diff --git a/.clang-tidy.hash b/.clang-tidy.hash
index 777c846371..767da3f33e 100644
--- a/.clang-tidy.hash
+++ b/.clang-tidy.hash
@@ -1 +1 @@
-5eb1e5852765114ad06533220d3160b6c23f5ccefc4de41828699de5dfff5ad6
+b97e16a84153b2a4cfc51137cd6121db3c32374504b2bea55144413b3e573052
diff --git a/.github/PULL_REQUEST_TEMPLATE.md b/.github/PULL_REQUEST_TEMPLATE.md
index d1ef3bd822..965b186c31 100644
--- a/.github/PULL_REQUEST_TEMPLATE.md
+++ b/.github/PULL_REQUEST_TEMPLATE.md
@@ -6,8 +6,9 @@
 
 - [ ] Bugfix (non-breaking change which fixes an issue)
 - [ ] New feature (non-breaking change which adds functionality)
-- [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
-- [ ] Developer breaking change (an API change that could break external components)
+- [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected) — [policy](https://developers.esphome.io/contributing/code/#what-constitutes-a-c-breaking-change)
+- [ ] Developer breaking change (an API change that could break external components) — [policy](https://developers.esphome.io/contributing/code/#what-is-considered-public-c-api)
+- [ ] Undocumented C++ API change (removal or change of undocumented public methods that lambda users may depend on) — [policy](https://developers.esphome.io/contributing/code/#c-user-expectations)
 - [ ] Code quality improvements to existing code or addition of tests
 - [ ] Other
 
diff --git a/.github/scripts/auto-label-pr/constants.js b/.github/scripts/auto-label-pr/constants.js
index bd60d8c766..8c3a62cf19 100644
--- a/.github/scripts/auto-label-pr/constants.js
+++ b/.github/scripts/auto-label-pr/constants.js
@@ -27,6 +27,7 @@ module.exports = {
     'new-feature',
     'breaking-change',
     'developer-breaking-change',
+    'undocumented-api-change',
     'code-quality',
     'deprecated-component'
   ],
diff --git a/.github/scripts/auto-label-pr/detectors.js b/.github/scripts/auto-label-pr/detectors.js
index f502a85666..a45a84f219 100644
--- a/.github/scripts/auto-label-pr/detectors.js
+++ b/.github/scripts/auto-label-pr/detectors.js
@@ -238,6 +238,7 @@ async function detectPRTemplateCheckboxes(context) {
     { pattern: /- \[x\] New feature \(non-breaking change which adds functionality\)/i, label: 'new-feature' },
     { pattern: /- \[x\] Breaking change \(fix or feature that would cause existing functionality to not work as expected\)/i, label: 'breaking-change' },
     { pattern: /- \[x\] Developer breaking change \(an API change that could break external components\)/i, label: 'developer-breaking-change' },
+    { pattern: /- \[x\] Undocumented C\+\+ API change \(removal or change of undocumented public methods that lambda users may depend on\)/i, label: 'undocumented-api-change' },
     { pattern: /- \[x\] Code quality improvements to existing code or addition of tests/i, label: 'code-quality' }
   ];
 
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 07d02e0e3c..d70dd9d0e1 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -11,7 +11,7 @@ ci:
 repos:
   - repo: https://github.com/astral-sh/ruff-pre-commit
     # Ruff version.
-    rev: v0.15.2
+    rev: v0.15.3
     hooks:
       # Run the linter.
       - id: ruff
diff --git a/esphome/components/api/api.proto b/esphome/components/api/api.proto
index 4395f3a0ec..84f78c735f 100644
--- a/esphome/components/api/api.proto
+++ b/esphome/components/api/api.proto
@@ -993,6 +993,7 @@ enum ClimateAction {
   CLIMATE_ACTION_IDLE = 4;
   CLIMATE_ACTION_DRYING = 5;
   CLIMATE_ACTION_FAN = 6;
+  CLIMATE_ACTION_DEFROSTING = 7;
 }
 enum ClimatePreset {
   CLIMATE_PRESET_NONE = 0;
diff --git a/esphome/components/api/api_pb2.h b/esphome/components/api/api_pb2.h
index 547ad42a1d..9ee9c6202a 100644
--- a/esphome/components/api/api_pb2.h
+++ b/esphome/components/api/api_pb2.h
@@ -116,6 +116,7 @@ enum ClimateAction : uint32_t {
   CLIMATE_ACTION_IDLE = 4,
   CLIMATE_ACTION_DRYING = 5,
   CLIMATE_ACTION_FAN = 6,
+  CLIMATE_ACTION_DEFROSTING = 7,
 };
 enum ClimatePreset : uint32_t {
   CLIMATE_PRESET_NONE = 0,
diff --git a/esphome/components/api/api_pb2_dump.cpp b/esphome/components/api/api_pb2_dump.cpp
index 2cc96afd96..965c51bb26 100644
--- a/esphome/components/api/api_pb2_dump.cpp
+++ b/esphome/components/api/api_pb2_dump.cpp
@@ -321,6 +321,8 @@ template<> const char *proto_enum_to_string<enums::ClimateAction>(enums::Climate
       return "CLIMATE_ACTION_DRYING";
     case enums::CLIMATE_ACTION_FAN:
       return "CLIMATE_ACTION_FAN";
+    case enums::CLIMATE_ACTION_DEFROSTING:
+      return "CLIMATE_ACTION_DEFROSTING";
     default:
       return "UNKNOWN";
   }
diff --git a/esphome/components/api/list_entities.h b/esphome/components/api/list_entities.h
index 90769f9a81..7d0eb5bb13 100644
--- a/esphome/components/api/list_entities.h
+++ b/esphome/components/api/list_entities.h
@@ -15,7 +15,7 @@ class APIConnection;
     return this->client_->schedule_message_(entity, ResponseType::MESSAGE_TYPE, ResponseType::ESTIMATED_SIZE); \
   }
 
-class ListEntitiesIterator : public ComponentIterator {
+class ListEntitiesIterator final : public ComponentIterator {
  public:
   ListEntitiesIterator(APIConnection *client);
 #ifdef USE_BINARY_SENSOR
diff --git a/esphome/components/api/subscribe_state.h b/esphome/components/api/subscribe_state.h
index 6f8577ca7b..9edf0f0f0c 100644
--- a/esphome/components/api/subscribe_state.h
+++ b/esphome/components/api/subscribe_state.h
@@ -16,7 +16,7 @@ class APIConnection;
     return this->client_->send_##entity_type##_state(entity); \
   }
 
-class InitialStateIterator : public ComponentIterator {
+class InitialStateIterator final : public ComponentIterator {
  public:
   InitialStateIterator(APIConnection *client);
 #ifdef USE_BINARY_SENSOR
diff --git a/esphome/components/captive_portal/captive_index.h b/esphome/components/captive_portal/captive_index.h
index 645ebb7a2f..a81edc1900 100644
--- a/esphome/components/captive_portal/captive_index.h
+++ b/esphome/components/captive_portal/captive_index.h
@@ -6,7 +6,7 @@
 namespace esphome::captive_portal {
 
 #ifdef USE_CAPTIVE_PORTAL_GZIP
-const uint8_t INDEX_GZ[] PROGMEM = {
+constexpr uint8_t INDEX_GZ[] PROGMEM = {
     0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0x95, 0x16, 0x6b, 0x8f, 0xdb, 0x36, 0xf2, 0x7b, 0x7e,
     0x05, 0x8f, 0x49, 0xbb, 0x52, 0xb3, 0x7a, 0x7a, 0xed, 0x6c, 0x24, 0x51, 0x45, 0x9a, 0xbb, 0xa2, 0x05, 0x9a, 0x36,
     0xc0, 0x6e, 0x73, 0x1f, 0x82, 0x00, 0x4b, 0x53, 0x23, 0x8b, 0x31, 0x45, 0xea, 0x48, 0xca, 0x8f, 0x18, 0xbe, 0xdf,
@@ -86,7 +86,7 @@ const uint8_t INDEX_GZ[] PROGMEM = {
     0xfc, 0xda, 0xd1, 0xf8, 0xe9, 0xa3, 0xe1, 0xa6, 0xfb, 0x1f, 0x53, 0x58, 0x46, 0xb2, 0xf9, 0x0a, 0x00, 0x00};
 
 #else  // Brotli (default, smaller)
-const uint8_t INDEX_BR[] PROGMEM = {
+constexpr uint8_t INDEX_BR[] PROGMEM = {
     0x1b, 0xf8, 0x0a, 0x00, 0x64, 0x5a, 0xd3, 0xfa, 0xe7, 0xf3, 0x62, 0xd8, 0x06, 0x1b, 0xe9, 0x6a, 0x8a, 0x81, 0x2b,
     0xb5, 0x49, 0x14, 0x37, 0xdc, 0x9e, 0x1a, 0xcb, 0x56, 0x87, 0xfb, 0xff, 0xf7, 0x73, 0x75, 0x12, 0x0a, 0xd6, 0x48,
     0x84, 0xc6, 0x21, 0xa4, 0x6d, 0xb5, 0x71, 0xef, 0x13, 0xbe, 0x4e, 0x54, 0xf1, 0x64, 0x8f, 0x3f, 0xcc, 0x9a, 0x78,
diff --git a/esphome/components/cc1101/cc1101.cpp b/esphome/components/cc1101/cc1101.cpp
index b6973da78d..51aa88b8f7 100644
--- a/esphome/components/cc1101/cc1101.cpp
+++ b/esphome/components/cc1101/cc1101.cpp
@@ -242,6 +242,9 @@ void CC1101Component::begin_tx() {
   if (this->gdo0_pin_ != nullptr) {
     this->gdo0_pin_->pin_mode(gpio::FLAG_OUTPUT);
   }
+  // Transition through IDLE to bypass CCA (Clear Channel Assessment) which can
+  // block TX entry when strobing from RX, and to ensure FS_AUTOCAL calibration
+  this->enter_idle_();
   if (!this->enter_tx_()) {
     ESP_LOGW(TAG, "Failed to enter TX state!");
   }
@@ -252,6 +255,8 @@ void CC1101Component::begin_rx() {
   if (this->gdo0_pin_ != nullptr) {
     this->gdo0_pin_->pin_mode(gpio::FLAG_INPUT);
   }
+  // Transition through IDLE to ensure FS_AUTOCAL calibration occurs
+  this->enter_idle_();
   if (!this->enter_rx_()) {
     ESP_LOGW(TAG, "Failed to enter RX state!");
   }
diff --git a/esphome/components/climate/climate_mode.cpp b/esphome/components/climate/climate_mode.cpp
index c4dd19d503..8e443f4146 100644
--- a/esphome/components/climate/climate_mode.cpp
+++ b/esphome/components/climate/climate_mode.cpp
@@ -10,8 +10,10 @@ const LogString *climate_mode_to_string(ClimateMode mode) {
   return ClimateModeStrings::get_log_str(static_cast<uint8_t>(mode), ClimateModeStrings::LAST_INDEX);
 }
 
-// Climate action strings indexed by ClimateAction enum (0,2-6): OFF, (gap), COOLING, HEATING, IDLE, DRYING, FAN
-PROGMEM_STRING_TABLE(ClimateActionStrings, "OFF", "UNKNOWN", "COOLING", "HEATING", "IDLE", "DRYING", "FAN", "UNKNOWN");
+// Climate action strings indexed by ClimateAction enum (0,2-7): OFF, (gap), COOLING, HEATING, IDLE, DRYING, FAN,
+// DEFROSTING
+PROGMEM_STRING_TABLE(ClimateActionStrings, "OFF", "UNKNOWN", "COOLING", "HEATING", "IDLE", "DRYING", "FAN",
+                     "DEFROSTING", "UNKNOWN");
 
 const LogString *climate_action_to_string(ClimateAction action) {
   return ClimateActionStrings::get_log_str(static_cast<uint8_t>(action), ClimateActionStrings::LAST_INDEX);
diff --git a/esphome/components/climate/climate_mode.h b/esphome/components/climate/climate_mode.h
index c961c44248..014b1a9e64 100644
--- a/esphome/components/climate/climate_mode.h
+++ b/esphome/components/climate/climate_mode.h
@@ -41,6 +41,8 @@ enum ClimateAction : uint8_t {
   CLIMATE_ACTION_DRYING = 5,
   /// The climate device is in fan only mode
   CLIMATE_ACTION_FAN = 6,
+  /// The climate device is defrosting
+  CLIMATE_ACTION_DEFROSTING = 7,
 };
 
 /// NOTE: If adding values, update ClimateFanModeMask in climate_traits.h to use the new last value
diff --git a/esphome/components/esp_ldo/__init__.py b/esphome/components/esp_ldo/__init__.py
index f136dd149b..5235a9411e 100644
--- a/esphome/components/esp_ldo/__init__.py
+++ b/esphome/components/esp_ldo/__init__.py
@@ -13,22 +13,63 @@ esp_ldo_ns = cg.esphome_ns.namespace("esp_ldo")
 EspLdo = esp_ldo_ns.class_("EspLdo", cg.Component)
 AdjustAction = esp_ldo_ns.class_("AdjustAction", Action)
 
-CHANNELS = (3, 4)
+CHANNELS = (1, 2, 3, 4)
+CHANNELS_INTERNAL = (1, 2)
 CONF_ADJUSTABLE = "adjustable"
+CONF_ALLOW_INTERNAL_CHANNEL = "allow_internal_channel"
+CONF_PASSTHROUGH = "passthrough"
 
 adjusted_ids = set()
 
+
+def validate_ldo_voltage(value):
+    if isinstance(value, str) and value.lower() == CONF_PASSTHROUGH:
+        return CONF_PASSTHROUGH
+    value = cv.voltage(value)
+    if 0.5 <= value <= 2.7:
+        return value
+    raise cv.Invalid(
+        f"LDO voltage must be in range 0.5V-2.7V or 'passthrough' (bypass mode), got {value}V"
+    )
+
+
+def validate_ldo_config(config):
+    channel = config[CONF_CHANNEL]
+    allow_internal = config[CONF_ALLOW_INTERNAL_CHANNEL]
+    if allow_internal and channel not in CHANNELS_INTERNAL:
+        raise cv.Invalid(
+            f"'{CONF_ALLOW_INTERNAL_CHANNEL}' is only valid for internal channels (1, 2). "
+            f"Channel {channel} is a user-configurable channel — its usage depends on your board schematic.",
+            path=[CONF_ALLOW_INTERNAL_CHANNEL],
+        )
+    if channel in CHANNELS_INTERNAL and not allow_internal:
+        raise cv.Invalid(
+            f"LDO channel {channel} is normally used internally by the chip (flash/PSRAM). "
+            f"Set '{CONF_ALLOW_INTERNAL_CHANNEL}: true' to confirm you know what you are doing.",
+            path=[CONF_CHANNEL],
+        )
+    if config[CONF_VOLTAGE] == CONF_PASSTHROUGH and config[CONF_ADJUSTABLE]:
+        raise cv.Invalid(
+            "Passthrough mode passes the supply voltage directly to the output and does not support "
+            "runtime voltage adjustment.",
+            path=[CONF_ADJUSTABLE],
+        )
+    return config
+
+
 CONFIG_SCHEMA = cv.All(
     cv.ensure_list(
-        cv.COMPONENT_SCHEMA.extend(
-            {
-                cv.GenerateID(): cv.declare_id(EspLdo),
-                cv.Required(CONF_VOLTAGE): cv.All(
-                    cv.voltage, cv.float_range(min=0.5, max=2.7)
-                ),
-                cv.Required(CONF_CHANNEL): cv.one_of(*CHANNELS, int=True),
-                cv.Optional(CONF_ADJUSTABLE, default=False): cv.boolean,
-            }
+        cv.All(
+            cv.COMPONENT_SCHEMA.extend(
+                {
+                    cv.GenerateID(): cv.declare_id(EspLdo),
+                    cv.Required(CONF_VOLTAGE): validate_ldo_voltage,
+                    cv.Required(CONF_CHANNEL): cv.one_of(*CHANNELS, int=True),
+                    cv.Optional(CONF_ADJUSTABLE, default=False): cv.boolean,
+                    cv.Optional(CONF_ALLOW_INTERNAL_CHANNEL, default=False): cv.boolean,
+                }
+            ),
+            validate_ldo_config,
         )
     ),
     cv.only_on_esp32,
@@ -40,7 +81,11 @@ async def to_code(configs):
     for config in configs:
         var = cg.new_Pvariable(config[CONF_ID], config[CONF_CHANNEL])
         await cg.register_component(var, config)
-        cg.add(var.set_voltage(config[CONF_VOLTAGE]))
+        voltage = config[CONF_VOLTAGE]
+        if voltage == CONF_PASSTHROUGH:
+            cg.add(var.set_voltage(3300))
+        else:
+            cg.add(var.set_voltage(int(round(voltage * 1000))))
         cg.add(var.set_adjustable(config[CONF_ADJUSTABLE]))
 
 
diff --git a/esphome/components/esp_ldo/esp_ldo.cpp b/esphome/components/esp_ldo/esp_ldo.cpp
index 2eee855b46..f8ebec1903 100644
--- a/esphome/components/esp_ldo/esp_ldo.cpp
+++ b/esphome/components/esp_ldo/esp_ldo.cpp
@@ -10,32 +10,34 @@ static const char *const TAG = "esp_ldo";
 void EspLdo::setup() {
   esp_ldo_channel_config_t config{};
   config.chan_id = this->channel_;
-  config.voltage_mv = (int) (this->voltage_ * 1000.0f);
+  config.voltage_mv = this->voltage_mv_;
   config.flags.adjustable = this->adjustable_;
   auto err = esp_ldo_acquire_channel(&config, &this->handle_);
   if (err != ESP_OK) {
-    ESP_LOGE(TAG, "Failed to acquire LDO channel %d with voltage %fV", this->channel_, this->voltage_);
+    ESP_LOGE(TAG, "Failed to acquire LDO channel %d with voltage %dmV", this->channel_, this->voltage_mv_);
     this->mark_failed(LOG_STR("Failed to acquire LDO channel"));
   } else {
-    ESP_LOGD(TAG, "Acquired LDO channel %d with voltage %fV", this->channel_, this->voltage_);
+    ESP_LOGD(TAG, "Acquired LDO channel %d with voltage %dmV", this->channel_, this->voltage_mv_);
   }
 }
 void EspLdo::dump_config() {
   ESP_LOGCONFIG(TAG,
                 "ESP LDO Channel %d:\n"
-                "  Voltage: %fV\n"
+                "  Voltage: %dmV\n"
                 "  Adjustable: %s",
-                this->channel_, this->voltage_, YESNO(this->adjustable_));
+                this->channel_, this->voltage_mv_, YESNO(this->adjustable_));
 }
 
 void EspLdo::adjust_voltage(float voltage) {
   if (!std::isfinite(voltage) || voltage < 0.5f || voltage > 2.7f) {
-    ESP_LOGE(TAG, "Invalid voltage %fV for LDO channel %d", voltage, this->channel_);
+    ESP_LOGE(TAG, "Invalid voltage %fV for LDO channel %d (must be 0.5V-2.7V)", voltage, this->channel_);
     return;
   }
-  auto erro = esp_ldo_channel_adjust_voltage(this->handle_, (int) (voltage * 1000.0f));
-  if (erro != ESP_OK) {
-    ESP_LOGE(TAG, "Failed to adjust LDO channel %d to voltage %fV: %s", this->channel_, voltage, esp_err_to_name(erro));
+  int voltage_mv = (int) roundf(voltage * 1000.0f);
+  auto err = esp_ldo_channel_adjust_voltage(this->handle_, voltage_mv);
+  if (err != ESP_OK) {
+    ESP_LOGE(TAG, "Failed to adjust LDO channel %d to voltage %dmV: %s", this->channel_, voltage_mv,
+             esp_err_to_name(err));
   }
 }
 
diff --git a/esphome/components/esp_ldo/esp_ldo.h b/esphome/components/esp_ldo/esp_ldo.h
index 9edd303e16..1a20f1d08a 100644
--- a/esphome/components/esp_ldo/esp_ldo.h
+++ b/esphome/components/esp_ldo/esp_ldo.h
@@ -15,7 +15,7 @@ class EspLdo : public Component {
   void dump_config() override;
 
   void set_adjustable(bool adjustable) { this->adjustable_ = adjustable; }
-  void set_voltage(float voltage) { this->voltage_ = voltage; }
+  void set_voltage(int voltage_mv) { this->voltage_mv_ = voltage_mv; }
   void adjust_voltage(float voltage);
   float get_setup_priority() const override {
     return setup_priority::BUS;  // LDO setup should be done early
@@ -23,7 +23,7 @@ class EspLdo : public Component {
 
  protected:
   int channel_;
-  float voltage_{2.7};
+  int voltage_mv_{2700};
   bool adjustable_{false};
   esp_ldo_channel_handle_t handle_{};
 };
diff --git a/esphome/components/esphome/ota/ota_esphome.h b/esphome/components/esphome/ota/ota_esphome.h
index c9e89c82ba..53715cfe6a 100644
--- a/esphome/components/esphome/ota/ota_esphome.h
+++ b/esphome/components/esphome/ota/ota_esphome.h
@@ -12,7 +12,7 @@
 namespace esphome {
 
 /// ESPHomeOTAComponent provides a simple way to integrate Over-the-Air updates into your app using ArduinoOTA.
-class ESPHomeOTAComponent : public ota::OTAComponent {
+class ESPHomeOTAComponent final : public ota::OTAComponent {
  public:
   enum class OTAState : uint8_t {
     IDLE,
diff --git a/esphome/components/http_request/ota/ota_http_request.h b/esphome/components/http_request/ota/ota_http_request.h
index e3f1a4aa90..6d39b0d466 100644
--- a/esphome/components/http_request/ota/ota_http_request.h
+++ b/esphome/components/http_request/ota/ota_http_request.h
@@ -22,7 +22,7 @@ enum OtaHttpRequestError : uint8_t {
   OTA_CONNECTION_ERROR = 0x12,
 };
 
-class OtaHttpRequestComponent : public ota::OTAComponent, public Parented<HttpRequestComponent> {
+class OtaHttpRequestComponent final : public ota::OTAComponent, public Parented<HttpRequestComponent> {
  public:
   void dump_config() override;
   float get_setup_priority() const override { return setup_priority::AFTER_WIFI; }
diff --git a/esphome/components/libretiny/__init__.py b/esphome/components/libretiny/__init__.py
index 2291114d9a..8f99124604 100644
--- a/esphome/components/libretiny/__init__.py
+++ b/esphome/components/libretiny/__init__.py
@@ -27,6 +27,7 @@ from esphome.storage_json import StorageJSON
 
 from . import gpio  # noqa
 from .const import (
+    COMPONENT_BK72XX,
     CONF_GPIO_RECOVER,
     CONF_LOGLEVEL,
     CONF_SDK_SILENT,
@@ -453,7 +454,14 @@ async def component_to_code(config):
     cg.add_platformio_option("lib_ldf_mode", "off")
     cg.add_platformio_option("lib_compat_mode", "soft")
     # include <Arduino.h> in every file
-    cg.add_platformio_option("build_src_flags", "-include Arduino.h")
+    build_src_flags = "-include Arduino.h"
+    if FAMILY_COMPONENT[config[CONF_FAMILY]] == COMPONENT_BK72XX:
+        # LibreTiny forces -O1 globally for BK72xx because the Beken SDK
+        # has issues with higher optimization levels. However, ESPHome code
+        # works fine with -Os (used on every other platform), so override
+        # it for project source files only. GCC uses the last -O flag.
+        build_src_flags += " -Os"
+    cg.add_platformio_option("build_src_flags", build_src_flags)
     # dummy version code
     cg.add_define("USE_ARDUINO_VERSION_CODE", cg.RawExpression("VERSION_CODE(0, 0, 0)"))
     # decrease web server stack size (16k words -> 4k words)
diff --git a/esphome/components/libretiny/core.h b/esphome/components/libretiny/core.h
index 9458df1f16..f909db4f0f 100644
--- a/esphome/components/libretiny/core.h
+++ b/esphome/components/libretiny/core.h
@@ -4,8 +4,6 @@
 
 #include <Arduino.h>
 
-namespace esphome {
-namespace libretiny {}  // namespace libretiny
-}  // namespace esphome
+namespace esphome::libretiny {}  // namespace esphome::libretiny
 
 #endif  // USE_LIBRETINY
diff --git a/esphome/components/libretiny/gpio_arduino.cpp b/esphome/components/libretiny/gpio_arduino.cpp
index 0b14c77cf2..1af0dce16d 100644
--- a/esphome/components/libretiny/gpio_arduino.cpp
+++ b/esphome/components/libretiny/gpio_arduino.cpp
@@ -3,8 +3,7 @@
 #include "gpio_arduino.h"
 #include "esphome/core/log.h"
 
-namespace esphome {
-namespace libretiny {
+namespace esphome::libretiny {
 
 static const char *const TAG = "lt.gpio";
 
@@ -77,7 +76,9 @@ void ArduinoInternalGPIOPin::detach_interrupt() const {
   detachInterrupt(pin_);  // NOLINT
 }
 
-}  // namespace libretiny
+}  // namespace esphome::libretiny
+
+namespace esphome {
 
 using namespace libretiny;
 
diff --git a/esphome/components/libretiny/gpio_arduino.h b/esphome/components/libretiny/gpio_arduino.h
index 30c7c33869..5f1fa3fec7 100644
--- a/esphome/components/libretiny/gpio_arduino.h
+++ b/esphome/components/libretiny/gpio_arduino.h
@@ -3,8 +3,7 @@
 #ifdef USE_LIBRETINY
 #include "esphome/core/hal.h"
 
-namespace esphome {
-namespace libretiny {
+namespace esphome::libretiny {
 
 class ArduinoInternalGPIOPin : public InternalGPIOPin {
  public:
@@ -31,7 +30,6 @@ class ArduinoInternalGPIOPin : public InternalGPIOPin {
   gpio::Flags flags_{};
 };
 
-}  // namespace libretiny
-}  // namespace esphome
+}  // namespace esphome::libretiny
 
 #endif  // USE_LIBRETINY
diff --git a/esphome/components/libretiny/lt_component.cpp b/esphome/components/libretiny/lt_component.cpp
index ffccd0ad7a..c01661b3a6 100644
--- a/esphome/components/libretiny/lt_component.cpp
+++ b/esphome/components/libretiny/lt_component.cpp
@@ -4,8 +4,7 @@
 
 #include "esphome/core/log.h"
 
-namespace esphome {
-namespace libretiny {
+namespace esphome::libretiny {
 
 static const char *const TAG = "lt.component";
 
@@ -15,6 +14,9 @@ void LTComponent::dump_config() {
                 "  Version: %s\n"
                 "  Loglevel: %u",
                 LT_BANNER_STR + 10, LT_LOGLEVEL);
+#if defined(__OPTIMIZE_SIZE__) && __OPTIMIZE_LEVEL__ > 0 && __OPTIMIZE_LEVEL__ <= 3
+  ESP_LOGCONFIG(TAG, "  Optimization: -Os, SDK: -O" STRINGIFY_MACRO(__OPTIMIZE_LEVEL__));
+#endif
 
 #ifdef USE_TEXT_SENSOR
   if (this->version_ != nullptr) {
@@ -25,7 +27,6 @@ void LTComponent::dump_config() {
 
 float LTComponent::get_setup_priority() const { return setup_priority::LATE; }
 
-}  // namespace libretiny
-}  // namespace esphome
+}  // namespace esphome::libretiny
 
 #endif  // USE_LIBRETINY
diff --git a/esphome/components/libretiny/lt_component.h b/esphome/components/libretiny/lt_component.h
index 3d4483ab5d..896f1901e3 100644
--- a/esphome/components/libretiny/lt_component.h
+++ b/esphome/components/libretiny/lt_component.h
@@ -12,8 +12,7 @@
 #include "esphome/components/text_sensor/text_sensor.h"
 #endif
 
-namespace esphome {
-namespace libretiny {
+namespace esphome::libretiny {
 
 class LTComponent : public Component {
  public:
@@ -30,7 +29,6 @@ class LTComponent : public Component {
 #endif  // USE_TEXT_SENSOR
 };
 
-}  // namespace libretiny
-}  // namespace esphome
+}  // namespace esphome::libretiny
 
 #endif  // USE_LIBRETINY
diff --git a/esphome/components/libretiny/preferences.cpp b/esphome/components/libretiny/preferences.cpp
index 8549631e46..740c1a233a 100644
--- a/esphome/components/libretiny/preferences.cpp
+++ b/esphome/components/libretiny/preferences.cpp
@@ -8,8 +8,7 @@
 #include <cstring>
 #include <memory>
 
-namespace esphome {
-namespace libretiny {
+namespace esphome::libretiny {
 
 static const char *const TAG = "lt.preferences";
 
@@ -194,7 +193,9 @@ void setup_preferences() {
   global_preferences = &s_preferences;
 }
 
-}  // namespace libretiny
+}  // namespace esphome::libretiny
+
+namespace esphome {
 
 ESPPreferences *global_preferences;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
 
diff --git a/esphome/components/libretiny/preferences.h b/esphome/components/libretiny/preferences.h
index 8ec3cd31b1..68f377bd3e 100644
--- a/esphome/components/libretiny/preferences.h
+++ b/esphome/components/libretiny/preferences.h
@@ -2,12 +2,10 @@
 
 #ifdef USE_LIBRETINY
 
-namespace esphome {
-namespace libretiny {
+namespace esphome::libretiny {
 
 void setup_preferences();
 
-}  // namespace libretiny
-}  // namespace esphome
+}  // namespace esphome::libretiny
 
 #endif  // USE_LIBRETINY
diff --git a/esphome/components/logger/logger.h b/esphome/components/logger/logger.h
index 90722ee79c..263d12b444 100644
--- a/esphome/components/logger/logger.h
+++ b/esphome/components/logger/logger.h
@@ -141,7 +141,7 @@ enum UARTSelection : uint8_t {
  * 2. Works with ESP-IDF's pthread implementation that uses a linked list for TLS variables
  * 3. Avoids the limitations of the fixed FreeRTOS task local storage slots
  */
-class Logger : public Component {
+class Logger final : public Component {
  public:
   explicit Logger(uint32_t baud_rate);
 #ifdef USE_ESPHOME_TASK_LOG_BUFFER
@@ -481,7 +481,7 @@ class Logger : public Component {
 };
 extern Logger *global_logger;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
 
-class LoggerMessageTrigger : public Trigger<uint8_t, const char *, const char *> {
+class LoggerMessageTrigger final : public Trigger<uint8_t, const char *, const char *> {
  public:
   explicit LoggerMessageTrigger(Logger *parent, uint8_t level) : level_(level) {
     parent->add_log_callback(this,
diff --git a/esphome/components/mdns/mdns_component.h b/esphome/components/mdns/mdns_component.h
index 32f8f16ec1..13c8ccf288 100644
--- a/esphome/components/mdns/mdns_component.h
+++ b/esphome/components/mdns/mdns_component.h
@@ -40,7 +40,7 @@ struct MDNSService {
   FixedVector<MDNSTXTRecord> txt_records;
 };
 
-class MDNSComponent : public Component {
+class MDNSComponent final : public Component {
  public:
   void setup() override;
   void dump_config() override;
diff --git a/esphome/components/mipi_dsi/models/waveshare.py b/esphome/components/mipi_dsi/models/waveshare.py
index bf4f9063bb..69414065f1 100644
--- a/esphome/components/mipi_dsi/models/waveshare.py
+++ b/esphome/components/mipi_dsi/models/waveshare.py
@@ -2,7 +2,11 @@ from esphome.components.mipi import DriverChip
 import esphome.config_validation as cv
 
 # fmt: off
-DriverChip(
+
+# Source for parameters and initsequence:
+#   https://github.com/waveshareteam/Waveshare-ESP32-components/tree/master/display/lcd/esp_lcd_jd9365_10_1
+# Product page: https://www.waveshare.com/wiki/ESP32-P4-Nano-StartPage
+JD9365_10_1_DSI_TOUCH_A = DriverChip(
     "WAVESHARE-P4-NANO-10.1",
     height=1280,
     width=800,
@@ -52,6 +56,15 @@ DriverChip(
     ],
 )
 
+# Standalone display
+# Product page: https://www.waveshare.com/wiki/10.1-DSI-TOUCH-A
+JD9365_10_1_DSI_TOUCH_A.extend(
+    "WAVESHARE-10.1-DSI-TOUCH-A",
+)
+
+# Source for parameters and initsequence:
+#   https://github.com/espressif/esp-iot-solution/tree/master/components/display/lcd/esp_lcd_st7703
+# Product page: https://www.waveshare.com/wiki/ESP32-P4-86-Panel-ETH-2RO
 DriverChip(
     "WAVESHARE-P4-86-PANEL",
     height=720,
@@ -95,6 +108,9 @@ DriverChip(
     ],
 )
 
+# Source for parameters and initsequence:
+#   https://github.com/espressif/esp-iot-solution/tree/master/components/display/lcd/esp_lcd_ek79007
+# Product page: https://www.waveshare.com/wiki/ESP32-P4-WIFI6-Touch-LCD-7B
 DriverChip(
     "WAVESHARE-ESP32-P4-WIFI6-TOUCH-LCD-7B",
     height=600,
@@ -121,7 +137,10 @@ DriverChip(
     ],
 )
 
-DriverChip(
+# Source for parameters and initsequence:
+#   https://github.com/waveshareteam/Waveshare-ESP32-components/tree/master/display/lcd/esp_lcd_jd9365
+# Product page: https://www.waveshare.com/wiki/ESP32-P4-WIFI6-Touch-LCD-3.4C
+JD9365_3_4_DSI_TOUCH_C = DriverChip(
     "WAVESHARE-ESP32-P4-WIFI6-TOUCH-LCD-3.4C",
     height=800,
     width=800,
@@ -170,7 +189,16 @@ DriverChip(
     ],
 )
 
-DriverChip(
+# Standalone display
+# Product page: https://www.waveshare.com/wiki/3.4-DSI-TOUCH-C
+JD9365_3_4_DSI_TOUCH_C.extend(
+    "WAVESHARE-3.4-DSI-TOUCH-C",
+)
+
+# Source for parameters and initsequence:
+#   https://github.com/waveshareteam/Waveshare-ESP32-components/tree/master/display/lcd/esp_lcd_jd9365
+# Product page: https://www.waveshare.com/wiki/ESP32-P4-WIFI6-Touch-LCD-4C
+JD9365_4_DSI_TOUCH_C = DriverChip(
     "WAVESHARE-ESP32-P4-WIFI6-TOUCH-LCD-4C",
     height=720,
     width=720,
@@ -218,3 +246,108 @@ DriverChip(
         (0xE0, 0x00),  # select userpage
     ]
 )
+
+# Standalone display
+# Product page: https://www.waveshare.com/wiki/4-DSI-TOUCH-C
+JD9365_4_DSI_TOUCH_C.extend(
+    "WAVESHARE-4-DSI-TOUCH-C",
+)
+
+# Source for parameters and initsequence:
+#   https://github.com/waveshareteam/Waveshare-ESP32-components/tree/master/display/lcd/esp_lcd_jd9365
+# Product page: https://www.waveshare.com/wiki/8-DSI-TOUCH-A
+DriverChip(
+    "WAVESHARE-8-DSI-TOUCH-A",
+    height=1280,
+    width=800,
+    hsync_back_porch=20,
+    hsync_pulse_width=20,
+    hsync_front_porch=40,
+    vsync_back_porch=12,
+    vsync_pulse_width=4,
+    vsync_front_porch=30,
+    pclk_frequency="80MHz",
+    lane_bit_rate="1.5Gbps",
+    swap_xy=cv.UNDEFINED,
+    color_order="RGB",
+    initsequence=[
+        (0xE0, 0x00),  # select userpage
+        (0xE1, 0x93), (0xE2, 0x65), (0xE3, 0xF8),
+        (0x80, 0x01),  # Select number of lanes (2)
+        (0xE0, 0x01),  # select page 1
+        (0x00, 0x00), (0x01, 0x4E), (0x03, 0x00), (0x04, 0x65), (0x0C, 0x74), (0x17, 0x00), (0x18, 0xB7), (0x19, 0x00),
+        (0x1A, 0x00), (0x1B, 0xB7), (0x1C, 0x00), (0x24, 0xFE), (0x37, 0x19), (0x38, 0x05), (0x39, 0x00), (0x3A, 0x01),
+        (0x3B, 0x01), (0x3C, 0x70), (0x3D, 0xFF), (0x3E, 0xFF), (0x3F, 0xFF), (0x40, 0x06), (0x41, 0xA0), (0x43, 0x1E),
+        (0x44, 0x0F), (0x45, 0x28), (0x4B, 0x04), (0x55, 0x02), (0x56, 0x01), (0x57, 0xA9), (0x58, 0x0A), (0x59, 0x0A),
+        (0x5A, 0x37), (0x5B, 0x19), (0x5D, 0x78), (0x5E, 0x63), (0x5F, 0x54), (0x60, 0x49), (0x61, 0x45), (0x62, 0x38),
+        (0x63, 0x3D), (0x64, 0x28), (0x65, 0x43), (0x66, 0x41), (0x67, 0x43), (0x68, 0x62), (0x69, 0x50), (0x6A, 0x57),
+        (0x6B, 0x49), (0x6C, 0x44), (0x6D, 0x37), (0x6E, 0x23), (0x6F, 0x10), (0x70, 0x78), (0x71, 0x63), (0x72, 0x54),
+        (0x73, 0x49), (0x74, 0x45), (0x75, 0x38), (0x76, 0x3D), (0x77, 0x28), (0x78, 0x43), (0x79, 0x41), (0x7A, 0x43),
+        (0x7B, 0x62), (0x7C, 0x50), (0x7D, 0x57), (0x7E, 0x49), (0x7F, 0x44), (0x80, 0x37), (0x81, 0x23), (0x82, 0x10),
+        (0xE0, 0x02),  # select page 2
+        (0x00, 0x47), (0x01, 0x47), (0x02, 0x45), (0x03, 0x45), (0x04, 0x4B), (0x05, 0x4B), (0x06, 0x49), (0x07, 0x49),
+        (0x08, 0x41), (0x09, 0x1F), (0x0A, 0x1F), (0x0B, 0x1F), (0x0C, 0x1F), (0x0D, 0x1F), (0x0E, 0x1F), (0x0F, 0x5F),
+        (0x10, 0x5F), (0x11, 0x57), (0x12, 0x77), (0x13, 0x35), (0x14, 0x1F), (0x15, 0x1F), (0x16, 0x46), (0x17, 0x46),
+        (0x18, 0x44), (0x19, 0x44), (0x1A, 0x4A), (0x1B, 0x4A), (0x1C, 0x48), (0x1D, 0x48), (0x1E, 0x40), (0x1F, 0x1F),
+        (0x20, 0x1F), (0x21, 0x1F), (0x22, 0x1F), (0x23, 0x1F), (0x24, 0x1F), (0x25, 0x5F), (0x26, 0x5F), (0x27, 0x57),
+        (0x28, 0x77), (0x29, 0x35), (0x2A, 0x1F), (0x2B, 0x1F), (0x58, 0x40), (0x59, 0x00), (0x5A, 0x00), (0x5B, 0x10),
+        (0x5C, 0x06), (0x5D, 0x40), (0x5E, 0x01), (0x5F, 0x02), (0x60, 0x30), (0x61, 0x01), (0x62, 0x02), (0x63, 0x03),
+        (0x64, 0x6B), (0x65, 0x05), (0x66, 0x0C), (0x67, 0x73), (0x68, 0x09), (0x69, 0x03), (0x6A, 0x56), (0x6B, 0x08),
+        (0x6C, 0x00), (0x6D, 0x04), (0x6E, 0x04), (0x6F, 0x88), (0x70, 0x00), (0x71, 0x00), (0x72, 0x06), (0x73, 0x7B),
+        (0x74, 0x00), (0x75, 0xF8), (0x76, 0x00), (0x77, 0xD5), (0x78, 0x2E), (0x79, 0x12), (0x7A, 0x03), (0x7B, 0x00),
+        (0x7C, 0x00), (0x7D, 0x03), (0x7E, 0x7B),
+        (0xE0, 0x04),  # select page 4
+        (0x00, 0x0E), (0x02, 0xB3), (0x09, 0x60), (0x0E, 0x2A), (0x36, 0x59), (0x37, 0x58), (0x2B, 0x0F),
+        (0xE0, 0x00),  # select userpage
+    ]
+)
+
+# Source for parameters and initsequence:
+#   https://github.com/waveshareteam/Waveshare-ESP32-components/tree/master/display/lcd/esp_lcd_ili9881c
+# Product page: https://www.waveshare.com/wiki/7-DSI-TOUCH-A
+DriverChip(
+    "WAVESHARE-7-DSI-TOUCH-A",
+    height=1280,
+    width=720,
+    hsync_back_porch=239,
+    hsync_pulse_width=50,
+    hsync_front_porch=33,
+    vsync_back_porch=20,
+    vsync_pulse_width=30,
+    vsync_front_porch=2,
+    pclk_frequency="80MHz",
+    lane_bit_rate="1000Mbps",
+    no_transform=True,
+    color_order="RGB",
+    initsequence=[
+        (0xFF, 0x98, 0x81, 0x03),
+        (0x01, 0x00), (0x02, 0x00), (0x03, 0x73), (0x04, 0x00), (0x05, 0x00), (0x06, 0x0A), (0x07, 0x00), (0x08, 0x00),
+        (0x09, 0x61), (0x0A, 0x00), (0x0B, 0x00), (0x0C, 0x01), (0x0D, 0x00), (0x0E, 0x00), (0x0F, 0x61), (0x10, 0x61),
+        (0x11, 0x00), (0x12, 0x00), (0x13, 0x00), (0x14, 0x00), (0x15, 0x00), (0x16, 0x00), (0x17, 0x00), (0x18, 0x00),
+        (0x19, 0x00), (0x1A, 0x00), (0x1B, 0x00), (0x1C, 0x00), (0x1D, 0x00), (0x1E, 0x40), (0x1F, 0x80), (0x20, 0x06),
+        (0x21, 0x01), (0x22, 0x00), (0x23, 0x00), (0x24, 0x00), (0x25, 0x00), (0x26, 0x00), (0x27, 0x00), (0x28, 0x33),
+        (0x29, 0x03), (0x2A, 0x00), (0x2B, 0x00), (0x2C, 0x00), (0x2D, 0x00), (0x2E, 0x00), (0x2F, 0x00), (0x30, 0x00),
+        (0x31, 0x00), (0x32, 0x00), (0x33, 0x00), (0x34, 0x04), (0x35, 0x00), (0x36, 0x00), (0x37, 0x00), (0x38, 0x3C),
+        (0x39, 0x00), (0x3A, 0x00), (0x3B, 0x00), (0x3C, 0x00), (0x3D, 0x00), (0x3E, 0x00), (0x3F, 0x00), (0x40, 0x00),
+        (0x41, 0x00), (0x42, 0x00), (0x43, 0x00), (0x44, 0x00), (0x50, 0x10), (0x51, 0x32), (0x52, 0x54), (0x53, 0x76),
+        (0x54, 0x98), (0x55, 0xBA), (0x56, 0x10), (0x57, 0x32), (0x58, 0x54), (0x59, 0x76), (0x5A, 0x98), (0x5B, 0xBA),
+        (0x5C, 0xDC), (0x5D, 0xFE), (0x5E, 0x00), (0x5F, 0x0E), (0x60, 0x0F), (0x61, 0x0C), (0x62, 0x0D), (0x63, 0x06),
+        (0x64, 0x07), (0x65, 0x02), (0x66, 0x02), (0x67, 0x02), (0x68, 0x02), (0x69, 0x01), (0x6A, 0x00), (0x6B, 0x02),
+        (0x6C, 0x15), (0x6D, 0x14), (0x6E, 0x02), (0x6F, 0x02), (0x70, 0x02), (0x71, 0x02), (0x72, 0x02), (0x73, 0x02),
+        (0x74, 0x02), (0x75, 0x0E), (0x76, 0x0F), (0x77, 0x0C), (0x78, 0x0D), (0x79, 0x06), (0x7A, 0x07), (0x7B, 0x02),
+        (0x7C, 0x02), (0x7D, 0x02), (0x7E, 0x02), (0x7F, 0x01), (0x80, 0x00), (0x81, 0x02), (0x82, 0x14), (0x83, 0x15),
+        (0x84, 0x02), (0x85, 0x02), (0x86, 0x02), (0x87, 0x02), (0x88, 0x02), (0x89, 0x02), (0x8A, 0x02),
+        (0xFF, 0x98, 0x81, 0x04),
+        (0x38, 0x01), (0x39, 0x00), (0x6C, 0x15), (0x6E, 0x2A), (0x6F, 0x33), (0x3A, 0x94), (0x8D, 0x14), (0x87, 0xBA),
+        (0x26, 0x76), (0xB2, 0xD1), (0xB5, 0x06), (0x3B, 0x98),
+        (0xFF, 0x98, 0x81, 0x01),
+        (0x22, 0x0A), (0x31, 0x00), (0x53, 0x71), (0x55, 0x8F), (0x40, 0x33), (0x50, 0x96), (0x51, 0x96), (0x60, 0x23),
+        (0xA0, 0x08), (0xA1, 0x1D), (0xA2, 0x2A), (0xA3, 0x10), (0xA4, 0x15), (0xA5, 0x28), (0xA6, 0x1C), (0xA7, 0x1D),
+        (0xA8, 0x7E), (0xA9, 0x1D), (0xAA, 0x29), (0xAB, 0x6B), (0xAC, 0x1A), (0xAD, 0x18), (0xAE, 0x4B), (0xAF, 0x20),
+        (0xB0, 0x27), (0xB1, 0x50), (0xB2, 0x64), (0xB3, 0x39), (0xC0, 0x08), (0xC1, 0x1D), (0xC2, 0x2A), (0xC3, 0x10),
+        (0xC4, 0x15), (0xC5, 0x28), (0xC6, 0x1C), (0xC7, 0x1D), (0xC8, 0x7E), (0xC9, 0x1D), (0xCA, 0x29), (0xCB, 0x6B),
+        (0xCC, 0x1A), (0xCD, 0x18), (0xCE, 0x4B), (0xCF, 0x20), (0xD0, 0x27), (0xD1, 0x50), (0xD2, 0x64), (0xD3, 0x39),
+        (0xFF, 0x98, 0x81, 0x00),
+        (0x3A, 0x77), (0x36, 0x00), (0x35, 0x00), (0x35, 0x00),
+    ],
+)
diff --git a/esphome/components/mqtt/mqtt_climate.cpp b/esphome/components/mqtt/mqtt_climate.cpp
index 81b2e0e8db..443c983efe 100644
--- a/esphome/components/mqtt/mqtt_climate.cpp
+++ b/esphome/components/mqtt/mqtt_climate.cpp
@@ -20,9 +20,10 @@ static ProgmemStr climate_mode_to_mqtt_str(ClimateMode mode) {
   return ClimateMqttModeStrings::get_progmem_str(static_cast<uint8_t>(mode), ClimateMqttModeStrings::LAST_INDEX);
 }
 
-// Climate action MQTT strings indexed by ClimateAction enum (0,2-6): OFF, (gap), COOLING, HEATING, IDLE, DRYING, FAN
+// Climate action MQTT strings indexed by ClimateAction enum (0,2-7): OFF, (gap), COOLING, HEATING, IDLE, DRYING, FAN,
+// DEFROSTING
 PROGMEM_STRING_TABLE(ClimateMqttActionStrings, "off", "unknown", "cooling", "heating", "idle", "drying", "fan",
-                     "unknown");
+                     "defrosting", "unknown");
 
 static ProgmemStr climate_action_to_mqtt_str(ClimateAction action) {
   return ClimateMqttActionStrings::get_progmem_str(static_cast<uint8_t>(action), ClimateMqttActionStrings::LAST_INDEX);
diff --git a/esphome/components/ota/ota_backend_arduino_libretiny.h b/esphome/components/ota/ota_backend_arduino_libretiny.h
index 6d9b7a96d5..8f9d268eec 100644
--- a/esphome/components/ota/ota_backend_arduino_libretiny.h
+++ b/esphome/components/ota/ota_backend_arduino_libretiny.h
@@ -7,7 +7,7 @@
 namespace esphome {
 namespace ota {
 
-class ArduinoLibreTinyOTABackend : public OTABackend {
+class ArduinoLibreTinyOTABackend final : public OTABackend {
  public:
   OTAResponseTypes begin(size_t image_size) override;
   void set_update_md5(const char *md5) override;
diff --git a/esphome/components/ota/ota_backend_arduino_rp2040.h b/esphome/components/ota/ota_backend_arduino_rp2040.h
index b9e10d506c..6a708f9c57 100644
--- a/esphome/components/ota/ota_backend_arduino_rp2040.h
+++ b/esphome/components/ota/ota_backend_arduino_rp2040.h
@@ -9,7 +9,7 @@
 namespace esphome {
 namespace ota {
 
-class ArduinoRP2040OTABackend : public OTABackend {
+class ArduinoRP2040OTABackend final : public OTABackend {
  public:
   OTAResponseTypes begin(size_t image_size) override;
   void set_update_md5(const char *md5) override;
diff --git a/esphome/components/ota/ota_backend_esp8266.h b/esphome/components/ota/ota_backend_esp8266.h
index a9d6dd2ccc..52f657f006 100644
--- a/esphome/components/ota/ota_backend_esp8266.h
+++ b/esphome/components/ota/ota_backend_esp8266.h
@@ -12,7 +12,7 @@ namespace esphome::ota {
 /// OTA backend for ESP8266 using native SDK functions.
 /// This implementation bypasses the Arduino Updater library to save ~228 bytes of RAM
 /// by not having a global Update object in .bss.
-class ESP8266OTABackend : public OTABackend {
+class ESP8266OTABackend final : public OTABackend {
  public:
   OTAResponseTypes begin(size_t image_size) override;
   void set_update_md5(const char *md5) override;
diff --git a/esphome/components/ota/ota_backend_esp_idf.h b/esphome/components/ota/ota_backend_esp_idf.h
index 764010e614..7f7f6115c5 100644
--- a/esphome/components/ota/ota_backend_esp_idf.h
+++ b/esphome/components/ota/ota_backend_esp_idf.h
@@ -10,7 +10,7 @@
 namespace esphome {
 namespace ota {
 
-class IDFOTABackend : public OTABackend {
+class IDFOTABackend final : public OTABackend {
  public:
   OTAResponseTypes begin(size_t image_size) override;
   void set_update_md5(const char *md5) override;
diff --git a/esphome/components/ota/ota_backend_host.h b/esphome/components/ota/ota_backend_host.h
index ae7d0cb0b3..5a2dcfcf39 100644
--- a/esphome/components/ota/ota_backend_host.h
+++ b/esphome/components/ota/ota_backend_host.h
@@ -7,7 +7,7 @@ namespace esphome::ota {
 /// Stub OTA backend for host platform - allows compilation but does not implement OTA.
 /// All operations return error codes immediately. This enables configurations with
 /// OTA triggers to compile for host platform during development.
-class HostOTABackend : public OTABackend {
+class HostOTABackend final : public OTABackend {
  public:
   OTAResponseTypes begin(size_t image_size) override;
   void set_update_md5(const char *md5) override;
diff --git a/esphome/components/rp2040/__init__.py b/esphome/components/rp2040/__init__.py
index 3a1ea16fa3..23f12e651f 100644
--- a/esphome/components/rp2040/__init__.py
+++ b/esphome/components/rp2040/__init__.py
@@ -91,18 +91,18 @@ def _parse_platform_version(value):
 # The default/recommended arduino framework version
 #  - https://github.com/earlephilhower/arduino-pico/releases
 #  - https://api.registry.platformio.org/v3/packages/earlephilhower/tool/framework-arduinopico
-RECOMMENDED_ARDUINO_FRAMEWORK_VERSION = cv.Version(3, 9, 4)
+RECOMMENDED_ARDUINO_FRAMEWORK_VERSION = cv.Version(5, 5, 0)
 
 # The raspberrypi platform version to use for arduino frameworks
 #  - https://github.com/maxgerhardt/platform-raspberrypi/tags
-RECOMMENDED_ARDUINO_PLATFORM_VERSION = "v1.2.0-gcc12"
+RECOMMENDED_ARDUINO_PLATFORM_VERSION = "v1.4.0-gcc14-arduinopico460"
 
 
 def _arduino_check_versions(value):
     value = value.copy()
     lookups = {
-        "dev": (cv.Version(3, 9, 4), "https://github.com/earlephilhower/arduino-pico"),
-        "latest": (cv.Version(3, 9, 4), None),
+        "dev": (cv.Version(5, 5, 0), "https://github.com/earlephilhower/arduino-pico"),
+        "latest": (cv.Version(5, 5, 0), None),
         "recommended": (RECOMMENDED_ARDUINO_FRAMEWORK_VERSION, None),
     }
 
diff --git a/esphome/components/rp2040/gpio.cpp b/esphome/components/rp2040/gpio.cpp
index 2b1699f888..4b3c98104c 100644
--- a/esphome/components/rp2040/gpio.cpp
+++ b/esphome/components/rp2040/gpio.cpp
@@ -106,7 +106,7 @@ void IRAM_ATTR ISRInternalGPIOPin::pin_mode(gpio::Flags flags) {
     sio_hw->gpio_oe_set = arg->mask;
   } else if (flags & gpio::FLAG_INPUT) {
     sio_hw->gpio_oe_clr = arg->mask;
-    hw_write_masked(&padsbank0_hw->io[arg->pin],
+    hw_write_masked(&pads_bank0_hw->io[arg->pin],
                     (bool_to_bit(flags & gpio::FLAG_PULLUP) << PADS_BANK0_GPIO0_PUE_LSB) |
                         (bool_to_bit(flags & gpio::FLAG_PULLDOWN) << PADS_BANK0_GPIO0_PDE_LSB),
                     PADS_BANK0_GPIO0_PUE_BITS | PADS_BANK0_GPIO0_PDE_BITS);
diff --git a/esphome/components/safe_mode/automation.h b/esphome/components/safe_mode/automation.h
index 952ed4da33..1d82ac45f1 100644
--- a/esphome/components/safe_mode/automation.h
+++ b/esphome/components/safe_mode/automation.h
@@ -8,7 +8,7 @@
 
 namespace esphome::safe_mode {
 
-class SafeModeTrigger : public Trigger<> {
+class SafeModeTrigger final : public Trigger<> {
  public:
   explicit SafeModeTrigger(SafeModeComponent *parent) {
     parent->add_on_safe_mode_callback([this]() { trigger(); });
diff --git a/esphome/components/safe_mode/safe_mode.h b/esphome/components/safe_mode/safe_mode.h
index a4d27c15da..902b8c415d 100644
--- a/esphome/components/safe_mode/safe_mode.h
+++ b/esphome/components/safe_mode/safe_mode.h
@@ -15,7 +15,7 @@ namespace esphome::safe_mode {
 constexpr uint32_t RTC_KEY = 233825507UL;
 
 /// SafeModeComponent provides a safe way to recover from repeated boot failures
-class SafeModeComponent : public Component {
+class SafeModeComponent final : public Component {
  public:
   bool should_enter_safe_mode(uint8_t num_attempts, uint32_t enable_time, uint32_t boot_is_good_after);
 
diff --git a/esphome/components/sensor/__init__.py b/esphome/components/sensor/__init__.py
index b0e0c28bda..770c044efb 100644
--- a/esphome/components/sensor/__init__.py
+++ b/esphome/components/sensor/__init__.py
@@ -603,7 +603,7 @@ DELTA_SCHEMA = cv.Any(
 def _get_delta(value):
     if isinstance(value, str):
         assert value.endswith("%")
-        return 0.0, float(value[:-1])
+        return 0.0, float(value[:-1]) / 100.0
     return value, 0.0
 
 
diff --git a/esphome/components/socket/__init__.py b/esphome/components/socket/__init__.py
index d82f0c7aba..5f4d04eb44 100644
--- a/esphome/components/socket/__init__.py
+++ b/esphome/components/socket/__init__.py
@@ -134,6 +134,8 @@ def require_wake_loop_threadsafe() -> None:
     IMPORTANT: This is for background thread context only, NOT ISR context.
     Socket operations are not safe to call from ISR handlers.
 
+    On ESP32, FreeRTOS task notifications are used instead (no socket needed).
+
     Example:
         from esphome.components import socket
 
@@ -147,8 +149,10 @@ def require_wake_loop_threadsafe() -> None:
     ):
         CORE.data[KEY_WAKE_LOOP_THREADSAFE_REQUIRED] = True
         cg.add_define("USE_WAKE_LOOP_THREADSAFE")
-        # Consume 1 socket for the shared wake notification socket
-        consume_sockets(1, "socket.wake_loop_threadsafe", SocketType.UDP)({})
+        if not CORE.is_esp32:
+            # Only non-ESP32 platforms need a UDP socket for wake notifications.
+            # ESP32 uses FreeRTOS task notifications instead (no socket needed).
+            consume_sockets(1, "socket.wake_loop_threadsafe", SocketType.UDP)({})
 
 
 CONFIG_SCHEMA = cv.Schema(
diff --git a/esphome/components/socket/socket.h b/esphome/components/socket/socket.h
index c0098d689a..a771e2fe1a 100644
--- a/esphome/components/socket/socket.h
+++ b/esphome/components/socket/socket.h
@@ -71,7 +71,7 @@ class Socket {
   int get_fd() const { return -1; }
 #endif
 
-  /// Check if socket has data ready to read
+  /// Check if socket has data ready to read. Must only be called from the main loop thread.
   /// For select()-based sockets: non-virtual, checks Application's select() results
   /// For LWIP raw TCP sockets: virtual, checks internal buffer state
 #ifdef USE_SOCKET_SELECT_SUPPORT
diff --git a/esphome/components/sprinkler/sprinkler.cpp b/esphome/components/sprinkler/sprinkler.cpp
index 9e423c1760..d82d7baaf6 100644
--- a/esphome/components/sprinkler/sprinkler.cpp
+++ b/esphome/components/sprinkler/sprinkler.cpp
@@ -84,32 +84,30 @@ SprinklerValveOperator::SprinklerValveOperator(SprinklerValve *valve, Sprinkler
     : controller_(controller), valve_(valve) {}
 
 void SprinklerValveOperator::loop() {
+  // Use wrapping subtraction so 32-bit millis() rollover is handled correctly:
+  // (now - start) yields the true elapsed time even across the 49.7-day boundary.
   uint32_t now = App.get_loop_component_start_time();
-  if (now >= this->start_millis_) {  // dummy check
-    switch (this->state_) {
-      case STARTING:
-        if (now > (this->start_millis_ + this->start_delay_)) {
-          this->run_();  // start_delay_ has been exceeded, so ensure both valves are on and update the state
-        }
-        break;
+  switch (this->state_) {
+    case STARTING:
+      if ((now - *this->start_millis_) > this->start_delay_) {
+        this->run_();  // start_delay_ has been exceeded, so ensure both valves are on and update the state
+      }
+      break;
 
-      case ACTIVE:
-        if (now > (this->start_millis_ + this->start_delay_ + this->run_duration_)) {
-          this->stop();  // start_delay_ + run_duration_ has been exceeded, start shutting down
-        }
-        break;
+    case ACTIVE:
+      if ((now - *this->start_millis_) > (this->start_delay_ + this->run_duration_)) {
+        this->stop();  // start_delay_ + run_duration_ has been exceeded, start shutting down
+      }
+      break;
 
-      case STOPPING:
-        if (now > (this->stop_millis_ + this->stop_delay_)) {
-          this->kill_();  // stop_delay_has been exceeded, ensure all valves are off
-        }
-        break;
+    case STOPPING:
+      if ((now - *this->stop_millis_) > this->stop_delay_) {
+        this->kill_();  // stop_delay_has been exceeded, ensure all valves are off
+      }
+      break;
 
-      default:
-        break;
-    }
-  } else {         // perhaps millis() rolled over...or something else is horribly wrong!
-    this->stop();  // bail out (TODO: handle this highly unlikely situation better...)
+    default:
+      break;
   }
 }
 
@@ -124,11 +122,11 @@ void SprinklerValveOperator::set_valve(SprinklerValve *valve) {
     if (this->state_ != IDLE) {  // Only kill if not already idle
       this->kill_();             // ensure everything is off before we let go!
     }
-    this->state_ = IDLE;      // reset state
-    this->run_duration_ = 0;  // reset to ensure the valve isn't started without updating it
-    this->start_millis_ = 0;  // reset because (new) valve has not been started yet
-    this->stop_millis_ = 0;   // reset because (new) valve has not been started yet
-    this->valve_ = valve;     // finally, set the pointer to the new valve
+    this->state_ = IDLE;          // reset state
+    this->run_duration_ = 0;      // reset to ensure the valve isn't started without updating it
+    this->start_millis_.reset();  // reset because (new) valve has not been started yet
+    this->stop_millis_.reset();   // reset because (new) valve has not been started yet
+    this->valve_ = valve;         // finally, set the pointer to the new valve
   }
 }
 
@@ -162,7 +160,7 @@ void SprinklerValveOperator::start() {
   } else {
     this->run_();  // there is no start_delay_, so just start the pump and valve
   }
-  this->stop_millis_ = 0;
+  this->stop_millis_.reset();
   this->start_millis_ = millis();  // save the time the start request was made
 }
 
@@ -189,22 +187,25 @@ void SprinklerValveOperator::stop() {
 uint32_t SprinklerValveOperator::run_duration() { return this->run_duration_ / 1000; }
 
 uint32_t SprinklerValveOperator::time_remaining() {
-  if (this->start_millis_ == 0) {
+  if (!this->start_millis_.has_value()) {
     return this->run_duration();  // hasn't been started yet
   }
 
-  if (this->stop_millis_) {
-    if (this->stop_millis_ - this->start_millis_ >= this->start_delay_ + this->run_duration_) {
+  if (this->stop_millis_.has_value()) {
+    uint32_t elapsed = *this->stop_millis_ - *this->start_millis_;
+    if (elapsed >= this->start_delay_ + this->run_duration_) {
       return 0;  // valve was active for more than its configured duration, so we are done
-    } else {
-      // we're stopped; return time remaining
-      return (this->run_duration_ - (this->stop_millis_ - this->start_millis_)) / 1000;
     }
+    if (elapsed <= this->start_delay_) {
+      return this->run_duration_ / 1000;  // stopped during start delay, full run duration remains
+    }
+    return (this->run_duration_ - (elapsed - this->start_delay_)) / 1000;
   }
 
-  auto completed_millis = this->start_millis_ + this->start_delay_ + this->run_duration_;
-  if (completed_millis > millis()) {
-    return (completed_millis - millis()) / 1000;  // running now
+  uint32_t elapsed = millis() - *this->start_millis_;
+  uint32_t total_duration = this->start_delay_ + this->run_duration_;
+  if (elapsed < total_duration) {
+    return (total_duration - elapsed) / 1000;  // running now
   }
   return 0;  // run completed
 }
@@ -593,7 +594,7 @@ void Sprinkler::set_repeat(optional<uint32_t> repeat) {
   if (this->repeat_number_ == nullptr) {
     return;
   }
-  if (this->repeat_number_->state == repeat.value()) {
+  if (this->repeat_number_->state == repeat.value_or(0)) {
     return;
   }
   auto call = this->repeat_number_->make_call();
@@ -793,7 +794,7 @@ void Sprinkler::start_single_valve(const optional<size_t> valve_number, optional
 void Sprinkler::queue_valve(optional<size_t> valve_number, optional<uint32_t> run_duration) {
   if (valve_number.has_value()) {
     if (this->is_a_valid_valve(valve_number.value()) && (this->queued_valves_.size() < this->max_queue_size_)) {
-      SprinklerQueueItem item{valve_number.value(), run_duration.value()};
+      SprinklerQueueItem item{valve_number.value(), run_duration.value_or(0)};
       this->queued_valves_.insert(this->queued_valves_.begin(), item);
       ESP_LOGD(TAG, "Valve %zu placed into queue with run duration of %" PRIu32 " seconds", valve_number.value_or(0),
                run_duration.value_or(0));
@@ -1080,7 +1081,7 @@ uint32_t Sprinkler::total_cycle_time_enabled_incomplete_valves() {
     }
   }
 
-  if (incomplete_valve_count >= enabled_valve_count) {
+  if (incomplete_valve_count > 0 && incomplete_valve_count >= enabled_valve_count) {
     incomplete_valve_count--;
   }
   if (incomplete_valve_count) {
diff --git a/esphome/components/sprinkler/sprinkler.h b/esphome/components/sprinkler/sprinkler.h
index a3cdef5b1a..2598a5606a 100644
--- a/esphome/components/sprinkler/sprinkler.h
+++ b/esphome/components/sprinkler/sprinkler.h
@@ -141,8 +141,8 @@ class SprinklerValveOperator {
   uint32_t start_delay_{0};
   uint32_t stop_delay_{0};
   uint32_t run_duration_{0};
-  uint64_t start_millis_{0};
-  uint64_t stop_millis_{0};
+  optional<uint32_t> start_millis_{};
+  optional<uint32_t> stop_millis_{};
   Sprinkler *controller_{nullptr};
   SprinklerValve *valve_{nullptr};
   SprinklerState state_{IDLE};
diff --git a/esphome/components/time/posix_tz.cpp b/esphome/components/time/posix_tz.cpp
new file mode 100644
index 0000000000..4d1f0c74c2
--- /dev/null
+++ b/esphome/components/time/posix_tz.cpp
@@ -0,0 +1,488 @@
+#include "esphome/core/defines.h"
+
+#ifdef USE_TIME_TIMEZONE
+
+#include "posix_tz.h"
+#include <cctype>
+
+namespace esphome::time {
+
+// Global timezone - set once at startup, rarely changes
+// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables) - intentional mutable state
+static ParsedTimezone global_tz_{};
+
+void set_global_tz(const ParsedTimezone &tz) { global_tz_ = tz; }
+
+const ParsedTimezone &get_global_tz() { return global_tz_; }
+
+namespace internal {
+
+// Remove before 2026.9.0: parse_uint, skip_tz_name, parse_offset, parse_dst_rule,
+// and parse_transition_time are only used by parse_posix_tz() (bridge code).
+static uint32_t parse_uint(const char *&p) {
+  uint32_t value = 0;
+  while (std::isdigit(static_cast<unsigned char>(*p))) {
+    value = value * 10 + (*p - '0');
+    p++;
+  }
+  return value;
+}
+
+bool is_leap_year(int year) { return (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0); }
+
+// Get days in year (avoids duplicate is_leap_year calls)
+static inline int days_in_year(int year) { return is_leap_year(year) ? 366 : 365; }
+
+// Convert days since epoch to year, updating days to remainder
+static int __attribute__((noinline)) days_to_year(int64_t &days) {
+  int year = 1970;
+  int diy;
+  while (days >= (diy = days_in_year(year)) && year < 2200) {
+    days -= diy;
+    year++;
+  }
+  while (days < 0 && year > 1900) {
+    year--;
+    days += days_in_year(year);
+  }
+  return year;
+}
+
+// Extract just the year from a UTC epoch
+static int epoch_to_year(time_t epoch) {
+  int64_t days = epoch / 86400;
+  if (epoch < 0 && epoch % 86400 != 0)
+    days--;
+  return days_to_year(days);
+}
+
+int days_in_month(int year, int month) {
+  switch (month) {
+    case 2:
+      return is_leap_year(year) ? 29 : 28;
+    case 4:
+    case 6:
+    case 9:
+    case 11:
+      return 30;
+    default:
+      return 31;
+  }
+}
+
+// Zeller-like algorithm for day of week (0 = Sunday)
+int __attribute__((noinline)) day_of_week(int year, int month, int day) {
+  // Adjust for January/February
+  if (month < 3) {
+    month += 12;
+    year--;
+  }
+  int k = year % 100;
+  int j = year / 100;
+  int h = (day + (13 * (month + 1)) / 5 + k + k / 4 + j / 4 - 2 * j) % 7;
+  // Convert from Zeller (0=Sat) to standard (0=Sun)
+  return ((h + 6) % 7);
+}
+
+void __attribute__((noinline)) epoch_to_tm_utc(time_t epoch, struct tm *out_tm) {
+  // Days since epoch
+  int64_t days = epoch / 86400;
+  int32_t remaining_secs = epoch % 86400;
+  if (remaining_secs < 0) {
+    days--;
+    remaining_secs += 86400;
+  }
+
+  out_tm->tm_sec = remaining_secs % 60;
+  remaining_secs /= 60;
+  out_tm->tm_min = remaining_secs % 60;
+  out_tm->tm_hour = remaining_secs / 60;
+
+  // Day of week (Jan 1, 1970 was Thursday = 4)
+  out_tm->tm_wday = static_cast<int>((days + 4) % 7);
+  if (out_tm->tm_wday < 0)
+    out_tm->tm_wday += 7;
+
+  // Calculate year (updates days to day-of-year)
+  int year = days_to_year(days);
+  out_tm->tm_year = year - 1900;
+  out_tm->tm_yday = static_cast<int>(days);
+
+  // Calculate month and day
+  int month = 1;
+  int dim;
+  while (days >= (dim = days_in_month(year, month))) {
+    days -= dim;
+    month++;
+  }
+
+  out_tm->tm_mon = month - 1;
+  out_tm->tm_mday = static_cast<int>(days) + 1;
+  out_tm->tm_isdst = 0;
+}
+
+bool skip_tz_name(const char *&p) {
+  if (*p == '<') {
+    // Angle-bracket quoted name: <+07>, <-03>, <AEST>
+    p++;  // skip '<'
+    while (*p && *p != '>') {
+      p++;
+    }
+    if (*p == '>') {
+      p++;  // skip '>'
+      return true;
+    }
+    return false;  // Unterminated
+  }
+
+  // Standard name: 3+ letters
+  const char *start = p;
+  while (*p && std::isalpha(static_cast<unsigned char>(*p))) {
+    p++;
+  }
+  return (p - start) >= 3;
+}
+
+int32_t __attribute__((noinline)) parse_offset(const char *&p) {
+  int sign = 1;
+  if (*p == '-') {
+    sign = -1;
+    p++;
+  } else if (*p == '+') {
+    p++;
+  }
+
+  int hours = parse_uint(p);
+  int minutes = 0;
+  int seconds = 0;
+
+  if (*p == ':') {
+    p++;
+    minutes = parse_uint(p);
+    if (*p == ':') {
+      p++;
+      seconds = parse_uint(p);
+    }
+  }
+
+  return sign * (hours * 3600 + minutes * 60 + seconds);
+}
+
+// Helper to parse the optional /time suffix (reuses parse_offset logic)
+static void parse_transition_time(const char *&p, DSTRule &rule) {
+  rule.time_seconds = 2 * 3600;  // Default 02:00
+  if (*p == '/') {
+    p++;
+    rule.time_seconds = parse_offset(p);
+  }
+}
+
+void __attribute__((noinline)) julian_to_month_day(int julian_day, int &out_month, int &out_day) {
+  // J format: day 1-365, Feb 29 is NOT counted even in leap years
+  // So day 60 is always March 1
+  // Iterate forward through months (no array needed)
+  int remaining = julian_day;
+  out_month = 1;
+  while (out_month <= 12) {
+    // Days in month for non-leap year (J format ignores leap years)
+    int dim = days_in_month(2001, out_month);  // 2001 is non-leap year
+    if (remaining <= dim) {
+      out_day = remaining;
+      return;
+    }
+    remaining -= dim;
+    out_month++;
+  }
+  out_day = remaining;
+}
+
+void __attribute__((noinline)) day_of_year_to_month_day(int day_of_year, int year, int &out_month, int &out_day) {
+  // Plain format: day 0-365, Feb 29 IS counted in leap years
+  // Day 0 = Jan 1
+  int remaining = day_of_year;
+  out_month = 1;
+
+  while (out_month <= 12) {
+    int days_this_month = days_in_month(year, out_month);
+    if (remaining < days_this_month) {
+      out_day = remaining + 1;
+      return;
+    }
+    remaining -= days_this_month;
+    out_month++;
+  }
+
+  // Shouldn't reach here with valid input
+  out_month = 12;
+  out_day = 31;
+}
+
+bool parse_dst_rule(const char *&p, DSTRule &rule) {
+  rule = {};  // Zero initialize
+
+  if (*p == 'M' || *p == 'm') {
+    // M format: Mm.w.d (month.week.day)
+    rule.type = DSTRuleType::MONTH_WEEK_DAY;
+    p++;
+
+    rule.month = parse_uint(p);
+    if (rule.month < 1 || rule.month > 12)
+      return false;
+
+    if (*p++ != '.')
+      return false;
+
+    rule.week = parse_uint(p);
+    if (rule.week < 1 || rule.week > 5)
+      return false;
+
+    if (*p++ != '.')
+      return false;
+
+    rule.day_of_week = parse_uint(p);
+    if (rule.day_of_week > 6)
+      return false;
+
+  } else if (*p == 'J' || *p == 'j') {
+    // J format: Jn (Julian day 1-365, not counting Feb 29)
+    rule.type = DSTRuleType::JULIAN_NO_LEAP;
+    p++;
+
+    rule.day = parse_uint(p);
+    if (rule.day < 1 || rule.day > 365)
+      return false;
+
+  } else if (std::isdigit(static_cast<unsigned char>(*p))) {
+    // Plain number format: n (day 0-365, counting Feb 29)
+    rule.type = DSTRuleType::DAY_OF_YEAR;
+
+    rule.day = parse_uint(p);
+    if (rule.day > 365)
+      return false;
+
+  } else {
+    return false;
+  }
+
+  // Parse optional /time suffix
+  parse_transition_time(p, rule);
+
+  return true;
+}
+
+// Calculate days from Jan 1 of given year to given month/day
+static int __attribute__((noinline)) days_from_year_start(int year, int month, int day) {
+  int days = day - 1;
+  for (int m = 1; m < month; m++) {
+    days += days_in_month(year, m);
+  }
+  return days;
+}
+
+// Calculate days from epoch to Jan 1 of given year (for DST transition calculations)
+// Only supports years >= 1970. Timezone is either compiled in from YAML or set by
+// Home Assistant, so pre-1970 dates are not a concern.
+static int64_t __attribute__((noinline)) days_to_year_start(int year) {
+  int64_t days = 0;
+  for (int y = 1970; y < year; y++) {
+    days += days_in_year(y);
+  }
+  return days;
+}
+
+time_t __attribute__((noinline)) calculate_dst_transition(int year, const DSTRule &rule, int32_t base_offset_seconds) {
+  int month, day;
+
+  switch (rule.type) {
+    case DSTRuleType::MONTH_WEEK_DAY: {
+      // Find the nth occurrence of day_of_week in the given month
+      int first_dow = day_of_week(year, rule.month, 1);
+
+      // Days until first occurrence of target day
+      int days_until_first = (rule.day_of_week - first_dow + 7) % 7;
+      int first_occurrence = 1 + days_until_first;
+
+      if (rule.week == 5) {
+        // "Last" occurrence - find the last one in the month
+        int dim = days_in_month(year, rule.month);
+        day = first_occurrence;
+        while (day + 7 <= dim) {
+          day += 7;
+        }
+      } else {
+        // nth occurrence
+        day = first_occurrence + (rule.week - 1) * 7;
+      }
+      month = rule.month;
+      break;
+    }
+
+    case DSTRuleType::JULIAN_NO_LEAP:
+      // J format: day 1-365, Feb 29 not counted
+      julian_to_month_day(rule.day, month, day);
+      break;
+
+    case DSTRuleType::DAY_OF_YEAR:
+      // Plain format: day 0-365, Feb 29 counted
+      day_of_year_to_month_day(rule.day, year, month, day);
+      break;
+
+    case DSTRuleType::NONE:
+      // Should never be called with NONE, but handle it gracefully
+      month = 1;
+      day = 1;
+      break;
+  }
+
+  // Calculate days from epoch to this date
+  int64_t days = days_to_year_start(year) + days_from_year_start(year, month, day);
+
+  // Convert to epoch and add transition time and base offset
+  return days * 86400 + rule.time_seconds + base_offset_seconds;
+}
+
+}  // namespace internal
+
+bool __attribute__((noinline)) is_in_dst(time_t utc_epoch, const ParsedTimezone &tz) {
+  if (!tz.has_dst()) {
+    return false;
+  }
+
+  int year = internal::epoch_to_year(utc_epoch);
+
+  // Calculate DST start and end for this year
+  // DST start transition happens in standard time
+  time_t dst_start = internal::calculate_dst_transition(year, tz.dst_start, tz.std_offset_seconds);
+  // DST end transition happens in daylight time
+  time_t dst_end = internal::calculate_dst_transition(year, tz.dst_end, tz.dst_offset_seconds);
+
+  if (dst_start < dst_end) {
+    // Northern hemisphere: DST is between start and end
+    return (utc_epoch >= dst_start && utc_epoch < dst_end);
+  } else {
+    // Southern hemisphere: DST is outside the range (wraps around year)
+    return (utc_epoch >= dst_start || utc_epoch < dst_end);
+  }
+}
+
+// Remove before 2026.9.0: This parser is bridge code for backward compatibility with
+// older Home Assistant clients that send the timezone as a POSIX TZ string instead of
+// the pre-parsed ParsedTimezone protobuf struct. Once all clients send the struct
+// directly, this function and the parsing helpers above (skip_tz_name, parse_offset,
+// parse_dst_rule, parse_transition_time) can be removed.
+// See https://github.com/esphome/backlog/issues/91
+bool parse_posix_tz(const char *tz_string, ParsedTimezone &result) {
+  if (!tz_string || !*tz_string) {
+    return false;
+  }
+
+  const char *p = tz_string;
+
+  // Initialize result (dst_start/dst_end default to type=NONE, so has_dst() returns false)
+  result.std_offset_seconds = 0;
+  result.dst_offset_seconds = 0;
+  result.dst_start = {};
+  result.dst_end = {};
+
+  // Skip standard timezone name
+  if (!internal::skip_tz_name(p)) {
+    return false;
+  }
+
+  // Parse standard offset (required)
+  if (!*p || (!std::isdigit(static_cast<unsigned char>(*p)) && *p != '+' && *p != '-')) {
+    return false;
+  }
+  result.std_offset_seconds = internal::parse_offset(p);
+
+  // Check for DST name
+  if (!*p) {
+    return true;  // No DST
+  }
+
+  // If next char is comma, there's no DST name but there are rules (invalid)
+  if (*p == ',') {
+    return false;
+  }
+
+  // Check if there's something that looks like a DST name start
+  // (letter or angle bracket). If not, treat as trailing garbage and return success.
+  if (!std::isalpha(static_cast<unsigned char>(*p)) && *p != '<') {
+    return true;  // No DST, trailing characters ignored
+  }
+
+  if (!internal::skip_tz_name(p)) {
+    return false;  // Invalid DST name (started but malformed)
+  }
+
+  // Optional DST offset (default is std - 1 hour)
+  if (*p && *p != ',' && (std::isdigit(static_cast<unsigned char>(*p)) || *p == '+' || *p == '-')) {
+    result.dst_offset_seconds = internal::parse_offset(p);
+  } else {
+    result.dst_offset_seconds = result.std_offset_seconds - 3600;
+  }
+
+  // Parse DST rules (required when DST name is present)
+  if (*p != ',') {
+    // DST name without rules - treat as no DST since we can't determine transitions
+    return true;
+  }
+
+  p++;
+  if (!internal::parse_dst_rule(p, result.dst_start)) {
+    return false;
+  }
+
+  // Second rule is required per POSIX
+  if (*p != ',') {
+    return false;
+  }
+  p++;
+  // has_dst() now returns true since dst_start.type was set by parse_dst_rule
+  return internal::parse_dst_rule(p, result.dst_end);
+}
+
+bool epoch_to_local_tm(time_t utc_epoch, const ParsedTimezone &tz, struct tm *out_tm) {
+  if (!out_tm) {
+    return false;
+  }
+
+  // Determine DST status once (avoids duplicate is_in_dst calculation)
+  bool in_dst = is_in_dst(utc_epoch, tz);
+  int32_t offset = in_dst ? tz.dst_offset_seconds : tz.std_offset_seconds;
+
+  // Apply offset (POSIX offset is positive west, so subtract to get local)
+  time_t local_epoch = utc_epoch - offset;
+
+  internal::epoch_to_tm_utc(local_epoch, out_tm);
+  out_tm->tm_isdst = in_dst ? 1 : 0;
+
+  return true;
+}
+
+}  // namespace esphome::time
+
+#ifndef USE_HOST
+// Override libc's localtime functions to use our timezone on embedded platforms.
+// This allows user lambdas calling ::localtime() to get correct local time
+// without needing the TZ environment variable (which pulls in scanf bloat).
+// On host, we use the normal TZ mechanism since there's no memory constraint.
+
+// Thread-safe version
+extern "C" struct tm *localtime_r(const time_t *timer, struct tm *result) {
+  if (timer == nullptr || result == nullptr) {
+    return nullptr;
+  }
+  esphome::time::epoch_to_local_tm(*timer, esphome::time::get_global_tz(), result);
+  return result;
+}
+
+// Non-thread-safe version (uses static buffer, standard libc behavior)
+extern "C" struct tm *localtime(const time_t *timer) {
+  // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
+  static struct tm localtime_buf;
+  return localtime_r(timer, &localtime_buf);
+}
+#endif  // !USE_HOST
+
+#endif  // USE_TIME_TIMEZONE
diff --git a/esphome/components/time/posix_tz.h b/esphome/components/time/posix_tz.h
new file mode 100644
index 0000000000..c71ba15cd1
--- /dev/null
+++ b/esphome/components/time/posix_tz.h
@@ -0,0 +1,144 @@
+#pragma once
+
+#ifdef USE_TIME_TIMEZONE
+
+#include <cstdint>
+#include <ctime>
+
+namespace esphome::time {
+
+/// Type of DST transition rule
+enum class DSTRuleType : uint8_t {
+  NONE = 0,        ///< No DST rule (used to indicate no DST)
+  MONTH_WEEK_DAY,  ///< M format: Mm.w.d (e.g., M3.2.0 = 2nd Sunday of March)
+  JULIAN_NO_LEAP,  ///< J format: Jn (day 1-365, Feb 29 not counted)
+  DAY_OF_YEAR,     ///< Plain number: n (day 0-365, Feb 29 counted in leap years)
+};
+
+/// Rule for DST transition (packed for 32-bit: 12 bytes)
+struct DSTRule {
+  int32_t time_seconds;  ///< Seconds after midnight (default 7200 = 2:00 AM)
+  uint16_t day;          ///< Day of year (for JULIAN_NO_LEAP and DAY_OF_YEAR)
+  DSTRuleType type;      ///< Type of rule
+  uint8_t month;         ///< Month 1-12 (for MONTH_WEEK_DAY)
+  uint8_t week;          ///< Week 1-5, 5 = last (for MONTH_WEEK_DAY)
+  uint8_t day_of_week;   ///< Day 0-6, 0 = Sunday (for MONTH_WEEK_DAY)
+};
+
+/// Parsed POSIX timezone information (packed for 32-bit: 32 bytes)
+struct ParsedTimezone {
+  int32_t std_offset_seconds;  ///< Standard time offset from UTC in seconds (positive = west)
+  int32_t dst_offset_seconds;  ///< DST offset from UTC in seconds
+  DSTRule dst_start;           ///< When DST starts
+  DSTRule dst_end;             ///< When DST ends
+
+  /// Check if this timezone has DST rules
+  bool has_dst() const { return this->dst_start.type != DSTRuleType::NONE; }
+};
+
+/// Parse a POSIX TZ string into a ParsedTimezone struct.
+///
+/// @deprecated Remove before 2026.9.0 (bridge code for backward compatibility).
+/// This parser only exists so that older Home Assistant clients that send the timezone
+/// as a string (instead of the pre-parsed ParsedTimezone protobuf struct) can still
+/// set the timezone on the device. Once all clients are updated to send the struct
+/// directly, this function and all internal parsing helpers will be removed.
+/// See https://github.com/esphome/backlog/issues/91
+///
+/// Supports formats like:
+///   - "EST5" (simple offset, no DST)
+///   - "EST5EDT,M3.2.0,M11.1.0" (with DST, M-format rules)
+///   - "CST6CDT,M3.2.0/2,M11.1.0/2" (with transition times)
+///   - "<+07>-7" (angle-bracket notation for special names)
+///   - "IST-5:30" (half-hour offsets)
+///   - "EST5EDT,J60,J300" (J-format: Julian day without leap day)
+///   - "EST5EDT,60,300" (plain day number: day of year with leap day)
+/// @param tz_string The POSIX TZ string to parse
+/// @param result Output: the parsed timezone data
+/// @return true if parsing succeeded, false on error
+bool parse_posix_tz(const char *tz_string, ParsedTimezone &result);
+
+/// Convert a UTC epoch to local time using the parsed timezone.
+/// This replaces libc's localtime() to avoid scanf dependency.
+/// @param utc_epoch Unix timestamp in UTC
+/// @param tz The parsed timezone
+/// @param[out] out_tm Output tm struct with local time
+/// @return true on success
+bool epoch_to_local_tm(time_t utc_epoch, const ParsedTimezone &tz, struct tm *out_tm);
+
+/// Set the global timezone used by epoch_to_local_tm() when called without a timezone.
+/// This is called by RealTimeClock::apply_timezone_() to enable ESPTime::from_epoch_local()
+/// to work without libc's localtime().
+void set_global_tz(const ParsedTimezone &tz);
+
+/// Get the global timezone.
+const ParsedTimezone &get_global_tz();
+
+/// Check if a given UTC epoch falls within DST for the parsed timezone.
+/// @param utc_epoch Unix timestamp in UTC
+/// @param tz The parsed timezone
+/// @return true if DST is in effect at the given time
+bool is_in_dst(time_t utc_epoch, const ParsedTimezone &tz);
+
+// Internal helper functions exposed for testing.
+// Remove before 2026.9.0: skip_tz_name, parse_offset, parse_dst_rule are only
+// used by parse_posix_tz() which is bridge code for backward compatibility.
+// The remaining helpers (epoch_to_tm_utc, day_of_week, days_in_month, etc.)
+// are used by the conversion functions and will stay.
+
+namespace internal {
+
+/// Skip a timezone name (letters or <...> quoted format)
+/// @param p Pointer to current position, updated on return
+/// @return true if a valid name was found
+bool skip_tz_name(const char *&p);
+
+/// Parse an offset in format [-]hh[:mm[:ss]]
+/// @param p Pointer to current position, updated on return
+/// @return Offset in seconds
+int32_t parse_offset(const char *&p);
+
+/// Parse a DST rule in format Mm.w.d[/time], Jn[/time], or n[/time]
+/// @param p Pointer to current position, updated on return
+/// @param rule Output: the parsed rule
+/// @return true if parsing succeeded
+bool parse_dst_rule(const char *&p, DSTRule &rule);
+
+/// Convert Julian day (J format, 1-365 not counting Feb 29) to month/day
+/// @param julian_day Day number 1-365
+/// @param[out] month Output: month 1-12
+/// @param[out] day Output: day of month
+void julian_to_month_day(int julian_day, int &month, int &day);
+
+/// Convert day of year (plain format, 0-365 counting Feb 29) to month/day
+/// @param day_of_year Day number 0-365
+/// @param year The year (for leap year calculation)
+/// @param[out] month Output: month 1-12
+/// @param[out] day Output: day of month
+void day_of_year_to_month_day(int day_of_year, int year, int &month, int &day);
+
+/// Calculate day of week for any date (0 = Sunday)
+/// Uses a simplified algorithm that works for years 1970-2099
+int day_of_week(int year, int month, int day);
+
+/// Get the number of days in a month
+int days_in_month(int year, int month);
+
+/// Check if a year is a leap year
+bool is_leap_year(int year);
+
+/// Convert epoch to year/month/day/hour/min/sec (UTC)
+void epoch_to_tm_utc(time_t epoch, struct tm *out_tm);
+
+/// Calculate the epoch timestamp for a DST transition in a given year.
+/// @param year The year (e.g., 2026)
+/// @param rule The DST rule (month, week, day_of_week, time)
+/// @param base_offset_seconds The timezone offset to apply (std or dst depending on context)
+/// @return Unix epoch timestamp of the transition
+time_t calculate_dst_transition(int year, const DSTRule &rule, int32_t base_offset_seconds);
+
+}  // namespace internal
+
+}  // namespace esphome::time
+
+#endif  // USE_TIME_TIMEZONE
diff --git a/esphome/components/time/real_time_clock.cpp b/esphome/components/time/real_time_clock.cpp
index 8a78186178..2e758ad8e7 100644
--- a/esphome/components/time/real_time_clock.cpp
+++ b/esphome/components/time/real_time_clock.cpp
@@ -14,8 +14,8 @@
 #include <sys/time.h>
 #endif
 #include <cerrno>
-
 #include <cinttypes>
+#include <cstdlib>
 
 namespace esphome::time {
 
@@ -23,9 +23,33 @@ static const char *const TAG = "time";
 
 RealTimeClock::RealTimeClock() = default;
 
+ESPTime __attribute__((noinline)) RealTimeClock::now() {
+#ifdef USE_TIME_TIMEZONE
+  time_t epoch = this->timestamp_now();
+  struct tm local_tm;
+  if (epoch_to_local_tm(epoch, get_global_tz(), &local_tm)) {
+    return ESPTime::from_c_tm(&local_tm, epoch);
+  }
+  // Fallback to UTC if parsing failed
+  return ESPTime::from_epoch_utc(epoch);
+#else
+  return ESPTime::from_epoch_local(this->timestamp_now());
+#endif
+}
+
 void RealTimeClock::dump_config() {
 #ifdef USE_TIME_TIMEZONE
-  ESP_LOGCONFIG(TAG, "Timezone: '%s'", this->timezone_.c_str());
+  const auto &tz = get_global_tz();
+  // POSIX offset is positive west, negate for conventional UTC+X display
+  int std_h = -tz.std_offset_seconds / 3600;
+  int std_m = (std::abs(tz.std_offset_seconds) % 3600) / 60;
+  if (tz.has_dst()) {
+    int dst_h = -tz.dst_offset_seconds / 3600;
+    int dst_m = (std::abs(tz.dst_offset_seconds) % 3600) / 60;
+    ESP_LOGCONFIG(TAG, "Timezone: UTC%+d:%02d (DST UTC%+d:%02d)", std_h, std_m, dst_h, dst_m);
+  } else {
+    ESP_LOGCONFIG(TAG, "Timezone: UTC%+d:%02d", std_h, std_m);
+  }
 #endif
   auto time = this->now();
   ESP_LOGCONFIG(TAG, "Current time: %04d-%02d-%02d %02d:%02d:%02d", time.year, time.month, time.day_of_month, time.hour,
@@ -72,11 +96,6 @@ void RealTimeClock::synchronize_epoch_(uint32_t epoch) {
     ret = settimeofday(&timev, nullptr);
   }
 
-#ifdef USE_TIME_TIMEZONE
-  // Move timezone back to local timezone.
-  this->apply_timezone_();
-#endif
-
   if (ret != 0) {
     ESP_LOGW(TAG, "setimeofday() failed with code %d", ret);
   }
@@ -89,9 +108,33 @@ void RealTimeClock::synchronize_epoch_(uint32_t epoch) {
 }
 
 #ifdef USE_TIME_TIMEZONE
-void RealTimeClock::apply_timezone_() {
-  setenv("TZ", this->timezone_.c_str(), 1);
+void RealTimeClock::apply_timezone_(const char *tz) {
+  ParsedTimezone parsed{};
+
+  // Handle null or empty input - use UTC
+  if (tz == nullptr || *tz == '\0') {
+    // Skip if already UTC
+    if (!get_global_tz().has_dst() && get_global_tz().std_offset_seconds == 0) {
+      return;
+    }
+    set_global_tz(parsed);
+    return;
+  }
+
+#ifdef USE_HOST
+  // On host platform, also set TZ environment variable for libc compatibility
+  setenv("TZ", tz, 1);
   tzset();
+#endif
+
+  // Parse the POSIX TZ string using our custom parser
+  if (!parse_posix_tz(tz, parsed)) {
+    ESP_LOGW(TAG, "Failed to parse timezone: %s", tz);
+    return;
+  }
+
+  // Set global timezone for all time conversions
+  set_global_tz(parsed);
 }
 #endif
 
diff --git a/esphome/components/time/real_time_clock.h b/esphome/components/time/real_time_clock.h
index 19aa1a4f4a..f9de5f5614 100644
--- a/esphome/components/time/real_time_clock.h
+++ b/esphome/components/time/real_time_clock.h
@@ -6,6 +6,9 @@
 #include "esphome/core/component.h"
 #include "esphome/core/helpers.h"
 #include "esphome/core/time.h"
+#ifdef USE_TIME_TIMEZONE
+#include "posix_tz.h"
+#endif
 
 namespace esphome::time {
 
@@ -20,26 +23,31 @@ class RealTimeClock : public PollingComponent {
   explicit RealTimeClock();
 
 #ifdef USE_TIME_TIMEZONE
-  /// Set the time zone.
-  void set_timezone(const std::string &tz) {
-    this->timezone_ = tz;
-    this->apply_timezone_();
-  }
+  /// Set the time zone from a POSIX TZ string.
+  void set_timezone(const char *tz) { this->apply_timezone_(tz); }
 
-  /// Set the time zone from raw buffer, only if it differs from the current one.
+  /// Set the time zone from a character buffer with known length.
+  /// The buffer does not need to be null-terminated.
   void set_timezone(const char *tz, size_t len) {
-    if (this->timezone_.length() != len || memcmp(this->timezone_.c_str(), tz, len) != 0) {
-      this->timezone_.assign(tz, len);
-      this->apply_timezone_();
+    if (tz == nullptr) {
+      this->apply_timezone_(nullptr);
+      return;
     }
+    // Stack buffer - TZ strings from tzdata are typically short (< 50 chars)
+    char buf[128];
+    if (len >= sizeof(buf))
+      len = sizeof(buf) - 1;
+    memcpy(buf, tz, len);
+    buf[len] = '\0';
+    this->apply_timezone_(buf);
   }
 
-  /// Get the time zone currently in use.
-  std::string get_timezone() { return this->timezone_; }
+  /// Set the time zone from a std::string.
+  void set_timezone(const std::string &tz) { this->apply_timezone_(tz.c_str()); }
 #endif
 
   /// Get the time in the currently defined timezone.
-  ESPTime now() { return ESPTime::from_epoch_local(this->timestamp_now()); }
+  ESPTime now();
 
   /// Get the time without any time zone or DST corrections.
   ESPTime utcnow() { return ESPTime::from_epoch_utc(this->timestamp_now()); }
@@ -58,8 +66,7 @@ class RealTimeClock : public PollingComponent {
   void synchronize_epoch_(uint32_t epoch);
 
 #ifdef USE_TIME_TIMEZONE
-  std::string timezone_{};
-  void apply_timezone_();
+  void apply_timezone_(const char *tz);
 #endif
 
   LazyCallbackManager<void()> time_sync_callback_;
diff --git a/esphome/components/uart/uart_component_rp2040.cpp b/esphome/components/uart/uart_component_rp2040.cpp
index 0c6834055c..faf8f4d90f 100644
--- a/esphome/components/uart/uart_component_rp2040.cpp
+++ b/esphome/components/uart/uart_component_rp2040.cpp
@@ -115,8 +115,8 @@ void RP2040UartComponent::setup() {
 
   if (tx_hw == -1 || rx_hw == -1 || tx_hw != rx_hw) {
     ESP_LOGV(TAG, "Using SerialPIO");
-    pin_size_t tx = this->tx_pin_ == nullptr ? SerialPIO::NOPIN : this->tx_pin_->get_pin();
-    pin_size_t rx = this->rx_pin_ == nullptr ? SerialPIO::NOPIN : this->rx_pin_->get_pin();
+    pin_size_t tx = this->tx_pin_ == nullptr ? NOPIN : this->tx_pin_->get_pin();
+    pin_size_t rx = this->rx_pin_ == nullptr ? NOPIN : this->rx_pin_->get_pin();
     auto *serial = new SerialPIO(tx, rx, this->rx_buffer_size_);  // NOLINT(cppcoreguidelines-owning-memory)
     serial->begin(this->baud_rate_, config);
     if (this->tx_pin_ != nullptr && this->tx_pin_->is_inverted())
diff --git a/esphome/components/web_server/list_entities.cpp b/esphome/components/web_server/list_entities.cpp
index 8458298062..ebe7bf4450 100644
--- a/esphome/components/web_server/list_entities.cpp
+++ b/esphome/components/web_server/list_entities.cpp
@@ -14,8 +14,6 @@ ListEntitiesIterator::ListEntitiesIterator(const WebServer *ws, AsyncEventSource
 ListEntitiesIterator::ListEntitiesIterator(const WebServer *ws, DeferredUpdateEventSource *es)
     : web_server_(ws), events_(es) {}
 #endif
-ListEntitiesIterator::~ListEntitiesIterator() {}
-
 #ifdef USE_BINARY_SENSOR
 bool ListEntitiesIterator::on_binary_sensor(binary_sensor::BinarySensor *obj) {
   this->events_->deferrable_send_state(obj, "state_detail_all", WebServer::binary_sensor_all_json_generator);
diff --git a/esphome/components/web_server/list_entities.h b/esphome/components/web_server/list_entities.h
index d0a4fa2725..6a84066109 100644
--- a/esphome/components/web_server/list_entities.h
+++ b/esphome/components/web_server/list_entities.h
@@ -17,14 +17,13 @@ class DeferredUpdateEventSource;
 #endif
 class WebServer;
 
-class ListEntitiesIterator : public ComponentIterator {
+class ListEntitiesIterator final : public ComponentIterator {
  public:
 #ifdef USE_ESP32
   ListEntitiesIterator(const WebServer *ws, esphome::web_server_idf::AsyncEventSource *es);
 #elif defined(USE_ARDUINO)
   ListEntitiesIterator(const WebServer *ws, DeferredUpdateEventSource *es);
 #endif
-  virtual ~ListEntitiesIterator();
 #ifdef USE_BINARY_SENSOR
   bool on_binary_sensor(binary_sensor::BinarySensor *obj) override;
 #endif
diff --git a/esphome/components/web_server/ota/ota_web_server.h b/esphome/components/web_server/ota/ota_web_server.h
index 53ff99899c..0857c31c5d 100644
--- a/esphome/components/web_server/ota/ota_web_server.h
+++ b/esphome/components/web_server/ota/ota_web_server.h
@@ -9,7 +9,7 @@
 
 namespace esphome::web_server {
 
-class WebServerOTAComponent : public ota::OTAComponent {
+class WebServerOTAComponent final : public ota::OTAComponent {
  public:
   void setup() override;
   void dump_config() override;
diff --git a/esphome/components/web_server/server_index_v2.h b/esphome/components/web_server/server_index_v2.h
index ffa9c87b3a..ac2195f387 100644
--- a/esphome/components/web_server/server_index_v2.h
+++ b/esphome/components/web_server/server_index_v2.h
@@ -9,7 +9,7 @@
 namespace esphome::web_server {
 
 #ifdef USE_WEBSERVER_GZIP
-const uint8_t INDEX_GZ[] PROGMEM = {
+constexpr uint8_t INDEX_GZ[] PROGMEM = {
     0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0xed, 0x7d, 0xd9, 0x72, 0xdb, 0x48, 0xb6, 0xe0, 0xf3,
     0xd4, 0x57, 0x40, 0x28, 0xb5, 0x8c, 0x2c, 0x26, 0xc1, 0x45, 0x92, 0x2d, 0x83, 0x4a, 0xb2, 0x65, 0xd9, 0xd5, 0x76,
     0x97, 0xb7, 0xb6, 0xec, 0xda, 0x58, 0x6c, 0x09, 0x02, 0x92, 0x44, 0x96, 0x41, 0x80, 0x05, 0x24, 0xb5, 0x14, 0x89,
@@ -698,7 +698,7 @@ const uint8_t INDEX_GZ[] PROGMEM = {
     0x01, 0x65, 0x21, 0x07, 0x4b, 0xe3, 0x97, 0x00, 0x00};
 
 #else  // Brotli (default, smaller)
-const uint8_t INDEX_BR[] PROGMEM = {
+constexpr uint8_t INDEX_BR[] PROGMEM = {
     0x1b, 0xe2, 0x97, 0xa3, 0x90, 0xa2, 0x95, 0x55, 0x51, 0x04, 0x1b, 0x07, 0x80, 0x20, 0x79, 0x0e, 0x50, 0xab, 0x02,
     0xdb, 0x98, 0x16, 0xf4, 0x7b, 0x22, 0xa3, 0x4d, 0xd3, 0x86, 0xc1, 0x26, 0x48, 0x49, 0x60, 0xbe, 0xb3, 0xc9, 0xa1,
     0x8c, 0x96, 0x10, 0x1b, 0x21, 0xcf, 0x48, 0x68, 0xce, 0x10, 0x34, 0x32, 0x7c, 0xbf, 0x71, 0x7b, 0x03, 0x8f, 0xdd,
diff --git a/esphome/components/web_server/server_index_v3.h b/esphome/components/web_server/server_index_v3.h
index b7c15df32b..a1cafe8707 100644
--- a/esphome/components/web_server/server_index_v3.h
+++ b/esphome/components/web_server/server_index_v3.h
@@ -9,7 +9,7 @@
 namespace esphome::web_server {
 
 #ifdef USE_WEBSERVER_GZIP
-const uint8_t INDEX_GZ[] PROGMEM = {
+constexpr uint8_t INDEX_GZ[] PROGMEM = {
     0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0xcc, 0xbd, 0x7b, 0x7f, 0x1a, 0xb9, 0xb2, 0x28, 0xfa,
     0xf7, 0x3d, 0x9f, 0xc2, 0xee, 0x9d, 0xf1, 0xb4, 0x8c, 0x68, 0x03, 0x36, 0x8e, 0xd3, 0x58, 0xe6, 0xe4, 0x39, 0xc9,
     0x3c, 0x92, 0x4c, 0x9c, 0x64, 0x26, 0xc3, 0xb0, 0x33, 0xa2, 0x11, 0xa0, 0xa4, 0x91, 0x98, 0x96, 0x88, 0xed, 0x01,
@@ -4107,7 +4107,7 @@ const uint8_t INDEX_GZ[] PROGMEM = {
     0xe8, 0xcd, 0xfe, 0x2c, 0x9d, 0x07, 0xfd, 0xff, 0x05, 0x64, 0x23, 0xa6, 0xdb, 0x06, 0x7b, 0x03, 0x00};
 
 #else  // Brotli (default, smaller)
-const uint8_t INDEX_BR[] PROGMEM = {
+constexpr uint8_t INDEX_BR[] PROGMEM = {
     0x5b, 0x05, 0x7b, 0x53, 0xc1, 0xb6, 0x69, 0x3d, 0x41, 0xeb, 0x04, 0x30, 0xf6, 0xd6, 0x77, 0x35, 0xdb, 0xa3, 0x08,
     0x36, 0x0e, 0x04, 0x80, 0x90, 0x4f, 0xf1, 0xb2, 0x21, 0xa4, 0x82, 0xee, 0x00, 0xaa, 0x20, 0x7f, 0x3b, 0xff, 0x00,
     0xaa, 0x9a, 0x73, 0x74, 0x8c, 0xe1, 0xa6, 0x1f, 0xa0, 0xa2, 0x59, 0xf5, 0xaa, 0x92, 0x79, 0x50, 0x43, 0x1f, 0xe8,
diff --git a/esphome/components/web_server/web_server.h b/esphome/components/web_server/web_server.h
index 76c1c8b0bd..64c492f82b 100644
--- a/esphome/components/web_server/web_server.h
+++ b/esphome/components/web_server/web_server.h
@@ -107,7 +107,7 @@ enum JsonDetail { DETAIL_ALL, DETAIL_STATE };
 using message_generator_t = json::SerializationBuffer<>(WebServer *, void *);
 
 class DeferredUpdateEventSourceList;
-class DeferredUpdateEventSource : public AsyncEventSource {
+class DeferredUpdateEventSource final : public AsyncEventSource {
   friend class DeferredUpdateEventSourceList;
 
   /*
@@ -163,7 +163,7 @@ class DeferredUpdateEventSource : public AsyncEventSource {
   void try_send_nodefer(const char *message, const char *event = nullptr, uint32_t id = 0, uint32_t reconnect = 0);
 };
 
-class DeferredUpdateEventSourceList : public std::list<DeferredUpdateEventSource *> {
+class DeferredUpdateEventSourceList final : public std::list<DeferredUpdateEventSource *> {
  protected:
   void on_client_connect_(DeferredUpdateEventSource *source);
   void on_client_disconnect_(DeferredUpdateEventSource *source);
@@ -187,7 +187,7 @@ class DeferredUpdateEventSourceList : public std::list<DeferredUpdateEventSource
  * under the '/light/...', '/sensor/...', ... URLs. A full documentation for this API
  * can be found under https://esphome.io/web-api/.
  */
-class WebServer : public Controller, public Component, public AsyncWebHandler {
+class WebServer final : public Controller, public Component, public AsyncWebHandler {
 #if !defined(USE_ESP32) && defined(USE_ARDUINO)
   friend class DeferredUpdateEventSourceList;
 #endif
diff --git a/esphome/components/web_server_idf/web_server_idf.cpp b/esphome/components/web_server_idf/web_server_idf.cpp
index 4034a22586..f18570965b 100644
--- a/esphome/components/web_server_idf/web_server_idf.cpp
+++ b/esphome/components/web_server_idf/web_server_idf.cpp
@@ -921,7 +921,7 @@ esp_err_t AsyncWebServer::handle_multipart_upload_(httpd_req_t *r, const char *c
   });
 
   // Use heap buffer - 1460 bytes is too large for the httpd task stack
-  auto buffer = std::make_unique<char[]>(MULTIPART_CHUNK_SIZE);
+  auto buffer = std::make_unique_for_overwrite<char[]>(MULTIPART_CHUNK_SIZE);
   size_t bytes_since_yield = 0;
 
   for (size_t remaining = r->content_len; remaining > 0;) {
diff --git a/esphome/components/wifi/wifi_component.cpp b/esphome/components/wifi/wifi_component.cpp
index d5d0419395..1e6961b8bd 100644
--- a/esphome/components/wifi/wifi_component.cpp
+++ b/esphome/components/wifi/wifi_component.cpp
@@ -3,6 +3,7 @@
 #include <cassert>
 #include <cinttypes>
 #include <cmath>
+#include <type_traits>
 
 #ifdef USE_ESP32
 #if (ESP_IDF_VERSION_MAJOR >= 5 && ESP_IDF_VERSION_MINOR >= 1)
@@ -1334,20 +1335,61 @@ void WiFiComponent::start_scanning() {
 // Using insertion sort instead of std::stable_sort saves flash memory
 // by avoiding template instantiations (std::rotate, std::stable_sort, lambdas)
 // IMPORTANT: This sort is stable (preserves relative order of equal elements)
+//
+// Uses raw memcpy instead of copy assignment to avoid CompactString's
+// destructor/constructor overhead (heap delete[]/new[] for long SSIDs).
+// Copy assignment calls ~CompactString() then placement-new for every shift,
+// which means delete[]/new[] per shift for heap-allocated SSIDs. With 70+
+// networks (e.g., captive portal showing full scan results), this caused
+// event loop blocking from hundreds of heap operations in a tight loop.
+//
+// This is safe because we're permuting elements within the same array —
+// each slot is overwritten exactly once, so no ownership duplication occurs.
+// All members of WiFiScanResult are either trivially copyable (bssid, channel,
+// rssi, priority, flags) or CompactString, which stores either inline data or
+// a heap pointer — never a self-referential pointer (unlike std::string's SSO
+// on some implementations). This was not possible before PR#13472 replaced
+// std::string with CompactString, since std::string's internal layout is
+// implementation-defined and may use self-referential pointers.
+//
+// TODO: If C++ standardizes std::trivially_relocatable, add the assertion for
+// WiFiScanResult/CompactString here to formally express the memcpy safety guarantee.
 template<typename VectorType> static void insertion_sort_scan_results(VectorType &results) {
+  // memcpy-based sort requires no self-referential pointers or virtual dispatch.
+  // These static_asserts guard the assumptions. If any fire, the memcpy sort
+  // must be reviewed for safety before updating the expected values.
+  //
+  // No vtable pointers (memcpy would corrupt vptr)
+  static_assert(!std::is_polymorphic<WiFiScanResult>::value, "WiFiScanResult must not have vtable");
+  static_assert(!std::is_polymorphic<CompactString>::value, "CompactString must not have vtable");
+  // Standard layout ensures predictable memory layout with no virtual bases
+  // and no mixed-access-specifier reordering
+  static_assert(std::is_standard_layout<WiFiScanResult>::value, "WiFiScanResult must be standard layout");
+  static_assert(std::is_standard_layout<CompactString>::value, "CompactString must be standard layout");
+  // Size checks catch added/removed fields that may need safety review
+  static_assert(sizeof(WiFiScanResult) == 32, "WiFiScanResult size changed - verify memcpy sort is still safe");
+  static_assert(sizeof(CompactString) == 20, "CompactString size changed - verify memcpy sort is still safe");
+  // Alignment must match for reinterpret_cast of key_buf to be valid
+  static_assert(alignof(WiFiScanResult) <= alignof(std::max_align_t), "WiFiScanResult alignment exceeds max_align_t");
   const size_t size = results.size();
+  constexpr size_t elem_size = sizeof(WiFiScanResult);
+  // Suppress warnings for intentional memcpy on non-trivially-copyable type.
+  // Safety is guaranteed by the static_asserts above and the permutation invariant.
+  // NOLINTNEXTLINE(bugprone-undefined-memory-manipulation)
+  auto *memcpy_fn = &memcpy;
   for (size_t i = 1; i < size; i++) {
-    // Make a copy to avoid issues with move semantics during comparison
-    WiFiScanResult key = results[i];
+    alignas(WiFiScanResult) uint8_t key_buf[elem_size];
+    memcpy_fn(key_buf, &results[i], elem_size);
+    const auto &key = *reinterpret_cast<const WiFiScanResult *>(key_buf);
     int32_t j = i - 1;
 
     // Move elements that are worse than key to the right
     // For stability, we only move if key is strictly better than results[j]
     while (j >= 0 && wifi_scan_result_is_better(key, results[j])) {
-      results[j + 1] = results[j];
+      memcpy_fn(&results[j + 1], &results[j], elem_size);
       j--;
     }
-    results[j + 1] = key;
+    memcpy_fn(&results[j + 1], key_buf, elem_size);
   }
 }
 
diff --git a/esphome/components/wifi/wifi_component.h b/esphome/components/wifi/wifi_component.h
index 984930c80c..63c7039f21 100644
--- a/esphome/components/wifi/wifi_component.h
+++ b/esphome/components/wifi/wifi_component.h
@@ -10,6 +10,7 @@
 
 #include <span>
 #include <string>
+#include <type_traits>
 #include <vector>
 
 #ifdef USE_LIBRETINY
@@ -223,6 +224,14 @@ class CompactString {
 };
 
 static_assert(sizeof(CompactString) == 20, "CompactString must be exactly 20 bytes");
+// CompactString is not trivially copyable (non-trivial destructor/copy for heap case).
+// However, its layout has no self-referential pointers: storage_[] contains either inline
+// data or an external heap pointer — never a pointer to itself. This is unlike libstdc++
+// std::string SSO where _M_p points to _M_local_buf within the same object.
+// This property allows memcpy-based permutation sorting where each element ends up in
+// exactly one slot (no ownership duplication). These asserts document that layout property.
+static_assert(std::is_standard_layout<CompactString>::value, "CompactString must be standard layout");
+static_assert(!std::is_polymorphic<CompactString>::value, "CompactString must not have vtable");
 
 class WiFiAP {
   friend class WiFiComponent;
diff --git a/esphome/components/wifi/wifi_component_pico_w.cpp b/esphome/components/wifi/wifi_component_pico_w.cpp
index 1baf21e2b2..9b2c077dc5 100644
--- a/esphome/components/wifi/wifi_component_pico_w.cpp
+++ b/esphome/components/wifi/wifi_component_pico_w.cpp
@@ -78,8 +78,13 @@ bool WiFiComponent::wifi_sta_connect_(const WiFiAP &ap) {
     return false;
 #endif
 
-  auto ret = WiFi.begin(ap.ssid_.c_str(), ap.password_.c_str());
-  if (ret != WL_CONNECTED)
+  // Use beginNoBlock to avoid WiFi.begin()'s additional 2x timeout wait loop on top of
+  // CYW43::begin()'s internal blocking join. CYW43::begin() blocks for up to 10 seconds
+  // (default timeout) to complete the join - this is required because the LwipIntfDev netif
+  // setup depends on begin() succeeding. beginNoBlock() skips the outer wait loop, saving
+  // up to 20 additional seconds of blocking per attempt.
+  auto ret = WiFi.beginNoBlock(ap.ssid_.c_str(), ap.password_.c_str());
+  if (ret == WL_IDLE_STATUS)
     return false;
 
   return true;
@@ -116,13 +121,19 @@ const char *get_disconnect_reason_str(uint8_t reason) {
 }
 
 WiFiSTAConnectStatus WiFiComponent::wifi_sta_connect_status_() {
-  int status = cyw43_tcpip_link_status(&cyw43_state, CYW43_ITF_STA);
+  // Use cyw43_wifi_link_status instead of cyw43_tcpip_link_status because the Arduino
+  // framework's __wrap_cyw43_cb_tcpip_init is a no-op — the SDK's internal netif
+  // (cyw43_state.netif[]) is never initialized. cyw43_tcpip_link_status checks that netif's
+  // flags and would only fall through to cyw43_wifi_link_status when the flags aren't set.
+  // Using cyw43_wifi_link_status directly gives us the actual WiFi radio join state.
+  int status = cyw43_wifi_link_status(&cyw43_state, CYW43_ITF_STA);
   switch (status) {
     case CYW43_LINK_JOIN:
-    case CYW43_LINK_NOIP:
+      // WiFi joined, check if we have an IP address via the Arduino framework's WiFi class
+      if (WiFi.status() == WL_CONNECTED) {
+        return WiFiSTAConnectStatus::CONNECTED;
+      }
       return WiFiSTAConnectStatus::CONNECTING;
-    case CYW43_LINK_UP:
-      return WiFiSTAConnectStatus::CONNECTED;
     case CYW43_LINK_FAIL:
     case CYW43_LINK_BADAUTH:
       return WiFiSTAConnectStatus::ERROR_CONNECT_FAILED;
@@ -139,18 +150,24 @@ int WiFiComponent::s_wifi_scan_result(void *env, const cyw43_ev_scan_result_t *r
 
 void WiFiComponent::wifi_scan_result(void *env, const cyw43_ev_scan_result_t *result) {
   s_scan_result_count++;
-  const char *ssid_cstr = reinterpret_cast<const char *>(result->ssid);
+
+  // CYW43 scan results have ssid as a 32-byte buffer that is NOT null-terminated.
+  // Use ssid_len to create a properly terminated copy for string operations.
+  uint8_t len = std::min(result->ssid_len, static_cast<uint8_t>(sizeof(result->ssid)));
+  char ssid_buf[33];  // 32 max + null terminator
+  memcpy(ssid_buf, result->ssid, len);
+  ssid_buf[len] = '\0';
 
   // Skip networks that don't match any configured network (unless full results needed)
-  if (!this->needs_full_scan_results_() && !this->matches_configured_network_(ssid_cstr, result->bssid)) {
-    this->log_discarded_scan_result_(ssid_cstr, result->bssid, result->rssi, result->channel);
+  if (!this->needs_full_scan_results_() && !this->matches_configured_network_(ssid_buf, result->bssid)) {
+    this->log_discarded_scan_result_(ssid_buf, result->bssid, result->rssi, result->channel);
     return;
   }
 
   bssid_t bssid;
   std::copy(result->bssid, result->bssid + 6, bssid.begin());
-  WiFiScanResult res(bssid, ssid_cstr, strlen(ssid_cstr), result->channel, result->rssi,
-                     result->auth_mode != CYW43_AUTH_OPEN, ssid_cstr[0] == '\0');
+  WiFiScanResult res(bssid, ssid_buf, len, result->channel, result->rssi, result->auth_mode != CYW43_AUTH_OPEN,
+                     len == 0);
   if (std::find(this->scan_result_.begin(), this->scan_result_.end(), res) == this->scan_result_.end()) {
     this->scan_result_.push_back(res);
   }
@@ -167,7 +184,6 @@ bool WiFiComponent::wifi_scan_start_(bool passive) {
     ESP_LOGV(TAG, "cyw43_wifi_scan failed");
   }
   return err == 0;
-  return true;
 }
 
 #ifdef USE_WIFI_AP
@@ -212,8 +228,10 @@ network::IPAddress WiFiComponent::wifi_soft_ap_ip() { return {(const ip_addr_t *
 #endif  // USE_WIFI_AP
 
 bool WiFiComponent::wifi_disconnect_() {
-  int err = cyw43_wifi_leave(&cyw43_state, CYW43_ITF_STA);
-  return err == 0;
+  // Use Arduino WiFi.disconnect() instead of raw cyw43_wifi_leave() to properly
+  // clean up the lwIP netif, DHCP client, and internal Arduino state.
+  WiFi.disconnect();
+  return true;
 }
 
 bssid_t WiFiComponent::wifi_bssid() {
@@ -269,9 +287,10 @@ void WiFiComponent::wifi_loop_() {
 
   // Poll for connection state changes
   // The arduino-pico WiFi library doesn't have event callbacks like ESP8266/ESP32,
-  // so we need to poll the link status to detect state changes
-  auto status = cyw43_tcpip_link_status(&cyw43_state, CYW43_ITF_STA);
-  bool is_connected = (status == CYW43_LINK_UP);
+  // so we need to poll the link status to detect state changes.
+  // Use WiFi.connected() which checks both the WiFi link and IP address via the
+  // Arduino framework's own netif (not the SDK's uninitialized one).
+  bool is_connected = WiFi.connected();
 
   // Detect connection state change
   if (is_connected && !s_sta_was_connected) {
diff --git a/esphome/core/application.cpp b/esphome/core/application.cpp
index 6a7683a987..a9753da1b5 100644
--- a/esphome/core/application.cpp
+++ b/esphome/core/application.cpp
@@ -9,6 +9,9 @@
 #endif
 #ifdef USE_ESP32
 #include <esp_chip_info.h>
+#include "esphome/core/lwip_fast_select.h"
+#include <freertos/FreeRTOS.h>
+#include <freertos/task.h>
 #endif
 #include "esphome/core/version.h"
 #include "esphome/core/hal.h"
@@ -144,8 +147,14 @@ void Application::setup() {
   clear_setup_priority_overrides();
 #endif
 
-#if defined(USE_SOCKET_SELECT_SUPPORT) && defined(USE_WAKE_LOOP_THREADSAFE)
-  // Set up wake socket for waking main loop from tasks
+#if defined(USE_SOCKET_SELECT_SUPPORT) && defined(USE_ESP32)
+  // Initialize fast select: saves main loop task handle for xTaskNotifyGive wake.
+  // Always init on ESP32 — the fast path (rcvevent reads + ulTaskNotifyTake) is used
+  // unconditionally when USE_SOCKET_SELECT_SUPPORT is enabled.
+  esphome_lwip_fast_select_init();
+#endif
+#if defined(USE_SOCKET_SELECT_SUPPORT) && defined(USE_WAKE_LOOP_THREADSAFE) && !defined(USE_ESP32)
+  // Set up wake socket for waking main loop from tasks (non-ESP32 only)
   this->setup_wake_loop_threadsafe_();
 #endif
 
@@ -523,7 +532,7 @@ void Application::enable_pending_loops_() {
 }
 
 void Application::before_loop_tasks_(uint32_t loop_start_time) {
-#if defined(USE_SOCKET_SELECT_SUPPORT) && defined(USE_WAKE_LOOP_THREADSAFE)
+#if defined(USE_SOCKET_SELECT_SUPPORT) && defined(USE_WAKE_LOOP_THREADSAFE) && !defined(USE_ESP32)
   // Drain wake notifications first to clear socket for next wake
   this->drain_wake_notifications_();
 #endif
@@ -576,11 +585,15 @@ bool Application::register_socket_fd(int fd) {
 #endif
 
   this->socket_fds_.push_back(fd);
+#ifdef USE_ESP32
+  // Hook the socket's netconn callback for instant wake on receive events
+  esphome_lwip_hook_socket(fd);
+#else
   this->socket_fds_changed_ = true;
-
   if (fd > this->max_fd_) {
     this->max_fd_ = fd;
   }
+#endif
 
   return true;
 }
@@ -595,12 +608,14 @@ void Application::unregister_socket_fd(int fd) {
     if (this->socket_fds_[i] != fd)
       continue;
 
-    // Swap with last element and pop - O(1) removal since order doesn't matter
+    // Swap with last element and pop - O(1) removal since order doesn't matter.
+    // No need to unhook the netconn callback on ESP32 — all LwIP sockets share
+    // the same static event_callback, and the socket will be closed by the caller.
     if (i < this->socket_fds_.size() - 1)
       this->socket_fds_[i] = this->socket_fds_.back();
     this->socket_fds_.pop_back();
+#ifndef USE_ESP32
     this->socket_fds_changed_ = true;
-
     // Only recalculate max_fd if we removed the current max
     if (fd == this->max_fd_) {
       this->max_fd_ = -1;
@@ -609,6 +624,7 @@ void Application::unregister_socket_fd(int fd) {
           this->max_fd_ = sock_fd;
       }
     }
+#endif
     return;
   }
 }
@@ -616,16 +632,41 @@ void Application::unregister_socket_fd(int fd) {
 #endif
 
 void Application::yield_with_select_(uint32_t delay_ms) {
-  // Delay while monitoring sockets. When delay_ms is 0, always yield() to ensure other tasks run
-  // since select() with 0 timeout only polls without yielding.
-#ifdef USE_SOCKET_SELECT_SUPPORT
-  if (!this->socket_fds_.empty()) {
+  // Delay while monitoring sockets. When delay_ms is 0, always yield() to ensure other tasks run.
+#if defined(USE_SOCKET_SELECT_SUPPORT) && defined(USE_ESP32)
+  // ESP32 fast path: reads rcvevent directly via lwip_socket_dbg_get_socket() (~215 ns per socket).
+  // Safe because this runs on the main loop which owns socket lifetime (create, read, close).
+  if (delay_ms == 0) [[unlikely]] {
+    yield();
+    return;
+  }
+
+  // Check if any socket already has pending data before sleeping.
+  // If a socket still has unread data (rcvevent > 0) but the task notification was already
+  // consumed, ulTaskNotifyTake would block until timeout — adding up to delay_ms latency.
+  // This scan preserves select() semantics: return immediately when any fd is ready.
+  for (int fd : this->socket_fds_) {
+    if (esphome_lwip_socket_has_data(fd)) {
+      yield();
+      return;
+    }
+  }
+
+  // Sleep with instant wake via FreeRTOS task notification.
+  // Woken by: callback wrapper (socket data arrives), wake_loop_threadsafe() (other tasks), or timeout.
+  // Without USE_WAKE_LOOP_THREADSAFE, only hooked socket callbacks wake the task —
+  // background tasks won't call wake, so this degrades to a pure timeout (same as old select path).
+  ulTaskNotifyTake(pdTRUE, pdMS_TO_TICKS(delay_ms));
+
+#elif defined(USE_SOCKET_SELECT_SUPPORT)
+  // Non-ESP32 select() path (LibreTiny bk72xx/rtl87xx, host platform).
+  // ESP32 is excluded by the #if above — both BSD_SOCKETS and LWIP_SOCKETS on ESP32
+  // use LwIP under the hood, so the fast path handles all ESP32 socket implementations.
+  if (!this->socket_fds_.empty()) [[likely]] {
     // Update fd_set if socket list has changed
-    if (this->socket_fds_changed_) {
+    if (this->socket_fds_changed_) [[unlikely]] {
       FD_ZERO(&this->base_read_fds_);
-      // fd bounds are already validated in register_socket_fd() or guaranteed by platform design:
-      // - ESP32: LwIP guarantees fd < FD_SETSIZE by design (LWIP_SOCKET_OFFSET = FD_SETSIZE - CONFIG_LWIP_MAX_SOCKETS)
-      // - Other platforms: register_socket_fd() validates fd < FD_SETSIZE
+      // fd bounds are validated in register_socket_fd()
       for (int fd : this->socket_fds_) {
         FD_SET(fd, &this->base_read_fds_);
       }
@@ -641,7 +682,7 @@ void Application::yield_with_select_(uint32_t delay_ms) {
     tv.tv_usec = (delay_ms - tv.tv_sec * 1000) * 1000;
 
     // Call select with timeout
-#if defined(USE_SOCKET_IMPL_LWIP_SOCKETS) || (defined(USE_ESP32) && defined(USE_SOCKET_IMPL_BSD_SOCKETS))
+#ifdef USE_SOCKET_IMPL_LWIP_SOCKETS
     int ret = lwip_select(this->max_fd_ + 1, &this->read_fds_, nullptr, nullptr, &tv);
 #else
     int ret = ::select(this->max_fd_ + 1, &this->read_fds_, nullptr, nullptr, &tv);
@@ -651,19 +692,18 @@ void Application::yield_with_select_(uint32_t delay_ms) {
     // ret < 0: error (except EINTR which is normal)
     // ret > 0: socket(s) have data ready - normal and expected
     // ret == 0: timeout occurred - normal and expected
-    if (ret < 0 && errno != EINTR) {
-      // Actual error - log and fall back to delay
-      ESP_LOGW(TAG, "select() failed with errno %d", errno);
-      delay(delay_ms);
+    if (ret >= 0 || errno == EINTR) [[likely]] {
+      // Yield if zero timeout since select(0) only polls without yielding
+      if (delay_ms == 0) [[unlikely]] {
+        yield();
+      }
+      return;
     }
-    // When delay_ms is 0, we need to yield since select(0) doesn't yield
-    if (delay_ms == 0) {
-      yield();
-    }
-  } else {
-    // No sockets registered, use regular delay
-    delay(delay_ms);
+    // select() error - log and fall through to delay()
+    ESP_LOGW(TAG, "select() failed with errno %d", errno);
   }
+  // No sockets registered or select() failed - use regular delay
+  delay(delay_ms);
 #elif defined(USE_ESP8266) && defined(USE_SOCKET_IMPL_LWIP_TCP)
   // No select support but can wake on socket activity via esp_schedule()
   socket::socket_delay(delay_ms);
@@ -673,9 +713,25 @@ void Application::yield_with_select_(uint32_t delay_ms) {
 #endif
 }
 
-Application App;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
+// App storage — asm label shares the linker symbol with "extern Application App".
+// char[] is trivially destructible, so no __cxa_atexit or destructor chain is emitted.
+// Constructed via placement new in the generated setup().
+#ifndef __GXX_ABI_VERSION
+#error "Application placement new requires Itanium C++ ABI (GCC/Clang)"
+#endif
+static_assert(std::is_default_constructible<Application>::value, "Application must be default-constructible");
+// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
+alignas(Application) char app_storage[sizeof(Application)] asm("_ZN7esphome3AppE");
 
 #if defined(USE_SOCKET_SELECT_SUPPORT) && defined(USE_WAKE_LOOP_THREADSAFE)
+
+#ifdef USE_ESP32
+void Application::wake_loop_threadsafe() {
+  // Direct FreeRTOS task notification — <1 us, task context only (NOT ISR-safe)
+  esphome_lwip_wake_main_loop();
+}
+#else   // !USE_ESP32
+
 void Application::setup_wake_loop_threadsafe_() {
   // Create UDP socket for wake notifications
   this->wake_socket_fd_ = lwip_socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
@@ -742,6 +798,8 @@ void Application::wake_loop_threadsafe() {
     lwip_send(this->wake_socket_fd_, &dummy, 1, 0);
   }
 }
+#endif  // USE_ESP32
+
 #endif  // defined(USE_SOCKET_SELECT_SUPPORT) && defined(USE_WAKE_LOOP_THREADSAFE)
 
 void Application::get_build_time_string(std::span<char, BUILD_TIME_STR_SIZE> buffer) {
diff --git a/esphome/core/application.h b/esphome/core/application.h
index cd275bb97f..f5df5e7bdf 100644
--- a/esphome/core/application.h
+++ b/esphome/core/application.h
@@ -24,10 +24,14 @@
 #endif
 
 #ifdef USE_SOCKET_SELECT_SUPPORT
+#ifdef USE_ESP32
+#include "esphome/core/lwip_fast_select.h"
+#else
 #include <sys/select.h>
 #ifdef USE_WAKE_LOOP_THREADSAFE
 #include <lwip/sockets.h>
 #endif
+#endif
 #endif  // USE_SOCKET_SELECT_SUPPORT
 
 #ifdef USE_BINARY_SENSOR
@@ -491,15 +495,12 @@ class Application {
   /// @return true if registration was successful, false if fd exceeds limits
   bool register_socket_fd(int fd);
   void unregister_socket_fd(int fd);
-  /// Check if there's data available on a socket without blocking
-  /// This function is thread-safe for reading, but should be called after select() has run
-  /// The read_fds_ is only modified by select() in the main loop
-  bool is_socket_ready(int fd) const { return fd >= 0 && this->is_socket_ready_(fd); }
 
 #ifdef USE_WAKE_LOOP_THREADSAFE
-  /// Wake the main event loop from a FreeRTOS task
-  /// Thread-safe, can be called from task context to immediately wake select()
-  /// IMPORTANT: NOT safe to call from ISR context (socket operations not ISR-safe)
+  /// Wake the main event loop from another FreeRTOS task.
+  /// Thread-safe, but must only be called from task context (NOT ISR-safe).
+  /// On ESP32: uses xTaskNotifyGive (<1 us)
+  /// On other platforms: uses UDP loopback socket
   void wake_loop_threadsafe();
 #endif
 #endif
@@ -510,10 +511,14 @@ class Application {
 
 #ifdef USE_SOCKET_SELECT_SUPPORT
   /// Fast path for Socket::ready() via friendship - skips negative fd check.
-  /// Safe because: fd was validated in register_socket_fd() at registration time,
-  /// and Socket::ready() only calls this when loop_monitored_ is true (registration succeeded).
-  /// FD_ISSET may include its own upper bounds check depending on platform.
+  /// Main loop only — on ESP32, reads rcvevent via lwip_socket_dbg_get_socket()
+  /// which has no refcount; safe only because the main loop owns socket lifetime
+  /// (creates, reads, and closes sockets on the same thread).
+#ifdef USE_ESP32
+  bool is_socket_ready_(int fd) const { return esphome_lwip_socket_has_data(fd); }
+#else
   bool is_socket_ready_(int fd) const { return FD_ISSET(fd, &this->read_fds_); }
+#endif
 #endif
 
   void register_component_(Component *comp);
@@ -541,7 +546,7 @@ class Application {
   /// Perform a delay while also monitoring socket file descriptors for readiness
   void yield_with_select_(uint32_t delay_ms);
 
-#if defined(USE_SOCKET_SELECT_SUPPORT) && defined(USE_WAKE_LOOP_THREADSAFE)
+#if defined(USE_SOCKET_SELECT_SUPPORT) && defined(USE_WAKE_LOOP_THREADSAFE) && !defined(USE_ESP32)
   void setup_wake_loop_threadsafe_();       // Create wake notification socket
   inline void drain_wake_notifications_();  // Read pending wake notifications in main loop (hot path - inlined)
 #endif
@@ -571,7 +576,7 @@ class Application {
   FixedVector<Component *> looping_components_{};
 #ifdef USE_SOCKET_SELECT_SUPPORT
   std::vector<int> socket_fds_;  // Vector of all monitored socket file descriptors
-#ifdef USE_WAKE_LOOP_THREADSAFE
+#if defined(USE_WAKE_LOOP_THREADSAFE) && !defined(USE_ESP32)
   int wake_socket_fd_{-1};  // Shared wake notification socket for waking main loop from tasks
 #endif
 #endif
@@ -584,7 +589,7 @@ class Application {
   uint32_t last_loop_{0};
   uint32_t loop_component_start_time_{0};
 
-#ifdef USE_SOCKET_SELECT_SUPPORT
+#if defined(USE_SOCKET_SELECT_SUPPORT) && !defined(USE_ESP32)
   int max_fd_{-1};  // Highest file descriptor number for select()
 #endif
 
@@ -600,14 +605,14 @@ class Application {
   bool in_loop_{false};
   volatile bool has_pending_enable_loop_requests_{false};
 
-#ifdef USE_SOCKET_SELECT_SUPPORT
+#if defined(USE_SOCKET_SELECT_SUPPORT) && !defined(USE_ESP32)
   bool socket_fds_changed_{false};  // Flag to rebuild base_read_fds_ when socket_fds_ changes
 #endif
 
-#ifdef USE_SOCKET_SELECT_SUPPORT
-  // Variable-sized members
+#if defined(USE_SOCKET_SELECT_SUPPORT) && !defined(USE_ESP32)
+  // Variable-sized members (not needed on ESP32 — is_socket_ready_ reads rcvevent directly)
+  fd_set read_fds_{};       // Working fd_set: populated by select()
   fd_set base_read_fds_{};  // Cached fd_set rebuilt only when socket_fds_ changes
-  fd_set read_fds_{};       // Working fd_set for select(), copied from base_read_fds_
 #endif
 
   // StaticVectors (largest members - contain actual array data inline)
@@ -694,7 +699,7 @@ class Application {
 /// Global storage of Application pointer - only one Application can exist.
 extern Application App;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
 
-#if defined(USE_SOCKET_SELECT_SUPPORT) && defined(USE_WAKE_LOOP_THREADSAFE)
+#if defined(USE_SOCKET_SELECT_SUPPORT) && defined(USE_WAKE_LOOP_THREADSAFE) && !defined(USE_ESP32)
 // Inline implementations for hot-path functions
 // drain_wake_notifications_() is called on every loop iteration
 
@@ -704,8 +709,8 @@ static constexpr size_t WAKE_NOTIFY_DRAIN_BUFFER_SIZE = 16;
 
 inline void Application::drain_wake_notifications_() {
   // Called from main loop to drain any pending wake notifications
-  // Must check is_socket_ready() to avoid blocking on empty socket
-  if (this->wake_socket_fd_ >= 0 && this->is_socket_ready(this->wake_socket_fd_)) {
+  // Must check is_socket_ready_() to avoid blocking on empty socket
+  if (this->wake_socket_fd_ >= 0 && this->is_socket_ready_(this->wake_socket_fd_)) {
     char buffer[WAKE_NOTIFY_DRAIN_BUFFER_SIZE];
     // Drain all pending notifications with non-blocking reads
     // Multiple wake events may have triggered multiple writes, so drain until EWOULDBLOCK
@@ -716,6 +721,6 @@ inline void Application::drain_wake_notifications_() {
     }
   }
 }
-#endif  // defined(USE_SOCKET_SELECT_SUPPORT) && defined(USE_WAKE_LOOP_THREADSAFE)
+#endif  // defined(USE_SOCKET_SELECT_SUPPORT) && defined(USE_WAKE_LOOP_THREADSAFE) && !defined(USE_ESP32)
 
 }  // namespace esphome
diff --git a/esphome/core/config.py b/esphome/core/config.py
index 21ed8ced1a..215432835a 100644
--- a/esphome/core/config.py
+++ b/esphome/core/config.py
@@ -512,6 +512,9 @@ async def to_code(config: ConfigType) -> None:
     cg.add_global(cg.RawExpression("using std::min"))
     cg.add_global(cg.RawExpression("using std::max"))
 
+    # Construct App via placement new — see application.cpp for storage details
+    cg.add_global(cg.RawStatement("#include <new>"))
+    cg.add(cg.RawExpression("new (&App) Application()"))
     cg.add(
         cg.App.pre_setup(
             config[CONF_NAME],
diff --git a/esphome/core/lwip_fast_select.c b/esphome/core/lwip_fast_select.c
new file mode 100644
index 0000000000..70a6482d48
--- /dev/null
+++ b/esphome/core/lwip_fast_select.c
@@ -0,0 +1,216 @@
+// Fast socket monitoring for ESP32 (ESP-IDF LwIP)
+// Replaces lwip_select() with direct rcvevent reads and FreeRTOS task notifications.
+//
+// This must be a .c file (not .cpp) because:
+// 1. lwip/priv/sockets_priv.h conflicts with C++ compilation units that include bootloader headers
+// 2. The netconn callback is a C function pointer
+//
+// defines.h is force-included by the build system (-include flag), providing USE_ESP32 etc.
+//
+// Thread safety analysis
+// ======================
+// Three threads interact with this code:
+//   1. Main loop task   — calls init, has_data, hook
+//   2. LwIP TCP/IP task — calls event_callback (reads s_original_callback; writes rcvevent
+//                         via the original callback under SYS_ARCH_PROTECT/UNPROTECT mutex)
+//   3. Background tasks — call wake_main_loop
+//
+// LwIP source references (ESP-IDF v5.5.2, commit 30aaf64524):
+//   sockets.c: https://github.com/espressif/esp-idf/blob/30aaf64524/components/lwip/lwip/src/api/sockets.c
+//     - event_callback (static, same for all sockets): L327
+//     - DEFAULT_SOCKET_EVENTCB = event_callback: L328
+//     - tryget_socket_unconn_nouse (direct array lookup): L450
+//     - lwip_socket_dbg_get_socket (thin wrapper): L461
+//     - All socket types use DEFAULT_SOCKET_EVENTCB: L1741, L1748, L1759
+//     - event_callback definition: L2538
+//     - SYS_ARCH_PROTECT before rcvevent switch: L2578
+//     - sock->rcvevent++ (NETCONN_EVT_RCVPLUS case): L2582
+//     - SYS_ARCH_UNPROTECT after switch: L2615
+//   sys.h: https://github.com/espressif/esp-idf/blob/30aaf64524/components/lwip/lwip/src/include/lwip/sys.h
+//     - SYS_ARCH_PROTECT calls sys_arch_protect(): L495
+//     - SYS_ARCH_UNPROTECT calls sys_arch_unprotect(): L506
+//     (ESP-IDF implements sys_arch_protect/unprotect as FreeRTOS mutex lock/unlock)
+//
+// Socket slot lifetime
+// ====================
+// This code reads struct lwip_sock fields without SYS_ARCH_PROTECT. The safety
+// argument requires that the slot cannot be freed while we read it.
+//
+// In LwIP, the socket table is a static array and slots are only freed via:
+//   lwip_close() -> lwip_close_internal() -> free_socket_free_elements() -> free_socket()
+// The TCP/IP thread does NOT call free_socket(). On link loss, RST, or timeout
+// it frees the TCP PCB and signals the netconn (rcvevent++ to indicate EOF), but
+// the netconn and lwip_sock slot remain allocated until the application calls
+// lwip_close(). ESPHome removes the fd from the monitored set before calling
+// lwip_close().
+//
+// Therefore lwip_socket_dbg_get_socket(fd) plus a volatile read of rcvevent
+// (to prevent compiler reordering or caching) is safe as long as the application
+// is single-writer for close. ESPHome guarantees this by design: all socket
+// create/read/close happens on the main loop. fd numbers are not reused while
+// the slot remains allocated, and the slot remains allocated until lwip_close().
+// Any change in LwIP that allows free_socket() to be called outside lwip_close()
+// would invalidate this assumption.
+//
+// LwIP source references for slot lifetime:
+//   sockets.c (same commit as above):
+//     - alloc_socket (slot allocation): L419
+//     - free_socket (slot deallocation): L384
+//     - free_socket_free_elements (called from lwip_close_internal): L393
+//     - lwip_close_internal (only caller of free_socket_free_elements): L2355
+//     - lwip_close (only caller of lwip_close_internal): L2450
+//
+// Shared state and safety rationale:
+//
+//   s_main_loop_task (TaskHandle_t, 4 bytes):
+//     Written once by main loop in init(). Read by TCP/IP thread (in callback)
+//     and background tasks (in wake).
+//     Safe: write-once-then-read pattern. Socket hooks may run before init(),
+//     but the NULL check on s_main_loop_task in the callback provides correct
+//     degraded behavior — notifications are simply skipped until init() completes.
+//
+//   s_original_callback (netconn_callback, 4-byte function pointer):
+//     Written by main loop in hook_socket() (only when NULL — set once).
+//     Read by TCP/IP thread in esphome_socket_event_callback().
+//     Safe: set-once pattern. The first hook_socket() captures the original callback.
+//     All subsequent hooks see it already set and skip the write. The TCP/IP thread
+//     only reads this after the callback pointer has been swapped (which happens after
+//     the write), so it always sees the initialized value.
+//
+//   sock->conn->callback (netconn_callback, 4-byte function pointer):
+//     Written by main loop in hook_socket(). Never restored — all LwIP sockets share
+//     the same static event_callback (DEFAULT_SOCKET_EVENTCB), so the wrapper stays permanently.
+//     Read by TCP/IP thread when invoking the callback.
+//     Safe: 32-bit aligned pointer writes are atomic on Xtensa and RISC-V (ESP32).
+//     The TCP/IP thread will see either the old or new pointer atomically — never a
+//     torn value. Both the wrapper and original callbacks are valid at all times
+//     (the wrapper itself calls the original), so either value is correct.
+//
+//   sock->rcvevent (s16_t, 2 bytes):
+//     Written by TCP/IP thread in event_callback under SYS_ARCH_PROTECT.
+//     Read by main loop in has_data() via volatile cast.
+//     Safe: SYS_ARCH_UNPROTECT releases a FreeRTOS mutex, which internally
+//     uses a critical section with memory barrier (rsync on dual-core Xtensa; on
+//     single-core builds the spinlock is compiled out, but cross-core visibility is
+//     not an issue). The volatile cast prevents the compiler
+//     from caching the read. Aligned 16-bit reads are single-instruction loads on
+//     Xtensa (L16SI) and RISC-V (LH), which cannot produce torn values.
+//
+//   FreeRTOS task notification value:
+//     Written by TCP/IP thread (xTaskNotifyGive in callback) and background tasks
+//     (xTaskNotifyGive in wake_main_loop). Read by main loop (ulTaskNotifyTake).
+//     Safe: FreeRTOS notification APIs are thread-safe by design (use internal
+//     critical sections). Multiple concurrent xTaskNotifyGive calls are safe —
+//     the notification count simply increments.
+
+#ifdef USE_ESP32
+
+// LwIP headers must come first — they define netconn_callback, struct lwip_sock, etc.
+#include <lwip/api.h>
+#include <lwip/priv/sockets_priv.h>
+#include <freertos/FreeRTOS.h>
+#include <freertos/task.h>
+
+#include "esphome/core/lwip_fast_select.h"
+
+#include <stddef.h>
+
+// Compile-time verification of thread safety assumptions.
+// On ESP32 (Xtensa/RISC-V), naturally-aligned reads/writes up to 32 bits are atomic.
+// These asserts ensure our cross-thread shared state meets those requirements.
+
+// Pointer types must fit in a single 32-bit store (atomic write)
+_Static_assert(sizeof(TaskHandle_t) <= 4, "TaskHandle_t must be <= 4 bytes for atomic access");
+_Static_assert(sizeof(netconn_callback) <= 4, "netconn_callback must be <= 4 bytes for atomic access");
+
+// rcvevent must fit in a single atomic read
+_Static_assert(sizeof(((struct lwip_sock *) 0)->rcvevent) <= 4, "rcvevent must be <= 4 bytes for atomic access");
+
+// Struct member alignment — natural alignment guarantees atomicity on Xtensa/RISC-V.
+// Misaligned access would not be atomic even if the size is <= 4 bytes.
+_Static_assert(offsetof(struct netconn, callback) % sizeof(netconn_callback) == 0,
+               "netconn.callback must be naturally aligned for atomic access");
+_Static_assert(offsetof(struct lwip_sock, rcvevent) % sizeof(((struct lwip_sock *) 0)->rcvevent) == 0,
+               "lwip_sock.rcvevent must be naturally aligned for atomic access");
+
+// Task handle for the main loop — written once in init(), read from TCP/IP and background tasks.
+static TaskHandle_t s_main_loop_task = NULL;
+
+// Saved original event_callback pointer — written once in first hook_socket(), read from TCP/IP task.
+static netconn_callback s_original_callback = NULL;
+
+// Wrapper callback: calls original event_callback + notifies main loop task.
+// Called from LwIP's TCP/IP thread when socket events occur (task context, not ISR).
+static void esphome_socket_event_callback(struct netconn *conn, enum netconn_evt evt, u16_t len) {
+  // Call original LwIP event_callback first — updates rcvevent/sendevent/errevent,
+  // signals any select() waiters. This preserves all LwIP behavior.
+  // s_original_callback is always valid here: hook_socket() sets it before swapping
+  // the callback pointer, so this wrapper cannot run until it's initialized.
+  s_original_callback(conn, evt, len);
+  // Wake the main loop task if sleeping in ulTaskNotifyTake().
+  // Only notify on receive events to avoid spurious wakeups from send-ready events.
+  // NETCONN_EVT_ERROR is deliberately omitted: LwIP signals errors via RCVPLUS
+  // (rcvevent++ with a NULL pbuf or error in recvmbox), so error conditions
+  // already wake the main loop through the RCVPLUS path.
+  if (evt == NETCONN_EVT_RCVPLUS) {
+    TaskHandle_t task = s_main_loop_task;
+    if (task != NULL) {
+      xTaskNotifyGive(task);
+    }
+  }
+}
+
+void esphome_lwip_fast_select_init(void) { s_main_loop_task = xTaskGetCurrentTaskHandle(); }
+
+// lwip_socket_dbg_get_socket() is a thin wrapper around the static
+// tryget_socket_unconn_nouse() — a direct array lookup without the refcount
+// that get_socket()/done_socket() uses. This is safe because:
+// 1. The only path to free_socket() is lwip_close(), called exclusively from the main loop
+// 2. The TCP/IP thread never frees socket slots (see "Socket slot lifetime" above)
+// 3. Both has_data() reads and lwip_close() run on the main loop — no concurrent free
+// If lwip_socket_dbg_get_socket() were ever removed, we could fall back to lwip_select().
+// Returns the sock only if both the sock and its netconn are valid, NULL otherwise.
+static inline struct lwip_sock *get_sock(int fd) {
+  struct lwip_sock *sock = lwip_socket_dbg_get_socket(fd);
+  if (sock == NULL || sock->conn == NULL)
+    return NULL;
+  return sock;
+}
+
+bool esphome_lwip_socket_has_data(int fd) {
+  struct lwip_sock *sock = get_sock(fd);
+  if (sock == NULL)
+    return false;
+  // volatile prevents the compiler from caching/reordering this cross-thread read.
+  // The write side (TCP/IP thread) commits via SYS_ARCH_UNPROTECT which releases a
+  // FreeRTOS mutex with a memory barrier (rsync on Xtensa), ensuring the value is
+  // visible. Aligned 16-bit reads are single-instruction loads (L16SI/LH) on
+  // Xtensa/RISC-V and cannot produce torn values.
+  return *(volatile s16_t *) &sock->rcvevent > 0;
+}
+
+void esphome_lwip_hook_socket(int fd) {
+  struct lwip_sock *sock = get_sock(fd);
+  if (sock == NULL)
+    return;
+
+  // Save original callback once — all LwIP sockets share the same static event_callback
+  // (DEFAULT_SOCKET_EVENTCB in sockets.c, used for SOCK_RAW, SOCK_DGRAM, and SOCK_STREAM).
+  if (s_original_callback == NULL) {
+    s_original_callback = sock->conn->callback;
+  }
+
+  // Replace with our wrapper. Atomic on ESP32 (32-bit aligned pointer write).
+  // TCP/IP thread sees either old or new pointer — both are valid.
+  sock->conn->callback = esphome_socket_event_callback;
+}
+
+// Wake the main loop from another FreeRTOS task. NOT ISR-safe.
+void esphome_lwip_wake_main_loop(void) {
+  TaskHandle_t task = s_main_loop_task;
+  if (task != NULL) {
+    xTaskNotifyGive(task);
+  }
+}
+
+#endif  // USE_ESP32
diff --git a/esphome/core/lwip_fast_select.h b/esphome/core/lwip_fast_select.h
new file mode 100644
index 0000000000..73a89fdc3d
--- /dev/null
+++ b/esphome/core/lwip_fast_select.h
@@ -0,0 +1,33 @@
+#pragma once
+
+// Fast socket monitoring for ESP32 (ESP-IDF LwIP)
+// Replaces lwip_select() with direct rcvevent reads and FreeRTOS task notifications.
+
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/// Initialize fast select — must be called from the main loop task during setup().
+/// Saves the current task handle for xTaskNotifyGive() wake notifications.
+void esphome_lwip_fast_select_init(void);
+
+/// Check if a LwIP socket has data ready via direct rcvevent read (~215 ns per socket).
+/// Uses lwip_socket_dbg_get_socket() — a direct array lookup without the refcount that
+/// get_socket()/done_socket() uses. Safe because the caller owns the socket lifetime:
+/// both has_data reads and socket close/unregister happen on the main loop thread.
+bool esphome_lwip_socket_has_data(int fd);
+
+/// Hook a socket's netconn callback to notify the main loop task on receive events.
+/// Wraps the original event_callback with one that also calls xTaskNotifyGive().
+/// Must be called from the main loop after socket creation.
+void esphome_lwip_hook_socket(int fd);
+
+/// Wake the main loop task from another FreeRTOS task — costs <1 us.
+/// NOT ISR-safe — must only be called from task context.
+void esphome_lwip_wake_main_loop(void);
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/esphome/core/time.cpp b/esphome/core/time.cpp
index 1aea18ac8d..73ba0a9be7 100644
--- a/esphome/core/time.cpp
+++ b/esphome/core/time.cpp
@@ -2,7 +2,6 @@
 #include "helpers.h"
 
 #include <algorithm>
-#include <cinttypes>
 
 namespace esphome {
 
@@ -67,58 +66,123 @@ std::string ESPTime::strftime(const char *format) {
 
 std::string ESPTime::strftime(const std::string &format) { return this->strftime(format.c_str()); }
 
-bool ESPTime::strptime(const char *time_to_parse, size_t len, ESPTime &esp_time) {
-  uint16_t year;
-  uint8_t month;
-  uint8_t day;
-  uint8_t hour;
-  uint8_t minute;
-  uint8_t second;
-  int num;
-  const int ilen = static_cast<int>(len);
-
-  if (sscanf(time_to_parse, "%04hu-%02hhu-%02hhu %02hhu:%02hhu:%02hhu %n", &year, &month, &day,  // NOLINT
-             &hour,                                                                              // NOLINT
-             &minute,                                                                            // NOLINT
-             &second, &num) == 6 &&                                                              // NOLINT
-      num == ilen) {
-    esp_time.year = year;
-    esp_time.month = month;
-    esp_time.day_of_month = day;
-    esp_time.hour = hour;
-    esp_time.minute = minute;
-    esp_time.second = second;
-  } else if (sscanf(time_to_parse, "%04hu-%02hhu-%02hhu %02hhu:%02hhu %n", &year, &month, &day,  // NOLINT
-                    &hour,                                                                       // NOLINT
-                    &minute, &num) == 5 &&                                                       // NOLINT
-             num == ilen) {
-    esp_time.year = year;
-    esp_time.month = month;
-    esp_time.day_of_month = day;
-    esp_time.hour = hour;
-    esp_time.minute = minute;
-    esp_time.second = 0;
-  } else if (sscanf(time_to_parse, "%02hhu:%02hhu:%02hhu %n", &hour, &minute, &second, &num) == 3 &&  // NOLINT
-             num == ilen) {
-    esp_time.hour = hour;
-    esp_time.minute = minute;
-    esp_time.second = second;
-  } else if (sscanf(time_to_parse, "%02hhu:%02hhu %n", &hour, &minute, &num) == 2 &&  // NOLINT
-             num == ilen) {
-    esp_time.hour = hour;
-    esp_time.minute = minute;
-    esp_time.second = 0;
-  } else if (sscanf(time_to_parse, "%04hu-%02hhu-%02hhu %n", &year, &month, &day, &num) == 3 &&  // NOLINT
-             num == ilen) {
-    esp_time.year = year;
-    esp_time.month = month;
-    esp_time.day_of_month = day;
-  } else {
-    return false;
+// Helper to parse exactly N digits, returns false if not enough digits
+static bool parse_digits(const char *&p, const char *end, int count, uint16_t &value) {
+  value = 0;
+  for (int i = 0; i < count; i++) {
+    if (p >= end || *p < '0' || *p > '9')
+      return false;
+    value = value * 10 + (*p - '0');
+    p++;
   }
   return true;
 }
 
+// Helper to check for expected character
+static bool expect_char(const char *&p, const char *end, char expected) {
+  if (p >= end || *p != expected)
+    return false;
+  p++;
+  return true;
+}
+
+bool ESPTime::strptime(const char *time_to_parse, size_t len, ESPTime &esp_time) {
+  // Supported formats:
+  //   YYYY-MM-DD HH:MM:SS (19 chars)
+  //   YYYY-MM-DD HH:MM    (16 chars)
+  //   YYYY-MM-DD          (10 chars)
+  //   HH:MM:SS            (8 chars)
+  //   HH:MM               (5 chars)
+
+  if (time_to_parse == nullptr || len == 0)
+    return false;
+
+  const char *p = time_to_parse;
+  const char *end = time_to_parse + len;
+  uint16_t v1, v2, v3, v4, v5, v6;
+
+  // Try date formats first (start with 4-digit year)
+  if (len >= 10 && time_to_parse[4] == '-') {
+    // YYYY-MM-DD...
+    if (!parse_digits(p, end, 4, v1))
+      return false;
+    if (!expect_char(p, end, '-'))
+      return false;
+    if (!parse_digits(p, end, 2, v2))
+      return false;
+    if (!expect_char(p, end, '-'))
+      return false;
+    if (!parse_digits(p, end, 2, v3))
+      return false;
+
+    esp_time.year = v1;
+    esp_time.month = v2;
+    esp_time.day_of_month = v3;
+
+    if (p == end) {
+      // YYYY-MM-DD (date only)
+      return true;
+    }
+
+    if (!expect_char(p, end, ' '))
+      return false;
+
+    // Continue with time part: HH:MM[:SS]
+    if (!parse_digits(p, end, 2, v4))
+      return false;
+    if (!expect_char(p, end, ':'))
+      return false;
+    if (!parse_digits(p, end, 2, v5))
+      return false;
+
+    esp_time.hour = v4;
+    esp_time.minute = v5;
+
+    if (p == end) {
+      // YYYY-MM-DD HH:MM
+      esp_time.second = 0;
+      return true;
+    }
+
+    if (!expect_char(p, end, ':'))
+      return false;
+    if (!parse_digits(p, end, 2, v6))
+      return false;
+
+    esp_time.second = v6;
+    return p == end;  // YYYY-MM-DD HH:MM:SS
+  }
+
+  // Try time-only formats (HH:MM[:SS])
+  if (len >= 5 && time_to_parse[2] == ':') {
+    if (!parse_digits(p, end, 2, v1))
+      return false;
+    if (!expect_char(p, end, ':'))
+      return false;
+    if (!parse_digits(p, end, 2, v2))
+      return false;
+
+    esp_time.hour = v1;
+    esp_time.minute = v2;
+
+    if (p == end) {
+      // HH:MM
+      esp_time.second = 0;
+      return true;
+    }
+
+    if (!expect_char(p, end, ':'))
+      return false;
+    if (!parse_digits(p, end, 2, v3))
+      return false;
+
+    esp_time.second = v3;
+    return p == end;  // HH:MM:SS
+  }
+
+  return false;
+}
+
 void ESPTime::increment_second() {
   this->timestamp++;
   if (!increment_time_value(this->second, 0, 60))
@@ -193,27 +257,67 @@ void ESPTime::recalc_timestamp_utc(bool use_day_of_year) {
 }
 
 void ESPTime::recalc_timestamp_local() {
-  struct tm tm;
+#ifdef USE_TIME_TIMEZONE
+  // Calculate timestamp as if fields were UTC
+  this->recalc_timestamp_utc(false);
+  if (this->timestamp == -1) {
+    return;  // Invalid time
+  }
 
-  tm.tm_year = this->year - 1900;
-  tm.tm_mon = this->month - 1;
-  tm.tm_mday = this->day_of_month;
-  tm.tm_hour = this->hour;
-  tm.tm_min = this->minute;
-  tm.tm_sec = this->second;
-  tm.tm_isdst = -1;
+  // Now convert from local to UTC by adding the offset
+  // POSIX: local = utc - offset, so utc = local + offset
+  const auto &tz = time::get_global_tz();
 
-  this->timestamp = mktime(&tm);
+  if (!tz.has_dst()) {
+    // No DST - just apply standard offset
+    this->timestamp += tz.std_offset_seconds;
+    return;
+  }
+
+  // Try both interpretations to match libc mktime() with tm_isdst=-1
+  // For ambiguous times (fall-back repeated hour), prefer standard time
+  // For invalid times (spring-forward skipped hour), libc normalizes forward
+  time_t utc_if_dst = this->timestamp + tz.dst_offset_seconds;
+  time_t utc_if_std = this->timestamp + tz.std_offset_seconds;
+
+  bool dst_valid = time::is_in_dst(utc_if_dst, tz);
+  bool std_valid = !time::is_in_dst(utc_if_std, tz);
+
+  if (dst_valid && std_valid) {
+    // Ambiguous time (repeated hour during fall-back) - prefer standard time
+    this->timestamp = utc_if_std;
+  } else if (dst_valid) {
+    // Only DST interpretation is valid
+    this->timestamp = utc_if_dst;
+  } else if (std_valid) {
+    // Only standard interpretation is valid
+    this->timestamp = utc_if_std;
+  } else {
+    // Invalid time (skipped hour during spring-forward)
+    // libc normalizes forward: 02:30 CST -> 08:30 UTC -> 03:30 CDT
+    // Using std offset achieves this since the UTC result falls during DST
+    this->timestamp = utc_if_std;
+  }
+#else
+  // No timezone support - treat as UTC
+  this->recalc_timestamp_utc(false);
+#endif
 }
 
 int32_t ESPTime::timezone_offset() {
+#ifdef USE_TIME_TIMEZONE
   time_t now = ::time(nullptr);
-  struct tm local_tm = *::localtime(&now);
-  local_tm.tm_isdst = 0;  // Cause mktime to ignore daylight saving time because we want to include it in the offset.
-  time_t local_time = mktime(&local_tm);
-  struct tm utc_tm = *::gmtime(&now);
-  time_t utc_time = mktime(&utc_tm);
-  return static_cast<int32_t>(local_time - utc_time);
+  const auto &tz = time::get_global_tz();
+  // POSIX offset is positive west, but we return offset to add to UTC to get local
+  // So we negate the POSIX offset
+  if (time::is_in_dst(now, tz)) {
+    return -tz.dst_offset_seconds;
+  }
+  return -tz.std_offset_seconds;
+#else
+  // No timezone support - no offset
+  return 0;
+#endif
 }
 
 bool ESPTime::operator<(const ESPTime &other) const { return this->timestamp < other.timestamp; }
diff --git a/esphome/core/time.h b/esphome/core/time.h
index d9ce86131c..874f0db4b4 100644
--- a/esphome/core/time.h
+++ b/esphome/core/time.h
@@ -7,6 +7,10 @@
 #include <span>
 #include <string>
 
+#ifdef USE_TIME_TIMEZONE
+#include "esphome/components/time/posix_tz.h"
+#endif
+
 namespace esphome {
 
 template<typename T> bool increment_time_value(T &current, uint16_t begin, uint16_t end);
@@ -105,11 +109,17 @@ struct ESPTime {
    * @return The generated ESPTime
    */
   static ESPTime from_epoch_local(time_t epoch) {
-    struct tm *c_tm = ::localtime(&epoch);
-    if (c_tm == nullptr) {
-      return ESPTime{};  // Return an invalid ESPTime
+#ifdef USE_TIME_TIMEZONE
+    struct tm local_tm;
+    if (time::epoch_to_local_tm(epoch, time::get_global_tz(), &local_tm)) {
+      return ESPTime::from_c_tm(&local_tm, epoch);
     }
-    return ESPTime::from_c_tm(c_tm, epoch);
+    // Fallback to UTC if conversion failed
+    return ESPTime::from_epoch_utc(epoch);
+#else
+    // No timezone support - return UTC (no TZ configured, localtime would return UTC anyway)
+    return ESPTime::from_epoch_utc(epoch);
+#endif
   }
   /** Convert an UTC epoch timestamp to a UTC time ESPTime instance.
    *
diff --git a/platformio.ini b/platformio.ini
index e35dce2228..16a1b18211 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -193,10 +193,10 @@ extra_scripts = post:esphome/components/esp32/post_build.py.script
 extends = common:arduino
 board_build.filesystem_size = 0.5m
 
-platform = https://github.com/maxgerhardt/platform-raspberrypi.git#v1.2.0-gcc12
+platform = https://github.com/maxgerhardt/platform-raspberrypi.git#v1.4.0-gcc14-arduinopico460
 platform_packages =
     ; earlephilhower/framework-arduinopico@~1.20602.0 ; Cannot use the platformio package until old releases stop getting deleted
-    earlephilhower/framework-arduinopico@https://github.com/earlephilhower/arduino-pico/releases/download/3.9.4/rp2040-3.9.4.zip
+    earlephilhower/framework-arduinopico@https://github.com/earlephilhower/arduino-pico/releases/download/5.5.0/rp2040-5.5.0.zip
 
 framework = arduino
 lib_deps =
diff --git a/requirements.txt b/requirements.txt
index d22097b3ca..95e3710f9e 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -12,7 +12,7 @@ platformio==6.1.19
 esptool==5.2.0
 click==8.1.7
 esphome-dashboard==20260210.0
-aioesphomeapi==44.1.0
+aioesphomeapi==44.2.0
 zeroconf==0.148.0
 puremagic==1.30
 ruamel.yaml==0.19.1 # dashboard_import
diff --git a/requirements_test.txt b/requirements_test.txt
index 3e5dc8a90c..88a38ffa99 100644
--- a/requirements_test.txt
+++ b/requirements_test.txt
@@ -1,6 +1,6 @@
 pylint==4.0.5
 flake8==7.3.0  # also change in .pre-commit-config.yaml when updating
-ruff==0.15.2  # also change in .pre-commit-config.yaml when updating
+ruff==0.15.3  # also change in .pre-commit-config.yaml when updating
 pyupgrade==3.21.2  # also change in .pre-commit-config.yaml when updating
 pre-commit
 
diff --git a/script/cpp_unit_test.py b/script/cpp_unit_test.py
index e97b5bd7b0..78b65092ae 100755
--- a/script/cpp_unit_test.py
+++ b/script/cpp_unit_test.py
@@ -66,6 +66,7 @@ def create_test_config(config_name: str, includes: list[str]) -> dict:
                 ],
                 "build_flags": [
                     "-Og",  # optimize for debug
+                    "-DUSE_TIME_TIMEZONE",  # enable timezone code paths for testing
                 ],
                 "debug_build_flags": [  # only for debug builds
                     "-g3",  # max debug info
diff --git a/tests/components/esp_ldo/test.esp32-p4-idf.yaml b/tests/components/esp_ldo/test.esp32-p4-idf.yaml
index 38bd6ac411..31d2b8cf7a 100644
--- a/tests/components/esp_ldo/test.esp32-p4-idf.yaml
+++ b/tests/components/esp_ldo/test.esp32-p4-idf.yaml
@@ -3,10 +3,13 @@ esp_ldo:
     channel: 3
     voltage: 2.5V
     adjustable: true
-  - id: ldo_4
+  - id: ldo_4_passthrough
     channel: 4
-    voltage: 2.0V
-    setup_priority: 900
+    voltage: passthrough
+  - id: ldo_1_internal
+    channel: 1
+    voltage: 1.8V
+    allow_internal_channel: true
 
 esphome:
   on_boot:
diff --git a/tests/components/socket/test.bk72xx-ard.yaml b/tests/components/socket/test.bk72xx-ard.yaml
new file mode 100644
index 0000000000..dade44d145
--- /dev/null
+++ b/tests/components/socket/test.bk72xx-ard.yaml
@@ -0,0 +1 @@
+<<: !include common.yaml
diff --git a/tests/components/socket/test.ln882x-ard.yaml b/tests/components/socket/test.ln882x-ard.yaml
new file mode 100644
index 0000000000..dade44d145
--- /dev/null
+++ b/tests/components/socket/test.ln882x-ard.yaml
@@ -0,0 +1 @@
+<<: !include common.yaml
diff --git a/tests/components/socket/test.rtl87xx-ard.yaml b/tests/components/socket/test.rtl87xx-ard.yaml
new file mode 100644
index 0000000000..dade44d145
--- /dev/null
+++ b/tests/components/socket/test.rtl87xx-ard.yaml
@@ -0,0 +1 @@
+<<: !include common.yaml
diff --git a/tests/components/socket/test_wake_loop_threadsafe.py b/tests/components/socket/test_wake_loop_threadsafe.py
index a40b6068a8..28b4ee564f 100644
--- a/tests/components/socket/test_wake_loop_threadsafe.py
+++ b/tests/components/socket/test_wake_loop_threadsafe.py
@@ -1,9 +1,21 @@
 from esphome.components import socket
+from esphome.const import (
+    KEY_CORE,
+    KEY_TARGET_PLATFORM,
+    PLATFORM_ESP32,
+    PLATFORM_ESP8266,
+)
 from esphome.core import CORE
 
 
+def _setup_platform(platform=PLATFORM_ESP8266) -> None:
+    """Set up CORE.data with a platform for testing."""
+    CORE.data[KEY_CORE] = {KEY_TARGET_PLATFORM: platform}
+
+
 def test_require_wake_loop_threadsafe__first_call() -> None:
     """Test that first call sets up define and consumes socket."""
+    _setup_platform()
     CORE.config = {"wifi": True}
     socket.require_wake_loop_threadsafe()
 
@@ -32,6 +44,7 @@ def test_require_wake_loop_threadsafe__idempotent() -> None:
 
 def test_require_wake_loop_threadsafe__multiple_calls() -> None:
     """Test that multiple calls only set up once."""
+    _setup_platform()
     # Call three times
     CORE.config = {"openthread": True}
     socket.require_wake_loop_threadsafe()
@@ -75,3 +88,29 @@ def test_require_wake_loop_threadsafe__no_networking_does_not_consume_socket() -
     udp_consumers = CORE.data.get(socket.KEY_SOCKET_CONSUMERS_UDP, {})
     assert "socket.wake_loop_threadsafe" not in udp_consumers
     assert udp_consumers == initial_udp
+
+
+def test_require_wake_loop_threadsafe__esp32_no_udp_socket() -> None:
+    """Test that ESP32 uses task notifications instead of UDP socket."""
+    _setup_platform(PLATFORM_ESP32)
+    CORE.config = {"wifi": True}
+    socket.require_wake_loop_threadsafe()
+
+    # Verify the define was added
+    assert CORE.data[socket.KEY_WAKE_LOOP_THREADSAFE_REQUIRED] is True
+    assert any(d.name == "USE_WAKE_LOOP_THREADSAFE" for d in CORE.defines)
+
+    # Verify no UDP socket was consumed (ESP32 uses FreeRTOS task notifications)
+    udp_consumers = CORE.data.get(socket.KEY_SOCKET_CONSUMERS_UDP, {})
+    assert "socket.wake_loop_threadsafe" not in udp_consumers
+
+
+def test_require_wake_loop_threadsafe__non_esp32_consumes_udp_socket() -> None:
+    """Test that non-ESP32 platforms consume a UDP socket for wake notifications."""
+    _setup_platform(PLATFORM_ESP8266)
+    CORE.config = {"wifi": True}
+    socket.require_wake_loop_threadsafe()
+
+    # Verify UDP socket was consumed
+    udp_consumers = CORE.data.get(socket.KEY_SOCKET_CONSUMERS_UDP, {})
+    assert udp_consumers.get("socket.wake_loop_threadsafe") == 1
diff --git a/tests/components/time/posix_tz_parser.cpp b/tests/components/time/posix_tz_parser.cpp
new file mode 100644
index 0000000000..d1747ef5b1
--- /dev/null
+++ b/tests/components/time/posix_tz_parser.cpp
@@ -0,0 +1,1275 @@
+// Tests for the POSIX TZ parser, time conversion functions, and ESPTime::strptime.
+//
+// Most tests here cover the C++ POSIX TZ string parser (parse_posix_tz), which is
+// bridge code for backward compatibility — it will be removed before ESPHome 2026.9.0.
+// After https://github.com/esphome/esphome/pull/14233 merges, the parser is solely
+// used to handle timezone strings from Home Assistant clients older than 2026.3.0
+// that haven't been updated to send the pre-parsed ParsedTimezone protobuf struct.
+// See https://github.com/esphome/backlog/issues/91
+//
+// The epoch_to_local_tm, is_in_dst, and ESPTime::strptime tests cover conversion
+// functions that will remain permanently.
+
+// Enable USE_TIME_TIMEZONE for tests
+#define USE_TIME_TIMEZONE
+
+#include <gtest/gtest.h>
+#include <cstdlib>
+#include <ctime>
+#include "esphome/components/time/posix_tz.h"
+#include "esphome/core/time.h"
+
+namespace esphome::time::testing {
+
+// Helper to create UTC epoch from date/time components (for test readability)
+static time_t make_utc(int year, int month, int day, int hour = 0, int min = 0, int sec = 0) {
+  int64_t days = 0;
+  for (int y = 1970; y < year; y++) {
+    days += (y % 4 == 0 && (y % 100 != 0 || y % 400 == 0)) ? 366 : 365;
+  }
+  static const int DAYS_BEFORE[] = {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334};
+  days += DAYS_BEFORE[month - 1];
+  if (month > 2 && (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0)))
+    days++;  // Leap year adjustment
+  days += day - 1;
+  return days * 86400 + hour * 3600 + min * 60 + sec;
+}
+
+// ============================================================================
+// Basic TZ string parsing tests
+// ============================================================================
+
+TEST(PosixTzParser, ParseSimpleOffsetEST5) {
+  ParsedTimezone tz;
+  ASSERT_TRUE(parse_posix_tz("EST5", tz));
+  EXPECT_EQ(tz.std_offset_seconds, 5 * 3600);  // +5 hours (west of UTC)
+  EXPECT_FALSE(tz.has_dst());
+}
+
+TEST(PosixTzParser, ParseNegativeOffsetCET) {
+  ParsedTimezone tz;
+  ASSERT_TRUE(parse_posix_tz("CET-1", tz));
+  EXPECT_EQ(tz.std_offset_seconds, -1 * 3600);  // -1 hour (east of UTC)
+  EXPECT_FALSE(tz.has_dst());
+}
+
+TEST(PosixTzParser, ParseExplicitPositiveOffset) {
+  ParsedTimezone tz;
+  ASSERT_TRUE(parse_posix_tz("TEST+5", tz));
+  EXPECT_EQ(tz.std_offset_seconds, 5 * 3600);
+  EXPECT_FALSE(tz.has_dst());
+}
+
+TEST(PosixTzParser, ParseZeroOffset) {
+  ParsedTimezone tz;
+  ASSERT_TRUE(parse_posix_tz("UTC0", tz));
+  EXPECT_EQ(tz.std_offset_seconds, 0);
+  EXPECT_FALSE(tz.has_dst());
+}
+
+TEST(PosixTzParser, ParseUSEasternWithDST) {
+  ParsedTimezone tz;
+  ASSERT_TRUE(parse_posix_tz("EST5EDT,M3.2.0,M11.1.0", tz));
+  EXPECT_EQ(tz.std_offset_seconds, 5 * 3600);
+  EXPECT_EQ(tz.dst_offset_seconds, 4 * 3600);  // Default: STD - 1hr
+  EXPECT_TRUE(tz.has_dst());
+  EXPECT_EQ(tz.dst_start.month, 3);
+  EXPECT_EQ(tz.dst_start.week, 2);
+  EXPECT_EQ(tz.dst_start.day_of_week, 0);          // Sunday
+  EXPECT_EQ(tz.dst_start.time_seconds, 2 * 3600);  // Default 2:00 AM
+  EXPECT_EQ(tz.dst_end.month, 11);
+  EXPECT_EQ(tz.dst_end.week, 1);
+  EXPECT_EQ(tz.dst_end.day_of_week, 0);
+}
+
+TEST(PosixTzParser, ParseUSCentralWithTime) {
+  ParsedTimezone tz;
+  ASSERT_TRUE(parse_posix_tz("CST6CDT,M3.2.0/2,M11.1.0/2", tz));
+  EXPECT_EQ(tz.std_offset_seconds, 6 * 3600);
+  EXPECT_EQ(tz.dst_offset_seconds, 5 * 3600);
+  EXPECT_EQ(tz.dst_start.time_seconds, 2 * 3600);  // 2:00 AM
+  EXPECT_EQ(tz.dst_end.time_seconds, 2 * 3600);
+}
+
+TEST(PosixTzParser, ParseEuropeBerlin) {
+  ParsedTimezone tz;
+  ASSERT_TRUE(parse_posix_tz("CET-1CEST,M3.5.0,M10.5.0/3", tz));
+  EXPECT_EQ(tz.std_offset_seconds, -1 * 3600);
+  EXPECT_EQ(tz.dst_offset_seconds, -2 * 3600);  // Default: STD - 1hr
+  EXPECT_TRUE(tz.has_dst());
+  EXPECT_EQ(tz.dst_start.month, 3);
+  EXPECT_EQ(tz.dst_start.week, 5);  // Last week
+  EXPECT_EQ(tz.dst_end.month, 10);
+  EXPECT_EQ(tz.dst_end.week, 5);                 // Last week
+  EXPECT_EQ(tz.dst_end.time_seconds, 3 * 3600);  // 3:00 AM
+}
+
+TEST(PosixTzParser, ParseNewZealand) {
+  ParsedTimezone tz;
+  // Southern hemisphere - DST starts in Sept, ends in April
+  ASSERT_TRUE(parse_posix_tz("NZST-12NZDT,M9.5.0,M4.1.0/3", tz));
+  EXPECT_EQ(tz.std_offset_seconds, -12 * 3600);
+  EXPECT_EQ(tz.dst_offset_seconds, -13 * 3600);  // Default: STD - 1hr
+  EXPECT_TRUE(tz.has_dst());
+  EXPECT_EQ(tz.dst_start.month, 9);  // September
+  EXPECT_EQ(tz.dst_end.month, 4);    // April
+}
+
+TEST(PosixTzParser, ParseExplicitDstOffset) {
+  ParsedTimezone tz;
+  // Some places have non-standard DST offsets
+  ASSERT_TRUE(parse_posix_tz("TEST5DST4,M3.2.0,M11.1.0", tz));
+  EXPECT_EQ(tz.std_offset_seconds, 5 * 3600);
+  EXPECT_EQ(tz.dst_offset_seconds, 4 * 3600);
+  EXPECT_TRUE(tz.has_dst());
+}
+
+// ============================================================================
+// Angle-bracket notation tests (espressif/newlib-esp32#8)
+// ============================================================================
+
+TEST(PosixTzParser, ParseAngleBracketPositive) {
+  // Format: <+07>-7 means UTC+7 (name is "+07", offset is -7 hours east)
+  ParsedTimezone tz;
+  ASSERT_TRUE(parse_posix_tz("<+07>-7", tz));
+  EXPECT_EQ(tz.std_offset_seconds, -7 * 3600);  // -7 = 7 hours east of UTC
+  EXPECT_FALSE(tz.has_dst());
+}
+
+TEST(PosixTzParser, ParseAngleBracketNegative) {
+  // <-03>3 means UTC-3 (name is "-03", offset is 3 hours west)
+  ParsedTimezone tz;
+  ASSERT_TRUE(parse_posix_tz("<-03>3", tz));
+  EXPECT_EQ(tz.std_offset_seconds, 3 * 3600);
+  EXPECT_FALSE(tz.has_dst());
+}
+
+TEST(PosixTzParser, ParseAngleBracketWithDST) {
+  // <+10>-10<+11>,M10.1.0,M4.1.0/3 (Australia/Sydney style)
+  ParsedTimezone tz;
+  ASSERT_TRUE(parse_posix_tz("<+10>-10<+11>,M10.1.0,M4.1.0/3", tz));
+  EXPECT_EQ(tz.std_offset_seconds, -10 * 3600);
+  EXPECT_EQ(tz.dst_offset_seconds, -11 * 3600);
+  EXPECT_TRUE(tz.has_dst());
+  EXPECT_EQ(tz.dst_start.month, 10);
+  EXPECT_EQ(tz.dst_end.month, 4);
+}
+
+TEST(PosixTzParser, ParseAngleBracketNamed) {
+  // <AEST>-10 (Australian Eastern Standard Time)
+  ParsedTimezone tz;
+  ASSERT_TRUE(parse_posix_tz("<AEST>-10", tz));
+  EXPECT_EQ(tz.std_offset_seconds, -10 * 3600);
+  EXPECT_FALSE(tz.has_dst());
+}
+
+TEST(PosixTzParser, ParseAngleBracketWithMinutes) {
+  // <+0545>-5:45 (Nepal)
+  ParsedTimezone tz;
+  ASSERT_TRUE(parse_posix_tz("<+0545>-5:45", tz));
+  EXPECT_EQ(tz.std_offset_seconds, -(5 * 3600 + 45 * 60));
+  EXPECT_FALSE(tz.has_dst());
+}
+
+// ============================================================================
+// Half-hour and unusual offset tests
+// ============================================================================
+
+TEST(PosixTzParser, ParseOffsetWithMinutesIndia) {
+  ParsedTimezone tz;
+  // India: UTC+5:30
+  ASSERT_TRUE(parse_posix_tz("IST-5:30", tz));
+  EXPECT_EQ(tz.std_offset_seconds, -(5 * 3600 + 30 * 60));
+  EXPECT_FALSE(tz.has_dst());
+}
+
+TEST(PosixTzParser, ParseOffsetWithMinutesNepal) {
+  ParsedTimezone tz;
+  // Nepal: UTC+5:45
+  ASSERT_TRUE(parse_posix_tz("NPT-5:45", tz));
+  EXPECT_EQ(tz.std_offset_seconds, -(5 * 3600 + 45 * 60));
+  EXPECT_FALSE(tz.has_dst());
+}
+
+TEST(PosixTzParser, ParseOffsetWithSeconds) {
+  ParsedTimezone tz;
+  // Unusual but valid: offset with seconds
+  ASSERT_TRUE(parse_posix_tz("TEST-1:30:30", tz));
+  EXPECT_EQ(tz.std_offset_seconds, -(1 * 3600 + 30 * 60 + 30));
+}
+
+TEST(PosixTzParser, ParseChathamIslands) {
+  // Chatham Islands: UTC+12:45 with DST
+  ParsedTimezone tz;
+  ASSERT_TRUE(parse_posix_tz("<+1245>-12:45<+1345>,M9.5.0/2:45,M4.1.0/3:45", tz));
+  EXPECT_EQ(tz.std_offset_seconds, -(12 * 3600 + 45 * 60));
+  EXPECT_EQ(tz.dst_offset_seconds, -(13 * 3600 + 45 * 60));
+  EXPECT_TRUE(tz.has_dst());
+}
+
+// ============================================================================
+// Invalid input tests
+// ============================================================================
+
+TEST(PosixTzParser, ParseEmptyStringFails) {
+  ParsedTimezone tz;
+  EXPECT_FALSE(parse_posix_tz("", tz));
+}
+
+TEST(PosixTzParser, ParseNullFails) {
+  ParsedTimezone tz;
+  EXPECT_FALSE(parse_posix_tz(nullptr, tz));
+}
+
+TEST(PosixTzParser, ParseShortNameFails) {
+  ParsedTimezone tz;
+  // TZ name must be at least 3 characters
+  EXPECT_FALSE(parse_posix_tz("AB5", tz));
+}
+
+TEST(PosixTzParser, ParseMissingOffsetFails) {
+  ParsedTimezone tz;
+  EXPECT_FALSE(parse_posix_tz("EST", tz));
+}
+
+TEST(PosixTzParser, ParseUnterminatedBracketFails) {
+  ParsedTimezone tz;
+  EXPECT_FALSE(parse_posix_tz("<+07-7", tz));  // Missing closing >
+}
+
+// ============================================================================
+// J-format and plain day number tests
+// ============================================================================
+
+TEST(PosixTzParser, ParseJFormatBasic) {
+  ParsedTimezone tz;
+  // J format: Julian day 1-365, not counting Feb 29
+  ASSERT_TRUE(parse_posix_tz("EST5EDT,J60,J305", tz));
+  EXPECT_TRUE(tz.has_dst());
+  EXPECT_EQ(tz.dst_start.type, DSTRuleType::JULIAN_NO_LEAP);
+  EXPECT_EQ(tz.dst_start.day, 60);  // March 1
+  EXPECT_EQ(tz.dst_end.type, DSTRuleType::JULIAN_NO_LEAP);
+  EXPECT_EQ(tz.dst_end.day, 305);  // November 1
+}
+
+TEST(PosixTzParser, ParseJFormatWithTime) {
+  ParsedTimezone tz;
+  ASSERT_TRUE(parse_posix_tz("EST5EDT,J60/2,J305/2", tz));
+  EXPECT_EQ(tz.dst_start.day, 60);
+  EXPECT_EQ(tz.dst_start.time_seconds, 2 * 3600);
+  EXPECT_EQ(tz.dst_end.day, 305);
+  EXPECT_EQ(tz.dst_end.time_seconds, 2 * 3600);
+}
+
+TEST(PosixTzParser, ParsePlainDayNumber) {
+  ParsedTimezone tz;
+  // Plain format: day 0-365, counting Feb 29 in leap years
+  ASSERT_TRUE(parse_posix_tz("EST5EDT,59,304", tz));
+  EXPECT_TRUE(tz.has_dst());
+  EXPECT_EQ(tz.dst_start.type, DSTRuleType::DAY_OF_YEAR);
+  EXPECT_EQ(tz.dst_start.day, 59);
+  EXPECT_EQ(tz.dst_end.type, DSTRuleType::DAY_OF_YEAR);
+  EXPECT_EQ(tz.dst_end.day, 304);
+}
+
+TEST(PosixTzParser, JFormatInvalidDayZero) {
+  ParsedTimezone tz;
+  // J format day must be 1-365, not 0
+  EXPECT_FALSE(parse_posix_tz("EST5EDT,J0,J305", tz));
+}
+
+TEST(PosixTzParser, JFormatInvalidDay366) {
+  ParsedTimezone tz;
+  // J format day must be 1-365
+  EXPECT_FALSE(parse_posix_tz("EST5EDT,J366,J305", tz));
+}
+
+TEST(PosixTzParser, ParsePlainDayNumberWithTime) {
+  ParsedTimezone tz;
+  ASSERT_TRUE(parse_posix_tz("EST5EDT,59/3,304/1:30", tz));
+  EXPECT_EQ(tz.dst_start.day, 59);
+  EXPECT_EQ(tz.dst_start.time_seconds, 3 * 3600);
+  EXPECT_EQ(tz.dst_end.day, 304);
+  EXPECT_EQ(tz.dst_end.time_seconds, 1 * 3600 + 30 * 60);
+}
+
+TEST(PosixTzParser, PlainDayInvalidDay366) {
+  ParsedTimezone tz;
+  // Plain format day must be 0-365
+  EXPECT_FALSE(parse_posix_tz("EST5EDT,366,304", tz));
+}
+
+// ============================================================================
+// Transition time edge cases (POSIX V3 allows -167 to +167 hours)
+// ============================================================================
+
+TEST(PosixTzParser, NegativeTransitionTime) {
+  ParsedTimezone tz;
+  // Negative transition time: /-1 means 11 PM (23:00) the previous day
+  ASSERT_TRUE(parse_posix_tz("EST5EDT,M3.2.0/-1,M11.1.0/2", tz));
+  EXPECT_EQ(tz.dst_start.time_seconds, -1 * 3600);  // -1 hour = 11 PM previous day
+  EXPECT_EQ(tz.dst_end.time_seconds, 2 * 3600);
+}
+
+TEST(PosixTzParser, NegativeTransitionTimeWithMinutes) {
+  ParsedTimezone tz;
+  // /-1:30 means 10:30 PM the previous day
+  ASSERT_TRUE(parse_posix_tz("EST5EDT,M3.2.0/-1:30,M11.1.0", tz));
+  EXPECT_EQ(tz.dst_start.time_seconds, -(1 * 3600 + 30 * 60));
+}
+
+TEST(PosixTzParser, LargeTransitionTime) {
+  ParsedTimezone tz;
+  // POSIX V3 allows transition times from -167 to +167 hours
+  // /25 means 1:00 AM the next day
+  ASSERT_TRUE(parse_posix_tz("EST5EDT,M3.2.0/25,M11.1.0", tz));
+  EXPECT_EQ(tz.dst_start.time_seconds, 25 * 3600);
+}
+
+TEST(PosixTzParser, MaxTransitionTime167Hours) {
+  ParsedTimezone tz;
+  // Maximum allowed transition time per POSIX V3
+  ASSERT_TRUE(parse_posix_tz("EST5EDT,M3.2.0/167,M11.1.0", tz));
+  EXPECT_EQ(tz.dst_start.time_seconds, 167 * 3600);
+}
+
+TEST(PosixTzParser, TransitionTimeWithHoursMinutesSeconds) {
+  ParsedTimezone tz;
+  ASSERT_TRUE(parse_posix_tz("EST5EDT,M3.2.0/2:30:45,M11.1.0", tz));
+  EXPECT_EQ(tz.dst_start.time_seconds, 2 * 3600 + 30 * 60 + 45);
+}
+
+// ============================================================================
+// Invalid M format tests
+// ============================================================================
+
+TEST(PosixTzParser, MFormatInvalidMonth13) {
+  ParsedTimezone tz;
+  // Month must be 1-12
+  EXPECT_FALSE(parse_posix_tz("EST5EDT,M13.1.0,M11.1.0", tz));
+}
+
+TEST(PosixTzParser, MFormatInvalidMonth0) {
+  ParsedTimezone tz;
+  // Month must be 1-12
+  EXPECT_FALSE(parse_posix_tz("EST5EDT,M0.1.0,M11.1.0", tz));
+}
+
+TEST(PosixTzParser, MFormatInvalidWeek6) {
+  ParsedTimezone tz;
+  // Week must be 1-5
+  EXPECT_FALSE(parse_posix_tz("EST5EDT,M3.6.0,M11.1.0", tz));
+}
+
+TEST(PosixTzParser, MFormatInvalidWeek0) {
+  ParsedTimezone tz;
+  // Week must be 1-5
+  EXPECT_FALSE(parse_posix_tz("EST5EDT,M3.0.0,M11.1.0", tz));
+}
+
+TEST(PosixTzParser, MFormatInvalidDayOfWeek7) {
+  ParsedTimezone tz;
+  // Day of week must be 0-6
+  EXPECT_FALSE(parse_posix_tz("EST5EDT,M3.2.7,M11.1.0", tz));
+}
+
+TEST(PosixTzParser, MissingEndRule) {
+  ParsedTimezone tz;
+  // POSIX requires both start and end rules if any rules are specified
+  EXPECT_FALSE(parse_posix_tz("EST5EDT,M3.2.0", tz));
+}
+
+TEST(PosixTzParser, MissingEndRuleJFormat) {
+  ParsedTimezone tz;
+  // POSIX requires both start and end rules if any rules are specified
+  EXPECT_FALSE(parse_posix_tz("EST5EDT,J60", tz));
+}
+
+TEST(PosixTzParser, MissingEndRulePlainDay) {
+  ParsedTimezone tz;
+  // POSIX requires both start and end rules if any rules are specified
+  EXPECT_FALSE(parse_posix_tz("EST5EDT,60", tz));
+}
+
+TEST(PosixTzParser, LowercaseMFormat) {
+  ParsedTimezone tz;
+  // Lowercase 'm' should be accepted
+  ASSERT_TRUE(parse_posix_tz("EST5EDT,m3.2.0,m11.1.0", tz));
+  EXPECT_TRUE(tz.has_dst());
+  EXPECT_EQ(tz.dst_start.month, 3);
+  EXPECT_EQ(tz.dst_end.month, 11);
+}
+
+TEST(PosixTzParser, LowercaseJFormat) {
+  ParsedTimezone tz;
+  // Lowercase 'j' should be accepted
+  ASSERT_TRUE(parse_posix_tz("EST5EDT,j60,j305", tz));
+  EXPECT_EQ(tz.dst_start.type, DSTRuleType::JULIAN_NO_LEAP);
+  EXPECT_EQ(tz.dst_start.day, 60);
+}
+
+TEST(PosixTzParser, DstNameWithoutRules) {
+  ParsedTimezone tz;
+  // DST name present but no rules - treat as no DST since we can't determine transitions
+  ASSERT_TRUE(parse_posix_tz("EST5EDT", tz));
+  EXPECT_FALSE(tz.has_dst());
+  EXPECT_EQ(tz.std_offset_seconds, 5 * 3600);
+}
+
+TEST(PosixTzParser, TrailingCharactersIgnored) {
+  ParsedTimezone tz;
+  // Trailing characters after valid TZ should be ignored (parser stops at end of valid input)
+  // This matches libc behavior
+  ASSERT_TRUE(parse_posix_tz("EST5 extra garbage here", tz));
+  EXPECT_EQ(tz.std_offset_seconds, 5 * 3600);
+  EXPECT_FALSE(tz.has_dst());
+}
+
+TEST(PosixTzParser, PlainDay365LeapYear) {
+  // Day 365 in leap year is Dec 31
+  int month, day;
+  internal::day_of_year_to_month_day(365, 2024, month, day);
+  EXPECT_EQ(month, 12);
+  EXPECT_EQ(day, 31);
+}
+
+TEST(PosixTzParser, PlainDay364NonLeapYear) {
+  // Day 364 (0-indexed) is Dec 31 in non-leap year (last valid day)
+  int month, day;
+  internal::day_of_year_to_month_day(364, 2025, month, day);
+  EXPECT_EQ(month, 12);
+  EXPECT_EQ(day, 31);
+}
+
+// ============================================================================
+// Large offset tests
+// ============================================================================
+
+TEST(PosixTzParser, MaxOffset14Hours) {
+  ParsedTimezone tz;
+  // Line Islands (Kiribati) is UTC+14, the maximum offset
+  ASSERT_TRUE(parse_posix_tz("<+14>-14", tz));
+  EXPECT_EQ(tz.std_offset_seconds, -14 * 3600);
+}
+
+TEST(PosixTzParser, MaxNegativeOffset12Hours) {
+  ParsedTimezone tz;
+  // Baker Island is UTC-12
+  ASSERT_TRUE(parse_posix_tz("<-12>12", tz));
+  EXPECT_EQ(tz.std_offset_seconds, 12 * 3600);
+}
+
+// ============================================================================
+// Helper function tests
+// ============================================================================
+
+TEST(PosixTzParser, JulianDay60IsMarch1) {
+  // J60 is always March 1 (J format ignores leap years by design)
+  int month, day;
+  internal::julian_to_month_day(60, month, day);
+  EXPECT_EQ(month, 3);
+  EXPECT_EQ(day, 1);
+}
+
+TEST(PosixTzParser, DayOfYear59DiffersByLeap) {
+  int month, day;
+  // Day 59 in leap year is Feb 29
+  internal::day_of_year_to_month_day(59, 2024, month, day);
+  EXPECT_EQ(month, 2);
+  EXPECT_EQ(day, 29);
+  // Day 59 in non-leap year is March 1
+  internal::day_of_year_to_month_day(59, 2025, month, day);
+  EXPECT_EQ(month, 3);
+  EXPECT_EQ(day, 1);
+}
+
+TEST(PosixTzParser, DayOfWeekKnownDates) {
+  // January 1, 1970 was Thursday (4)
+  EXPECT_EQ(internal::day_of_week(1970, 1, 1), 4);
+  // January 1, 2000 was Saturday (6)
+  EXPECT_EQ(internal::day_of_week(2000, 1, 1), 6);
+  // March 8, 2026 is Sunday (0) - US DST start
+  EXPECT_EQ(internal::day_of_week(2026, 3, 8), 0);
+}
+
+TEST(PosixTzParser, LeapYearDetection) {
+  EXPECT_FALSE(internal::is_leap_year(1900));  // Divisible by 100 but not 400
+  EXPECT_TRUE(internal::is_leap_year(2000));   // Divisible by 400
+  EXPECT_TRUE(internal::is_leap_year(2024));   // Divisible by 4
+  EXPECT_FALSE(internal::is_leap_year(2025));  // Not divisible by 4
+}
+
+TEST(PosixTzParser, JulianDay1IsJan1) {
+  int month, day;
+  internal::julian_to_month_day(1, month, day);
+  EXPECT_EQ(month, 1);
+  EXPECT_EQ(day, 1);
+}
+
+TEST(PosixTzParser, JulianDay31IsJan31) {
+  int month, day;
+  internal::julian_to_month_day(31, month, day);
+  EXPECT_EQ(month, 1);
+  EXPECT_EQ(day, 31);
+}
+
+TEST(PosixTzParser, JulianDay32IsFeb1) {
+  int month, day;
+  internal::julian_to_month_day(32, month, day);
+  EXPECT_EQ(month, 2);
+  EXPECT_EQ(day, 1);
+}
+
+TEST(PosixTzParser, JulianDay59IsFeb28) {
+  int month, day;
+  internal::julian_to_month_day(59, month, day);
+  EXPECT_EQ(month, 2);
+  EXPECT_EQ(day, 28);
+}
+
+TEST(PosixTzParser, JulianDay365IsDec31) {
+  int month, day;
+  internal::julian_to_month_day(365, month, day);
+  EXPECT_EQ(month, 12);
+  EXPECT_EQ(day, 31);
+}
+
+TEST(PosixTzParser, DayOfYear0IsJan1) {
+  int month, day;
+  internal::day_of_year_to_month_day(0, 2025, month, day);
+  EXPECT_EQ(month, 1);
+  EXPECT_EQ(day, 1);
+}
+
+TEST(PosixTzParser, DaysInMonthRegular) {
+  // Test all 12 months to ensure switch coverage
+  EXPECT_EQ(internal::days_in_month(2025, 1), 31);   // Jan - default case
+  EXPECT_EQ(internal::days_in_month(2025, 2), 28);   // Feb - case 2
+  EXPECT_EQ(internal::days_in_month(2025, 3), 31);   // Mar - default case
+  EXPECT_EQ(internal::days_in_month(2025, 4), 30);   // Apr - case 4
+  EXPECT_EQ(internal::days_in_month(2025, 5), 31);   // May - default case
+  EXPECT_EQ(internal::days_in_month(2025, 6), 30);   // Jun - case 6
+  EXPECT_EQ(internal::days_in_month(2025, 7), 31);   // Jul - default case
+  EXPECT_EQ(internal::days_in_month(2025, 8), 31);   // Aug - default case
+  EXPECT_EQ(internal::days_in_month(2025, 9), 30);   // Sep - case 9
+  EXPECT_EQ(internal::days_in_month(2025, 10), 31);  // Oct - default case
+  EXPECT_EQ(internal::days_in_month(2025, 11), 30);  // Nov - case 11
+  EXPECT_EQ(internal::days_in_month(2025, 12), 31);  // Dec - default case
+}
+
+TEST(PosixTzParser, DaysInMonthLeapYear) {
+  EXPECT_EQ(internal::days_in_month(2024, 2), 29);
+  EXPECT_EQ(internal::days_in_month(2025, 2), 28);
+}
+
+// ============================================================================
+// DST transition calculation tests
+// ============================================================================
+
+TEST(PosixTzParser, DstStartUSEastern2026) {
+  // March 8, 2026 is 2nd Sunday of March
+  ParsedTimezone tz;
+  parse_posix_tz("EST5EDT,M3.2.0/2,M11.1.0/2", tz);
+
+  time_t dst_start = internal::calculate_dst_transition(2026, tz.dst_start, tz.std_offset_seconds);
+  struct tm tm;
+  internal::epoch_to_tm_utc(dst_start, &tm);
+
+  // At 2:00 AM EST (UTC-5), so 7:00 AM UTC
+  EXPECT_EQ(tm.tm_year + 1900, 2026);
+  EXPECT_EQ(tm.tm_mon + 1, 3);  // March
+  EXPECT_EQ(tm.tm_mday, 8);     // 8th
+  EXPECT_EQ(tm.tm_hour, 7);     // 7:00 UTC = 2:00 EST
+}
+
+TEST(PosixTzParser, DstEndUSEastern2026) {
+  // November 1, 2026 is 1st Sunday of November
+  ParsedTimezone tz;
+  parse_posix_tz("EST5EDT,M3.2.0/2,M11.1.0/2", tz);
+
+  time_t dst_end = internal::calculate_dst_transition(2026, tz.dst_end, tz.dst_offset_seconds);
+  struct tm tm;
+  internal::epoch_to_tm_utc(dst_end, &tm);
+
+  // At 2:00 AM EDT (UTC-4), so 6:00 AM UTC
+  EXPECT_EQ(tm.tm_year + 1900, 2026);
+  EXPECT_EQ(tm.tm_mon + 1, 11);  // November
+  EXPECT_EQ(tm.tm_mday, 1);      // 1st
+  EXPECT_EQ(tm.tm_hour, 6);      // 6:00 UTC = 2:00 EDT
+}
+
+TEST(PosixTzParser, LastSundayOfMarch2026) {
+  // Europe: M3.5.0 = last Sunday of March = March 29, 2026
+  DSTRule rule{};
+  rule.type = DSTRuleType::MONTH_WEEK_DAY;
+  rule.month = 3;
+  rule.week = 5;
+  rule.day_of_week = 0;
+  rule.time_seconds = 2 * 3600;
+  time_t transition = internal::calculate_dst_transition(2026, rule, 0);
+  struct tm tm;
+  internal::epoch_to_tm_utc(transition, &tm);
+  EXPECT_EQ(tm.tm_mday, 29);
+  EXPECT_EQ(tm.tm_wday, 0);  // Sunday
+}
+
+TEST(PosixTzParser, LastSundayOfOctober2026) {
+  // Europe: M10.5.0 = last Sunday of October = October 25, 2026
+  DSTRule rule{};
+  rule.type = DSTRuleType::MONTH_WEEK_DAY;
+  rule.month = 10;
+  rule.week = 5;
+  rule.day_of_week = 0;
+  rule.time_seconds = 3 * 3600;
+  time_t transition = internal::calculate_dst_transition(2026, rule, 0);
+  struct tm tm;
+  internal::epoch_to_tm_utc(transition, &tm);
+  EXPECT_EQ(tm.tm_mday, 25);
+  EXPECT_EQ(tm.tm_wday, 0);  // Sunday
+}
+
+TEST(PosixTzParser, FirstSundayOfApril2026) {
+  // April 5, 2026 is 1st Sunday
+  DSTRule rule{};
+  rule.type = DSTRuleType::MONTH_WEEK_DAY;
+  rule.month = 4;
+  rule.week = 1;
+  rule.day_of_week = 0;
+  rule.time_seconds = 0;
+  time_t transition = internal::calculate_dst_transition(2026, rule, 0);
+  struct tm tm;
+  internal::epoch_to_tm_utc(transition, &tm);
+  EXPECT_EQ(tm.tm_mday, 5);
+  EXPECT_EQ(tm.tm_wday, 0);
+}
+
+// ============================================================================
+// DST detection tests
+// ============================================================================
+
+TEST(PosixTzParser, IsInDstUSEasternSummer) {
+  ParsedTimezone tz;
+  parse_posix_tz("EST5EDT,M3.2.0/2,M11.1.0/2", tz);
+
+  // July 4, 2026 12:00 UTC - definitely in DST
+  time_t summer = make_utc(2026, 7, 4, 12);
+  EXPECT_TRUE(is_in_dst(summer, tz));
+}
+
+TEST(PosixTzParser, IsInDstUSEasternWinter) {
+  ParsedTimezone tz;
+  parse_posix_tz("EST5EDT,M3.2.0/2,M11.1.0/2", tz);
+
+  // January 15, 2026 12:00 UTC - definitely not in DST
+  time_t winter = make_utc(2026, 1, 15, 12);
+  EXPECT_FALSE(is_in_dst(winter, tz));
+}
+
+TEST(PosixTzParser, IsInDstNoDstTimezone) {
+  ParsedTimezone tz;
+  parse_posix_tz("IST-5:30", tz);
+
+  // July 15, 2026 12:00 UTC
+  time_t epoch = make_utc(2026, 7, 15, 12);
+  EXPECT_FALSE(is_in_dst(epoch, tz));
+}
+
+TEST(PosixTzParser, SouthernHemisphereDstSummer) {
+  ParsedTimezone tz;
+  parse_posix_tz("NZST-12NZDT,M9.5.0,M4.1.0/3", tz);
+
+  // December 15, 2025 12:00 UTC - summer in NZ, should be in DST
+  time_t nz_summer = make_utc(2025, 12, 15, 12);
+  EXPECT_TRUE(is_in_dst(nz_summer, tz));
+}
+
+TEST(PosixTzParser, SouthernHemisphereDstWinter) {
+  ParsedTimezone tz;
+  parse_posix_tz("NZST-12NZDT,M9.5.0,M4.1.0/3", tz);
+
+  // July 15, 2026 12:00 UTC - winter in NZ, should NOT be in DST
+  time_t nz_winter = make_utc(2026, 7, 15, 12);
+  EXPECT_FALSE(is_in_dst(nz_winter, tz));
+}
+
+// ============================================================================
+// epoch_to_local_tm tests
+// ============================================================================
+
+TEST(PosixTzParser, EpochToLocalBasic) {
+  ParsedTimezone tz;
+  parse_posix_tz("UTC0", tz);
+
+  time_t epoch = 0;  // Jan 1, 1970 00:00:00 UTC
+  struct tm local;
+  ASSERT_TRUE(epoch_to_local_tm(epoch, tz, &local));
+  EXPECT_EQ(local.tm_year, 70);
+  EXPECT_EQ(local.tm_mon, 0);
+  EXPECT_EQ(local.tm_mday, 1);
+  EXPECT_EQ(local.tm_hour, 0);
+}
+
+TEST(PosixTzParser, EpochToLocalNegativeEpoch) {
+  ParsedTimezone tz;
+  parse_posix_tz("UTC0", tz);
+
+  // Dec 31, 1969 23:59:59 UTC (1 second before epoch)
+  time_t epoch = -1;
+  struct tm local;
+  ASSERT_TRUE(epoch_to_local_tm(epoch, tz, &local));
+  EXPECT_EQ(local.tm_year, 69);  // 1969
+  EXPECT_EQ(local.tm_mon, 11);   // December
+  EXPECT_EQ(local.tm_mday, 31);
+  EXPECT_EQ(local.tm_hour, 23);
+  EXPECT_EQ(local.tm_min, 59);
+  EXPECT_EQ(local.tm_sec, 59);
+}
+
+TEST(PosixTzParser, EpochToLocalNullTmFails) {
+  ParsedTimezone tz;
+  parse_posix_tz("UTC0", tz);
+  EXPECT_FALSE(epoch_to_local_tm(0, tz, nullptr));
+}
+
+TEST(PosixTzParser, EpochToLocalWithOffset) {
+  ParsedTimezone tz;
+  parse_posix_tz("EST5", tz);  // UTC-5
+
+  // Jan 1, 2026 05:00:00 UTC should be Jan 1, 2026 00:00:00 EST
+  time_t utc_epoch = make_utc(2026, 1, 1, 5);
+
+  struct tm local;
+  ASSERT_TRUE(epoch_to_local_tm(utc_epoch, tz, &local));
+  EXPECT_EQ(local.tm_hour, 0);  // Midnight EST
+  EXPECT_EQ(local.tm_mday, 1);
+  EXPECT_EQ(local.tm_isdst, 0);
+}
+
+TEST(PosixTzParser, EpochToLocalDstTransition) {
+  ParsedTimezone tz;
+  parse_posix_tz("EST5EDT,M3.2.0/2,M11.1.0/2", tz);
+
+  // July 4, 2026 16:00 UTC = 12:00 EDT (noon)
+  time_t utc_epoch = make_utc(2026, 7, 4, 16);
+
+  struct tm local;
+  ASSERT_TRUE(epoch_to_local_tm(utc_epoch, tz, &local));
+  EXPECT_EQ(local.tm_hour, 12);  // Noon EDT
+  EXPECT_EQ(local.tm_isdst, 1);
+}
+
+// ============================================================================
+// Verification against libc
+// ============================================================================
+
+class LibcVerificationTest : public ::testing::TestWithParam<std::tuple<const char *, time_t>> {
+ protected:
+  // NOLINTNEXTLINE(readability-identifier-naming) - Google Test requires this name
+  void SetUp() override {
+    // Save current TZ
+    const char *current_tz = getenv("TZ");
+    saved_tz_ = current_tz ? current_tz : "";
+    had_tz_ = current_tz != nullptr;
+  }
+
+  // NOLINTNEXTLINE(readability-identifier-naming) - Google Test requires this name
+  void TearDown() override {
+    // Restore TZ
+    if (had_tz_) {
+      setenv("TZ", saved_tz_.c_str(), 1);
+    } else {
+      unsetenv("TZ");
+    }
+    tzset();
+  }
+
+ private:
+  std::string saved_tz_;
+  bool had_tz_{false};
+};
+
+TEST_P(LibcVerificationTest, MatchesLibc) {
+  auto [tz_str, epoch] = GetParam();
+
+  ParsedTimezone tz;
+  ASSERT_TRUE(parse_posix_tz(tz_str, tz));
+
+  // Our implementation
+  struct tm our_tm {};
+  ASSERT_TRUE(epoch_to_local_tm(epoch, tz, &our_tm));
+
+  // libc implementation
+  setenv("TZ", tz_str, 1);
+  tzset();
+  struct tm *libc_tm = localtime(&epoch);
+  ASSERT_NE(libc_tm, nullptr);
+
+  EXPECT_EQ(our_tm.tm_year, libc_tm->tm_year);
+  EXPECT_EQ(our_tm.tm_mon, libc_tm->tm_mon);
+  EXPECT_EQ(our_tm.tm_mday, libc_tm->tm_mday);
+  EXPECT_EQ(our_tm.tm_hour, libc_tm->tm_hour);
+  EXPECT_EQ(our_tm.tm_min, libc_tm->tm_min);
+  EXPECT_EQ(our_tm.tm_sec, libc_tm->tm_sec);
+  EXPECT_EQ(our_tm.tm_isdst, libc_tm->tm_isdst);
+}
+
+INSTANTIATE_TEST_SUITE_P(USEastern, LibcVerificationTest,
+                         ::testing::Values(std::make_tuple("EST5EDT,M3.2.0/2,M11.1.0/2", 1704067200),
+                                           std::make_tuple("EST5EDT,M3.2.0/2,M11.1.0/2", 1720000000),
+                                           std::make_tuple("EST5EDT,M3.2.0/2,M11.1.0/2", 1735689600)));
+
+INSTANTIATE_TEST_SUITE_P(AngleBracket, LibcVerificationTest,
+                         ::testing::Values(std::make_tuple("<+07>-7", 1704067200),
+                                           std::make_tuple("<+07>-7", 1720000000)));
+
+INSTANTIATE_TEST_SUITE_P(India, LibcVerificationTest,
+                         ::testing::Values(std::make_tuple("IST-5:30", 1704067200),
+                                           std::make_tuple("IST-5:30", 1720000000)));
+
+INSTANTIATE_TEST_SUITE_P(NewZealand, LibcVerificationTest,
+                         ::testing::Values(std::make_tuple("NZST-12NZDT,M9.5.0,M4.1.0/3", 1704067200),
+                                           std::make_tuple("NZST-12NZDT,M9.5.0,M4.1.0/3", 1720000000)));
+
+INSTANTIATE_TEST_SUITE_P(USCentral, LibcVerificationTest,
+                         ::testing::Values(std::make_tuple("CST6CDT,M3.2.0/2,M11.1.0/2", 1704067200),
+                                           std::make_tuple("CST6CDT,M3.2.0/2,M11.1.0/2", 1720000000),
+                                           std::make_tuple("CST6CDT,M3.2.0/2,M11.1.0/2", 1735689600)));
+
+INSTANTIATE_TEST_SUITE_P(EuropeBerlin, LibcVerificationTest,
+                         ::testing::Values(std::make_tuple("CET-1CEST,M3.5.0,M10.5.0/3", 1704067200),
+                                           std::make_tuple("CET-1CEST,M3.5.0,M10.5.0/3", 1720000000),
+                                           std::make_tuple("CET-1CEST,M3.5.0,M10.5.0/3", 1735689600)));
+
+INSTANTIATE_TEST_SUITE_P(AustraliaSydney, LibcVerificationTest,
+                         ::testing::Values(std::make_tuple("AEST-10AEDT,M10.1.0,M4.1.0/3", 1704067200),
+                                           std::make_tuple("AEST-10AEDT,M10.1.0,M4.1.0/3", 1720000000),
+                                           std::make_tuple("AEST-10AEDT,M10.1.0,M4.1.0/3", 1735689600)));
+
+// ============================================================================
+// DST boundary edge cases
+// ============================================================================
+
+TEST(PosixTzParser, DstBoundaryJustBeforeSpringForward) {
+  // Test 1 second before DST starts
+  ParsedTimezone tz;
+  parse_posix_tz("EST5EDT,M3.2.0/2,M11.1.0/2", tz);
+
+  // March 8, 2026 06:59:59 UTC = 01:59:59 EST (1 second before spring forward)
+  time_t before_epoch = make_utc(2026, 3, 8, 6, 59, 59);
+  EXPECT_FALSE(is_in_dst(before_epoch, tz));
+
+  // March 8, 2026 07:00:00 UTC = 02:00:00 EST -> 03:00:00 EDT (DST started)
+  time_t after_epoch = make_utc(2026, 3, 8, 7);
+  EXPECT_TRUE(is_in_dst(after_epoch, tz));
+}
+
+TEST(PosixTzParser, DstBoundaryJustBeforeFallBack) {
+  // Test 1 second before DST ends
+  ParsedTimezone tz;
+  parse_posix_tz("EST5EDT,M3.2.0/2,M11.1.0/2", tz);
+
+  // November 1, 2026 05:59:59 UTC = 01:59:59 EDT (1 second before fall back)
+  time_t before_epoch = make_utc(2026, 11, 1, 5, 59, 59);
+  EXPECT_TRUE(is_in_dst(before_epoch, tz));
+
+  // November 1, 2026 06:00:00 UTC = 02:00:00 EDT -> 01:00:00 EST (DST ended)
+  time_t after_epoch = make_utc(2026, 11, 1, 6);
+  EXPECT_FALSE(is_in_dst(after_epoch, tz));
+}
+
+}  // namespace esphome::time::testing
+
+// ============================================================================
+// ESPTime::strptime tests (replaces sscanf-based parsing)
+// ============================================================================
+
+namespace esphome::testing {
+
+TEST(ESPTimeStrptime, FullDateTime) {
+  ESPTime t{};
+  ASSERT_TRUE(ESPTime::strptime("2026-03-15 14:30:45", 19, t));
+  EXPECT_EQ(t.year, 2026);
+  EXPECT_EQ(t.month, 3);
+  EXPECT_EQ(t.day_of_month, 15);
+  EXPECT_EQ(t.hour, 14);
+  EXPECT_EQ(t.minute, 30);
+  EXPECT_EQ(t.second, 45);
+}
+
+TEST(ESPTimeStrptime, DateTimeNoSeconds) {
+  ESPTime t{};
+  ASSERT_TRUE(ESPTime::strptime("2026-03-15 14:30", 16, t));
+  EXPECT_EQ(t.year, 2026);
+  EXPECT_EQ(t.month, 3);
+  EXPECT_EQ(t.day_of_month, 15);
+  EXPECT_EQ(t.hour, 14);
+  EXPECT_EQ(t.minute, 30);
+  EXPECT_EQ(t.second, 0);
+}
+
+TEST(ESPTimeStrptime, DateOnly) {
+  ESPTime t{};
+  ASSERT_TRUE(ESPTime::strptime("2026-03-15", 10, t));
+  EXPECT_EQ(t.year, 2026);
+  EXPECT_EQ(t.month, 3);
+  EXPECT_EQ(t.day_of_month, 15);
+}
+
+TEST(ESPTimeStrptime, TimeWithSeconds) {
+  ESPTime t{};
+  ASSERT_TRUE(ESPTime::strptime("14:30:45", 8, t));
+  EXPECT_EQ(t.hour, 14);
+  EXPECT_EQ(t.minute, 30);
+  EXPECT_EQ(t.second, 45);
+}
+
+TEST(ESPTimeStrptime, TimeNoSeconds) {
+  ESPTime t{};
+  ASSERT_TRUE(ESPTime::strptime("14:30", 5, t));
+  EXPECT_EQ(t.hour, 14);
+  EXPECT_EQ(t.minute, 30);
+  EXPECT_EQ(t.second, 0);
+}
+
+TEST(ESPTimeStrptime, Midnight) {
+  ESPTime t{};
+  ASSERT_TRUE(ESPTime::strptime("00:00:00", 8, t));
+  EXPECT_EQ(t.hour, 0);
+  EXPECT_EQ(t.minute, 0);
+  EXPECT_EQ(t.second, 0);
+}
+
+TEST(ESPTimeStrptime, EndOfDay) {
+  ESPTime t{};
+  ASSERT_TRUE(ESPTime::strptime("23:59:59", 8, t));
+  EXPECT_EQ(t.hour, 23);
+  EXPECT_EQ(t.minute, 59);
+  EXPECT_EQ(t.second, 59);
+}
+
+TEST(ESPTimeStrptime, LeapYearDate) {
+  ESPTime t{};
+  ASSERT_TRUE(ESPTime::strptime("2024-02-29", 10, t));
+  EXPECT_EQ(t.year, 2024);
+  EXPECT_EQ(t.month, 2);
+  EXPECT_EQ(t.day_of_month, 29);
+}
+
+TEST(ESPTimeStrptime, NewYearsEve) {
+  ESPTime t{};
+  ASSERT_TRUE(ESPTime::strptime("2026-12-31 23:59:59", 19, t));
+  EXPECT_EQ(t.year, 2026);
+  EXPECT_EQ(t.month, 12);
+  EXPECT_EQ(t.day_of_month, 31);
+  EXPECT_EQ(t.hour, 23);
+  EXPECT_EQ(t.minute, 59);
+  EXPECT_EQ(t.second, 59);
+}
+
+TEST(ESPTimeStrptime, EmptyStringFails) {
+  ESPTime t{};
+  EXPECT_FALSE(ESPTime::strptime("", 0, t));
+}
+
+TEST(ESPTimeStrptime, NullInputFails) {
+  ESPTime t{};
+  EXPECT_FALSE(ESPTime::strptime(nullptr, 0, t));
+}
+
+TEST(ESPTimeStrptime, InvalidFormatFails) {
+  ESPTime t{};
+  EXPECT_FALSE(ESPTime::strptime("not-a-date", 10, t));
+}
+
+TEST(ESPTimeStrptime, PartialDateFails) {
+  ESPTime t{};
+  EXPECT_FALSE(ESPTime::strptime("2026-03", 7, t));
+}
+
+TEST(ESPTimeStrptime, PartialTimeFails) {
+  ESPTime t{};
+  EXPECT_FALSE(ESPTime::strptime("14:", 3, t));
+}
+
+TEST(ESPTimeStrptime, ExtraCharactersFails) {
+  ESPTime t{};
+  // Full datetime with extra characters should fail
+  EXPECT_FALSE(ESPTime::strptime("2026-03-15 14:30:45x", 20, t));
+}
+
+TEST(ESPTimeStrptime, WrongSeparatorFails) {
+  ESPTime t{};
+  EXPECT_FALSE(ESPTime::strptime("2026/03/15", 10, t));
+}
+
+TEST(ESPTimeStrptime, LeadingZeroTime) {
+  ESPTime t{};
+  ASSERT_TRUE(ESPTime::strptime("01:05:09", 8, t));
+  EXPECT_EQ(t.hour, 1);
+  EXPECT_EQ(t.minute, 5);
+  EXPECT_EQ(t.second, 9);
+}
+
+// ============================================================================
+// recalc_timestamp_local() tests - verify behavior matches libc mktime()
+// ============================================================================
+
+// Helper to call libc mktime with same fields
+static time_t libc_mktime(int year, int month, int day, int hour, int min, int sec) {
+  struct tm tm {};
+  tm.tm_year = year - 1900;
+  tm.tm_mon = month - 1;
+  tm.tm_mday = day;
+  tm.tm_hour = hour;
+  tm.tm_min = min;
+  tm.tm_sec = sec;
+  tm.tm_isdst = -1;  // Let libc determine DST
+  return mktime(&tm);
+}
+
+// Helper to create ESPTime and call recalc_timestamp_local
+static time_t esptime_recalc_local(int year, int month, int day, int hour, int min, int sec) {
+  ESPTime t{};
+  t.year = year;
+  t.month = month;
+  t.day_of_month = day;
+  t.hour = hour;
+  t.minute = min;
+  t.second = sec;
+  t.day_of_week = 1;  // Placeholder for fields_in_range()
+  t.day_of_year = 1;
+  t.recalc_timestamp_local();
+  return t.timestamp;
+}
+
+TEST(RecalcTimestampLocal, NormalTimeMatchesLibc) {
+  // Set timezone to US Central (CST6CDT)
+  const char *tz_str = "CST6CDT,M3.2.0,M11.1.0";
+  setenv("TZ", tz_str, 1);
+  tzset();
+  time::ParsedTimezone tz{};
+  ASSERT_TRUE(parse_posix_tz(tz_str, tz));
+  set_global_tz(tz);
+
+  // Test a normal time in winter (no DST)
+  // January 15, 2026 at 10:30:00 CST
+  time_t libc_result = libc_mktime(2026, 1, 15, 10, 30, 0);
+  time_t esp_result = esptime_recalc_local(2026, 1, 15, 10, 30, 0);
+  EXPECT_EQ(esp_result, libc_result);
+
+  // Test a normal time in summer (DST active)
+  // July 15, 2026 at 10:30:00 CDT
+  libc_result = libc_mktime(2026, 7, 15, 10, 30, 0);
+  esp_result = esptime_recalc_local(2026, 7, 15, 10, 30, 0);
+  EXPECT_EQ(esp_result, libc_result);
+}
+
+TEST(RecalcTimestampLocal, SpringForwardSkippedHour) {
+  // Set timezone to US Central (CST6CDT)
+  // DST starts March 8, 2026 at 2:00 AM -> clocks jump to 3:00 AM
+  const char *tz_str = "CST6CDT,M3.2.0,M11.1.0";
+  setenv("TZ", tz_str, 1);
+  tzset();
+  time::ParsedTimezone tz{};
+  ASSERT_TRUE(parse_posix_tz(tz_str, tz));
+  set_global_tz(tz);
+
+  // Test time before the transition (1:30 AM CST exists)
+  time_t libc_result = libc_mktime(2026, 3, 8, 1, 30, 0);
+  time_t esp_result = esptime_recalc_local(2026, 3, 8, 1, 30, 0);
+  EXPECT_EQ(esp_result, libc_result);
+
+  // Test time after the transition (3:30 AM CDT exists)
+  libc_result = libc_mktime(2026, 3, 8, 3, 30, 0);
+  esp_result = esptime_recalc_local(2026, 3, 8, 3, 30, 0);
+  EXPECT_EQ(esp_result, libc_result);
+
+  // Test the skipped hour (2:30 AM doesn't exist - gets normalized)
+  // Both implementations should produce the same result
+  libc_result = libc_mktime(2026, 3, 8, 2, 30, 0);
+  esp_result = esptime_recalc_local(2026, 3, 8, 2, 30, 0);
+  EXPECT_EQ(esp_result, libc_result);
+}
+
+TEST(RecalcTimestampLocal, FallBackRepeatedHour) {
+  // Set timezone to US Central (CST6CDT)
+  // DST ends November 1, 2026 at 2:00 AM -> clocks fall back to 1:00 AM
+  const char *tz_str = "CST6CDT,M3.2.0,M11.1.0";
+  setenv("TZ", tz_str, 1);
+  tzset();
+  time::ParsedTimezone tz{};
+  ASSERT_TRUE(parse_posix_tz(tz_str, tz));
+  set_global_tz(tz);
+
+  // Test time before the transition (midnight CDT)
+  time_t libc_result = libc_mktime(2026, 11, 1, 0, 30, 0);
+  time_t esp_result = esptime_recalc_local(2026, 11, 1, 0, 30, 0);
+  EXPECT_EQ(esp_result, libc_result);
+
+  // Test time well after the transition (3:00 AM CST)
+  libc_result = libc_mktime(2026, 11, 1, 3, 0, 0);
+  esp_result = esptime_recalc_local(2026, 11, 1, 3, 0, 0);
+  EXPECT_EQ(esp_result, libc_result);
+
+  // Test the repeated hour (1:30 AM occurs twice)
+  // libc behavior varies by platform for this edge case, so we verify our
+  // consistent behavior: prefer standard time (later UTC timestamp)
+  esp_result = esptime_recalc_local(2026, 11, 1, 1, 30, 0);
+  time_t std_interpretation = esptime_recalc_local(2026, 11, 1, 2, 30, 0) - 3600;  // 2:30 CST - 1 hour
+  EXPECT_EQ(esp_result, std_interpretation);
+}
+
+TEST(RecalcTimestampLocal, SouthernHemisphereDST) {
+  // Set timezone to Australia/Sydney (AEST-10AEDT,M10.1.0,M4.1.0)
+  // DST starts first Sunday of October, ends first Sunday of April
+  const char *tz_str = "AEST-10AEDT,M10.1.0,M4.1.0";
+  setenv("TZ", tz_str, 1);
+  tzset();
+  time::ParsedTimezone tz{};
+  ASSERT_TRUE(parse_posix_tz(tz_str, tz));
+  set_global_tz(tz);
+
+  // Test winter time (July - no DST in southern hemisphere)
+  time_t libc_result = libc_mktime(2026, 7, 15, 10, 30, 0);
+  time_t esp_result = esptime_recalc_local(2026, 7, 15, 10, 30, 0);
+  EXPECT_EQ(esp_result, libc_result);
+
+  // Test summer time (January - DST active in southern hemisphere)
+  libc_result = libc_mktime(2026, 1, 15, 10, 30, 0);
+  esp_result = esptime_recalc_local(2026, 1, 15, 10, 30, 0);
+  EXPECT_EQ(esp_result, libc_result);
+}
+
+TEST(RecalcTimestampLocal, ExactTransitionBoundary) {
+  // Test exact boundary of spring forward transition
+  // Mar 8, 2026 at 2:00 AM CST -> 3:00 AM CDT (clocks skip forward)
+  const char *tz_str = "CST6CDT,M3.2.0,M11.1.0";
+  setenv("TZ", tz_str, 1);
+  tzset();
+  time::ParsedTimezone tz{};
+  ASSERT_TRUE(parse_posix_tz(tz_str, tz));
+  set_global_tz(tz);
+
+  // 1:59:59 AM CST - last second before transition (still standard time)
+  time_t libc_result = libc_mktime(2026, 3, 8, 1, 59, 59);
+  time_t esp_result = esptime_recalc_local(2026, 3, 8, 1, 59, 59);
+  EXPECT_EQ(esp_result, libc_result);
+
+  // 3:00:00 AM CDT - first second after transition (now DST)
+  libc_result = libc_mktime(2026, 3, 8, 3, 0, 0);
+  esp_result = esptime_recalc_local(2026, 3, 8, 3, 0, 0);
+  EXPECT_EQ(esp_result, libc_result);
+
+  // Verify the gap: 3:00 AM CDT should be exactly 1 second after 1:59:59 AM CST
+  time_t before_transition = esptime_recalc_local(2026, 3, 8, 1, 59, 59);
+  time_t after_transition = esptime_recalc_local(2026, 3, 8, 3, 0, 0);
+  EXPECT_EQ(after_transition - before_transition, 1);
+}
+
+TEST(RecalcTimestampLocal, NonDefaultTransitionTime) {
+  // Test DST transition at 3:00 AM instead of default 2:00 AM
+  // Using custom transition time: CST6CDT,M3.2.0/3,M11.1.0/3
+  const char *tz_str = "CST6CDT,M3.2.0/3,M11.1.0/3";
+  setenv("TZ", tz_str, 1);
+  tzset();
+  time::ParsedTimezone tz{};
+  ASSERT_TRUE(parse_posix_tz(tz_str, tz));
+  set_global_tz(tz);
+
+  // 2:30 AM should still be standard time (transition at 3:00 AM)
+  time_t libc_result = libc_mktime(2026, 3, 8, 2, 30, 0);
+  time_t esp_result = esptime_recalc_local(2026, 3, 8, 2, 30, 0);
+  EXPECT_EQ(esp_result, libc_result);
+
+  // 4:00 AM should be DST (after 3:00 AM transition)
+  libc_result = libc_mktime(2026, 3, 8, 4, 0, 0);
+  esp_result = esptime_recalc_local(2026, 3, 8, 4, 0, 0);
+  EXPECT_EQ(esp_result, libc_result);
+}
+
+TEST(RecalcTimestampLocal, YearBoundaryDST) {
+  // Test southern hemisphere DST across year boundary
+  // Australia/Sydney: DST active from October to April (spans Jan 1)
+  const char *tz_str = "AEST-10AEDT,M10.1.0,M4.1.0";
+  setenv("TZ", tz_str, 1);
+  tzset();
+  time::ParsedTimezone tz{};
+  ASSERT_TRUE(parse_posix_tz(tz_str, tz));
+  set_global_tz(tz);
+
+  // Dec 31, 2025 at 23:30 - DST should be active
+  time_t libc_result = libc_mktime(2025, 12, 31, 23, 30, 0);
+  time_t esp_result = esptime_recalc_local(2025, 12, 31, 23, 30, 0);
+  EXPECT_EQ(esp_result, libc_result);
+
+  // Jan 1, 2026 at 00:30 - DST should still be active
+  libc_result = libc_mktime(2026, 1, 1, 0, 30, 0);
+  esp_result = esptime_recalc_local(2026, 1, 1, 0, 30, 0);
+  EXPECT_EQ(esp_result, libc_result);
+
+  // Verify both are in DST (11 hour offset from UTC, not 10)
+  // The timestamps should be 1 hour apart
+  time_t dec31 = esptime_recalc_local(2025, 12, 31, 23, 30, 0);
+  time_t jan1 = esptime_recalc_local(2026, 1, 1, 0, 30, 0);
+  EXPECT_EQ(jan1 - dec31, 3600);  // 1 hour difference
+}
+
+// ============================================================================
+// ESPTime::timezone_offset() tests
+// ============================================================================
+
+TEST(TimezoneOffset, NoTimezone) {
+  // When no timezone is set, offset should be 0
+  time::ParsedTimezone tz{};
+  set_global_tz(tz);
+
+  int32_t offset = ESPTime::timezone_offset();
+  EXPECT_EQ(offset, 0);
+}
+
+TEST(TimezoneOffset, FixedOffsetPositive) {
+  // India: UTC+5:30 (no DST)
+  const char *tz_str = "IST-5:30";
+  time::ParsedTimezone tz{};
+  ASSERT_TRUE(parse_posix_tz(tz_str, tz));
+  set_global_tz(tz);
+
+  int32_t offset = ESPTime::timezone_offset();
+  // Offset should be +5:30 = 19800 seconds (to add to UTC to get local)
+  EXPECT_EQ(offset, 5 * 3600 + 30 * 60);
+}
+
+TEST(TimezoneOffset, FixedOffsetNegative) {
+  // US Eastern Standard Time: UTC-5 (testing without DST rules)
+  const char *tz_str = "EST5";
+  time::ParsedTimezone tz{};
+  ASSERT_TRUE(parse_posix_tz(tz_str, tz));
+  set_global_tz(tz);
+
+  int32_t offset = ESPTime::timezone_offset();
+  // Offset should be -5 hours = -18000 seconds
+  EXPECT_EQ(offset, -5 * 3600);
+}
+
+TEST(TimezoneOffset, WithDstReturnsCorrectOffsetBasedOnCurrentTime) {
+  // US Eastern with DST
+  const char *tz_str = "EST5EDT,M3.2.0,M11.1.0";
+  time::ParsedTimezone tz{};
+  ASSERT_TRUE(parse_posix_tz(tz_str, tz));
+  set_global_tz(tz);
+
+  // Get current time and check offset matches expected based on DST status
+  time_t now = ::time(nullptr);
+  int32_t offset = ESPTime::timezone_offset();
+
+  // Verify offset matches what is_in_dst says
+  if (time::is_in_dst(now, tz)) {
+    // During DST, offset should be -4 hours (EDT)
+    EXPECT_EQ(offset, -4 * 3600);
+  } else {
+    // During standard time, offset should be -5 hours (EST)
+    EXPECT_EQ(offset, -5 * 3600);
+  }
+}
+
+}  // namespace esphome::testing
diff --git a/tests/integration/fixtures/sensor_filters_delta.yaml b/tests/integration/fixtures/sensor_filters_delta.yaml
index 19bd2d5ca4..2494a430da 100644
--- a/tests/integration/fixtures/sensor_filters_delta.yaml
+++ b/tests/integration/fixtures/sensor_filters_delta.yaml
@@ -28,6 +28,11 @@ sensor:
     id: source_sensor_4
     accuracy_decimals: 1
 
+  - platform: template
+    name: "Source Sensor 5"
+    id: source_sensor_5
+    accuracy_decimals: 1
+
   - platform: copy
     source_id: source_sensor_1
     name: "Filter Min"
@@ -69,6 +74,13 @@ sensor:
     filters:
       - delta: 0
 
+  - platform: copy
+    source_id: source_sensor_5
+    name: "Filter Percentage"
+    id: filter_percentage
+    filters:
+      - delta: 50%
+
 script:
   - id: test_filter_min
     then:
@@ -154,6 +166,28 @@ script:
           id: source_sensor_4
           state: 2.0
 
+  - id: test_filter_percentage
+    then:
+      - sensor.template.publish:
+          id: source_sensor_5
+          state: 100.0
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_5
+          state: 120.0  # Filtered out (delta=20, need >50)
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_5
+          state: 160.0  # Passes (delta=60 > 50% of 100=50)
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_5
+          state: 200.0  # Filtered out (delta=40, need >50% of 160=80)
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_5
+          state: 250.0  # Passes (delta=90 > 80)
+
 button:
   - platform: template
     name: "Test Filter Min"
@@ -178,3 +212,9 @@ button:
     id: btn_filter_zero_delta
     on_press:
       - script.execute: test_filter_zero_delta
+
+  - platform: template
+    name: "Test Filter Percentage"
+    id: btn_filter_percentage
+    on_press:
+      - script.execute: test_filter_percentage
diff --git a/tests/integration/test_sensor_filters_delta.py b/tests/integration/test_sensor_filters_delta.py
index c7a26bf9d1..9d0114e0c4 100644
--- a/tests/integration/test_sensor_filters_delta.py
+++ b/tests/integration/test_sensor_filters_delta.py
@@ -24,12 +24,14 @@ async def test_sensor_filters_delta(
         "filter_max": [],
         "filter_baseline_max": [],
         "filter_zero_delta": [],
+        "filter_percentage": [],
     }
 
     filter_min_done = loop.create_future()
     filter_max_done = loop.create_future()
     filter_baseline_max_done = loop.create_future()
     filter_zero_delta_done = loop.create_future()
+    filter_percentage_done = loop.create_future()
 
     def on_state(state: EntityState) -> None:
         if not isinstance(state, SensorState) or state.missing_state:
@@ -66,6 +68,12 @@ async def test_sensor_filters_delta(
             and not filter_zero_delta_done.done()
         ):
             filter_zero_delta_done.set_result(True)
+        elif (
+            sensor_name == "filter_percentage"
+            and len(sensor_values[sensor_name]) == 3
+            and not filter_percentage_done.done()
+        ):
+            filter_percentage_done.set_result(True)
 
     async with (
         run_compiled(yaml_config),
@@ -80,6 +88,7 @@ async def test_sensor_filters_delta(
                 "filter_max": "Filter Max",
                 "filter_baseline_max": "Filter Baseline Max",
                 "filter_zero_delta": "Filter Zero Delta",
+                "filter_percentage": "Filter Percentage",
             },
         )
 
@@ -98,13 +107,14 @@ async def test_sensor_filters_delta(
             "Test Filter Max": "filter_max",
             "Test Filter Baseline Max": "filter_baseline_max",
             "Test Filter Zero Delta": "filter_zero_delta",
+            "Test Filter Percentage": "filter_percentage",
         }
         buttons = {}
         for entity in entities:
             if isinstance(entity, ButtonInfo) and entity.name in button_name_map:
                 buttons[button_name_map[entity.name]] = entity.key
 
-        assert len(buttons) == 4, f"Expected 3 buttons, found {len(buttons)}"
+        assert len(buttons) == 5, f"Expected 5 buttons, found {len(buttons)}"
 
         # Test 1: Min
         sensor_values["filter_min"].clear()
@@ -161,3 +171,18 @@ async def test_sensor_filters_delta(
         assert sensor_values["filter_zero_delta"] == pytest.approx(expected), (
             f"Test 4 failed: expected {expected}, got {sensor_values['filter_zero_delta']}"
         )
+
+        # Test 5: Percentage (delta: 50%)
+        sensor_values["filter_percentage"].clear()
+        client.button_command(buttons["filter_percentage"])
+        try:
+            await asyncio.wait_for(filter_percentage_done, timeout=2.0)
+        except TimeoutError:
+            pytest.fail(
+                f"Test 5 timed out. Values: {sensor_values['filter_percentage']}"
+            )
+
+        expected = [100.0, 160.0, 250.0]
+        assert sensor_values["filter_percentage"] == pytest.approx(expected), (
+            f"Test 5 failed: expected {expected}, got {sensor_values['filter_percentage']}"
+        )