Run

./gradlew jar

Then inspect the file ./build/lib/gradle-manifest-multibyte-demo.jar/META-INF/MANIFEST.MF. Some multibyte characters are cut apart, because each line ends at exactly 72 bytes.

A copy of that MANIFEST.MF can be found at src/main/resources/MANIFEST.MF.

Run

./gradlew run

You will see an analysis of both files src/main/resources/MANIFEST.MF and src/main/resources/MANIFEST2.MF (identical files, the first with cut UTF-8 characters, the other one has all characters intact). First you see how the attributes are represented when you deserialize the manifest using the java.util.jar.Manifest class from Java (identical for both files). Then you see how the same class serializes the manifest (also identical).

The JAR File Specification states that the lines in a MANIFEST.MF file must be no longer than 72 bytes (explicitly not 72 characters). It does not explicitly say if it's ok to split multibyte characters.