Runtime Recipe Modification

Current API Minecraft 1.21.1 / MBD2 21.1.1

MBDMachineEvents.onBeforeRecipeModify('example:crusher', wrapper => {
  const event = wrapper.event
  const upgrades = event.machine.getTraitByName('speed_upgrades')
  if (upgrades === null) return

  const count = upgrades.storage.getStackInSlot(0).count
  if (count <= 0) return

  const builder = event.recipe.toBuilder()
  builder.duration(Math.max(20, Math.ceil(event.recipe.duration * (1 - count * 0.1))))
  event.setRecipe(builder.buildMBDRecipe())
})

Read event.recipe, copy it with toBuilder(), modify the builder, and assign the new MBDRecipe back. Never mutate the shared registry recipe. onBeforeRecipeModify is cancellable; use onAfterRecipeModify to observe the final copy.