I can play a Mockingbird with it self in my luajit console, but it will stackoverflow at luau demo page.

[yhm-amber]

My code:

This should stackoverflow:

(function (x) return ((x) (x)) end) (function (x) return ((x) (x)) end)

But this shoud not:

(function (x) return (x) (x) end) (function (x) return (x) (x) end)

That is they in luajit:

And That is in luau demo:

Looks luau do not have lazy feature ... did this true ?

[vegorov-rbx]

Compared to Lua/luajit, Luau doesn't support infinite tail recursion.

You have to rewrite your code to avoid it.