I just made a similar post.  In testing, it looks like you currently have to add a "Response" text.  If you even put a period in Response, then the attachment sticks.

I can confirm that this is by design. Attachments are only relevant in the context of a ticket response. 

If you say so, but our help staff receives documents outside of OsTicket that are relevant to the ticket, but cannot attach it without also sending it to the contact.  Not all attachments are needed, or should be seen by the contact.

... these docs are relevant to the programmers that end up supporting the situation.

@[deleted] - If the docs are internal then the logical thing to do is - open the ticket and then post an internal note with the attachments. Attaching files to the message will expose the attachments to the contact.

Okay, thank you.  That confirms how we are using the system now.  So it does take a 2nd pass at the ticket to get an internal-only attachment.  I will say they desire attaching internal documents on ticket creation, but at least we now know.  Thanks.

Unless you add an "internal note" form on staff ticket-creation as well.. ;-) </pot-stirrer>