When does Viktor - Innovator's ability trigger and resolve when casting a spell during an opponent's turn?

Ruling: "When you play" triggers occur after the spell resolves, and the trigger goes onto the chain as a triggered ability that allows responses before it resolves.

Sequence:

• Cast the spell (e.g., Stupefy)
• The spell resolves
• Viktor's "when you play" trigger goes onto the chain
• Players can respond to the trigger
• When the trigger resolves, play the 1-might recruit token to your base

Nuances:

• The trigger can occur mid-chain if the spell that triggered it resolves while other items are still on the chain
• If the spell is countered, the "when you play" trigger never occurs because countered spells are not played