Dll.response missing


I came across a serious issue for me.
I’m getting an error while compiling (in Editor and also out of VS) that says the "
\Intermediate\Build\Win64\ProjectName\UE4Editor-ProjectName-9596.dll.response" file is missing. I checked the folder and this is correct. But I’m speechless why.
This has happened now several times and everytime I could get my backup running. However it worked last night without a problem and while starting the project today, I got this error.
I even zipped my working project yesterday. (I dad this bug yesterday as well, so I went ahead and used my old backup to get it working without the bug and continued zipping this running project).
I also checked the given folder in my backup and it’s filled with with a massive amount of files “Project-9595.dll”, “project-2423.dll” etc.
In the current project (with the given error) the folder is empty but 3 files remain:

  1. ProjectName.exe.respone
  2. Makefile.ubt
  3. UnrealHeaderTool.manifest

as I said all other files are missing (see picture)
left-side = current project
right-side = zip of current project from last night


This is SUPER ANNOYING as I have to create a backup like every time I change something, because I can’t be sure the version will still be working the next day. It seems that something causes Unreal to delete all these files. :o

Is there anything that could possible cause this? Or even better: Is there anything that can prevent this?

Thanks for reading,


P.S: This only happend to me in 4.9.1

The numbered dlls are work of hot reload, compiler can’t modify dll when it’s running so UBT creates new dll with number and order engine to unload old dll and load new one.

If you get some error from it, try building without editor open, UBT then deletes all hot reload stuff

Thank you for the explanation.
Unfortunately I get another error when compiling without opened editor. It seems that even the one file (projectname.dll.response) without a number is missing.


where the first line translates into: file XYZ couldn’t be opened.


for those that can’t read it:

Fehler	2	error : Failed to produce item: F:\Dokumente und Einstellungen\Theo\Unreal Projects\CoopBasic 4.9_new\Binaries\Win64\UE4Editor-CoopBasic.pdb	f:\Dokumente und Einstellungen\Theo\Unreal Projects\CoopBasic 4.9_new\Intermediate\ProjectFiles\ERROR	CoopBasic

Fehler	1	error LNK1104: Datei "F:\Dokumente und Einstellungen\Theo\Unreal Projects\CoopBasic 4.9_new\Intermediate\Build\Win64\CoopBasic\Development\UE4Editor-CoopBasic.dll.response" kann nicht ge÷ffnet werden.	f:\Dokumente und Einstellungen\Theo\Unreal Projects\CoopBasic 4.9_new\Intermediate\ProjectFiles\LINK	CoopBasic

Fehler	3	error MSB3073: Der Befehl ""C:\Program Files\Epic Games\4.9\Engine\Build\BatchFiles\Build.bat" CoopBasicEditor Win64 Development "F:\Dokumente und Einstellungen\Theo\Unreal Projects\CoopBasic 4.9_new\CoopBasic.uproject" -rocket -waitmutex" wurde mit dem Code -1 beendet.	C:\Program Files (x86)\MSBuild\Microsoft.Cpp\v4.0\V120\Microsoft.MakeFile.Targets	38	5	CoopBasic

Ok i guess there no other way then delete intermediate directory and build again, it should clean the project

Thanks! It actually seems to work!
For anybody else experiencing this problem, i did the following:

  1. delete /intermediate folder
  2. right clicked the .uproject and selected “generate visual studio files”
  3. right clicked my projectname (under games) and clicked “build”
  4. right clicked it again after getting an error and selected it as startup project.

I also had this problem but it was due to the fact I used a previous project to build off of. I needed to right click my .uproject file and edit the name like so:


Saved My Life. Thank You!!!

Thank you so much! This is a problem in 4.19 as well