Function recv_map_ok_publish_with_step 

pub fn recv_map_ok_publish_with_step<Rx, Tx>(
    rx: &mut Rx,
    tx: &mut Tx,
    input: &mut [u8],
    on_full: OnFullV1,
    wait: &mut impl WaitStrategy,
    map_ok: fn(&[u8], &mut [u8]) -> usize,
) -> Result<bool, LaneTxError>
where
    Rx: LaneRx,
    Tx: LaneTxWith,

Receive → (MapOk) transform → publish-with (slot write).

This avoids an intermediate output buffer copy by writing directly into the lane slot.