Factorio Forums

Same issue as viewtopic.php?p=439933
It looks like the fix back then was just to disallow these upgrades in the planner, not actually preventing the bots to build the upgrade.
Selecting upgrades with different collision requirements is currently possible, so this might be a regression.

But expected behaviour would be that these upgrades are still allowed and bots just idle above the thing-to-upgrade like they do over a ghost-to-build that relies on ghost tiles below.

Full form bug report:

What did you do?
- Added small mod (attached, upgrug.zip), which modifies assembling-machine-3 placement conditions
- Try to replace assembling-machine-2 with assembling-machine-3 by hand and by bots
What happened?
- operation is not possible by hand (expected), but bots perform the operation without checks (unexpected)
What did you expect to happen instead? It might be obvious to you, but do it anyway!
- Bot with assembling-machine-3 in inventory floats over upgrade target without upgrading until tile requirements are met (like they do for ghosts)
Does it happen always, once, or sometimes?
- always

Bots cannot upgrade entities with different collision boxes, if you found a way for them to do that provide exact steps please, see 3638.

Loewchen wrote: Sun Feb 08, 2026 5:01 pm Bots cannot upgrade entities with different collision boxes, if you found a way for them to do that provide exact steps please, see 3638.

Updated my post.
The issue is not different collision boxes, but different collision masks tile_buildability_rules. i.e. like original bug said, upgrade is only placeable on water, but original is not. I can provide a simple modded setup to reproduce this, but since this is now in "Not a Bug" I guess I have to open a new thread for it?

This is reproducable with a mod containing this single line in data.lua:
data.raw["assembling-machine"]["assembling-machine-3"].tile_buildability_rules = { { area = {{ -1, -1 }, {1, 1}}, required_tiles = { layers = { resource = true } } } }

This makes AM 3 to no longer be placeable by hand, but it will still be a valid upgrade for AM 2 in the upgrade planner and bots will happily perform that upgrade.

Thanks for the report. To be consistent with collision boxes, we could disable upgrade option for entities which have different tile buildability rules. I'm not sure if this would be desired in your case.

Equally related, build a normal offshore pump, land-fill it, Now you can't place a higher quality version by hand, but a bot can still place it via an upgrade planner, and this alone ignores tile buildability rules.