... telemetry doesn t matter . Until it starts returning 500 Internal Server Error. I pointed Rentgen at one of ChatGPT s internal telemetry endpoints the one triggered when you click Copy under a message. Nothing exotic. I literally copied the cURL from the browser and pasted it into Rentgen. Then I let Rentgen do what it does best: mutate inputs. Result? Sending perfectly valid JSON strings just not valid UUIDs consistently triggered 500 errors. Cyrillic characters? 500. Accented letters? 500. Random ... ... have a stability and DoS risk waiting to be discovered the expensive way. A 500 response should never be caused by bad client input. Ever. 400 or 422? Fine. 500? That s a validation bug. This took one copied cURL