Curios API Forge

First Forge release — a port of Curios API 9.5.1 from NeoForge to Forge 52.1.x on Minecraft 1.21.1.

Port

• Rebuilt the platform layer for Forge: capabilities, networking, configs, events and screen registration.
• Mixin configs are now declared through the MixinConfigs manifest attribute.
• Slot conditions in datapacks accept both forge:condition and neoforge:conditions, so existing NeoForge datapacks work unchanged.
• JEI integration kept; EMI and REI integrations removed (no Forge 1.21.1 builds available).

Fixes

• Items no longer disappear when loading a curio inventory with an occupied slot — they are returned to the owner.
• Cosmetic items are no longer destroyed when slots are removed or resized.
• Fixed Enderman anger checks ignoring the player's mask for the rest of the tick.
• Fixed NPE in CurioSlot#isActiveState for slots without active states.
• Fixed wrong NBT node used for Size in CurioStacksHandler#deserializeNBT.
• Fixed client disconnects ("Curios Networking Failure") caused by out-of-range slot indices.
• Hardened server-side packet checks: CPacketDestroy is creative-only, render toggles reject invalid slots.
• Fixed findCurios leaking its cached list; empty cache keys are no longer stored.
• Fixed show_in_tooltip being ignored for curios:attribute_modifiers.
• CurioCanUnequipEvent#getUnequipResult no longer returns null (defaults to DEFAULT).
• Made the predicate registry and SlotAttribute cache thread-safe.
• Fixed "+N slots" tooltip selection and non-deterministic slot order.
• Fixed itemCacheKey containing Optional[...].
• Fixed the test advancement path for 1.21 (advancements → advancement).

Notes

• Requires Minecraft 1.21.1 and Forge 52.1.0+.
• No content changes compared to upstream 9.5.1.
• Original Curios API by C4 (TheIllusiveC4); Forge port and maintenance by Fitals.
• License: MIT.