I'm building a similar project, and I may open-source it. I'm using OnlyOffice and a coding agent that modifies the files with Python libraries in a sandbox (e.g. python-pptx for PowerPoint files).

Have you also considered using a solution like OnlyOffice for your product? Or a "Notion-like" lib such as Tiptap or PlateJS?

I definitely looked at TipTap and ended up building off their Y.js backend, which is great: https://tiptap.dev/docs/hocuspocus/getting-started/overview

I wanted to build something canvas-based, so that eliminated most of these options. I also just wanted full control of that part of my stack... it's the core product after all. There are several TipTap/ProseMirror wrappers out there already.

You should share yours though, would be interested to see