Are you sure it is the right thread? On mine it shows the title of the last agent thread even though I'm in a text thread.
Yes, and it followed the instructions in my text thread.
I opened a previous agent thread and it gave me the option to include both threads to the context of the inline prompt (the old text thread was included and I had to click to exclude it, the new thread was grayed out and I had to click to include it).
There is also the "+" button to add files, threads etc, though it would be nice if it could also be done through slash commands.