diff --git a/esphome/components/api/api.proto b/esphome/components/api/api.proto
index 9b714d00f1..87f477799d 100644
--- a/esphome/components/api/api.proto
+++ b/esphome/components/api/api.proto
@@ -1519,7 +1519,7 @@ message BluetoothGATTCharacteristic {
   repeated uint64 uuid = 1 [(fixed_array_size) = 2, (fixed_array_skip_zero) = true];
   uint32 handle = 2;
   uint32 properties = 3;
-  repeated BluetoothGATTDescriptor descriptors = 4 [(fixed_vector) = true];
+  repeated BluetoothGATTDescriptor descriptors = 4;
 
   // New field for efficient UUID (v1.12+)
   // Only one of uuid or short_uuid will be set.
@@ -1531,7 +1531,7 @@ message BluetoothGATTCharacteristic {
 message BluetoothGATTService {
   repeated uint64 uuid = 1 [(fixed_array_size) = 2, (fixed_array_skip_zero) = true];
   uint32 handle = 2;
-  repeated BluetoothGATTCharacteristic characteristics = 3 [(fixed_vector) = true];
+  repeated BluetoothGATTCharacteristic characteristics = 3;
 
   // New field for efficient UUID (v1.12+)
   // Only one of uuid or short_uuid will be set.
diff --git a/esphome/components/api/api_options.proto b/esphome/components/api/api_options.proto
index ead8ac0bbc..633f39b552 100644
--- a/esphome/components/api/api_options.proto
+++ b/esphome/components/api/api_options.proto
@@ -64,10 +64,4 @@ extend google.protobuf.FieldOptions {
     // This is typically done through methods returning const T& or special accessor
     // methods like get_options() or supported_modes_for_api_().
     optional string container_pointer = 50001;
-
-    // fixed_vector: Use FixedVector instead of std::vector for repeated fields
-    // When set, the repeated field will use FixedVector<T> which requires calling
-    // init(size) before adding elements. This eliminates std::vector template overhead
-    // and is ideal when the exact size is known before populating the array.
-    optional bool fixed_vector = 50013 [default=false];
 }
diff --git a/esphome/components/api/api_pb2.h b/esphome/components/api/api_pb2.h
index 1798458393..d9e68ece9b 100644
--- a/esphome/components/api/api_pb2.h
+++ b/esphome/components/api/api_pb2.h
@@ -1923,7 +1923,7 @@ class BluetoothGATTCharacteristic final : public ProtoMessage {
   std::array<uint64_t, 2> uuid{};
   uint32_t handle{0};
   uint32_t properties{0};
-  FixedVector<BluetoothGATTDescriptor> descriptors{};
+  std::vector<BluetoothGATTDescriptor> descriptors{};
   uint32_t short_uuid{0};
   void encode(ProtoWriteBuffer buffer) const override;
   void calculate_size(ProtoSize &size) const override;
@@ -1937,7 +1937,7 @@ class BluetoothGATTService final : public ProtoMessage {
  public:
   std::array<uint64_t, 2> uuid{};
   uint32_t handle{0};
-  FixedVector<BluetoothGATTCharacteristic> characteristics{};
+  std::vector<BluetoothGATTCharacteristic> characteristics{};
   uint32_t short_uuid{0};
   void encode(ProtoWriteBuffer buffer) const override;
   void calculate_size(ProtoSize &size) const override;
diff --git a/esphome/components/api/proto.h b/esphome/components/api/proto.h
index a6a09bf7c5..9d780692ec 100644
--- a/esphome/components/api/proto.h
+++ b/esphome/components/api/proto.h
@@ -749,29 +749,13 @@ class ProtoSize {
   template<typename MessageType>
   inline void add_repeated_message(uint32_t field_id_size, const std::vector<MessageType> &messages) {
     // Skip if the vector is empty
-    if (!messages.empty()) {
-      // Use the force version for all messages in the repeated field
-      for (const auto &message : messages) {
-        add_message_object_force(field_id_size, message);
-      }
+    if (messages.empty()) {
+      return;
     }
-  }
 
-  /**
-   * @brief Calculates and adds the sizes of all messages in a repeated field to the total message size (FixedVector
-   * version)
-   *
-   * @tparam MessageType The type of the nested messages in the FixedVector
-   * @param messages FixedVector of message objects
-   */
-  template<typename MessageType>
-  inline void add_repeated_message(uint32_t field_id_size, const FixedVector<MessageType> &messages) {
-    // Skip if the fixed vector is empty
-    if (!messages.empty()) {
-      // Use the force version for all messages in the repeated field
-      for (const auto &message : messages) {
-        add_message_object_force(field_id_size, message);
-      }
+    // Use the force version for all messages in the repeated field
+    for (const auto &message : messages) {
+      add_message_object_force(field_id_size, message);
     }
   }
 };
diff --git a/esphome/components/bluetooth_proxy/bluetooth_connection.cpp b/esphome/components/bluetooth_proxy/bluetooth_connection.cpp
index 6f172b0bcf..cde82fbfb0 100644
--- a/esphome/components/bluetooth_proxy/bluetooth_connection.cpp
+++ b/esphome/components/bluetooth_proxy/bluetooth_connection.cpp
@@ -230,8 +230,8 @@ void BluetoothConnection::send_service_for_discovery_() {
     service_resp.handle = service_result.start_handle;
 
     if (total_char_count > 0) {
-      // Initialize FixedVector with exact count and process characteristics
-      service_resp.characteristics.init(total_char_count);
+      // Reserve space and process characteristics
+      service_resp.characteristics.reserve(total_char_count);
       uint16_t char_offset = 0;
       esp_gattc_char_elem_t char_result;
       while (true) {  // characteristics
@@ -275,8 +275,8 @@ void BluetoothConnection::send_service_for_discovery_() {
           continue;
         }
 
-        // Initialize FixedVector with exact count and process descriptors
-        characteristic_resp.descriptors.init(total_desc_count);
+        // Reserve space and process descriptors
+        characteristic_resp.descriptors.reserve(total_desc_count);
         uint16_t desc_offset = 0;
         esp_gattc_descr_elem_t desc_result;
         while (true) {  // descriptors
diff --git a/esphome/components/wifi/wifi_component.cpp b/esphome/components/wifi/wifi_component.cpp
index 644dffeb82..2365e3f560 100644
--- a/esphome/components/wifi/wifi_component.cpp
+++ b/esphome/components/wifi/wifi_component.cpp
@@ -554,7 +554,7 @@ void WiFiComponent::start_scanning() {
 // Using insertion sort instead of std::stable_sort saves flash memory
 // by avoiding template instantiations (std::rotate, std::stable_sort, lambdas)
 // IMPORTANT: This sort is stable (preserves relative order of equal elements)
-static void insertion_sort_scan_results(std::vector<WiFiScanResult> &results) {
+template<typename VectorType> static void insertion_sort_scan_results(VectorType &results) {
   const size_t size = results.size();
   for (size_t i = 1; i < size; i++) {
     // Make a copy to avoid issues with move semantics during comparison
diff --git a/esphome/components/wifi/wifi_component.h b/esphome/components/wifi/wifi_component.h
index c0b63e1858..bae047eb9d 100644
--- a/esphome/components/wifi/wifi_component.h
+++ b/esphome/components/wifi/wifi_component.h
@@ -121,6 +121,14 @@ struct EAPAuth {
 
 using bssid_t = std::array<uint8_t, 6>;
 
+// Use std::vector for RP2040 since scan count is unknown (callback-based)
+// Use FixedVector for other platforms where count is queried first
+#ifdef USE_RP2040
+template<typename T> using wifi_scan_vector_t = std::vector<T>;
+#else
+template<typename T> using wifi_scan_vector_t = FixedVector<T>;
+#endif
+
 class WiFiAP {
  public:
   void set_ssid(const std::string &ssid);
@@ -278,7 +286,7 @@ class WiFiComponent : public Component {
   std::string get_use_address() const;
   void set_use_address(const std::string &use_address);
 
-  const std::vector<WiFiScanResult> &get_scan_result() const { return scan_result_; }
+  const wifi_scan_vector_t<WiFiScanResult> &get_scan_result() const { return scan_result_; }
 
   network::IPAddress wifi_soft_ap_ip();
 
@@ -386,7 +394,7 @@ class WiFiComponent : public Component {
   std::string use_address_;
   std::vector<WiFiAP> sta_;
   std::vector<WiFiSTAPriority> sta_priorities_;
-  std::vector<WiFiScanResult> scan_result_;
+  wifi_scan_vector_t<WiFiScanResult> scan_result_;
   WiFiAP selected_ap_;
   WiFiAP ap_;
   optional<float> output_power_;
diff --git a/esphome/components/wifi/wifi_component_esp8266.cpp b/esphome/components/wifi/wifi_component_esp8266.cpp
index 3b3b4b139c..59909b2cb5 100644
--- a/esphome/components/wifi/wifi_component_esp8266.cpp
+++ b/esphome/components/wifi/wifi_component_esp8266.cpp
@@ -696,7 +696,15 @@ void WiFiComponent::wifi_scan_done_callback_(void *arg, STATUS status) {
     this->retry_connect();
     return;
   }
+
+  // Count the number of results first
   auto *head = reinterpret_cast<bss_info *>(arg);
+  size_t count = 0;
+  for (bss_info *it = head; it != nullptr; it = STAILQ_NEXT(it, next)) {
+    count++;
+  }
+
+  this->scan_result_.init(count);
   for (bss_info *it = head; it != nullptr; it = STAILQ_NEXT(it, next)) {
     WiFiScanResult res({it->bssid[0], it->bssid[1], it->bssid[2], it->bssid[3], it->bssid[4], it->bssid[5]},
                        std::string(reinterpret_cast<char *>(it->ssid), it->ssid_len), it->channel, it->rssi,
diff --git a/esphome/components/wifi/wifi_component_esp_idf.cpp b/esphome/components/wifi/wifi_component_esp_idf.cpp
index ccec800205..951f5803a6 100644
--- a/esphome/components/wifi/wifi_component_esp_idf.cpp
+++ b/esphome/components/wifi/wifi_component_esp_idf.cpp
@@ -784,7 +784,7 @@ void WiFiComponent::wifi_process_event_(IDFWiFiEvent *data) {
     }
     records.resize(number);
 
-    scan_result_.reserve(number);
+    scan_result_.init(number);
     for (int i = 0; i < number; i++) {
       auto &record = records[i];
       bssid_t bssid;
diff --git a/esphome/components/wifi/wifi_component_libretiny.cpp b/esphome/components/wifi/wifi_component_libretiny.cpp
index b15f710150..cb179d9022 100644
--- a/esphome/components/wifi/wifi_component_libretiny.cpp
+++ b/esphome/components/wifi/wifi_component_libretiny.cpp
@@ -411,7 +411,7 @@ void WiFiComponent::wifi_scan_done_callback_() {
   if (num < 0)
     return;
 
-  this->scan_result_.reserve(static_cast<unsigned int>(num));
+  this->scan_result_.init(static_cast<unsigned int>(num));
   for (int i = 0; i < num; i++) {
     String ssid = WiFi.SSID(i);
     wifi_auth_mode_t authmode = WiFi.encryptionType(i);
diff --git a/script/api_protobuf/api_protobuf.py b/script/api_protobuf/api_protobuf.py
index 9a55f1d136..487c187372 100755
--- a/script/api_protobuf/api_protobuf.py
+++ b/script/api_protobuf/api_protobuf.py
@@ -1415,8 +1415,6 @@ class RepeatedTypeInfo(TypeInfo):
         # Check if this is a pointer field by looking for container_pointer option
         self._container_type = get_field_opt(field, pb.container_pointer, "")
         self._use_pointer = bool(self._container_type)
-        # Check if this should use FixedVector instead of std::vector
-        self._use_fixed_vector = get_field_opt(field, pb.fixed_vector, False)
 
         # For repeated fields, we need to get the base type info
         # but we can't call create_field_type_info as it would cause recursion
@@ -1440,8 +1438,6 @@ class RepeatedTypeInfo(TypeInfo):
             if "<" in self._container_type and ">" in self._container_type:
                 return f"const {self._container_type}*"
             return f"const {self._container_type}<{self._ti.cpp_type}>*"
-        if self._use_fixed_vector:
-            return f"FixedVector<{self._ti.cpp_type}>"
         return f"std::vector<{self._ti.cpp_type}>"
 
     @property