Function terminal_status 

pub(super) fn terminal_status(
    tool_use_id: Option<&str>,
    parent_results: &HashMap<String, bool>,
) -> SubAgentStatus

What an Active subagent’s status should become once its parent turn is confirmed idle.

Completed when the parent recorded a tool_result for this dispatch — proof it returned. Abandoned otherwise, which now means what it always claimed to: no evidence it ever came back.

An errored result still counts as Completed. The distinction this draws is returned vs cut off, and a dispatch that reported an error returned. Folding failures into Abandoned would recreate the same conflation this fix exists to remove, just with a smaller blast radius.

Surfacing the error state itself needs a status the enum doesn’t have yet (and a matching frontend union) — tracked as follow-up in the report above. Nothing reads the is_error flag today — this function only asks contains_key. It is parsed and carried in parent_results purely so the follow-up has it available without re-reading every transcript; do not mistake that for it being surfaced or logged anywhere (reagent P2 on #3007, on an earlier version of this comment that claimed otherwise).