There are A LOT, mostly due to Mojang breaking networking AGAIN.
The following deprecated APIs were removed:
fabric-containers-v0(deprecated since 2020), usefabric-screen-handler-api-v1ScreenRegistryandScreenHandlerRegistry, use TAW
The following were deprecated:
FabricBlockSettings(use regularAbstractBlock.Settings)FabricItemSettings(same; custom APIs available via interface injection ofFabricItem PERIOD Settings)
CustomDamageHandler callback's signature was changed from ItemStack stack, int amount, LivingEntity entity, Consumer breakCallback to ItemStack stack, int amount, LivingEntity entity, EquipmentSlot slot, Runnable breakCallback. Additionally, calling breakCallback now ignores the return value and vanilla damage handler (as the item is already broken).
FabricParticleTypes#complex now requires passing Codec and PacketCodec. You still need to pass Factory, which is used for commands.
CustomIngredientSerializer#read and write were removed and replaced with getPacketCodec.
ExtendedScreenHandlerType no longer uses raw PacketByteBuf; instead you create a custom data object and pass a PacketCodec in its constructor to serialize the payload. create similarly no longer takes PacketByteBuf, instead the custom data object. ExtendedScreenHandlerFactory#writeScreenOpeningData was replaced with getScreenOpeningData, which receives only the player as the argument, and returns the data object.
TODO