Anthropic adds Claude Code prompt rule against recreating specific existing video games

Left · 2Anthropic has updated Claude Code's system prompt to stop the tool being used to recreate existing video games, while still allowing other game development. 1 2 Left · 1A social media user and AI decompilation enthusiast going by "chasm" was among the first to note the change, saying a rule seemed to have been added to the Claude Code prompt on or around October 27; the rule sits in a json file under the name "tengu_heron_brook". 2 Left · 2The wording reported is: "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." The Verge quotes the last words as "named or called original" and describes the post as a screenshot that allegedly shows the sentences. 2 1

Left · 2Addy Osmani, an Anthropic software engineer, said on 30 October 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." They said original games, genre games and games built from a user's own designs and assets are meant to keep working, that Anthropic will keep iterating, and that users whose own work Claude turns down should contact them. 2 1 Left · 2Ars Technica says Osmani confirmed the change, while The Verge says Osmani did not confirm the specific language but did say the prompt had been updated. 2 1 Left · 1According to Ars Technica, XDA independently verified that the rule appears in version 2.1.314 of the Claude Code binary, released on October 30. XDA also reported that "tengu_heron_brook" had been used for other purposes in earlier versions, and that Claude Opus 5.5 appeared to have its own separate instructions restricting game recreations in its system prompt bundle. 2

Left · 2The change comes amid a surge of AI-assisted copying of games. The Verge says retro gaming is being overrun with AI-made decompilations, recompilations and ports. Ars Technica adds that copies of game demos have made some developers afraid to show early work, and that the decomp.dev community shut down last month, with maintainer Luke Street saying AI had broken the community aspect of decompilation. 1 2 Left · 1Ars Technica argues the rule is unlikely to slow the trend much, because copiers can switch to other frontier models without such limits or to cheaper open-weight models. It says the rule may help shield Anthropic from copyright liability, and notes that decompilation generally passes legal muster if expressive elements such as art and sound are excluded. 2 Left · 2Open questions remain. Ars Technica says a handful of GitHub issue reports suggest the prompt is getting in the way of some game development, and asks how Claude can tell a direct Tetris re-creation from a Tetris-style game, or how it should treat mashups of existing games. The Verge says it has asked Anthropic whether other Claude system prompts have been or will be updated. 2 1