Bevy 0.20

Bevy 0.20 is a major engine release (227 contributors, 817 PRs) that adds large rendering, scene, and UI improvements plus many ergonomics and performance tweaks. The realtime pathtraced renderer Solari gained higher-quality, mostly unbiased lighting via ReSTIR improvements, reduced CPU costs through retained scene management, macOS/Metal support, and updated DLSS-RR 4.5 support; ReSTIR is now optional and disabled by default to favor performance. Bevy adopted WESL as the shader language, added sprite custom materials and extended 2D materials, introduced a pan-orbit camera, and improved mesh-shader and shader toolchain compatibility. The release also includes texture compression improvements and better DLSS integration (update the DLSS SDK to compile).

Scene authoring and UX saw big wins: BSN scene syntax was simplified with explicit @ prefixes, removal of template_value wrappers, better enum handling, chained-method support, and cleaner list separators to reduce noise. A new Ready event fires after an entity and its descendants finish spawning, enabling bottom-up initialization. Feathers UI gained many widgets (color input, scrollable list, dropdowns, draggable number input, headless tabs), and runtime/engine improvements include weak system ordering via chain_weak, contextual theming, per-column change ticks, FixedNode and elliptical border radius support, schedule randomization, panic catching, faster bulk despawning, richer error context messages, and new InlineBox/InlineImage capabilities. Upgrade guidance and a 0.19→0.20 migration guide are provided.