OpenAI’s rival to Claude Code has a very strict command line for AI Agents: Never talk about …

OpenAI has banned its AI Agent, Codex, from mentioning goblins and other mythical creatures. Codex is OpenAI’s answer to Anthropic’s Claude Code AI Agent that can also generate and execute code through a command-line interface (CLI), but its latest version now comes with unusually strict behavioural rules embedded in its system prompt.

According to newly released base instructions for GPT-5.5 in OpenAI’s Codex CLI, the model is explicitly told to “never talk about goblins, gremlins, raccoons, trolls, ogres, pigeons, or other animals or creatures unless it is absolutely and unambiguously relevant to the user’s query.”