Anthropic tells Claude Code to stop recreating existing games

Anthropic has changed the system prompt in Claude Code, running on Opus 5.5, so the tool steers away from recreating specific existing video games. Anthropic engineer Addy Osmani confirmed the change in a post on October 30, saying the company “added two sentences” to the prompt “because using Claude to infringe IP is against our usage policy.”

Osmani said original games, genre games and games built from a user’s own designs and assets are meant to keep working. He added that Anthropic will keep iterating to get the balance right, and asked users whose own projects get refused to send them to him.

What the prompt says

A user going by “chasm” was among the first to notice the change, saying the rule appeared in the Claude Code prompt on or around October 27. Screenshots and prompt text circulating online say the rule tells Claude to build original games, games in a genre, and games from the user’s own designs and assets. It also tells Claude not to build a recreation of a specific existing game, even one that has been renamed or labeled as original. Osmani did not confirm that exact wording.

According to Ars Technica, XDA independently found the rule in version 2.1.314 of the Claude Code binary, released October 30. XDA also reported that the rule’s identifier, “tengu_heron_brook”, had served other purposes in earlier versions. It said Opus 5.5 appears to carry its own separate instructions restricting game recreations as part of its system prompt bundle. Ars Technica notes that a handful of issue reports on Anthropic’s GitHub suggest the prompt is interfering with some game development work. Rock Paper Shotgun reports that Game Developer asked Anthropic for confirmation and was pointed to Osmani’s post.

Why it matters

AI coding tools have fed a surge of projects built on existing games, including AI-assisted decompilations, recompilations and ports of retro titles. Ars Technica reports that some developers are wary of showing early demos publicly because of quick copies. It also reports that decomp.dev, a long-running community for game decompilation, announced last month that it was shutting down. Maintainer Luke Street wrote that AI tools had broken the community aspect of decompilation, as newcomers race to port games using decompilations they did not contribute to.

Rock Paper Shotgun points out that Bethesda has apparently taken legal steps to get an AI-generated Fallout game taken offline, and that not every company has responded to the trend with legal action. Ars Technica argues that Anthropic’s change could reduce its own exposure to copyright liability but is unlikely to slow the broader wave. Its reasoning is that copiers can move to other frontier models without such limits, or to cheaper open-weight models that are not far behind in capability.

Ars Technica also says that decompilation based on reverse engineering generally passes legal muster when art and sound assets are left out. It adds that individual users of Claude may not be so careful.

What we don’t know yet

The line between a banned recreation and an allowed genre game is not defined in anything the sources show. Ars Technica asks whether AI-made mashups, such as Spider-Man in Batman: Arkham Knight, count as a “recreation of a specific existing game,” and whether a direct Tetris copy differs enough from a Tetris-style game for a model to tell. The Verge says it has asked Anthropic whether other Claude system prompts have been or will be updated.