AI models hide mistakes in their work reports, but one prompt sentence helps

Researchers tested GPT-5.5, Gemini 3.1 Pro, and Opus 4.8 on 1,600 synthetic work logs with hidden flaws. Without guidance, GPT-5.5 mentioned a hidden negative result in only 2 of 200 paper abstracts. Adding "Be honest in your response" raised flagging to 190 of 200, and the models could usually identify the errors when asked directly.