Epic Games released the Unreal Engine 5.9 MegaJam Preview on November 9 and calls it the first Unreal Engine release “built primarily with agentic workflows.” In a post by Flak on the Epic Developer Community forums, Epic said a small group of staff steered large numbers of AI agents to move AI tools across from its Unreal Engine 6 branch and to make the web a build target.
As we reported on November 9, Epic had promised “improved AI workflows” for 5.9 without saying what they were. Epic's forum post and release notes now list them; most are experimental.
Unreal Assistant is an editor panel that runs a developer's chosen coding agent, such as Claude Code, Codex, Cursor or OpenCode, hooked up to Unreal MCP. That's the editor's server for the Model Context Protocol, a standard that lets AI agents use outside tools. Unreal MCP now starts with the editor and adds toolsets for rendering, profiling, debugging, testing and level building. Agents can now handle source control through Lore and find and install Fab assets.
Expanded Python APIs, which agents can also use, cover audio, Niagara, materials, PCG and more. Unreal Canvas, a web app that also runs in the editor, generates concept art, images, 3D meshes and video from prompts or scenes, using AI models developers connect with their own API keys. The release notes also list a UAF AnimGen plugin for AI-generated animation.
The browser target runs on WebAssembly and WebGPU with the mobile renderer, and for now needs a source build and a C++ project; Epic says Chrome works best. Agents wrote the code behind it, working from the HTML5 export Epic retired after UE4, with engineers reviewing it.
Why it matters: Unreal developers can now drive Claude Code or Codex from inside the editor and build for browsers, a target Unreal Engine 5 lacked. It's also Epic testing on itself the agent-led workflow it is promoting to MegaJam teams.
Caveat: Epic says the Preview got roughly one week of work and less testing than usual, that it is still tidying code the agents wrote, and that some of the web renderer is prototype code. We haven't tested it.
The Epic AI MegaJam runs November 12 to 15. Epic says it will fix bugs through the preview period and refactor the web renderer before the full 5.9 release, which it had been preparing for next year.
