When playing Tideturner from hidden with Gemcrafter Seer's vision trigger, if you stack vision first and see/play a Nocturne, can Tideturner swap with that Nocturne?

Ruling: No, Tideturner cannot swap with Nocturne in this scenario. You must decide targets for a trigger when it goes on the chain, and since Nocturne isn't on the board at that time, it cannot be selected as a swap target.

Sequence:

• When Tideturner is played, both its swap ability and Gemcrafter Seer's vision trigger go on the chain
• You can choose the order these triggers go on the chain (you control both)
• Tideturner's swap ability must select its target when it goes on the chain
• Even if vision resolves first and plays Nocturne, Tideturner has already locked in its target (or lack thereof) before Nocturne enters play