Nope, we built the workflow builder entirely ourselves, but I guess most workflow builders do end up looking very similar!

That strikes me as a surprising choice given the amount of prebuilt integrations with n8n

One factor in hindsight for doing this in-house was we did find out that AI can struggle with understanding and navigating existing workflow builders that were built and optimized for human usage and comprehension e.g. what nodes are available, the options that can set inside of those nodes and even how they are named had quite an impact on whether the AI could reliably form valid workflows on its own.

Not that surprising if you take n8n license into account. Its very prohibitive.