Attachment upload difference between (Drag & Drop / Button)

I don’t know if that counts as a bug, but I find that a bit odd:

When I try to upload a .md file to Deepseek V3.1, I do get the overlay that states the same as when I hover the upload button, that it accepts “TEXT” and “PDF”.

Now Markdown isn’t really anything special, and so I thought it would work, but it opens the file via the file protocol in a new tab.

When I use the upload button, it either converts or just signals in the UI that the Markdown-File has become a text file.

Because I wasn’t sure, whether that’s a file problem, I’ve tried a .txt and .pdf as well. Same behaviour.

So at least for that model, drag & drop does not seem to work. Or maybe it has to do with the latest update?

While writing this, I was still doing some minimal tests, and it even happens to models like the GPT-5 series, so I believe the latest update must’ve caused this.

I could’ve truncated this to hit the point, but I think more information is better, showcasing what I’ve first noticed, and where I went from there.