Function definition_summary_attempted 

fn definition_summary_attempted() -> &'static Mutex<HashSet<String>>

At-most-once-per-process-lifetime claim set for definition-summary generation attempts triggered from listrecentsessions — see the call site below and db_agent_activity_summaries (OBJECT_SCHEMA_VERSION v28). HashSet::insert returns true only the first time a given definition_id is claimed; every later call for the same id (a repeat poll of “My Agents”) sees false and does not re-spawn.