Build Troubleshooting
This page collects the errors that come up most often, what they actually mean, and how to clear them.
Toolchain errors
error C4668: '__has_feature' is not defined as a preprocessor macro
This is the signature error of a toolchain mismatch. Unreal Engine 4.27 predates the MSVC version you have installed, and UBT has selected a toolset whose preprocessor behaviour the engine's headers do not expect.
Fix. Install a supported MSVC version, remove the others, and pin the SDK in BuildConfiguration.xml. See Toolchain Requirements. Regenerate project files after changing anything.
UnrealBuildTool picks the wrong compiler or SDK
UBT autodetects by scanning installed toolsets and generally prefers the newest. When you have several installed, that is often not the one you want.
Fix. Pin both explicitly in %APPDATA%\Unreal Engine\UnrealBuildTool\BuildConfiguration.xml:
Then run GenerateProjectFiles.bat again. Watch the build log just before linking to confirm the toolchain UBT reports is the one you intended.
ViteSetup.bat refuses to continue with a [FAIL] line
The assistant enforces its toolchain requirements deliberately and offers no bypass. The failing line names the missing component. Note that the assistant currently pins Visual Studio 2022, MSVC 14.44 and Windows SDK 10.0.26100.7705 or higher; if you are on the newer VS 2026 / MSVC 14.50 toolchain, either build manually as described in Building from Source, or update the REQUIRED_* variables at the top of the script.
C# tool projects fail to build (SwarmAgent, NetworkProfiler, UnrealControls)
These target .NET Framework 4.5, whose targeting pack modern Visual Studio installers no longer ship.
Fix. Install it, as described in Toolchain Requirements. A v4.5 folder containing only XML files is a runtime stub, not a targeting pack — check for v4.5\RedistList\FrameworkList.xml.
Dependency and setup errors
Setup.bat fails to download dependencies
In stock Unreal Engine 4.27 this happens because the GitDeps endpoints have moved. Vite already ships the fix, so if you are seeing download failures on this fork, the cause is environmental: a proxy, a firewall, or an interrupted earlier run leaving a corrupt cache.
Fix. Delete the UE4_Source_Cache folder in the repository root and run Setup.bat again. ViteSetup.bat removes this cache automatically after a successful setup.
Setup.bat asks to overwrite local changes
Answer N. Answering Y reverts fork-specific files to their upstream state and will break the build.
Missing astcenc.exe or other third-party tools in a Win64 build
You excluded the Win32 folders during setup. Win64 installed builds depend on tools that live under Win32, including ARM\Win32\astcenc.exe.
Fix. Re-run Setup.bat without any -exclude=Win32 argument. The ViteSetup.bat presets never exclude Win32 for this reason.
Compile and link errors
Out of memory or heap exhaustion during compilation
Unreal's unity build system compiles very large translation units and parallelises aggressively. On machines with high core counts and modest RAM, the default parallelism can exhaust memory.
Fix. Limit parallel actions in BuildConfiguration.xml:
The editor builds but fails to launch
Confirm all three targets were built: UE4Editor, ShaderCompileWorker and UnrealLightmass. Building only the editor target produces a binary that starts and then fails as soon as it needs to compile a shader.
Stale shaders or derived data after pulling engine changes
Rendering changes invalidate the shader cache. If you see shader compilation errors, missing materials or visual corruption after a pull, wipe the engine-level caches:
This removes Engine\DerivedDataCache, Engine\Intermediate\Shaders and Engine\Saved\ShaderDebugInfo. The engine rebuilds them on the next launch, which will take a while. Close the editor and any ShaderCompileWorker processes first, or the deletion will fail. See Cache Management.
Runtime issues after a successful build
A new project runs much slower than expected
Ray tracing is enabled by default in Vite, including shadows, reflections, translucency and ambient occlusion. This is intentional so that the features are discoverable, but it means an empty project is heavier than a stock 4.27 one.
Fix. Disable the effects you do not need. See Ray Tracing for the console variables.
Gameplay behaves differently from stock 4.27
Vite changes several engine defaults for performance, and some of them affect behaviour rather than just frame time — overlap events are disabled by default on primitive components, for instance.
Fix. Read Engine Default Changes in full. Every changed default is listed there with a link to the commit that changed it.
Getting help
If none of the above applies, the #support channels on the community Discord are the fastest route. Include your Visual Studio version, MSVC toolset version, Windows SDK version, the branch you are building, and the first error in the log rather than the last — Unreal's build output cascades, and the final error is rarely the useful one.