Anthropic Tweaks Claude So It Won't Clone Your Game Anymore

Anthropic has quietly rewritten part of Claude's rulebook to stop the AI from building exact copies of existing video games, a response to growing anger from developers who say their work is being cloned wholesale with the help of coding assistants.

The change surfaced in Claude Opus 5.5's Claude Code tool, where a new entry under a rule labeled "tengu_heron_brook" now reads: "Do build original games, games in 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." The addition was first spotted by X user Chasm, with the find later reported by Game Developer.

Addy Osmani, a member of Anthropic's technical staff, confirmed the update directly. "We 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," he wrote in response to Chasm's post. Osmani was careful to draw a line between copying and building within a genre, noting that "original games, genre games, and games built from your own design are meant to keep working." He added that Anthropic would "continue to iterate to ensure that we're striking the right balance" and invited developers to flag cases where Claude incorrectly refuses to work on something that's actually theirs.

A tool good enough to cause a problem

The guardrail exists because Opus 5.5 turned out to be unusually effective at reverse engineering code. That capability has rippled well beyond indie game cloning: it's been used to rapidly decompile old console games and even played a role in jailbreaking the PS5. Useful for preservation and modding communities, but the same skill set makes it trivial to pull apart a small studio's demo and rebuild it under a different name.

That's exactly what's been happening, according to multiple reports from developers over the past several weeks. Studios have described seeing their games and demos copied closely enough that some have canceled planned public showcases entirely, worried that putting a demo in front of players also means putting it in front of anyone willing to reverse engineer the code.

The timing lines up with a broader shift on Steam itself. Low-effort game clones aren't new, but the scale has changed. At the most recent Steam Next Fest, the number of demos on display roughly doubled compared to the previous event, and AI-assisted titles accounted for most of that growth. A lot of what's showed up looks less like inspiration and more like direct imitation, sometimes down to the code.

Valve won't play gatekeeper

Valve has acknowledged the slop problem on its own platform, but the company has made clear it isn't interested in solving it by restricting what tools developers use. At Steam's Indie Connect event last week, Valve's Tom Giardino said the company doesn't want "to be gatekeepers telling developers which tools they should or shouldn't use."

Pressed on what Valve actually intends to do, Giardino didn't offer specifics, saying only that "making Steam a smarter and more dynamic platform is the starting point of our philosophy." His practical advice to developers worried about being cloned: build games that are harder to copy by continuing to add to them. "You need to keep growing your game by adding features, personality and creativity that stem from your own perspective," he said.

That advice lands a little awkwardly given how the games industry actually works right now. Many of the most influential releases of the past few years, Vampire Survivors, Balatro, Peak, are built on relatively simple core concepts. Simplicity isn't the problem. Those games spawned plenty of imitators too, and that's always been part of how game design evolves. The distinction developers are drawing is between riffing on an idea with your own execution and lifting a game's actual codebase. One is how the industry has always worked. The other is what Claude's new rule is aimed at stopping.

Anthropic's fix only addresses its own tool, and it's narrow by design: Claude is still expected to help build games in established genres or styles, just not pixel-for-pixel recreations passed off as something new. Whether that two-sentence addition meaningfully slows the flow of clones on Steam, or whether developers simply route around it with other AI tools, remains to be seen. Valve, for its part, still hasn't said what "smarter and more dynamic" actually looks like in practice.