Anthropic Adds Claude Rule Against Recreating Existing Games, but the Copying Wave Rolls On

Anthropic has slipped a new instruction into its Claude models aimed at stopping them from rebuilding specific existing video games. The change may shield the company from some liability, but it probably won't do much to slow the surge of AI-assisted game porting and copying seen in recent months.

An AI decompilation enthusiast posting as "chasm" was among the first to flag the change late last week, noting a rule that appeared to be added to the Claude Code prompt on or around October 27. The rule, filed in a json under the name "tengu_heron_brook," tells the model to build original games, games in a genre, and games from the user's own designs and assets, but not to recreate a specific existing game, even if it is renamed or called original.

XDA later independently confirmed the rule appears in version 2.1.314 of the Claude Code binary, released October 30. XDA also reported that "tengu_heron_brook" had served other purposes in earlier versions, and that the Claude Opus 5.5 model appeared to carry its own separate instructions restricting game recreations.

Anthropic software engineer Addy Osmani confirmed on social media 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 said the prompt still permits original games, genre games, and games built from a user's own designs and assets, though a handful of issue reports on Anthropic's GitHub suggest the new rule is tripping up some game development use cases.

Source: Ars Technica