Updating to the package to spine-unity-4.2-2024-07-19 breaks my IK script (it's basically just a modified SkeletonUtilityGroundConstraint.cs that supports more scenarios, e.g. reversing IK when climbing and arms reaching/hitting roof). If I downgrade to spine-unity-4.1-2024-06-19 then it works again.
If interested: I have a sample package/project using the version that works spine-unity-4.1-2024-06-19, so you can upgrade it and see for yourself. Let me know where I could send it (don't want to upload a bunch of Spine code here if not allowed to).
Custom IK no longer works since updating
It seems like the issue with your custom IK script might be related to changes in the spine-unity runtime between versions 4.1 and 4.2. To troubleshoot this, you can try the following steps:
- Re-import the spine-unity package: Ensure that you have a clean installation of the spine-unity-4.2-2024-07-19 package. Sometimes, issues arise from incomplete or corrupted imports.
- Check for changes in IKConstraints.cs: Since your custom script is based on
SkeletonUtilityGroundConstraint.cs, there might be changes in the underlying IK handling in the new version. Compare theIKConstraints.csfile between the two versions to identify any significant changes. - Test in a clean project: Create a new Unity project and import the spine-unity-4.2-2024-07-19 package. Then, add your custom IK script to see if the issue persists. This can help isolate whether the problem is with the project setup or the script itself.
If you still encounter issues, you can share your sample package/project for further investigation. You can send it as a zip package to contact@esotericsoftware.com, briefly mentioning this context so that the team can have a look at it.
I've tested in a clean project, the issue remains :/ Will send the package to the email, will be using the same subject as the titel here
@PeterBacall Sorry for the troubles and thanks for reporting! During a recent bugfix commit I have accidentally introduced a bug which causes your SkeletonUtilityConstraint subclass to not receive updates.
This issue has just been fixed on the 4.2 branch. A new spine-unity 4.2 unitypackage is available for download here as usual:
https://esotericsoftware.com/spine-unity-download
Please do let us know whether this resolves the issue on your end as well.
Issue ticket URL for later reference:
EsotericSoftware/spine-runtimes2587
Harald It did solve it on my end as well, thank you! 
@PeterBacall Glad to hear, thanks for letting us know!