Causes conflict with Light Overlay.

In general, when including code from other libraries without use of Fabric/Quilt's include JiJ configuration, the package should be changed to something unique to the mod.

As this API copies code from org.reflections:reflections without changing the package, it crashes alongside light overlay, which includes an older version of the same library lacking one of the used methods.

Change the package to something like com.yungnickyoung.minecraft.yungsapi.included.org.reflections to fix.

Alternatively, as this seems to be a fabric-only dependency, go the recommended route and include the actual jar to let Fabric do the version handling:

dependencies {
    implementation("org.reflections:reflections:0.10.2")
    include("org.reflections:reflections:0.10.2")
}

Same applies to Javassist.

Thanks, I totally forgot to address this. Will probably just move it to a fabric include like you said

Fixed in the latest releases.