Spellcraft, Detect Magic, and Illusions

[Tor the Fallen]

For myself, I rule the following:

The attempt at detecting magic counts as an attempt at disbelief. If the detector fails their saving throw, the illusion supercedes the detection ability and it radiates whatever the illusion-caster says it does.

Spellcraft works differently. You have to believe or have proof that something is magical to use Spellcraft on it. If you cannot identify an effect you cannot use Spellcraft.

But spellcraft occurs automatically. It's like being able to sense magic is there, because you know what its signs are. Just like an elf gets to role a search check for a hidden door, even if it doesn't know there's a door there.

I mean, if it doesn't require an action to do, there's no reason why a caster can't say- "i'm making spellcraft checks constantly," as it literally takes no time.

[edit]
Maybe a spellcraft check first, and if that succeeds, then they get a will save?