Casting time and counterspell

[Selion]

How do counterspell rules interact with spells with a casting time longer than a standard action?
E.g. an enemy spellcaster uses a summoning spell which has a casting time of 1 round. Do i roll to recognize it immediately or do i have to wait for the spell completion?
Can i try to counterspell it the second round? Let's say:
Enemy turn: summon monster
My turn: i ready an action to counterspell
Enemy turn: summon monster spell is completed

[upho]

Your readied action is triggered by the enemy starting to cast, ie the moment the enemy initiates the required action. The casting time of the enemy's spell is irrelevant.

[Selion]

Your readied action is triggered by the enemy starting to cast, ie the moment the enemy initiates the required action. The casting time of the enemy's spell is irrelevant.

It seems right, and It's even good on a balance perspective to prevent some spells to be outright useless, but it's strange there's not an explicit statement in the rules.
What happen if i suddenly enter in a room with a cleric is in the middle of a commune spell (10 minutes casting time), inside a force cage? It sounds strange that i cannot try to stop the spell because i wasn't ready the very first instant of a time span of 10 minutes, but i guess that it's how the game works.

[Techwarrior]

You can still interrupt the cleric's casting. Break his concentration with a souped up Orb or something.

Alternatively, get the fighter to hit it. That's like their one job.

[upho]

What happen if i suddenly enter in a room with a cleric is in the middle of a commune spell (10 minutes casting time), inside a force cage? It sounds strange that i cannot try to stop the spell because i wasn't ready the very first instant of a time span of 10 minutes, but i guess that it's how the game works.I don't think it's very strange at all, actually, as counterspell says:

"you must select an opponent as the target of the counterspell. You do this by choosing the ready action."

Which means counterspelling doesn't simply ready you to counter any spell from any source, but only those specifically cast by the selected target. You're basically keeping the target under close watch to react the moment the target starts casting, which isn't exactly possible when if you "suddenly enter in a room with a cleric is in the middle of a commune spell". I hope that makes the verisimilitude more sensible.

And from a balance perspective, as Techwarrior mentioned, long casting times are a huge disadvantage in combat anyways, as the caster can be easily interrupted in so many other ways (most of them much more effective and less costly than counterspelling). Casting times beyond 1-round are typically "Combat: No" (without very effective defenses already in place), and even 1-round times are of course much more risky than anything you start and finish during the same turn.

EDIT: The same is btw true for other triggered immediate actions and AoOs; they happen the moment the trigger starts. Which for example means that an AoO triggered by moving can happen in the square where the move action was taken, and if for example used to trip the target the AoO can therefore often halt the movement and completely void the action before the target was able to move any distance at all. These things are unfortunately not very clearly explained in the core rules. /EDIT

[Psyren]

I'd rule that you can attempt to counterspell anytime before the spell goes off. This includes walking in on a casting in progress. But I don't think it's clearly stated anywhere.

[Lord of Shadows]

This might help, I hope I've got it right:

Phases of Counterspelling
A Caster is opposed by one or more enemies who can cast spells.
That Caster decides to Counterspell and declares a Ready Action to Counterspell a specific enemy target. (Declaring a Ready Action is a Standard Action, allowing the Counterspeller only a Move Action that turn)
On that specific enemy target's next turn, they begin casting a spell. This triggers the Counterspeller's Readied Action and the Counterspeller gets a Spellcraft check (DC = 15 + level of spell being cast) as a Free Action to both detect the casting and identify the spell being cast.

-Spellcraft in 3.x specifies that you, "must see or hear the spell’s verbal or somatic components."


-Spellcraft in Pathfinder specifies that you, "must be able to clearly see the spell as it is being cast, and this incurs the same penalties as a Perception skill check due to distance, poor conditions, and other factors."



-Neither allows a Retry.
If your Spellcraft check succeeds, you may attempt to complete the Counterspell action. Proceed to the next step. If your Spellcraft check fails, your Readied Action ends.
To complete the Counterspell action, both 3.x and Pathfinder require you to cast a spell as a Counterspell. Their wording is slightly different, but both state that if you cast the same spell that you are countering, and the other caster is within the range of your spell, the spells cancel each other.

- In 3.x it states, "If you are able to cast the same spell and you have it prepared (if you prepare spells), you cast it, altering it slightly to create a counterspell effect."


- In Pathfinder it states, "If you are able to cast the same spell and you have it prepared (or have a slot of the appropriate level available), you cast it, creating a counterspell effect."
If you do not have the same spell available, you can also attempt to use a Dispel Magic as a Counterspell, which succeeds or fails based on a caster level check (D20 + your caster level vs. a DC of 11 + the opposing caster's level). Using Dispel Magic as a counterspell does not require a Spellcraft check, but may require a Perception check as a free action to detect your target beginning to cast a spell.
Casting Time
If the Counterspell process works normally, both casters will be casting the same spell at the same time, and Casting Time will not be relevant to them. It still might be relevant if another character is able to affect the target of the counterspell before they finish casting. If the counterspell target's casting is disrupted, the Counterspeller's spell will still go off, but is not likely to do anything due to the "counterspell effect" language above.

One case where straight up casting time could be important is if the target of the counterspell has a shorter casting time than the counterspell caster. If the Counterspeller does not have access to the spell being countered (i.e. a Cleric trying to counter a Sor/Wiz only spell, like Featherfall), and must use Dispel Magic, it is possible that the target caster could complete their spell before the counterspeller.

As far as Metamagic Feats like Quicken Spell are concerned, both 3.x and Pathfinder specify that, "Whether or not a spell has been enhanced by a metamagic feat does not affect its vulnerability to counterspelling or its ability to counterspell another spell." This doesn't explain exactly what happens with a Quickened Spell, other than to imply it can be countered just like the same spell cast normally.

The rules seem to imply that any spell can be countered at any time, but are severely lacking in details, which will likely have to be decided by the table/DM.

This topic has come up before here (http://www.giantitp.com/forums/showthread.php?31980-Can-a-quickened-spell-be-countered) (short...) and here (http://www.giantitp.com/forums/showthread.php?436564-Can-you-dispel-a-spell-whose-casting-time-is-instantaneous) (a little better...). There may be others as well. One poster in that 2nd link had some good ideas:


You have four chief strategies to pursue:

* Deny your opponent the ability to know you are casting a spell. For example, if you are invisible and your spell has no verbal components, no one will know you are casting.
* Render your spell difficult to counter by increasing its effective spell level and/or caster level so that more resources are required to counter it. This is difficult and expensive.
* Use deception and teamwork to render the counterspeller unable to counter you. For example, if the fighter tackles him, he may be unable to cast. If you delay to time your action with an allied spellcaster and you both cast at once, the enemy can only counter one of you. If you cast more than one spell per round, the opponent may be unable to counter both of them. If the countercaster is unable to identify your spell correctly (say, you use a skill trick to disguise the casting) he may think it is a low-threat spell and elect not to counter it.
* Pre-cast your spells. Long-duration buffs cast before you enter the combat zone can't be countered (although they can be dispelled).

Errata...
Supplements, splat books, etc all offer a host of options that can affect counterspelling in one way or another. YMMV...

Hope this helps...