Function session_history_main_thread 

pub fn session_history_main_thread(
    config_dir: &Path,
    session_id: &str,
    cwd: &str,
) -> ConversationHistory

session_history over the session’s own rows only: sub-agent sidecars are not opened or folded. The handoff brief takes this one, so it pays for neither the frames nor the parse. A page read does not: a dispatch row draws its sidecar frames (#1763).