the damn chat.openai.com webapp lags a lot as well on long chats, typing takes so long.
And keeps doing it in intervals in /prepare endpoint, during each prompt.
So if you are working with something sensitive - don't write it to browser directly and edit it there.
The entire conversation sits in the DOM.
For what it's worth I use a small script that essentially deletes old chat messages DOM nodes which significantly speeds it up.
I bet there’s also some React performance issues involved here too
There are some real table stakes FE perf issues with the ChatGPT site