Seems like ClearML tasks in offline mode cannot be properly closed, we get ValueError: Unsupported keyword arguments: publish when calling task.close() .
This stems from self.mark_completed() , which attempts to communicate with the backend I assume (even though there is none, since it’s offline mode?)
In turn, this simply does not reach the code where it sets the __main_task to None .

I get e.g.

ClearML Task: Offline session stored in /Users/idan/.clearml/cache/offline/offline-4e2ad0100d114e7ba95cc0a6dcf48f76.zip
Retrying, previous request failed <class 'clearml.backend_api.services.v2_9.projects.GetAllRequest'>: 'Session' object has no attribute '_Session__access_key'

Notice that the API version is set to v2_9 because there is no backend (offline execution) 😕