Claude Code builds an Unreal prototype through the CLI without opening the editor

• An Unreal prototype was built entirely through Claude Code and the CLI, without opening the editor, according to the creator's demo post.
• The build used C++ without Blueprints, while its character and animations came from Fab.
• A Windows batch launcher let both the creator and the coding agent open game previews.

A Windows batch file is the wonderfully unglamorous centerpiece: the agent could use the same launcher as its creator. Epic already documents running a project in game mode through UnrealEditor.exe, without the full editor UI.

Danny Limanseta says he spent the weekend experimenting with Unreal, an engine he'd associated with AAA game development. Once setup was done, he found it “pretty vibe-code friendly,” as he put it in the demo thread.

He confirmed that the build used C++ and said no Blueprints were involved. His post leaves the initial setup unspecified.

Limanseta says he asked Opus 5.5 to create a .bat file for previews. He described two ways to use it:

• Double-click the file to preview the game himself.
• Let the agent use the same file to launch a preview.

Epic's separate documented example runs a project in game mode:

That example still uses the Unreal editor executable, with a flag controlling its startup mode. Limanseta's replies describe his launcher but don't include its contents.

The character and animations were downloaded from Fab, Limanseta explained. He also pointed to Unreal's free character-movement animations and separately praised its mannequin animations.

Epic offers a separate Game Animation Sample on Fab. Its original announcement describes more than 500 free animations, plus a working character and animation Blueprint; Limanseta doesn't identify that sample as the one he used.

Limanseta has also described making games with AI as a way to bring his ideas to life without relying on anyone else. “And on top of that, the whole process is so fun,” he wrote.