Claude’s new rules against game cloning won’t stop the AI copying boom

Anthropic added two sentences to the Claude Code system prompt for Claude Opus 5.5 to stop the model from recreating specific existing video games, a change first flagged by AI decompilation enthusiast "chasm" around October 27 and independently verified by XDA in Claude Code version 2.1.314, released October 30. Anthropic software engineer Addy Osmani confirmed the change, saying the company acted "because using Claude to infringe IP is against our usage policy," while noting the prompt still permits original games, genre games, and games built from a user's own designs and assets. The rule, stored in a JSON file under the name "tengu_heron_brook," is unlikely to slow the broader wave of AI-assisted game porting and copying, and GitHub issue reports on Anthropic's repository suggest it is already blocking some legitimate game development use cases.

Last week, Anthropic introduced a new system prompt designed to stop its Claude models from recreating specific, existing video games. But while that move could help shield Anthropic from some liability, it’s unlikely to do much to slow a massive wave of AI-assisted game porting and copying that has emerged in recent months. A social media user and AI decompilation enthusiast https://x.com/chasmmmmmmmmmmm/status/2107897874860371988 going by the name “chasm” was among the first to note the prompt change https://x.com/chasmmmmmmmmmmm/status/2116062991686721968 late last week, saying a new rule seemed to be added to the Claude Code prompt on or around October 27. That rule—included in a json file under the name “tengu heron brook”—reads as follows: Do build original games, games in a genre, and games from the user’s own designs and assets. Don’t build a recreation of a specific existing game, even if it is renamed or called original. XDA later independently verified https://www.xda-developers.com/anthropic-testing-potential-crackdown-on-vibe-coded-ports-of-existing-games/ that the new rule appears in version 2.1.314 of the Claude Code binary, which was released on October 30 https://code.claude.com/docs/en/changelog 2-1-314 . XDA also reported that the “tengu heron brook” rule had been used for other purposes in earlier versions and that the Claude Opus 5.5 model specifically seemed to have its own distinct and independent instructions restricting game recreations as part of its system prompt bundle. Following chasm’s initial report, Anthropic software engineer Addy Osmani confirmed on social media https://x.com/addyosmani/status/2116213240363729013 that the company had “added two sentences to Claude Code’s prompt on Opus 5.5 to steer it away from recreating someone else’s specific game because using Claude to infringe IP is against our usage policy.” He added that the new prompt was designed to still allow “original games, genre games, and games built from your own designs and assets,” even as a handful https://github.com/anthropics/claude-code/issues/106167 of issue reports https://github.com/anthropics/claude-code/issues/105589 on Anthropic’s GitHub suggest the new prompt is getting in the way of some game development use cases.