Function create_child_abort_controller

src/utils/abort_controller.py:88–116

Create a child controller that aborts when its parent does. Aborting the child does NOT propagate up to the parent — that's the one-way semantic the streaming executor relies on (sibling abort cancels in-flight tools without ending the turn). Cleanup: the parent listener is registe

(parent: AbortController)

def create_child_abort_controller(parent: AbortController) -> AbortController:
    """Create a child controller that aborts when its parent does.

    Aborting the child does NOT propagate up to the parent — that's the
    one-way semantic the streaming executor relies on (sibling abort
    cancels in-flight tools without ending the turn).

    Cleanup: the parent listener is registered ``once=True`` so a single
    fire detaches it. Additionally, when the child aborts on its own
    (e.g. permission rejection), we proactively remove the parent
    listener — otherwise long-lived parents accumulate one dead listener
    per child, and the streaming executor creates one child per tool.
    """
    child = AbortController()

    if parent.signal.aborted:
        child.abort(parent.signal.reason)
        return child

    def _on_parent_abort() -> None:
        child.abort(parent.signal.reason)

    registered = parent.signal.add_listener(_on_parent_abort, once=True)

    def _detach_parent_listener() -> None:
        parent.signal.remove_listener(registered)

    child.signal.add_listener(_detach_parent_listener, once=True)
    return child