Do cleanups happen during the resolution of a spell or ability, or only after the entire spell/ability has finished resolving?

Ruling: Cleanups do not happen during the resolution of a spell or ability. The entire spell or ability must finish resolving completely before any cleanup occurs.

Sequence:

• Begin resolving the spell or ability
• Execute all effects of the spell/ability in their entirety (including all moves, damage, status changes, etc.)
• The spell/ability finishes resolving and is removed from the chain
• Cleanup occurs

Nuances:

• This prevents cards like Zhonya's Hourglass from killing a unit twice (once after the replacement effect, then again before the heal)
• For Tideturner, both moves complete before any cleanup happens, so you don't lose control of a battlefield mid-resolution
• When cards need a cleanup to happen between steps, they use reflexive triggers (like Lee Sin's spell)
• Passives are always active, but their consequences are only checked during cleanup
• This interpretation prevents numerous game-breaking interactions and is consistent with how other TCGs handle similar timing