Fix compat: use owned vector instead of leak, wire preset modes in subclasses

- Deprecated FanTraits setters store in an owned compat_preset_modes_
  vector (same copy cost as pre-PR). No heap leak, no dangling pointer.
- Subclass get_traits() calls wire_preset_modes_() to attach the
  Fan-owned pointer to the returned traits.
- Getter/find/supports all check compat vector as fallback.

esphome/components/fan/fan.cpp

@@ -15,8 +15,14 @@ static const char *const TAG = "fan";
 static const std::vector<const char *> EMPTY_PRESET_MODES;  // NOLINT
 
 const std::vector<const char *> &FanTraits::supported_preset_modes() const {
-  // Compat: return empty ref when pointer is null. Remove in 2026.11.0 (change return to const vector *).
-  return this->preset_modes_ ? *this->preset_modes_ : EMPTY_PRESET_MODES;
+  if (this->preset_modes_) {
+    return *this->preset_modes_;
+  }
+  // Compat: fall back to owned vector from deprecated setters. Remove in 2026.11.0 (change return to const vector *).
+  if (!this->compat_preset_modes_.empty()) {
+    return this->compat_preset_modes_;
+  }
+  return EMPTY_PRESET_MODES;
 }
 
 // Fan direction strings indexed by FanDirection enum (0-1): FORWARD, REVERSE, plus UNKNOWN

esphome/components/fan/fan.h

@@ -175,6 +175,13 @@ class Fan : public EntityBase {
   const char *find_preset_mode_(const char *preset_mode);
   const char *find_preset_mode_(const char *preset_mode, size_t len);
 
+  /// Wire the Fan-owned preset modes pointer into the given traits object.
+  void wire_preset_modes_(FanTraits &traits) {
+    if (this->supported_preset_modes_) {
+      traits.set_supported_preset_modes(this->supported_preset_modes_);
+    }
+  }
+
   LazyCallbackManager<void()> state_callback_{};
   ESPPreferenceObject rtc_;
   FanRestoreMode restore_mode_;

esphome/components/fan/fan_traits.h

@@ -39,31 +39,32 @@ class FanTraits {
   // Remove before 2026.11.0
   ESPDEPRECATED("Call set_supported_preset_modes() on the Fan entity instead. Removed in 2026.11.0", "2026.5.0")
   void set_supported_preset_modes(std::initializer_list<const char *> preset_modes) {
-    // NOLINT - intentional leak: pointer must survive copies of FanTraits
-    this->preset_modes_ = new std::vector<const char *>(preset_modes);  // NOLINT
+    // Compat: store in owned vector. Copies copy the vector (same cost as before this PR).
+    this->compat_preset_modes_ = preset_modes;
   }
   // Remove before 2026.11.0
   ESPDEPRECATED("Call set_supported_preset_modes() on the Fan entity instead. Removed in 2026.11.0", "2026.5.0")
   void set_supported_preset_modes(const std::vector<const char *> &preset_modes) {
-    this->preset_modes_ = new std::vector<const char *>(preset_modes);  // NOLINT
+    this->compat_preset_modes_ = preset_modes;
   }
 
   /// Return if preset modes are supported
-  bool supports_preset_modes() const { return this->preset_modes_ && !this->preset_modes_->empty(); }
+  bool supports_preset_modes() const {
+    return (this->preset_modes_ && !this->preset_modes_->empty()) || !this->compat_preset_modes_.empty();
+  }
   /// Find and return the matching preset mode pointer from supported modes, or nullptr if not found.
   const char *find_preset_mode(const char *preset_mode) const {
     return this->find_preset_mode(preset_mode, preset_mode ? strlen(preset_mode) : 0);
   }
   const char *find_preset_mode(const char *preset_mode, size_t len) const {
-    if (preset_mode == nullptr || len == 0)
-      return nullptr;
-    if (!this->preset_modes_) {
+    if (preset_mode == nullptr || len == 0) {
       return nullptr;
     }
-    const auto &modes = *this->preset_modes_;
+    // Check pointer-based storage (new path) then compat owned vector (deprecated path)
+    const auto &modes = this->preset_modes_ ? *this->preset_modes_ : this->compat_preset_modes_;
     for (const char *mode : modes) {
       if (strncmp(mode, preset_mode, len) == 0 && mode[len] == '\0') {
-        return mode;  // Return pointer from traits
+        return mode;
       }
     }
     return nullptr;
@@ -75,6 +76,9 @@ class FanTraits {
   bool direction_{false};
   int speed_count_{};
   const std::vector<const char *> *preset_modes_{nullptr};
+  // Compat: owned storage for deprecated setters. Copies copy the vector (same cost as pre-PR).
+  // Remove in 2026.11.0.
+  std::vector<const char *> compat_preset_modes_;
 };
 
 }  // namespace fan

esphome/components/hbridge/fan/hbridge_fan.h

@@ -24,7 +24,10 @@ class HBridgeFan : public Component, public fan::Fan {
 
   void setup() override;
   void dump_config() override;
-  fan::FanTraits get_traits() override { return this->traits_; }
+  fan::FanTraits get_traits() override {
+    this->wire_preset_modes_(this->traits_);
+    return this->traits_;
+  }
 
   fan::FanCall brake();
 

esphome/components/speed/fan/speed_fan.h

@@ -17,7 +17,10 @@ class SpeedFan : public Component, public fan::Fan {
   void set_oscillating(output::BinaryOutput *oscillating) { this->oscillating_ = oscillating; }
   void set_direction(output::BinaryOutput *direction) { this->direction_ = direction; }
   void set_preset_modes(std::initializer_list<const char *> presets) { this->set_supported_preset_modes(presets); }
-  fan::FanTraits get_traits() override { return this->traits_; }
+  fan::FanTraits get_traits() override {
+    this->wire_preset_modes_(this->traits_);
+    return this->traits_;
+  }
 
  protected:
   void control(const fan::FanCall &call) override;

esphome/components/template/fan/template_fan.h

@@ -14,7 +14,10 @@ class TemplateFan final : public Component, public fan::Fan {
   void set_has_oscillating(bool has_oscillating) { this->has_oscillating_ = has_oscillating; }
   void set_speed_count(int count) { this->speed_count_ = count; }
   void set_preset_modes(std::initializer_list<const char *> presets) { this->set_supported_preset_modes(presets); }
-  fan::FanTraits get_traits() override { return this->traits_; }
+  fan::FanTraits get_traits() override {
+    this->wire_preset_modes_(this->traits_);
+    return this->traits_;
+  }
 
  protected:
   void control(const fan::FanCall &call) override;