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Epic Games vibe-coding now extends to Fortnite, Unreal Editor for Fortnite (UEFN) and Unreal Engine 6, its next numbered engine release. Marcus Wassmer, Epic's executive vice president of development, said AI tools now produce most of the code while engineers steer them toward the architecture they want. Vibe-coding, as he described it, means directing AI tools rather than typing code by hand. He argued the approach will ship updates faster and with fewer bugs. Epic now treats slow progress as a bigger danger than the backlash, Wassmer said in an interview, as first reported by This Week In Video Games.
That means our engineers are no longer writing the bulk of the code, but they are still guiding the tools to get the architectural result we want.
Marcus Wassmer, executive vice president of development, Epic Games
Key takeaways
- Most code now comes from AI: Marcus Wassmer, Epic's executive vice president of development, said Epic engineers no longer write most of the code for Unreal Engine work and instead guide AI tools toward the architecture they want.
- UE6 is part of the push: Wassmer said almost all of Epic's current development runs in the dev streams for Fortnite, UEFN and Unreal Engine 6.
- Speed over skepticism: Wassmer said Epic worries more about moving too slowly than about AI skepticism, and called a halfway approach to AI unviable.
- Fight over Steam disclosure: Epic CEO Tim Sweeney called Valve's rule asking developers to disclose generative AI use on Steam pages abhorrent.
Table of contents
What Vibe-Coding Unreal Engine 6 Means at Epic
Wassmer confirmed that Epic is "definitely using AI to develop code and features for Unreal Engine," and said the work extends into UE6. He placed nearly all current work in three places: "Almost all development happening right now is being done in the dev streams attached to Fortnite, UEFN [Unreal Editor for Fortnite], and UE6."
Asked directly whether Epic is vibe-coding anything tied to Unreal Engine, he said yes. He stressed that the iteration is meant to keep the engine inside its memory, performance and scalability limits, rather than "one-shotting" it from a single request.
Those limits matter because studios outside Epic build on Unreal Engine. Those developers will be the ones to test whether AI-written code stays inside the bounds Wassmer set.
Why Epic Fears Moving Slowly More Than Its Critics
Epic is pressing ahead despite criticism from several directions. Workers fear for their jobs, developers worry about AI copying their work, and communities around the world have raised the environmental cost of the technology.
Wassmer framed the trade-off bluntly, saying Epic is "more concerned about the risks of moving too slowly than we are about AI skepticism." He also rejected any middle path: "We don't think it's viable to take a halfway approach to AI in development."
His stated plan is openness: be up front about the work, share best practices with other developers, and use the strongest tools available at each stage to build UE6. Wassmer's remarks do not address the plagiarism or energy concerns, so those questions remain open.
How the Launcher and the Steam Row Fit the Pattern
Epic has already taken the same method beyond the engine, using it to rebuild its Epic Games Launcher with the goal of running a touch quicker than Steam. At the time, Epic's explanation was blunt: "Prograaming is hard," it said, and so it had vibe coded the launcher instead.
Eurogamer has separately reported that a team building a troubled Disney and Marvel shooter was instructed to hand code and art production to generative AI.
Tim Sweeney, Epic's chief executive, has also attacked Valve's Steam policy asking developers to disclose generative AI use on their store pages. He wrote that "forcing developers to write a political statement to be used against them by the hate mod they're helping organize is abhorrent." Epic is plainly digging in.
| Project | AI use described | Who said it |
|---|---|---|
| Unreal Engine and UE6 | AI writes most code; engineers guide architecture | Marcus Wassmer |
| Fortnite and UEFN | Almost all current development in their dev streams | Marcus Wassmer |
| Epic Games Launcher | Vibe-coded to run slightly faster than Steam | Epic Games |
| Disney and Marvel shooter | Team told to use AI for code and art | Eurogamer reporting |
| Steam AI disclosure rule | Opposed by Epic | Tim Sweeney |
The case for and against Epic's AI bet
The case for
- Wassmer says AI tools will let Epic ship Unreal Engine updates faster and with fewer bugs.
- Engineers still guide architecture, which Wassmer says keeps UE6 within memory, performance and scalability targets.
- Epic has pledged to share best practices with other developers building on the engine.
The case against
- Epic has given no measurements to support its speed and bug-reduction claims.
- Workers fear job losses and developers worry about plagiarism, concerns Wassmer did not address.
- Tim Sweeney's opposition to Steam disclosure rules makes AI use in games harder for players to see.
What to be careful about
- Studios building on UE6 inherit any defects that AI-generated engine code introduces.
- Epic engineers face job-security pressure as AI tools take over most code writing.
- Epic's clash with Valve over Steam disclosure could deepen distrust among developers and players.
The bottom line
Epic has made its bet. Its development chief says most new code across Fortnite, UEFN and UE6 now comes from AI tools under engineer supervision, and its chief executive is fighting the disclosure rules that would make such work visible on Steam. What remains unproven is the payoff. Wassmer promised faster updates and fewer bugs, but he offered no measurements, and no UE6 release date was given. Unreal Engine users will be the test. If UE6 lands inside the memory, performance and scalability targets Wassmer described, Epic's argument gains weight. If it does not, the skeptics he set aside will have their evidence.
What to watch
- Watch for Epic to announce a release date for Unreal Engine 6; Wassmer gave none.
- Watch whether Valve changes its Steam rule asking developers to disclose generative AI use after Tim Sweeney's attack on it; no date has been set.
- Watch for news on the troubled Disney and Marvel shooter whose team was told to use AI for code and art; no new schedule has been given.
Frequently asked questions
Is Unreal Engine 6 being written by AI?
Partly. Marcus Wassmer said Epic is using AI to develop code and features for Unreal Engine, including UE6, with engineers guiding the tools rather than writing most of the code themselves.
What does vibe-coding mean at Epic Games?
Wassmer described it as AI tools producing the bulk of the code while engineers steer toward the architecture Epic wants. He said Epic iterates with the tools rather than one-shotting the engine.
Why does Tim Sweeney oppose Steam's AI disclosure rule?
Valve asks developers to disclose generative AI use on their Steam pages. Epic CEO Tim Sweeney argued that forcing such statements hands critics material to use against developers, and called the requirement abhorrent.
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