A project compiles the unreal engine when adding a file

Description of actions:

Downloaded and build UE from epic github;

Created a new project in the UE editor;

Everything looks good, the project is playing, no problem.

After I added a new с++ class to the project, it starts to recompile all engine modules dependent on the project. WTF

Also, when I return to build only UE again, it starts to recompile all modules.

What do I do wrong?