Adding a tangential anecdote.

I asked GPT-5.4 High to draw up an architecture diagram in SVG and left it running. It took over an hour to generate something and had some spacing wrong, things overlapping, etc. I thought it was stuck, but it actually came back with the output.

Then I asked it to make it with HTML and CSS instead, and it made a better output in five seconds (no arrows/lines though).

SVG looks similar to the XML format of spreadsheets. I wonder if LLMs struggle with that?

The LLMs seem to struggle at anything that isn't relatively well anchored in whatever space. HTML documents have a lot of foundation to them in the training data, so they seem to perform well by comparison to other things.

I just spent a few hours trying to get GPT5.4 to write strict, git compatible patches and concluded this is a huge waste of time. It's a lot easier and more stable to do simple find/replace or overwrite the whole file each time. Same story in places like Unity or Blender. The ability to coordinate things in 3d is really bad still. You can get clean output using parametric scenes, but that's about it.

Claude's diagramming tool that they have built into their web UI is my goto for this task. It's reliable enough that I often will delegate to it first with what I need written in prose instead of using mermaid/lucid diagram

I’d try asking it for a mermaid diagram. I think ChatGPT’s web interface will render them.

Gemini is very good with SVG, but I don't really see the similarity to spreadsheets.