AI News · 5 min read
Unreal Engine 5.9 Preview brings Claude Code and Codex into the editor
Epic's UE 5.9 MegaJam Preview was built mostly by AI agents in about a week. It adds Unreal Assistant, a bigger Unreal MCP, Unreal Canvas and browser builds.
What Epic released
On November 9, 2026, Epic Games released the Unreal Engine 5.9 MegaJam Preview ↗. You can download it from the Epic Games Launcher or GitHub. Epic calls it "the first Unreal Engine release built primarily with agentic workflows," and Inven Global ↗ and GameMakers ↗ reported the details the same day.
Epic is unusually open about how it was made. The team only decided to build a 5.9 Preview "just a week ago," in time for the Epic AI MegaJam on November 12–15. "A handful of people directed fleets of agents to port the AI tooling from our UE6 development branch and implement Web as a target platform." Agents wrote the new web platform code, starting from UE4's retired HTML5 platform, while engineers directed, reviewed and tested it.
Epic also lists the trade-offs itself: "about a week of development and a shorter QA pass than usual," agent-written code that's still being cleaned up, and web-renderer parts that are prototypes. "Expect rough edges, missing pieces, and things that break."
What's new for AI tools
Everything below is marked Experimental:
| Feature | What it does |
|---|---|
| Unreal Assistant | An in-editor panel for Claude Code, Codex, Cursor or OpenCode, connected to Unreal MCP |
| Unreal MCP | Starts with the editor; new toolsets for rendering, source control, profiling, debugging, gameplay testing, geometry, audio, UI and level creation |
| Fab toolset | Agents can search Fab, browse your library and install free or purchased assets |
| Unreal Canvas | Concept art, images, 3D meshes and video from prompts or your own scenes, using models you connect with your own API keys |
| Expanded Python | New APIs for audio, MetaSounds, Niagara, materials, PCG, networking and UI, which agents can also use |
There's also an integration with Lore for agent-managed source control. And projects can now run in a browser through WebAssembly and WebGPU. For now that uses the mobile renderer, needs a source build and a C++ project, and works best in Chrome.
One setup step catches people out. Epic's own known-issues post says new projects give agents "no tools to edit the level." The MCP server is on, but the Toolset plugins are off. Before you connect your agent, enable All Toolsets in Edit > Plugins, restart the editor, then reconnect. You need to do this once per project.
Other known issues include web games crashing above 2 GB of Wasm memory and the Mac and Linux launcher builds missing some web support files. Epic says a fix build is planned this week.
The MegaJam
The preview is timed for the Epic AI MegaJam. Teams of up to five can use as many AI agents as they like to build a game in Unreal Engine or UEFN, and standout entries can get grants of up to $50,000, per Inven Global ↗. On the forum, one developer asked whether jam entrants are expected to use 5.9 or can stay on 5.8. Epic hadn't answered when we checked.
What developers are saying
The @UnrealEngine announcement ↗ passed 118,000 views. Reactions split sharply:
"Being able to use our own agents inside the editor is what I was hoping for. Debugging by screenshotting broken graphs was such a pain," wrote Garud ↗ on Epic's forum.
"Unreal Engine 5.9 Preview is out. Almost everything in it is AI," posted Stefan 3D AI ↗ in a widely bookmarked feature thread.
"The interesting number isn't 'a week', it's how many people reviewed what the agents wrote... review is the bottleneck now, not typing," replied Mukhsin Mukhtorov ↗.
Forum regulars were harsher. "lol, instead of finishing experimental plugins and fixing perf bugs we get more bugs," wrote KryogenicGames ↗. RYRY1002 said the new docs "sound unsure of itself" and that the new pages have no images.
"Can the in-editor agent edit blueprints directly or is it only touching c++?" asked Agentic Feed ↗. Epic's MCP toolsets list Blueprint tools, but only once you've turned them on.
We couldn't pull Reddit threads for this story (Reddit blocked our requests), so these reactions are from X and Epic's own forum.
Our take
Unreal Assistant matters more than the "built by agents" headline. Unreal MCP was already there as an experimental plugin. What's new is that it starts with the editor, reaches far more of the engine (levels, profiling, tests, even the Fab store), and comes with an in-editor panel for the agents people already pay for. That's a clear sign that big creative tools now treat outside coding agents as first-class users. Our MCP tutorial explains why that standard matters.
Use it for the jam or on a copy, not on a shipping project. Epic says so plainly, and a week of development with a short QA pass is a warning, not modesty. If you're entering the MegaJam, enable All Toolsets first, and pick an agent you already know. Our Claude Code review and Codex vs Claude Code comparison can help you choose. If you prefer an editor-first workflow, see our Copilot vs Cursor comparison.
The backlash is worth taking seriously. Long-time users want unfinished experimental features finished, not more of them, and AI-written docs without screenshots don't help. Epic has said it will triage bugs with agents during the preview. How quickly the known issues get fixed will show whether this way of working actually helps Unreal developers.