From 541c697a42e5ff46434a3f4fdcf4e8e1cb6c6777 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Mon, 13 Oct 2025 18:52:49 -1000
Subject: [PATCH 1/4] [mdns] Use FixedVector for txt_records to reduce flash
 usage

---
 esphome/components/mdns/mdns_component.cpp | 4 ++--
 esphome/components/mdns/mdns_component.h   | 2 +-
 esphome/core/helpers.h                     | 9 +++++++++
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/esphome/components/mdns/mdns_component.cpp b/esphome/components/mdns/mdns_component.cpp
index fea3ced99f..ef585db51b 100644
--- a/esphome/components/mdns/mdns_component.cpp
+++ b/esphome/components/mdns/mdns_component.cpp
@@ -83,7 +83,7 @@ void MDNSComponent::compile_records_(StaticVector<MDNSService, MDNS_SERVICE_COUN
 #endif
 
     auto &txt_records = service.txt_records;
-    txt_records.reserve(txt_count);
+    txt_records.init(txt_count);
 
     if (!friendly_name_empty) {
       txt_records.push_back({MDNS_STR(TXT_FRIENDLY_NAME), MDNS_STR(friendly_name.c_str())});
@@ -171,7 +171,7 @@ void MDNSComponent::compile_records_(StaticVector<MDNSService, MDNS_SERVICE_COUN
   fallback_service.service_type = MDNS_STR(SERVICE_HTTP);
   fallback_service.proto = MDNS_STR(SERVICE_TCP);
   fallback_service.port = USE_WEBSERVER_PORT;
-  fallback_service.txt_records.push_back({MDNS_STR(TXT_VERSION), MDNS_STR(VALUE_VERSION)});
+  fallback_service.txt_records = {{MDNS_STR(TXT_VERSION), MDNS_STR(VALUE_VERSION)}};
 #endif
 
 #ifdef USE_MDNS_STORE_SERVICES
diff --git a/esphome/components/mdns/mdns_component.h b/esphome/components/mdns/mdns_component.h
index 62476e9504..35371fd739 100644
--- a/esphome/components/mdns/mdns_component.h
+++ b/esphome/components/mdns/mdns_component.h
@@ -38,7 +38,7 @@ struct MDNSService {
   // as defined in RFC6763 Section 7, like "_tcp" or "_udp"
   const MDNSString *proto;
   TemplatableValue<uint16_t> port;
-  std::vector<MDNSTXTRecord> txt_records;
+  FixedVector<MDNSTXTRecord> txt_records;
 };
 
 class MDNSComponent : public Component {
diff --git a/esphome/core/helpers.h b/esphome/core/helpers.h
index e352c9c415..b94826629f 100644
--- a/esphome/core/helpers.h
+++ b/esphome/core/helpers.h
@@ -197,6 +197,15 @@ template<typename T> class FixedVector {
  public:
   FixedVector() = default;
 
+  /// Constructor from initializer list - allocates exact size needed
+  /// This enables brace initialization: FixedVector<int> v = {1, 2, 3};
+  FixedVector(std::initializer_list<T> init) {
+    init(init.size());
+    for (const auto &item : init) {
+      push_back(item);
+    }
+  }
+
   ~FixedVector() { cleanup_(); }
 
   // Disable copy operations (avoid accidental expensive copies)

From ac35c97a44a339dd6e69bcc503a5aa9edec5e156 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Mon, 13 Oct 2025 18:59:46 -1000
Subject: [PATCH 2/4] we need copy now

---
 esphome/core/helpers.h | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/esphome/core/helpers.h b/esphome/core/helpers.h
index b94826629f..c0e73b70e0 100644
--- a/esphome/core/helpers.h
+++ b/esphome/core/helpers.h
@@ -208,9 +208,30 @@ template<typename T> class FixedVector {
 
   ~FixedVector() { cleanup_(); }
 
-  // Disable copy operations (avoid accidental expensive copies)
-  FixedVector(const FixedVector &) = delete;
-  FixedVector &operator=(const FixedVector &) = delete;
+  // Copy constructor - performs deep copy
+  FixedVector(const FixedVector &other) {
+    if (other.size_ > 0) {
+      init(other.size_);
+      for (size_t i = 0; i < other.size_; i++) {
+        push_back(other.data_[i]);
+      }
+    }
+  }
+
+  // Copy assignment operator - performs deep copy
+  FixedVector &operator=(const FixedVector &other) {
+    if (this != &other) {
+      cleanup_();
+      reset_();
+      if (other.size_ > 0) {
+        init(other.size_);
+        for (size_t i = 0; i < other.size_; i++) {
+          push_back(other.data_[i]);
+        }
+      }
+    }
+    return *this;
+  }
 
   // Enable move semantics (allows use in move-only containers like std::vector)
   FixedVector(FixedVector &&other) noexcept : data_(other.data_), size_(other.size_), capacity_(other.capacity_) {

From 45014db02796aad16e103f649f30f955baa6c242 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Mon, 13 Oct 2025 19:05:26 -1000
Subject: [PATCH 3/4] preen

---
 esphome/components/mdns/mdns_component.cpp |  4 +--
 esphome/core/helpers.h                     | 29 +++-------------------
 2 files changed, 6 insertions(+), 27 deletions(-)

diff --git a/esphome/components/mdns/mdns_component.cpp b/esphome/components/mdns/mdns_component.cpp
index ef585db51b..7b36fce229 100644
--- a/esphome/components/mdns/mdns_component.cpp
+++ b/esphome/components/mdns/mdns_component.cpp
@@ -175,8 +175,8 @@ void MDNSComponent::compile_records_(StaticVector<MDNSService, MDNS_SERVICE_COUN
 #endif
 
 #ifdef USE_MDNS_STORE_SERVICES
-  // Copy to member variable if storage is enabled (verbose logging, OpenThread, or extra services)
-  this->services_ = services;
+  // Move to member variable if storage is enabled (verbose logging, OpenThread, or extra services)
+  this->services_ = std::move(services);
 #endif
 }
 
diff --git a/esphome/core/helpers.h b/esphome/core/helpers.h
index c0e73b70e0..a9c0427917 100644
--- a/esphome/core/helpers.h
+++ b/esphome/core/helpers.h
@@ -208,32 +208,11 @@ template<typename T> class FixedVector {
 
   ~FixedVector() { cleanup_(); }
 
-  // Copy constructor - performs deep copy
-  FixedVector(const FixedVector &other) {
-    if (other.size_ > 0) {
-      init(other.size_);
-      for (size_t i = 0; i < other.size_; i++) {
-        push_back(other.data_[i]);
-      }
-    }
-  }
+  // Disable copy operations - use std::move() to transfer ownership
+  FixedVector(const FixedVector &) = delete;
+  FixedVector &operator=(const FixedVector &) = delete;
 
-  // Copy assignment operator - performs deep copy
-  FixedVector &operator=(const FixedVector &other) {
-    if (this != &other) {
-      cleanup_();
-      reset_();
-      if (other.size_ > 0) {
-        init(other.size_);
-        for (size_t i = 0; i < other.size_; i++) {
-          push_back(other.data_[i]);
-        }
-      }
-    }
-    return *this;
-  }
-
-  // Enable move semantics (allows use in move-only containers like std::vector)
+  // Enable move semantics
   FixedVector(FixedVector &&other) noexcept : data_(other.data_), size_(other.size_), capacity_(other.capacity_) {
     other.reset_();
   }

From fc30326e603834154703b66e8a373bc2cf1ad498 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Mon, 13 Oct 2025 19:06:02 -1000
Subject: [PATCH 4/4] preen

---
 esphome/core/helpers.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/esphome/core/helpers.h b/esphome/core/helpers.h
index a9c0427917..b94826629f 100644
--- a/esphome/core/helpers.h
+++ b/esphome/core/helpers.h
@@ -208,11 +208,11 @@ template<typename T> class FixedVector {
 
   ~FixedVector() { cleanup_(); }
 
-  // Disable copy operations - use std::move() to transfer ownership
+  // Disable copy operations (avoid accidental expensive copies)
   FixedVector(const FixedVector &) = delete;
   FixedVector &operator=(const FixedVector &) = delete;
 
-  // Enable move semantics
+  // Enable move semantics (allows use in move-only containers like std::vector)
   FixedVector(FixedVector &&other) noexcept : data_(other.data_), size_(other.size_), capacity_(other.capacity_) {
     other.reset_();
   }