OpenAI's documentation of its three crawlers and what each robots.txt setting does, including the one that decides whether your site can appear in ChatGPT search answers.
OAI-SearchBot surfaces sites in ChatGPT search; sites that block it are not shown in ChatGPT search answers.
GPTBot collects content for model training and can be blocked separately from search.
ChatGPT-User makes user-initiated visits and does not decide whether you appear in search.