SKILL.md

Unreal Packaging & Cooking

Turn a UE5 project into a runnable, distributable build: choose the right build configuration, cook content, set the launch map, and package — from the editor or the command line. Targets UE 5.8.

When to use

Use when producing a build (test or release), choosing Development vs Shipping, cooking content, configuring Packaging / Maps & Modes settings, or automating builds with RunUAT BuildCookRun for CI.
Use when the project has a *.uproject and Config/Default*.ini, and the goal is a packaged player rather than running in-editor.

When not to use: storefront submission/release process → steam-publish / itch-publish. Editor-time gameplay/iteration is not packaging.

Core workflow

Set the launch map. Project Settings → Maps & Modes → Game Default Map is what a packaged build loads first. Wrong/empty here is the most common "packaged game is black" cause.
Pick the build configuration: Development (default; optimized but keeps logging/ stats/console for testing) vs Shipping (all optimizations, debugging tools stripped — for release). DebugGame/Debug are for debugging engine/game code and aren't for distribution; DebugGame isn't available for Blueprint-only projects.
Understand cook vs package. Cooking converts assets to the target platform's format. Staging/packaging copies the compiled executable + cooked content into a standalone, distributable folder, with content in container files (.pak, plus .utoc/.ucas when Use Io Store is on, which is the default). Packaging runs a cook as part of it.
Package from the editor: the Platforms menu → choose the platform (e.g. Windows) → set the Binary Configuration → Package Project → pick an output folder.
Or build from the command line with the Unreal Automation Tool (RunUAT BuildCookRun) for repeatable/CI builds. The Project Launcher (Platforms → Project Launcher) saves the same build/cook/stage/deploy choices as reusable launch profiles.
Tune Packaging settings (Project Settings → Packaging): which maps/directories to cook, full-rebuild, compression, and whether to build all maps.
Validate assets before packaging when UnrealEditor-Cmd is available. Run UnrealEditor-Cmd <Project>.uproject -run=DataValidation (UnrealEditor-Cmd.exe on Windows) and fix every reported validation error before cooking.
Verify by running the packaged build, not just by a successful cook — launch the executable and confirm it loads the right map and runs.

Patterns

1. Editor packaging (the menu path)

Platforms (toolbar)
  -> Windows
     -> Binary Configuration -> Development | Shipping
     -> Content Management -> Package Project
  -> choose/confirm the staging output folder

2. Command-line build with UAT (CI-friendly)

# Cook + build + stage + pak + archive a Shipping Windows build.
RunUAT BuildCookRun \
  -project="C:/Path/MyGame.uproject" \
  -noP4 -platform=Win64 -clientconfig=Shipping \
  -cook -allmaps -build -stage -pak -archive \
  -archivedirectory="C:/Builds/MyGame"

RunUAT lives in Engine/Build/BatchFiles/ (RunUAT.bat on Windows, RunUAT.sh on macOS/Linux). Drop -allmaps and pass -map=Map1+Map2 to cook a subset. UE 5.8 adds experimental Windows on Arm game builds: -clientarchitecture=arm64 (or arm64+x64 for both executables side by side); the editor itself is not supported on Arm64 in 5.8.

3. Cook only (no packaging), e.g. to refresh content

RunUAT BuildCookRun -project="C:/Path/MyGame.uproject" -noP4 \
  -platform=Win64 -clientconfig=Development -cook -skipstage

Pitfalls

Packaged build loads a black/empty level — Game Default Map isn't set (or that map wasn't cooked). Set it in Maps & Modes and ensure it's included in the cook.
Shipping a Development build — Development keeps logging/console/stats and is slower; ship Shipping. Conversely, Shipping strips UE_LOG/console, so debugging a Shipping-only issue needs Development or Test. A Shipping build has no console quit, so the game needs its own exit option.
A referenced map/asset is missing at runtime — it wasn't cooked. Add it to the Packaging settings' maps/directories to cook, or cook all maps.
Build fails on the platform — the platform SDK/toolchain isn't installed or is too old. For UE 5.8 on Windows that means Visual Studio 2022 17.14+ (2026 recommended), MSVC 14.38+ and Windows SDK 10.0.22621.0+; macOS needs Xcode 15.2+. Check the release notes' Platform SDK table for other targets. Console packaging also requires a source build of the engine, not the Launcher build.
Saved/Cooked/<Platform> has no .uasset/.uexp files — in UE 5.8 Zen Server is the cooked output store by default (unless the project turned it off in Packaging settings). The folder only holds a small ue.projectstore marker and the data lives in the Zen data directory. Staging still writes .pak/.utoc/.ucas to the staging folder; ship that folder, not Saved/Cooked. For team and CI machines Epic recommends LimitProcessLifetime=false under [Zen.AutoLaunch] in DefaultEngine.ini so zenserver is not started and stopped on every step; make sure your build automation tolerates that long-running process.
Expecting Blueprint Nativization — it was removed in UE5; don't rely on it for performance. Profile and move hot logic to C++ (unreal-cpp-gameplay) instead.
First cook is very slow — shaders and all assets cook from scratch; subsequent cooks are incremental. Don't mistake a slow first cook for a hang.

References

Primary docs: "Packaging Your Project" (https://dev.epicgames.com/documentation/en-us/unreal-engine/packaging-your-project), the Build Configurations / BuildCookRun references, "Zenserver as Cooked Output Store" (https://dev.epicgames.com/documentation/en-us/unreal-engine/using-zen-storage-server-as-cooked-output-store-for-unreal-engine) and the Platform SDK table in the UE 5.8 release notes (https://dev.epicgames.com/documentation/en-us/unreal-engine/unreal-engine-5-8-release-notes).

Related skills

steam-publish / itch-publish — distributing the packaged build to a storefront.
unreal-cpp-gameplay — moving hot logic to C++ now that BP nativization is gone.