Recently, Claude Opus 5.5 started receiving complaints from users over the AI’s sudden inability to work in tandem with Reverse Engineer Anything, the very same tool that allowed users to decompile and open-source video games . At the time, no rules or updates had officially been announced by Anthropic.

Today, however, we have confirmation that Anthropic is deliberately pushing back against its users’ love of vibe-coded IP theft slop, as a new rule (a flag in Claude Opus 5.5’s code titled “tengu_heron_brook”) instructs the AI to safeguard against prompts that produce “a recreation of a specific existing game, even if it is renamed or called original.”

The new rule was seemingly first spotted by a user on X , but first appeared in Claude Opus 5.5’s changelog on October 27.…