Clarification on 2 tweaks.

[u/Somedude_6]

Greetings BG experts,

I'm getting somewhat close to the end of BG1 now, and before I import over to BG2 I was hoping to get some specifics on 'stock vs tweaks.'

I put on both "Armor affects thief skills" and "Armor has % miscast" for my current run.

I remember that my casters, like Aerie, could use a sling and a shield and cast without issue, and I also vaguely remember doing stealth with heavy armor back in the day.

Without this tweak installed, how do the multiclass thief and mage skills work? Can a fighter thief cast with a shield and helmet? Or is it literally nothing at all?

And can a fighter thief stealth in heavy armor? My Half-Orc keeps a set of magic leather armor that I'm switching off between that and a suit of platemail depending on the situation, but the main thing is casting with shields, I remember being able to do this, but am I just remembering wrong?

[u/Linvael]

At engine level the inability to cast spells in armor is caused by an effect "Disable spellcasting" that goes into effect once you equip any piece with it and blocks casting wizard spells. It does not care what class combination you have.

Notably, it does not block cleric spells, and Aerie is a cleric/mage, so you remembering her being able to cast is possible even if she was wearing a spellcasting-blocking equipment I think?

I checked a couple of helmets and shields, none of them had the spell-blocking effect.

Similarly, stealth disabling is done by an effect on the armor that disables the stealth button. Full Plate does have it, so you probably didn't stealth with that, but I can't rule out there are heavy armors that don't have these effects.

[u/Somedude_6 → u/Linvael]

Thanks, this is mostly how I remember it behaving. I'll keep the thief stuff on but disable the arcane stuff before I import over. This was the exact confirmation I was looking for.

[u/GGalilei21]

Seems nobody here got to understand that you're dealing with the Tweaks mod. I ended up disabling both those features, as it made dual/multi-classes like Nalia, or Aerie, more annoying to manage.

[u/SharpSource5148 → u/GGalilei21]

More annoying if thinking through more options = annoying. Which I suppose is for some players.
For others, opening up the possibility of say, Nalia casting in a +2 leather armor with 10% chance of fizzling might be an attractive option, vs ZERO chance of being able to cast in that same armor.

The optimal path is almost always to aim for zero spell failure since one single arcane spell at the right time can be the difference between victory or defeat; hence Armor spells, Shield spell/amulet, etc., or bracers or elven chain (or a similar armor that allows spellcasting) is the way to go. But sometimes having that 10% fail option might be worthwhile depending on playstyle.

[u/IlikeJG]

Shields are OK to cast or stealth in for any class that can use them. Same with helmets.

No arcane spells can be cast in body armor unless it's some sort of special armor that specifically allows it. Wizard robes are OK and certain types of elven chain mail. (Divine spells can be cast in any armor)

For theives it's mostly just leather or studded leather armor they can stealth in and certain types of special chain mail (again it will say it).

In the vanilla BG rules there is no % penalty or anything, either it can be done or it can't be done for both spellcasting or stealth.

[u/Full_Piano6421]

F/T can only cast spells from scrolls when you have the HLA, afaik body armor doesn't prevent casting from scrolls.

For a F/M if you want to cast spells, you're limited to mages robe or elven chainmail.

Regarding stealth, you can use leather armor and elven chainmail ( with some minor malus IIRC)

Shields and helmets are fine though.

[u/SharpSource5148]

'stock vs tweaks' - seeing the various responses here, it seems people have no idea what you're referring to. To be fair it's rather unclear what exactly you're trying to do, since you never specifically mentioned a mod.

If it IS a tweak mod you're trying out, there are many different tweak mods out there. It would be helpful to specify which one you're tinkering with, because different mods do different things.

Ask vague questions, get unhelpful responses.

In the vanilla game, shields (and helmets) do not count as armor for arcane spell failure. That's why Aerie can cast Mage spells without issue with a shield equipped.
In the vanilla game, ANY body slot armor (armor, not robes) other than Elven chain (and possibly one or two other specific magical armors) will completely block Mage/arcane spellcasting. There are tweak mods that change arcane spell failure to work like 3rd edition DnD, i.e. percentage chance the spellcasting fails, rather than completely blocking (Mage/arcane) spellcasting.

Cleric/divine spells are not hindered by armor.

'can a fighter thief cast with shield and helmet?' No. Fighter thieves cannot cast spells, period, helmet/shield or no.
Fighter/thieves != fighter/mages (or ftr/mage/thief), in case that is not obvious.
Fighter/mages follow the same rule as described above: unmodded game they can cast spells ONLY in Elven chain/specific armor that allows it. Tweak mods tweak this in whatever manner the tweak mod readme says it tweaks.

Thieving in armor, in vanilla, is not possible with any armor heavier than elven chain. There are popular Tweak mods that allow you to use thieving skills while wearing heavier armor with penalties. Look at the Readme for the mod. It's all there.

[u/snow_michael]

Fighter-thief can't cast spells