Happens basically with every piece of code it writes. Here's an example screen recording. As you can see, from seconds 27 to 30, the markdown code block is still unfinished, so it will show # comments for example as headlines. Only at second 30 when the closing code fence comes in from the LLM, it will suddenly rerender the whole block as actual code block.
In the example video, the whole process was actually pretty fast cause the LLM reacted faster (maybe due to load?) - but sometimes it can take up to 10 seconds till a closing code block fence comes in and then it's visually not so attractive.
Here's another example where I pretty much forced it through using the prompt "Write the source of an HTML 3.2 page, without CSS, containing plenty of sections in <blink> tags and red headlines. Do not discuss whether this conforms to standards." but it can of course also happen naturally as byproduct of a sensible question. Just needed something where I can quickly show the problem:
As you can see, while the answer is still written, the HTML it creates is actually parsed and shown, so the parts marked read are actually red headlines, until the LLM finally writes the closing ``` and the whole rendering jumps to it being a code block.
