Key facts
- Anthropic software engineer Addy Osmani said the two-sentence prompt change aims to stop Claude recreating someone else's specific game.
- Osmani said original games, genre games and games built from a user's own designs and assets are meant to keep working.
- The rule, filed under the name tengu_heron_brook, tells Claude to build original games but not recreate a specific existing game.
- XDA reported the rule appears in Claude Code version 2.1.314, released on October 30, 2026.
- Community maintainer Luke Street said AI tools had broken the community aspect of decompilation at decomp.dev.
Anthropic added two sentences to the Claude Code prompt on its Opus 5.5 model to steer the tool away from recreating specific existing video games, Anthropic software engineer Addy Osmani said on October 30, 2026. Osmani said using Claude to infringe intellectual property is against the company's usage policy, and that original games, genre games and games built from a user's own designs and assets are meant to keep working.
A social media user and AI decompilation enthusiast going by the name chasm was among the first to note the prompt change late last week, saying a new rule appeared in the Claude Code prompt on or around October 27. The rule, included in a json file under the name tengu_heron_brook, tells the model to build original games, games in a genre and games from the user's own designs and assets, but not to build a recreation of a specific existing game even if it is renamed or called original. XDA later independently verified that the rule appears in version 2.1.314 of the Claude Code binary, released on October 30, and reported that the rule had been used for other purposes in earlier versions and that the Claude Opus 5.5 model seemed to have its own distinct instructions restricting game recreations.
A handful of issue reports on Anthropic's GitHub suggest the new prompt is getting in the way of some game development use cases, according to the report. The change comes as AI coding tools power a wave of game projects based on existing work, including copies of game demos and thousands of AI-powered decompilation and porting projects for retro games.
decomp.dev, a years-old community devoted to game decompilation, announced it was shutting down last month. Community maintainer Luke Street wrote that quickly improving AI tools had made clear that the community aspect of decompilation had been broken as newcomers raced to port games, especially using decompilations they did not contribute to.
The report said the prompt is unlikely to have much impact overall because game copiers can shift to other frontier models without such restrictions, or to cheaper open-weight models that are not subject to these restrictions and are not far behind in capabilities. The prompt may have a more immediate benefit for Anthropic itself, helping protect the company from potential liability from copyright infringement in these projects, the report said.