agent-shell 0.81.1 will put a dropped file into the live prompt while the agent is still working, if that prompt exists. There is no 0.81.0 tag. I compared the v0.80.2 and v0.81.1 sources and did not run Emacs.

v0.80.2 queued a mid-turn drop, send-region, or shell-command output whenever shell-maker-busy was set. Quote-region already ignored busy and looked for agent-shell--prompt-input-start. 0.81.1 moved drop, send-region, shell-command output, and yank-media onto that same check, then agent-shell-insert. No live prompt still queues.

agent-shell-prompt-queue still keys on busy. Persistent prompt is on by default.