I got the SpoilToTriggerResult approach running. The script only gets the containing entity, so I'm checking every inventory in the entity for relevant items to perform item replacement, but there's a couple problems.

First, while the script-based item swap works fine in normal inventories, in a ...

Interesting. It looks like a spoilage quality can be specified, but that appears absolute, not relative to the source item.
Is the trigger idea using the SpoilToTriggerResult api? I'll have to experiment; the use of a trigger sounds fairly performant, but I worry that dummy items would break pedia ...

I'm trying to find a way to make a recipe with ingredients of quality n yield a result of quality n+1 . The recipe prototypes don't supply this natively, so I'm trying to find a code-based solution. I've run into a few obstacles, though.
* I don't see an event for when crafting machines get assigned ...