Assuming the package names are actually clang15 and clang16, there should be no problem. Those are two independent packages and Pungi doesn't know that in fact they are different versions of the same software. If both are tagged in the source koji tag, both would be included in the final compose (as long as either comps or additional_packages or some dependency pulls them in).

15 and 16 are just different version numbers of one package, not two independent packages. At present, pungi seems to be able to only integrate into the latest version of one package.

Both versions of the package are tagged in the source koji tag, but it dose not work

If they both have the same name and differ only in version, then only one will be included in the compose. Pungi takes the latest package from the Koji tag (latest doesn't mean highest version, but last to be tagged). You can see the list of latest packages with Koji client like $koji list-tagged --latest --inherit $compose_tag. This is pretty close to what pungi does.

There is no option to change this.

Also note that the final repository would not be very user friendly. If someone installed clang-15 from there, any future call to dnf update would replace it with clang-16. Users would need to either very carefully upgrade, or use versionlock, or some other external measure to ensure they stay on the desired version.

This issue has been migrated to Fedora Forge:
https://forge.fedoraproject.org/pungi/pungi/issues/1730

Please continue any further discussion there.