When can hidden cards be revealed, particularly on an opponent's turn during neutral open state or when passing priority?

Ruling: Hidden cards can be revealed any time you have priority, just like reactions. On an opponent's turn during neutral open state, you do not gain priority through phase changes - only through chains being opened. If an opponent passes during an open state, their turn ends and you don't have a chance to respond unless this causes something to trigger.

Sequence:

• During your turn in neutral open state, you can reveal hidden cards as discretionary actions
• On opponent's turn, you can only reveal hidden cards when a chain is opened (giving you priority to react)
• If opponent passes during open state without opening a chain, their turn ends with no reaction window

Nuances:

• The temporary trick works: if a unit with temporary at a location with a hidden card is banished, you can react by flipping the hidden card because temporary creates a chain/trigger
• During showdowns, when opponent passes focus to you, you can play hidden cards even though it's not a neutral open state
• Phase changes alone do not grant priority to the non-turn player