I’m not super familiar with the FreeCAD file format internals, but I assume it implements history using Open CASCADE API’s, in an application specific format. W

I’m not super familiar with the FreeCAD file format internals, but I assume it implements history using Open CASCADE API’s, in an application specific format. We have some internally developed CAD tooling based on Open CASCADE that uses the OCAF framework to store history inside a custom container format. Any code that links OCCT can in theory get the contents of the container using API calls, but to interpret it, you would have to write a lot of application specific logic on top of that (we wrote our own wrapper API’s around that to expose the file format to e.g. scripts etc)