Dwarf Fortress Bug Tracker - Dwarf Fortress
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0011711Dwarf FortressPathfindingpublic2021-03-04 08:322021-03-11 09:37
0011711: Forgotten Beast in flooded cavern ignores path into fortress, prefers to wander aimlessly
Whenever FBs enter the map on dry land they usually head straight towards my fortress, but if they appear in a flooded cavern layer then they seem content to wander around and ignore any paths I provide. The same issue was present in 47.04 and I also remember it happening with a flying FB in a flooded cavern.

I can't guarantee that it's 100% reproducible, but it's 2/2 for FBs in this save and I've seen it happen many times before.

Note that the FB will still chase and attack any cavern wildlife which gets too close, so it's not totally unable to path through water.
1. Embark somewhere where one of the cavern layers is mostly flooded.
2. Wait for an FB to show up in that cavern.
3. Give them a path into your fortress which requires them to path through water.
Save: https://dffd.bay12games.com/file.php?id=15454 [^]
The FB causing problems is called "Dirlu Ngethacthefin Ewomamsir Usu" and its symbol is a grey N. It should be in view when you first load the save. It's to the north in the first cavern layer (hotkey Shift+F1).
To verify the path into the fortress start at the FB holding cells (hotkey F6) just below the first cavern layer. You can then trace the path from the main stairwell, through one of the holding cells, up the narrow stairwell to the east, along a corridor and down through a floor hatch into onto a piece of dry ground in the first cavern layer. None of the doors/hatches are locked.
I've also included errorlog.txt in the save above.
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Issue History
2021-03-04 08:32Moeteru62New Issue
2021-03-11 09:37Moeteru62Note Added: 0040971

2021-03-11 09:37   
It's definitely an issue with pathfinding through water. I waited until the FB randomly wandered onto the patch of dry ground and then opened the bridge again. Once it no longer had to path through water it immediately made a bee-line for my fort, allowing me to catch it.

If I had to guess I'd say that the invader AI used to attack the fort is restricted by the same pathing rules as dwarves, even if the creature is amphibious.