Function search_candidates 

pub(crate) fn search_candidates(
    candidates: &[SearchCandidate],
    opts: &HistorySearchOptions,
    load: &dyn Fn(&SearchCandidate) -> Result<Option<HistorySession>, HistoryError>,
) -> HistorySearchOutcome

Search message content and tool calls across a chosen set of sessions, whose content load reads — from a provider transcript or from AgentMux’s record. See [SessionIndex::search_sessions] for why stopping early is always reported.