Definition
GPTBot is the user-agent OpenAI uses to crawl the web for TRAINING data, not for ChatGPT's real-time retrieval. Blocking GPTBot in robots.txt only prevents your content from being used in future OpenAI model training. It does NOT affect ChatGPT's ability to cite your pages via OAI-SearchBot retrieval.
User-agent: GPTBot Disallow: / (Blocks future training use, but ChatGPT can still cite the page through OAI-SearchBot retrieval.)
How to optimize
Decide based on your content policy. Many publishers Disallow GPTBot but Allow OAI-SearchBot: opt out of training, opt in to citation. VectorCite's ai-bot-access signal scores this distinction.