From which I was able to then say, "Can I have the equivalent source code" and it did that too, from which I was able to spot my mistake in my original attempt. ( The KDF was using md5 not sha ).
I'm willing to bet that LLMs are also just as good at coming up with the right ffmpeg or imagemagick commands with just a vague notion of what is wanted.
Like, can we vignette the video and then add a green alien to the top corner? Sure we can (NB: I've not actually verified the result here) : https://claude.ai/share/5a63c01d-1ba9-458d-bb9d-b722367aea13