Error at launch project creation

Mac, Unreal Engine Version 5.4.3, Xcode 15.4
Error at a project creation time.

any idea?

Setting up bundled DotNet SDK
/Volumes/X5_2/Epic/UE_5.4/Engine/Build/BatchFiles/Mac/../../../Binaries/ThirdParty/DotNet/6.0.302/mac-x64
Running dotnet Engine/Binaries/DotNET/UnrealBuildTool/UnrealBuildTool.dll -projectfiles -project=/Volumes/X5_2/Epic/Projects/Start/Start.uproject -game -rocket -progress
Log file: /Users/jinbom/Library/Application Support/Epic/UnrealBuildTool/Log_GPF.txt

Generating XCode project files:
Discovering modules, targets and source code for project...
Total execution time: 20.71 seconds
UnrealBuildTool(0): error:System.Text.Json.JsonException: '0x00' is an invalid start of a value. LineNumber: 0 | BytePositionInLine: 0. (in /Volumes/X5_2/Epic/UE_5.4/Engine/Plugins/2D/Paper2D/._Paper2D.uplugin)
 ---> System.Text.Json.JsonReaderException: '0x00' is an invalid start of a value. LineNumber: 0 | BytePositionInLine: 0.
   at System.Text.Json.ThrowHelper.ThrowJsonReaderException(Utf8JsonReader& json, ExceptionResource resource, Byte nextByte, ReadOnlySpan`1 bytes)
   at System.Text.Json.Utf8JsonReader.ConsumeValue(Byte marker)
   at System.Text.Json.Utf8JsonReader.ReadFirstToken(Byte first)
   at System.Text.Json.Utf8JsonReader.ReadSingleSegment()
   at System.Text.Json.Utf8JsonReader.Read()
   at System.Text.Json.JsonDocument.Parse(ReadOnlySpan`1 utf8JsonSpan, JsonReaderOptions readerOptions, MetadataDb& database, StackRowStack& stack)
   at System.Text.Json.JsonDocument.Parse(ReadOnlyMemory`1 utf8Json, JsonReaderOptions readerOptions, Byte[] extraRentedArrayPoolBytes, PooledByteBufferWriter extraPooledByteBufferWriter)
   at System.Text.Json.JsonDocument.Parse(ReadOnlyMemory`1 json, JsonDocumentOptions options)
   at System.Text.Json.JsonDocument.Parse(String json, JsonDocumentOptions options)
   at EpicGames.Core.JsonObject.Parse(String text) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/Shared/EpicGames.Core/JsonObject.cs:line 289
   at EpicGames.Core.JsonObject.Read(FileReference file) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/Shared/EpicGames.Core/JsonObject.cs:line 250
   at UnrealBuildTool.PluginDescriptor.FromFile(FileReference FileName) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/System/PluginDescriptor.cs:line 380
   --- End of inner exception stack trace ---
   at UnrealBuildTool.PluginDescriptor.FromFile(FileReference FileName) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/System/PluginDescriptor.cs:line 388
   at UnrealBuildTool.PluginInfo..ctor(FileReference InFile, PluginType InType) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/System/Plugins.cs:line 107
   at UnrealBuildTool.Plugins.ReadPluginsFromDirectory(DirectoryReference RootDirectory, String Subdirectory, PluginType Type) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/System/Plugins.cs:line 591
   at UnrealBuildTool.RulesCompiler.CreateEngineRulesAssembly(Boolean bUsePrecompiled, Boolean bSkipCompile, Boolean bForceCompile, ILogger Logger) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/System/RulesCompiler.cs:line 94
   at UnrealBuildTool.RulesCompiler.<>c__DisplayClass9_0.<CreateProjectRulesAssembly>b__0(FileReference _) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/System/RulesCompiler.cs:line 254
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
   at UnrealBuildTool.RulesCompiler.CreateProjectRulesAssembly(FileReference ProjectFileName, Boolean bUsePrecompiled, Boolean bSkipCompile, Boolean bForceCompile, ILogger Logger) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/System/RulesCompiler.cs:line 247
   at UnrealBuildTool.ProjectFileGenerator.AddProjectsForAllTargets(PlatformProjectGeneratorCollection PlatformProjectGenerators, List`1 AllGames, List`1 AllTargetFiles, String[] Arguments, List`1 EngineProjects, List`1 GameProjects, Dictionary`2 ProjectFileToUProjectFile, Dictionary`2 ProgramProjects, Dictionary`2 RulesAssemblies, ILogger Logger) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/ProjectFiles/ProjectFileGenerator.cs:line 2774
   at UnrealBuildTool.ProjectFileGenerator.GenerateProjectFiles(PlatformProjectGeneratorCollection PlatformProjectGenerators, String[] Arguments, Boolean bCacheDataForEditor, ILogger Logger) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/ProjectFiles/ProjectFileGenerator.cs:line 1038
   at UnrealBuildTool.GenerateProjectFilesMode.ExecuteAsync(CommandLineArguments Arguments, ILogger Logger) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/Modes/GenerateProjectFilesMode.cs:line 65
   at UnrealBuildTool.UnrealBuildTool.Main(String[] ArgumentsArray) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/UnrealBuildTool.cs:line 660

Having the exact issue with UE 5.5.1 on M1 macOS 15.2 with XCode 16
Installed and creating an empty project on an external SSD ExFAT4
It was a fresh install but tried uninstalling and reinstalling anyway
Seeing that the above post has no replies, I am hopeless but also clueless

Setting up bundled DotNet SDK
/Volumes/_/_/epic/UE_5.5/Engine/Build/BatchFiles/Mac/../../../Binaries/ThirdParty/DotNet/8.0.300/mac-arm64
Running dotnet Engine/Binaries/DotNET/UnrealBuildTool/UnrealBuildTool.dll -projectfiles -project=/Volumes/_/_.uproject -game -rocket -progress
Log file: /Users/_/Documents/Library/Application Support/Epic/UnrealBuildTool/Log_GPF.txt

Generating XCode project files:
Discovering modules, targets and source code for project...
Total execution time: 23.61 seconds
._Paper2D.uplugin(0): error: JsonReaderException: '0x00' is an invalid start of a value. LineNumber: 0 | BytePositionInLine: 0.
   at System.Text.Json.ThrowHelper.ThrowJsonReaderException(Utf8JsonReader& json, ExceptionResource resource, Byte nextByte, ReadOnlySpan`1 bytes)
   at System.Text.Json.Utf8JsonReader.ConsumeValue(Byte marker)
   at System.Text.Json.Utf8JsonReader.ReadFirstToken(Byte first)
   at System.Text.Json.Utf8JsonReader.ReadSingleSegment()
   at System.Text.Json.Utf8JsonReader.Read()
   at System.Text.Json.JsonDocument.Parse(ReadOnlySpan`1 utf8JsonSpan, JsonReaderOptions readerOptions, MetadataDb& database, StackRowStack& stack)
   at System.Text.Json.JsonDocument.Parse(ReadOnlyMemory`1 utf8Json, JsonReaderOptions readerOptions, Byte[] extraRentedArrayPoolBytes, PooledByteBufferWriter extraPooledByteBufferWriter)
   at System.Text.Json.JsonDocument.Parse(ReadOnlyMemory`1 json, JsonDocumentOptions options)
   at System.Text.Json.JsonDocument.Parse(String json, JsonDocumentOptions options)
   at EpicGames.Core.JsonObject.Parse(String text) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/Shared/EpicGames.Core/JsonObject.cs:line 289
   at EpicGames.Core.JsonObject.Read(FileReference file) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/Shared/EpicGames.Core/JsonObject.cs:line 250
   at UnrealBuildTool.PluginDescriptor.FromFile(FileReference FileName) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/System/PluginDescriptor.cs:line 395Wrapped by JsonException: '0x00' is an invalid start of a value. LineNumber: 0 | BytePositionInLine: 0. (in /Volumes/KINGSTON/macosapps/epic/UE_5.5/Engine/Plugins/2D/Paper2D/._Paper2D.uplugin)
   at UnrealBuildTool.PluginDescriptor.FromFile(FileReference FileName) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/System/PluginDescriptor.cs:line 403
   at UnrealBuildTool.PluginInfo..ctor(FileReference InFile, PluginType InType) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/System/Plugins.cs:line 107
   at UnrealBuildTool.Plugins.ReadPluginsFromDirectory(DirectoryReference RootDirectory, String Subdirectory, PluginType Type) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/System/Plugins.cs:line 591
   at UnrealBuildTool.Plugins.ReadEnginePlugins(DirectoryReference EngineDirectory) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/System/Plugins.cs:line 351
   at UnrealBuildTool.RulesCompiler.CreateEngineRulesAssembly(Boolean bUsePrecompiled, Boolean bSkipCompile, Boolean bForceCompile, ILogger Logger) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/System/RulesCompiler.cs:line 94
   at UnrealBuildTool.ProjectFileGenerator.AddProjectsForAllTargets(PlatformProjectGeneratorCollection PlatformProjectGenerators, List`1 AllGames, List`1 AllTargetFiles, String[] Arguments, List`1 EngineProjects, List`1 GameProjects, Dictionary`2 ProjectFileToUProjectFile, Dictionary`2 ProgramProjects, Dictionary`2 RulesAssemblies, ILogger Logger) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/ProjectFiles/ProjectFileGenerator.cs:line 2777
   at UnrealBuildTool.ProjectFileGenerator.GenerateProjectFiles(PlatformProjectGeneratorCollection PlatformProjectGenerators, String[] Arguments, Boolean bCacheDataForEditor, ILogger Logger) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/ProjectFiles/ProjectFileGenerator.cs:line 1048
   at UnrealBuildTool.GenerateProjectFilesMode.ExecuteAsync(CommandLineArguments Arguments, ILogger Logger) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/Modes/GenerateProjectFilesMode.cs:line 260
   at UnrealBuildTool.UnrealBuildTool.Main(String[] ArgumentsArray) in /Users/build/Build/++UE5/Sync/Engine/Saved/CsTools/Engine/Source/Programs/UnrealBuildTool/UnrealBuildTool.cs:line 687

Same issue with UE 5.5.1 when trying to generate Visual Studio project files on Windows. I created the project on a M3 Macbook Pro and transfered project files using a USB key.

In my case it occurs with AdvancedSessions plugin, it’s the only one in my project.

Generating VisualStudio project files:
Discovering modules, targets and source code for project...
Total execution time: 1.09 seconds
._AdvancedSessions.uplugin(0): error: JsonReaderException: '0x00' is an invalid start of a value. LineNumber: 0 | BytePositionInLine: 0.
   at System.Text.Json.ThrowHelper.ThrowJsonReaderException(Utf8JsonReader& json, ExceptionResource resource, Byte nextByte, ReadOnlySpan`1 bytes)
   at System.Text.Json.Utf8JsonReader.ConsumeValue(Byte marker)
   at System.Text.Json.Utf8JsonReader.ReadFirstToken(Byte first)
   at System.Text.Json.Utf8JsonReader.ReadSingleSegment()
   at System.Text.Json.Utf8JsonReader.Read()
   at System.Text.Json.JsonDocument.Parse(ReadOnlySpan`1 utf8JsonSpan, JsonReaderOptions readerOptions, MetadataDb& database, StackRowStack& stack)
   at System.Text.Json.JsonDocument.Parse(ReadOnlyMemory`1 utf8Json, JsonReaderOptions readerOptions, Byte[] extraRentedArrayPoolBytes, PooledByteBufferWriter extraPooledByteBufferWriter)
   at System.Text.Json.JsonDocument.Parse(ReadOnlyMemory`1 json, JsonDocumentOptions options)
   at System.Text.Json.JsonDocument.Parse(String json, JsonDocumentOptions options)
   at EpicGames.Core.JsonObject.Parse(String text) in D:\build\++UE5\Sync\Engine\Saved\CsTools\Engine\Source\Programs\Shared\EpicGames.Core\JsonObject.cs:line 289
   at EpicGames.Core.JsonObject.Read(FileReference file) in D:\build\++UE5\Sync\Engine\Saved\CsTools\Engine\Source\Programs\Shared\EpicGames.Core\JsonObject.cs:line 250
   at UnrealBuildTool.PluginDescriptor.FromFile(FileReference FileName) in D:\build\++UE5\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\System\PluginDescriptor.cs:line 395Wrapped by JsonException: '0x00' is an invalid start of a value. LineNumber: 0 | BytePositionInLine: 0. (in C:\Users\gegva\Documents\1\Plugins\AdvancedSessions\._AdvancedSessions.uplugin)
   at UnrealBuildTool.PluginDescriptor.FromFile(FileReference FileName) in D:\build\++UE5\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\System\PluginDescriptor.cs:line 403
   at UnrealBuildTool.PluginInfo..ctor(FileReference InFile, PluginType InType) in D:\build\++UE5\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\System\Plugins.cs:line 107
   at UnrealBuildTool.Plugins.ReadPluginsFromDirectory(DirectoryReference RootDirectory, String Subdirectory, PluginType Type) in D:\build\++UE5\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\System\Plugins.cs:line 591
   at UnrealBuildTool.Plugins.ReadProjectPlugins(DirectoryReference ProjectDirectory) in D:\build\++UE5\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\System\Plugins.cs:line 362
   at UnrealBuildTool.RulesCompiler.<>c__DisplayClass9_0.<CreateProjectRulesAssembly>b__0(FileReference _) in D:\build\++UE5\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\System\RulesCompiler.cs:line 291
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
   at UnrealBuildTool.RulesCompiler.CreateProjectRulesAssembly(FileReference ProjectFileName, Boolean bUsePrecompiled, Boolean bSkipCompile, Boolean bForceCompile, ILogger Logger) in D:\build\++UE5\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\System\RulesCompiler.cs:line 247
   at UnrealBuildTool.ProjectFileGenerator.AddProjectsForAllTargets(PlatformProjectGeneratorCollection PlatformProjectGenerators, List`1 AllGames, List`1 AllTargetFiles, String[] Arguments, List`1 EngineProjects, List`1 GameProjects, Dictionary`2 ProjectFileToUProjectFile, Dictionary`2 ProgramProjects, Dictionary`2 RulesAssemblies, ILogger Logger) in D:\build\++UE5\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\ProjectFiles\ProjectFileGenerator.cs:line 2791
   at UnrealBuildTool.ProjectFileGenerator.GenerateProjectFiles(PlatformProjectGeneratorCollection PlatformProjectGenerators, String[] Arguments, Boolean bCacheDataForEditor, ILogger Logger) in D:\build\++UE5\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\ProjectFiles\ProjectFileGenerator.cs:line 1048
   at UnrealBuildTool.GenerateProjectFilesMode.ExecuteAsync(CommandLineArguments Arguments, ILogger Logger) in D:\build\++UE5\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Modes\GenerateProjectFilesMode.cs:line 260
   at UnrealBuildTool.UnrealBuildTool.Main(String[] ArgumentsArray) in D:\build\++UE5\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\UnrealBuildTool.cs:line 687

I’ll keep you updated if I find something.

Has anyone got updates for this? I’m trying to build a project on UE 5.5.2 and keep getting the same error as OP with the logs stating Paper2D is having issues.

I’ve even disabled Paper2D and it’s still giving me errors.

Getting same issue here with UE5.5.2 on a MBP M1. Generate Project Files right click menu does nothing. Manually forming command in Termal results in the same error as reported above.

Project was created on Windows. On older Intel Mac Mini no issues generating project and building.