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.
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