Epic Games has released a preview build of Unreal Engine 5.9, which it calls the “MegaJam Preview.” According to the studio, it is the first Unreal Engine release built primarily with agentic workflows. The preview is available through the Epic Games Launcher and GitHub, with a separate download option for Linux.
According to information Oyun Günlüğü obtained from Epic Games’ official developer forums, the company had been accumulating rendering and animation changes for a full 5.9 release planned for next year. However, just a week ago, the team decided to put together a preview in time for the 2026 Epic AI MegaJam, taking place on November 12–15. A handful of people directed groups of AI agents to port the AI tooling from the UE6 development branch and to implement web as a target platform. The agents wrote the web platform code starting from Unreal Engine 4’s retired HTML5 platform, while engineers directed, reviewed and tested the work.
Epic Games says this approach allows it to deliver more UE5 releases with faster bug fixes and focused feature work without pulling attention away from UE6. At the same time, the company notes that the preview had about a week of development and a shorter QA pass than usual. Some of the agent-written code is still being cleaned up, and parts of the web renderer are prototypes that will be refactored before the full release.
Unreal MCP and Unreal Assistant
The experimental Unreal MCP now launches automatically with the editor and offers more reliable connections. Its toolsets have expanded to cover rendering, source control, profiling, debugging, gameplay testing, geometry, audio, UI and level creation. A new Lore integration lets AI agents manage project changes and automate source control workflows, while the new Fab toolset allows agents to search the catalog, browse the user’s library and install free or purchased assets directly into projects.
The experimental Unreal Assistant lets developers use AI coding agents such as Claude Code, Codex, Cursor and OpenCode from an assistant panel inside Unreal Editor, connected to Unreal MCP.
Python and Unreal Canvas
Python APIs now cover audio, MetaSounds, modeling, physics, Niagara, materials, PCG, networking and UI, and these capabilities also allow AI agents to handle more tasks directly in the editor.
The experimental Unreal Canvas brings AI-assisted content creation both as a web app and inside Unreal Editor. It can generate concept art, images, 3D meshes and video from prompts, reference images or the user’s own scenes, and users can connect AI models of their choice with their own API keys.
Projects can run in a browser
Another highlight is the ability to run Unreal Engine projects directly in web browsers with no installation required. Powered by WebAssembly and WebGPU, the experimental feature uses the mobile renderer, currently requires a source build and a C++ project, and works best in Chrome. Epic Games warns of longer cook times and occasional performance issues. Among the known issues, the prebuilt Mac and Linux versions are missing some of the web support files, with a fix planned for release this week.
Reactions on the forum were mixed. Some users criticized the use of AI for writing documentation and said they are considering moving away from the engine, while others said being able to use their own agents inside the editor is a feature they had been hoping for.
