Anthropic adds Opus 5.5 prompt rule against game cloning

The change surfaced through the AI decompilation community before Anthropic confirmed it. A user going by "chasm" noted the new rule, filed under the name "tengu_heron_brook," appeared in the Claude Code prompt on or around October 27, and XDA later verified it in version 2.1.314 of the binary released October 30. XDA also reported that Claude Opus 5.5 seemed to carry its own separate instructions restricting game recreations.

The backdrop is a surge in AI-assisted game porting and copying. Copies of game demos are making some developers afraid to show early work publicly, and thousands of AI-powered decompilation and porting projects for retro games now exist. The years-old decompilation community decomp.dev announced last month it was shutting down; maintainer Luke Street wrote that AI tools had broken the community aspect as newcomers raced to port games using decompilations they did not contribute to, turning a process where every fraction of a percent took real human effort into what he called a hollow numbers game.

The prompt raises hard line-drawing questions, such as whether AI mashups like adding Spider-Man to Batman: Arkham Knight count as recreations, or where a direct Tetris copy ends and a Tetris-genre game begins. Anthropic's Osmani said the company will keep iterating and asked users to send along cases where Claude turns down something that is theirs.