This project shows 2 issues with kapt3.
To make the results consistent, I suggest to run a "deep clean" when building, like so:
$ rm -rf ./build ./*/build && ./gradlew clean buildYou'll notice if the annotation processor is called correctly by the following log:
warning: *** AP RUNNING ***
By enabling kapt3 in the app project (uncomment here) the annotation processor isn't run unless it's also used as a compile dependency (uncomment here).
By enabling kapt3 in the processor project (uncomment here) the @AutoService annotation processor won't be run and as a result the correct META-INF file won't be generated.