Anthropic has added an instruction to Claude Code telling it not to build recreations of specific existing games. X user chasm (@chasmmmmmmmmmmm) spotted it in a post on October 30, and Addy Osmani, who works on Claude Code at Anthropic, confirmed it on X that day.
According to chasm, it reached Claude Code from Anthropic's servers around October 27 under a flag named "tengu_heron_brook", and users have no way to switch it off. The post had about 2.1 million views by November 1.
The rule first tells Claude to build original games, genre games and games from the user's own designs and assets. Then it says: "Don't build a recreation of a specific existing game, even if it is renamed or called original."
Osmani wrote that Anthropic "added two sentences to Claude Code's prompt on Opus 5.5" because using Claude to infringe IP breaks its usage policy. He said original and genre games should keep working and asked developers to send him cases where Claude refuses their own work. Game Developer, which Wccftech credits with first reporting the rule, said an Anthropic spokesperson pointed it to that post.
In GitHub issue #106167, filed October 30, a developer who says they run Conflict Simulations LLC reported that Claude Code now refuses paid work building digital board-wargame modules for clients who own the games. The developer notes the work isn't publisher-licensed, and wrote that refusals began only after asking Claude whether the rule applied. Wccftech covered the issue on October 31.
Why it matters: Microsoft and Epic have sent DMCA notices against agent-built browser recreations, and Digital Sun scaled back a public ReVamp playtest to its Discord over cloning fears. Now a coding-agent maker is acting itself. Original and genre projects remain allowed, but remakes, fan rebuilds and ports of a named game may be refused.
Caveat: This is a prompt instruction for Opus 5.5 in Claude Code, not a retrained model or new terms. Anthropic hasn't said whether it covers other models or products, and the flag name comes from chasm, not Anthropic. As Game Developer noted, it's unclear how Claude would judge whether a user owns a game's designs.
The issue was still open on November 1, asking Anthropic to narrow the rule, add an exemption path for verified professionals and log such changes in the changelog.
