My basic question here is thus: Will a character with multiple detection spells be able to see, say, a monofilament tripwire linked to a couple bouquets of flashbangs hidden in the walls? I don't want him to be able to literally see everything at once, because it'd make any attempt at traps and sneaky GM stuff entirely pointless, and I don't have the urge to just GM fiat every last little trap. Any ideas?

Monofilament wire is, itself, a trap. It's more likely to slice someone in half than ever put enough tension on the flashbang's pin to get them to go off.

Oh. Well, would a very fine, thin wire work? I essentially want to try tricking him into walking down a seemingly abandoned hallway rather than risk fighting a group of life-forms (actually wage slaves working late) and get flash-banged, before security comes after him.

Fishing line is great for that kind of stuff.

As for the spell Detect Traps...he'd still have to roll a perception check.

So he /doesn't/ just "see everything around him like it's a map"?

What are the limits of the spells? What should I make him roll a perception test for? Do the spells add their rating to it?

I don't have the details of that spell in front of me, so I can't answer specifics.

But as for rolling perception test, you ask him to "Roll a perception test." Then based off how many hits you got, you tell him what he noticed (there's a section in the book on Perception).

I don't think so. You could spot it anyway without the spell.

That the spell does is an opposed roll based on the object resistance of the trap. You would have to dream up what the object resistance of a fishing line grenade trap is. For example, grenades are technically devices so they could be 15, but fishing line is pretty low tech, maybe 1 or 2. I'd probably split the difference at 8.

So roll 8 die vs whatever the spell specifies is rolled by the caster. I can't remember if it is spellcasting or some stat combo with a limit of the force of the detection spell.

Like everything in Shadowrun these spells use reverse descriptive logic. Active spells, such as detect objects (which you would use for traps) automatically detects things that enter the area of the spell, where passive detection spells still rely on preception tests. This can be confusing because in gaming terms passive tends to mean automatic (like those blasted direct, indirect definitions).

You could argue perhaps that detect 'Traps' is too broad a usage of the spell, but ultimately that's up to you. I could see a player arguing that Traps is about as broad as say, computers or guns.