Bug Report Case 1210824 - the response was basically "it's by design, we aren't going to fix it, you can make a feature request at http://feedback.unity3d.com/" (which is of course a link to the old feedback site that doesn't exist any more and just redirects to these forums). PlayableGraphs are really handy for playing animations in Edit Mode, particularly using OnValidate which is called when assemblies are reloaded or when anything is changed in the Inspector. Except that saving the scene causes Unity to destroy my PlayableGraph and does not call OnValidate again afterwards. Unity support claimed that this is "by design" because PlayableGraphs can't be serialized, but: Serialized fields don't lose their values when saving the scene. Non-serialized fields don't lose their values when saving the scene either. You need to explicitly make sure that you destroy any PlayableGraphs you created when exiting Play Mode or when scripts are recompiled to prevent Unity from giving you a warning. Yet Unity thinks it's fine to just destroy them when the scene is saved. So in most circumstances Unity blames me for not destroying them and won't do it automatically, but then it goes ahead and destroys them for no reason when saving the scene. And it is of course extremely unlikely that this "by design" behaviour is actually documented anywhere.