diff --git a/esphome/components/ethernet/ethernet_component.h b/esphome/components/ethernet/ethernet_component.h
index de136a02eb..4f30959e40 100644
--- a/esphome/components/ethernet/ethernet_component.h
+++ b/esphome/components/ethernet/ethernet_component.h
@@ -114,7 +114,12 @@ class EthernetComponent : public Component {
   /// @brief Set arbitratry PHY registers from config.
   void write_phy_register_(esp_eth_mac_t *mac, PHYRegister register_data);
 
+ private:
+  // Stores a pointer to a string literal (static storage duration).
+  // ONLY set from Python-generated code with string literals - never dynamic strings.
   const char *use_address_{""};
+
+ protected:
 #ifdef USE_ETHERNET_SPI
   uint8_t clk_pin_;
   uint8_t miso_pin_;
diff --git a/esphome/components/openthread/openthread.h b/esphome/components/openthread/openthread.h
index d099c321f9..3132e41696 100644
--- a/esphome/components/openthread/openthread.h
+++ b/esphome/components/openthread/openthread.h
@@ -41,6 +41,10 @@ class OpenThreadComponent : public Component {
   bool teardown_started_{false};
   bool teardown_complete_{false};
   std::function<void()> factory_reset_external_callback_;
+
+ private:
+  // Stores a pointer to a string literal (static storage duration).
+  // ONLY set from Python-generated code with string literals - never dynamic strings.
   const char *use_address_{""};
 };
 
diff --git a/esphome/components/wifi/wifi_component.h b/esphome/components/wifi/wifi_component.h
index 0c079ef1e4..4aa2ad15d4 100644
--- a/esphome/components/wifi/wifi_component.h
+++ b/esphome/components/wifi/wifi_component.h
@@ -393,7 +393,12 @@ class WiFiComponent : public Component {
   void wifi_scan_done_callback_();
 #endif
 
+ private:
+  // Stores a pointer to a string literal (static storage duration).
+  // ONLY set from Python-generated code with string literals - never dynamic strings.
   const char *use_address_{""};
+
+ protected:
   FixedVector<WiFiAP> sta_;
   std::vector<WiFiSTAPriority> sta_priorities_;
   wifi_scan_vector_t<WiFiScanResult> scan_result_;