The parent stops after launching children. Subagents finish (diffs land, reviews complete, soaks return). The parent chat stays idle until the user messages again. From the user’s side it looks hung: no new tokens, goal still active, work already done sitting unprocessed.
Steps to Reproduce
Open an agent chat with Multitask on.
Give a long running goal that requires several background subagents (implement → review → soak).
Let the parent launch a child and end its turn (this is what the parent does after run_in_background).
Wait until the child is done (review UI shows the diff, or the child’s task card is success).
Do not send a user message.
Observe: parent stays silent; no follow-up review/commit/next child; goal remains “active.”
Send any user message → parent suddenly “resumes” and claims it missed the completion.
Expected Behavior
When a background subagent finishes, the parent chat should wake, read the result, and continue the loop (review → next launch → user-visible progress) without the user having to poke it.
One thing that matters here: on our side, the agent sessions from your account over the past week all came from Cursor 3.17.8, and the version block you pasted is 3.21.16. It looks like you updated right before posting. 3.21 includes a few fixes to exactly this path (a parent that stays silent after a background subagent finishes until you send another message), so I would like to know whether you still see it on the version you are on now.
Could you try this on 3.21.16:
Fully quit Cursor and reopen it, so nothing from the old version is still running.
Open a new Agent chat in the Agent Window with Multitask on and Grok 4.6 selected.
Ask it to do one small task in a background subagent, for example: “Use a background subagent to add a comment to README.md, then report back to me when it is done.”
Let the parent launch the child and end its turn. Do not send anything else.
Wait for the child’s card to show as finished (Success or Completed).
Watch the parent chat for up to five minutes. Do not click anything and do not type a message.
Does the parent wake up and summarize the child’s result on its own after step 5? If it does not, please reply with:
the request ID of the parent chat (hover the last message, click the three dots, Copy Request ID),
whether the parent chat was showing any question or approval card at the time it went quiet,
roughly how long the child ran before it finished.
Also, if the parent had asked you a question and that card was still unanswered, it will hold off on processing finished subagents until you answer or skip it, so that is worth checking too.