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I notice that forge auto pays for the spell or activated ability that I intend to cast, which means that I can't get the KCI multi sacrificing working, 'cause I just can't generate more mana than the spell or ability actually needs.
forge just automatically pays for the spell or ability when I tap lands or activating other mana abilities and automatically put the spell or ability on stack onec the generated mana is sufficient.
Is this a problem and can it be fixed? Or am I missing some setting that can bypass this issue?
Im fresh to forge and I love the idea that you can try all kinds of decks in it. Please help me with this, thanks dudes.

Yea, Forge doesn't do the ordering for paying costs 100% correctly. We already have an issue to track this, but it's a fairly big rewrite to fix.

https://git.cardforge.org/core-develope ... issues/391

Basically when you are activating abilities/casting spells you have a time to activate mana abilities before you start paying costs. We lump together the "activate mana" and "pay mana cost" portions for simplicity.