Claude Code Adds Rule Restricting Recreation of Existing Games

Around October 27, 2026, Anthropic added a rule to the system prompt of Claude Code (based on Opus 5.5) (json file named tengu_heron_brook), prohibiting users from using Claude to replicate specific existing games; however, the rule also allows creating original games, games of the same genre, and works based on users' own materials. According to an Ars Technica report on November 3, engineer Addy Osmani confirmed that the reason for this move is that using Claude to replicate existing games would infringe intellectual property and violate Anthropic's usage policy. The Verge also reported on the system prompt update the same day, noting that the addition consists of two sentences aimed at blocking the replication of existing video games, and that the restriction likewise only targets the replication of specific games—users can still use Claude Code to create original or genre-style games. The report also pointed out that since the restriction is implemented only at the prompt level (not the model level), the wave of AI game replication will still be hard to stop. The core facts of this event are: the restriction is enforced only via the prompt, and its scope is limited to the replication of "specific existing games," not the generation of entire game genres.

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