Anthropic has confirmed it added two sentences to the Claude Code prompt on Opus 5.5, instructing the tool to build original games and refuse recreations of specific existing games. The rule surfaced under the internal name tengu_heron_brook after weeks of indie developers pulling public demos over fears that AI clones would beat their own games to market.
Nobody announced it. An X user named Chasm found the change sitting inside Claude Code this week: a new rule, pushed around October 27 under the internal name tengu_heron_brook, that tells the tool to stop rebuilding other people’s games. Anthropic has since confirmed the rule is real.
The Announcement
The rule itself is short. It 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.” Chasm reports there is no way to switch it off.
Anthropic gave its confirmation through a post on X by Addy Osmani, a member of its technical staff. A company spokesperson pointed Game Developer to that post when asked about the change.
“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,” Osmani wrote. “Original games, genre games, and games built from your own designs and assets are meant to keep working. We’ll continue to iterate to ensure we’re striking the right balance.”
Osmani added an open door for mistakes: “In the meantime, if Claude turns down something that’s yours, send it my way.” Game Developer published the story on October 30 and updated it the same day with the Anthropic confirmation.
Important Details
| Item | Detail |
|---|---|
| The rule | Build original games; do not recreate a specific existing game |
| Internal name | tengu_heron_brook |
| Spotted | Pushed around October 27, posted by X user Chasm on October 30 |
| Model named by Anthropic | Opus 5.5, in the Claude Code prompt |
| Confirmation | Addy Osmani, Anthropic technical staff, on X |
| Way to disable it | None, according to Chasm |
| Still allowed | Original games, genre games, games from your own designs and assets |
The backdrop is a frightened indie scene. Developers have spent recent weeks worried that a public demo can be fed into an AI tool and cloned, with the copy reaching the store before the original ships. Aftermath has covered several studios reaching that conclusion.
Digital Sun Games, the studio behind Moonlighter, cancelled the public playtest of its upcoming game ReVamp and moved testing to a smaller Discord group. The studio wrote: “We’ve been concerned by recent news of games being reverse-engineered, cloned, and published before the original is even out.” Publisher Alliance Arts cancelled a planned demo of Drunken Goddess Reflux over the same fear, as Aftermath reported.
The pressure has also reached the storefront. At Steam Indie Connect in South Korea on October 27, Valve staff Tom Giardino and Marc Wilkinson told developers the company will not police which tools a studio uses, AI included, according to Inven Global reporting on the session. Valve’s stated defence against clones is community trust and steady updates, not a ban on the tools that make cloning fast.
What Is Next
The confirmed part is narrow: two sentences now sit in the Claude Code prompt on Opus 5.5, and Anthropic says it will keep adjusting them. The company has not said whether the same wording applies to other models, and it has not published the rule in a changelog or a policy page.
The limits are just as clear. A prompt rule is an instruction, not a lock, and researchers and reporters have repeatedly shown that limits inside a prompt can be talked around. Claude also has no reliable way to judge who owns a game idea or a pile of assets, which is why Osmani is personally collecting cases where the tool refuses work that belongs to the person asking.
The bigger hole sits outside Anthropic entirely. Nothing stops a cloner from moving the same request to an open weight model that carries no such rule, as users replying to Chasm were quick to point out. Whether rival labs follow with rules of their own, and whether Valve adds any store level protection beyond discovery tweaks, are open questions. For now, the most honest reading is that Anthropic has made the polite path slower for copycats, and the determined ones will simply change tools.
Sources
- Game Developer: Anthropic tells Claude to stop remaking video games
- Aftermath: Game Developers Fear That Thieving AI Vibecoders Will Make Free Game Demos A Thing Of The Past
- Inven Global: Developers Fear AI Slop and Clones, Valve Answers Directly
- Video Games Chronicle: ReVamp developer cancels public playtest in case AI users reverse engineer it and publish a clone first
- Illustration: Dirty Static
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