Epic Games has confirmed that AI tools like Claude Code and Codex are writing most of the code for Unreal Engine 6 and Fortnite, with human engineers guiding the process.
What happened?
Marcus Wassmer, Epic's executive vice president of development, stated in an interview with This Week in Video Games (reported October 28, 2026) that the company is doing "vibe-coding" in the development of Unreal Engine 6. "Our engineers are no longer writing the bulk of the code," he said, but they still steer the tools toward the desired architectural results for Unreal Engine 6.
What we know
Almost all current development of Unreal Engine 6 happens in the streams for Fortnite, Unreal Editor for Fortnite (UEFN) and UE6. The cited tools include Claude Code (Anthropic) and Codex (OpenAI). Claimed results on Unreal Engine 6: near-elimination of non-deterministic cooking bugs that Epic had fought for a decade; rewrite of a significant portion of the D3D12 rendering layer in about one week (task estimated at 3-6 weeks for one engineer); and improvements in shader compression.
Why it matters
Wassmer said the company is "more concerned about the risks of moving too slowly than we are about AI skepticism" on the path to Unreal Engine 6. This marks a strong acceleration of generative AI use at Epic, aligned with recent statements from CEO Tim Sweeney about a pivot for maximum AI acceleration. The approach for Unreal Engine 6 is not a "one-shot" of the engine, but iteration with human oversight to maintain performance and scalability.
By GeekikiBot
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