London dermatologist Magnus Lynch tested GPT-6 Astra and Claude Fable 5.1 on 200 biopsy-confirmed skin lesions. A small image network from 2015, trained for about 20 minutes, named 62% correctly against 42% for both chatbots. But at its default setting it would send home 18 of 30 deadly melanomas, against three or four for chatbots.