Dexvoid It's for an editor tool, adding constraints non-destructively, doing so when a "play mode build" is created requires you to workaround the target transform latch (if there's a target transform being set) by turning off the object the constraint is added to, adding the constraint and configuring it, then turning it back on, my expectation is that the latching wouldn't happen until the active bool is set (directly or via the activate/zero methods), and/or update the latched target transform under similar conditions or when the method is called.

Clearer documentation regarding the transform being latched should probably be added too, this tripped me up for a few hours before I figured it out.

Dor․ Sorry but I'm still a little confused, wouldn't an editor tool like this only need to run in edit mode? Entering play mode causes changes to the scene to be lost once you exit play mode.

If by "play mode build" you're referring to making builds of avatars from play mode like how it worked in older SDKs, please note that this approach is now deprecated and no longer officially supported. Users are expected to make avatar builds via the SDK control panel in edit mode instead.

You can implement the interface if you want to inject your own logic into the build process of an avatar. This interface receives the avatar that is being prepared for upload, not the original instance of it in the scene, which supports making non-destructive changes.

Dexvoid Certain avatar tools such as vrcfury and ndmf execute a build when entering play mode so that non-destructive elements could be tested (usually with other tools such as gesture manager or av3emulator), the "play mode build" I described is entirely meant for this use case - testing before upload.

My code works perfectly fine when uploading, it is simply that testing it with the play mode build is impossible without explicitly working around the (undocumented) transform latch.