Entities Collide with fix-climbing-bypassing-cramming-rule Enabled

[diegogarciarojo]

Expected behavior

When the fix-climbing-bypassing-cramming-rule: true option is enabled, entities should not collide with each other, similar to vanilla Minecraft behavior. The cramming rule should still function to kill entities when there are too many in a confined space, without causing collision issues.

Entities should not collide, like in vanilla, with cramming rule killing excess entities instead.

Entities in scaffolds collide and push each other with fix-climbing-bypassing-cramming-rule: true enabled.

Observed/Actual behavior

With fix-climbing-bypassing-cramming-rule: true enabled, entities now collide with each other, which is not the intended behavior. This collision should not occur, as it deviates from vanilla mechanics where entities do not collide under these conditions.

Steps/models to reproduce

1. Set up a PaperMC server with the latest version.
2. Enable fix-climbing-bypassing-cramming-rule: true in the configuration.
3. Place multiple entities (e.g., animals or mobs) within a confined space, such as the structure shown in the image (allays in scaffold).
4. Observe that entities collide with each other instead of passing through or being killed by the cramming rule without collision.

Plugin and Datapack List

• No additional plugins or datapacks are used that affect entity collision or cramming rules.

Paper version

[19:45:35] [ServerMain/INFO]: [bootstrap] Loading Paper 1.21.4-232-ver/1.21.4@12d8fe0 (2025-06-09T10:15:42Z) for Minecraft 1.21.4

Other

• The issue is observed in a custom structure designed to test entity cramming, as depicted in the provided image.
• The collision behavior was tested with multiple entity types (e.g., chickens, allays) and consistently resulted in unwanted collisions.
• This behavior disrupts gameplay mechanics that rely on vanilla cramming rules without entity collisions.

[Axyss]

pls fix, any news?

It's being worked on. Check #12793

[MC-XiaoHei]

Hello, any updates? #12793 latest update at almost two months ago

[diegogarciarojo]

Yeah, any updates?

[Huge-mistake]

Half a year has passed, and the issue still hasn’t been fixed. What on earth is going on with Paper? Is there any team member available to spare some time reviewing the relevant PR?😢

[electronicboy]

Approved it, this was fairly low down on the list vs everything else being worked upon, the branch might be frozen due to the work preparing for the update, however;