Rider launches previous UnreaEditor executable upon retargeting project to a newer engine version

Scenario:

• User usually opens project through .uproject;

• Once the project is being retargeted to a newer engine version (e.g. from UE 5.6 to UE 5.7);

• It might happen that during project retartegting, the UBT errors might be not noticed by a user and skipped;

• User opens a project in Rider. Project now targets newer engine (EngineAssociation in .uproject is new);

• Rider attempts to generate its own project files by calling UBT (by design);

• Rider reports Failed to generate Unreal project model definition files. This could be due to a conflicting instance of UBT already running.:

• In the project files generation output (the UnrealBuiltTool tool window) it is seen:

  09:23:43.014: dotnet.exe "C:\Program Files\Epic Games\UE_5.7\Engine\Binaries\DotNET\UnrealBuildTool\UnrealBuildTool.dll" -ProjectFiles -Rider -Automated -Minimize -NoMutex -Log=C:\Users\Dmitry.Kazantsev\AppData\Local\JetBrains\Rider2025.3\log\UBT_GPF.txt -Platforms=Win64 -TargetTypes=Editor -TargetConfigurations=Development A:\Projekte\u56l_fps\u56l_fps.uproject
  09:23:43.252: Log file: C:\Users\Dmitry.Kazantsev\AppData\Local\JetBrains\Rider2025.3\log\UBT_GPF.txt
  09:23:43.410: Generating Rider project files:
  09:23:43.721: Writing project files...
  09:23:43.721: Warning: [Upgrade]
  09:23:43.721: Warning: [Upgrade] Using backward-compatible build settings. The latest version of UE sets the following values by default, which may require code changes:
  09:23:43.721: Warning: [Upgrade]     WindowsPlatform.bStrictInlineConformance = true        => Updates MSVC inline conformance (Remove unreferenced COMDAT) to true (Previously: false).
  09:23:43.721: Warning: [Upgrade]     UndefinedIdentifierWarningLevel = WarningLevel.Error   => Enables compile-time validation of undefined identifiers in conditional expressions. (Previously: Off).
  09:23:43.721: Warning: [Upgrade] Suppress this message by setting 'DefaultBuildSettings = BuildSettingsVersion.V6;' in u56l_fpsEditor.Target.cs, and explicitly overriding settings that differ from the new defaults.
  09:23:43.721: Warning: [Upgrade]
  09:23:43.721: Warning: [Upgrade]
  09:23:43.721: Warning: [Upgrade] Using backward-compatible include order. The latest version of UE has changed the order of includes, which may require code changes. The current setting is:
  09:23:43.721: Warning: [Upgrade]     IncludeOrderVersion = EngineIncludeOrderVersion.Unreal5_6
  09:23:43.721: Warning: [Upgrade] Suppress this message by setting 'IncludeOrderVersion = EngineIncludeOrderVersion.Unreal5_7;' in u56l_fpsEditor.Target.cs.
  09:23:43.721: Warning: [Upgrade] Alternatively you can set this to 'EngineIncludeOrderVersion.Latest' to always use the latest include order. This will potentially cause compile errors when integrating new versions of the engine.
  09:23:43.721: Warning: [Upgrade]
  09:23:43.860: Wrote partial receipt to A:\Projekte\u56l_fps\Binaries\Win64\u56l_fpsEditor.target
  09:23:43.860: Exception while generating include data for Target:u56l_fpsEditor, Platform: Win64, Configuration: Development
  09:23:43.860: u56l_fpsEditor modifies the values of properties: [ UndefinedIdentifierWarningLevel: Off != Error ]. This is not allowed, as u56l_fpsEditor has build products in common with UnrealEditor.
  09:23:43.860: Remove the modified setting, change u56l_fpsEditor to use a unique build environment by setting 'BuildEnvironment = TargetBuildEnvironment.Unique;' in the u56l_fpsEditorTarget constructor, or set bOverrideBuildEnvironment = true to force this setting on.
  09:24:04.500: Writing project files... 33%
  09:24:04.500: Writing project files... 100%
  09:24:04.589: Generating QueryTargets data for editor...
  09:24:04.590: Compiling Rules Assemblies 100%
  09:24:04.604: Writing Query Target Info 100%
  09:24:04.604: Generating QueryTargets data for editor took 0.02s
  09:24:04.606: Result: Succeeded
  09:24:04.606: Total execution time: 21.52 seconds
  

  • Meantime this error is the caused by the initial failure during "switching UE version". There is the output that might be skipped during switching UE version for the project:

    Running C:/Program Files/Epic Games/UE_5.7/Engine/Build/BatchFiles/Build.bat Development Win64 -Project="A:/Projekte/u56l_fps/u56l_fps.uproject" -TargetType=Editor -Progress -NoEngineChanges -NoHotReloadFromIDE
    Using bundled DotNet SDK version: 8.0.412 win-x64
    Running UnrealBuildTool: dotnet "..\..\Engine\Binaries\DotNET\UnrealBuildTool\UnrealBuildTool.dll" Development Win64 -Project="A:/Projekte/u56l_fps/u56l_fps.uproject" -TargetType=Editor -Progress -NoEngineChanges -NoHotReloadFromIDE
    Log file: C:\Users\Dmitry.Kazantsev\AppData\Local\UnrealBuildTool\Log.txt
    Creating makefile for u56l_fpsEditor (no existing makefile)
    Warning: [Upgrade]
    Warning: [Upgrade] Using backward-compatible build settings. The latest version of UE sets the following values by default, which may require code changes:
    Warning: [Upgrade]     WindowsPlatform.bStrictInlineConformance = true        => Updates MSVC inline conformance (Remove unreferenced COMDAT) to true (Previously: false).
    Warning: [Upgrade]     UndefinedIdentifierWarningLevel = WarningLevel.Error   => Enables compile-time validation of undefined identifiers in conditional expressions. (Previously: Off).
    Warning: [Upgrade] Suppress this message by setting 'DefaultBuildSettings = BuildSettingsVersion.V6;' in u56l_fpsEditor.Target.cs, and explicitly overriding settings that differ from the new defaults.
    Warning: [Upgrade]
    Warning: [Upgrade]
    Warning: [Upgrade] Using backward-compatible include order. The latest version of UE has changed the order of includes, which may require code changes. The current setting is:
    Warning: [Upgrade]     IncludeOrderVersion = EngineIncludeOrderVersion.Unreal5_6
    Warning: [Upgrade] Suppress this message by setting 'IncludeOrderVersion = EngineIncludeOrderVersion.Unreal5_7;' in u56l_fpsEditor.Target.cs.
    Warning: [Upgrade] Alternatively you can set this to 'EngineIncludeOrderVersion.Latest' to always use the latest include order. This will potentially cause compile errors when integrating new versions of the engine.
    Warning: [Upgrade]
    Wrote partial receipt to A:\Projekte\u56l_fps\Binaries\Win64\u56l_fpsEditor.target
    u56l_fpsEditor modifies the values of properties: [ UndefinedIdentifierWarningLevel: Off != Error ]. This is not allowed, as u56l_fpsEditor has build products in common with UnrealEditor.
    Remove the modified setting, change u56l_fpsEditor to use a unique build environment by setting 'BuildEnvironment = TargetBuildEnvironment.Unique;' in the u56l_fpsEditorTarget constructor, or set bOverrideBuildEnvironment = true to force this setting on.
    
    Result: Failed (OtherCompilationError)
    Total execution time: 0.62 seconds
    

• User might attempt to launch project via the Run button. But it leads to launch of previous engine: (Expected Exe path to be: ...UE5.7\Engine'Win64\UnrealEditor.exe)

Solution:

See the UBT output for the project files generation. When a new engine versions release, it might be the project requires specific changes for the project files to generate properly. In current situation, it says the below changes need to be done to target.cs files:

DefaultBuildSettings = BuildSettingsVersion.V6;
IncludeOrderVersion = EngineIncludeOrderVersion.Unreal5_7;
bOverrideBuildEnvironment = true;

In case of FirstPersonShooter template project created with UE5.6, the following files requires that similar changes to be applied: "u56l_fps.Target.cs", "u56l_fps.EditorTarget.cs"

Note: sample report in Epic Games forum: thread.