Look into generating a big warning when a tag is created for a draft that doesn't exist. The current error message is a little obtuse, to say the least. It's a little fiddly to do so, but it's probably worth it as a usability enhancement.
Consider whether it makes sense to fail in this case. I think that it probably makes sense to fail, or the warning is less likely to arrive in inboxes. The downside of a failure is that it might be necessary to delete spurious tags before adding the correct tag or the build errors will persist. With a warning, this instructions for fixing the problem might be included.
Look into generating a big warning when a tag is created for a draft that doesn't exist. The current error message is a little obtuse, to say the least. It's a little fiddly to do so, but it's probably worth it as a usability enhancement.
Consider whether it makes sense to fail in this case. I think that it probably makes sense to fail, or the warning is less likely to arrive in inboxes. The downside of a failure is that it might be necessary to delete spurious tags before adding the correct tag or the build errors will persist. With a warning, this instructions for fixing the problem might be included.
See https://github.com/httpwg/http-extensions/issues/1338 for an example of how this might happen.