Claude Code now refuses to rebuild existing games, but clones are already everywhere

A quiet rule inside Claude Code

A developer going by chasm noticed that the hidden configuration Anthropic sends to Claude Code, its coding tool for the terminal, had gained a short pair of instructions. One side says what is allowed: helping build original games, games in an established genre, and games based on the user's own design and assets. The other forbids rebuilding a specific existing game, even if the user renames it or insists it is original.

Once the text became public, other developers said they had been turned away too. Some were modding a game or digging through an old project. One person only wanted help analysing harmless decompiled code (code recovered from a finished program), and another wanted a routine comparison of physics collisions in competing games. Both got a flat refusal, according to ifanr.

As ifanr reported, Anthropic's Addy Osmani then confirmed publicly that the team had added the two sentences to the system prompt for Opus 5.5. A system prompt is the standing set of instructions a model reads before it sees your request. He said the goal was to prevent intellectual property infringement.

Why a video is enough to copy a game

The reason for the rule becomes clearer in the cases ifanr collected. Cloning a game used to take some skill at pulling apart code or working out its rules. Now, the article argues, a copier only needs to hand a developer's public gameplay footage to an AI, which can infer the controls and rules and assemble working code.

The developers of 204Snake, a puzzle game that merges Snake with the number-sliding of 2048, saw this happen. Their Steam page was barely up and marketing had not started when a near pixel-identical web game with the same name appeared. The first levels matched the layouts from their technical video. Later levels looked like unplayable puzzles generated in bulk. The copy also locked its undo button behind a 30-second ad and sold a top-up pack.

Japanese developer Kamaboko had a similar experience with Typing Magician, a typing-and-tower-defense game he documented on YouTube. A look-alike appeared on the Unityroom platform, and according to Japanese outlet AUTOMATON, the copier admitted feeding his videos to an AI. The knock-off even reached the platform's popular chart.

Clones copying clones

The article describes a messier scene on Steam. Earlier this year Valve began requiring developers to declare whether their games contain AI-generated content. It was meant as transparency for players. ifanr says it has become a box that mass-produced copies simply tick before going on sale.

Developer Nas posted a demo on August 22 of Needle In A Haystack Simulator, in which a player sifts through 5 million pieces of hay for one needle. Six days later he opened a Steam page. Before the game even launched, at least 8 similar games had appeared, and by mid-September the count passed 10. Another developer, NoGlyph, released a game on the same theme on September 29, then on October 17 accused a rival title of lifting his code. NoGlyph said it shared 13 identically named classes, and that over half of the related functions matched. He has filed a copyright complaint with Valve.

Copies can also hijack attention. When Lithuanian duo Lazy Flock showed Haunted Paws at Nintendo's Indie World showcase on October 28, Kotaku's Kenneth Shepard searched for it on Switch 2 and found Ghostly Whiskers instead. That game swaps the puppy for two kittens but keeps the same two-player haunted-house premise. It had been on sale since September, while the real game is not due until May 2027.

A chilling effect on sharing

The fear has changed behavior. According to ifanr, Digital Sun cancelled the public beta of its new game ReVamp and moved testing to private servers. Another developer switched his demo to a lottery system, and Lucas Pope, creator of Papers, Please, said he no longer dares discuss early ideas in public.

The legal footing is weak for small teams. Copyright follows the idea-expression split, which protects specific code, art and audio but not abstract gameplay and rules. Lawsuits are slow and costly, and ifanr notes that Valve's advice was to build a community and keep updating the game. The outlet calls that thin comfort for a tiny team living on savings.

There is a counterweight. Analyst Chris Zukowski observed that bulk-generated games still rarely reach the top of the rankings. At the October Steam Next Fest, the share of demos disclosing AI use rose from 21.2% earlier in the year to 34.4%. Yet only 2 of the 25 most popular demos, or 8%, disclosed it. ifanr's point is that copies may not reach the summit but can still trample the foothills where small teams live.

Too little, too late?

ifanr describes Anthropic's rule as a reactive patch that comes after the damage and cannot fix the underlying problem. It also has a cost, since honest developers get refused along with copiers. The article does not suggest other AI tools share the restriction.

The larger worry is the economics. If copying is cheaper and quicker than experimenting with original ideas, the incentive to publish work in progress shrinks. And if teams hide their ideas until release, players see fewer unfinished experiments that might have grown into something good.