This is expected for the master builders. All child builds scheduled by the given master will have cbb_master_buildbucket_id == id of the master.

This is because all properties and tags have to be defined when issuing the buildbucket request, and the buildbucket id isn't known until the request completes.

That makes sense, seeing as the tags are just a string[]. So we should just take "None" to mean null in tags. This still needs to be handled by the CI API though, as the tags we care about are parsed into first-class Proto fields like `Build.parent_id` and we don't want every client to be surprised by the appearance of "None" instead of null.

This seems like a bug in the tag generation code; "None" is a python-specific implementation detail. It should either omit the tag or have an empty value like for cbb_email in that result.

Oh.. you mean a literal "None". Yes, that is a bug. I revamped the relevant code a few months ago, and I think the current version should be resistant to that behavior since it explicitly filters empty properties/tags.

Are you seeing this only on builds that ran a long time ago? Branched builds? Or TOT?