Can you play reaction spells in the middle of a chain resolving, or only when reflexive triggers add to the chain?

Ruling: You can play reaction spells in the middle of a chain resolving. Each time an item on the chain resolves, priority passes to the player who controls the next item on the chain, and it must be passed again before the next item resolves.

Sequence:

• An item on the chain resolves
• Priority passes to the player who controls the next item on the chain
• Priority must be passed again before the next item resolves
• During this priority window, any player can play a reaction spell

Nuances:

• This is not limited to only when reflexive triggers add to the chain - reactions can be played at any point during chain resolution when priority is passed