Epic Games has made the Unreal Engine 5.9 MegaJam Preview available. The company describes the release as the first Unreal Engine build constructed primarily with agentic workflows.
What happened?
According to the announcement on the Epic Developer Community forums, the preview was put together in about a week. A small group of engineers directed fleets of AI agents to port AI tooling from the Unreal Engine 6 development branch and to implement web as a target platform. The agents wrote the web platform code starting from the HTML5 platform retired in Unreal Engine 4, while engineers reviewed and tested the work.
The release was timed for the Epic AI MegaJam 2026, running November 12–15. Teams of up to five people can use as many AI agents as they like to build games in Unreal Engine or Unreal Editor for Fortnite, with standout entries eligible for grants of up to $50,000.
What's new?
Key experimental features include:
- Unreal Assistant: an in-editor panel that lets developers work with coding agents such as Claude Code, Codex, Cursor or OpenCode, connected to Unreal MCP.
- Expanded Unreal MCP: launches automatically with the editor and provides toolsets for rendering, source control, profiling, debugging, gameplay testing, geometry, audio, UI and level creation. Includes Lore integration and a Fab toolset to search and install assets.
- Unreal Canvas: a shared workspace for content creation with agents.
- Browser runtime: experimental support via WebAssembly and WebGPU based on the mobile renderer. Currently requires a source-built engine and a C++ project, and works best in Chrome.
Epic notes that the preview had a short development period and reduced QA. Some agent-written code is still being cleaned up, and the full stable 5.9 release is planned for 2027.
Why this matters
The fact that the engine release itself was built primarily by agents marks a practical turning point in tool development. Epic is using the preview both to deliver AI features in time for MegaJam and to learn how to scale development with multiple engineers directing swarms of agents in parallel, without diverting focus from Unreal Engine 6.
For developers, this means being able to use coding agents directly inside the editor for tasks ranging from level creation to installing Fab assets, with MCP providing structured access to editor tools.
What changes in practice
Anyone wanting to test should use a copy of their project, as the preview still has rough edges. Download is available through the Epic Games Launcher and on GitHub. Epic encourages experimentation during MegaJam and bug reports, since agents also help with triage and quick fixes.
The move reinforces Epic's direction of integrating AI deeply into the development workflow, consistent with recent statements about Unreal Engine 6. For the geek audience, it is a clear signal of how game creation tools are evolving in real time.
Image credit: Epic Games | Source: Unreal Engine / Epic Developer Community
By Grok
