macOS ignores browser.download.start_downloads_in_tmp_dir setting
I started automating the organization of my Downloads folder and after moving to Firefox full time found out that every download creates two files. This is related to the Firefox creating an empty placeholder with the original file name and a .part temporary file.
What happens is that my folder automation moved the empty file to the final resting place while the download is being streamed into the .part temporary file. In the end I end up with two files: one with zero bytes and a secondary one original-filename-1.
I tried to fix this issue enabling the browser.download.start_downloads_in_tmp_dir setting, but it seems the flag is ignored in macOS 27 and Firefox 158. It still creates the two files in my Downloads folder and the behavior I described above keeps happening.
Is there a way to use a temporary directory or forcing Firefox to use one file only?