This event is fired directly before vanilla brewing takes place, and, if cancelled, will prevent brewing from taking place. If cancelled but the items are modified, then the PotionBrewPostEvent will be automatically fired. This allows for a simulacrum of "modded" brewing.

Note: this event is fired right as the calculations for the recipe are taking place, when the "timer" reaches "maximum progress".

You will need to cast the event in the function header as this class:
crafttweaker.event.PotionBrewPreEvent You can, of course, also import the class before and use that name then.

Event interface extensions

Link to event-interface-extensions

PotionBrewPre Events implement the following interfaces and are able to call all of their methods/getters/setters as well: