In case you missed it, ChatGPT 5.1 had a tendency to talk about “goblins” in its responses. Supposedly this was a result of training a “nerdy” personality, but it bled into the model as a whole. Because the training run for the latest model already had this flaw, they had to add specific instructions to the system prompt for their Codex coding tool to avoid this behaviour.

Here’s the full prompt from their github. In fact, they repeated the goblin instructions twice, cos you know that will definitely fix it. It’s an interesting read if you consider each one of these instructions were meant to prevent some undesired behaviour: https://paste.sh/Iev3HtMe#JZ4dw_CkvJcpVmjjoy7WZnSn

More info here: https://news.northeastern.edu/2026/05/06/chatgpt-goblins-problem-ai-behavior/

OpenAI’s own blog post casually explaining why they couldn’t predict that their state of the art model would obsess about goblins: https://openai.com/index/where-the-goblins-came-from/