Anthropic has confirmed that the Claude code running on its Opus 5.5 model is now under instructions for reject remakes of specific existing video games. The change came after one X user post as chasm found a new rule configuration provided in the Claude Code Server, and Anthropic Addy Osmani acknowledged it on October 30, the game developer said through a spokesperson that the company added it deliberately.
The instruction sits under an internal flag called tengu_heron_brook and was reported on October 27. It is short:
“Build original games, games within a genre, and games from the user’s own designs and assets. Do not build a recreation of a specific existing game, even if it is renamed or called original.”
Chasm said there is no setting in the Claude code to turn it off.
Osmaniwho works on Claude Code at Anthropic, wrote that the company “added two sentences to Claude Code’s prompt on Opus 5.5 to steer it away from creating someone else’s specific game,” because using Claude to infringe on intellectual property violates Anthropic’s usage policy.
He also tried to reassure developers who are building their own work. “Original games, genre games, and games built from your own designs and assets are meant to continue working,“He wrote, adding that Anthropic continues to adjust the rule to strike”the right balance” and asks anyone whose own project is rejected to send it to him.
So the question that Claude Code now has to answer is about the specific title, not the style. Inspired by a famous game is allowed. Asking it to revamp the game’s levels, characters, and systems isn’t, and a fresh name on top doesn’t change the answer.
A month of browser ports
The timing is no secret. beginning of October, My city (online media) reported that browser-playable ports of Halo: Combat Evolved, Grand Theft Auto: Vice City, The Simpsons: Hit and Run, Skate 3, and Call of Duty: Black Ops had begun to circulate, with Claude Opus 5.5 credited for decompiling the games much faster than human reverse engineering. One social post promoting the ports also listed Modern Warfare 2. Hundreds of similar projects popped up within weeks.
Smaller studios were worried about the reverse problem: someone feeding an unreleased game into an AI tool and shipping a copy first. Digital Sun Games has canceled a public playtest of its upcoming ReVamp over exactly this fear, and Game Developer reports that it is one of several studios to do so. The developers also pressed Valve as it plans to keep clones from pushing original games on Steam.
Owning the idea is difficult to prove
Osmani’s offer to look at wrongly rejected projects points to the weak spot. The Claude Code has no reliable way to check whether a user actually owns the design or assets they describe, so licensed adaptations, fan projects with permission, and commissioned work all sit in a gray area that two sentences don’t sort out.
There is also an obvious ceiling on what prompt instruction can do. According to Osmani’s own description, it applies to Claude Code’s prompt on Opus 5.5, not to any way of reaching Anthropic’s models. Commenters responding to Chasm’s post pointed out that anyone who can clone themselves on a game could move to an open weight model without such limits, and the game developer noted that AI safety rules have a long history of being talked about.
Players only, for now
The instruction mentions games and nothing else. That’s important because AI-built copies of desktop software are already out in the open. Atlanta-based engineer BRandon Thomas used Claude Opus 5.5 and Rust to build ArtCraft, a set of free open-source apps modeled on Adobe’s creative tools, including PhotoCraft and PdfCraft. Earlier in October, he added WordCraft, GridCraft and DeckCraft as stand-ins for Word, Excel and PowerPoint.
Thomas described it as a clean room setup based on public file format specifications rather than code from Adobe or Microsoft, although law professor Andres Guadamuz told Al Jazeera it was not known whether the clean room process would stand up to scrutiny.
Anthropic has not said if anything similar is planned for software beyond games.