Lock *obj, lock::LockState value, JsonDetail start_config);
+  json::SerializationBuffer<> lock_json_(lock::Lock *obj, lock::LockState value, JsonDetail start_config);
 #endif
 #ifdef USE_VALVE
-  std::string valve_json_(valve::Valve *obj, JsonDetail start_config);
+  json::SerializationBuffer<> valve_json_(valve::Valve *obj, JsonDetail start_config);
 #endif
 #ifdef USE_ALARM_CONTROL_PANEL
-  std::string alarm_control_panel_json_(alarm_control_panel::AlarmControlPanel *obj,
-                                        alarm_control_panel::AlarmControlPanelState value, JsonDetail start_config);
+  json::SerializationBuffer<> alarm_control_panel_json_(alarm_control_panel::AlarmControlPanel *obj,
+                                                        alarm_control_panel::AlarmControlPanelState value,
+                                                        JsonDetail start_config);
 #endif
 #ifdef USE_EVENT
-  std::string event_json_(event::Event *obj, StringRef event_type, JsonDetail start_config);
+  json::SerializationBuffer<> event_json_(event::Event *obj, StringRef event_type, JsonDetail start_config);
 #endif
 #ifdef USE_WATER_HEATER
-  std::string water_heater_json_(water_heater::WaterHeater *obj, JsonDetail start_config);
+  json::SerializationBuffer<> water_heater_json_(water_heater::WaterHeater *obj, JsonDetail start_config);
 #endif
 #ifdef USE_INFRARED
-  std::string infrared_json_(infrared::Infrared *obj, JsonDetail start_config);
+  json::SerializationBuffer<> infrared_json_(infrared::Infrared *obj, JsonDetail start_config);
 #endif
 #ifdef USE_UPDATE
-  std::string update_json_(update::UpdateEntity *obj, JsonDetail start_config);
+  json::SerializationBuffer<> update_json_(update::UpdateEntity *obj, JsonDetail start_config);
 #endif
 };
 

esphome/components/web_server_idf/web_server_idf.cpp

@@ -507,7 +507,7 @@ AsyncEventSourceResponse::AsyncEventSourceResponse(const AsyncWebServerRequest *
 
   // Configure reconnect timeout and send config
   // this should always go through since the tcp send buffer is empty on connect
-  std::string message = ws->get_config_json();
+  auto message = ws->get_config_json();
   this->try_send_nodefer(message.c_str(), "ping", millis(), 30000);
 
 #ifdef USE_WEBSERVER_SORTING
@@ -561,7 +561,7 @@ void AsyncEventSourceResponse::deq_push_back_with_dedup_(void *source, message_g
 void AsyncEventSourceResponse::process_deferred_queue_() {
   while (!deferred_queue_.empty()) {
     DeferredEvent &de = deferred_queue_.front();
-    std::string message = de.message_generator_(web_server_, de.source_);
+    auto message = de.message_generator_(web_server_, de.source_);
     if (this->try_send_nodefer(message.c_str(), "state")) {
       // O(n) but memory efficiency is more important than speed here which is why std::vector was chosen
       deferred_queue_.erase(deferred_queue_.begin());
@@ -798,7 +798,7 @@ void AsyncEventSourceResponse::deferrable_send_state(void *source, const char *e
     // trying to send first
     deq_push_back_with_dedup_(source, message_generator);
   } else {
-    std::string message = message_generator(web_server_, source);
+    auto message = message_generator(web_server_, source);
     if (!this->try_send_nodefer(message.c_str(), "state")) {
       deq_push_back_with_dedup_(source, message_generator);
     }

esphome/components/web_server_idf/web_server_idf.h

@@ -16,6 +16,7 @@
 #include <vector>
 
 #ifdef USE_WEBSERVER
+#include "esphome/components/json/json_util.h"
 #include "esphome/components/web_server/list_entities.h"
 #endif
 
@@ -250,7 +251,7 @@ class AsyncWebHandler {
 class AsyncEventSource;
 class AsyncEventSourceResponse;
 
-using message_generator_t = std::string(esphome::web_server::WebServer *, void *);
+using message_generator_t = json::SerializationBuffer<>(esphome::web_server::WebServer *, void *);
 
 /*
   This class holds a pointer to the source component that wants to publish a state event, and a pointer to a function

esphome/core/time.cpp

@@ -2,6 +2,7 @@
 #include "helpers.h"
 
 #include <algorithm>
+#include <cinttypes>
 
 namespace esphome {
 
@@ -66,121 +67,56 @@ std::string ESPTime::strftime(const char *format) {
 
 std::string ESPTime::strftime(const std::string &format) { return this->strftime(format.c_str()); }
 
-// Helper to parse exactly N digits, returns false if not enough digits
-static bool parse_digits(const char *&p, const char *end, int count, uint16_t &value) {
-  value = 0;
-  for (int i = 0; i < count; i++) {
-    if (p >= end || *p < '0' || *p > '9')
-      return false;
-    value = value * 10 + (*p - '0');
-    p++;
-  }
-  return true;
-}
-
-// Helper to check for expected character
-static bool expect_char(const char *&p, const char *end, char expected) {
-  if (p >= end || *p != expected)
-    return false;
-  p++;
-  return true;
-}
-
 bool ESPTime::strptime(const char *time_to_parse, size_t len, ESPTime &esp_time) {
-  // Supported formats:
-  //   YYYY-MM-DD HH:MM:SS (19 chars)
-  //   YYYY-MM-DD HH:MM    (16 chars)
-  //   YYYY-MM-DD          (10 chars)
-  //   HH:MM:SS            (8 chars)
-  //   HH:MM               (5 chars)
+  uint16_t year;
+  uint8_t month;
+  uint8_t day;
+  uint8_t hour;
+  uint8_t minute;
+  uint8_t second;
+  int num;
+  const int ilen = static_cast<int>(len);
 
-  if (time_to_parse == nullptr || len == 0)
+  if (sscanf(time_to_parse, "%04hu-%02hhu-%02hhu %02hhu:%02hhu:%02hhu %n", &year, &month, &day,  // NOLINT
+             &hour,                                                                              // NOLINT
+             &minute,                                                                            // NOLINT
+             &second, &num) == 6 &&                                                              // NOLINT
+      num == ilen) {
+    esp_time.year = year;
+    esp_time.month = month;
+    esp_time.day_of_month = day;
+    esp_time.hour = hour;
+    esp_time.minute = minute;
+    esp_time.second = second;
+  } else if (sscanf(time_to_parse, "%04hu-%02hhu-%02hhu %02hhu:%02hhu %n", &year, &month, &day,  // NOLINT
+                    &hour,                                                                       // NOLINT
+                    &minute, &num) == 5 &&                                                       // NOLINT
+             num == ilen) {
+    esp_time.year = year;
+    esp_time.month = month;
+    esp_time.day_of_month = day;
+    esp_time.hour = hour;
+    esp_time.minute = minute;
+    esp_time.second = 0;
+  } else if (sscanf(time_to_parse, "%02hhu:%02hhu:%02hhu %n", &hour, &minute, &second, &num) == 3 &&  // NOLINT
+             num == ilen) {
+    esp_time.hour = hour;
+    esp_time.minute = minute;
+    esp_time.second = second;
+  } else if (sscanf(time_to_parse, "%02hhu:%02hhu %n", &hour, &minute, &num) == 2 &&  // NOLINT
+             num == ilen) {
+    esp_time.hour = hour;
+    esp_time.minute = minute;
+    esp_time.second = 0;
+  } else if (sscanf(time_to_parse, "%04hu-%02hhu-%02hhu %n", &year, &month, &day, &num) == 3 &&  // NOLINT
+             num == ilen) {
+    esp_time.year = year;
+    esp_time.month = month;
+    esp_time.day_of_month = day;
+  } else {
     return false;
-
-  const char *p = time_to_parse;
-  const char *end = time_to_parse + len;
-  uint16_t v1, v2, v3, v4, v5, v6;
-
-  // Try date formats first (start with 4-digit year)
-  if (len >= 10 && time_to_parse[4] == '-') {
-    // YYYY-MM-DD...
-    if (!parse_digits(p, end, 4, v1))
-      return false;
-    if (!expect_char(p, end, '-'))
-      return false;
-    if (!parse_digits(p, end, 2, v2))
-      return false;
-    if (!expect_char(p, end, '-'))
-      return false;
-    if (!parse_digits(p, end, 2, v3))
-      return false;
-
-    esp_time.year = v1;
-    esp_time.month = v2;
-    esp_time.day_of_month = v3;
-
-    if (p == end) {
-      // YYYY-MM-DD (date only)
-      return true;
-    }
-
-    if (!expect_char(p, end, ' '))
-      return false;
-
-    // Continue with time part: HH:MM[:SS]
-    if (!parse_digits(p, end, 2, v4))
-      return false;
-    if (!expect_char(p, end, ':'))
-      return false;
-    if (!parse_digits(p, end, 2, v5))
-      return false;
-
-    esp_time.hour = v4;
-    esp_time.minute = v5;
-
-    if (p == end) {
-      // YYYY-MM-DD HH:MM
-      esp_time.second = 0;
-      return true;
-    }
-
-    if (!expect_char(p, end, ':'))
-      return false;
-    if (!parse_digits(p, end, 2, v6))
-      return false;
-
-    esp_time.second = v6;
-    return p == end;  // YYYY-MM-DD HH:MM:SS
   }
-
-  // Try time-only formats (HH:MM[:SS])
-  if (len >= 5 && time_to_parse[2] == ':') {
-    if (!parse_digits(p, end, 2, v1))
-      return false;
-    if (!expect_char(p, end, ':'))
-      return false;
-    if (!parse_digits(p, end, 2, v2))
-      return false;
-
-    esp_time.hour = v1;
-    esp_time.minute = v2;
-
-    if (p == end) {
-      // HH:MM
-      esp_time.second = 0;
-      return true;
-    }
-
-    if (!expect_char(p, end, ':'))
-      return false;
-    if (!parse_digits(p, end, 2, v3))
-      return false;
-
-    esp_time.second = v3;
-    return p == end;  // HH:MM:SS
-  }
-
-  return false;
+  return true;
 }
 
 void ESPTime::increment_second() {
@@ -257,67 +193,27 @@ void ESPTime::recalc_timestamp_utc(bool use_day_of_year) {
 }
 
 void ESPTime::recalc_timestamp_local() {
-#ifdef USE_TIME_TIMEZONE
-  // Calculate timestamp as if fields were UTC
-  this->recalc_timestamp_utc(false);
-  if (this->timestamp == -1) {
-    return;  // Invalid time
-  }
+  struct tm tm;
 
-  // Now convert from local to UTC by adding the offset
-  // POSIX: local = utc - offset, so utc = local + offset
-  const auto &tz = time::get_global_tz();
+  tm.tm_year = this->year - 1900;
+  tm.tm_mon = this->month - 1;
+  tm.tm_mday = this->day_of_month;
+  tm.tm_hour = this->hour;
+  tm.tm_min = this->minute;
+  tm.tm_sec = this->second;
+  tm.tm_isdst = -1;
 
-  if (!tz.has_dst()) {
-    // No DST - just apply standard offset
-    this->timestamp += tz.std_offset_seconds;
-    return;
-  }
-
-  // Try both interpretations to match libc mktime() with tm_isdst=-1
-  // For ambiguous times (fall-back repeated hour), prefer standard time
-  // For invalid times (spring-forward skipped hour), libc normalizes forward
-  time_t utc_if_dst = this->timestamp + tz.dst_offset_seconds;
-  time_t utc_if_std = this->timestamp + tz.std_offset_seconds;
-
-  bool dst_valid = time::is_in_dst(utc_if_dst, tz);
-  bool std_valid = !time::is_in_dst(utc_if_std, tz);
-
-  if (dst_valid && std_valid) {
-    // Ambiguous time (repeated hour during fall-back) - prefer standard time
-    this->timestamp = utc_if_std;
-  } else if (dst_valid) {
-    // Only DST interpretation is valid
-    this->timestamp = utc_if_dst;
-  } else if (std_valid) {
-    // Only standard interpretation is valid
-    this->timestamp = utc_if_std;
-  } else {
-    // Invalid time (skipped hour during spring-forward)
-    // libc normalizes forward: 02:30 CST -> 08:30 UTC -> 03:30 CDT
-    // Using std offset achieves this since the UTC result falls during DST
-    this->timestamp = utc_if_std;
-  }
-#else
-  // No timezone support - treat as UTC
-  this->recalc_timestamp_utc(false);
-#endif
+  this->timestamp = mktime(&tm);
 }
 
 int32_t ESPTime::timezone_offset() {
-#ifdef USE_TIME_TIMEZONE
   time_t now = ::time(nullptr);
-  const auto &tz = time::get_global_tz();
-  // POSIX offset is positive west, but we return offset to add to UTC to get local
-  // So we negate the POSIX offset
-  if (time::is_in_dst(now, tz)) {
-    return -tz.dst_offset_seconds;
-  }
-  return -tz.std_offset_seconds;
-#else
-  // No timezone support - no offset
-  return 0;
-#endif
+  struct tm local_tm = *::localtime(&now);
+  local_tm.tm_isdst = 0;  // Cause mktime to ignore daylight saving time because we want to include it in the offset.
+  time_t local_time = mktime(&local_tm);
+  struct tm utc_tm = *::gmtime(&now);
+  time_t utc_time = mktime(&utc_tm);
+  return static_cast<int32_t>(local_time - utc_time);
 }
 
 bool ESPTime::operator<(const ESPTime &other) const { return this->timestamp < other.timestamp; }

esphome/core/time.h

@@ -7,10 +7,6 @@
 #include <span>
 #include <string>
 
-#ifdef USE_TIME_TIMEZONE
-#include "esphome/components/time/posix_tz.h"
-#endif
-
 namespace esphome {
 
 template<typename T> bool increment_time_value(T &current, uint16_t begin, uint16_t end);
@@ -109,17 +105,11 @@ struct ESPTime {
    * @return The generated ESPTime
    */
   static ESPTime from_epoch_local(time_t epoch) {
-#ifdef USE_TIME_TIMEZONE
-    struct tm local_tm;
-    if (time::epoch_to_local_tm(epoch, time::get_global_tz(), &local_tm)) {
-      return ESPTime::from_c_tm(&local_tm, epoch);
+    struct tm *c_tm = ::localtime(&epoch);
+    if (c_tm == nullptr) {
+      return ESPTime{};  // Return an invalid ESPTime
     }
-    // Fallback to UTC if conversion failed
-    return ESPTime::from_epoch_utc(epoch);
-#else
-    // No timezone support - return UTC (no TZ configured, localtime would return UTC anyway)
-    return ESPTime::from_epoch_utc(epoch);
-#endif
+    return ESPTime::from_c_tm(c_tm, epoch);
   }
   /** Convert an UTC epoch timestamp to a UTC time ESPTime instance.
    *

script/cpp_unit_test.py

@@ -66,7 +66,6 @@ def create_test_config(config_name: str, includes: list[str]) -> dict:
                 ],
                 "build_flags": [
                     "-Og",  # optimize for debug
-                    "-DUSE_TIME_TIMEZONE",  # enable timezone code paths for testing
                 ],
                 "debug_build_flags": [  # only for debug builds
                     "-g3",  # max debug info

tests/components/json/common.yaml

@@ -4,15 +4,16 @@ interval:
   - interval: 60s
     then:
       - lambda: |-
-          // Test build_json
-          std::string json_str = esphome::json::build_json([](JsonObject root) {
+          // Test build_json - returns SerializationBuffer, use auto to avoid heap allocation
+          auto json_buf = esphome::json::build_json([](JsonObject root) {
             root["sensor"] = "temperature";
             root["value"] = 23.5;
             root["unit"] = "°C";
           });
-          ESP_LOGD("test", "Built JSON: %s", json_str.c_str());
+          ESP_LOGD("test", "Built JSON: %s", json_buf.c_str());
 
-          // Test parse_json
+          // Test parse_json - implicit conversion to std::string for backward compatibility
+          std::string json_str = json_buf;
           bool parse_ok = esphome::json::parse_json(json_str, [](JsonObject root) {
             if (root["sensor"].is<const char*>() && root["value"].is<float>()) {
               const char* sensor = root["sensor"];
@@ -26,10 +27,10 @@ interval:
           });
           ESP_LOGD("test", "Parse result (JSON syntax only): %s", parse_ok ? "success" : "failed");
 
-          // Test JsonBuilder class
+          // Test JsonBuilder class - returns SerializationBuffer
           esphome::json::JsonBuilder builder;
           JsonObject obj = builder.root();
           obj["test"] = "direct_builder";
           obj["count"] = 42;
-          std::string result = builder.serialize();
+          auto result = builder.serialize();
           ESP_LOGD("test", "JsonBuilder result: %s", result.c_str());

tests/components/pmsx003/common.yaml

@@ -8,11 +8,11 @@ sensor:
     pm_10_0:
       name: PM 10.0 Concentration
     pm_1_0_std:
-      name: PM 1.0 Standard Atmospheric Concentration
+      name: PM 1.0 Standard Atmospher Concentration
     pm_2_5_std:
-      name: PM 2.5 Standard Atmospheric Concentration
+      name: PM 2.5 Standard Atmospher Concentration
     pm_10_0_std:
-      name: PM 10.0 Standard Atmospheric Concentration
+      name: PM 10.0 Standard Atmospher Concentration
     pm_0_3um:
       name: Particulate Count >0.3um
     pm_0_5um: