From f72130d074283357903f6b21fedd21180b74cc85 Mon Sep 17 00:00:00 2001
From: clydebarrow <2366188+clydebarrow@users.noreply.github.com>
Date: Mon, 19 Oct 2026 11:18:23 +1100
Subject: [PATCH] [entity_transport] Fail when the packet buffer cannot be
 allocated

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 .../entity_transport/entity_transport.cpp         | 15 ++++++++++-----
 .../entity_transport/entity_transport.h           |  3 +--
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/esphome/components/entity_transport/entity_transport.cpp b/esphome/components/entity_transport/entity_transport.cpp
index 85fe93acba7..40d1eb8a99f 100644
--- a/esphome/components/entity_transport/entity_transport.cpp
+++ b/esphome/components/entity_transport/entity_transport.cpp
@@ -58,7 +58,12 @@ void EntityTransport::setup() {
     this->mark_failed(LOG_STR("max_packet_size too small for the device name and entity ids"));
     return;
   }
-  this->buffer_ = std::make_unique<uint8_t[]>(this->max_packet_size_);
+  RAMAllocator<uint8_t> allocator;
+  this->buffer_ = allocator.allocate(this->max_packet_size_);
+  if (this->buffer_ == nullptr) {
+    this->mark_failed(LOG_STR("Not enough memory for the packet buffer"));
+    return;
+  }
   // The dictionary id changes when the device name or any entity changes
   uint32_t hash = fnv1a_hash(name.c_str());
   for (const auto &entity : this->entities_) {
@@ -163,12 +168,12 @@ void EntityTransport::loop() {
 
 size_t EntityTransport::write_header_(uint8_t type) const {
   this->buffer_[0] = type;
-  put_uint32(this->buffer_.get() + 1, this->dictionary_id_);
+  put_uint32(this->buffer_ + 1, this->dictionary_id_);
   return HEADER_SIZE;
 }
 
 bool EntityTransport::send_dictionary_() {
-  uint8_t *buf = this->buffer_.get();
+  uint8_t *buf = this->buffer_;
   const auto &name = App.get_name();
   size_t header = this->write_header_(PACKET_DICTIONARY);
   buf[header++] = name.size();
@@ -227,7 +232,7 @@ bool EntityTransport::send_updated_() {
       this->buffer_[SENSOR_COUNT_OFFSET] = 0;
       first = i;
     }
-    uint8_t *record = this->buffer_.get() + length;
+    uint8_t *record = this->buffer_ + length;
     record[0] = entity.number;
 #ifdef USE_SENSOR
     if (entity.is_sensor) {
@@ -253,7 +258,7 @@ bool EntityTransport::send_updated_() {
 bool EntityTransport::flush_(size_t length, size_t first, size_t last) {
   if (length == DATA_HEADER_SIZE)
     return true;
-  if (!this->interface_->send_to_interface(PacketBuffer(this->buffer_.get(), length), {})) {
+  if (!this->interface_->send_to_interface(PacketBuffer(this->buffer_, length), {})) {
     ESP_LOGV(TAG, "Packet of %zu bytes not accepted, will retry", length);
     return false;
   }
diff --git a/esphome/components/entity_transport/entity_transport.h b/esphome/components/entity_transport/entity_transport.h
index 360e26a557b..b1c0a88c91f 100644
--- a/esphome/components/entity_transport/entity_transport.h
+++ b/esphome/components/entity_transport/entity_transport.h
@@ -1,6 +1,5 @@
 #pragma once
 
-#include <memory>
 #include <span>
 
 #include "esphome/components/packet_interface/packet_interface.h"
@@ -130,7 +129,7 @@ class EntityTransport : public Component {
       remote_binary_sensors_;
 #endif
   // Packets are built here, allocated in setup()
-  std::unique_ptr<uint8_t[]> buffer_;
+  uint8_t *buffer_{nullptr};
   size_t max_packet_size_{0};
   uint32_t update_interval_ms_{0};
   uint32_t remote_timeout_ms_{0};