What is causing this build error from source: Build.bat -Target="ShaderCompileWorker" -WaitMutex -FromMsBuild" exited with code 6

We are using the 4.25 source code for a project and out of nowhere this error started popping up when trying to compile the project/engines code:

Severity Code Description Project File Line Suppression State
Error MSB3073 The command “…..\Build\BatchFiles\Build.bat -Target=“MyProjectEditor Win64 Development” -Target=“ShaderCompileWorker Win64 Development -Quiet” -WaitMutex -FromMsBuild” exited with code 6. MyProject C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Microsoft\VC\v160\Microsoft.MakeFile.Targets 46

Has anyone encountered this before? I have seen similar issues after some searching, but nothing related to this message.

If it helps:
Microsoft Visual Studio Community 2019
Version 16.9.0

Same issue here

Severity Code Description Project File Line Suppression State
Error MSB3073 The command ““D:\Epic Games\UE_4.26\Engine\Build\BatchFiles\Build.bat” Edit_BP_via_CPPEditor Win64 Development -Project=“D:\tests\Edit_BP_via_CPP\Edit_BP_via_CPP.uproject” -WaitMutex -FromMsBuild” exited with code 6. Edit_BP_via_CPP C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Microsoft\VC\v160\Microsoft.MakeFile.Targets 46

Same issue, can’t use C++ at all in Unreal Engine 4.26.1. I don’t have the issue in 4.25.4.

C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\MSBuild\Microsoft\VC\v160\Microsoft.MakeFile.Targets(44,5): error MSB3073: The command ““C:\Program Files\Epic Games\UE_4.26\Engine\Build\BatchFiles\Build.bat” ToonTanksEditor Win64 Development -Project=“C:\Users\Documents\Unreal Projects\ToonTanks 4.26\ToonTanks.uproject” -WaitMutex -FromMsBuild” exited with code 6.

I also had this problem. What worked for me was to go into the editor and select File → Refresh Visual Studio Project.

After that I was able to build the project without issue.

didn’t work for me…

I am having the same problem trying to build 4.27 from Source. I get the same error. Did you ever find a solution?

Right-click on the Solution in VS2022 Solution Explorer and select Batch Build, Choose the Clean button, and then rebuild the project. Remember to restart the editor after the successful build.

1 Like

I had the same issue on UE 5.1.0/Rider 2022.2.4 and it started when I enabled Live Coding. Disabling it resolved the issue.