Unreal Engine 5.9 Preview is the first engine release built mostly by AI agents
nicolascraske · x · 2026-11-11
Epic Games shipped the Unreal Engine 5.9 Preview—its first engine release built primarily with agentic workflows—assembled in roughly a week for the 2026 Epic AI MegaJam (Nov 12-15).
- A handful of engineers directed fleets of parallel agents to port AI tooling from the UE6 branch and implement Web as a target platform, starting from UE4's retired HTML5 code; agents wrote the code while engineers directed, reviewed, and tested.
- Epic says the approach lets it deliver more UE5 releases with faster bug fixes without pulling focus from UE6, though it's still cleaning up agent-written code and some web renderer parts are prototypes to refactor before 5.9 ships.
- The preview also adds AI workflow enhancements, running projects in a browser, and rendering/animation updates.
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