Epic confirms AI vibe coding for Unreal Engine 6 and Fortnite

Epic Games confirmed on Oct. 28, 2026 that it is using AI-driven vibe coding for Unreal Engine 6 and future Fortnite updates, executive vice president of development Marcus Wassmer said in a statement to This Week In Video Games. The confirmation marks a shift from last year, when Chief Executive Tim Sweeney denied Epic was using AI tools for Unreal Engine updates. Sweeney’s previous denial meant Epic had publicly distanced itself from AI use in Unreal Engine development before reversing course in 2026. Sweeney confirmed on Sunday that Epic is using AI tools to develop code for the engine.

Epic uses AI tools including Claude Code and Codex across its backend, engine, and game development engineering teams. The June Unreal Engine 6 blog post and later statements identified these two tools as central to Epic’s AI-assisted engineering work. Claude Code and Codex are AI coding assistants that generate software code.

Nearly all current development occurs in the dev streams tied to Fortnite, Unreal Editor for Fortnite, and UE6, Wassmer said. The statement indicated current development work concentrates across Fortnite-related and UE6 streams rather than spreading across older engine branches.

Epic does not think a halfway approach to AI in development is viable and prefers to be up front, share best practices, and make the best UE6 with the best tools available. Wassmer said transparency and full adoption were preferable to partial AI integration as Epic builds Unreal Engine 6.

Wassmer said Epic is more concerned about the risks of moving too slowly than it is about AI skepticism. He claimed AI tools would help Epic push out updates faster and with fewer bugs. Eurogamer reported Wassmer’s claim as part of Epic’s justification for expanding AI use across Fortnite and UE6. Wassmer said Epic is not one-shotting the engine but is iterating with AI to ship features developers want while keeping the engine within memory, performance, and scalability envelopes.

The AI tools have almost eliminated non-deterministic cooking bugs that Epic had been fighting for a decade. Wassmer cited the bug fix as one of the major recent efficiency gains from using AI coding tools across Epic’s engineering teams. Non-deterministic cooking bugs are errors that appear inconsistently when developers build game content.

AI also accelerated shader compression work, which reduces patch sizes. Shader compression improvements and cooking bug elimination are ways AI is reducing patch sizes and speeding development.

Wassmer said a major section of the D3D12 rendering layer finished in about one week after he had estimated the task would take three to six weeks for one engineer. D3D12 is a graphics application programming interface used to render games.

AI tools help keep Epic’s internal test suites healthy and expand those test suites for more coverage. Wassmer listed test suite maintenance and expansion among the broad development work supported by Claude Code and Codex. The company can now attempt larger architectural refactors with AI than possible due to the amount of file changes required. Rock Paper Shotgun reported Wassmer’s comment that AI enables refactors impractical because of the volume of file changes involved.

Epic has started using automatic PC stability monitoring on Fortnite to spot issues with specific driver and hardware pairings, together with automatic root cause analysis and fix generation. Wassmer said these systems detect driver and hardware issues that took months to diagnose and are improving long-standing PC problems in Fortnite and Unreal Engine.

Epic revealed earlier this month that it vibe-coded a new version of the Epic Games Store launcher, describing it as faster, more responsive, and with a new look. Epic’s own post described the launcher work as vibe coding because programming is hard, presenting it as an example of the company’s AI approach.

The launcher starts from a cold boot 46 percent faster than Steam and delivers a 14 percent performance boost when restored from the system tray. GamingBolt reported these performance claims alongside charts comparing the new launcher to Steam’s storefront in October 2026. Shortly after the launcher reveal, social media showed clips of the launcher hallucinating, and one poster claimed the new launcher bricked their PC. According to Polygon, Epic said its launcher booted faster than Steam, though Valve later issued a store update that erased the advantage. Polygon reported that the launcher issues appeared shortly after Epic touted its speed advantage over Steam. This launcher claim was part of a series of AI-related announcements Epic made in October 2026 before the Unreal Engine 6 confirmation.

In June, Epic said it was still investigating what works and what does not work for code generation with AI. The June investigation preceded the October confirmation that AI code generation is now broadly used across Epic’s development streams.

The next engine version will combine Unreal Engine 5 with Unreal Editor for Fortnite. GamingBolt reported Wassmer’s June statement that the next engine version would merge the main engine line with the Fortnite editor.

Epic announced an AI game jam shortly before walking back the AI requirement, and the week before the game jam, the company said it had vibe coded the Epic Games Launcher to be faster than the other guy.

Sweeney said he believes a golden age of gaming is imminent because of generative AI technology. Polygon listed this among pro-AI statements Sweeney made in recent months alongside his criticism of Steam’s AI disclosure rules.

He repeatedly criticized Steam’s inclusion of AI disclosures as a political act that confiscates opportunity from developers. Epic’s CEO has opposed Valve’s policy requiring developers to disclose generative AI use on Steam store pages, calling it partisan and harmful.

Sweeney said it is abhorrent to force developers to write a political statement that a hate mob could use against them. Yahoo Tech and GamingBolt connected these remarks to Sweeney’s opposition to Steam’s requirement that developers disclose generative AI use on store pages.

Epic Games welcomes projects that make use of generative AI technology. Yahoo Tech said being open about vibe coding lets PC gamers decide for themselves whether to engage with a game. GamingBolt reported Sweeney’s statement alongside his criticism of Valve’s AI disclosure policy in October 2026. Yahoo Tech argued that Epic’s openness about vibe coding gives players information to decide whether to support its games.

Workers worry about job security, developers worry about plagiarism, and communities worry about the environmental impact of Epic’s generative AI push. Eurogamer noted these concerns even as Epic appeared unconcerned about the divisive reaction to its generative AI strategy.

Game developers have reacted with alarm to reports that Unreal Engine 6 is AI vibe-coded and might not be understood by Epic. Polygon reported that the idea of an AI-vibe-coded engine caused concern among developers who questioned whether Epic understands the resulting code.

Others said there is little reason developers do not just vibe-code their own engine instead of paying Epic’s hefty licensing fees. Some developers suggested Epic’s licensing model loses appeal if teams can build their own engines using AI coding tools.

Polygon reported that many players still care whether humans or an LLM made game art assets and writing, while some gamers are becoming more comfortable with AI in games. Polygon noted that audience attitudes remain mixed, with some players still valuing human-created assets and writing while others grow more accepting of AI in games. LLM stands for large language model, an AI that generates text.

Epic recently delayed an unannounced Marvel and Star Wars crossover game while shifting to an AI-first development approach. The delay occurred as Epic reorganized its development around generative AI tools and workflows across its projects. A director on the delayed game reportedly told staff there would be no more handwritten code, and AI would generate all art with full AI workflows. The report indicated the game would abandon traditional programming in favor of AI-generated assets and code under the new approach.

Developers working on a troubled Disney and Marvel shooter were reportedly told to let generative AI handle code and art production. Eurogamer reported this as an example of generative AI applied to code and art production in a troubled shooter project.