How long does Stun last? Does it wear off at the beginning of the stunned unit's controller's Ending Step, or at the beginning of the very next Ending Step (which would be the active player's Ending Step)?

Ruling: Stun lasts until the beginning of the next Ending Step that occurs in the game, which is the active player's (the player who applied the stun) Ending Step. This means a stunned unit becomes unstunned during the same turn it was stunned.

Nuances:

• ChatGPT's interpretation that stun lasts until the stunned unit's controller's Ending Step is incorrect
• While stun may feel weak with this timing, it still provides value by allowing safe attacks into stunned units (taking no damage back) or causing attacking stunned units to be recalled without dealing damage