The repository daemon module registration is based on scanning for (jar) archive Manifest Hippo-Modules entries.
This works fine when running (or testing) based on an actual jar archive (as a project dependency) within IntelliJ.
However, when the (Maven) module providing the daemon module itself is part of the IntelliJ project (or loaded as additional module), this currently fails.
IntelliJ then will build the (test)runtime classpath based upon the project/module build target classes and test-classes folders, not the artifact jar file.
The needed MANIFEST.MF classpath resource then is not available at runtime and the daemon module won't be activated.
To fix this problem, the maven-jar-plugin configuration for the module will be changed to point to a custom Manifest file (fragment).
This custom Manifest file will be automatically merged into the final MANIFEST.MF for the jar artifact, as documented at the Maven Archiver website.
This custom src/main/resources META-INF/MANIFEST.MF file, containing (only) the Hippo-Modules entry, will then also be available when running/testing from within IntelliJ, and the daemon module detected and activated.