Is there a guarantee on the bug fix?

Yes. Every fix ships with a regression test that pins the bug closed, and we include 14 days of free cover, if the exact same bug resurfaces in that window, we fix it again at no charge. We also fix on a feature branch you review, so you approve the change before it ever reaches production. We don’t guarantee unrelated new bugs, but we do guarantee the one we were hired to kill stays dead.