I am not sure if this is expected or not however in case its not:
if you create a new pdf and save it to a record then run this:
const fileLinks = project_field_project_details_file_urls;
const filenames = project_field_project_details_filename;
const filename = var_tname;
// Filter the array to find the URL containing the file name
const filelink = fileLinks.find(url => url.includes(var_tname));
from within the same automation the project_field_project_details_file_urls doesn’t seem to deliver a set of easily useable URLs however if you call an automation from the create and save one with the above script in it does work as expected.
I assume this is something to do with it returning some sort of temporary url’s or similar.
if run in its own Automation you get returned the URL with filename:
attachment%3Bfilename%3D%22details-1.pdf