How does Invisibility work if you cast it while observed?

Question

In PF2, undetected and hidden are distinct conditions. A literal reading of the invisibility spell suggests that, upon casting the spell, the caster automatically becomes undetected.

Cloaked in illusion, the target becomes invisible. This makes it undetected to all creatures, though the creatures can attempt to find the target, making it hidden to them instead.

If the caster is undetected, then other creatures can attempt to find them by taking the seek action on their turns.

However, the rules for being invisible seem to contradict this:

If you become invisible while someone can already see you, you start out hidden to the observer (instead of undetected) until you successfully Sneak.

Suppose a spellcaster is being observed, and they cast invisibility. Do they become undetected, or do they become hidden?

If they want to become undetected, would they need to use an action to Sneak after turning invisible?

Answer 1

The target becomes Hidden

I noticed this notch in the rules as well. It becomes a question of specific vs. general where the spell would usually win out. Fortunately, the first section of the Invisibility 'General' Rules helps clarify.

A creature with the invisible condition (by way of an invisibility spell or invisibility potion, for example) is automatically undetected to any creatures relying on sight as their only precise sense. Precise senses other than sight ignore the invisible condition.

You can use the Seek basic action to attempt to figure out an invisible creature’s location, making it instead only hidden from you. This lasts until the invisible creature successfully uses Sneak to become undetected again. If you’re already observing a creature when it becomes invisible, it starts out hidden, since you know where it was when it became invisible, though it can then Sneak to become undetected.

It references the spell specifically, indicating that the rules therein apply and are actually more specific.

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The same seems to be true of the ability to make an invisible creature or object observed, seen here and here.

Other effects might make an invisible creature hidden or even observed but concealed. For instance, if you were tracking an invisible creature’s footprints through the snow, the footprints would make it hidden. Similarly, throwing a net over an invisible creature would make it observed but concealed for as long as the net is on the creature.

You can’t become observed while invisible except via special abilities or magic.