On October 23, 2026, Epic Games CEO Tim Sweeney said the company was using AI tools to develop Unreal Engine code. Development executive Marcus Wassmer described the process as engineer-guided work across projects tied to Unreal Engine 6 (UE6), Fortnite and Unreal Editor for Fortnite (UEFN), with AI writing much of the code and engineers directing the architecture and revising the results.
That makes Epic’s account about AI-assisted engineering, not a hands-off engine rewrite. Wassmer named Claude Code and Codex as tools in use and said engineers keep the work within memory, performance and scalability limits.
What Epic says its engineers are doing
In the detailed account of Epic’s development practices, Wassmer said nearly all development was happening in workstreams attached to Fortnite, UEFN and UE6. The June 2026 UE6 roadmap had described broad internal use of code generation and AI analysis across backend, engine and game-development engineering teams. At the time, Epic said most of those code-generation uses were not producing mainline Unreal Engine code.
The two descriptions cover different points in time and different scopes. The June roadmap described the broader internal program; Wassmer later discussed AI-assisted work in engine and game-development streams.
Wassmer said engineers guide AI tools toward the intended architecture, review and iterate on their output, and keep the engine within technical constraints. He also said AI was writing the bulk of the code. The tools therefore contribute to implementation while engineers remain responsible for steering the work and its engineering requirements.
NeoTeo previously covered a separate AI-assisted effort involving the Epic Games Launcher. Wassmer’s examples here concern engineering work tied to Unreal Engine, Fortnite and UEFN.
Testing, stability work and a D3D12 rewrite
Wassmer described AI use beyond code generation. He said it helped Epic expand internal test coverage, analyze bugs and refactor larger parts of the engine. For Fortnite on PC, he described automated stability monitoring that identifies problems associated with particular driver and hardware combinations, alongside automated root-cause analysis and fix generation.
Wassmer also reported that AI-assisted work had nearly eliminated non-deterministic cooking bugs, which can appear inconsistently, after Epic had struggled with them for a decade. He said AI accelerated shader-compression work that reduced patch sizes. These are his descriptions of Epic’s results, not general performance guarantees.
One concrete example was a substantial rewrite of the Direct3D 12 (D3D12) rendering layer. Wassmer said it took about one week, compared with his estimate of three to six weeks for one engineer. He also reported improved CPU time and fewer bugs, without giving numerical results for those changes. The time comparison describes this rewrite, not a general speedup for AI-assisted programming.
UE6’s planned AI tools and target schedule
Epic’s June 22, 2026 roadmap described developer-facing AI features planned for UE6. One is a Model Context Protocol (MCP) foundation intended to connect the development pipeline with models such as Claude and Gemini. The roadmap also described Epic Developer Assistant as an optional turnkey tool available by default.
The roadmap targeted UE6 Early Access for the end of 2027, with a full release planned 12 to 18 months later. Epic also said UE6’s gameplay programming model would move to Verse, which can call C++ code.
These developer-facing plans are separate from the internal tools Wassmer named. He identified Claude Code and Codex in use at Epic; the roadmap’s MCP integrations and Epic Developer Assistant are planned UE6 features.
