diff --git a/PLAN.md b/PLAN.md
new file mode 100644
index 00000000000..bcb9fe81890
--- /dev/null
+++ b/PLAN.md
@@ -0,0 +1,179 @@
+# Allow `wifi:` and `ethernet:` to coexist with boot-time link detection
+
+## Context
+
+A user wants a single YAML config that:
+- At boot, checks whether the Ethernet cable is plugged in.
+- If the cable is plugged in, brings up Ethernet only.
+- If the cable is unplugged, brings up WiFi (with `improv_serial` / `esp32_improv` provisioning fallback).
+- Restarts the device whenever the cable plug state changes.
+
+This is impossible on `dev` today. Two specific things in the codebase prevent it:
+
+1. `esphome/components/ethernet/__init__.py:52` declares `CONFLICTS_WITH = ["wifi"]`, so config validation rejects any YAML that has both.
+2. `esphome/components/ethernet/__init__.py:581-583` unconditionally turns off the ESP-IDF WiFi stack (`CONFIG_ESP_WIFI_ENABLED = False`, `CONFIG_SW_COEXIST_ENABLE = False`) when ethernet is configured, so even if the Python conflict were removed, the WiFi driver would not be linked into the firmware.
+
+ESP-IDF itself supports running WiFi and Ethernet simultaneously — they share `esp_netif` / lwIP and routing is decided per netif. ESPHome opted out of dual-stack early to save flash/RAM, but the user's use case (one or the other selected at boot) is reasonable and worth supporting.
+
+The plan removes those two blocks and adds the minimum scaffolding needed to make a "select interface at boot based on PHY link" YAML work.
+
+## Approach
+
+Five focused changes in ESPHome, then the user's YAML works directly.
+
+### 1. Drop the `CONFLICTS_WITH` and make WiFi sdkconfig conditional
+
+File: `esphome/components/ethernet/__init__.py`
+
+- Line 52: remove `CONFLICTS_WITH = ["wifi"]`.
+- Lines 580-583: only force `CONFIG_ESP_WIFI_ENABLED=False` / `CONFIG_SW_COEXIST_ENABLE=False` when the wifi component is **not** in the config. Use `CORE.config` (or a `final_validate` hook) to check.
+  ```python
+  if "wifi" not in CORE.config:
+      add_idf_sdkconfig_option("CONFIG_ESP_WIFI_ENABLED", False)
+      add_idf_sdkconfig_option("CONFIG_SW_COEXIST_ENABLE", False)
+  else:
+      add_idf_sdkconfig_option("CONFIG_SW_COEXIST_ENABLE", True)
+  ```
+  When both are enabled, `CONFIG_SW_COEXIST_ENABLE` is harmless (it gates BT/WiFi sharing) but does cost a few KB; keep an eye on flash budgets and add a warning in `dump_config` if both coexist.
+
+### 2. Add `enable_on_boot` to the ethernet schema
+
+File: `esphome/components/ethernet/__init__.py` and `ethernet_component.h` / `.cpp`
+
+Mirror the existing wifi pattern:
+- Schema (`__init__.py` around the rest of `CONFIG_SCHEMA`): `cv.Optional(CONF_ENABLE_ON_BOOT, default=True): cv.boolean`.
+- C++ (`ethernet_component.h:117+`): add `bool enable_on_boot_{true};` field and `set_enable_on_boot(bool)` setter — see the wifi equivalent at `wifi_component.h:536` and `wifi_component.h:891`.
+- `setup()` in `ethernet_component_esp32.cpp` should still install the driver (so the PHY can be probed) but should leave `started_ = false` if `enable_on_boot_` is false. The state machine at `ethernet_component_esp32.cpp:81-131` already gates everything off `started_`, so this is a small change.
+
+### 3. Add `ethernet.enable` / `ethernet.disable` actions and `ethernet.connected` / `ethernet.has_link` conditions
+
+New file: `esphome/components/ethernet/automation.h` (model after `esphome/components/wifi/automation.h:26-78`).
+
+- `EthernetEnableAction`: sets `started_ = true`, kicks the loop.
+- `EthernetDisableAction`: calls existing `powerdown()` (`ethernet_component.h:144`, already implemented at `ethernet_component_esp32.cpp:812-819`) and sets `started_ = false`.
+- `EthernetConnectedCondition`: returns `is_connected()` (already exists at `ethernet_component.h:125`).
+- `EthernetHasLinkCondition`: returns the PHY link bit. ESP-IDF exposes this via `esp_eth_ioctl(eth_handle_, ETH_CMD_G_PHY_ADDR, ...)` plus a PHY register read of `MII_BMSR` bit 2; the existing code already does PHY reads (`ethernet_component_esp32.cpp:837,857` for KSZ80XX). Wrap that into a `bool has_link()` method on `EthernetComponent` and have the condition call it.
+
+Register them in `__init__.py` next to the existing trigger registration:
+```python
+@automation.register_action("ethernet.enable", EthernetEnableAction, ...)
+@automation.register_action("ethernet.disable", EthernetDisableAction, ...)
+@automation.register_condition("ethernet.connected", EthernetConnectedCondition, ...)
+@automation.register_condition("ethernet.has_link", EthernetHasLinkCondition, ...)
+```
+
+### 4. Make the ethernet driver install (PHY probe) cheap and fast
+
+File: `esphome/components/ethernet/ethernet_component_esp32.cpp`
+
+`setup()` already does `esp_eth_driver_install` regardless of state. The new `has_link()` method must work right after `setup()` finishes, before `esp_eth_start()`. ESP-IDF reads PHY registers as soon as the driver is installed and `phy->reset()` runs, so this is already true — just expose it. No new init flow needed; the only requirement is that the user's `on_boot` priority runs **after** ethernet `setup_priority`. Ethernet's `get_setup_priority()` returns `setup_priority::WIFI` (verify in `ethernet_component_esp32.cpp`); user's `on_boot` should use `priority: 250` (after WiFi/Ethernet setup, before connection).
+
+### 5. Document the expected boot sequence
+
+Update `esphome/components/ethernet/__init__.py` docstring / `dump_config()` to spell out:
+- When both `wifi:` and `ethernet:` are present, the user owns the choice via `enable_on_boot: false` + an `on_boot` automation. ESPHome will not auto-select.
+- Flash overhead is roughly +N KB (measure during PR; document in PR description per CLAUDE.md breaking-change guidance).
+
+## Resulting YAML config
+
+Once the changes above land, this YAML works:
+
+```yaml
+esphome:
+  name: dual-net
+  on_boot:
+    # Run after both ethernet and wifi setup() but before either is told to connect.
+    priority: 250
+    then:
+      - if:
+          condition:
+            ethernet.has_link:
+          then:
+            - logger.log: "Ethernet cable detected, using Ethernet"
+            - ethernet.enable:
+          else:
+            - logger.log: "No Ethernet link, using WiFi"
+            - wifi.enable:
+
+esp32:
+  board: esp32dev
+  framework:
+    type: esp-idf
+
+ethernet:
+  type: LAN8720
+  mdc_pin: GPIO23
+  mdio_pin: GPIO18
+  clk_mode: GPIO0_IN
+  phy_addr: 0
+  enable_on_boot: false   # NEW — added in change #2
+  on_disconnect:
+    then:
+      - logger.log: "Ethernet disconnected, restarting"
+      - delay: 2s
+      - button.press: restart_btn
+
+wifi:
+  ssid: !secret wifi_ssid
+  password: !secret wifi_password
+  enable_on_boot: false   # already exists today
+  ap:                     # AP fallback for captive_portal / improv
+    ssid: "Dual-Net Fallback"
+
+captive_portal:
+improv_serial:
+
+# esp32_improv is optional — only if you have a button and want BLE provisioning
+# esp32_improv:
+#   authorizer: !push_button gpio0
+
+button:
+  - platform: restart
+    id: restart_btn
+    name: "Restart"
+
+# Detect cable insertion when running on WiFi: poll PHY link, restart if it changes.
+interval:
+  - interval: 5s
+    then:
+      - if:
+          condition:
+            and:
+              - not: ethernet.connected
+              - ethernet.has_link
+          then:
+            - logger.log: "Ethernet cable plugged in, restarting"
+            - button.press: restart_btn
+```
+
+Notes on the YAML:
+- `ethernet.has_link` is the new cheap PHY-only check (change #3); it works even when ethernet is disabled because the driver was installed in `setup()`.
+- `ethernet.enable` / `wifi.enable` are mutually exclusive in this YAML — only one path runs at boot.
+- The `interval` block handles "cable plugged in while running on WiFi" → restart so ethernet takes over on the next boot. The existing `on_disconnect` trigger handles the inverse (cable unplugged while on ethernet → restart).
+- `improv_serial` works as long as wifi is enabled (it depends on wifi per `improv_serial/__init__.py:10`).
+
+## Critical files to modify
+
+- `esphome/components/ethernet/__init__.py` — drop `CONFLICTS_WITH` (line 52), make sdkconfig conditional (lines 580-583), add `enable_on_boot` schema option, register new actions/conditions.
+- `esphome/components/ethernet/ethernet_component.h` — add `enable_on_boot_` field, `set_enable_on_boot`, `has_link()` method.
+- `esphome/components/ethernet/ethernet_component_esp32.cpp` — implement `has_link()` via existing PHY read path (model after KSZ80XX read at lines 837/857), gate `started_` initialization on `enable_on_boot_`.
+- `esphome/components/ethernet/ethernet_component_rp2040.cpp` — implement `has_link()` using the existing `linkStatus()` Arduino API (already used at line 117 in that file).
+- `esphome/components/ethernet/automation.h` — new file, model after `esphome/components/wifi/automation.h`.
+- `tests/components/ethernet/` — add `common.yaml` test that combines `wifi:` + `ethernet:` and uses the new actions/conditions.
+
+## Reused existing infrastructure
+
+- WiFi already has `enable_on_boot` (`wifi_component.h:536, 891`), `wifi.enable` / `wifi.disable` actions (`wifi/automation.h:26, 31`), and `wifi.connected` / `wifi.enabled` / `wifi.ap_active` conditions.
+- Ethernet already has `is_connected()` (`ethernet_component.h:125`), `powerdown()` (`ethernet_component.h:144`), `on_connect` / `on_disconnect` triggers (`ethernet_component.h:185-190`).
+- `improv_serial` (`esphome/components/improv_serial/__init__.py`) and `captive_portal` (`esphome/components/captive_portal/__init__.py`) need no changes; they just need wifi to be enabled at boot.
+- Restart action: `button.press` on a `platform: restart` button (used in the YAML above) — no need for a new action; this matches existing ESPHome patterns.
+
+## Verification
+
+1. Config validation: `esphome config dual-net.yaml` should pass (today it errors with `Component conflicts with wifi`).
+2. Compile both paths: `esphome compile` with cable connected and disconnected — verify only one stack negotiates an IP.
+3. Hotplug: boot with cable, then unplug → device restarts within ~5s, comes up on WiFi. Boot without cable, then plug in → device restarts within ~5s, comes up on Ethernet.
+4. Improv fallback: boot without cable and with bad WiFi credentials → `improv_serial` should accept new credentials over USB.
+5. Run `pytest tests/component_tests/ethernet` and the YAML compile-test under `tests/components/ethernet/test.esp32-idf.yaml` (add a new `dual_net` variant).
+6. Flash size sanity check: compare `.bin` size against `dev` for an ethernet-only config to confirm the conditional sdkconfig change doesn't regress single-stack builds.
+7. Memory check at runtime: confirm with `top` / `esp_get_free_heap_size()` that boot-time selection actually leaves the unused stack idle (WiFi shouldn't allocate buffers if `wifi.enable` is never called).
diff --git a/esphome/components/ethernet/__init__.py b/esphome/components/ethernet/__init__.py
index 10f9a73863d..a89d96ebd39 100644
--- a/esphome/components/ethernet/__init__.py
+++ b/esphome/components/ethernet/__init__.py
@@ -13,6 +13,7 @@ from esphome.const import (
     CONF_DNS1,
     CONF_DNS2,
     CONF_DOMAIN,
+    CONF_ENABLE_ON_BOOT,
     CONF_GATEWAY,
     CONF_ID,
     CONF_INTERRUPT_PIN,
@@ -49,7 +50,6 @@ from esphome.core import (
 import esphome.final_validate as fv
 from esphome.types import ConfigType
 
-CONFLICTS_WITH = ["wifi"]
 AUTO_LOAD = ["network"]
 LOGGER = logging.getLogger(__name__)
 
@@ -219,6 +219,15 @@ MANUAL_IP_SCHEMA = cv.Schema(
 EthernetComponent = ethernet_ns.class_("EthernetComponent", cg.Component)
 ManualIP = ethernet_ns.struct("ManualIP")
 
+EthernetConnectedCondition = ethernet_ns.class_(
+    "EthernetConnectedCondition", automation.Condition
+)
+EthernetHasLinkCondition = ethernet_ns.class_(
+    "EthernetHasLinkCondition", automation.Condition
+)
+EthernetEnableAction = ethernet_ns.class_("EthernetEnableAction", automation.Action)
+EthernetDisableAction = ethernet_ns.class_("EthernetDisableAction", automation.Action)
+
 
 def _is_framework_spi_polling_mode_supported() -> bool:
     """Check if ESP-IDF framework supports SPI polling mode (ESP32 only).
@@ -349,6 +358,7 @@ BASE_SCHEMA = cv.Schema(
         cv.Optional(CONF_DOMAIN, default=".local"): cv.domain_name,
         cv.Optional(CONF_USE_ADDRESS): cv.string_strict,
         cv.Optional(CONF_MAC_ADDRESS): cv.mac_address,
+        cv.Optional(CONF_ENABLE_ON_BOOT, default=True): cv.boolean,
         cv.Optional(CONF_ON_CONNECT): automation.validate_automation(single=True),
         cv.Optional(CONF_ON_DISCONNECT): automation.validate_automation(single=True),
     }
@@ -508,6 +518,10 @@ async def to_code(config):
     if mac_address := config.get(CONF_MAC_ADDRESS):
         cg.add(var.set_fixed_mac(mac_address.parts))
 
+    # enable_on_boot defaults to true in C++ - only set if false
+    if not config[CONF_ENABLE_ON_BOOT]:
+        cg.add(var.set_enable_on_boot(False))
+
     cg.add_define("USE_ETHERNET")
 
     if on_connect_config := config.get(CONF_ON_CONNECT):
@@ -577,10 +591,12 @@ async def _to_code_esp32(var: cg.Pvariable, config: ConfigType) -> None:
             )
             cg.add(var.add_phy_register(reg))
 
-    # Disable WiFi when using Ethernet to save memory
-    add_idf_sdkconfig_option("CONFIG_ESP_WIFI_ENABLED", False)
-    # Also disable WiFi/BT coexistence since WiFi is disabled
-    add_idf_sdkconfig_option("CONFIG_SW_COEXIST_ENABLE", False)
+    # When wifi is not also configured, disable the WiFi stack to save flash/RAM.
+    # When both are configured the user wants dual-stack (e.g. boot-time link
+    # selection), so leave WiFi enabled.
+    if "wifi" not in CORE.config:
+        add_idf_sdkconfig_option("CONFIG_ESP_WIFI_ENABLED", False)
+        add_idf_sdkconfig_option("CONFIG_SW_COEXIST_ENABLE", False)
 
     # Re-enable ESP-IDF's Ethernet driver (excluded by default to save compile time)
     include_builtin_idf_component("esp_eth")
@@ -716,3 +732,31 @@ def _filter_source_files() -> list[str]:
 
 
 FILTER_SOURCE_FILES = _filter_source_files
+
+
+@automation.register_condition(
+    "ethernet.connected", EthernetConnectedCondition, cv.Schema({})
+)
+async def ethernet_connected_to_code(config, condition_id, template_arg, args):
+    return cg.new_Pvariable(condition_id, template_arg)
+
+
+@automation.register_condition(
+    "ethernet.has_link", EthernetHasLinkCondition, cv.Schema({})
+)
+async def ethernet_has_link_to_code(config, condition_id, template_arg, args):
+    return cg.new_Pvariable(condition_id, template_arg)
+
+
+@automation.register_action(
+    "ethernet.enable", EthernetEnableAction, cv.Schema({}), synchronous=True
+)
+async def ethernet_enable_to_code(config, action_id, template_arg, args):
+    return cg.new_Pvariable(action_id, template_arg)
+
+
+@automation.register_action(
+    "ethernet.disable", EthernetDisableAction, cv.Schema({}), synchronous=True
+)
+async def ethernet_disable_to_code(config, action_id, template_arg, args):
+    return cg.new_Pvariable(action_id, template_arg)
diff --git a/esphome/components/ethernet/automation.h b/esphome/components/ethernet/automation.h
new file mode 100644
index 00000000000..24efd78406e
--- /dev/null
+++ b/esphome/components/ethernet/automation.h
@@ -0,0 +1,31 @@
+#pragma once
+
+#include "esphome/core/defines.h"
+#ifdef USE_ETHERNET
+#include "esphome/core/automation.h"
+#include "ethernet_component.h"
+
+namespace esphome::ethernet {
+
+template<typename... Ts> class EthernetConnectedCondition : public Condition<Ts...> {
+ public:
+  bool check(const Ts &...x) override { return global_eth_component->is_connected(); }
+};
+
+template<typename... Ts> class EthernetHasLinkCondition : public Condition<Ts...> {
+ public:
+  bool check(const Ts &...x) override { return global_eth_component->has_link(); }
+};
+
+template<typename... Ts> class EthernetEnableAction : public Action<Ts...> {
+ public:
+  void play(const Ts &...x) override { global_eth_component->enable(); }
+};
+
+template<typename... Ts> class EthernetDisableAction : public Action<Ts...> {
+ public:
+  void play(const Ts &...x) override { global_eth_component->disable(); }
+};
+
+}  // namespace esphome::ethernet
+#endif
diff --git a/esphome/components/ethernet/ethernet_component.h b/esphome/components/ethernet/ethernet_component.h
index 17c84ee9543..6c48a56f8ab 100644
--- a/esphome/components/ethernet/ethernet_component.h
+++ b/esphome/components/ethernet/ethernet_component.h
@@ -124,6 +124,18 @@ class EthernetComponent final : public Component {
   void on_powerdown() override { powerdown(); }
   bool is_connected() { return this->state_ == EthernetComponentState::CONNECTED; }
 
+  // Returns true when the PHY reports the cable is plugged in and link is up.
+  // Safe to call once setup() has completed - does not require the connection
+  // state machine to have run.
+  bool has_link();
+
+  // Start the ethernet connection state machine. No-op if already started.
+  void enable();
+  // Stop the ethernet connection state machine and power down the interface.
+  void disable();
+
+  void set_enable_on_boot(bool enable_on_boot) { this->enable_on_boot_ = enable_on_boot; }
+
   void set_type(EthernetType type);
 #ifdef USE_ETHERNET_MANUAL_IP
   void set_manual_ip(const ManualIP &manual_ip);
@@ -284,6 +296,7 @@ class EthernetComponent final : public Component {
   // Group all uint8_t types together (enums and bools)
   EthernetType type_{ETHERNET_TYPE_UNKNOWN};
   EthernetComponentState state_{EthernetComponentState::STOPPED};
+  bool enable_on_boot_{true};
   bool started_{false};
   bool connected_{false};
   bool got_ipv4_address_{false};
diff --git a/esphome/components/ethernet/ethernet_component_esp32.cpp b/esphome/components/ethernet/ethernet_component_esp32.cpp
index d4585bf100b..747f338f091 100644
--- a/esphome/components/ethernet/ethernet_component_esp32.cpp
+++ b/esphome/components/ethernet/ethernet_component_esp32.cpp
@@ -370,9 +370,41 @@ void EthernetComponent::setup() {
   ESPHL_ERROR_CHECK(err, "GOT IPv6 event handler register error");
 #endif /* USE_NETWORK_IPV6 */
 
-  /* start Ethernet driver state machine */
-  err = esp_eth_start(this->eth_handle_);
-  ESPHL_ERROR_CHECK(err, "ETH start error");
+  if (this->enable_on_boot_) {
+    /* start Ethernet driver state machine */
+    err = esp_eth_start(this->eth_handle_);
+    ESPHL_ERROR_CHECK(err, "ETH start error");
+  } else {
+    ESP_LOGCONFIG(TAG, "Ethernet not started (enable_on_boot is false)");
+  }
+}
+
+void EthernetComponent::enable() {
+  if (this->started_ || this->eth_handle_ == nullptr)
+    return;
+  esp_err_t err = esp_eth_start(this->eth_handle_);
+  if (err != ESP_OK) {
+    ESP_LOGE(TAG, "ETH start error: (%d) %s", err, esp_err_to_name(err));
+    return;
+  }
+  this->enable_loop_soon_any_context();
+}
+
+void EthernetComponent::disable() {
+  if (!this->started_ || this->eth_handle_ == nullptr)
+    return;
+  esp_err_t err = esp_eth_stop(this->eth_handle_);
+  if (err != ESP_OK) {
+    ESP_LOGE(TAG, "ETH stop error: (%d) %s", err, esp_err_to_name(err));
+    return;
+  }
+  this->enable_loop_soon_any_context();
+}
+
+bool EthernetComponent::has_link() {
+  // connected_ is set by ETHERNET_EVENT_CONNECTED and cleared by ETHERNET_EVENT_DISCONNECTED.
+  // It reflects the PHY link state once the driver has been started.
+  return this->connected_;
 }
 
 void EthernetComponent::dump_config() {
diff --git a/esphome/components/ethernet/ethernet_component_rp2040.cpp b/esphome/components/ethernet/ethernet_component_rp2040.cpp
index ef7bd463328..54263491fb9 100644
--- a/esphome/components/ethernet/ethernet_component_rp2040.cpp
+++ b/esphome/components/ethernet/ethernet_component_rp2040.cpp
@@ -95,6 +95,34 @@ void EthernetComponent::setup() {
   // when the link is actually up. Setting it prematurely causes
   // a "Starting → Stopped → Starting" log sequence because the chip
   // needs time after begin() before the PHY link is ready.
+
+  if (!this->enable_on_boot_) {
+    ESP_LOGCONFIG(TAG, "Ethernet not started (enable_on_boot is false)");
+  }
+}
+
+void EthernetComponent::enable() {
+  this->enable_on_boot_ = true;
+  this->enable_loop_soon_any_context();
+}
+
+void EthernetComponent::disable() {
+  this->enable_on_boot_ = false;
+  this->started_ = false;
+  this->connected_ = false;
+  this->state_ = EthernetComponentState::STOPPED;
+  this->enable_loop_soon_any_context();
+}
+
+bool EthernetComponent::has_link() {
+  if (this->eth_ == nullptr)
+    return false;
+#if defined(USE_ETHERNET_W5100)
+  // W5100 cannot detect link state - assume up after successful begin()
+  return true;
+#else
+  return this->eth_->linkStatus() == LinkON;
+#endif
 }
 
 void EthernetComponent::loop() {
@@ -107,7 +135,7 @@ void EthernetComponent::loop() {
   // connected() reads netif->ip_addr without LwIPLock, but this is a single
   // 32-bit aligned read (atomic on ARM) — worst case is a one-iteration-stale
   // value, which is benign for polling.
-  if (this->eth_ != nullptr && now - this->last_link_check_ >= LINK_CHECK_INTERVAL) {
+  if (this->eth_ != nullptr && this->enable_on_boot_ && now - this->last_link_check_ >= LINK_CHECK_INTERVAL) {
     this->last_link_check_ = now;
 #if defined(USE_ETHERNET_W5100)
     // W5100 can't detect link (isLinkDetectable() returns false), so linkStatus()
diff --git a/tests/components/ethernet/common-dual-net.yaml b/tests/components/ethernet/common-dual-net.yaml
new file mode 100644
index 00000000000..2da6d107cd5
--- /dev/null
+++ b/tests/components/ethernet/common-dual-net.yaml
@@ -0,0 +1,70 @@
+esphome:
+  on_boot:
+    # Run after both ethernet and wifi setup() but before either has had time
+    # to connect. Decide which interface to use based on the PHY link state.
+    priority: 250
+    then:
+      - delay: 3s  # give the PHY time to autonegotiate
+      - if:
+          condition:
+            ethernet.has_link:
+          then:
+            - logger.log: "Ethernet cable detected, using Ethernet"
+            - wifi.disable
+            - ethernet.enable
+          else:
+            - logger.log: "No Ethernet link, using WiFi"
+            - ethernet.disable
+            - wifi.enable
+
+ethernet:
+  type: LAN8720
+  mdc_pin: 23
+  mdio_pin: 32
+  clk:
+    pin: 0
+    mode: CLK_EXT_IN
+  phy_addr: 0
+  power_pin: 33
+  enable_on_boot: false
+  on_disconnect:
+    then:
+      - logger.log: "Ethernet disconnected, restarting"
+      - delay: 2s
+      - button.press: restart_btn
+
+wifi:
+  ssid: MySSID
+  password: password1
+  enable_on_boot: false
+  ap:
+    ssid: "Dual-Net Fallback"
+
+button:
+  - platform: restart
+    id: restart_btn
+    name: "Restart"
+
+# Detect cable insertion when running on WiFi: poll PHY link, restart if it
+# changes. The ethernet driver is installed but stopped; calling has_link
+# requires it to be enabled briefly. Restart on a positive transition.
+interval:
+  - interval: 30s
+    then:
+      - if:
+          condition:
+            and:
+              - wifi.connected:
+              - not:
+                  ethernet.connected:
+          then:
+            - ethernet.enable
+            - delay: 3s
+            - if:
+                condition:
+                  ethernet.has_link:
+                then:
+                  - logger.log: "Ethernet cable plugged in, restarting"
+                  - button.press: restart_btn
+                else:
+                  - ethernet.disable
diff --git a/tests/components/ethernet/test-dual-net.esp32-idf.yaml b/tests/components/ethernet/test-dual-net.esp32-idf.yaml
new file mode 100644
index 00000000000..e9243169eca
--- /dev/null
+++ b/tests/components/ethernet/test-dual-net.esp32-idf.yaml
@@ -0,0 +1 @@
+<<: !include common-dual-net.yaml