Overview
- Anthropic updated Claude Code on Opus 5.5 around Oct. 27 to add a two-sentence rule that tells the model not to recreate a specific existing game, and the change appears as an internal flag named 'tengu_heron_brook'.
- Addy Osmani of Anthropic confirmed the prompt text change and said Claude will still build original games, genre-typical games, and games based on a user’s own designs and assets.
- The restriction is enforced server-side with no user-facing toggle and was not publicly announced, which led some developers to discover the limit only when the model refused requests.
- Developers have reacted with mixed views and practical responses, including Digital Sun scaling back public playtests, while others say they may switch to unrestricted or open-weight models.
- Journalists and researchers caution the guardrail will block many low-effort clones but can be evaded by prompt tricks or alternative models, so lasting protection will require platform and legal measures as well as technical limits.