Finally managed to kill the traffic:
1. renamed the worker - the bot was bypassing the route on the domain and using the worker.dev domain
2. add WAF rules to block gptbot in user agent
3. serve zip bomb on request from GPT.
interesting that GPT was accessing the worker directly to bypass the WAF rule son Cloudflare
interesting that GPT was accessing the worker directly to bypass the WAF rule son Cloudflare