It's not immediately obvious which 3rd party apps powered by LLMs-- the most frequent blatant usage I can see is captured by the dominant LLM platforms (chat.openai.com, Gemini, etc).

Of course AI powered coding tools are an exception but what other apps use LLMs or reasoning/CoT LLMs extensively?

I assume a ton of apps make API calls to LLMs in the background, to get or process information, though this is not always clear in the frontend/UX. I'm curious what are known uses.

I know some flashcard-like apps and other educational features use LLMs extensively, some customer service applications-- what else?