One robots.txt line can erase you from AI answers.
Robots.txt is the first file every crawler reads, and well-behaved AI crawlers — GPTBot, ClaudeBot, PerplexityBot — honor it strictly. A single disallow line, often copied from a template or left over from a staging setup, silently removes your entire site from ChatGPT, Claude, and Perplexity answers. Nothing errors; you just stop being cited.