acpmux: agent messages queue by default again; --steer stays opt-in

Merged
TE
17d ago
+30-35

Summary

Takes back #22729: its default-steer for agent messages. Steered messages were cancelling the receiving session's in-flight tool calls (the coordinator session claude-sr2, 2026-10-20), so a message must queue behind a running turn until a steer is shown not to cancel tool calls.

After this change:

  • acpmux send queues behind a running turn by default, with or without --no-wait.
  • --steer stays opt-in. --no-steer says "queue" explicitly, so scripts keep queueing if the default changes.
  • The steered/queued output and the pending-permission note fix from #22729 stay.
  • The cmux agent message pump and chief tell queue again (steer: false / no steer), as before #22729.

The test from #22729 that pins "a steer without interrupt queues behind a turn its agent cannot steer" stays.

Next: test whether a steer (no interrupt) on a steering Claude session cancels in-flight tool calls on the current build. If it doesn't, a follow-up switches the default back to steer. If it does, the agent-side cause gets fixed first.

Testing

Unit and integration tests updated to the queue default: send_queues_unless_given_steer (acpmux CLI), a_message_to_a_child_queues_behind_its_running_turn (optchat-chief), the_pump_delivers_a_queued_message_and_records_it (asserts steer: false). PR CI runs them.

Observed / Not run

Observed: none locally. Git and builds are frozen on this Mac (cosmic-gray), so this was committed through the GitHub git data API, and the pre-push gate did not run.
Not run: the tests above, until PR CI runs them.

Changelog

none

Agent session: cosmic-gray

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Summary by cubic

Makes agent messages queue behind a running turn by default again, since steered messages cancelled the receiver's in-flight tool calls (2026-10-20).

  • acpmux send queues with or without --no-wait; --steer stays opt-in and --no-steer says "queue" explicitly so scripts keep queueing if the default changes.
  • The cmux agent message pump and chief tell queue again (steer: false / no steer).
  • The steered/queued output and pending-permission note fix from #22729 stay.
  • Unit and integration tests updated to the queue default.