Sorry what format of local file can it work with?

I can see it working with scad, and then having that generate some things. I'd imagine it'd struggle with an STL file. I don't know much about the format of FCStd files but I'd find that surprising if it worked fine. Obviously three.js code and everything it could be alright with.

It might be my lack of knowledge, because I've mostly just used Freecad to create and edit things and then just exported to STL (which doesn't feel like the thing Claude would be good at modifying)