but it seemed like even after .upload_artifact() has done its job, the task's terminal didn't terminate.

DeterminedOwl36 I'm not sure I understand this statement - do you mean the console print outs did not day "task completed"?

SuccessfulKoala55 I don't think so cuz the files are just small dataframes and the thing is I tried saving those output files on my local machine then created a new task, uploaded them with a new code on .ipynb, and it took less than a minute and everything works fine. (the frozen script is .py)

It printed "ClearML couldn't detect iterations..." something like this, but the process never ends, just freezes here. I mean I can't run any further commands with this terminal cuz it's running this task, except ctrl+c.

DeterminedOwl36 perhaps this is a side-effect of the running environment? What are you using to run the experiment? Is this clearml-agent running the experiments remotely?

Most likely the files is large and it's just uploading it?