For reference, this is how I do it in my Caddyfile:

   (block_ai) {
       @ai_bots {
           header_regexp User-Agent (?i)(anthropic-ai|ClaudeBot|Claude-Web|Claude-SearchBot|GPTBot|ChatGPT-User|Google-Extended|CCBot|PerplexityBot|ImagesiftBot)
       }

       abort @ai_bots
   }

Then, in a specific app block include it via

   import block_ai