From ff0b1a24c77c0e2b1632258c4dc066524b752fa5 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Thu, 8 Jan 2026 21:35:18 -1000
Subject: [PATCH 01/10] [fan] Make get_preset_mode() return empty string
 instead of nullptr for safety

---
 esphome/components/copy/fan/copy_fan.cpp      | 18 +++++++++-------
 esphome/components/copy/fan/copy_fan.h        |  2 +-
 esphome/components/fan/automation.h           |  5 ++---
 esphome/components/fan/fan.cpp                | 21 ++++++++++++-------
 esphome/components/fan/fan.h                  |  6 ++++--
 .../components/hbridge/fan/hbridge_fan.cpp    |  2 +-
 esphome/components/speed/fan/speed_fan.cpp    |  2 +-
 .../components/template/fan/template_fan.cpp  |  2 +-
 8 files changed, 35 insertions(+), 23 deletions(-)

diff --git a/esphome/components/copy/fan/copy_fan.cpp b/esphome/components/copy/fan/copy_fan.cpp
index d35ece950b..b4a43cf2f1 100644
--- a/esphome/components/copy/fan/copy_fan.cpp
+++ b/esphome/components/copy/fan/copy_fan.cpp
@@ -8,20 +8,24 @@ static const char *const TAG = "copy.fan";
 
 void CopyFan::setup() {
   source_->add_on_state_callback([this]() {
-    this->state = source_->state;
-    this->oscillating = source_->oscillating;
-    this->speed = source_->speed;
-    this->direction = source_->direction;
-    this->set_preset_mode_(source_->get_preset_mode());
+    this->copy_state_from_source_();
     this->publish_state();
   });
 
+  this->copy_state_from_source_();
+  this->publish_state();
+}
+
+void CopyFan::copy_state_from_source_() {
   this->state = source_->state;
   this->oscillating = source_->oscillating;
   this->speed = source_->speed;
   this->direction = source_->direction;
-  this->set_preset_mode_(source_->get_preset_mode());
-  this->publish_state();
+  if (source_->has_preset_mode()) {
+    this->set_preset_mode_(source_->get_preset_mode());
+  } else {
+    this->clear_preset_mode_();
+  }
 }
 
 void CopyFan::dump_config() { LOG_FAN("", "Copy Fan", this); }
diff --git a/esphome/components/copy/fan/copy_fan.h b/esphome/components/copy/fan/copy_fan.h
index b474975bc4..988129f07b 100644
--- a/esphome/components/copy/fan/copy_fan.h
+++ b/esphome/components/copy/fan/copy_fan.h
@@ -16,7 +16,7 @@ class CopyFan : public fan::Fan, public Component {
 
  protected:
   void control(const fan::FanCall &call) override;
-  ;
+  void copy_state_from_source_();
 
   fan::Fan *source_;
 };
diff --git a/esphome/components/fan/automation.h b/esphome/components/fan/automation.h
index ce1db6fc64..d6becb66fd 100644
--- a/esphome/components/fan/automation.h
+++ b/esphome/components/fan/automation.h
@@ -216,15 +216,14 @@ class FanPresetSetTrigger : public Trigger<std::string> {
       auto should_trigger = preset_mode != this->last_preset_mode_;
       this->last_preset_mode_ = preset_mode;
       if (should_trigger) {
-        // Trigger with empty string when nullptr to maintain backward compatibility
-        this->trigger(preset_mode != nullptr ? preset_mode : "");
+        this->trigger(preset_mode);
       }
     });
     this->last_preset_mode_ = state->get_preset_mode();
   }
 
  protected:
-  const char *last_preset_mode_{nullptr};
+  const char *last_preset_mode_{""};
 };
 
 }  // namespace fan
diff --git a/esphome/components/fan/fan.cpp b/esphome/components/fan/fan.cpp
index 0ffb60e50d..b56ed72d9a 100644
--- a/esphome/components/fan/fan.cpp
+++ b/esphome/components/fan/fan.cpp
@@ -83,7 +83,7 @@ void FanCall::validate_() {
       *this->binary_state_
       // ..,and no preset mode will be active...
       && !this->has_preset_mode() &&
-      this->parent_.get_preset_mode() == nullptr
+      !this->parent_.has_preset_mode()
       // ...and neither current nor new speed is available...
       && traits.supports_speed() && this->parent_.speed == 0 && !this->speed_.has_value()) {
     // ...set speed to 100%
@@ -175,6 +175,15 @@ bool Fan::set_preset_mode_(const std::string &preset_mode) { return this->set_pr
 
 void Fan::clear_preset_mode_() { this->preset_mode_ = nullptr; }
 
+void Fan::apply_preset_mode_(const FanCall &call) {
+  if (call.has_preset_mode()) {
+    this->set_preset_mode_(call.get_preset_mode());
+  } else if (call.get_speed().has_value()) {
+    // Manually setting speed clears preset (per Home Assistant convention)
+    this->clear_preset_mode_();
+  }
+}
+
 void Fan::add_on_state_callback(std::function<void()> &&callback) { this->state_callback_.add(std::move(callback)); }
 void Fan::publish_state() {
   auto traits = this->get_traits();
@@ -192,9 +201,8 @@ void Fan::publish_state() {
   if (traits.supports_direction()) {
     ESP_LOGD(TAG, "  Direction: %s", LOG_STR_ARG(fan_direction_to_string(this->direction)));
   }
-  const char *preset = this->get_preset_mode();
-  if (preset != nullptr) {
-    ESP_LOGD(TAG, "  Preset Mode: %s", preset);
+  if (this->has_preset_mode()) {
+    ESP_LOGD(TAG, "  Preset Mode: %s", this->get_preset_mode());
   }
   this->state_callback_.call();
 #if defined(USE_FAN) && defined(USE_CONTROLLER_REGISTRY)
@@ -249,12 +257,11 @@ void Fan::save_state_() {
   state.speed = this->speed;
   state.direction = this->direction;
 
-  const char *preset = this->get_preset_mode();
-  if (preset != nullptr) {
+  if (this->has_preset_mode()) {
     const auto &preset_modes = traits.supported_preset_modes();
     // Find index of current preset mode (pointer comparison is safe since preset is from traits)
     for (size_t i = 0; i < preset_modes.size(); i++) {
-      if (preset_modes[i] == preset) {
+      if (preset_modes[i] == this->preset_mode_) {
         state.preset_mode = i;
         break;
       }
diff --git a/esphome/components/fan/fan.h b/esphome/components/fan/fan.h
index 7c79fda83e..17462c4108 100644
--- a/esphome/components/fan/fan.h
+++ b/esphome/components/fan/fan.h
@@ -128,8 +128,8 @@ class Fan : public EntityBase {
   /// Set the restore mode of this fan.
   void set_restore_mode(FanRestoreMode restore_mode) { this->restore_mode_ = restore_mode; }
 
-  /// Get the current preset mode (returns pointer to string stored in traits, or nullptr if not set)
-  const char *get_preset_mode() const { return this->preset_mode_; }
+  /// Get the current preset mode (returns pointer to string stored in traits, or empty string if not set)
+  const char *get_preset_mode() const { return this->preset_mode_ != nullptr ? this->preset_mode_ : ""; }
 
   /// Check if a preset mode is currently active
   bool has_preset_mode() const { return this->preset_mode_ != nullptr; }
@@ -151,6 +151,8 @@ class Fan : public EntityBase {
   bool set_preset_mode_(const std::string &preset_mode);
   /// Clear the preset mode
   void clear_preset_mode_();
+  /// Apply preset mode from a FanCall (handles speed-clears-preset convention)
+  void apply_preset_mode_(const FanCall &call);
   /// Find and return the matching preset mode pointer from traits, or nullptr if not found.
   const char *find_preset_mode_(const char *preset_mode);
   const char *find_preset_mode_(const char *preset_mode, size_t len);
diff --git a/esphome/components/hbridge/fan/hbridge_fan.cpp b/esphome/components/hbridge/fan/hbridge_fan.cpp
index 488208b725..9bf58f9d1e 100644
--- a/esphome/components/hbridge/fan/hbridge_fan.cpp
+++ b/esphome/components/hbridge/fan/hbridge_fan.cpp
@@ -57,7 +57,7 @@ void HBridgeFan::control(const fan::FanCall &call) {
     this->oscillating = *call.get_oscillating();
   if (call.get_direction().has_value())
     this->direction = *call.get_direction();
-  this->set_preset_mode_(call.get_preset_mode());
+  this->apply_preset_mode_(call);
 
   this->write_state_();
   this->publish_state();
diff --git a/esphome/components/speed/fan/speed_fan.cpp b/esphome/components/speed/fan/speed_fan.cpp
index 801593c2ac..af98e3a51f 100644
--- a/esphome/components/speed/fan/speed_fan.cpp
+++ b/esphome/components/speed/fan/speed_fan.cpp
@@ -29,7 +29,7 @@ void SpeedFan::control(const fan::FanCall &call) {
     this->oscillating = *call.get_oscillating();
   if (call.get_direction().has_value())
     this->direction = *call.get_direction();
-  this->set_preset_mode_(call.get_preset_mode());
+  this->apply_preset_mode_(call);
 
   this->write_state_();
   this->publish_state();
diff --git a/esphome/components/template/fan/template_fan.cpp b/esphome/components/template/fan/template_fan.cpp
index 384e6b0ca1..0e1920a984 100644
--- a/esphome/components/template/fan/template_fan.cpp
+++ b/esphome/components/template/fan/template_fan.cpp
@@ -28,7 +28,7 @@ void TemplateFan::control(const fan::FanCall &call) {
     this->oscillating = *call.get_oscillating();
   if (call.get_direction().has_value() && this->has_direction_)
     this->direction = *call.get_direction();
-  this->set_preset_mode_(call.get_preset_mode());
+  this->apply_preset_mode_(call);
 
   this->publish_state();
 }

From 04ffa7464363692e0139ec4ce446a11134344e0d Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Thu, 8 Jan 2026 21:44:40 -1000
Subject: [PATCH 02/10] if we are going ot break it, string view

---
 esphome/components/api/api_connection.cpp | 6 ++++--
 esphome/components/fan/automation.h       | 6 +++---
 esphome/components/fan/fan.cpp            | 6 +++---
 esphome/components/fan/fan.h              | 8 ++++++--
 4 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/esphome/components/api/api_connection.cpp b/esphome/components/api/api_connection.cpp
index fb3548d117..989536aca0 100644
--- a/esphome/components/api/api_connection.cpp
+++ b/esphome/components/api/api_connection.cpp
@@ -442,8 +442,10 @@ uint16_t APIConnection::try_send_fan_state(EntityBase *entity, APIConnection *co
   }
   if (traits.supports_direction())
     msg.direction = static_cast<enums::FanDirection>(fan->direction);
-  if (traits.supports_preset_modes() && fan->has_preset_mode())
-    msg.preset_mode = StringRef(fan->get_preset_mode());
+  if (traits.supports_preset_modes() && fan->has_preset_mode()) {
+    auto preset = fan->get_preset_mode();
+    msg.preset_mode = StringRef(preset.data(), preset.size());
+  }
   return fill_and_encode_entity_state(fan, msg, FanStateResponse::MESSAGE_TYPE, conn, remaining_size, is_single);
 }
 uint16_t APIConnection::try_send_fan_info(EntityBase *entity, APIConnection *conn, uint32_t remaining_size,
diff --git a/esphome/components/fan/automation.h b/esphome/components/fan/automation.h
index d6becb66fd..8175caefea 100644
--- a/esphome/components/fan/automation.h
+++ b/esphome/components/fan/automation.h
@@ -212,18 +212,18 @@ class FanPresetSetTrigger : public Trigger<std::string> {
  public:
   FanPresetSetTrigger(Fan *state) {
     state->add_on_state_callback([this, state]() {
-      const auto *preset_mode = state->get_preset_mode();
+      auto preset_mode = state->get_preset_mode();
       auto should_trigger = preset_mode != this->last_preset_mode_;
       this->last_preset_mode_ = preset_mode;
       if (should_trigger) {
-        this->trigger(preset_mode);
+        this->trigger(std::string(preset_mode));
       }
     });
     this->last_preset_mode_ = state->get_preset_mode();
   }
 
  protected:
-  const char *last_preset_mode_{""};
+  std::string_view last_preset_mode_{};
 };
 
 }  // namespace fan
diff --git a/esphome/components/fan/fan.cpp b/esphome/components/fan/fan.cpp
index b56ed72d9a..e24507678a 100644
--- a/esphome/components/fan/fan.cpp
+++ b/esphome/components/fan/fan.cpp
@@ -61,7 +61,7 @@ void FanCall::perform() {
   if (this->direction_.has_value()) {
     ESP_LOGD(TAG, "  Direction: %s", LOG_STR_ARG(fan_direction_to_string(*this->direction_)));
   }
-  if (this->has_preset_mode()) {
+  if (this->preset_mode_ != nullptr) {
     ESP_LOGD(TAG, "  Preset Mode: %s", this->preset_mode_);
   }
   this->parent_.control(*this);
@@ -201,8 +201,8 @@ void Fan::publish_state() {
   if (traits.supports_direction()) {
     ESP_LOGD(TAG, "  Direction: %s", LOG_STR_ARG(fan_direction_to_string(this->direction)));
   }
-  if (this->has_preset_mode()) {
-    ESP_LOGD(TAG, "  Preset Mode: %s", this->get_preset_mode());
+  if (this->preset_mode_ != nullptr) {
+    ESP_LOGD(TAG, "  Preset Mode: %s", this->preset_mode_);
   }
   this->state_callback_.call();
 #if defined(USE_FAN) && defined(USE_CONTROLLER_REGISTRY)
diff --git a/esphome/components/fan/fan.h b/esphome/components/fan/fan.h
index 17462c4108..eddcb7c2d3 100644
--- a/esphome/components/fan/fan.h
+++ b/esphome/components/fan/fan.h
@@ -1,5 +1,7 @@
 #pragma once
 
+#include <string_view>
+
 #include "esphome/core/entity_base.h"
 #include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
@@ -128,8 +130,10 @@ class Fan : public EntityBase {
   /// Set the restore mode of this fan.
   void set_restore_mode(FanRestoreMode restore_mode) { this->restore_mode_ = restore_mode; }
 
-  /// Get the current preset mode (returns pointer to string stored in traits, or empty string if not set)
-  const char *get_preset_mode() const { return this->preset_mode_ != nullptr ? this->preset_mode_ : ""; }
+  /// Get the current preset mode (returns view of string stored in traits, or empty view if not set)
+  std::string_view get_preset_mode() const {
+    return this->preset_mode_ != nullptr ? std::string_view(this->preset_mode_) : std::string_view();
+  }
 
   /// Check if a preset mode is currently active
   bool has_preset_mode() const { return this->preset_mode_ != nullptr; }

From 6c502d879b16d488be250e8872724b8bd336266a Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Thu, 8 Jan 2026 21:49:15 -1000
Subject: [PATCH 03/10] cleanup

---
 esphome/components/fan/fan.cpp | 20 +++++++++++++++-----
 esphome/components/fan/fan.h   |  3 ++-
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/esphome/components/fan/fan.cpp b/esphome/components/fan/fan.cpp
index e24507678a..3c1e1357f5 100644
--- a/esphome/components/fan/fan.cpp
+++ b/esphome/components/fan/fan.cpp
@@ -154,16 +154,16 @@ const char *Fan::find_preset_mode_(const char *preset_mode, size_t len) {
   return this->get_traits().find_preset_mode(preset_mode, len);
 }
 
-bool Fan::set_preset_mode_(const char *preset_mode) {
-  if (preset_mode == nullptr) {
-    // Treat nullptr as clearing the preset mode
+bool Fan::set_preset_mode_(const char *preset_mode, size_t len) {
+  if (preset_mode == nullptr || len == 0) {
+    // Treat nullptr/empty as clearing the preset mode
     if (this->preset_mode_ == nullptr) {
       return false;  // No change
     }
     this->clear_preset_mode_();
     return true;
   }
-  const char *validated = this->find_preset_mode_(preset_mode);
+  const char *validated = this->find_preset_mode_(preset_mode, len);
   if (validated == nullptr || this->preset_mode_ == validated) {
     return false;  // Preset mode not supported or no change
   }
@@ -171,7 +171,17 @@ bool Fan::set_preset_mode_(const char *preset_mode) {
   return true;
 }
 
-bool Fan::set_preset_mode_(const std::string &preset_mode) { return this->set_preset_mode_(preset_mode.c_str()); }
+bool Fan::set_preset_mode_(const char *preset_mode) {
+  return this->set_preset_mode_(preset_mode, preset_mode ? strlen(preset_mode) : 0);
+}
+
+bool Fan::set_preset_mode_(const std::string &preset_mode) {
+  return this->set_preset_mode_(preset_mode.data(), preset_mode.size());
+}
+
+bool Fan::set_preset_mode_(std::string_view preset_mode) {
+  return this->set_preset_mode_(preset_mode.data(), preset_mode.size());
+}
 
 void Fan::clear_preset_mode_() { this->preset_mode_ = nullptr; }
 
diff --git a/esphome/components/fan/fan.h b/esphome/components/fan/fan.h
index eddcb7c2d3..0504b1010e 100644
--- a/esphome/components/fan/fan.h
+++ b/esphome/components/fan/fan.h
@@ -150,9 +150,10 @@ class Fan : public EntityBase {
   void dump_traits_(const char *tag, const char *prefix);
 
   /// Set the preset mode (finds and stores pointer from traits). Returns true if changed.
+  bool set_preset_mode_(const char *preset_mode, size_t len);
   bool set_preset_mode_(const char *preset_mode);
-  /// Set the preset mode (finds and stores pointer from traits). Returns true if changed.
   bool set_preset_mode_(const std::string &preset_mode);
+  bool set_preset_mode_(std::string_view preset_mode);
   /// Clear the preset mode
   void clear_preset_mode_();
   /// Apply preset mode from a FanCall (handles speed-clears-preset convention)

From 1e30f54dffeaccb36062f46b310ad7e15d7c9053 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Thu, 8 Jan 2026 21:49:59 -1000
Subject: [PATCH 04/10] cleanup

---
 esphome/components/fan/fan.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/esphome/components/fan/fan.h b/esphome/components/fan/fan.h
index 0504b1010e..df42af9f99 100644
--- a/esphome/components/fan/fan.h
+++ b/esphome/components/fan/fan.h
@@ -130,7 +130,9 @@ class Fan : public EntityBase {
   /// Set the restore mode of this fan.
   void set_restore_mode(FanRestoreMode restore_mode) { this->restore_mode_ = restore_mode; }
 
-  /// Get the current preset mode (returns view of string stored in traits, or empty view if not set)
+  /// Get the current preset mode.
+  /// Returns a view of the string stored in traits (static storage), or empty view if not set.
+  /// Safe to use as the underlying string has static lifetime.
   std::string_view get_preset_mode() const {
     return this->preset_mode_ != nullptr ? std::string_view(this->preset_mode_) : std::string_view();
   }

From 04eba0563af538b47233100181fd20de3d2c75bb Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Thu, 8 Jan 2026 21:58:20 -1000
Subject: [PATCH 05/10] tests

---
 tests/components/copy/common.yaml | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tests/components/copy/common.yaml b/tests/components/copy/common.yaml
index a73b3467e6..a376004b2f 100644
--- a/tests/components/copy/common.yaml
+++ b/tests/components/copy/common.yaml
@@ -7,6 +7,9 @@ fan:
   - platform: speed
     id: fan_speed
     output: fan_output_1
+    preset_modes:
+      - Eco
+      - Turbo
   - platform: copy
     source_id: fan_speed
     name: Fan Speed Copy

From 0ebe99ccf5f1badd70a6385e04ca32c32b08c016 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Thu, 8 Jan 2026 22:00:04 -1000
Subject: [PATCH 06/10] tests

---
 tests/components/fan/common.yaml | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/tests/components/fan/common.yaml b/tests/components/fan/common.yaml
index 55c2a656fd..bbd5be327a 100644
--- a/tests/components/fan/common.yaml
+++ b/tests/components/fan/common.yaml
@@ -9,3 +9,27 @@ fan:
     has_oscillating: true
     has_direction: true
     speed_count: 3
+
+# Test lambdas using get_preset_mode() which returns std::string_view
+binary_sensor:
+  - platform: template
+    id: fan_has_preset
+    name: "Fan Has Preset"
+    lambda: |-
+      // Test has_preset_mode() method
+      if (!id(test_fan).has_preset_mode()) {
+        return false;
+      }
+      // Test .empty() on string_view
+      if (id(test_fan).get_preset_mode().empty()) {
+        return false;
+      }
+      // Test == comparison with string literal
+      if (id(test_fan).get_preset_mode() == "Eco") {
+        return true;
+      }
+      // Test != comparison
+      if (id(test_fan).get_preset_mode() != "Sleep") {
+        return true;
+      }
+      return false;

From cd76747b259d4a5164f90f161770c8a2f0277db2 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Thu, 8 Jan 2026 22:19:52 -1000
Subject: [PATCH 07/10] tests

---
 tests/components/fan/common.yaml | 38 ++++++++++++++++++++++++++------
 1 file changed, 31 insertions(+), 7 deletions(-)

diff --git a/tests/components/fan/common.yaml b/tests/components/fan/common.yaml
index bbd5be327a..ccc822be5a 100644
--- a/tests/components/fan/common.yaml
+++ b/tests/components/fan/common.yaml
@@ -11,23 +11,47 @@ fan:
     speed_count: 3
 
 # Test lambdas using get_preset_mode() which returns std::string_view
+# These examples match the migration guide in the PR description
 binary_sensor:
   - platform: template
     id: fan_has_preset
     name: "Fan Has Preset"
     lambda: |-
-      // Test has_preset_mode() method
-      if (!id(test_fan).has_preset_mode()) {
-        return false;
+      // Migration guide: Checking if preset mode is set
+      // Use empty() or has_preset_mode()
+      if (!id(test_fan).get_preset_mode().empty()) {
+        // preset is set
       }
-      // Test .empty() on string_view
-      if (id(test_fan).get_preset_mode().empty()) {
-        return false;
+      if (id(test_fan).has_preset_mode()) {
+        // preset is set
       }
-      // Test == comparison with string literal
+
+      // Migration guide: Comparing preset mode
+      // Use == operator directly (safe, works even when empty)
       if (id(test_fan).get_preset_mode() == "Eco") {
         return true;
       }
+
+      // Migration guide: Checking for no preset
+      if (id(test_fan).get_preset_mode().empty()) {
+        // no preset
+      }
+      if (!id(test_fan).has_preset_mode()) {
+        // no preset
+      }
+
+      // Migration guide: Getting as std::string
+      std::string preset = std::string(id(test_fan).get_preset_mode());
+
+      // Migration guide: Logging option 1
+      // Use .data() - works because string_view points to null-terminated string in traits
+      ESP_LOGD("test", "Preset: %s", id(test_fan).get_preset_mode().data());
+
+      // Migration guide: Logging option 2
+      // Use %.*s format (safer, no null-termination assumption)
+      auto preset_view = id(test_fan).get_preset_mode();
+      ESP_LOGD("test", "Preset: %.*s", (int)preset_view.size(), preset_view.data());
+
       // Test != comparison
       if (id(test_fan).get_preset_mode() != "Sleep") {
         return true;

From a3553dab1ccdc2e1d1de80a77c7f96c3de8b2566 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Thu, 8 Jan 2026 22:24:38 -1000
Subject: [PATCH 08/10] address copilot review comments

---
 esphome/components/fan/fan.cpp | 4 +++-
 esphome/components/fan/fan.h   | 5 +++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/esphome/components/fan/fan.cpp b/esphome/components/fan/fan.cpp
index 3c1e1357f5..79301a2e18 100644
--- a/esphome/components/fan/fan.cpp
+++ b/esphome/components/fan/fan.cpp
@@ -156,7 +156,7 @@ const char *Fan::find_preset_mode_(const char *preset_mode, size_t len) {
 
 bool Fan::set_preset_mode_(const char *preset_mode, size_t len) {
   if (preset_mode == nullptr || len == 0) {
-    // Treat nullptr/empty as clearing the preset mode
+    // Treat nullptr or empty string as clearing the preset mode (no valid preset is "")
     if (this->preset_mode_ == nullptr) {
       return false;  // No change
     }
@@ -180,6 +180,8 @@ bool Fan::set_preset_mode_(const std::string &preset_mode) {
 }
 
 bool Fan::set_preset_mode_(std::string_view preset_mode) {
+  // Safe: find_preset_mode_ only uses the input for comparison and returns
+  // a pointer from traits, so the input string_view's lifetime doesn't matter.
   return this->set_preset_mode_(preset_mode.data(), preset_mode.size());
 }
 
diff --git a/esphome/components/fan/fan.h b/esphome/components/fan/fan.h
index df42af9f99..c16ec389f2 100644
--- a/esphome/components/fan/fan.h
+++ b/esphome/components/fan/fan.h
@@ -131,8 +131,9 @@ class Fan : public EntityBase {
   void set_restore_mode(FanRestoreMode restore_mode) { this->restore_mode_ = restore_mode; }
 
   /// Get the current preset mode.
-  /// Returns a view of the string stored in traits (static storage), or empty view if not set.
-  /// Safe to use as the underlying string has static lifetime.
+  /// Returns a view of the string stored in traits, or empty view if not set.
+  /// The returned view points to string literals from codegen (static storage).
+  /// Traits are set once at startup and valid for the lifetime of the program.
   std::string_view get_preset_mode() const {
     return this->preset_mode_ != nullptr ? std::string_view(this->preset_mode_) : std::string_view();
   }

From 872b2ec7db63cd420e37a4ad3c5b9aebd6289df3 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Thu, 8 Jan 2026 22:25:16 -1000
Subject: [PATCH 09/10] address copilot review comments

---
 esphome/components/fan/fan.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/esphome/components/fan/fan.h b/esphome/components/fan/fan.h
index c16ec389f2..f1b17d7e15 100644
--- a/esphome/components/fan/fan.h
+++ b/esphome/components/fan/fan.h
@@ -153,6 +153,7 @@ class Fan : public EntityBase {
   void dump_traits_(const char *tag, const char *prefix);
 
   /// Set the preset mode (finds and stores pointer from traits). Returns true if changed.
+  /// Passing nullptr or empty string clears the preset mode.
   bool set_preset_mode_(const char *preset_mode, size_t len);
   bool set_preset_mode_(const char *preset_mode);
   bool set_preset_mode_(const std::string &preset_mode);

From 1fdacd9d22a06ab55562093dfd28d7f90f3537d1 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Fri, 9 Jan 2026 15:40:18 -1000
Subject: [PATCH 10/10] use stringref

---
 esphome/components/api/api_connection.cpp |  6 ++----
 esphome/components/fan/automation.h       |  2 +-
 esphome/components/fan/fan.cpp            |  6 +++---
 esphome/components/fan/fan.h              | 13 +++++--------
 tests/components/fan/common.yaml          | 10 +++++-----
 5 files changed, 16 insertions(+), 21 deletions(-)

diff --git a/esphome/components/api/api_connection.cpp b/esphome/components/api/api_connection.cpp
index 989536aca0..4bc19a8bad 100644
--- a/esphome/components/api/api_connection.cpp
+++ b/esphome/components/api/api_connection.cpp
@@ -442,10 +442,8 @@ uint16_t APIConnection::try_send_fan_state(EntityBase *entity, APIConnection *co
   }
   if (traits.supports_direction())
     msg.direction = static_cast<enums::FanDirection>(fan->direction);
-  if (traits.supports_preset_modes() && fan->has_preset_mode()) {
-    auto preset = fan->get_preset_mode();
-    msg.preset_mode = StringRef(preset.data(), preset.size());
-  }
+  if (traits.supports_preset_modes() && fan->has_preset_mode())
+    msg.preset_mode = fan->get_preset_mode();
   return fill_and_encode_entity_state(fan, msg, FanStateResponse::MESSAGE_TYPE, conn, remaining_size, is_single);
 }
 uint16_t APIConnection::try_send_fan_info(EntityBase *entity, APIConnection *conn, uint32_t remaining_size,
diff --git a/esphome/components/fan/automation.h b/esphome/components/fan/automation.h
index 8175caefea..77abc2f13f 100644
--- a/esphome/components/fan/automation.h
+++ b/esphome/components/fan/automation.h
@@ -223,7 +223,7 @@ class FanPresetSetTrigger : public Trigger<std::string> {
   }
 
  protected:
-  std::string_view last_preset_mode_{};
+  StringRef last_preset_mode_{};
 };
 
 }  // namespace fan
diff --git a/esphome/components/fan/fan.cpp b/esphome/components/fan/fan.cpp
index 79301a2e18..2e48d84eb9 100644
--- a/esphome/components/fan/fan.cpp
+++ b/esphome/components/fan/fan.cpp
@@ -179,10 +179,10 @@ bool Fan::set_preset_mode_(const std::string &preset_mode) {
   return this->set_preset_mode_(preset_mode.data(), preset_mode.size());
 }
 
-bool Fan::set_preset_mode_(std::string_view preset_mode) {
+bool Fan::set_preset_mode_(StringRef preset_mode) {
   // Safe: find_preset_mode_ only uses the input for comparison and returns
-  // a pointer from traits, so the input string_view's lifetime doesn't matter.
-  return this->set_preset_mode_(preset_mode.data(), preset_mode.size());
+  // a pointer from traits, so the input StringRef's lifetime doesn't matter.
+  return this->set_preset_mode_(preset_mode.c_str(), preset_mode.size());
 }
 
 void Fan::clear_preset_mode_() { this->preset_mode_ = nullptr; }
diff --git a/esphome/components/fan/fan.h b/esphome/components/fan/fan.h
index f1b17d7e15..55d4ba8825 100644
--- a/esphome/components/fan/fan.h
+++ b/esphome/components/fan/fan.h
@@ -1,12 +1,11 @@
 #pragma once
 
-#include <string_view>
-
 #include "esphome/core/entity_base.h"
 #include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 #include "esphome/core/optional.h"
 #include "esphome/core/preferences.h"
+#include "esphome/core/string_ref.h"
 #include "fan_traits.h"
 
 namespace esphome {
@@ -131,12 +130,10 @@ class Fan : public EntityBase {
   void set_restore_mode(FanRestoreMode restore_mode) { this->restore_mode_ = restore_mode; }
 
   /// Get the current preset mode.
-  /// Returns a view of the string stored in traits, or empty view if not set.
-  /// The returned view points to string literals from codegen (static storage).
+  /// Returns a StringRef of the string stored in traits, or empty ref if not set.
+  /// The returned ref points to string literals from codegen (static storage).
   /// Traits are set once at startup and valid for the lifetime of the program.
-  std::string_view get_preset_mode() const {
-    return this->preset_mode_ != nullptr ? std::string_view(this->preset_mode_) : std::string_view();
-  }
+  StringRef get_preset_mode() const { return StringRef::from_maybe_nullptr(this->preset_mode_); }
 
   /// Check if a preset mode is currently active
   bool has_preset_mode() const { return this->preset_mode_ != nullptr; }
@@ -157,7 +154,7 @@ class Fan : public EntityBase {
   bool set_preset_mode_(const char *preset_mode, size_t len);
   bool set_preset_mode_(const char *preset_mode);
   bool set_preset_mode_(const std::string &preset_mode);
-  bool set_preset_mode_(std::string_view preset_mode);
+  bool set_preset_mode_(StringRef preset_mode);
   /// Clear the preset mode
   void clear_preset_mode_();
   /// Apply preset mode from a FanCall (handles speed-clears-preset convention)
diff --git a/tests/components/fan/common.yaml b/tests/components/fan/common.yaml
index ccc822be5a..099bbfef08 100644
--- a/tests/components/fan/common.yaml
+++ b/tests/components/fan/common.yaml
@@ -10,7 +10,7 @@ fan:
     has_direction: true
     speed_count: 3
 
-# Test lambdas using get_preset_mode() which returns std::string_view
+# Test lambdas using get_preset_mode() which returns StringRef
 # These examples match the migration guide in the PR description
 binary_sensor:
   - platform: template
@@ -44,13 +44,13 @@ binary_sensor:
       std::string preset = std::string(id(test_fan).get_preset_mode());
 
       // Migration guide: Logging option 1
-      // Use .data() - works because string_view points to null-terminated string in traits
-      ESP_LOGD("test", "Preset: %s", id(test_fan).get_preset_mode().data());
+      // Use .c_str() - works because StringRef points to null-terminated string in traits
+      ESP_LOGD("test", "Preset: %s", id(test_fan).get_preset_mode().c_str());
 
       // Migration guide: Logging option 2
       // Use %.*s format (safer, no null-termination assumption)
-      auto preset_view = id(test_fan).get_preset_mode();
-      ESP_LOGD("test", "Preset: %.*s", (int)preset_view.size(), preset_view.data());
+      auto preset_ref = id(test_fan).get_preset_mode();
+      ESP_LOGD("test", "Preset: %.*s", (int)preset_ref.size(), preset_ref.c_str());
 
       // Test != comparison
       if (id(test_fan).get_preset_mode() != "Sleep") {