Anthropic has tightened Claude Code’s instructions to stop users from rebuilding particular existing video games, as AI-assisted ports, decompilations and lookalike projects spread rapidly through the retro-gaming scene.

The change surfaced late last week, when a user posted what appeared to be two additions to Claude Code’s system prompt. One instruction set permits “original games, games in a genre, and games from the user’s own designs and assets,” but says: “Don’t build a recreation of a specific existing game, even if it is named or called original.”¹

Anthropic software engineer Addy Osmani subsequently confirmed the company had added two sentences to the Claude Code prompt for Opus 5.5. The purpose, he said, was “to steer it away from recreating someone else’s specific game because using Claude to infringe IP is against our usage policy.”¹ He said legitimate original, genre-based and user-owned projects were meant to continue working, while inviting reports of mistaken refusals.

The restriction was later independently found in version 2.1.314 of the Claude Code binary, released on October 30, according to reporting that also identified separate Opus 5.5 instructions addressing game recreations.²

The immediate effect may be more legal than cultural. The broader AI-copying wave has already helped turn arduous game decompilation and porting work into a far faster process, contributing to decomp.dev’s decision to close after its community said the collaborative ethos had been overwhelmed by token-fuelled port races.²

Critics of the safeguard argue that determined users can move to other frontier systems or open-weight models with no comparable limits. They also warn that Claude may struggle to distinguish a forbidden near-replica from a permissible genre game or a more transformative mashup. In that view, Anthropic has erected a useful corporate boundary—but hardly a seawall against the copying boom.