I'm sorry to hear you're experiencing shader errors after upgrading to Unity 6.3. This appears to be a compatibility issue between the Spine URP shaders and Unity 6.3.
The error indicates that FragmentOutput is being redefined in Unity's URP lighting utility, which suggests there may be a conflict between the Spine URP shader code and Unity 6.3's URP package.
Here are some steps to resolve this:
1. Update to the Latest Spine URP Shaders Package
Make sure you're using the latest version of the Spine URP Shaders package that's compatible with Unity 6. The Spine 4.2 URP shaders should support Unity 6, but you may need to update to the very latest version:
2. Check Version Compatibility
Verify that you're using compatible versions:
- Spine 4.2 runtime supports Unity 2017.1-2023.2 according to the download page
- Unity 6.3 may require special consideration as it's newer than the officially tested versions
3. Temporary Workaround
If updating doesn't resolve the issue immediately, you might need to wait for a Spine URP shaders update that specifically addresses Unity 6.3 compatibility. The FragmentOutput redefinition error suggests Unity made changes to their internal shader code structure in version 6.3.
4. Consider Rolling Back
As a last resort, if you need to continue working immediately, you could temporarily roll back to Unity 6.2 until a compatible Spine URP shaders update is available.
Since Unity 6.3 is very recent, this compatibility issue may require an update from Esoteric Software. The shader errors you're seeing are due to changes in Unity's URP shader include files between versions 6.2 and 6.3.
