With gradle task flowCopyFrontendResources as registered in webapp/build.gradle.kts, the following steps bring a working productionMode:

1. ./gradlew clean
2. ./gradlew webapp:vaadinBuildFrontend
3. run main method in WebApp.kt

Without gradle task flowCopyFrontendResources, there's one of the following two cases:

Case 1: Production from blank state

1. ./gradlew clean just to be sure; now webapp/build is non-existent
2. Make sure webapp/build.gradle.kts has vaadin { productionMode = true }
3. ./gradlew webapp:vaadinPrepareFrontend, then observe the following:
   • webapp/build/flow-frontend/styles only contains mybutton.css but not mytextfield.scss
   • webapp/build/resources is non-existent
4. ./gradlew webapp:vaadinBuildFrontend fails due to

   Failed to find the following css files in the node_modules or /Users/manuel/Repos/multiprojectgradletest/webapp/frontend directory tree: - ./styles/mytextfield.scss

Case 2: Production after DevMode

1. ./gradlew clean
2. Make sure webapp/build.gradle.kts has vaadin { productionMode = false }
3. run WebApp to initiate building the frontend, then observe the following:
   • build/flow-frontend/styles contains mybutton.css and mytextfield.scss
   • build/resources only contains the flow-build-info.json
4. Make sure webapp/build.gradle.kts has vaadin { productionMode = true }
5. run gradle webapp:vaadinBuildFrontend and observe:
   • build/resources now contains some more files
6. (re)run WebApp, now the production mode seems to work