Does Gaea's Cradle produce mana based on creatures at the time you tap it or when the mana ability resolves?

Gaea's Cradle reads: '{T}: Add {G} for each creature you control.' This is a mana ability, and like all abilities, its effects are determined when it resolves, not when it is activated. The number of creatures you control is counted at the moment the mana ability resolves and produces mana.

Under CR 605.3, mana abilities resolve immediately when activated — they don't use the stack in the normal sense, so there's virtually no window for the creature count to change between activation and resolution in normal gameplay. However, the count is still technically evaluated on resolution per CR 608.2b, which instructs effects to check the game state at the time they apply.

In practice, because mana abilities resolve immediately without using the stack (CR 605.3a), no player can respond to change the creature count before the mana is produced. This means the result is functionally the same as checking at activation time in almost every real game situation.

Concrete example: You control 4 creatures and tap Gaea's Cradle. The mana ability resolves immediately and you get {G}{G}{G}{G}. No opponent can cast a removal spell in response to reduce that count, because mana abilities don't use the stack and cannot be responded to.

The rare edge case where timing matters would be something like a replacement effect or a triggered ability that fires during mana production itself — but for standard play, tapping Gaea's Cradle always counts creatures at that same instant of resolution.