The USE_ESP_IDF C++ define and related Python APIs are deprecated. Since Arduino-ESP32 is built on ESP-IDF, all IDF APIs are available on ESP32 regardless of framework selection.
This is a breaking change for external components in ESPHome 2026.1.0 and later.
The light component's callback system has been refactored to use a listener interface pattern with lazy allocation. This replaces the previous CallbackManager<void()> approach with explicit listener interfaces that only allocate memory when callbacks are actually registered.
This is a breaking change for external components that register light state callbacks in ESPHome 2025.12.0 and later.
The network::get_use_address() function has been optimized to return const char* instead of const std::string& to reduce memory overhead. This eliminates unnecessary string object storage when accessing the device's network address.
This is a breaking change for external components that call network::get_use_address() in ESPHome 2025.11.0 and later.
ESPHome 2025.11.0 introduces significant memory optimizations to the Climate entity class that affect external components implementing custom climate devices.
ESPHome 2025.11.0 introduces memory optimizations to the Event entity class that reduce heap usage and store event type strings in flash. These changes affect external components implementing custom event devices.
ESPHome 2025.11.0 introduces a memory optimization to the Fan entity class that also changes how preset modes are ordered. This affects external components implementing custom fan devices and may change the display order of preset modes in Home Assistant.
ESPHome 2025.11.0 introduces memory optimizations to the Light entity class that reduce both heap and flash usage. These changes affect external components implementing custom light devices and effects.
ESPHome 2025.11.0 introduces significant optimizations to the Select entity class that reduce memory usage and improve performance. These changes affect external components that implement custom select entities.
The core automation framework (actions, triggers, and conditions) has been optimized to use const references instead of pass-by-value for parameter passing. This reduces memory allocations by 83% in the automation execution path.
This is a breaking change for external components with custom actions or conditions in ESPHome 2025.11.0 and later.
At the beginning of this year, we made the transition from IDF 4.4 to IDF 5.1; this was a major upgrade and many changes were necessary within ESPHome to achieve this.