diff --git a/esphome/components/api/api.proto b/esphome/components/api/api.proto
index 20645fc47b..7a50fa6b17 100644
--- a/esphome/components/api/api.proto
+++ b/esphome/components/api/api.proto
@@ -1000,9 +1000,9 @@ message ListEntitiesClimateResponse {
   bool supports_action = 12; // Deprecated: use feature_flags
   repeated ClimateFanMode supported_fan_modes = 13 [(container_pointer_no_template) = "climate::ClimateFanModeMask"];
   repeated ClimateSwingMode supported_swing_modes = 14 [(container_pointer_no_template) = "climate::ClimateSwingModeMask"];
-  repeated string supported_custom_fan_modes = 15 [(container_pointer) = "std::vector"];
+  repeated string supported_custom_fan_modes = 15 [(container_pointer_no_template) = "std::vector<const char *>"];
   repeated ClimatePreset supported_presets = 16 [(container_pointer_no_template) = "climate::ClimatePresetMask"];
-  repeated string supported_custom_presets = 17 [(container_pointer) = "std::vector"];
+  repeated string supported_custom_presets = 17 [(container_pointer_no_template) = "std::vector<const char *>"];
   bool disabled_by_default = 18;
   string icon = 19 [(field_ifdef) = "USE_ENTITY_ICON"];
   EntityCategory entity_category = 20;
diff --git a/esphome/components/api/api_pb2.cpp b/esphome/components/api/api_pb2.cpp
index 0673d35518..dfa1a1320f 100644
--- a/esphome/components/api/api_pb2.cpp
+++ b/esphome/components/api/api_pb2.cpp
@@ -1179,14 +1179,14 @@ void ListEntitiesClimateResponse::encode(ProtoWriteBuffer buffer) const {
   for (const auto &it : *this->supported_swing_modes) {
     buffer.encode_uint32(14, static_cast<uint32_t>(it), true);
   }
-  for (const auto &it : *this->supported_custom_fan_modes) {
-    buffer.encode_string(15, it, true);
+  for (const char *it : *this->supported_custom_fan_modes) {
+    buffer.encode_string(15, it, strlen(it), true);
   }
   for (const auto &it : *this->supported_presets) {
     buffer.encode_uint32(16, static_cast<uint32_t>(it), true);
   }
-  for (const auto &it : *this->supported_custom_presets) {
-    buffer.encode_string(17, it, true);
+  for (const char *it : *this->supported_custom_presets) {
+    buffer.encode_string(17, it, strlen(it), true);
   }
   buffer.encode_bool(18, this->disabled_by_default);
 #ifdef USE_ENTITY_ICON
@@ -1229,8 +1229,8 @@ void ListEntitiesClimateResponse::calculate_size(ProtoSize &size) const {
     }
   }
   if (!this->supported_custom_fan_modes->empty()) {
-    for (const auto &it : *this->supported_custom_fan_modes) {
-      size.add_length_force(1, it.size());
+    for (const char *it : *this->supported_custom_fan_modes) {
+      size.add_length_force(1, strlen(it));
     }
   }
   if (!this->supported_presets->empty()) {
@@ -1239,8 +1239,8 @@ void ListEntitiesClimateResponse::calculate_size(ProtoSize &size) const {
     }
   }
   if (!this->supported_custom_presets->empty()) {
-    for (const auto &it : *this->supported_custom_presets) {
-      size.add_length_force(2, it.size());
+    for (const char *it : *this->supported_custom_presets) {
+      size.add_length_force(2, strlen(it));
     }
   }
   size.add_bool(2, this->disabled_by_default);
diff --git a/esphome/components/api/api_pb2.h b/esphome/components/api/api_pb2.h
index 89f16044d7..716f1a6e9b 100644
--- a/esphome/components/api/api_pb2.h
+++ b/esphome/components/api/api_pb2.h
@@ -1384,9 +1384,9 @@ class ListEntitiesClimateResponse final : public InfoResponseProtoMessage {
   bool supports_action{false};
   const climate::ClimateFanModeMask *supported_fan_modes{};
   const climate::ClimateSwingModeMask *supported_swing_modes{};
-  const std::vector<std::string> *supported_custom_fan_modes{};
+  const std::vector<const char *> *supported_custom_fan_modes{};
   const climate::ClimatePresetMask *supported_presets{};
-  const std::vector<std::string> *supported_custom_presets{};
+  const std::vector<const char *> *supported_custom_presets{};
   float visual_current_temperature_step{0.0f};
   bool supports_current_humidity{false};
   bool supports_target_humidity{false};
diff --git a/esphome/components/bedjet/climate/bedjet_climate.cpp b/esphome/components/bedjet/climate/bedjet_climate.cpp
index f22d312b5a..65fa092e8e 100644
--- a/esphome/components/bedjet/climate/bedjet_climate.cpp
+++ b/esphome/components/bedjet/climate/bedjet_climate.cpp
@@ -48,7 +48,7 @@ void BedJetClimate::dump_config() {
     ESP_LOGCONFIG(TAG, "   - %s", LOG_STR_ARG(climate_fan_mode_to_string(mode)));
   }
   for (const auto &mode : traits.get_supported_custom_fan_modes()) {
-    ESP_LOGCONFIG(TAG, "   - %s (c)", mode.c_str());
+    ESP_LOGCONFIG(TAG, "   - %s (c)", mode);
   }
 
   ESP_LOGCONFIG(TAG, "  Supported presets:");
@@ -56,7 +56,7 @@ void BedJetClimate::dump_config() {
     ESP_LOGCONFIG(TAG, "   - %s", LOG_STR_ARG(climate_preset_to_string(preset)));
   }
   for (const auto &preset : traits.get_supported_custom_presets()) {
-    ESP_LOGCONFIG(TAG, "   - %s (c)", preset.c_str());
+    ESP_LOGCONFIG(TAG, "   - %s (c)", preset);
   }
 }
 
diff --git a/esphome/components/bedjet/climate/bedjet_climate.h b/esphome/components/bedjet/climate/bedjet_climate.h
index dbbb73aeae..05f4a849e0 100644
--- a/esphome/components/bedjet/climate/bedjet_climate.h
+++ b/esphome/components/bedjet/climate/bedjet_climate.h
@@ -50,21 +50,13 @@ class BedJetClimate : public climate::Climate, public BedJetClient, public Polli
         // Climate doesn't have a "TURBO" mode, but we can use the BOOST preset instead.
         climate::CLIMATE_PRESET_BOOST,
     });
+    // String literals are stored in rodata and valid for program lifetime
     traits.set_supported_custom_presets({
-        // We could fetch biodata from bedjet and set these names that way.
-        // But then we have to invert the lookup in order to send the right preset.
-        // For now, we can leave them as M1-3 to match the remote buttons.
-        // EXT HT added to match remote button.
-        "EXT HT",
+        this->heating_mode_ == HEAT_MODE_EXTENDED ? "LTD HT" : "EXT HT",
         "M1",
         "M2",
         "M3",
     });
-    if (this->heating_mode_ == HEAT_MODE_EXTENDED) {
-      traits.add_supported_custom_preset("LTD HT");
-    } else {
-      traits.add_supported_custom_preset("EXT HT");
-    }
     traits.set_visual_min_temperature(19.0);
     traits.set_visual_max_temperature(43.0);
     traits.set_visual_temperature_step(1.0);
diff --git a/esphome/components/climate/climate.cpp b/esphome/components/climate/climate.cpp
index 944934edbf..64f43ffd80 100644
--- a/esphome/components/climate/climate.cpp
+++ b/esphome/components/climate/climate.cpp
@@ -387,8 +387,8 @@ void Climate::save_state_() {
     const auto &supported = traits.get_supported_custom_fan_modes();
     // std::vector maintains insertion order
     size_t i = 0;
-    for (const auto &mode : supported) {
-      if (mode == custom_fan_mode) {
+    for (const char *mode : supported) {
+      if (strcmp(mode, custom_fan_mode.value().c_str()) == 0) {
         state.custom_fan_mode = i;
         break;
       }
@@ -404,8 +404,8 @@ void Climate::save_state_() {
     const auto &supported = traits.get_supported_custom_presets();
     // std::vector maintains insertion order
     size_t i = 0;
-    for (const auto &preset : supported) {
-      if (preset == custom_preset) {
+    for (const char *preset : supported) {
+      if (strcmp(preset, custom_preset.value().c_str()) == 0) {
         state.custom_preset = i;
         break;
       }
@@ -527,7 +527,7 @@ ClimateCall ClimateDeviceRestoreState::to_call(Climate *climate) {
   if (this->uses_custom_fan_mode) {
     if (this->custom_fan_mode < traits.get_supported_custom_fan_modes().size()) {
       call.fan_mode_.reset();
-      call.custom_fan_mode_ = *std::next(traits.get_supported_custom_fan_modes().cbegin(), this->custom_fan_mode);
+      call.custom_fan_mode_ = std::string(traits.get_supported_custom_fan_modes()[this->custom_fan_mode]);
     }
   } else if (traits.supports_fan_mode(this->fan_mode)) {
     call.set_fan_mode(this->fan_mode);
@@ -535,7 +535,7 @@ ClimateCall ClimateDeviceRestoreState::to_call(Climate *climate) {
   if (this->uses_custom_preset) {
     if (this->custom_preset < traits.get_supported_custom_presets().size()) {
       call.preset_.reset();
-      call.custom_preset_ = *std::next(traits.get_supported_custom_presets().cbegin(), this->custom_preset);
+      call.custom_preset_ = std::string(traits.get_supported_custom_presets()[this->custom_preset]);
     }
   } else if (traits.supports_preset(this->preset)) {
     call.set_preset(this->preset);
@@ -562,7 +562,7 @@ void ClimateDeviceRestoreState::apply(Climate *climate) {
   if (this->uses_custom_fan_mode) {
     if (this->custom_fan_mode < traits.get_supported_custom_fan_modes().size()) {
       climate->fan_mode.reset();
-      climate->custom_fan_mode = *std::next(traits.get_supported_custom_fan_modes().cbegin(), this->custom_fan_mode);
+      climate->custom_fan_mode = std::string(traits.get_supported_custom_fan_modes()[this->custom_fan_mode]);
     }
   } else if (traits.supports_fan_mode(this->fan_mode)) {
     climate->fan_mode = this->fan_mode;
@@ -571,7 +571,7 @@ void ClimateDeviceRestoreState::apply(Climate *climate) {
   if (this->uses_custom_preset) {
     if (this->custom_preset < traits.get_supported_custom_presets().size()) {
       climate->preset.reset();
-      climate->custom_preset = *std::next(traits.get_supported_custom_presets().cbegin(), this->custom_preset);
+      climate->custom_preset = std::string(traits.get_supported_custom_presets()[this->custom_preset]);
     }
   } else if (traits.supports_preset(this->preset)) {
     climate->preset = this->preset;
@@ -656,8 +656,8 @@ void Climate::dump_traits_(const char *tag) {
   }
   if (!traits.get_supported_custom_fan_modes().empty()) {
     ESP_LOGCONFIG(tag, "  Supported custom fan modes:");
-    for (const std::string &s : traits.get_supported_custom_fan_modes())
-      ESP_LOGCONFIG(tag, "  - %s", s.c_str());
+    for (const char *s : traits.get_supported_custom_fan_modes())
+      ESP_LOGCONFIG(tag, "  - %s", s);
   }
   if (!traits.get_supported_presets().empty()) {
     ESP_LOGCONFIG(tag, "  Supported presets:");
@@ -666,8 +666,8 @@ void Climate::dump_traits_(const char *tag) {
   }
   if (!traits.get_supported_custom_presets().empty()) {
     ESP_LOGCONFIG(tag, "  Supported custom presets:");
-    for (const std::string &s : traits.get_supported_custom_presets())
-      ESP_LOGCONFIG(tag, "  - %s", s.c_str());
+    for (const char *s : traits.get_supported_custom_presets())
+      ESP_LOGCONFIG(tag, "  - %s", s);
   }
   if (!traits.get_supported_swing_modes().empty()) {
     ESP_LOGCONFIG(tag, "  Supported swing modes:");
diff --git a/esphome/components/climate/climate_traits.h b/esphome/components/climate/climate_traits.h
index 1161a54f4e..f0e0dbe02b 100644
--- a/esphome/components/climate/climate_traits.h
+++ b/esphome/components/climate/climate_traits.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <cstring>
 #include <vector>
 #include "climate_mode.h"
 #include "esphome/core/finite_set_mask.h"
@@ -18,16 +19,6 @@ using ClimateSwingModeMask =
     FiniteSetMask<ClimateSwingMode, DefaultBitPolicy<ClimateSwingMode, CLIMATE_SWING_HORIZONTAL + 1>>;
 using ClimatePresetMask = FiniteSetMask<ClimatePreset, DefaultBitPolicy<ClimatePreset, CLIMATE_PRESET_ACTIVITY + 1>>;
 
-// Lightweight linear search for small vectors (1-20 items)
-// Avoids std::find template overhead
-template<typename T> inline bool vector_contains(const std::vector<T> &vec, const T &value) {
-  for (const auto &item : vec) {
-    if (item == value)
-      return true;
-  }
-  return false;
-}
-
 /** This class contains all static data for climate devices.
  *
  * All climate devices must support these features:
@@ -128,46 +119,52 @@ class ClimateTraits {
 
   void set_supported_fan_modes(ClimateFanModeMask modes) { this->supported_fan_modes_ = modes; }
   void add_supported_fan_mode(ClimateFanMode mode) { this->supported_fan_modes_.insert(mode); }
-  void add_supported_custom_fan_mode(const std::string &mode) { this->supported_custom_fan_modes_.push_back(mode); }
   bool supports_fan_mode(ClimateFanMode fan_mode) const { return this->supported_fan_modes_.count(fan_mode); }
   bool get_supports_fan_modes() const {
     return !this->supported_fan_modes_.empty() || !this->supported_custom_fan_modes_.empty();
   }
   const ClimateFanModeMask &get_supported_fan_modes() const { return this->supported_fan_modes_; }
 
-  void set_supported_custom_fan_modes(std::vector<std::string> supported_custom_fan_modes) {
-    this->supported_custom_fan_modes_ = std::move(supported_custom_fan_modes);
+  void set_supported_custom_fan_modes(std::initializer_list<const char *> modes) {
+    this->supported_custom_fan_modes_ = modes;
   }
-  void set_supported_custom_fan_modes(std::initializer_list<std::string> modes) {
+  void set_supported_custom_fan_modes(const std::vector<const char *> &modes) {
     this->supported_custom_fan_modes_ = modes;
   }
   template<size_t N> void set_supported_custom_fan_modes(const char *const (&modes)[N]) {
     this->supported_custom_fan_modes_.assign(modes, modes + N);
   }
-  const std::vector<std::string> &get_supported_custom_fan_modes() const { return this->supported_custom_fan_modes_; }
+  const std::vector<const char *> &get_supported_custom_fan_modes() const { return this->supported_custom_fan_modes_; }
   bool supports_custom_fan_mode(const std::string &custom_fan_mode) const {
-    return vector_contains(this->supported_custom_fan_modes_, custom_fan_mode);
+    for (const char *mode : this->supported_custom_fan_modes_) {
+      if (strcmp(mode, custom_fan_mode.c_str()) == 0)
+        return true;
+    }
+    return false;
   }
 
   void set_supported_presets(ClimatePresetMask presets) { this->supported_presets_ = presets; }
   void add_supported_preset(ClimatePreset preset) { this->supported_presets_.insert(preset); }
-  void add_supported_custom_preset(const std::string &preset) { this->supported_custom_presets_.push_back(preset); }
   bool supports_preset(ClimatePreset preset) const { return this->supported_presets_.count(preset); }
   bool get_supports_presets() const { return !this->supported_presets_.empty(); }
   const ClimatePresetMask &get_supported_presets() const { return this->supported_presets_; }
 
-  void set_supported_custom_presets(std::vector<std::string> supported_custom_presets) {
-    this->supported_custom_presets_ = std::move(supported_custom_presets);
+  void set_supported_custom_presets(std::initializer_list<const char *> presets) {
+    this->supported_custom_presets_ = presets;
   }
-  void set_supported_custom_presets(std::initializer_list<std::string> presets) {
+  void set_supported_custom_presets(const std::vector<const char *> &presets) {
     this->supported_custom_presets_ = presets;
   }
   template<size_t N> void set_supported_custom_presets(const char *const (&presets)[N]) {
     this->supported_custom_presets_.assign(presets, presets + N);
   }
-  const std::vector<std::string> &get_supported_custom_presets() const { return this->supported_custom_presets_; }
+  const std::vector<const char *> &get_supported_custom_presets() const { return this->supported_custom_presets_; }
   bool supports_custom_preset(const std::string &custom_preset) const {
-    return vector_contains(this->supported_custom_presets_, custom_preset);
+    for (const char *preset : this->supported_custom_presets_) {
+      if (strcmp(preset, custom_preset.c_str()) == 0)
+        return true;
+    }
+    return false;
   }
 
   void set_supported_swing_modes(ClimateSwingModeMask modes) { this->supported_swing_modes_ = modes; }
@@ -239,8 +236,11 @@ class ClimateTraits {
   climate::ClimateFanModeMask supported_fan_modes_;
   climate::ClimateSwingModeMask supported_swing_modes_;
   climate::ClimatePresetMask supported_presets_;
-  std::vector<std::string> supported_custom_fan_modes_;
-  std::vector<std::string> supported_custom_presets_;
+  // Store const char* pointers to avoid std::string overhead
+  // Pointers must remain valid for traits lifetime (typically string literals in rodata,
+  // or pointers to strings with sufficient lifetime like member variables)
+  std::vector<const char *> supported_custom_fan_modes_;
+  std::vector<const char *> supported_custom_presets_;
 };
 
 }  // namespace climate
diff --git a/esphome/components/midea/ac_adapter.cpp b/esphome/components/midea/ac_adapter.cpp
index 2837713c35..dca4038f04 100644
--- a/esphome/components/midea/ac_adapter.cpp
+++ b/esphome/components/midea/ac_adapter.cpp
@@ -8,9 +8,9 @@ namespace midea {
 namespace ac {
 
 const char *const Constants::TAG = "midea";
-const std::string Constants::FREEZE_PROTECTION = "freeze protection";
-const std::string Constants::SILENT = "silent";
-const std::string Constants::TURBO = "turbo";
+const char *const Constants::FREEZE_PROTECTION = "freeze protection";
+const char *const Constants::SILENT = "silent";
+const char *const Constants::TURBO = "turbo";
 
 ClimateMode Converters::to_climate_mode(MideaMode mode) {
   switch (mode) {
@@ -108,7 +108,7 @@ bool Converters::is_custom_midea_fan_mode(MideaFanMode mode) {
   }
 }
 
-const std::string &Converters::to_custom_climate_fan_mode(MideaFanMode mode) {
+const char *Converters::to_custom_climate_fan_mode(MideaFanMode mode) {
   switch (mode) {
     case MideaFanMode::FAN_SILENT:
       return Constants::SILENT;
@@ -151,7 +151,7 @@ ClimatePreset Converters::to_climate_preset(MideaPreset preset) {
 
 bool Converters::is_custom_midea_preset(MideaPreset preset) { return preset == MideaPreset::PRESET_FREEZE_PROTECTION; }
 
-const std::string &Converters::to_custom_climate_preset(MideaPreset preset) { return Constants::FREEZE_PROTECTION; }
+const char *Converters::to_custom_climate_preset(MideaPreset preset) { return Constants::FREEZE_PROTECTION; }
 
 MideaPreset Converters::to_midea_preset(const std::string &preset) { return MideaPreset::PRESET_FREEZE_PROTECTION; }
 
@@ -169,7 +169,7 @@ void Converters::to_climate_traits(ClimateTraits &traits, const dudanov::midea::
   if (capabilities.supportEcoPreset())
     traits.add_supported_preset(ClimatePreset::CLIMATE_PRESET_ECO);
   if (capabilities.supportFrostProtectionPreset())
-    traits.add_supported_custom_preset(Constants::FREEZE_PROTECTION);
+    traits.set_supported_custom_presets({Constants::FREEZE_PROTECTION});
 }
 
 }  // namespace ac
diff --git a/esphome/components/midea/ac_adapter.h b/esphome/components/midea/ac_adapter.h
index c17894ae31..d52f421331 100644
--- a/esphome/components/midea/ac_adapter.h
+++ b/esphome/components/midea/ac_adapter.h
@@ -20,9 +20,9 @@ using MideaPreset = dudanov::midea::ac::Preset;
 class Constants {
  public:
   static const char *const TAG;
-  static const std::string FREEZE_PROTECTION;
-  static const std::string SILENT;
-  static const std::string TURBO;
+  static const char *const FREEZE_PROTECTION;
+  static const char *const SILENT;
+  static const char *const TURBO;
 };
 
 class Converters {
@@ -35,12 +35,12 @@ class Converters {
   static MideaPreset to_midea_preset(const std::string &preset);
   static bool is_custom_midea_preset(MideaPreset preset);
   static ClimatePreset to_climate_preset(MideaPreset preset);
-  static const std::string &to_custom_climate_preset(MideaPreset preset);
+  static const char *to_custom_climate_preset(MideaPreset preset);
   static MideaFanMode to_midea_fan_mode(ClimateFanMode fan_mode);
   static MideaFanMode to_midea_fan_mode(const std::string &fan_mode);
   static bool is_custom_midea_fan_mode(MideaFanMode fan_mode);
   static ClimateFanMode to_climate_fan_mode(MideaFanMode fan_mode);
-  static const std::string &to_custom_climate_fan_mode(MideaFanMode fan_mode);
+  static const char *to_custom_climate_fan_mode(MideaFanMode fan_mode);
   static void to_climate_traits(ClimateTraits &traits, const dudanov::midea::ac::Capabilities &capabilities);
 };
 
diff --git a/esphome/components/midea/air_conditioner.cpp b/esphome/components/midea/air_conditioner.cpp
index 0ad26ebd51..97eacb936c 100644
--- a/esphome/components/midea/air_conditioner.cpp
+++ b/esphome/components/midea/air_conditioner.cpp
@@ -84,8 +84,10 @@ ClimateTraits AirConditioner::traits() {
   traits.set_supported_modes(this->supported_modes_);
   traits.set_supported_swing_modes(this->supported_swing_modes_);
   traits.set_supported_presets(this->supported_presets_);
-  traits.set_supported_custom_presets(this->supported_custom_presets_);
-  traits.set_supported_custom_fan_modes(this->supported_custom_fan_modes_);
+  if (!this->supported_custom_presets_.empty())
+    traits.set_supported_custom_presets(this->supported_custom_presets_);
+  if (!this->supported_custom_fan_modes_.empty())
+    traits.set_supported_custom_fan_modes(this->supported_custom_fan_modes_);
   /* + MINIMAL SET OF CAPABILITIES */
   traits.add_supported_fan_mode(ClimateFanMode::CLIMATE_FAN_AUTO);
   traits.add_supported_fan_mode(ClimateFanMode::CLIMATE_FAN_LOW);
diff --git a/esphome/components/midea/air_conditioner.h b/esphome/components/midea/air_conditioner.h
index 6c2401efe7..70833b8bcc 100644
--- a/esphome/components/midea/air_conditioner.h
+++ b/esphome/components/midea/air_conditioner.h
@@ -46,8 +46,8 @@ class AirConditioner : public ApplianceBase<dudanov::midea::ac::AirConditioner>,
   void set_supported_modes(ClimateModeMask modes) { this->supported_modes_ = modes; }
   void set_supported_swing_modes(ClimateSwingModeMask modes) { this->supported_swing_modes_ = modes; }
   void set_supported_presets(ClimatePresetMask presets) { this->supported_presets_ = presets; }
-  void set_custom_presets(const std::vector<std::string> &presets) { this->supported_custom_presets_ = presets; }
-  void set_custom_fan_modes(const std::vector<std::string> &modes) { this->supported_custom_fan_modes_ = modes; }
+  void set_custom_presets(std::initializer_list<const char *> presets) { this->supported_custom_presets_ = presets; }
+  void set_custom_fan_modes(std::initializer_list<const char *> modes) { this->supported_custom_fan_modes_ = modes; }
 
  protected:
   void control(const ClimateCall &call) override;
@@ -55,8 +55,8 @@ class AirConditioner : public ApplianceBase<dudanov::midea::ac::AirConditioner>,
   ClimateModeMask supported_modes_{};
   ClimateSwingModeMask supported_swing_modes_{};
   ClimatePresetMask supported_presets_{};
-  std::vector<std::string> supported_custom_presets_{};
-  std::vector<std::string> supported_custom_fan_modes_{};
+  std::vector<const char *> supported_custom_presets_{};
+  std::vector<const char *> supported_custom_fan_modes_{};
   Sensor *outdoor_sensor_{nullptr};
   Sensor *humidity_sensor_{nullptr};
   Sensor *power_sensor_{nullptr};
diff --git a/esphome/components/thermostat/thermostat_climate.cpp b/esphome/components/thermostat/thermostat_climate.cpp
index 18efe3984e..6842bd4be8 100644
--- a/esphome/components/thermostat/thermostat_climate.cpp
+++ b/esphome/components/thermostat/thermostat_climate.cpp
@@ -321,9 +321,17 @@ climate::ClimateTraits ThermostatClimate::traits() {
   for (auto &it : this->preset_config_) {
     traits.add_supported_preset(it.first);
   }
-  for (auto &it : this->custom_preset_config_) {
-    traits.add_supported_custom_preset(it.first);
+
+  // Extract custom preset names from the custom_preset_config_ map
+  if (!this->custom_preset_config_.empty()) {
+    std::vector<const char *> custom_preset_names;
+    custom_preset_names.reserve(this->custom_preset_config_.size());
+    for (const auto &it : this->custom_preset_config_) {
+      custom_preset_names.push_back(it.first.c_str());
+    }
+    traits.set_supported_custom_presets(custom_preset_names);
   }
+
   return traits;
 }
 
diff --git a/script/api_protobuf/api_protobuf.py b/script/api_protobuf/api_protobuf.py
index 394e92b9a7..3b756095a1 100755
--- a/script/api_protobuf/api_protobuf.py
+++ b/script/api_protobuf/api_protobuf.py
@@ -1610,8 +1610,9 @@ class RepeatedTypeInfo(TypeInfo):
             # Other types need the actual value
             # Special handling for const char* elements
             if self._use_pointer and "const char" in self._container_no_template:
+                field_id_size = self.calculate_field_id_size()
                 o += f"  for (const char *it : {container_ref}) {{\n"
-                o += "    size.add_length_force(1, strlen(it));\n"
+                o += f"    size.add_length_force({field_id_size}, strlen(it));\n"
             else:
                 auto_ref = "" if self._ti_is_bool else "&"
                 o += f"  for (const auto {auto_ref}it : {container_ref}) {{\n"
diff --git a/tests/integration/fixtures/climate_custom_fan_modes_and_presets.yaml b/tests/integration/fixtures/climate_custom_fan_modes_and_presets.yaml
new file mode 100644
index 0000000000..bf4ef9eafd
--- /dev/null
+++ b/tests/integration/fixtures/climate_custom_fan_modes_and_presets.yaml
@@ -0,0 +1,40 @@
+esphome:
+  name: climate-custom-modes-test
+host:
+api:
+logger:
+
+sensor:
+  - platform: template
+    id: thermostat_sensor
+    lambda: "return 22.0;"
+
+climate:
+  - platform: thermostat
+    id: test_thermostat
+    name: Test Thermostat Custom Modes
+    sensor: thermostat_sensor
+    preset:
+      - name: Away
+        default_target_temperature_low: 16°C
+        default_target_temperature_high: 20°C
+      - name: Eco Plus
+        default_target_temperature_low: 18°C
+        default_target_temperature_high: 22°C
+      - name: Super Saver
+        default_target_temperature_low: 20°C
+        default_target_temperature_high: 24°C
+      - name: Vacation Mode
+        default_target_temperature_low: 15°C
+        default_target_temperature_high: 18°C
+    idle_action:
+      - logger.log: idle_action
+    cool_action:
+      - logger.log: cool_action
+    heat_action:
+      - logger.log: heat_action
+    min_cooling_off_time: 10s
+    min_cooling_run_time: 10s
+    min_heating_off_time: 10s
+    min_heating_run_time: 10s
+    min_idle_time: 10s
diff --git a/tests/integration/test_climate_custom_modes.py b/tests/integration/test_climate_custom_modes.py
new file mode 100644
index 0000000000..ce34959d88
--- /dev/null
+++ b/tests/integration/test_climate_custom_modes.py
@@ -0,0 +1,42 @@
+"""Integration test for climate custom presets."""
+
+from __future__ import annotations
+
+from aioesphomeapi import ClimateInfo, ClimatePreset
+import pytest
+
+from .types import APIClientConnectedFactory, RunCompiledFunction
+
+
+@pytest.mark.asyncio
+async def test_climate_custom_fan_modes_and_presets(
+    yaml_config: str,
+    run_compiled: RunCompiledFunction,
+    api_client_connected: APIClientConnectedFactory,
+) -> None:
+    """Test that custom presets are properly exposed via API."""
+    async with run_compiled(yaml_config), api_client_connected() as client:
+        # Get entities and services
+        entities, services = await client.list_entities_services()
+        climate_infos = [e for e in entities if isinstance(e, ClimateInfo)]
+        assert len(climate_infos) == 1, "Expected exactly 1 climate entity"
+
+        test_climate = climate_infos[0]
+
+        # Verify enum presets are exposed (from preset: config map)
+        assert ClimatePreset.AWAY in test_climate.supported_presets, (
+            "Expected AWAY in enum presets"
+        )
+
+        # Verify custom string presets are exposed (non-standard preset names from preset map)
+        custom_presets = test_climate.supported_custom_presets
+        assert len(custom_presets) == 3, (
+            f"Expected 3 custom presets, got {len(custom_presets)}: {custom_presets}"
+        )
+        assert "Eco Plus" in custom_presets, "Expected 'Eco Plus' in custom presets"
+        assert "Super Saver" in custom_presets, (
+            "Expected 'Super Saver' in custom presets"
+        )
+        assert "Vacation Mode" in custom_presets, (
+            "Expected 'Vacation Mode' in custom presets"
+        )