Most probably not a kata issue.

May have been a platform issue. Not reproducible now.

I get the same, but only running the tests - submitting it works fine.

yes. same here

Int32 is the wrong data type for this. It should be Word32. The number in the example 2149583361 is not representable in Int32. Haskell has a type sytem to enforce good coding not work around it. I would say this kata is non-solvable with the Int32 interface.

The haskell version of this Kata appears bugged, just running the code with no changes (expecting a runtime error) gives:

/tmp/haskell1141012-7-88dasz/ProcessTree.hs:2:8:
Could not find module `ProcessTree.Process'
Use -v to see a list of the files searched for

The preloaded stuff is seemingly not preloaded.

there is no reason to rescue, nil will be returned anyway