diff --git a/esphome/components/api/api.proto b/esphome/components/api/api.proto
index a03bf5fc1a9..933d22f089a 100644
--- a/esphome/components/api/api.proto
+++ b/esphome/components/api/api.proto
@@ -1207,9 +1207,9 @@ 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_no_template) = "std::vector<const char *>"];
+  repeated string supported_custom_fan_modes = 15 [(container_pointer_no_template) = "std::span<const char *const>"];
   repeated ClimatePreset supported_presets = 16 [(container_pointer_no_template) = "climate::ClimatePresetMask"];
-  repeated string supported_custom_presets = 17 [(container_pointer_no_template) = "std::vector<const char *>"];
+  repeated string supported_custom_presets = 17 [(container_pointer_no_template) = "std::span<const char *const>"];
   bool disabled_by_default = 18;
   string icon = 19 [(field_ifdef) = "USE_ENTITY_ICON", (max_data_length) = 63];
   EntityCategory entity_category = 20;
diff --git a/esphome/components/api/api_connection.cpp b/esphome/components/api/api_connection.cpp
index e50bf2f722a..5885303a86a 100644
--- a/esphome/components/api/api_connection.cpp
+++ b/esphome/components/api/api_connection.cpp
@@ -806,9 +806,13 @@ uint16_t APIConnection::try_send_climate_info(EntityBase *entity, APIConnection
   msg.visual_min_humidity = traits.get_visual_min_humidity();
   msg.visual_max_humidity = traits.get_visual_max_humidity();
   msg.supported_fan_modes = &traits.get_supported_fan_modes();
-  msg.supported_custom_fan_modes = &traits.get_supported_custom_fan_modes();
+  const auto &fan_modes = traits.get_supported_custom_fan_modes();
+  const std::span<const char *const> custom_fan_modes(fan_modes.data(), fan_modes.size());
+  msg.supported_custom_fan_modes = &custom_fan_modes;
   msg.supported_presets = &traits.get_supported_presets();
-  msg.supported_custom_presets = &traits.get_supported_custom_presets();
+  const auto &presets = traits.get_supported_custom_presets();
+  const std::span<const char *const> custom_presets(presets.data(), presets.size());
+  msg.supported_custom_presets = &custom_presets;
   msg.supported_swing_modes = &traits.get_supported_swing_modes();
   return fill_and_encode_entity_info(climate, msg, conn, remaining_size);
 }
diff --git a/esphome/components/api/api_pb2.h b/esphome/components/api/api_pb2.h
index b4e3d4c55b4..350e962e84a 100644
--- a/esphome/components/api/api_pb2.h
+++ b/esphome/components/api/api_pb2.h
@@ -1666,9 +1666,9 @@ class ListEntitiesClimateResponse final : public InfoResponseProtoMessage {
   bool supports_action{false};
   const climate::ClimateFanModeMask *supported_fan_modes{};
   const climate::ClimateSwingModeMask *supported_swing_modes{};
-  const std::vector<const char *> *supported_custom_fan_modes{};
+  const std::span<const char *const> *supported_custom_fan_modes{};
   const climate::ClimatePresetMask *supported_presets{};
-  const std::vector<const char *> *supported_custom_presets{};
+  const std::span<const char *const> *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 196d4785e98..62e82f3146b 100644
--- a/esphome/components/bedjet/climate/bedjet_climate.cpp
+++ b/esphome/components/bedjet/climate/bedjet_climate.cpp
@@ -61,7 +61,7 @@ void BedJetClimate::dump_config() {
 
 void BedJetClimate::setup() {
   // Set custom modes once during setup — stored on Climate base class, wired via get_traits()
-  this->set_supported_custom_fan_modes(BEDJET_FAN_STEP_NAMES);
+  this->set_supported_custom_fan_modes_static(BEDJET_FAN_STEP_NAMES, BEDJET_FAN_SPEED_COUNT);
   this->set_supported_custom_presets({
       this->heating_mode_ == HEAT_MODE_EXTENDED ? "LTD HT" : "EXT HT",
       "M1",
diff --git a/esphome/components/climate/__init__.py b/esphome/components/climate/__init__.py
index e64092d30e5..b5ebb5eb3c6 100644
--- a/esphome/components/climate/__init__.py
+++ b/esphome/components/climate/__init__.py
@@ -458,6 +458,24 @@ async def setup_climate_core_(var: MockObj, config: ConfigType) -> None:
         await web_server.add_entity_config(var, web_server_config)
 
 
+def set_custom_fan_modes(var: MockObj, modes: list[str]) -> None:
+    """Point the climate at a shared flash table of custom fan modes."""
+    if modes:
+        table = cg.shared_progmem_array(
+            "climate_custom_fan_modes", cg.const_char_ptr, modes
+        )
+        cg.add(var.set_supported_custom_fan_modes_static(table, len(modes)))
+
+
+def set_custom_presets(var: MockObj, presets: list[str]) -> None:
+    """Point the climate at a shared flash table of custom presets."""
+    if presets:
+        table = cg.shared_progmem_array(
+            "climate_custom_presets", cg.const_char_ptr, presets
+        )
+        cg.add(var.set_supported_custom_presets_static(table, len(presets)))
+
+
 async def register_climate(var: MockObj, config: ConfigType) -> None:
     if not CORE.has_id(config[CONF_ID]):
         var = cg.Pvariable(config[CONF_ID], var)
diff --git a/esphome/components/climate/climate.cpp b/esphome/components/climate/climate.cpp
index d08952115bd..ed749b4a6d4 100644
--- a/esphome/components/climate/climate.cpp
+++ b/esphome/components/climate/climate.cpp
@@ -479,10 +479,8 @@ void Climate::publish_state() {
 ClimateTraits Climate::get_traits() {
   auto traits = this->traits();
   // Wire custom mode pointers from Climate-owned storage
-  if (this->supported_custom_fan_modes_)
-    traits.set_supported_custom_fan_modes_(this->supported_custom_fan_modes_);
-  if (this->supported_custom_presets_)
-    traits.set_supported_custom_presets_(this->supported_custom_presets_);
+  traits.set_supported_custom_fan_modes_(&this->supported_custom_fan_modes_);
+  traits.set_supported_custom_presets_(&this->supported_custom_presets_);
 #ifdef USE_CLIMATE_VISUAL_OVERRIDES
   if (!std::isnan(this->visual_min_temperature_override_)) {
     traits.set_visual_min_temperature(this->visual_min_temperature_override_);
@@ -628,7 +626,7 @@ template<typename T> bool set_primary_mode(optional<T> &primary, const char *&cu
  *   After:  fan_mode=nullopt,          custom_fan_mode_="Turbo" (pointer from traits)
  *
  * Lifetime Safety:
- *   - found_ptr must come from traits.find_custom_*_mode_()
+ *   - found_ptr must come from Climate::find_custom_*_()
  *   - Only pointers found in traits are stored, ensuring they remain valid
  *   - Prevents dangling pointers from temporary strings
  *
@@ -684,11 +682,7 @@ const char *Climate::find_custom_fan_mode_(const char *custom_fan_mode) {
 }
 
 const char *Climate::find_custom_fan_mode_(const char *custom_fan_mode, size_t len) {
-  if (this->supported_custom_fan_modes_) {
-    return vector_find(*this->supported_custom_fan_modes_, custom_fan_mode, len);
-  }
-  // Fallback for deprecated path: external components may set modes on ClimateTraits directly
-  return this->get_traits().find_custom_fan_mode_(custom_fan_mode, len);
+  return vector_find(this->supported_custom_fan_modes_, custom_fan_mode, len);
 }
 
 const char *Climate::find_custom_preset_(const char *custom_preset) {
@@ -696,11 +690,7 @@ const char *Climate::find_custom_preset_(const char *custom_preset) {
 }
 
 const char *Climate::find_custom_preset_(const char *custom_preset, size_t len) {
-  if (this->supported_custom_presets_) {
-    return vector_find(*this->supported_custom_presets_, custom_preset, len);
-  }
-  // Fallback for deprecated path: external components may set modes on ClimateTraits directly
-  return this->get_traits().find_custom_preset_(custom_preset, len);
+  return vector_find(this->supported_custom_presets_, custom_preset, len);
 }
 
 void Climate::dump_traits_(const char *tag) {
diff --git a/esphome/components/climate/climate.h b/esphome/components/climate/climate.h
index a9068972356..53cd6acad9b 100644
--- a/esphome/components/climate/climate.h
+++ b/esphome/components/climate/climate.h
@@ -246,26 +246,34 @@ class Climate : public EntityBase {
   }
 #endif
 
-  /// Set the supported custom fan modes (stored on Climate, referenced by ClimateTraits).
+  /// Set the supported custom fan modes; the list is copied (stored on Climate, referenced by ClimateTraits).
   void set_supported_custom_fan_modes(std::initializer_list<const char *> modes) {
-    this->ensure_custom_fan_modes_().assign(modes.begin(), modes.end());
+    this->supported_custom_fan_modes_.assign_copy(modes.begin(), modes.size());
   }
   void set_supported_custom_fan_modes(const std::vector<const char *> &modes) {
-    this->ensure_custom_fan_modes_() = modes;
+    this->supported_custom_fan_modes_.assign_copy(modes.data(), modes.size());
   }
   template<size_t N> void set_supported_custom_fan_modes(const char *const (&modes)[N]) {
-    this->ensure_custom_fan_modes_().assign(modes, modes + N);
+    this->supported_custom_fan_modes_.assign_copy(modes, N);
+  }
+  /// Points at a static table that outlives the climate (codegen); call before any runtime copy.
+  void set_supported_custom_fan_modes_static(const char *const *modes, size_t count) {
+    this->supported_custom_fan_modes_.assign_static(modes, count);
   }
 
-  /// Set the supported custom presets (stored on Climate, referenced by ClimateTraits).
+  /// Set the supported custom presets; the list is copied (stored on Climate, referenced by ClimateTraits).
   void set_supported_custom_presets(std::initializer_list<const char *> presets) {
-    this->ensure_custom_presets_().assign(presets.begin(), presets.end());
+    this->supported_custom_presets_.assign_copy(presets.begin(), presets.size());
   }
   void set_supported_custom_presets(const std::vector<const char *> &presets) {
-    this->ensure_custom_presets_() = presets;
+    this->supported_custom_presets_.assign_copy(presets.data(), presets.size());
   }
   template<size_t N> void set_supported_custom_presets(const char *const (&presets)[N]) {
-    this->ensure_custom_presets_().assign(presets, presets + N);
+    this->supported_custom_presets_.assign_copy(presets, N);
+  }
+  /// Points at a static table that outlives the climate (codegen); call before any runtime copy.
+  void set_supported_custom_presets_static(const char *const *presets, size_t count) {
+    this->supported_custom_presets_.assign_static(presets, count);
   }
 
   /// Check if a custom fan mode is currently active.
@@ -388,22 +396,8 @@ class Climate : public EntityBase {
 #endif
 
  private:
-  /// Lazy-allocate custom mode vectors (never freed — entity lives forever).
-  std::vector<const char *> &ensure_custom_fan_modes_() {
-    if (!this->supported_custom_fan_modes_) {
-      this->supported_custom_fan_modes_ = new std::vector<const char *>();  // NOLINT
-    }
-    return *this->supported_custom_fan_modes_;
-  }
-  std::vector<const char *> &ensure_custom_presets_() {
-    if (!this->supported_custom_presets_) {
-      this->supported_custom_presets_ = new std::vector<const char *>();  // NOLINT
-    }
-    return *this->supported_custom_presets_;
-  }
-
-  std::vector<const char *> *supported_custom_fan_modes_{nullptr};
-  std::vector<const char *> *supported_custom_presets_{nullptr};
+  ClimateCustomModes supported_custom_fan_modes_;
+  ClimateCustomModes supported_custom_presets_;
 
   /** The active custom fan mode (private - enforces use of safe setters).
    *
diff --git a/esphome/components/climate/climate_traits.cpp b/esphome/components/climate/climate_traits.cpp
index 398e25f69e3..2bf0afbb7b6 100644
--- a/esphome/components/climate/climate_traits.cpp
+++ b/esphome/components/climate/climate_traits.cpp
@@ -2,31 +2,14 @@
 
 namespace esphome::climate {
 
-// Compat: shared empty vector for getters when no custom modes are set.
-// Remove in 2026.11.0 when deprecated ClimateTraits setters are removed
-// and getters can return const vector * instead of const vector &.
-static const std::vector<const char *> EMPTY_CUSTOM_MODES;  // NOLINT
+static const ClimateCustomModes EMPTY_CUSTOM_MODES;  // NOLINT
 
-const std::vector<const char *> &ClimateTraits::get_supported_custom_fan_modes() const {
-  if (this->supported_custom_fan_modes_) {
-    return *this->supported_custom_fan_modes_;
-  }
-  // Compat: fall back to owned vector from deprecated setters. Remove in 2026.11.0.
-  if (!this->compat_custom_fan_modes_.empty()) {
-    return this->compat_custom_fan_modes_;
-  }
-  return EMPTY_CUSTOM_MODES;
+const ClimateCustomModes &ClimateTraits::get_supported_custom_fan_modes() const {
+  return this->supported_custom_fan_modes_ != nullptr ? *this->supported_custom_fan_modes_ : EMPTY_CUSTOM_MODES;
 }
 
-const std::vector<const char *> &ClimateTraits::get_supported_custom_presets() const {
-  if (this->supported_custom_presets_) {
-    return *this->supported_custom_presets_;
-  }
-  // Compat: fall back to owned vector from deprecated setters. Remove in 2026.11.0.
-  if (!this->compat_custom_presets_.empty()) {
-    return this->compat_custom_presets_;
-  }
-  return EMPTY_CUSTOM_MODES;
+const ClimateCustomModes &ClimateTraits::get_supported_custom_presets() const {
+  return this->supported_custom_presets_ != nullptr ? *this->supported_custom_presets_ : EMPTY_CUSTOM_MODES;
 }
 
 int8_t ClimateTraits::get_target_temperature_accuracy_decimals() const {
diff --git a/esphome/components/climate/climate_traits.h b/esphome/components/climate/climate_traits.h
index 6c776e0228f..37b1e7bc224 100644
--- a/esphome/components/climate/climate_traits.h
+++ b/esphome/components/climate/climate_traits.h
@@ -1,7 +1,7 @@
 #pragma once
 
 #include <cstring>
-#include <vector>
+#include <type_traits>
 #include "climate_mode.h"
 #include "esphome/core/finite_set_mask.h"
 #include "esphome/core/helpers.h"
@@ -18,9 +18,12 @@ 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) of const char* pointers
+/// Custom fan modes and custom presets: a flash table from codegen, or an owned copy set at runtime.
+using ClimateCustomModes = ConstVector<const char *, true>;
+
+// Lightweight linear search for small lists (1-20 items) of const char* pointers
 // Avoids std::find template overhead
-inline bool vector_contains(const std::vector<const char *> &vec, const char *value, size_t len) {
+template<typename List> inline bool vector_contains(const List &vec, const char *value, size_t len) {
   for (const char *item : vec) {
     if (strncmp(item, value, len) == 0 && item[len] == '\0')
       return true;
@@ -28,12 +31,12 @@ inline bool vector_contains(const std::vector<const char *> &vec, const char *va
   return false;
 }
 
-inline bool vector_contains(const std::vector<const char *> &vec, const char *value) {
+template<typename List> inline bool vector_contains(const List &vec, const char *value) {
   return vector_contains(vec, value, strlen(value));
 }
 
-// Find and return matching pointer from vector, or nullptr if not found
-inline const char *vector_find(const std::vector<const char *> &vec, const char *value, size_t len) {
+// Find and return matching pointer from a list, or nullptr if not found
+template<typename List> inline const char *vector_find(const List &vec, const char *value, size_t len) {
   for (const char *item : vec) {
     if (strncmp(item, value, len) == 0 && item[len] == '\0')
       return item;
@@ -71,7 +74,7 @@ inline const char *vector_find(const std::vector<const char *> &vec, const char
 class Climate;  // Forward declaration
 
 class ClimateTraits {
-  friend class Climate;  // Allow Climate to access protected find methods
+  friend class Climate;  // Climate wires its custom mode lists into traits
 
  public:
   /// Get/set feature flags (see ClimateFeatures enum in climate_mode.h)
@@ -93,42 +96,14 @@ class ClimateTraits {
     if (!this->supported_fan_modes_.empty()) {
       return true;
     }
-    // Same precedence as get_supported_custom_fan_modes() getter
-    if (this->supported_custom_fan_modes_) {
-      return !this->supported_custom_fan_modes_->empty();
-    }
-    return !this->compat_custom_fan_modes_.empty();  // Compat: remove in 2026.11.0
+    return this->supported_custom_fan_modes_ != nullptr && !this->supported_custom_fan_modes_->empty();
   }
   const ClimateFanModeMask &get_supported_fan_modes() const { return this->supported_fan_modes_; }
 
-  // Remove before 2026.11.0
-  ESPDEPRECATED("Call set_supported_custom_fan_modes() on the Climate entity instead. Removed in 2026.11.0", "2026.5.0")
-  void set_supported_custom_fan_modes(std::initializer_list<const char *> modes) {
-    // Compat: store in owned vector. Copies copy the vector (deprecated path still copies this vector).
-    this->compat_custom_fan_modes_ = modes;
-  }
-  // Remove before 2026.11.0
-  ESPDEPRECATED("Call set_supported_custom_fan_modes() on the Climate entity instead. Removed in 2026.11.0", "2026.5.0")
-  void set_supported_custom_fan_modes(const std::vector<const char *> &modes) {
-    this->compat_custom_fan_modes_ = modes;
-  }
-  // Remove before 2026.11.0
-  template<size_t N>
-  ESPDEPRECATED("Call set_supported_custom_fan_modes() on the Climate entity instead. Removed in 2026.11.0", "2026.5.0")
-  void set_supported_custom_fan_modes(const char *const (&modes)[N]) {
-    this->compat_custom_fan_modes_.assign(modes, modes + N);
-  }
-
-  // Deleted overloads to catch incorrect std::string usage at compile time with clear error messages
-  void set_supported_custom_fan_modes(const std::vector<std::string> &modes) = delete;
-  void set_supported_custom_fan_modes(std::initializer_list<std::string> modes) = delete;
-
-  // Compat: returns const ref with empty fallback. In 2026.11.0 change to return const vector *.
-  const std::vector<const char *> &get_supported_custom_fan_modes() const;
+  /// Empty when the climate has no custom fan modes. Set them on the Climate entity.
+  const ClimateCustomModes &get_supported_custom_fan_modes() const;
   bool supports_custom_fan_mode(const char *custom_fan_mode) const {
-    return (this->supported_custom_fan_modes_ &&
-            vector_contains(*this->supported_custom_fan_modes_, custom_fan_mode)) ||
-           vector_contains(this->compat_custom_fan_modes_, custom_fan_mode);  // Compat: remove in 2026.11.0
+    return vector_contains(this->get_supported_custom_fan_modes(), custom_fan_mode);
   }
   bool supports_custom_fan_mode(const std::string &custom_fan_mode) const {
     return this->supports_custom_fan_mode(custom_fan_mode.c_str());
@@ -140,32 +115,10 @@ class ClimateTraits {
   bool get_supports_presets() const { return !this->supported_presets_.empty(); }
   const ClimatePresetMask &get_supported_presets() const { return this->supported_presets_; }
 
-  // Remove before 2026.11.0
-  ESPDEPRECATED("Call set_supported_custom_presets() on the Climate entity instead. Removed in 2026.11.0", "2026.5.0")
-  void set_supported_custom_presets(std::initializer_list<const char *> presets) {
-    this->compat_custom_presets_ = presets;
-  }
-  // Remove before 2026.11.0
-  ESPDEPRECATED("Call set_supported_custom_presets() on the Climate entity instead. Removed in 2026.11.0", "2026.5.0")
-  void set_supported_custom_presets(const std::vector<const char *> &presets) {
-    this->compat_custom_presets_ = presets;
-  }
-  // Remove before 2026.11.0
-  template<size_t N>
-  ESPDEPRECATED("Call set_supported_custom_presets() on the Climate entity instead. Removed in 2026.11.0", "2026.5.0")
-  void set_supported_custom_presets(const char *const (&presets)[N]) {
-    this->compat_custom_presets_.assign(presets, presets + N);
-  }
-
-  // Deleted overloads to catch incorrect std::string usage at compile time with clear error messages
-  void set_supported_custom_presets(const std::vector<std::string> &presets) = delete;
-  void set_supported_custom_presets(std::initializer_list<std::string> presets) = delete;
-
-  // Compat: returns const ref with empty fallback. In 2026.11.0 change to return const vector *.
-  const std::vector<const char *> &get_supported_custom_presets() const;
+  /// Empty when the climate has no custom presets. Set them on the Climate entity.
+  const ClimateCustomModes &get_supported_custom_presets() const;
   bool supports_custom_preset(const char *custom_preset) const {
-    return (this->supported_custom_presets_ && vector_contains(*this->supported_custom_presets_, custom_preset)) ||
-           vector_contains(this->compat_custom_presets_, custom_preset);  // Compat: remove in 2026.11.0
+    return vector_contains(this->get_supported_custom_presets(), custom_preset);
   }
   bool supports_custom_preset(const std::string &custom_preset) const {
     return this->supports_custom_preset(custom_preset.c_str());
@@ -232,38 +185,8 @@ class ClimateTraits {
   }
 
   /// Set custom mode pointers (only Climate::get_traits() should call these).
-  void set_supported_custom_fan_modes_(const std::vector<const char *> *modes) {
-    this->supported_custom_fan_modes_ = modes;
-  }
-  void set_supported_custom_presets_(const std::vector<const char *> *presets) {
-    this->supported_custom_presets_ = presets;
-  }
-
-  /// Find and return the matching custom fan mode pointer from supported modes, or nullptr if not found
-  /// This is protected as it's an implementation detail - use Climate::find_custom_fan_mode_() instead
-  const char *find_custom_fan_mode_(const char *custom_fan_mode) const {
-    return this->find_custom_fan_mode_(custom_fan_mode, strlen(custom_fan_mode));
-  }
-  const char *find_custom_fan_mode_(const char *custom_fan_mode, size_t len) const {
-    if (this->supported_custom_fan_modes_) {
-      return vector_find(*this->supported_custom_fan_modes_, custom_fan_mode, len);
-    }
-    // Compat: check owned vector from deprecated setters. Remove in 2026.11.0.
-    return vector_find(this->compat_custom_fan_modes_, custom_fan_mode, len);
-  }
-
-  /// Find and return the matching custom preset pointer from supported presets, or nullptr if not found
-  /// This is protected as it's an implementation detail - use Climate::find_custom_preset_() instead
-  const char *find_custom_preset_(const char *custom_preset) const {
-    return this->find_custom_preset_(custom_preset, strlen(custom_preset));
-  }
-  const char *find_custom_preset_(const char *custom_preset, size_t len) const {
-    if (this->supported_custom_presets_) {
-      return vector_find(*this->supported_custom_presets_, custom_preset, len);
-    }
-    // Compat: check owned vector from deprecated setters. Remove in 2026.11.0.
-    return vector_find(this->compat_custom_presets_, custom_preset, len);
-  }
+  void set_supported_custom_fan_modes_(const ClimateCustomModes *modes) { this->supported_custom_fan_modes_ = modes; }
+  void set_supported_custom_presets_(const ClimateCustomModes *presets) { this->supported_custom_presets_ = presets; }
 
   uint32_t feature_flags_{0};
   float visual_min_temperature_{10};
@@ -279,17 +202,10 @@ class ClimateTraits {
   climate::ClimatePresetMask supported_presets_;
   TemperatureUnit temperature_unit_{TemperatureUnit::CELSIUS};
 
-  /** Custom mode storage - pointers to vectors owned by the Climate base class.
-   *
-   * ClimateTraits does not own this data; Climate stores the vectors and
-   * get_traits() wires these pointers automatically.
-   */
-  const std::vector<const char *> *supported_custom_fan_modes_{nullptr};
-  const std::vector<const char *> *supported_custom_presets_{nullptr};
-  // Compat: owned storage for deprecated setters. Copies copy the vector (copies include this vector).
-  // Remove in 2026.11.0.
-  std::vector<const char *> compat_custom_fan_modes_;
-  std::vector<const char *> compat_custom_presets_;
+  /// Owned by the Climate entity; get_traits() wires these pointers.
+  const ClimateCustomModes *supported_custom_fan_modes_{nullptr};
+  const ClimateCustomModes *supported_custom_presets_{nullptr};
 };
+static_assert(std::is_trivially_copyable_v<ClimateTraits>, "ClimateTraits is copied on every traits() call");
 
 }  // namespace esphome::climate
diff --git a/esphome/components/midea/ac_adapter.cpp b/esphome/components/midea/ac_adapter.cpp
index 30771d25ca2..a034abed6e0 100644
--- a/esphome/components/midea/ac_adapter.cpp
+++ b/esphome/components/midea/ac_adapter.cpp
@@ -5,11 +5,6 @@
 
 namespace esphome::midea::ac {
 
-const char *const Constants::TAG = "midea";
-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) {
     case MideaMode::MODE_AUTO:
diff --git a/esphome/components/midea/ac_adapter.h b/esphome/components/midea/ac_adapter.h
index 4a888ee8ff2..747d8cbf695 100644
--- a/esphome/components/midea/ac_adapter.h
+++ b/esphome/components/midea/ac_adapter.h
@@ -17,10 +17,10 @@ using MideaPreset = dudanov::midea::ac::Preset;
 
 class Constants {
  public:
-  static const char *const TAG;
-  static const char *const FREEZE_PROTECTION;
-  static const char *const SILENT;
-  static const char *const TURBO;
+  static constexpr const char *TAG = "midea";
+  static constexpr const char *FREEZE_PROTECTION = "Freeze Protection";
+  static constexpr const char *SILENT = "Silent";
+  static constexpr const char *TURBO = "Turbo";
 };
 
 class Converters {
diff --git a/esphome/components/midea/air_conditioner.h b/esphome/components/midea/air_conditioner.h
index 9977d2088ff..d227f22a3dd 100644
--- a/esphome/components/midea/air_conditioner.h
+++ b/esphome/components/midea/air_conditioner.h
@@ -44,8 +44,6 @@ class AirConditioner final : public ApplianceBase<dudanov::midea::ac::AirConditi
   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(std::initializer_list<const char *> presets) { this->set_supported_custom_presets(presets); }
-  void set_custom_fan_modes(std::initializer_list<const char *> modes) { this->set_supported_custom_fan_modes(modes); }
 
  protected:
   void control(const ClimateCall &call) override;
diff --git a/esphome/components/midea/climate.py b/esphome/components/midea/climate.py
index da952ab87b0..079b3e77065 100644
--- a/esphome/components/midea/climate.py
+++ b/esphome/components/midea/climate.py
@@ -210,10 +210,8 @@ async def to_code(config):
         cg.add(var.set_supported_swing_modes(config[CONF_SUPPORTED_SWING_MODES]))
     if CONF_SUPPORTED_PRESETS in config:
         cg.add(var.set_supported_presets(config[CONF_SUPPORTED_PRESETS]))
-    if CONF_CUSTOM_PRESETS in config:
-        cg.add(var.set_custom_presets(config[CONF_CUSTOM_PRESETS]))
-    if CONF_CUSTOM_FAN_MODES in config:
-        cg.add(var.set_custom_fan_modes(config[CONF_CUSTOM_FAN_MODES]))
+    climate.set_custom_presets(var, config.get(CONF_CUSTOM_PRESETS, []))
+    climate.set_custom_fan_modes(var, config.get(CONF_CUSTOM_FAN_MODES, []))
     sensors = sensor.sub_sensors(config)
     await sensors(CONF_OUTDOOR_TEMPERATURE, var.set_outdoor_temperature_sensor)
     await sensors(CONF_POWER_USAGE, var.set_power_sensor)
diff --git a/esphome/components/template/climate/__init__.py b/esphome/components/template/climate/__init__.py
index 5f7627c5c38..cca772d8e52 100644
--- a/esphome/components/template/climate/__init__.py
+++ b/esphome/components/template/climate/__init__.py
@@ -324,12 +324,7 @@ async def to_code(config: ConfigType) -> None:
     for mode in config.get(CONF_SUPPORTED_FAN_MODES, []):
         cg.add(var.add_supported_fan_mode(mode))
 
-    if CONF_CUSTOM_FAN_MODES in config:
-        cg.add(
-            var.set_supported_custom_fan_modes(
-                cg.ArrayInitializer(*config[CONF_CUSTOM_FAN_MODES])
-            )
-        )
+    climate.set_custom_fan_modes(var, config.get(CONF_CUSTOM_FAN_MODES, []))
 
     for mode in config.get(CONF_SUPPORTED_SWING_MODES, []):
         cg.add(var.add_supported_swing_mode(mode))
@@ -337,12 +332,7 @@ async def to_code(config: ConfigType) -> None:
     for preset in config.get(CONF_SUPPORTED_PRESETS, []):
         cg.add(var.add_supported_preset(preset))
 
-    if CONF_CUSTOM_PRESETS in config:
-        cg.add(
-            var.set_supported_custom_presets(
-                cg.ArrayInitializer(*config[CONF_CUSTOM_PRESETS])
-            )
-        )
+    climate.set_custom_presets(var, config.get(CONF_CUSTOM_PRESETS, []))
 
     for key, trigger_getter, arg_type in SET_ACTIONS:
         if (conf := config.get(key)) is not None:
diff --git a/tests/component_tests/climate/__init__.py b/tests/component_tests/climate/__init__.py
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/tests/component_tests/climate/config/custom_modes.yaml b/tests/component_tests/climate/config/custom_modes.yaml
new file mode 100644
index 00000000000..ba92a8aea26
--- /dev/null
+++ b/tests/component_tests/climate/config/custom_modes.yaml
@@ -0,0 +1,33 @@
+esphome:
+  name: test
+
+esp8266:
+  board: esp01_1m
+
+sensor:
+  - platform: template
+    id: room_temp
+    lambda: return 21.0;
+
+climate:
+  - platform: template
+    id: climate_a
+    name: Climate A
+    optimistic: true
+    sensor: room_temp
+    supported_modes: ["OFF", HEAT]
+    custom_fan_modes: [turbo, silent]
+    custom_presets: [eco]
+  - platform: template
+    id: climate_b
+    name: Climate B
+    optimistic: true
+    sensor: room_temp
+    supported_modes: ["OFF", HEAT]
+    custom_fan_modes: [turbo, silent]
+  - platform: template
+    id: climate_c
+    name: Climate C
+    optimistic: true
+    sensor: room_temp
+    supported_modes: ["OFF", HEAT]
diff --git a/tests/component_tests/climate/test_custom_modes.py b/tests/component_tests/climate/test_custom_modes.py
new file mode 100644
index 00000000000..23a116dca6f
--- /dev/null
+++ b/tests/component_tests/climate/test_custom_modes.py
@@ -0,0 +1,27 @@
+"""Custom fan modes and presets from YAML live in shared flash tables."""
+
+from collections.abc import Callable
+from pathlib import Path
+import re
+
+
+def test_custom_modes_use_shared_tables(
+    generate_main: Callable[[str | Path], str],
+    component_config_path: Callable[[str], Path],
+) -> None:
+    main_cpp = generate_main(component_config_path("custom_modes.yaml"))
+
+    fan_tables = re.findall(
+        r"static constexpr const char \* (climate_custom_fan_modes\w*)\[\] PROGMEM",
+        main_cpp,
+    )
+    assert len(fan_tables) == 1  # Climate A and B share one table
+    assert (
+        main_cpp.count(f"set_supported_custom_fan_modes_static({fan_tables[0]}, 2);")
+        == 2
+    )
+    assert (
+        "climate_a->set_supported_custom_presets_static(climate_custom_presets, 1);"
+        in main_cpp
+    )
+    assert "climate_c->set_supported_custom" not in main_cpp
diff --git a/tests/components/climate/climate_test.cpp b/tests/components/climate/climate_test.cpp
index bda014b87a4..4a568a75ab7 100644
--- a/tests/components/climate/climate_test.cpp
+++ b/tests/components/climate/climate_test.cpp
@@ -1,4 +1,7 @@
 #include <gtest/gtest.h>
+
+#include <vector>
+
 #include "esphome/components/climate/climate.h"
 
 namespace esphome::climate::testing {
@@ -70,4 +73,35 @@ TEST(ClimateRestoreStateTest, KeepsRestoringTheOtherFieldsWhenTheModeIsDropped)
   EXPECT_EQ(climate.fan_mode, CLIMATE_FAN_HIGH);
 }
 
+static constexpr const char *const FAN_TABLE[] = {"Turbo", "Silent"};
+
+TEST(ClimateCustomModesTest, StaticTableIsViewedNotCopied) {
+  TestClimate climate;
+  climate.set_supported_custom_fan_modes_static(FAN_TABLE, 2);
+  auto traits = climate.get_traits();
+  ASSERT_EQ(traits.get_supported_custom_fan_modes().size(), 2u);
+  EXPECT_EQ(traits.get_supported_custom_fan_modes().data(), FAN_TABLE);
+  EXPECT_TRUE(traits.get_supports_fan_modes());
+  EXPECT_TRUE(traits.supports_custom_fan_mode("Silent"));
+  EXPECT_FALSE(traits.supports_custom_fan_mode("Quiet"));
+}
+
+TEST(ClimateCustomModesTest, RuntimeListsAreCopiedAndReplaced) {
+  TestClimate climate;
+  std::vector<const char *> presets{"Eco", "Sleep"};
+  climate.set_supported_custom_presets(presets);
+  presets[0] = "Changed";  // the climate keeps its own copy
+  EXPECT_STREQ(climate.get_traits().get_supported_custom_presets()[0], "Eco");
+  climate.set_supported_custom_presets({"Night"});  // frees the previous copy
+  ASSERT_EQ(climate.get_traits().get_supported_custom_presets().size(), 1u);
+  EXPECT_STREQ(climate.get_traits().get_supported_custom_presets()[0], "Night");
+}
+
+TEST(ClimateCustomModesTest, TraitsWithoutAClimateHaveEmptyLists) {
+  ClimateTraits traits;
+  EXPECT_TRUE(traits.get_supported_custom_fan_modes().empty());
+  EXPECT_TRUE(traits.get_supported_custom_presets().empty());
+  EXPECT_FALSE(traits.supports_custom_preset("Eco"));
+}
+
 }  // namespace esphome::climate::testing
diff --git a/tests/integration/fixtures/external_components/legacy_climate_component/__init__.py b/tests/integration/fixtures/external_components/legacy_climate_component/__init__.py
deleted file mode 100644
index ba9eff2d892..00000000000
--- a/tests/integration/fixtures/external_components/legacy_climate_component/__init__.py
+++ /dev/null
@@ -1,4 +0,0 @@
-"""Legacy climate component — tests deprecated ClimateTraits setters backward compat.
-
-Remove this entire directory in 2026.11.0 when the deprecated setters are removed.
-"""
diff --git a/tests/integration/fixtures/external_components/legacy_climate_component/climate/__init__.py b/tests/integration/fixtures/external_components/legacy_climate_component/climate/__init__.py
deleted file mode 100644
index 0810ae02a16..00000000000
--- a/tests/integration/fixtures/external_components/legacy_climate_component/climate/__init__.py
+++ /dev/null
@@ -1,16 +0,0 @@
-"""Legacy climate platform that uses deprecated ClimateTraits setters."""
-
-import esphome.codegen as cg
-from esphome.components import climate
-import esphome.config_validation as cv
-from esphome.types import ConfigType
-
-legacy_climate_ns = cg.esphome_ns.namespace("legacy_climate_test")
-LegacyClimate = legacy_climate_ns.class_("LegacyClimate", climate.Climate, cg.Component)
-
-CONFIG_SCHEMA = climate.climate_schema(LegacyClimate).extend(cv.COMPONENT_SCHEMA)
-
-
-async def to_code(config: ConfigType) -> None:
-    var = await climate.new_climate(config)
-    await cg.register_component(var, config)
diff --git a/tests/integration/fixtures/external_components/legacy_climate_component/climate/legacy_climate.h b/tests/integration/fixtures/external_components/legacy_climate_component/climate/legacy_climate.h
deleted file mode 100644
index bdf5179fa5b..00000000000
--- a/tests/integration/fixtures/external_components/legacy_climate_component/climate/legacy_climate.h
+++ /dev/null
@@ -1,55 +0,0 @@
-#pragma once
-
-#include "esphome/components/climate/climate.h"
-#include "esphome/core/component.h"
-
-namespace esphome::legacy_climate_test {
-
-/// Test climate that uses the DEPRECATED ClimateTraits setters for custom modes.
-/// This validates backward compatibility for external components that haven't migrated.
-class LegacyClimate : public climate::Climate, public Component {
- public:
-  void setup() override {
-    this->mode = climate::CLIMATE_MODE_OFF;
-    this->target_temperature = 22.0f;
-    this->current_temperature = 20.0f;
-    this->publish_state();
-  }
-
- protected:
-  climate::ClimateTraits traits() override {
-    auto traits = climate::ClimateTraits();
-    traits.add_feature_flags(climate::CLIMATE_SUPPORTS_CURRENT_TEMPERATURE);
-    traits.set_supported_modes({climate::CLIMATE_MODE_OFF, climate::CLIMATE_MODE_HEAT, climate::CLIMATE_MODE_COOL});
-    traits.set_visual_min_temperature(16.0f);
-    traits.set_visual_max_temperature(30.0f);
-    traits.set_visual_temperature_step(0.5f);
-
-    // DEPRECATED API: setting custom modes directly on ClimateTraits.
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
-    traits.set_supported_custom_fan_modes({"Turbo", "Silent", "Auto"});
-    traits.set_supported_custom_presets({"Eco Mode", "Night Mode"});
-#pragma GCC diagnostic pop
-
-    return traits;
-  }
-
-  void control(const climate::ClimateCall &call) override {
-    if (call.get_mode().has_value()) {
-      this->mode = *call.get_mode();
-    }
-    if (call.get_target_temperature().has_value()) {
-      this->target_temperature = *call.get_target_temperature();
-    }
-    if (call.has_custom_fan_mode()) {
-      this->set_custom_fan_mode_(call.get_custom_fan_mode());
-    }
-    if (call.has_custom_preset()) {
-      this->set_custom_preset_(call.get_custom_preset());
-    }
-    this->publish_state();
-  }
-};
-
-}  // namespace esphome::legacy_climate_test
diff --git a/tests/integration/fixtures/legacy_climate_compat.yaml b/tests/integration/fixtures/legacy_climate_compat.yaml
deleted file mode 100644
index 112e50a4685..00000000000
--- a/tests/integration/fixtures/legacy_climate_compat.yaml
+++ /dev/null
@@ -1,18 +0,0 @@
-esphome:
-  name: legacy-climate-compat
-
-host:
-api:
-logger:
-  level: DEBUG
-
-external_components:
-  - source:
-      type: local
-      path: EXTERNAL_COMPONENT_PATH
-    components: [legacy_climate_component]
-
-climate:
-  - platform: legacy_climate_component
-    name: "Legacy Climate"
-    id: legacy_climate
diff --git a/tests/integration/integration_test_durations.json b/tests/integration/integration_test_durations.json
index 060799862f7..cea269df243 100644
--- a/tests/integration/integration_test_durations.json
+++ b/tests/integration/integration_test_durations.json
@@ -61,7 +61,6 @@
   "tests/integration/test_improv_serial_uart.py": 15.6,
   "tests/integration/test_large_message_batching.py": 13.6,
   "tests/integration/test_legacy_area.py": 11.44,
-  "tests/integration/test_legacy_climate_compat.py": 12.99,
   "tests/integration/test_legacy_fan_compat.py": 8.75,
   "tests/integration/test_light_automations.py": 15.38,
   "tests/integration/test_light_binary_effect_off_phase.py": 23.85,
diff --git a/tests/integration/test_legacy_climate_compat.py b/tests/integration/test_legacy_climate_compat.py
deleted file mode 100644
index aad71dd04ae..00000000000
--- a/tests/integration/test_legacy_climate_compat.py
+++ /dev/null
@@ -1,96 +0,0 @@
-"""Integration test for backward compatibility of deprecated ClimateTraits setters.
-
-Verifies that external components using the old traits.set_supported_custom_fan_modes()
-and traits.set_supported_custom_presets() API still work correctly during the
-deprecation period.
-
-Remove this entire test file and the legacy_climate_component external component
-in 2026.11.0 when the deprecated ClimateTraits setters are removed.
-"""
-
-from __future__ import annotations
-
-import asyncio
-from pathlib import Path
-
-import aioesphomeapi
-from aioesphomeapi import ClimateInfo
-import pytest
-
-from .state_utils import InitialStateHelper
-from .types import APIClientConnectedFactory, RunCompiledFunction
-
-
-@pytest.mark.asyncio
-async def test_legacy_climate_compat(
-    yaml_config: str,
-    run_compiled: RunCompiledFunction,
-    api_client_connected: APIClientConnectedFactory,
-) -> None:
-    """Test that deprecated ClimateTraits custom mode setters still work end-to-end."""
-    external_components_path = str(
-        Path(__file__).parent / "fixtures" / "external_components"
-    )
-    yaml_config = yaml_config.replace(
-        "EXTERNAL_COMPONENT_PATH", external_components_path
-    )
-
-    loop = asyncio.get_running_loop()
-
-    async with run_compiled(yaml_config), api_client_connected() as client:
-        entities, _ = await client.list_entities_services()
-        initial_state_helper = InitialStateHelper(entities)
-
-        climate_infos = [e for e in entities if isinstance(e, ClimateInfo)]
-        assert len(climate_infos) == 1, (
-            f"Expected 1 climate entity, got {len(climate_infos)}"
-        )
-
-        test_climate = climate_infos[0]
-
-        # Verify custom fan modes set via deprecated ClimateTraits setter are exposed
-        assert set(test_climate.supported_custom_fan_modes) == {
-            "Turbo",
-            "Silent",
-            "Auto",
-        }, (
-            f"Expected custom fan modes {{Turbo, Silent, Auto}}, "
-            f"got {test_climate.supported_custom_fan_modes}"
-        )
-
-        # Verify custom presets set via deprecated ClimateTraits setter are exposed
-        assert set(test_climate.supported_custom_presets) == {
-            "Eco Mode",
-            "Night Mode",
-        }, (
-            f"Expected custom presets {{Eco Mode, Night Mode}}, "
-            f"got {test_climate.supported_custom_presets}"
-        )
-
-        # Set up state tracking with InitialStateHelper
-        turbo_future: asyncio.Future[aioesphomeapi.ClimateState] = loop.create_future()
-
-        def on_state(state: aioesphomeapi.EntityState) -> None:
-            if (
-                isinstance(state, aioesphomeapi.ClimateState)
-                and state.custom_fan_mode == "Turbo"
-                and not turbo_future.done()
-            ):
-                turbo_future.set_result(state)
-
-        client.subscribe_states(initial_state_helper.on_state_wrapper(on_state))
-
-        try:
-            await initial_state_helper.wait_for_initial_states()
-        except TimeoutError:
-            pytest.fail("Timeout waiting for initial states")
-
-        # Verify we can set a custom fan mode via API (tests find_custom_fan_mode_ compat path)
-        client.climate_command(test_climate.key, custom_fan_mode="Turbo")
-
-        try:
-            turbo_state = await asyncio.wait_for(turbo_future, timeout=5.0)
-        except TimeoutError:
-            pytest.fail("Custom fan mode 'Turbo' not received within 5 seconds")
-
-        assert turbo_state.custom_fan_mode == "Turbo"