Crash during cook: BspMode module asserts on FSlateApplication::Get() in headless commandlet (UE 5.8.1)

General Issues and Bug Reporting (Unreal Engine)
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Summary

When packaging a project, the cook step crashes with an assertion failure in FSlateApplication::Get(). The crash occurs because FBspModeModule::StartupModule() calls FEditorClassUtils::GetTooltip(), which creates an SDocumentationToolTip widget that requires a valid FSlateApplication — unavailable during a headless cook commandlet (UnrealEditor-Cmd.exe -run=Cook).

The issue only manifests when the Editor Preference “Display Documentation Link” is enabled. Disabling it prevents the tooltip creation and allows the cook to succeed.

What Type of Bug are you experiencing?

Editor

Steps to Reproduce

  1. Create or open a project that loads the GeometryMode plugin (e.g., an FPS Template-based project).
  2. Ensure Editor Preferences > “Display Documentation Link” is enabled.
  3. Package the project for Windows.

Expected Result

The cook commandlet should complete successfully. Editor-only modules should not attempt to access FSlateApplication in a headless context, or the documentation tooltip code should gracefully check whether FSlateApplication is initialized before constructing widgets.

Observed Result

The cook fails with the following crash:

UATHelper: Packaging (Windows):
UATHelper: Error: Packaging (Windows): LogWindows: Error: begin: stack for UAT
UATHelper: Error: Packaging (Windows): LogWindows: Error: === Critical error: ===
UATHelper: Error: Packaging (Windows): LogWindows: Error:
UATHelper: Error: Packaging (Windows): LogWindows: Error: Assertion failed: CurrentApplication.IsValid() [File:D:\build++UE5\Sync\Engine\Source\Runtime\Slate\Public\Framework\Application\SlateApplication.h] [Line: 321]
UATHelper: Error: Packaging (Windows): LogWindows: Error:
UATHelper: Error: Packaging (Windows): LogWindows: Error:
UATHelper: Error: Packaging (Windows): LogWindows: Error:
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ffb0c22bec8 UnrealEditor-Core.dll!FDebug::CheckVerifyFailedImpl2() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Private\Misc\AssertionMacros.cpp:797]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ffb6c5e35f4 UnrealEditor-Documentation.dll!FSlateApplication::Get() [D:\build++UE5\Sync\Engine\Source\Runtime\Slate\Public\Framework\Application\SlateApplication.h:321]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ffb6c5ce70b UnrealEditor-Documentation.dll!SDocumentationToolTip::AddDocumentation() [D:\build++UE5\Sync\Engine\Source\Editor\Documentation\Private\SDocumentationToolTip.cpp:336]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ffb6c5d9dec UnrealEditor-Documentation.dll!SDocumentationToolTip::ConstructSimpleTipContent() [D:\build++UE5\Sync\Engine\Source\Editor\Documentation\Private\SDocumentationToolTip.cpp:222]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ffb6c5d3d30 UnrealEditor-Documentation.dll!SDocumentationToolTip::Construct() [D:\build++UE5\Sync\Engine\Source\Editor\Documentation\Private\SDocumentationToolTip.cpp:84]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ffb6c5c7f31 UnrealEditor-Documentation.dll!TSlateDecl<SDocumentationToolTip,RequiredArgs::T0RequiredArgs>::operator<<=() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Public\Widgets\DeclarativeSyntaxSupport.h:983]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ffb6c5dc0c3 UnrealEditor-Documentation.dll!FDocumentation::CreateToolTip() [D:\build++UE5\Sync\Engine\Source\Editor\Documentation\Private\Documentation.cpp:220]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ffb6c5dc45d UnrealEditor-Documentation.dll!FDocumentation::CreateToolTip() [D:\build++UE5\Sync\Engine\Source\Editor\Documentation\Private\Documentation.cpp:196]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ffb05774fe0 UnrealEditor-UnrealEd.dll!FEditorClassUtils::GetTooltip() [D:\build++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\EditorClassUtils.cpp:61]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ffabd034a33 UnrealEditor-BspMode.dll!FBspDragHandler::Initialize() [D:\build++UE5\Sync\Engine\Plugins\Editor\GeometryMode\Source\BspMode\Private\BspDragHandler.cpp:14]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ffabd0124bb UnrealEditor-BspMode.dll!FBspModeModule::RegisterBspBuilderType() [D:\build++UE5\Sync\Engine\Plugins\Editor\GeometryMode\Source\BspMode\Private\BspModeModule.cpp:78]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ffabd01179c UnrealEditor-BspMode.dll!FBspModeModule::StartupModule() [D:\build++UE5\Sync\Engine\Plugins\Editor\GeometryMode\Source\BspMode\Private\BspModeModule.cpp:50]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ffb0c3d8b27 UnrealEditor-Core.dll!FModuleManager::LoadModuleWithFailureReason() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Private\Modules\ModuleManager.cpp:1252]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ffbe073fd58 UnrealEditor-Projects.dll!FModuleDescriptor::LoadModulesForPhase() [D:\build++UE5\Sync\Engine\Source\Runtime\Projects\Private\ModuleDescriptor.cpp:798]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ffbe075e70e UnrealEditor-Projects.dll!FPluginManager::TryLoadModulesForPlugin() [D:\build++UE5\Sync\Engine\Source\Runtime\Projects\Private\PluginManager.cpp:2736]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ffbe073f679 UnrealEditor-Projects.dll!FPluginManager::LoadModulesForEnabledPlugins() [D:\build++UE5\Sync\Engine\Source\Runtime\Projects\Private\PluginManager.cpp:2875]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ff7fc196e5f UnrealEditor-Cmd.exe!FEngineLoop::PreInitPostStartupScreen() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\LaunchEngineLoop.cpp:4069]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ff7fc18c289 UnrealEditor-Cmd.exe!GuardedMain() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Launch.cpp:146]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ff7fc18c5ba UnrealEditor-Cmd.exe!GuardedMainWrapper() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:123]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ff7fc191256 UnrealEditor-Cmd.exe!LaunchWindowsStartup() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:277]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ff7fc1a5c74 UnrealEditor-Cmd.exe!WinMain() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:338]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ff7fc1a838a UnrealEditor-Cmd.exe!__scrt_common_main_seh() [D:\a_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288]
UATHelper: Error: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ffc1939ccb7 KERNEL32.DLL!UnknownFunction
UATHelper: Error: Packaging (Windows): LogWindows: Error:
UATHelper: Error: Packaging (Windows): LogWindows: Error: end: stack for UAT
UATHelper: Error: Packaging (Windows): Took 9,11s to run UnrealEditor-Cmd.exe, ExitCode=3
UATHelper: Error: Packaging (Windows): Cook failed.
(see C:\Users\Grego\AppData\Roaming\Unreal Engine\AutomationTool\Logs\C+Program+Files+Epic+Games+UE_5.8\Log.txt for full exception trace)
UATHelper: Packaging (Windows): AutomationTool executed for 0h 0m 25s
UATHelper: Packaging (Windows): AutomationTool exiting with ExitCode=25 (Error_UnknownCookFailure)
UATHelper: Packaging (Windows): Updating environment variables set by a Turnkey sub-process
UATHelper: Packaging (Windows): BUILD FAILED
LogStreaming: Display: FlushAsyncLoading(429): 1 QueuedPackages, 0 AsyncPackages
PackagingResults: Error: Unknown Cook Failure

Affects Versions

5.8

Platform(s)

Windows

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