Steve Yegge's recent blog posts claim that SourceGraph are getting a pretty good result by using embeddings created from their knowledge graph of the code structure. That's still the usual [create embeddings, search against embedding of query, retrieve results and use them as prompt] schlep, so yeah, it isn't really understanding architecture well yet.

I too have a job where almost every question is about structural understanding and improvement of a large existing codebase. I'd love to have AI help, but I think it's going to take another iteration or three of model architecture to get there.