Overview
- A server-side rule pushed under the internal flag "tengu_heron_brook" instructs Claude Code not to produce recreations of specific existing games and first appeared on October 27.
- Anthropic confirmed the change through technical staffer Addy Osmani, who said two sentences were added to Claude Code’s prompt on Opus 5.5 to prevent IP infringement and that original or user-owned projects should still work.
- The restriction lives on Anthropic’s servers with no user-facing toggle and was rolled out without a prior public announcement or inclusion in the company’s usage policy update scheduled for November 12.
- Developer reaction is mixed: some welcome a limit on low-effort clones while others worry about predictability for workflows and say they may switch to alternative or open models.
- Experts warn the guardrail may only stop casual copycats because rhetorical prompting and open-weight models can bypass server-side rules, and the move could push studios to seek platform-level protections or change how they run playtests.