Function compute_overlays 

pub fn compute_overlays(
    start_at: Option<&OwnedRow>,
    constraint: Option<&Constraint>,
    overlay: Option<&Overlay>,
    gate_sort: &Sort,
    reverse: bool,
    predicate: Option<&RowPredicate>,
    multi_constraints: &[MultiConstraint],
) -> Overlays

The full ordered narrowing pipeline: startAt → constraint → each non-empty multiConstraint → filter (computeOverlays, memory-source.ts:722). Pure — no leaf access. gate_sort/reverse are the connection comparator — the one the downstream start gate (generate_with_start) applies — NOT the scan’s constrained index sort (see overlays_for_start_at’s comparator invariant; the splice’s interleaving comparator is a separate parameter of generate_with_overlay).