In Minecraft Java snapshots 25w36a and the follow-up 25w36b mannequins (the newly introduced minecraft:mannequin entity) ignore the NoAI:1b NBT flag. Even when summoned with that tag mannequins behave as if they have AI.
How to reproduce:/summon minecraft:mannequin ~ ~ ~ {NoAI:1b}
Expected behavior:
The mannequin should remain completely static and not move.
Actual behavior:
The mannequin still shows AI-like behavior and movement despite having NoAI:1b.
The Invulnerable NBT seems to be working as expected, mannequins do not take damage when hit by players in survival or adventure mode. As for the NoAI tag, I can confirm that the entity takes knockback, unlike other mobs with NoAI.