Sometimes the biggest policy shifts in tech don't arrive with a blog post, a press event or a countdown timer. This one showed up as a short rule buried inside a coding tool, and it took a sharp-eyed user on X to notice it.
Anthropic has added two sentences to the prompt that runs Claude Code on its Opus 5.5 model. The aim is simple: stop the tool from rebuilding someone else's specific video game. The company has confirmed it, and the timing is no accident. Game developers have spent weeks complaining about a flood of AI-assisted knock-offs landing on Steam.
What the rule actually says
The wording has been reported in full by several outlets, and it comes in two halves. The first half is the reassuring one: Claude Code should happily build original games, games that belong to a genre, and games based on the user's own designs and assets. The second half is the one that bites. It tells the tool not to build a recreation of a specific existing game, and it closes the obvious loophole by saying that renaming the project or calling it original doesn't change the answer.
So a platformer in the spirit of a classic is fine. A pixel-for-pixel rebuild of one particular hit, with the title swapped, is not.
How it came to light
The rule was first spotted in late October by an X user going by Chasm, who found it inside Claude Code, tagged under an internal flag named tengu_heron_brook. It was later reported to have turned up independently in the code of a recent Claude Code build, which tells you it wasn't a one-off glitch. Gaming and tech outlets picked it up quickly.
Anthropic didn't issue its own announcement. Instead, Addy Osmani, a member of Anthropic's technical staff, replied publicly on X. His explanation was short: the two sentences were added to steer Claude Code away from recreating someone else's specific game, because using Claude to infringe intellectual property is against Anthropic's usage policy. He also said original and genre games should keep working, and invited developers to get in touch if the tool refuses something that is genuinely theirs.
Why now? Blame the Steam clone problem
Anyone following indie gaming this autumn knows the mood. Cheap, fast, AI-assisted copies of successful games have been appearing on Steam, sometimes within days of the original catching attention. In one widely shared case in October, a developer behind a clone of a viral game accused yet another studio of lifting their code almost wholesale, a clone of a clone, which says plenty about where things have got to.
Valve, which runs Steam, has so far leaned on disclosure rules for AI content and has suggested that developers do more to protect their own games. Developers say that doesn't solve the volume problem. One studio, best known for the Moonlighter series, has even delayed a public playtest of its next game because it fears a clone could beat it to launch.
Seen against that backdrop, Anthropic's move reads as a company trying to make sure its own tool isn't the one doing the copying.
The rule at a glance
| Detail | What is known |
|---|---|
| Where it applies | Claude Code, running on Opus 5.5 |
| Length | Two sentences added to the prompt |
| Internal flag | tengu_heron_brook |
| Confirmed by | Addy Osmani, Anthropic technical staff (via X) |
| Official reason | Infringing IP breaks Anthropic's usage policy |
| Still allowed | Original games, genre games, games from your own designs and assets |
| Not allowed | Recreating a specific existing game, even if renamed |
| Can users switch it off? | Reportedly no |
| Other models affected? | Not stated by Anthropic |
What a prompt rule can and can't do
Here is where it gets interesting, and where I'd urge a bit of caution before calling this a fix. The rule lives in the tool's prompt, not in the model's training. That makes it quick to ship and easy to adjust, but it's a soft control. A determined user can break a copy into many small requests that each look harmless, and a prompt for something "similar to" a famous game can drift towards a clone without ever asking for one.
There's also the question of where "inspired by" ends and "recreation of" begins. Game design has always borrowed. Entire genres exist because someone liked a mechanic and built on it. Anthropic hasn't published a test for this, so for now the line is drawn case by case, by the model.
The collateral damage developers are reporting
Broad rules tend to catch things they weren't aimed at. Some users say they've hit unexpected refusals in game-adjacent work that has nothing to do with cloning, including Windows crash dump analysis, cleaning junk software off a Samsung TV, anti-cheat work and a reverse-engineering tool. These are user reports rather than confirmed findings, and Anthropic hasn't commented on each one. Still, they show why developers are asking for clearer documentation.
What happens next
- Written policy. A broader update to Anthropic's usage policy is due to take effect on November 12, 2026, and coverage notes the game rule isn't part of it. Expect pressure to spell the principle out in public.
- Other AI coding tools. If one major player draws this line, rivals will be asked where they stand.
- The platforms. Steam and other storefronts still decide what gets listed. A tool-side rule helps, but it doesn't replace moderation.
- Courts and lawmakers. Game mechanics are famously hard to protect under copyright, while art, music and code are not. That gap is why this debate isn't going away.
Bottom line
Anthropic has drawn a small but visible line: Claude Code can help you make a game, but it shouldn't help you remake someone else's. For indie developers worried about copycats, it's a welcome signal, even if an imperfect one. For everyone building legitimately, the open question is how consistently the line will be applied. We'll be watching for the November 12 policy update and for any clarification from Anthropic.
Frequently asked questions
What is Anthropic's two-sentence game rule?
It's a pair of sentences added to Claude Code's prompt on Opus 5.5. One says the tool can build original games, genre games and games from the user's own designs and assets. The other says it shouldn't build a recreation of a specific existing game, even if the request renames it or calls it original.
Who confirmed the change?
Addy Osmani, a member of technical staff at Anthropic, confirmed it in a post on X around October 30, 2026. Anthropic did not publish a separate announcement.
Can I still make a game similar to another one with Claude Code?
Games within the same genre are meant to keep working. The rule targets recreations of one specific existing game. Anthropic hasn't publicly defined exactly where the line sits.
Does renaming a cloned game get around the rule?
No. The rule specifically says a renamed game, or one described as original, is still off limits if it recreates a specific existing title.
Can users turn the rule off?
Reports say there's no user-facing setting to disable it. It's delivered from Anthropic's side through a server flag.
Does the rule apply to every Claude model?
Anthropic has only said it was added for Claude Code on Opus 5.5. It hasn't said whether other models used inside Claude Code are affected.