Unreal Engine 5.9 Preview 1 is out

Epic released Unreal Engine 5.9 Preview 1 on November 9. It is a preview, so it is still changing. Epic recommends testing it on a copy of a project, not the real one.

Here is the part that matters if you work with agents. The experimental Unreal MCP server now starts with the editor. MCP is how an AI agent uses tools inside the editor, so an agent can work on a level instead of only reading code. That is the step from chat about a game to an agent inside the build.

One bug will bite first. In new projects the MCP server runs, but the toolset plugins are off (UE-412135), so the agent gets no tools and no explanation. Fix it before you connect an agent: enable All Toolsets in Edit > Plugins, then restart the editor. You can also add the AllToolsets plugin to the .uproject file.

Primary source: Unreal Engine 5.9 MegaJam Preview. Official notes: Unreal Engine 5.9 Preview release notes.