Epic Games has released the Unreal Engine 5.9 MegaJam Preview, an experimental build that brings AI coding agents, editor tools and generative workflows closer together. Epic says it assembled the preview for the November 12–15 Epic AI MegaJam and gave it a shorter quality-assurance pass than usual. This is a preview, not the final 5.9 release.
In its November 9 announcement, Epic says engineers directed and reviewed AI-agent work while bringing tooling across from its Unreal Engine 6 development branch. That is Epic’s account of how it built the preview, not an independent assessment of the code.
Codex and other agents inside the editor
The experimental Unreal Assistant panel can run external agents including Codex, Claude Code, Cursor and OpenCode. Epic’s setup documentation explains that the selected agent uses its own provider account and connects to the editor through the Agent Client Protocol. The editor connects it to Unreal MCP for access to available tools.
That could make it easier to ask an agent to inspect a level or help with development without constantly switching between editor and terminal. It does not make the agent’s changes automatically correct; developers still need to inspect the work, test behavior and review changes before keeping them.
Unreal MCP: agents get editor tools
Epic describes Unreal MCP as an experimental server inside the editor. Its toolsets can expose operations for levels, Blueprints, materials, audio, profiling, testing and more. The preview announcement also describes a Fab toolset for finding assets and a Lore integration for project and source-control workflows.
There is a practical setup wrinkle: Epic lists a known issue in which new projects have the MCP server enabled but lack editor toolsets. Its stated workaround is to enable All Toolsets and restart the editor. The server is loopback-only by default and has no authentication, so its local access should be treated carefully and it should not be exposed to a network.
Canvas, Python and the browser
Experimental Unreal Canvas supports AI-assisted concepts, images, 3D meshes and video using prompts, references and scene context. Epic says creators can connect their chosen models with their own API keys; those providers’ terms and costs are separate considerations. Expanded Python APIs also expose more editor functionality to scripts and agents.
Epic has additionally included an experimental WebAssembly and WebGPU target. Its initial workflow requires a source build and a C++ project, uses the mobile renderer and can have performance or packaging limitations. This is a web deployment experiment, not a promise that every existing Unreal game will run unchanged in a browser.
Try it on a copy
Epic warns that the preview had limited QA and lists issues involving web builds, editor crashes and scripted changes. For a project like DroneKilla, a copied project and source-control checkpoint are sensible starting points. We have not tested this preview or its agent workflows, so the capabilities above are based on Epic’s announcement and documentation.
Original reporting based on Epic’s announcement and documentation; preview not independently tested.
