diff --git a/CODEOWNERS b/CODEOWNERS
index 00a22fed7c..b7675f9406 100644
--- a/CODEOWNERS
+++ b/CODEOWNERS
@@ -104,6 +104,7 @@ esphome/components/cc1101/* @gabest11 @lygris
 esphome/components/ccs811/* @habbie
 esphome/components/cd74hc4067/* @asoehlke
 esphome/components/ch422g/* @clydebarrow @jesterret
+esphome/components/ch423/* @dwmw2
 esphome/components/chsc6x/* @kkosik20
 esphome/components/climate/* @esphome/core
 esphome/components/climate_ir/* @glmnet
diff --git a/esphome/components/ch423/__init__.py b/esphome/components/ch423/__init__.py
new file mode 100644
index 0000000000..e3990ee631
--- /dev/null
+++ b/esphome/components/ch423/__init__.py
@@ -0,0 +1,103 @@
+from esphome import pins
+import esphome.codegen as cg
+from esphome.components import i2c
+from esphome.components.i2c import I2CBus
+import esphome.config_validation as cv
+from esphome.const import (
+    CONF_I2C_ID,
+    CONF_ID,
+    CONF_INPUT,
+    CONF_INVERTED,
+    CONF_MODE,
+    CONF_NUMBER,
+    CONF_OPEN_DRAIN,
+    CONF_OUTPUT,
+)
+from esphome.core import CORE
+
+CODEOWNERS = ["@dwmw2"]
+DEPENDENCIES = ["i2c"]
+MULTI_CONF = True
+ch423_ns = cg.esphome_ns.namespace("ch423")
+
+CH423Component = ch423_ns.class_("CH423Component", cg.Component, i2c.I2CDevice)
+CH423GPIOPin = ch423_ns.class_(
+    "CH423GPIOPin", cg.GPIOPin, cg.Parented.template(CH423Component)
+)
+
+CONF_CH423 = "ch423"
+
+# Note that no address is configurable - each register in the CH423 has a dedicated i2c address
+CONFIG_SCHEMA = cv.Schema(
+    {
+        cv.GenerateID(CONF_ID): cv.declare_id(CH423Component),
+        cv.GenerateID(CONF_I2C_ID): cv.use_id(I2CBus),
+    }
+).extend(cv.COMPONENT_SCHEMA)
+
+
+async def to_code(config):
+    var = cg.new_Pvariable(config[CONF_ID])
+    await cg.register_component(var, config)
+    # Can't use register_i2c_device because there is no CONF_ADDRESS
+    parent = await cg.get_variable(config[CONF_I2C_ID])
+    cg.add(var.set_i2c_bus(parent))
+
+
+# This is used as a final validation step so that modes have been fully transformed.
+def pin_mode_check(pin_config, _):
+    if pin_config[CONF_MODE][CONF_INPUT] and pin_config[CONF_NUMBER] >= 8:
+        raise cv.Invalid("CH423 only supports input on pins 0-7")
+    if pin_config[CONF_MODE][CONF_OPEN_DRAIN] and pin_config[CONF_NUMBER] < 8:
+        raise cv.Invalid("CH423 only supports open drain output on pins 8-23")
+
+    ch423_id = pin_config[CONF_CH423]
+    pin_num = pin_config[CONF_NUMBER]
+    is_output = pin_config[CONF_MODE][CONF_OUTPUT]
+    is_open_drain = pin_config[CONF_MODE][CONF_OPEN_DRAIN]
+
+    # Track pin modes per CH423 instance in CORE.data
+    ch423_modes = CORE.data.setdefault(CONF_CH423, {})
+    if ch423_id not in ch423_modes:
+        ch423_modes[ch423_id] = {"gpio_output": None, "gpo_open_drain": None}
+
+    if pin_num < 8:
+        # GPIO pins (0-7): all must have same direction
+        if ch423_modes[ch423_id]["gpio_output"] is None:
+            ch423_modes[ch423_id]["gpio_output"] = is_output
+        elif ch423_modes[ch423_id]["gpio_output"] != is_output:
+            raise cv.Invalid(
+                "CH423 GPIO pins (0-7) must all be configured as input or all as output"
+            )
+    # GPO pins (8-23): all must have same open-drain setting
+    elif ch423_modes[ch423_id]["gpo_open_drain"] is None:
+        ch423_modes[ch423_id]["gpo_open_drain"] = is_open_drain
+    elif ch423_modes[ch423_id]["gpo_open_drain"] != is_open_drain:
+        raise cv.Invalid(
+            "CH423 GPO pins (8-23) must all be configured as push-pull or all as open-drain"
+        )
+
+
+CH423_PIN_SCHEMA = pins.gpio_base_schema(
+    CH423GPIOPin,
+    cv.int_range(min=0, max=23),
+    modes=[CONF_INPUT, CONF_OUTPUT, CONF_OPEN_DRAIN],
+).extend(
+    {
+        cv.Required(CONF_CH423): cv.use_id(CH423Component),
+    }
+)
+
+
+@pins.PIN_SCHEMA_REGISTRY.register(CONF_CH423, CH423_PIN_SCHEMA, pin_mode_check)
+async def ch423_pin_to_code(config):
+    var = cg.new_Pvariable(config[CONF_ID])
+    parent = await cg.get_variable(config[CONF_CH423])
+
+    cg.add(var.set_parent(parent))
+
+    num = config[CONF_NUMBER]
+    cg.add(var.set_pin(num))
+    cg.add(var.set_inverted(config[CONF_INVERTED]))
+    cg.add(var.set_flags(pins.gpio_flags_expr(config[CONF_MODE])))
+    return var
diff --git a/esphome/components/ch423/ch423.cpp b/esphome/components/ch423/ch423.cpp
new file mode 100644
index 0000000000..4abbbe7adf
--- /dev/null
+++ b/esphome/components/ch423/ch423.cpp
@@ -0,0 +1,148 @@
+#include "ch423.h"
+#include "esphome/core/log.h"
+#include "esphome/core/progmem.h"
+
+namespace esphome::ch423 {
+
+static constexpr uint8_t CH423_REG_SYS = 0x24;    // Set system parameters (0x48 >> 1)
+static constexpr uint8_t CH423_SYS_IO_OE = 0x01;  // IO output enable
+static constexpr uint8_t CH423_SYS_OD_EN = 0x04;  // Open drain enable for OC pins
+static constexpr uint8_t CH423_REG_IO = 0x30;     // Write/read IO7-IO0 (0x60 >> 1)
+static constexpr uint8_t CH423_REG_IO_RD = 0x26;  // Read IO7-IO0 (0x4D >> 1, rounded down)
+static constexpr uint8_t CH423_REG_OCL = 0x22;    // Write OC7-OC0 (0x44 >> 1)
+static constexpr uint8_t CH423_REG_OCH = 0x23;    // Write OC15-OC8 (0x46 >> 1)
+
+static const char *const TAG = "ch423";
+
+void CH423Component::setup() {
+  // set outputs before mode
+  this->write_outputs_();
+  // Set system parameters and check for errors
+  bool success = this->write_reg_(CH423_REG_SYS, this->sys_params_);
+  // Only read inputs if pins are configured for input (IO_OE not set)
+  if (success && !(this->sys_params_ & CH423_SYS_IO_OE)) {
+    success = this->read_inputs_();
+  }
+  if (!success) {
+    ESP_LOGE(TAG, "CH423 not detected");
+    this->mark_failed();
+    return;
+  }
+
+  ESP_LOGCONFIG(TAG, "Initialization complete. Warning: %d, Error: %d", this->status_has_warning(),
+                this->status_has_error());
+}
+
+void CH423Component::loop() {
+  // Clear all the previously read flags.
+  this->pin_read_flags_ = 0x00;
+}
+
+void CH423Component::dump_config() {
+  ESP_LOGCONFIG(TAG, "CH423:");
+  if (this->is_failed()) {
+    ESP_LOGE(TAG, ESP_LOG_MSG_COMM_FAIL);
+  }
+}
+
+void CH423Component::pin_mode(uint8_t pin, gpio::Flags flags) {
+  if (pin < 8) {
+    if (flags & gpio::FLAG_OUTPUT) {
+      this->sys_params_ |= CH423_SYS_IO_OE;
+    }
+  } else if (pin >= 8 && pin < 24) {
+    if (flags & gpio::FLAG_OPEN_DRAIN) {
+      this->sys_params_ |= CH423_SYS_OD_EN;
+    }
+  }
+}
+
+bool CH423Component::digital_read(uint8_t pin) {
+  if (this->pin_read_flags_ == 0 || this->pin_read_flags_ & (1 << pin)) {
+    // Read values on first access or in case it's being read again in the same loop
+    this->read_inputs_();
+  }
+
+  this->pin_read_flags_ |= (1 << pin);
+  return (this->input_bits_ & (1 << pin)) != 0;
+}
+
+void CH423Component::digital_write(uint8_t pin, bool value) {
+  if (value) {
+    this->output_bits_ |= (1 << pin);
+  } else {
+    this->output_bits_ &= ~(1 << pin);
+  }
+  this->write_outputs_();
+}
+
+bool CH423Component::read_inputs_() {
+  if (this->is_failed()) {
+    return false;
+  }
+  // reading inputs requires IO_OE to be 0
+  if (this->sys_params_ & CH423_SYS_IO_OE) {
+    return false;
+  }
+  uint8_t result = this->read_reg_(CH423_REG_IO_RD);
+  this->input_bits_ = result;
+  this->status_clear_warning();
+  return true;
+}
+
+// Write a register. Can't use the standard write_byte() method because there is no single pre-configured i2c address.
+bool CH423Component::write_reg_(uint8_t reg, uint8_t value) {
+  auto err = this->bus_->write_readv(reg, &value, 1, nullptr, 0);
+  if (err != i2c::ERROR_OK) {
+    char buf[64];
+    ESPHOME_snprintf_P(buf, sizeof(buf), ESPHOME_PSTR("write failed for register 0x%X, error %d"), reg, err);
+    this->status_set_warning(buf);
+    return false;
+  }
+  this->status_clear_warning();
+  return true;
+}
+
+uint8_t CH423Component::read_reg_(uint8_t reg) {
+  uint8_t value;
+  auto err = this->bus_->write_readv(reg, nullptr, 0, &value, 1);
+  if (err != i2c::ERROR_OK) {
+    char buf[64];
+    ESPHOME_snprintf_P(buf, sizeof(buf), ESPHOME_PSTR("read failed for register 0x%X, error %d"), reg, err);
+    this->status_set_warning(buf);
+    return 0;
+  }
+  this->status_clear_warning();
+  return value;
+}
+
+bool CH423Component::write_outputs_() {
+  bool success = true;
+  // Write IO7-IO0
+  success &= this->write_reg_(CH423_REG_IO, static_cast<uint8_t>(this->output_bits_));
+  // Write OC7-OC0
+  success &= this->write_reg_(CH423_REG_OCL, static_cast<uint8_t>(this->output_bits_ >> 8));
+  // Write OC15-OC8
+  success &= this->write_reg_(CH423_REG_OCH, static_cast<uint8_t>(this->output_bits_ >> 16));
+  return success;
+}
+
+float CH423Component::get_setup_priority() const { return setup_priority::IO; }
+
+// Run our loop() method very early in the loop, so that we cache read values
+// before other components call our digital_read() method.
+float CH423Component::get_loop_priority() const { return 9.0f; }  // Just after WIFI
+
+void CH423GPIOPin::pin_mode(gpio::Flags flags) { this->parent_->pin_mode(this->pin_, flags); }
+bool CH423GPIOPin::digital_read() { return this->parent_->digital_read(this->pin_) ^ this->inverted_; }
+
+void CH423GPIOPin::digital_write(bool value) { this->parent_->digital_write(this->pin_, value ^ this->inverted_); }
+size_t CH423GPIOPin::dump_summary(char *buffer, size_t len) const {
+  return snprintf(buffer, len, "EXIO%u via CH423", this->pin_);
+}
+void CH423GPIOPin::set_flags(gpio::Flags flags) {
+  flags_ = flags;
+  this->parent_->pin_mode(this->pin_, flags);
+}
+
+}  // namespace esphome::ch423
diff --git a/esphome/components/ch423/ch423.h b/esphome/components/ch423/ch423.h
new file mode 100644
index 0000000000..7adc7de6a1
--- /dev/null
+++ b/esphome/components/ch423/ch423.h
@@ -0,0 +1,67 @@
+#pragma once
+
+#include "esphome/core/component.h"
+#include "esphome/core/hal.h"
+#include "esphome/components/i2c/i2c.h"
+
+namespace esphome::ch423 {
+
+class CH423Component : public Component, public i2c::I2CDevice {
+ public:
+  CH423Component() = default;
+
+  /// Check i2c availability and setup masks
+  void setup() override;
+  /// Poll for input changes periodically
+  void loop() override;
+  /// Helper function to read the value of a pin.
+  bool digital_read(uint8_t pin);
+  /// Helper function to write the value of a pin.
+  void digital_write(uint8_t pin, bool value);
+  /// Helper function to set the pin mode of a pin.
+  void pin_mode(uint8_t pin, gpio::Flags flags);
+
+  float get_setup_priority() const override;
+  float get_loop_priority() const override;
+  void dump_config() override;
+
+ protected:
+  bool write_reg_(uint8_t reg, uint8_t value);
+  uint8_t read_reg_(uint8_t reg);
+  bool read_inputs_();
+  bool write_outputs_();
+
+  /// The mask to write as output state - 1 means HIGH, 0 means LOW
+  uint32_t output_bits_{0x00};
+  /// Flags to check if read previously during this loop
+  uint8_t pin_read_flags_{0x00};
+  /// Copy of last read values
+  uint8_t input_bits_{0x00};
+  /// System parameters
+  uint8_t sys_params_{0x00};
+};
+
+/// Helper class to expose a CH423 pin as a GPIO pin.
+class CH423GPIOPin : public GPIOPin {
+ public:
+  void setup() override{};
+  void pin_mode(gpio::Flags flags) override;
+  bool digital_read() override;
+  void digital_write(bool value) override;
+  size_t dump_summary(char *buffer, size_t len) const override;
+
+  void set_parent(CH423Component *parent) { parent_ = parent; }
+  void set_pin(uint8_t pin) { pin_ = pin; }
+  void set_inverted(bool inverted) { inverted_ = inverted; }
+  void set_flags(gpio::Flags flags);
+
+  gpio::Flags get_flags() const override { return this->flags_; }
+
+ protected:
+  CH423Component *parent_{};
+  uint8_t pin_{};
+  bool inverted_{};
+  gpio::Flags flags_{};
+};
+
+}  // namespace esphome::ch423
diff --git a/esphome/components/esp32/__init__.py b/esphome/components/esp32/__init__.py
index 1d7ea5395f..a3154f9933 100644
--- a/esphome/components/esp32/__init__.py
+++ b/esphome/components/esp32/__init__.py
@@ -739,9 +739,10 @@ CONF_DISABLE_REGI2C_IN_IRAM = "disable_regi2c_in_iram"
 CONF_DISABLE_FATFS = "disable_fatfs"
 
 # VFS requirement tracking
-# Components that need VFS features can call require_vfs_select() or require_vfs_dir()
+# Components that need VFS features can call require_vfs_*() functions
 KEY_VFS_SELECT_REQUIRED = "vfs_select_required"
 KEY_VFS_DIR_REQUIRED = "vfs_dir_required"
+KEY_VFS_TERMIOS_REQUIRED = "vfs_termios_required"
 # Feature requirement tracking - components can call require_* functions to re-enable
 # These are stored in CORE.data[KEY_ESP32] dict
 KEY_USB_SERIAL_JTAG_SECONDARY_REQUIRED = "usb_serial_jtag_secondary_required"
@@ -768,6 +769,15 @@ def require_vfs_dir() -> None:
     CORE.data[KEY_VFS_DIR_REQUIRED] = True
 
 
+def require_vfs_termios() -> None:
+    """Mark that VFS termios support is required by a component.
+
+    Call this from components that use terminal I/O functions (usb_serial_jtag_vfs_*, etc.).
+    This prevents CONFIG_VFS_SUPPORT_TERMIOS from being disabled.
+    """
+    CORE.data[KEY_VFS_TERMIOS_REQUIRED] = True
+
+
 def require_full_certificate_bundle() -> None:
     """Request the full certificate bundle instead of the common-CAs-only bundle.
 
@@ -1372,11 +1382,18 @@ async def to_code(config):
         add_idf_sdkconfig_option("CONFIG_LIBC_LOCKS_PLACE_IN_IRAM", False)
 
     # Disable VFS support for termios (terminal I/O functions)
-    # ESPHome doesn't use termios functions on ESP32 (only used in host UART driver).
+    # USB Serial JTAG VFS functions require termios support.
+    # Components that need it (e.g., logger when USB_SERIAL_JTAG is supported but not selected
+    # as the logger output) call require_vfs_termios().
     # Saves approximately 1.8KB of flash when disabled (default).
-    add_idf_sdkconfig_option(
-        "CONFIG_VFS_SUPPORT_TERMIOS", not advanced[CONF_DISABLE_VFS_SUPPORT_TERMIOS]
-    )
+    if CORE.data.get(KEY_VFS_TERMIOS_REQUIRED, False):
+        # Component requires VFS termios - force enable regardless of user setting
+        add_idf_sdkconfig_option("CONFIG_VFS_SUPPORT_TERMIOS", True)
+    else:
+        # No component needs it - allow user to control (default: disabled)
+        add_idf_sdkconfig_option(
+            "CONFIG_VFS_SUPPORT_TERMIOS", not advanced[CONF_DISABLE_VFS_SUPPORT_TERMIOS]
+        )
 
     # Disable VFS support for select() with file descriptors
     # ESPHome only uses select() with sockets via lwip_select(), which still works.
diff --git a/esphome/components/logger/__init__.py b/esphome/components/logger/__init__.py
index cadd0a14ae..40ceaec7dc 100644
--- a/esphome/components/logger/__init__.py
+++ b/esphome/components/logger/__init__.py
@@ -16,6 +16,8 @@ from esphome.components.esp32 import (
     VARIANT_ESP32S3,
     add_idf_sdkconfig_option,
     get_esp32_variant,
+    require_usb_serial_jtag_secondary,
+    require_vfs_termios,
 )
 from esphome.components.libretiny import get_libretiny_component, get_libretiny_family
 from esphome.components.libretiny.const import (
@@ -397,9 +399,15 @@ async def to_code(config):
         elif config[CONF_HARDWARE_UART] == USB_SERIAL_JTAG:
             add_idf_sdkconfig_option("CONFIG_ESP_CONSOLE_USB_SERIAL_JTAG", True)
             cg.add_define("USE_LOGGER_UART_SELECTION_USB_SERIAL_JTAG")
+    # Define platform support flags for components that need auto-detection
     try:
         uart_selection(USB_SERIAL_JTAG)
         cg.add_define("USE_LOGGER_USB_SERIAL_JTAG")
+        # USB Serial JTAG code is compiled when platform supports it.
+        # Enable secondary USB serial JTAG console so the VFS functions are available.
+        if CORE.is_esp32 and config[CONF_HARDWARE_UART] != USB_SERIAL_JTAG:
+            require_usb_serial_jtag_secondary()
+            require_vfs_termios()
     except cv.Invalid:
         pass
     try:
diff --git a/esphome/components/pmsx003/pmsx003.cpp b/esphome/components/pmsx003/pmsx003.cpp
index bb167033d1..b0920de062 100644
--- a/esphome/components/pmsx003/pmsx003.cpp
+++ b/esphome/components/pmsx003/pmsx003.cpp
@@ -2,21 +2,20 @@
 #include "esphome/core/log.h"
 #include "esphome/core/application.h"
 
-namespace esphome {
-namespace pmsx003 {
+namespace esphome::pmsx003 {
 
 static const char *const TAG = "pmsx003";
 
 static const uint8_t START_CHARACTER_1 = 0x42;
 static const uint8_t START_CHARACTER_2 = 0x4D;
 
-static const uint16_t PMS_STABILISING_MS = 30000;  // time taken for the sensor to become stable after power on in ms
+static const uint16_t STABILISING_MS = 30000;  // time taken for the sensor to become stable after power on in ms
 
-static const uint16_t PMS_CMD_MEASUREMENT_MODE_PASSIVE =
-    0x0000;  // use `PMS_CMD_MANUAL_MEASUREMENT` to trigger a measurement
-static const uint16_t PMS_CMD_MEASUREMENT_MODE_ACTIVE = 0x0001;  // automatically perform measurements
-static const uint16_t PMS_CMD_SLEEP_MODE_SLEEP = 0x0000;         // go to sleep mode
-static const uint16_t PMS_CMD_SLEEP_MODE_WAKEUP = 0x0001;        // wake up from sleep mode
+static const uint16_t CMD_MEASUREMENT_MODE_PASSIVE =
+    0x0000;  // use `Command::MANUAL_MEASUREMENT` to trigger a measurement
+static const uint16_t CMD_MEASUREMENT_MODE_ACTIVE = 0x0001;  // automatically perform measurements
+static const uint16_t CMD_SLEEP_MODE_SLEEP = 0x0000;         // go to sleep mode
+static const uint16_t CMD_SLEEP_MODE_WAKEUP = 0x0001;        // wake up from sleep mode
 
 void PMSX003Component::setup() {}
 
@@ -42,7 +41,7 @@ void PMSX003Component::dump_config() {
   LOG_SENSOR("  ", "Temperature", this->temperature_sensor_);
   LOG_SENSOR("  ", "Humidity", this->humidity_sensor_);
 
-  if (this->update_interval_ <= PMS_STABILISING_MS) {
+  if (this->update_interval_ <= STABILISING_MS) {
     ESP_LOGCONFIG(TAG, "  Mode: active continuous (sensor default)");
   } else {
     ESP_LOGCONFIG(TAG, "  Mode: passive with sleep/wake cycles");
@@ -55,44 +54,44 @@ void PMSX003Component::loop() {
   const uint32_t now = App.get_loop_component_start_time();
 
   // Initialize sensor mode on first loop
-  if (this->initialised_ == 0) {
-    if (this->update_interval_ > PMS_STABILISING_MS) {
+  if (!this->initialised_) {
+    if (this->update_interval_ > STABILISING_MS) {
       // Long update interval: use passive mode with sleep/wake cycles
-      this->send_command_(PMS_CMD_MEASUREMENT_MODE, PMS_CMD_MEASUREMENT_MODE_PASSIVE);
-      this->send_command_(PMS_CMD_SLEEP_MODE, PMS_CMD_SLEEP_MODE_WAKEUP);
+      this->send_command_(Command::MEASUREMENT_MODE, CMD_MEASUREMENT_MODE_PASSIVE);
+      this->send_command_(Command::SLEEP_MODE, CMD_SLEEP_MODE_WAKEUP);
     } else {
       // Short/zero update interval: use active continuous mode
-      this->send_command_(PMS_CMD_MEASUREMENT_MODE, PMS_CMD_MEASUREMENT_MODE_ACTIVE);
+      this->send_command_(Command::MEASUREMENT_MODE, CMD_MEASUREMENT_MODE_ACTIVE);
     }
-    this->initialised_ = 1;
+    this->initialised_ = true;
   }
 
   // If we update less often than it takes the device to stabilise, spin the fan down
   // rather than running it constantly. It does take some time to stabilise, so we
   // need to keep track of what state we're in.
-  if (this->update_interval_ > PMS_STABILISING_MS) {
+  if (this->update_interval_ > STABILISING_MS) {
     switch (this->state_) {
-      case PMSX003_STATE_IDLE:
+      case State::IDLE:
         // Power on the sensor now so it'll be ready when we hit the update time
-        if (now - this->last_update_ < (this->update_interval_ - PMS_STABILISING_MS))
+        if (now - this->last_update_ < (this->update_interval_ - STABILISING_MS))
           return;
 
-        this->state_ = PMSX003_STATE_STABILISING;
-        this->send_command_(PMS_CMD_SLEEP_MODE, PMS_CMD_SLEEP_MODE_WAKEUP);
+        this->state_ = State::STABILISING;
+        this->send_command_(Command::SLEEP_MODE, CMD_SLEEP_MODE_WAKEUP);
         this->fan_on_time_ = now;
         return;
-      case PMSX003_STATE_STABILISING:
+      case State::STABILISING:
         // wait for the sensor to be stable
-        if (now - this->fan_on_time_ < PMS_STABILISING_MS)
+        if (now - this->fan_on_time_ < STABILISING_MS)
           return;
         // consume any command responses that are in the serial buffer
         while (this->available())
           this->read_byte(&this->data_[0]);
         // Trigger a new read
-        this->send_command_(PMS_CMD_MANUAL_MEASUREMENT, 0);
-        this->state_ = PMSX003_STATE_WAITING;
+        this->send_command_(Command::MANUAL_MEASUREMENT, 0);
+        this->state_ = State::WAITING;
         break;
-      case PMSX003_STATE_WAITING:
+      case State::WAITING:
         // Just go ahead and read stuff
         break;
     }
@@ -180,27 +179,28 @@ optional<bool> PMSX003Component::check_byte_() {
 }
 
 bool PMSX003Component::check_payload_length_(uint16_t payload_length) {
+  // https://avaldebe.github.io/PyPMS/sensors/Plantower/
   switch (this->type_) {
-    case PMSX003_TYPE_X003:
+    case Type::PMSX003:
       // The expected payload length is typically 28 bytes.
       // However, a 20-byte payload check was already present in the code.
       // No official documentation was found confirming this.
       // Retaining this check to avoid breaking existing behavior.
       return payload_length == 28 || payload_length == 20;  // 2*13+2
-    case PMSX003_TYPE_5003T:
-    case PMSX003_TYPE_5003S:
+    case Type::PMS5003S:
+    case Type::PMS5003T:
       return payload_length == 28;  // 2*13+2 (Data 13 not set/reserved)
-    case PMSX003_TYPE_5003ST:
+    case Type::PMS5003ST:
       return payload_length == 36;  // 2*17+2 (Data 16 not set/reserved)
   }
   return false;
 }
 
-void PMSX003Component::send_command_(PMSX0003Command cmd, uint16_t data) {
+void PMSX003Component::send_command_(Command cmd, uint16_t data) {
   uint8_t send_data[7] = {
       START_CHARACTER_1,            // Start Byte 1
       START_CHARACTER_2,            // Start Byte 2
-      cmd,                          // Command
+      static_cast<uint8_t>(cmd),    // Command
       uint8_t((data >> 8) & 0xFF),  // Data 1
       uint8_t((data >> 0) & 0xFF),  // Data 2
       0,                            // Verify Byte 1
@@ -265,7 +265,7 @@ void PMSX003Component::parse_data_() {
   if (this->pm_particles_25um_sensor_ != nullptr)
     this->pm_particles_25um_sensor_->publish_state(pm_particles_25um);
 
-  if (this->type_ == PMSX003_TYPE_5003T) {
+  if (this->type_ == Type::PMS5003T) {
     ESP_LOGD(TAG,
              "Got PM0.3 Particles: %u Count/0.1L, PM0.5 Particles: %u Count/0.1L, PM1.0 Particles: %u Count/0.1L, "
              "PM2.5 Particles %u Count/0.1L",
@@ -289,7 +289,7 @@ void PMSX003Component::parse_data_() {
   }
 
   // Formaldehyde
-  if (this->type_ == PMSX003_TYPE_5003ST || this->type_ == PMSX003_TYPE_5003S) {
+  if (this->type_ == Type::PMS5003S || this->type_ == Type::PMS5003ST) {
     const uint16_t formaldehyde = this->get_16_bit_uint_(28);
 
     ESP_LOGD(TAG, "Got Formaldehyde: %u µg/m^3", formaldehyde);
@@ -299,8 +299,8 @@ void PMSX003Component::parse_data_() {
   }
 
   // Temperature and Humidity
-  if (this->type_ == PMSX003_TYPE_5003ST || this->type_ == PMSX003_TYPE_5003T) {
-    const uint8_t temperature_offset = (this->type_ == PMSX003_TYPE_5003T) ? 24 : 30;
+  if (this->type_ == Type::PMS5003T || this->type_ == Type::PMS5003ST) {
+    const uint8_t temperature_offset = (this->type_ == Type::PMS5003T) ? 24 : 30;
 
     const float temperature = static_cast<int16_t>(this->get_16_bit_uint_(temperature_offset)) / 10.0f;
     const float humidity = this->get_16_bit_uint_(temperature_offset + 2) / 10.0f;
@@ -314,7 +314,7 @@ void PMSX003Component::parse_data_() {
   }
 
   // Firmware Version and Error Code
-  if (this->type_ == PMSX003_TYPE_5003ST) {
+  if (this->type_ == Type::PMS5003ST) {
     const uint8_t firmware_version = this->data_[36];
     const uint8_t error_code = this->data_[37];
 
@@ -323,13 +323,12 @@ void PMSX003Component::parse_data_() {
 
   // Spin down the sensor again if we aren't going to need it until more time has
   // passed than it takes to stabilise
-  if (this->update_interval_ > PMS_STABILISING_MS) {
-    this->send_command_(PMS_CMD_SLEEP_MODE, PMS_CMD_SLEEP_MODE_SLEEP);
-    this->state_ = PMSX003_STATE_IDLE;
+  if (this->update_interval_ > STABILISING_MS) {
+    this->send_command_(Command::SLEEP_MODE, CMD_SLEEP_MODE_SLEEP);
+    this->state_ = State::IDLE;
   }
 
   this->status_clear_warning();
 }
 
-}  // namespace pmsx003
-}  // namespace esphome
+}  // namespace esphome::pmsx003
diff --git a/esphome/components/pmsx003/pmsx003.h b/esphome/components/pmsx003/pmsx003.h
index f48121800e..f2d4e68db7 100644
--- a/esphome/components/pmsx003/pmsx003.h
+++ b/esphome/components/pmsx003/pmsx003.h
@@ -5,27 +5,25 @@
 #include "esphome/components/sensor/sensor.h"
 #include "esphome/components/uart/uart.h"
 
-namespace esphome {
-namespace pmsx003 {
+namespace esphome::pmsx003 {
 
-enum PMSX0003Command : uint8_t {
-  PMS_CMD_MEASUREMENT_MODE =
-      0xE1,  // Data Options: `PMS_CMD_MEASUREMENT_MODE_PASSIVE`, `PMS_CMD_MEASUREMENT_MODE_ACTIVE`
-  PMS_CMD_MANUAL_MEASUREMENT = 0xE2,
-  PMS_CMD_SLEEP_MODE = 0xE4,  // Data Options: `PMS_CMD_SLEEP_MODE_SLEEP`, `PMS_CMD_SLEEP_MODE_WAKEUP`
+enum class Type : uint8_t {
+  PMSX003 = 0,
+  PMS5003S,
+  PMS5003T,
+  PMS5003ST,
 };
 
-enum PMSX003Type {
-  PMSX003_TYPE_X003 = 0,
-  PMSX003_TYPE_5003T,
-  PMSX003_TYPE_5003ST,
-  PMSX003_TYPE_5003S,
+enum class Command : uint8_t {
+  MEASUREMENT_MODE = 0xE1,  // Data Options: `CMD_MEASUREMENT_MODE_PASSIVE`, `CMD_MEASUREMENT_MODE_ACTIVE`
+  MANUAL_MEASUREMENT = 0xE2,
+  SLEEP_MODE = 0xE4,  // Data Options: `CMD_SLEEP_MODE_SLEEP`, `CMD_SLEEP_MODE_WAKEUP`
 };
 
-enum PMSX003State {
-  PMSX003_STATE_IDLE = 0,
-  PMSX003_STATE_STABILISING,
-  PMSX003_STATE_WAITING,
+enum class State : uint8_t {
+  IDLE = 0,
+  STABILISING,
+  WAITING,
 };
 
 class PMSX003Component : public uart::UARTDevice, public Component {
@@ -37,7 +35,7 @@ class PMSX003Component : public uart::UARTDevice, public Component {
 
   void set_update_interval(uint32_t update_interval) { this->update_interval_ = update_interval; }
 
-  void set_type(PMSX003Type type) { this->type_ = type; }
+  void set_type(Type type) { this->type_ = type; }
 
   void set_pm_1_0_std_sensor(sensor::Sensor *pm_1_0_std_sensor) { this->pm_1_0_std_sensor_ = pm_1_0_std_sensor; }
   void set_pm_2_5_std_sensor(sensor::Sensor *pm_2_5_std_sensor) { this->pm_2_5_std_sensor_ = pm_2_5_std_sensor; }
@@ -77,20 +75,20 @@ class PMSX003Component : public uart::UARTDevice, public Component {
   optional<bool> check_byte_();
   void parse_data_();
   bool check_payload_length_(uint16_t payload_length);
-  void send_command_(PMSX0003Command cmd, uint16_t data);
+  void send_command_(Command cmd, uint16_t data);
   uint16_t get_16_bit_uint_(uint8_t start_index) const {
     return encode_uint16(this->data_[start_index], this->data_[start_index + 1]);
   }
 
+  Type type_;
+  State state_{State::IDLE};
+  bool initialised_{false};
   uint8_t data_[64];
   uint8_t data_index_{0};
-  uint8_t initialised_{0};
   uint32_t fan_on_time_{0};
   uint32_t last_update_{0};
   uint32_t last_transmission_{0};
   uint32_t update_interval_{0};
-  PMSX003State state_{PMSX003_STATE_IDLE};
-  PMSX003Type type_;
 
   // "Standard Particle"
   sensor::Sensor *pm_1_0_std_sensor_{nullptr};
@@ -118,5 +116,4 @@ class PMSX003Component : public uart::UARTDevice, public Component {
   sensor::Sensor *humidity_sensor_{nullptr};
 };
 
-}  // namespace pmsx003
-}  // namespace esphome
+}  // namespace esphome::pmsx003
diff --git a/esphome/components/pmsx003/sensor.py b/esphome/components/pmsx003/sensor.py
index bebd3a01ee..4f95b1dcdb 100644
--- a/esphome/components/pmsx003/sensor.py
+++ b/esphome/components/pmsx003/sensor.py
@@ -41,33 +41,33 @@ PMSX003Component = pmsx003_ns.class_("PMSX003Component", uart.UARTDevice, cg.Com
 PMSX003Sensor = pmsx003_ns.class_("PMSX003Sensor", sensor.Sensor)
 
 TYPE_PMSX003 = "PMSX003"
+TYPE_PMS5003S = "PMS5003S"
 TYPE_PMS5003T = "PMS5003T"
 TYPE_PMS5003ST = "PMS5003ST"
-TYPE_PMS5003S = "PMS5003S"
 
-PMSX003Type = pmsx003_ns.enum("PMSX003Type")
+Type = pmsx003_ns.enum("Type", is_class=True)
 
 PMSX003_TYPES = {
-    TYPE_PMSX003: PMSX003Type.PMSX003_TYPE_X003,
-    TYPE_PMS5003T: PMSX003Type.PMSX003_TYPE_5003T,
-    TYPE_PMS5003ST: PMSX003Type.PMSX003_TYPE_5003ST,
-    TYPE_PMS5003S: PMSX003Type.PMSX003_TYPE_5003S,
+    TYPE_PMSX003: Type.PMSX003,
+    TYPE_PMS5003S: Type.PMS5003S,
+    TYPE_PMS5003T: Type.PMS5003T,
+    TYPE_PMS5003ST: Type.PMS5003ST,
 }
 
 SENSORS_TO_TYPE = {
-    CONF_PM_1_0: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_2_5: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_10_0: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_1_0_STD: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_2_5_STD: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_10_0_STD: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_0_3UM: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_0_5UM: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_1_0UM: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_2_5UM: [TYPE_PMSX003, TYPE_PMS5003T, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_5_0UM: [TYPE_PMSX003, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_PM_10_0UM: [TYPE_PMSX003, TYPE_PMS5003ST, TYPE_PMS5003S],
-    CONF_FORMALDEHYDE: [TYPE_PMS5003ST, TYPE_PMS5003S],
+    CONF_PM_1_0_STD: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
+    CONF_PM_2_5_STD: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
+    CONF_PM_10_0_STD: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
+    CONF_PM_1_0: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
+    CONF_PM_2_5: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
+    CONF_PM_10_0: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
+    CONF_PM_0_3UM: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
+    CONF_PM_0_5UM: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
+    CONF_PM_1_0UM: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
+    CONF_PM_2_5UM: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003T, TYPE_PMS5003ST],
+    CONF_PM_5_0UM: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003ST],
+    CONF_PM_10_0UM: [TYPE_PMSX003, TYPE_PMS5003S, TYPE_PMS5003ST],
+    CONF_FORMALDEHYDE: [TYPE_PMS5003S, TYPE_PMS5003ST],
     CONF_TEMPERATURE: [TYPE_PMS5003T, TYPE_PMS5003ST],
     CONF_HUMIDITY: [TYPE_PMS5003T, TYPE_PMS5003ST],
 }
diff --git a/tests/components/ch423/common.yaml b/tests/components/ch423/common.yaml
new file mode 100644
index 0000000000..ccf9170bd0
--- /dev/null
+++ b/tests/components/ch423/common.yaml
@@ -0,0 +1,36 @@
+ch423:
+  - id: ch423_hub
+    i2c_id: i2c_bus
+
+binary_sensor:
+  - platform: gpio
+    id: ch423_input
+    name: CH423 Binary Sensor
+    pin:
+      ch423: ch423_hub
+      number: 1
+      mode: INPUT
+      inverted: true
+  - platform: gpio
+    id: ch423_input_2
+    name: CH423 Binary Sensor 2
+    pin:
+      ch423: ch423_hub
+      number: 0
+      mode: INPUT
+      inverted: false
+output:
+  - platform: gpio
+    id: ch423_out_11
+    pin:
+      ch423: ch423_hub
+      number: 11
+      mode: OUTPUT_OPEN_DRAIN
+      inverted: true
+  - platform: gpio
+    id: ch423_out_23
+    pin:
+      ch423: ch423_hub
+      number: 23
+      mode: OUTPUT_OPEN_DRAIN
+      inverted: false
diff --git a/tests/components/ch423/test.esp32-idf.yaml b/tests/components/ch423/test.esp32-idf.yaml
new file mode 100644
index 0000000000..b47e39c389
--- /dev/null
+++ b/tests/components/ch423/test.esp32-idf.yaml
@@ -0,0 +1,4 @@
+packages:
+  i2c: !include ../../test_build_components/common/i2c/esp32-idf.yaml
+
+<<: !include common.yaml
diff --git a/tests/components/ch423/test.esp8266-ard.yaml b/tests/components/ch423/test.esp8266-ard.yaml
new file mode 100644
index 0000000000..4a98b9388a
--- /dev/null
+++ b/tests/components/ch423/test.esp8266-ard.yaml
@@ -0,0 +1,4 @@
+packages:
+  i2c: !include ../../test_build_components/common/i2c/esp8266-ard.yaml
+
+<<: !include common.yaml
diff --git a/tests/components/ch423/test.rp2040-ard.yaml b/tests/components/ch423/test.rp2040-ard.yaml
new file mode 100644
index 0000000000..319a7c71a6
--- /dev/null
+++ b/tests/components/ch423/test.rp2040-ard.yaml
@@ -0,0 +1,4 @@
+packages:
+  i2c: !include ../../test_build_components/common/i2c/rp2040-ard.yaml
+
+<<: !include common.yaml
diff --git a/tests/components/pmsx003/common.yaml b/tests/components/pmsx003/common.yaml
index 3c60995804..eaa3cbc3e9 100644
--- a/tests/components/pmsx003/common.yaml
+++ b/tests/components/pmsx003/common.yaml
@@ -8,11 +8,11 @@ sensor:
     pm_10_0:
       name: PM 10.0 Concentration
     pm_1_0_std:
-      name: PM 1.0 Standard Atmospher Concentration
+      name: PM 1.0 Standard Atmospheric Concentration
     pm_2_5_std:
-      name: PM 2.5 Standard Atmospher Concentration
+      name: PM 2.5 Standard Atmospheric Concentration
     pm_10_0_std:
-      name: PM 10.0 Standard Atmospher Concentration
+      name: PM 10.0 Standard Atmospheric Concentration
     pm_0_3um:
       name: Particulate Count >0.3um
     pm_0_5um:
diff --git a/tests/unit_tests/components/test_ch423.py b/tests/unit_tests/components/test_ch423.py
new file mode 100644
index 0000000000..ac79fe48fe
--- /dev/null
+++ b/tests/unit_tests/components/test_ch423.py
@@ -0,0 +1,58 @@
+"""Tests for ch423 component validation."""
+
+from unittest.mock import patch
+
+from esphome import config, yaml_util
+from esphome.core import CORE
+
+
+def test_ch423_mixed_gpio_modes_fails(tmp_path, capsys):
+    """Test that mixing input/output on GPIO pins 0-7 fails validation."""
+    test_file = tmp_path / "test.yaml"
+    test_file.write_text("""
+esphome:
+  name: test
+
+esp8266:
+  board: esp01_1m
+
+i2c:
+  sda: GPIO4
+  scl: GPIO5
+
+ch423:
+  - id: ch423_hub
+
+binary_sensor:
+  - platform: gpio
+    name: "CH423 Input 0"
+    pin:
+      ch423: ch423_hub
+      number: 0
+      mode: input
+
+switch:
+  - platform: gpio
+    name: "CH423 Output 1"
+    pin:
+      ch423: ch423_hub
+      number: 1
+      mode: output
+""")
+
+    parsed_yaml = yaml_util.load_yaml(test_file)
+
+    with (
+        patch.object(yaml_util, "load_yaml", return_value=parsed_yaml),
+        patch.object(CORE, "config_path", test_file),
+    ):
+        result = config.read_config({})
+
+    assert result is None, "Expected validation to fail with mixed GPIO modes"
+
+    # Check that the error message mentions the GPIO pin restriction
+    captured = capsys.readouterr()
+    assert (
+        "GPIO pins (0-7) must all be configured as input or all as output"
+        in captured.out
+    )