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Report / Published 2026-10-29

Epic says its engineers no longer write most of the code

Epic's development chief confirmed AI tools are used across Fortnite, UEFN and Unreal Engine 6, named Claude Code and Codex, and said engineers now guide tools rather than write the bulk of the code.

Q.QIBA Gaming deskSource-backed article · 4 min read
Event date Prepared Published 2026-10-29
A wooden workbench lit by a single desk lamp, with a blank sheet of paper, pencils in a cup, loose screws and a small toolbox, all in deep blue shadow.
Conceptual editorial illustration; not a screenshot or a depiction of Epic's tools.

THE SHORT VERSION

  • Epic executive vice president of development Marcus Wassmer said the company is using AI to develop code and features for Unreal Engine, with almost all current development happening in the dev streams attached to Fortnite, UEFN and UE6.
  • He said Epic is "vibe-coding" and that engineers no longer write the bulk of the code, naming Claude Code and Codex among the tools, while saying the studio is not one-shotting the engine and still guards memory, performance and scalability.
  • Epic cites wins including the near elimination of non-deterministic cooking bugs, faster shader compression and a D3D12 rendering-layer rewrite finished in about a week; neither report independently verifies those productivity claims.

What Epic confirmed, and who said it

Epic Games executive vice president of development Marcus Wassmer told This Week In Video Games that the company is "definitely using AI to develop code and features for Unreal Engine", according to Eurogamer. He also said that "almost all development happening right now is being done in the dev streams attached to Fortnite, UEFN and UE6", which puts the next numbered engine and the Fortnite ecosystem in the same sentence.

The quote that travelled is blunter. Asked whether Epic is vibe-coding Unreal Engine work, Wassmer said: "Yes, we are vibe-coding things. 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." PC Gamer also points to Tim Sweeney's earlier post on X confirming the company now uses AI tools to develop Unreal Engine code. The two outlets agree on the confirmation and differ mainly in which quotes they lead with.

The tools, and the specific wins Epic cites

PC Gamer names two tools Wassmer cited: Claude Code and Codex. It also carries his examples of where the work shows up, which are narrower and more checkable than the headline: the near-complete elimination of non-deterministic cooking bugs the studio had fought for a decade, faster work on shader compression that reduces patch sizes, and a rewrite of a significant part of the D3D12 rendering layer.

The D3D12 example is the most concrete. Wassmer estimated the rewrite would take a single engineer three to six weeks and said it was completed in about one week, with better CPU time and fewer bugs. Those are production claims from the company rather than measured results published for outside review, and neither outlet reports independent verification of the time saved or the bug counts.

The limits Epic puts on the claim

Wassmer's statement includes its own caveats. He said Epic is "not one-shotting the engine" and that the team iterates with AI to ship features, keeping the engine inside the memory, performance and scalability envelopes developers rely on. Eurogamer also reports his claim that the tools help push updates faster with fewer bugs.

The company's broader argument is about approach rather than a single result. Wassmer said Epic is "more concerned about the risks of moving too slowly than we are about AI skepticism", and that a halfway approach is not viable, with the quality of the games and tools offered as the answer to doubt. That is a position statement; it does not establish that the code Epic ships is better, only that the studio believes the trade is worth it.

The dispute around disclosure

The timing sits inside a public fight about disclosure. PC Gamer reports that Sweeney argued against Steam's requirement that developers disclose generative-AI use, calling the statements "just as partisan as mandatory political essays" and saying forcing developers to write a political statement that can be used against them is abhorrent. Eurogamer frames the same dispute and notes Epic is unlikely to soften after that exchange.

There is more than one objection in the air. Eurogamer lists workers worried about job security, developers worried about plagiarism and communities worried about environmental impact, and notes the divisive reaction to Epic's push. None of those concerns is answered by a productivity claim; they are separate questions about labour, attribution and cost that the two reports raise without resolving. Neither report says whether Epic has changed how it documents generated code, which is the detail a developer would need to judge the practice.

This is not Epic's first announcement

The confirmation follows a run of smaller disclosures. Eurogamer recalls that Epic said it had vibe-coded the latest Epic Games Launcher to run faster than Steam, and that developers on a troubled Disney and Marvel shooter were reportedly told to let generative AI handle code and art. PC Gamer adds the AI game jam and a walked-back AI requirement, and notes a June Unreal Engine 6 post in which Wassmer described broad usage for code generation across backend, engine and game engineering teams.

Read together, the reports describe a company that has been signalling this direction for months and is now stating it plainly. The site's other files on the surrounding policy fight, including Valve's response to AI cloning on Steam and Fortnitemares 2026, cover the storefront and live-game sides of the same period, while Deadlock's city update is a reminder that other studios are shipping on the same platforms without making the same disclosure.

What would make the claim checkable

The claims would become testable in three places: Unreal Engine 6's ship date and stability at release, the patch sizes Epic ships for Fortnite and UEFN, and whether the studio publishes any defect or performance data rather than time-saved anecdotes. None of that exists in these two reports, which rely on the company's own account of its workflow. A public postmortem or a defect trend would move the argument from anecdote to evidence.

For developers, the practical question is different from the headline. If most code is generated, the review burden moves to the people guiding the tools, and the relevant signals become how Epic documents generated code, how it handles licensing and attribution, and whether its disclosure practices change. Neither outlet answers those; they establish what Epic said and what it did not show.

Sources & reporting limits

  1. Epic Games further doubles down on gen-AI tools for Fortnite, Unreal Engine 6 and more: "Our engineers are no longer writing the bulk of the code"
  2. 'Yes, we are vibe-coding things': Epic confirms it's using AI tools to code Unreal Engine 6, Fortnite, and more
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