Anthropic has confirmed that it added a restriction to the system prompt used by Opus 5.5 in Claude Code, steering the model away from recreating other people's specific games. The change was first spotted by a user on X. The games-industry outlet Game Developer then asked Anthropic about it, and a company spokesperson pointed the reporter to a public explanation posted on X by Addy Osmani, a member of Anthropic's technical staff.
According to Game Developer, the rule shipped with a Claude Code update on October 27 under the internal codename tengu_heron_brook. Its core sentence reads:
"Do not build a recreation of a specific existing game, even if it is renamed or called original."
In other words, the model should not clone a particular existing game, even if the clone is renamed or described as an original.
How Anthropic explains it
Osmani said the team added two sentences to the Opus 5.5 Claude Code prompt so that the model avoids recreating other people's specific games, on the grounds that infringing intellectual property through Claude violates the usage policy. He listed what is not affected: original games, genre games (for example a platformer or a match-three), and games built with the user's own designs and assets.
He added that the team will keep tuning the rule to find the right balance, and that users whose work gets refused can send feedback to him directly. According to the person who found it, users cannot switch the rule off themselves. Anthropic has not said whether it will extend to other Claude products or to API calls.
Why developers care
The rule arrives amid anxiety in the indie game scene about fast AI-made copies. Game Developer noted that Digital Sun Games, the studio behind ReVamp, cancelled a planned public playtest out of concern that a demo fed into AI tools could quickly spawn knockoffs, and that several other studios made the same call. Developers are also asking Valve how Steam intends to keep such clones off the store.
The report is equally clear about the rule's limits. Public workarounds already exist for prompt-level restrictions, and software has a hard time telling whether a user really owns an idea or an asset, so what gets stopped is mostly the cheapest tier of copycats. One reader comment pointed out that anyone who is blocked can simply switch to an open-weight model without such restrictions.
What it means for developers in China
For developers in China, the impact falls mainly on workflow. Reskinning has long been a common tactic on mini-game platforms: swap the art, tweak the numbers, keep the core gameplay. Under the boundary Anthropic described, asking for "a tower defense game" or "a merge game" counts as a genre game and should go through, while explicitly asking for a one-to-one build of a particular hit game would be refused.
The middle ground is the hardest to call. If someone describes another game's level structure, UI layout and numeric tables item by item and then asks the model to implement them, is that a recreation? The rule offers no standard, so for now it depends on how the model reads the specific conversation.
Another concern is stability for commercial users. Teams that use Claude Code for outsourced projects or internal tools face rules that change with prompt updates, so a request that passes today may be refused in the next version. Osmani said the team will keep iterating, so the actual criteria will have to be judged from how later versions behave, and Anthropic has not published any statistics on refused requests.
Sources: Game Developer, CocoLoop, public statement by Anthropic technical staff member Addy Osmani; the rule wording, applicable model and unrestricted scope were checked.