How does priority work when reactions are stacked in a showdown, and who can react as the chain resolves?

Ruling: As each item on the chain resolves, there is another round of priority for players to react. The player who controls the next item on the chain after an item resolves gets priority first, then they can play a reaction or pass priority to the next player in turn order. When all players pass in succession, the topmost item resolves and the process repeats.

Sequence:

• Player 1 (with Focus) stacks reactions 1, 2, 3 and passes priority
• Player 2 can respond to any item on the chain (e.g., Defy targeting reaction 2)
• When all players pass, the topmost item begins to resolve
• As each item resolves, the player controlling the next item on the chain gets priority first
• Players can add new items to the chain at each pause
• When all players choose not to respond, the topmost item resolves
• This repeats until the chain is empty

Nuances:

• Focus is specifically for playing cards/activating abilities during a showdown when nothing is on the chain; it doesn't affect priority or the chain itself directly
• Focus swaps when the chain fully resolves in a showdown, or when a player chooses to pass focus rather than start a new chain
• Defy can target any item on the chain when it's being finalized except for itself