diff --git a/esphome/components/demo/demo_climate.h b/esphome/components/demo/demo_climate.h
index 1706ba804e..c6d328b1bc 100644
--- a/esphome/components/demo/demo_climate.h
+++ b/esphome/components/demo/demo_climate.h
@@ -16,6 +16,19 @@ class DemoClimate : public climate::Climate, public Component {
  public:
   void set_type(DemoClimateType type) { type_ = type; }
   void setup() override {
+    // Set custom modes once during setup — stored on Climate base class, wired via get_traits()
+    switch (type_) {
+      case DemoClimateType::TYPE_1:
+        break;
+      case DemoClimateType::TYPE_2:
+        this->set_supported_custom_fan_modes({"Auto Low", "Auto High"});
+        this->set_supported_custom_presets({"My Preset"});
+        break;
+      case DemoClimateType::TYPE_3:
+        this->set_supported_custom_fan_modes({"Auto Low", "Auto High"});
+        break;
+    }
+    // Set initial state
     switch (type_) {
       case DemoClimateType::TYPE_1:
         this->current_temperature = 20.0;
@@ -105,14 +118,13 @@ class DemoClimate : public climate::Climate, public Component {
             climate::CLIMATE_FAN_DIFFUSE,
             climate::CLIMATE_FAN_QUIET,
         });
-        this->set_supported_custom_fan_modes({"Auto Low", "Auto High"});
+        // Custom fan modes and presets are set once in setup()
         traits.set_supported_swing_modes({
             climate::CLIMATE_SWING_OFF,
             climate::CLIMATE_SWING_BOTH,
             climate::CLIMATE_SWING_VERTICAL,
             climate::CLIMATE_SWING_HORIZONTAL,
         });
-        this->set_supported_custom_presets({"My Preset"});
         break;
       case DemoClimateType::TYPE_3:
         traits.add_feature_flags(climate::CLIMATE_SUPPORTS_CURRENT_TEMPERATURE |
@@ -123,7 +135,7 @@ class DemoClimate : public climate::Climate, public Component {
             climate::CLIMATE_MODE_HEAT,
             climate::CLIMATE_MODE_HEAT_COOL,
         });
-        this->set_supported_custom_fan_modes({"Auto Low", "Auto High"});
+        // Custom fan modes are set once in setup()
         traits.set_supported_swing_modes({
             climate::CLIMATE_SWING_OFF,
             climate::CLIMATE_SWING_HORIZONTAL,
diff --git a/esphome/components/midea/air_conditioner.cpp b/esphome/components/midea/air_conditioner.cpp
index 2a9a5e9902..50521cf238 100644
--- a/esphome/components/midea/air_conditioner.cpp
+++ b/esphome/components/midea/air_conditioner.cpp
@@ -24,19 +24,20 @@ template<typename T> void update_property(T &property, const T &value, bool &fla
 }
 
 void AirConditioner::on_status_change() {
-  // Add frost protection custom preset once when autoconf completes (merge, don't overwrite)
+  // Add frost protection custom preset once when autoconf completes
   if (this->base_.getAutoconfStatus() == dudanov::midea::AUTOCONF_OK &&
       this->base_.getCapabilities().supportFrostProtectionPreset() && !this->frost_protection_set_) {
-    auto presets = this->get_traits().get_supported_custom_presets();
+    // Read existing presets (set by codegen), append frost protection, write back
+    const auto &existing = this->get_traits().get_supported_custom_presets();
     bool found = false;
-    for (const char *p : presets) {
+    for (const char *p : existing) {
       if (strcmp(p, Constants::FREEZE_PROTECTION) == 0) {
         found = true;
         break;
       }
     }
     if (!found) {
-      std::vector<const char *> merged(presets.begin(), presets.end());
+      std::vector<const char *> merged(existing.begin(), existing.end());
       merged.push_back(Constants::FREEZE_PROTECTION);
       this->set_supported_custom_presets(merged);
     }