When a directory doesn't exist, the resolve() method trims everything except the first component (a doesn't exist here):

import pathlib
p = pathlib.Path(".", "a", "b", "c")
p
WindowsPath('a/b/c')
p.resolve(strict=False)
WindowsPath('C:/Python36/Scripts/a')

I would expect C:/Python36/Scripts/a/b/c
Am I missing something?

I'm not sure - I try the same thing (on 3.6, 3.7 and 3.8) and get different results:

>>> import pathlib
>>> p = pathlib.Path(".", "a", "b", "c")
>>> p.resolve(strict=False)
WindowsPath('a/b/c')

Are you sure that it's not successfully resolving a link of some kind?

If "a" exists in the current directory, I get this (correct) result:

>>> import pathlib
>>> p = pathlib.Path(".", "a", "b", "c")
>>> p.resolve(strict=False)
WindowsPath('<my CWD>/a/b/c')

So there's an existence check of some kind that's not being handled properly.