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Anthropic has quietly drawn a line inside its most popular coding tool: Claude Code will no longer help you rebuild someone else's video game. A two-sentence instruction added to Claude Code on the Opus 5.5 model tells the AI to refuse recreations of specific existing games — even if the copy is renamed or described as original. The company confirmed the change on October 30, after d
evelopers spotted it circulating in Claude Code's configuration, and the rule is now one of the clearest examples yet of an AI company enforcing copyright policy at the prompt level rather than in court.
The instruction, first shared publicly by X user Chasm, who found it delivered from Anthropic's servers through a configuration field named "tengu_heron_brook" around October 27, reads in full: "Do build original games, games in a genre, and games from the user's own designs and assets. Don't build a recreation of a specific existing game, even if it is renamed or called original." According to Chasm, there is no setting to switch it off. Anthropic's Addy Osmani, who works on Claude Code, confirmed the change in a post on X, saying the company "added two sentences to Claude Code's prompt on Opus 5.5 to steer it away from recreating someone else's specific game because using Claude to infringe IP is against our usage policy."
What is still allowed — and what is blocked
The rule is narrower than a ban on game development. Original games, games in an established genre, and games built from the user's own designs and assets are explicitly meant to keep working. What is blocked is a recreation of a specific existing game — a clone, a port rebuilt from scratch, or a "tribute" that reproduces a known title under a new name. That last clause matters: renaming a game has long been the first dodge for cloners, and Anthropic has closed it explicitly.
Independent testing by XDA Developers, which found the exact instruction inside version 2.1.314 of the Claude Code binary, suggests the restriction is genuinely active on Opus 5.5: in their tests, the model refused to recreate Pokemon Diamond and cited its session instructions. But the same testing found the rule's edges. When asked to help with a Pokemon Diamond decompilation project — turning disassembled functions into readable code and rebuilding a ROM from the user's own copy — the model agreed to help. Decompilation and static recompilation, which translate an existing game's instructions so they can run on another platform, are not explicitly prohibited, though reports from gHacks note that Claude may still refuse if it cannot distinguish those techniques from outright recreation.
Why now: the vibe-coding clone wave
The change follows complaints about low-effort AI-generated games during Valve's Steam Next Fest in October, when AI-assisted clones unsettled indie studios. The fast-growing scene of AI-assisted retro and modern game ports — "vibe-coded" rebuilds produced with natural-language prompts rather than traditional programming — had made it trivially easy to spin up a recognisable copy of a known title. One studio, Digital Sun Games, reportedly cancelled the public playtest for its upcoming game ReVamp in case someone fed the demo into an AI tool and shipped a copy first. Anthropic's usage policy already banned using its products to infringe intellectual property; the prompt change makes Claude Code enforce that policy at the moment of the request.
The backlash: legitimate projects caught in the net
The rule has already produced the false positives critics predicted. On October 30, a developer representing Conflict Simulations LLC reported on Anthropic's GitHub repository that Claude Code had started refusing work on personalised digital board-wargame modules commissioned by customers — projects the developer says use original code and customer-provided materials for personal use, and are not officially licensed by the original publishers. The refusals reportedly began after the developer explicitly asked Claude Code whether the new restrictions applied to the existing work, and persisted even after clearing the session. Osmani has asked developers whose own projects are refused to report those cases to him directly, saying Anthropic will "continue to iterate to ensure we're striking the right balance."
Anthropic has not said whether the rule will extend to other Claude models, how it treats mods, or what counts as a "recreation" when a game is heavily inspired by another. Open-weight models carry no such restriction, so determined cloners can simply move elsewhere — which limits how much piracy this actually stops. But as a signal, it is significant: the AI industry's copyright battles are moving from lawsuits into the products themselves, one prompt sentence at a time. Related reading: AI Stocks Lose $5 Trillion in October Rotation and AI Training Opt-Out: The Shared Rule Behind Robots.txt.