Ghasts don't aggro unless you're at the exact same height they are flying

Really? It's not working with me... Still have to be at eye level with them.

When I summon them (at a different height) they attack me but when I go to the Nether they don't see me.

I tried it with /summon and with a spawn egg, and they didn't work. Neither did naturally spawning. Spawn a zombie, then stack about 6-10 blocks high, then go into survival, it won't see you. Other mobs have this problem, it could be linked with that.

Confirmed in 14w29b. I just noticed this bug while playing survival. There's a ghast in the nether pretty close above me who hasn't noticed me, with no obstacles anywhere between us (big, open cavern).

I've noticed ghasts are more accurate now. But they can't hit the player if they can't see them!

This may be the most serious of the mob AI quirks, and it's still in the pre-release. The second would be endermen not turning peaceful when in water.

You have to create a new issue for the endermans.

Because other mobs have this bug too the tittle of this issue is wrong but that is your choice.

Ghasts are most badly effected. I guess you're right though, but ghasts should most definitely not be effected.

You have forgot how to reproduce this bug. You can write it in some steps like:
1. Go in survival.
2. Do /summon Ghast ~ ~20 ~

It's pretty self explanatory, but I'll add it.

I don't see that you have added it. But take your time. They will notice this later 🙂

I have made a video of it. I can't post it as an attach file.
http://youtu.be/RiuyR4qSwT0

Facepalm Ghasts' AI has been slightly changed. They cannot see the player unless their hight comes to almost eye level with the player, which is possibly a bug. When attacking, ghasts will now turn their whole body to face the player's direction, and repeatedly strafe left to right around the player while attacking. They now have perfect accuracy with their fireballs, shooting at the player's head, compared to earlier versions when the fireball was previously aimed slightly above the player's head.

http://minecraft.gamepedia.com/Ghast#History

This is no bug anymore... they have changed it.

Heh, funny thing about that. I just became a minecraft wiki editor, due to seeing how terribly outdated the mob articles are, and I have changed some things in the mob articles to include new AI and bugs. Look at the newly refreshed spider "Behavior" section. That one you quoted is a whole section I wrote in the "History," thanks for pointing it out. I said it is possibly a bug, which is true since it is confirmed now. Or at least marked "community consensus." So yes, it is still a bug, I wrote something similar in the blaze's History section.

Confirmed for 1.8.2-pre1. If the ghast sees you first then flies above you, it still attacks; however if you walk under it and it hasn't seen you before it doesn't attack until at the same height.

Confirmed for 1.8.7.

Confirmed for 1.8.8.

Still in 1.9

Confirmed for 1.12.

Confirmed for 18w30b

Confirmed for 1.13.1.

Confirmed for 1.13.2 and 19w09a

Is this still the case in 1.14+? The mob AI was altered to focus on eye visibility.

Tested in 1.14.4 They only aggro if you're on the same level, but once they're aggressive they'll shoot you from any height

Can confirm in 1.15-pre1

Noticed in 1.15.1. It does appear to revolve around same height. They don't even attack if attacked. Once you get to the same height and they notice you, they seem fine.

Confirmed in 20w09a

It has to do with chunks too

Once I teleported to nether and spawned in soul soil valley biome, where too many ghasts spawn

They all were ignoring me, I used f3+b to see chunks' boarder and when i entered a new chunk they all attacked me at once!

The code in net.minecraft.entity.mob.GhastEntity.initGoals() (based on Yarn 20w13b mappings) seems to explicitly limit the height difference to 4 blocks, which suggests that this behavior might be intentional:

protected void initGoals() {
        ...
        this.targetSelector.add(1, new FollowTargetGoal<>(this, PlayerEntity.class, 10, true, false, livingEntity -> Math.abs(livingEntity.getY() - this.getY()) <= 4.0));
    }

If this is intentional, I hope they undo it. I remember when you would go to the Nether and you HAD to keep an eye out for Ghasts. Now, if I see them, I don’t think much about them. This bug or change really seems to make the Nether too safe. It’s supposed to be a rough place. I hope they fix/change this soon.

I hope it will be fixed before Nether Update.

If it's intentional, can it be at least linked to the difficulty, for example fixing it for hard difficulty? I really miss more challenges in the game and this seems like a big killer of fun for players who like the excitement of adventure.

Connecting it to difficulty seems like a good idea. I was making a PVE type map and ghasts are an enemy. However, due to this issue, I’ve postponed adding them as they are currently useless. They just fly around and let you hit them. Also, can they please attack back if attacked? Currently, if you attack them, they don’t react. This change would at least somewhat make them more difficult.