Using a bucket, bottle, water potion, dyed armour, patterned banner or dyed shulker box on an empty, water, lava or powder snow cauldron follows CauldronInteractions, including the creative-mode stack rules of ItemUtils.createFilledResult and the underwater refusal for lava and powder snow. A harness runs every item against every cauldron state in vanilla's own useItemOn and compares the result, block writes, sounds, drops and inventory.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Ludovic Marie