If my opponent plays a vanilla unit (permanent), do I have a chance to play a reaction before it resolves?

Ruling: No, you do not have a chance to play a reaction before a vanilla unit resolves. When a permanent starts a chain, it enters the chain and immediately resolves with no priority windows for reactions.

Sequence:

• Opponent plays a vanilla unit (permanent)
• The permanent enters the chain
• The permanent immediately resolves off the chain
• No reaction windows are provided

Nuances:

• You also do not get a reaction window after the permanent resolves
• A vanilla unit gives you exactly 0 windows to react