Merge branch 'dev' into esp32_ard_compile_time

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

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());
-      auto json_buf = builder.serialize();
+      std::string json_str = builder.serialize();
       this->parent_->send_action_response(call_id, success, StringRef(error_message),
-                                          reinterpret_cast<const uint8_t *>(json_buf.data()), json_buf.size());
+                                          reinterpret_cast<const uint8_t *>(json_str.data()), json_str.size());
       return;
     }
 #endif

esphome/components/bme680_bsec/__init__.py

@@ -89,8 +89,9 @@ async def to_code(config):
         var.set_state_save_interval(config[CONF_STATE_SAVE_INTERVAL].total_milliseconds)
     )
 
-    # Although this component does not use SPI, the BSEC library requires the SPI library
+    # Although this component does not use SPI/Wire directly, the BSEC library requires them
     cg.add_library("SPI", None)
+    cg.add_library("Wire", None)
 
     cg.add_define("USE_BSEC")
     cg.add_library("boschsensortec/BSEC Software Library", "1.6.1480")

esphome/components/esp32/__init__.py

@@ -5,6 +5,7 @@ import logging
 import os
 from pathlib import Path
 import re
+import shutil
 
 from esphome import yaml_util
 import esphome.codegen as cg
@@ -50,6 +51,7 @@ from esphome.writer import clean_cmake_cache
 
 from .boards import BOARDS, STANDARD_BOARDS
 from .const import (  # noqa
+    KEY_ARDUINO_LIBRARIES,
     KEY_BOARD,
     KEY_COMPONENTS,
     KEY_ESP32,
@@ -146,6 +148,168 @@ DEFAULT_EXCLUDED_IDF_COMPONENTS = (
     "wifi_provisioning",  # WiFi provisioning - ESPHome uses its own improv implementation
 )
 
+# Additional IDF managed components to exclude for Arduino framework builds
+# These are pulled in by the Arduino framework's idf_component.yml but not used by ESPHome
+# Note: Component names include the namespace prefix (e.g., "espressif__cbor") because
+# that's how managed components are registered in the IDF build system
+# List includes direct dependencies from arduino-esp32/idf_component.yml
+# plus transitive dependencies from RainMaker/Insights (except espressif/mdns which we need)
+ARDUINO_EXCLUDED_IDF_COMPONENTS = (
+    "chmorgan__esp-libhelix-mp3",  # MP3 decoder - not used
+    "espressif__cbor",  # CBOR library - only used by RainMaker/Insights
+    "espressif__esp-dsp",  # DSP library - not used
+    "espressif__esp-modbus",  # Modbus - ESPHome has its own
+    "espressif__esp-sr",  # Speech recognition - not used
+    "espressif__esp-zboss-lib",  # Zigbee ZBOSS library - not used
+    "espressif__esp-zigbee-lib",  # Zigbee library - not used
+    "espressif__esp_diag_data_store",  # Diagnostics - not used
+    "espressif__esp_diagnostics",  # Diagnostics - not used
+    "espressif__esp_hosted",  # ESP hosted - only for ESP32-P4
+    "espressif__esp_insights",  # ESP Insights - not used
+    "espressif__esp_modem",  # Modem library - not used
+    "espressif__esp_rainmaker",  # RainMaker - not used
+    "espressif__esp_rcp_update",  # RCP update - RainMaker transitive dep
+    "espressif__esp_schedule",  # Schedule - RainMaker transitive dep
+    "espressif__esp_secure_cert_mgr",  # Secure cert - RainMaker transitive dep
+    "espressif__esp_wifi_remote",  # WiFi remote - only for ESP32-P4
+    "espressif__json_generator",  # JSON generator - RainMaker transitive dep
+    "espressif__json_parser",  # JSON parser - RainMaker transitive dep
+    "espressif__lan867x",  # Ethernet PHY - ESPHome uses ESP-IDF ethernet directly
+    "espressif__libsodium",  # Crypto - ESPHome uses its own noise-c library
+    "espressif__network_provisioning",  # Network provisioning - not used
+    "espressif__qrcode",  # QR code - not used
+    "espressif__rmaker_common",  # RainMaker common - not used
+    "joltwallet__littlefs",  # LittleFS - ESPHome doesn't use filesystem
+)
+
+# Mapping of Arduino libraries to IDF managed components they require
+# When an Arduino library is enabled via cg.add_library(), these components
+# are automatically un-stubbed from ARDUINO_EXCLUDED_IDF_COMPONENTS.
+#
+# Note: Some libraries (Matter, LittleFS, ESP_SR, WiFiProv, ArduinoOTA) already have
+# conditional maybe_add_component() calls in arduino-esp32/CMakeLists.txt that handle
+# their managed component dependencies. Our mapping is primarily needed for libraries
+# that don't have such conditionals (Ethernet, PPP, Zigbee, RainMaker, Insights, etc.)
+# and to ensure the stubs are removed from our idf_component.yml overrides.
+ARDUINO_LIBRARY_IDF_COMPONENTS: dict[str, tuple[str, ...]] = {
+    "BLE": ("esp_driver_gptimer",),
+    "BluetoothSerial": ("esp_driver_gptimer",),
+    "ESP_HostedOTA": ("espressif__esp_hosted", "espressif__esp_wifi_remote"),
+    "ESP_SR": ("espressif__esp-sr",),
+    "Ethernet": ("espressif__lan867x",),
+    "FFat": ("fatfs",),
+    "Insights": (
+        "espressif__cbor",
+        "espressif__esp_insights",
+        "espressif__esp_diagnostics",
+        "espressif__esp_diag_data_store",
+        "espressif__rmaker_common",  # Transitive dep from esp_insights
+    ),
+    "LittleFS": ("joltwallet__littlefs",),
+    "Matter": ("espressif__esp_matter",),
+    "PPP": ("espressif__esp_modem",),
+    "RainMaker": (
+        # Direct deps from idf_component.yml
+        "espressif__cbor",
+        "espressif__esp_rainmaker",
+        "espressif__esp_insights",
+        "espressif__esp_diagnostics",
+        "espressif__esp_diag_data_store",
+        "espressif__rmaker_common",
+        "espressif__qrcode",
+        # Transitive deps from esp_rainmaker
+        "espressif__esp_rcp_update",
+        "espressif__esp_schedule",
+        "espressif__esp_secure_cert_mgr",
+        "espressif__json_generator",
+        "espressif__json_parser",
+        "espressif__network_provisioning",
+    ),
+    "SD": ("fatfs",),
+    "SD_MMC": ("fatfs",),
+    "SPIFFS": ("spiffs",),
+    "WiFiProv": ("espressif__network_provisioning", "espressif__qrcode"),
+    "Zigbee": ("espressif__esp-zigbee-lib", "espressif__esp-zboss-lib"),
+}
+
+# Arduino library to Arduino library dependencies
+# When enabling one library, also enable its dependencies
+# Kconfig "select" statements don't work with CONFIG_ARDUINO_SELECTIVE_COMPILATION
+ARDUINO_LIBRARY_DEPENDENCIES: dict[str, tuple[str, ...]] = {
+    "Ethernet": ("Network",),
+    "WiFi": ("Network",),
+}
+
+
+def _idf_component_stub_name(component: str) -> str:
+    """Get stub directory name from IDF component name.
+
+    Component names are typically namespace__name (e.g., espressif__cbor).
+    Returns just the name part (e.g., cbor). If no namespace is present,
+    returns the original component name.
+    """
+    _prefix, sep, suffix = component.partition("__")
+    return suffix if sep else component
+
+
+def _idf_component_dep_name(component: str) -> str:
+    """Convert IDF component name to dependency format.
+
+    Converts espressif__cbor to espressif/cbor.
+    """
+    return component.replace("__", "/")
+
+
+# Arduino libraries to disable by default when using Arduino framework
+# ESPHome uses ESP-IDF APIs directly; we only need the Arduino core
+# (HardwareSerial, Print, Stream, GPIO functions which are always compiled)
+# Components use cg.add_library() which auto-enables any they need
+# This list must match ARDUINO_ALL_LIBRARIES from arduino-esp32/CMakeLists.txt
+ARDUINO_DISABLED_LIBRARIES: frozenset[str] = frozenset(
+    {
+        "ArduinoOTA",
+        "AsyncUDP",
+        "BLE",
+        "BluetoothSerial",
+        "DNSServer",
+        "EEPROM",
+        "ESP_HostedOTA",
+        "ESP_I2S",
+        "ESP_NOW",
+        "ESP_SR",
+        "ESPmDNS",
+        "Ethernet",
+        "FFat",
+        "FS",
+        "Hash",
+        "HTTPClient",
+        "HTTPUpdate",
+        "Insights",
+        "LittleFS",
+        "Matter",
+        "NetBIOS",
+        "Network",
+        "NetworkClientSecure",
+        "OpenThread",
+        "PPP",
+        "Preferences",
+        "RainMaker",
+        "SD",
+        "SD_MMC",
+        "SimpleBLE",
+        "SPI",
+        "SPIFFS",
+        "Ticker",
+        "Update",
+        "USB",
+        "WebServer",
+        "WiFi",
+        "WiFiProv",
+        "Wire",
+        "Zigbee",
+    }
+)
+
 # ESP32 (original) chip revision options
 # Setting minimum revision to 3.0 or higher:
 # - Reduces flash size by excluding workaround code for older chip bugs
@@ -237,7 +401,13 @@ def set_core_data(config):
     CORE.data[KEY_ESP32][KEY_COMPONENTS] = {}
     # Initialize with default exclusions - components can call include_builtin_idf_component()
     # to re-enable any they need
-    CORE.data[KEY_ESP32][KEY_EXCLUDE_COMPONENTS] = set(DEFAULT_EXCLUDED_IDF_COMPONENTS)
+    excluded = set(DEFAULT_EXCLUDED_IDF_COMPONENTS)
+    # Add Arduino-specific managed component exclusions when using Arduino framework
+    if conf[CONF_TYPE] == FRAMEWORK_ARDUINO:
+        excluded.update(ARDUINO_EXCLUDED_IDF_COMPONENTS)
+    CORE.data[KEY_ESP32][KEY_EXCLUDE_COMPONENTS] = excluded
+    # Initialize Arduino library tracking - cg.add_library() auto-enables libraries
+    CORE.data[KEY_ESP32][KEY_ARDUINO_LIBRARIES] = set()
     CORE.data[KEY_CORE][KEY_FRAMEWORK_VERSION] = cv.Version.parse(
         config[CONF_FRAMEWORK][CONF_VERSION]
     )
@@ -385,6 +555,26 @@ def include_builtin_idf_component(name: str) -> None:
     CORE.data[KEY_ESP32][KEY_EXCLUDE_COMPONENTS].discard(name)
 
 
+def _enable_arduino_library(name: str) -> None:
+    """Enable an Arduino library that is disabled by default.
+
+    This is called automatically by CORE.add_library() when a component adds
+    an Arduino library via cg.add_library(). Components should not call this
+    directly - just use cg.add_library("LibName", None).
+
+    Args:
+        name: The library name (e.g., "Wire", "SPI", "WiFi")
+    """
+    enabled_libs: set[str] = CORE.data[KEY_ESP32][KEY_ARDUINO_LIBRARIES]
+    enabled_libs.add(name)
+    # Also enable any required Arduino library dependencies
+    for dep_lib in ARDUINO_LIBRARY_DEPENDENCIES.get(name, ()):
+        enabled_libs.add(dep_lib)
+    # Also enable any required IDF components
+    for idf_component in ARDUINO_LIBRARY_IDF_COMPONENTS.get(name, ()):
+        include_builtin_idf_component(idf_component)
+
+
 def add_extra_script(stage: str, filename: str, path: Path):
     """Add an extra script to the project."""
     key = f"{stage}:{filename}"
@@ -739,9 +929,10 @@ 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_select() or require_vfs_dir()
+# Components that need VFS features can call require_vfs_*() functions
 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"
@@ -768,6 +959,15 @@ 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.
 
@@ -1116,6 +1316,27 @@ async def _write_exclude_components() -> None:
         )
 
 
+@coroutine_with_priority(CoroPriority.FINAL)
+async def _write_arduino_libraries_sdkconfig() -> None:
+    """Write Arduino selective compilation sdkconfig after all components have added libraries.
+
+    This must run at FINAL priority so that all components have had a chance to call
+    cg.add_library() which auto-enables Arduino libraries via _enable_arduino_library().
+    """
+    if KEY_ESP32 not in CORE.data:
+        return
+    # Enable Arduino selective compilation to disable unused Arduino libraries
+    # ESPHome uses ESP-IDF APIs directly; we only need the Arduino core
+    # (HardwareSerial, Print, Stream, GPIO functions which are always compiled)
+    # cg.add_library() auto-enables needed libraries; users can also add
+    # libraries via esphome: libraries: config which calls cg.add_library()
+    add_idf_sdkconfig_option("CONFIG_ARDUINO_SELECTIVE_COMPILATION", True)
+    enabled_libs = CORE.data[KEY_ESP32].get(KEY_ARDUINO_LIBRARIES, set())
+    for lib in ARDUINO_DISABLED_LIBRARIES:
+        # Enable if explicitly requested, disable otherwise
+        add_idf_sdkconfig_option(f"CONFIG_ARDUINO_SELECTIVE_{lib}", lib in enabled_libs)
+
+
 @coroutine_with_priority(CoroPriority.FINAL)
 async def _add_yaml_idf_components(components: list[ConfigType]):
     """Add IDF components from YAML config with final priority to override code-added components."""
@@ -1372,11 +1593,18 @@ 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)
-    # ESPHome doesn't use termios functions on ESP32 (only used in host UART driver).
+    # 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().
     # Saves approximately 1.8KB of flash when disabled (default).
-    add_idf_sdkconfig_option(
-        "CONFIG_VFS_SUPPORT_TERMIOS", not advanced[CONF_DISABLE_VFS_SUPPORT_TERMIOS]
-    )
+    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]
+        )
 
     # Disable VFS support for select() with file descriptors
     # ESPHome only uses select() with sockets via lwip_select(), which still works.
@@ -1523,6 +1751,11 @@ async def to_code(config):
     # Default exclusions are added in set_core_data() during config validation.
     CORE.add_job(_write_exclude_components)
 
+    # Write Arduino selective compilation sdkconfig at FINAL priority after all
+    # components have had a chance to call cg.add_library() to enable libraries they need.
+    if conf[CONF_TYPE] == FRAMEWORK_ARDUINO:
+        CORE.add_job(_write_arduino_libraries_sdkconfig)
+
 
 APP_PARTITION_SIZES = {
     "2MB": 0x0C0000,  # 768 KB
@@ -1603,11 +1836,49 @@ def _write_sdkconfig():
 
 def _write_idf_component_yml():
     yml_path = CORE.relative_build_path("src/idf_component.yml")
+    dependencies: dict[str, dict] = {}
+
+    # For Arduino builds, override unused managed components from the Arduino framework
+    # by pointing them to empty stub directories using override_path
+    # This prevents the IDF component manager from downloading the real components
+    if CORE.using_arduino:
+        # Determine which IDF components are needed by enabled Arduino libraries
+        enabled_libs = CORE.data[KEY_ESP32].get(KEY_ARDUINO_LIBRARIES, set())
+        required_idf_components = {
+            comp
+            for lib in enabled_libs
+            for comp in ARDUINO_LIBRARY_IDF_COMPONENTS.get(lib, ())
+        }
+
+        # Only stub components that are not required by any enabled Arduino library
+        components_to_stub = (
+            set(ARDUINO_EXCLUDED_IDF_COMPONENTS) - required_idf_components
+        )
+
+        stubs_dir = CORE.relative_build_path("component_stubs")
+        stubs_dir.mkdir(exist_ok=True)
+        for component_name in components_to_stub:
+            # Create stub directory with minimal CMakeLists.txt
+            stub_path = stubs_dir / _idf_component_stub_name(component_name)
+            stub_path.mkdir(exist_ok=True)
+            stub_cmake = stub_path / "CMakeLists.txt"
+            if not stub_cmake.exists():
+                stub_cmake.write_text("idf_component_register()\n")
+            dependencies[_idf_component_dep_name(component_name)] = {
+                "version": "*",
+                "override_path": str(stub_path),
+            }
+
+        # Remove stubs for components that are now required by enabled libraries
+        for component_name in required_idf_components:
+            stub_path = stubs_dir / _idf_component_stub_name(component_name)
+            if stub_path.exists():
+                shutil.rmtree(stub_path)
+
     if CORE.data[KEY_ESP32][KEY_COMPONENTS]:
         components: dict = CORE.data[KEY_ESP32][KEY_COMPONENTS]
-        dependencies = {}
         for name, component in components.items():
-            dependency = {}
+            dependency: dict[str, str] = {}
             if component[KEY_REF]:
                 dependency["version"] = component[KEY_REF]
             if component[KEY_REPO]:
@@ -1615,9 +1886,8 @@ def _write_idf_component_yml():
             if component[KEY_PATH]:
                 dependency["path"] = component[KEY_PATH]
             dependencies[name] = dependency
-        contents = yaml_util.dump({"dependencies": dependencies})
-    else:
-        contents = ""
+
+    contents = yaml_util.dump({"dependencies": dependencies}) if dependencies else ""
     if write_file_if_changed(yml_path, contents):
         dependencies_lock = CORE.relative_build_path("dependencies.lock")
         if dependencies_lock.is_file():

esphome/components/esp32/const.py

@@ -7,6 +7,7 @@ KEY_VARIANT = "variant"
 KEY_SDKCONFIG_OPTIONS = "sdkconfig_options"
 KEY_COMPONENTS = "components"
 KEY_EXCLUDE_COMPONENTS = "exclude_components"
+KEY_ARDUINO_LIBRARIES = "arduino_libraries"
 KEY_REPO = "repo"
 KEY_REF = "ref"
 KEY_REFRESH = "refresh"

esphome/components/espnow/__init__.py

@@ -13,7 +13,7 @@ from esphome.const import (
     CONF_TRIGGER_ID,
     CONF_WIFI,
 )
-from esphome.core import CORE, HexInt
+from esphome.core import HexInt
 from esphome.types import ConfigType
 
 CODEOWNERS = ["@jesserockz"]
@@ -124,9 +124,6 @@ async def to_code(config):
     var = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(var, config)
 
-    if CORE.using_arduino:
-        cg.add_library("WiFi", None)
-
     # ESP-NOW uses wake_loop_threadsafe() to wake the main loop from ESP-NOW callbacks
     # This enables low-latency event processing instead of waiting for select() timeout
     socket.require_wake_loop_threadsafe()

esphome/components/ethernet/__init__.py

@@ -427,9 +427,6 @@ async def to_code(config):
         # Add LAN867x 10BASE-T1S PHY support component
         add_idf_component(name="espressif/lan867x", ref="2.0.0")
 
-    if CORE.using_arduino:
-        cg.add_library("WiFi", None)
-
     CORE.add_job(final_step)
 
 

esphome/components/i2s_audio/media_player/__init__.py

@@ -114,6 +114,7 @@ async def to_code(config):
         cg.add(var.set_external_dac_channels(2 if config[CONF_MODE] == "stereo" else 1))
         cg.add(var.set_i2s_comm_fmt_lsb(config[CONF_I2S_COMM_FMT] == "lsb"))
 
+    cg.add_library("WiFi", None)
     cg.add_library("NetworkClientSecure", None)
     cg.add_library("HTTPClient", None)
     cg.add_library("esphome/ESP32-audioI2S", "2.3.0")

esphome/components/json/json_util.cpp

@@ -15,7 +15,7 @@ static const char *const TAG = "json";
 static SpiRamAllocator global_json_allocator;
 #endif
 
-SerializationBuffer<> build_json(const json_build_t &f) {
+std::string build_json(const json_build_t &f) {
   // NOLINTBEGIN(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
   JsonBuilder builder;
   JsonObject root = builder.root();
@@ -61,62 +61,14 @@ JsonDocument parse_json(const uint8_t *data, size_t len) {
   // NOLINTEND(clang-analyzer-cplusplus.NewDeleteLeaks)
 }
 
-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)
-
+std::string JsonBuilder::serialize() {
   if (doc_.overflowed()) {
     ESP_LOGE(TAG, "JSON document overflow");
-    auto *buf = result.data_writable_();
-    buf[0] = '{';
-    buf[1] = '}';
-    buf[2] = '\0';
-    result.set_size_(2);
-    return result;
+    return "{}";
   }
-
-  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;
+  std::string output;
+  serializeJson(doc_, output);
+  return output;
 }
 
 }  // namespace json

esphome/components/json/json_util.h

@@ -1,7 +1,5 @@
 #pragma once
 
-#include <cstring>
-#include <string>
 #include <vector>
 
 #include "esphome/core/defines.h"
@@ -16,108 +14,6 @@
 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
@@ -150,8 +46,7 @@ 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.
-/// Returns SerializationBuffer for stack-first allocation; implicitly converts to std::string.
-SerializationBuffer<> build_json(const json_build_t &f);
+std::string 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);
@@ -174,9 +69,7 @@ class JsonBuilder {
     return root_;
   }
 
-  /// 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();
+  std::string serialize();
 
  private:
 #ifdef USE_PSRAM

esphome/components/logger/__init__.py

@@ -16,6 +16,8 @@ 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 (
@@ -397,9 +399,15 @@ 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/midea/climate.py

@@ -30,7 +30,7 @@ from esphome.const import (
     UNIT_PERCENT,
     UNIT_WATT,
 )
-from esphome.core import coroutine
+from esphome.core import CORE, coroutine
 
 CODEOWNERS = ["@dudanov"]
 DEPENDENCIES = ["climate", "uart"]
@@ -290,4 +290,7 @@ async def to_code(config):
     if CONF_HUMIDITY_SETPOINT in config:
         sens = await sensor.new_sensor(config[CONF_HUMIDITY_SETPOINT])
         cg.add(var.set_humidity_setpoint_sensor(sens))
+    # MideaUART library requires WiFi (WiFi auto-enables Network via dependency mapping)
+    if CORE.is_esp32:
+        cg.add_library("WiFi", None)
     cg.add_library("dudanov/MideaUART", "1.1.9")

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) {
-  auto message = json::build_json(f);
-  return this->publish(topic, message.c_str(), message.size(), qos, retain);
+  std::string message = json::build_json(f);
+  return this->publish(topic, message.c_str(), message.length(), qos, retain);
 }
 
 void MQTTClientComponent::enable() {

esphome/components/network/__init__.py

@@ -137,8 +137,7 @@ CONFIG_SCHEMA = cv.Schema(
 @coroutine_with_priority(CoroPriority.NETWORK)
 async def to_code(config):
     cg.add_define("USE_NETWORK")
-    if CORE.using_arduino and CORE.is_esp32:
-        cg.add_library("Networking", None)
+    # ESP32 with Arduino uses ESP-IDF network APIs directly, no Arduino Network library needed
 
     # Apply high performance networking settings
     # Config can explicitly enable/disable, or default to component-driven behavior

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();
-    auto message = de.message_generator_(web_server_, de.source_);
+    std::string 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 {
-    auto message = message_generator(web_server_, source);
+    std::string 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
-    auto message = ws->get_config_json();
+    std::string 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;
-      auto group_msg = builder.serialize();
+      message = builder.serialize();
 
       // up to 31 groups should be able to be queued initially without defer
-      source->try_send_nodefer(group_msg.c_str(), "sorting_group");
+      source->try_send_nodefer(message.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
 
-json::SerializationBuffer<> WebServer::get_config_json() {
+std::string 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);
-      auto data = this->sensor_json_(obj, obj->state, detail);
+      std::string data = this->sensor_json_(obj, obj->state, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
   }
   request->send(404);
 }
-json::SerializationBuffer<> WebServer::sensor_state_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::sensor_state_json_generator(WebServer *web_server, void *source) {
   return web_server->sensor_json_((sensor::Sensor *) (source), ((sensor::Sensor *) (source))->state, DETAIL_STATE);
 }
-json::SerializationBuffer<> WebServer::sensor_all_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::sensor_all_json_generator(WebServer *web_server, void *source) {
   return web_server->sensor_json_((sensor::Sensor *) (source), ((sensor::Sensor *) (source))->state, DETAIL_ALL);
 }
-json::SerializationBuffer<> WebServer::sensor_json_(sensor::Sensor *obj, float value, JsonDetail start_config) {
+std::string 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);
-      auto data = this->text_sensor_json_(obj, obj->state, detail);
+      std::string data = this->text_sensor_json_(obj, obj->state, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
   }
   request->send(404);
 }
-json::SerializationBuffer<> WebServer::text_sensor_state_json_generator(WebServer *web_server, void *source) {
+std::string 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);
 }
-json::SerializationBuffer<> WebServer::text_sensor_all_json_generator(WebServer *web_server, void *source) {
+std::string 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);
 }
-json::SerializationBuffer<> WebServer::text_sensor_json_(text_sensor::TextSensor *obj, const std::string &value,
-                                                         JsonDetail start_config) {
+std::string 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);
-      auto data = this->switch_json_(obj, obj->state, detail);
+      std::string 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);
 }
-json::SerializationBuffer<> WebServer::switch_state_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::switch_state_json_generator(WebServer *web_server, void *source) {
   return web_server->switch_json_((switch_::Switch *) (source), ((switch_::Switch *) (source))->state, DETAIL_STATE);
 }
-json::SerializationBuffer<> WebServer::switch_all_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::switch_all_json_generator(WebServer *web_server, void *source) {
   return web_server->switch_json_((switch_::Switch *) (source), ((switch_::Switch *) (source))->state, DETAIL_ALL);
 }
-json::SerializationBuffer<> WebServer::switch_json_(switch_::Switch *obj, bool value, JsonDetail start_config) {
+std::string 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);
-      auto data = this->button_json_(obj, detail);
+      std::string 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);
 }
-json::SerializationBuffer<> WebServer::button_all_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::button_all_json_generator(WebServer *web_server, void *source) {
   return web_server->button_json_((button::Button *) (source), DETAIL_ALL);
 }
-json::SerializationBuffer<> WebServer::button_json_(button::Button *obj, JsonDetail start_config) {
+std::string WebServer::button_json_(button::Button *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -805,23 +805,22 @@ 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);
-      auto data = this->binary_sensor_json_(obj, obj->state, detail);
+      std::string data = this->binary_sensor_json_(obj, obj->state, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
   }
   request->send(404);
 }
-json::SerializationBuffer<> WebServer::binary_sensor_state_json_generator(WebServer *web_server, void *source) {
+std::string 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);
 }
-json::SerializationBuffer<> WebServer::binary_sensor_all_json_generator(WebServer *web_server, void *source) {
+std::string 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);
 }
-json::SerializationBuffer<> WebServer::binary_sensor_json_(binary_sensor::BinarySensor *obj, bool value,
-                                                           JsonDetail start_config) {
+std::string WebServer::binary_sensor_json_(binary_sensor::BinarySensor *obj, bool value, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -848,7 +847,7 @@ 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);
-      auto data = this->fan_json_(obj, detail);
+      std::string 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());
@@ -889,13 +888,13 @@ void WebServer::handle_fan_request(AsyncWebServerRequest *request, const UrlMatc
   }
   request->send(404);
 }
-json::SerializationBuffer<> WebServer::fan_state_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::fan_state_json_generator(WebServer *web_server, void *source) {
   return web_server->fan_json_((fan::Fan *) (source), DETAIL_STATE);
 }
-json::SerializationBuffer<> WebServer::fan_all_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::fan_all_json_generator(WebServer *web_server, void *source) {
   return web_server->fan_json_((fan::Fan *) (source), DETAIL_ALL);
 }
-json::SerializationBuffer<> WebServer::fan_json_(fan::Fan *obj, JsonDetail start_config) {
+std::string WebServer::fan_json_(fan::Fan *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -929,7 +928,7 @@ 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);
-      auto data = this->light_json_(obj, detail);
+      std::string 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());
@@ -968,13 +967,13 @@ void WebServer::handle_light_request(AsyncWebServerRequest *request, const UrlMa
   }
   request->send(404);
 }
-json::SerializationBuffer<> WebServer::light_state_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::light_state_json_generator(WebServer *web_server, void *source) {
   return web_server->light_json_((light::LightState *) (source), DETAIL_STATE);
 }
-json::SerializationBuffer<> WebServer::light_all_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::light_all_json_generator(WebServer *web_server, void *source) {
   return web_server->light_json_((light::LightState *) (source), DETAIL_ALL);
 }
-json::SerializationBuffer<> WebServer::light_json_(light::LightState *obj, JsonDetail start_config) {
+std::string WebServer::light_json_(light::LightState *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1008,7 +1007,7 @@ 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);
-      auto data = this->cover_json_(obj, detail);
+      std::string data = this->cover_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1056,13 +1055,13 @@ void WebServer::handle_cover_request(AsyncWebServerRequest *request, const UrlMa
   }
   request->send(404);
 }
-json::SerializationBuffer<> WebServer::cover_state_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::cover_state_json_generator(WebServer *web_server, void *source) {
   return web_server->cover_json_((cover::Cover *) (source), DETAIL_STATE);
 }
-json::SerializationBuffer<> WebServer::cover_all_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::cover_all_json_generator(WebServer *web_server, void *source) {
   return web_server->cover_json_((cover::Cover *) (source), DETAIL_ALL);
 }
-json::SerializationBuffer<> WebServer::cover_json_(cover::Cover *obj, JsonDetail start_config) {
+std::string WebServer::cover_json_(cover::Cover *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1097,7 +1096,7 @@ 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);
-      auto data = this->number_json_(obj, obj->state, detail);
+      std::string data = this->number_json_(obj, obj->state, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1116,13 +1115,13 @@ void WebServer::handle_number_request(AsyncWebServerRequest *request, const UrlM
   request->send(404);
 }
 
-json::SerializationBuffer<> WebServer::number_state_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::number_state_json_generator(WebServer *web_server, void *source) {
   return web_server->number_json_((number::Number *) (source), ((number::Number *) (source))->state, DETAIL_STATE);
 }
-json::SerializationBuffer<> WebServer::number_all_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::number_all_json_generator(WebServer *web_server, void *source) {
   return web_server->number_json_((number::Number *) (source), ((number::Number *) (source))->state, DETAIL_ALL);
 }
-json::SerializationBuffer<> WebServer::number_json_(number::Number *obj, float value, JsonDetail start_config) {
+std::string WebServer::number_json_(number::Number *obj, float value, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1164,7 +1163,7 @@ 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);
-      auto data = this->date_json_(obj, detail);
+      std::string data = this->date_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1189,13 +1188,13 @@ void WebServer::handle_date_request(AsyncWebServerRequest *request, const UrlMat
   request->send(404);
 }
 
-json::SerializationBuffer<> WebServer::date_state_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::date_state_json_generator(WebServer *web_server, void *source) {
   return web_server->date_json_((datetime::DateEntity *) (source), DETAIL_STATE);
 }
-json::SerializationBuffer<> WebServer::date_all_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::date_all_json_generator(WebServer *web_server, void *source) {
   return web_server->date_json_((datetime::DateEntity *) (source), DETAIL_ALL);
 }
-json::SerializationBuffer<> WebServer::date_json_(datetime::DateEntity *obj, JsonDetail start_config) {
+std::string WebServer::date_json_(datetime::DateEntity *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1224,7 +1223,7 @@ 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);
-      auto data = this->time_json_(obj, detail);
+      std::string data = this->time_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1248,13 +1247,13 @@ void WebServer::handle_time_request(AsyncWebServerRequest *request, const UrlMat
   }
   request->send(404);
 }
-json::SerializationBuffer<> WebServer::time_state_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::time_state_json_generator(WebServer *web_server, void *source) {
   return web_server->time_json_((datetime::TimeEntity *) (source), DETAIL_STATE);
 }
-json::SerializationBuffer<> WebServer::time_all_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::time_all_json_generator(WebServer *web_server, void *source) {
   return web_server->time_json_((datetime::TimeEntity *) (source), DETAIL_ALL);
 }
-json::SerializationBuffer<> WebServer::time_json_(datetime::TimeEntity *obj, JsonDetail start_config) {
+std::string WebServer::time_json_(datetime::TimeEntity *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1283,7 +1282,7 @@ 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);
-      auto data = this->datetime_json_(obj, detail);
+      std::string data = this->datetime_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1307,13 +1306,13 @@ void WebServer::handle_datetime_request(AsyncWebServerRequest *request, const Ur
   }
   request->send(404);
 }
-json::SerializationBuffer<> WebServer::datetime_state_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::datetime_state_json_generator(WebServer *web_server, void *source) {
   return web_server->datetime_json_((datetime::DateTimeEntity *) (source), DETAIL_STATE);
 }
-json::SerializationBuffer<> WebServer::datetime_all_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::datetime_all_json_generator(WebServer *web_server, void *source) {
   return web_server->datetime_json_((datetime::DateTimeEntity *) (source), DETAIL_ALL);
 }
-json::SerializationBuffer<> WebServer::datetime_json_(datetime::DateTimeEntity *obj, JsonDetail start_config) {
+std::string WebServer::datetime_json_(datetime::DateTimeEntity *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1344,7 +1343,7 @@ 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);
-      auto data = this->text_json_(obj, obj->state, detail);
+      std::string data = this->text_json_(obj, obj->state, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1363,13 +1362,13 @@ void WebServer::handle_text_request(AsyncWebServerRequest *request, const UrlMat
   request->send(404);
 }
 
-json::SerializationBuffer<> WebServer::text_state_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::text_state_json_generator(WebServer *web_server, void *source) {
   return web_server->text_json_((text::Text *) (source), ((text::Text *) (source))->state, DETAIL_STATE);
 }
-json::SerializationBuffer<> WebServer::text_all_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::text_all_json_generator(WebServer *web_server, void *source) {
   return web_server->text_json_((text::Text *) (source), ((text::Text *) (source))->state, DETAIL_ALL);
 }
-json::SerializationBuffer<> WebServer::text_json_(text::Text *obj, const std::string &value, JsonDetail start_config) {
+std::string WebServer::text_json_(text::Text *obj, const std::string &value, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1401,7 +1400,7 @@ 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);
-      auto data = this->select_json_(obj, obj->has_state() ? obj->current_option() : StringRef(), detail);
+      std::string data = this->select_json_(obj, obj->has_state() ? obj->current_option() : StringRef(), detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1420,15 +1419,15 @@ void WebServer::handle_select_request(AsyncWebServerRequest *request, const UrlM
   }
   request->send(404);
 }
-json::SerializationBuffer<> WebServer::select_state_json_generator(WebServer *web_server, void *source) {
+std::string 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);
 }
-json::SerializationBuffer<> WebServer::select_all_json_generator(WebServer *web_server, void *source) {
+std::string 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);
 }
-json::SerializationBuffer<> WebServer::select_json_(select::Select *obj, StringRef value, JsonDetail start_config) {
+std::string WebServer::select_json_(select::Select *obj, StringRef value, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1460,7 +1459,7 @@ 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);
-      auto data = this->climate_json_(obj, detail);
+      std::string data = this->climate_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1489,15 +1488,15 @@ void WebServer::handle_climate_request(AsyncWebServerRequest *request, const Url
   }
   request->send(404);
 }
-json::SerializationBuffer<> WebServer::climate_state_json_generator(WebServer *web_server, void *source) {
+std::string 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);
 }
-json::SerializationBuffer<> WebServer::climate_all_json_generator(WebServer *web_server, void *source) {
+std::string 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);
 }
-json::SerializationBuffer<> WebServer::climate_json_(climate::Climate *obj, JsonDetail start_config) {
+std::string 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();
@@ -1630,7 +1629,7 @@ 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);
-      auto data = this->lock_json_(obj, obj->state, detail);
+      std::string data = this->lock_json_(obj, obj->state, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1659,13 +1658,13 @@ void WebServer::handle_lock_request(AsyncWebServerRequest *request, const UrlMat
   }
   request->send(404);
 }
-json::SerializationBuffer<> WebServer::lock_state_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::lock_state_json_generator(WebServer *web_server, void *source) {
   return web_server->lock_json_((lock::Lock *) (source), ((lock::Lock *) (source))->state, DETAIL_STATE);
 }
-json::SerializationBuffer<> WebServer::lock_all_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::lock_all_json_generator(WebServer *web_server, void *source) {
   return web_server->lock_json_((lock::Lock *) (source), ((lock::Lock *) (source))->state, DETAIL_ALL);
 }
-json::SerializationBuffer<> WebServer::lock_json_(lock::Lock *obj, lock::LockState value, JsonDetail start_config) {
+std::string WebServer::lock_json_(lock::Lock *obj, lock::LockState value, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1693,7 +1692,7 @@ 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);
-      auto data = this->valve_json_(obj, detail);
+      std::string data = this->valve_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1739,13 +1738,13 @@ void WebServer::handle_valve_request(AsyncWebServerRequest *request, const UrlMa
   }
   request->send(404);
 }
-json::SerializationBuffer<> WebServer::valve_state_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::valve_state_json_generator(WebServer *web_server, void *source) {
   return web_server->valve_json_((valve::Valve *) (source), DETAIL_STATE);
 }
-json::SerializationBuffer<> WebServer::valve_all_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::valve_all_json_generator(WebServer *web_server, void *source) {
   return web_server->valve_json_((valve::Valve *) (source), DETAIL_ALL);
 }
-json::SerializationBuffer<> WebServer::valve_json_(valve::Valve *obj, JsonDetail start_config) {
+std::string WebServer::valve_json_(valve::Valve *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -1778,7 +1777,7 @@ 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);
-      auto data = this->alarm_control_panel_json_(obj, obj->get_state(), detail);
+      std::string data = this->alarm_control_panel_json_(obj, obj->get_state(), detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1818,19 +1817,19 @@ void WebServer::handle_alarm_control_panel_request(AsyncWebServerRequest *reques
   }
   request->send(404);
 }
-json::SerializationBuffer<> WebServer::alarm_control_panel_state_json_generator(WebServer *web_server, void *source) {
+std::string 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);
 }
-json::SerializationBuffer<> WebServer::alarm_control_panel_all_json_generator(WebServer *web_server, void *source) {
+std::string 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);
 }
-json::SerializationBuffer<> WebServer::alarm_control_panel_json_(alarm_control_panel::AlarmControlPanel *obj,
-                                                                 alarm_control_panel::AlarmControlPanelState value,
-                                                                 JsonDetail start_config) {
+std::string 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();
 
@@ -1859,7 +1858,7 @@ 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);
-      auto data = this->water_heater_json_(obj, detail);
+      std::string data = this->water_heater_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -1895,14 +1894,14 @@ void WebServer::handle_water_heater_request(AsyncWebServerRequest *request, cons
   request->send(404);
 }
 
-json::SerializationBuffer<> WebServer::water_heater_state_json_generator(WebServer *web_server, void *source) {
+std::string 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);
 }
-json::SerializationBuffer<> WebServer::water_heater_all_json_generator(WebServer *web_server, void *source) {
+std::string 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);
 }
-json::SerializationBuffer<> WebServer::water_heater_json_(water_heater::WaterHeater *obj, JsonDetail start_config) {
+std::string WebServer::water_heater_json_(water_heater::WaterHeater *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
   char buf[PSTR_LOCAL_SIZE];
@@ -1965,7 +1964,7 @@ 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);
-      auto data = this->infrared_json_(obj, detail);
+      std::string data = this->infrared_json_(obj, detail);
       request->send(200, ESPHOME_F("application/json"), data.c_str());
       return;
     }
@@ -2036,12 +2035,12 @@ void WebServer::handle_infrared_request(AsyncWebServerRequest *request, const Ur
   request->send(404);
 }
 
-json::SerializationBuffer<> WebServer::infrared_all_json_generator(WebServer *web_server, void *source) {
+std::string WebServer::infrared_all_json_generator(WebServer *web_server, void *source) {
   // NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks) false positive with ArduinoJson
   return web_server->infrared_json_(static_cast<infrared::Infrared *>(source), DETAIL_ALL);
 }
 
-json::SerializationBuffer<> WebServer::infrared_json_(infrared::Infrared *obj, JsonDetail start_config) {
+std::string WebServer::infrared_json_(infrared::Infrared *obj, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -2076,7 +2075,7 @@ 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);
-      auto data = this->event_json_(obj, StringRef(), detail);
+      std::string data = this->event_json_(obj, StringRef(), detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -2086,16 +2085,16 @@ 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(); }
 
-json::SerializationBuffer<> WebServer::event_state_json_generator(WebServer *web_server, void *source) {
+std::string 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
-json::SerializationBuffer<> WebServer::event_all_json_generator(WebServer *web_server, void *source) {
+std::string 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);
 }
-json::SerializationBuffer<> WebServer::event_json_(event::Event *obj, StringRef event_type, JsonDetail start_config) {
+std::string WebServer::event_json_(event::Event *obj, StringRef event_type, JsonDetail start_config) {
   json::JsonBuilder builder;
   JsonObject root = builder.root();
 
@@ -2142,7 +2141,7 @@ 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);
-      auto data = this->update_json_(obj, detail);
+      std::string data = this->update_json_(obj, detail);
       request->send(200, "application/json", data.c_str());
       return;
     }
@@ -2158,15 +2157,15 @@ void WebServer::handle_update_request(AsyncWebServerRequest *request, const UrlM
   }
   request->send(404);
 }
-json::SerializationBuffer<> WebServer::update_state_json_generator(WebServer *web_server, void *source) {
+std::string 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);
 }
-json::SerializationBuffer<> WebServer::update_all_json_generator(WebServer *web_server, void *source) {
+std::string 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);
 }
-json::SerializationBuffer<> WebServer::update_json_(update::UpdateEntity *obj, JsonDetail start_config) {
+std::string 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

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

esphome/components/web_server_base/__init__.py

@@ -38,11 +38,8 @@ async def to_code(config):
         cg.add_define("WEB_SERVER_DEFAULT_HEADERS_COUNT", 1)
         return
 
+    # ESP32 uses IDF web server (early return above), so this is for other Arduino platforms
     if CORE.using_arduino:
-        if CORE.is_esp32:
-            cg.add_library("WiFi", None)
-            cg.add_library("FS", None)
-            cg.add_library("Update", None)
         if CORE.is_esp8266:
             cg.add_library("ESP8266WiFi", None)
         if CORE.is_libretiny:

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
-  auto message = ws->get_config_json();
+  std::string 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();
-    auto message = de.message_generator_(web_server_, de.source_);
+    std::string 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 {
-    auto message = message_generator(web_server_, source);
+    std::string 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

@@ -16,7 +16,6 @@
 #include <vector>
 
 #ifdef USE_WEBSERVER
-#include "esphome/components/json/json_util.h"
 #include "esphome/components/web_server/list_entities.h"
 #endif
 
@@ -251,7 +250,7 @@ class AsyncWebHandler {
 class AsyncEventSource;
 class AsyncEventSourceResponse;
 
-using message_generator_t = json::SerializationBuffer<>(esphome::web_server::WebServer *, void *);
+using message_generator_t = std::string(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/components/wled/__init__.py

@@ -3,6 +3,7 @@ from esphome.components.light.effects import register_addressable_effect
 from esphome.components.light.types import AddressableLightEffect
 import esphome.config_validation as cv
 from esphome.const import CONF_NAME, CONF_PORT
+from esphome.core import CORE
 
 wled_ns = cg.esphome_ns.namespace("wled")
 WLEDLightEffect = wled_ns.class_("WLEDLightEffect", AddressableLightEffect)
@@ -27,4 +28,6 @@ async def wled_light_effect_to_code(config, effect_id):
     cg.add(effect.set_port(config[CONF_PORT]))
     cg.add(effect.set_sync_group_mask(config[CONF_SYNC_GROUP_MASK]))
     cg.add(effect.set_blank_on_start(config[CONF_BLANK_ON_START]))
+    if CORE.is_esp32:
+        cg.add_library("WiFi", None)
     return effect

esphome/core/__init__.py

@@ -888,6 +888,16 @@ class EsphomeCore:
             library.name if "/" not in library.name else library.name.split("/")[-1]
         )
 
+        # Auto-enable Arduino libraries on ESP32 Arduino builds
+        if self.is_esp32 and self.using_arduino:
+            from esphome.components.esp32 import (
+                ARDUINO_DISABLED_LIBRARIES,
+                _enable_arduino_library,
+            )
+
+            if short_name in ARDUINO_DISABLED_LIBRARIES:
+                _enable_arduino_library(short_name)
+
         if short_name not in self.platformio_libraries:
             _LOGGER.debug("Adding library: %s", library)
             self.platformio_libraries[short_name] = library

tests/components/i2s_audio/test.esp32-ard.yaml

@@ -0,0 +1,16 @@
+substitutions:
+  i2s_bclk_pin: GPIO15
+  i2s_lrclk_pin: GPIO4
+  i2s_mclk_pin: GPIO5
+
+<<: !include common.yaml
+
+wifi:
+  ssid: test
+  password: test1234
+
+media_player:
+  - platform: i2s_audio
+    name: Test Media Player
+    dac_type: internal
+    mode: stereo

tests/components/json/common.yaml

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

tests/unit_tests/test_core.py

@@ -780,3 +780,78 @@ class TestEsphomeCore:
         target.config = {const.CONF_ESPHOME: {"name": "test"}, "logger": {}}
 
         assert target.has_networking is False
+
+    def test_add_library__esp32_arduino_enables_disabled_library(self, target):
+        """Test add_library auto-enables Arduino libraries on ESP32 Arduino builds."""
+        target.data[const.KEY_CORE] = {
+            const.KEY_TARGET_PLATFORM: "esp32",
+            const.KEY_TARGET_FRAMEWORK: "arduino",
+        }
+
+        library = core.Library("WiFi", None)
+
+        with patch("esphome.components.esp32._enable_arduino_library") as mock_enable:
+            target.add_library(library)
+            mock_enable.assert_called_once_with("WiFi")
+
+        assert "WiFi" in target.platformio_libraries
+
+    def test_add_library__esp32_arduino_ignores_non_arduino_library(self, target):
+        """Test add_library doesn't enable libraries not in ARDUINO_DISABLED_LIBRARIES."""
+        target.data[const.KEY_CORE] = {
+            const.KEY_TARGET_PLATFORM: "esp32",
+            const.KEY_TARGET_FRAMEWORK: "arduino",
+        }
+
+        library = core.Library("SomeOtherLib", "1.0.0")
+
+        with patch("esphome.components.esp32._enable_arduino_library") as mock_enable:
+            target.add_library(library)
+            mock_enable.assert_not_called()
+
+        assert "SomeOtherLib" in target.platformio_libraries
+
+    def test_add_library__esp32_idf_does_not_enable_arduino_library(self, target):
+        """Test add_library doesn't auto-enable Arduino libraries on ESP32 IDF builds."""
+        target.data[const.KEY_CORE] = {
+            const.KEY_TARGET_PLATFORM: "esp32",
+            const.KEY_TARGET_FRAMEWORK: "esp-idf",
+        }
+
+        library = core.Library("WiFi", None)
+
+        with patch("esphome.components.esp32._enable_arduino_library") as mock_enable:
+            target.add_library(library)
+            mock_enable.assert_not_called()
+
+        assert "WiFi" in target.platformio_libraries
+
+    def test_add_library__esp8266_does_not_enable_arduino_library(self, target):
+        """Test add_library doesn't auto-enable Arduino libraries on ESP8266."""
+        target.data[const.KEY_CORE] = {
+            const.KEY_TARGET_PLATFORM: "esp8266",
+            const.KEY_TARGET_FRAMEWORK: "arduino",
+        }
+
+        library = core.Library("WiFi", None)
+
+        with patch("esphome.components.esp32._enable_arduino_library") as mock_enable:
+            target.add_library(library)
+            mock_enable.assert_not_called()
+
+        assert "WiFi" in target.platformio_libraries
+
+    def test_add_library__extracts_short_name_from_path(self, target):
+        """Test add_library extracts short name from library paths like owner/lib."""
+        target.data[const.KEY_CORE] = {
+            const.KEY_TARGET_PLATFORM: "esp32",
+            const.KEY_TARGET_FRAMEWORK: "arduino",
+        }
+
+        library = core.Library("arduino/Wire", None)
+
+        with patch("esphome.components.esp32._enable_arduino_library") as mock_enable:
+            target.add_library(library)
+            mock_enable.assert_called_once_with("Wire")
+
+        assert "Wire" in target.platformio_libraries