The turn finalizer already hands back steer text that queued after the
final tool batch — result["pending_steer"], with the comment "hand it
back to the caller so it can be delivered as the next user turn instead
of being silently lost." Every interactive surface honors that contract
(cli.py, gateway/run.py, tui_gateway/server.py all requeue it). The
delegation layer doesn't: _run_single_child never reads it, so a steer
queued into a delegated child that finishes first vanishes with no trace
in the completion entry. There is also no sanctioned sender: the registry
has interrupt_subagent() but no redirection-side mirror, and session.steer
cannot reach children (lazy watch sessions have agent=None, so it 4010s).
Complete the contract for delegated children — both halves:
- steer_subagent(subagent_id, text): redirection-side mirror of
interrupt_subagent(). Resolves the live child in _active_subagents and
queues text via AIAgent.steer(). True means queued, not delivered.
- missed_steer retention: when the child's result carries pending_steer,
_run_single_child names it on the completion entry (missed_steer field
plus a summary note) so the parent can re-issue the guidance instead of
trusting it landed. This is what makes adding a sender safe: without it
the finish-before-drain race silently loses the text — the exact loss
the finalizer contract exists to prevent.
- subagent.steer gateway RPC beside subagent.interrupt so programmatic
hosts (dashboard, voice layers, ACP bridges) get an in-tree caller;
catalogued in programmatic-integration.md.
- docs: "Steering a Running Subagent" section in delegation.md covering
the queued-vs-delivered semantics.
Tests: registry-level steer coverage (delivery, unknown id, empty text,
dead record, raising agent), the finish-before-drain race retaining
missed_steer, and the RPC contract (4000/4002 validation, queued and
rejected envelopes).
SmokeDev
60e1f7517c