You are right, it is a lighttable bug. You should log it here
The following work in lighttable without issue
(->> [0 1]
(iterate (fn [[a b]] [b (+ a b)]))
(take 10)
(my-map first))
and
(take 10 (->> [0 1M]
(iterate (fn [[a b]] [b (+ a b)]))
(my-map first)))