The story
InboxFlow runs entirely as a content script on mail.google.com. The hard requirement was that it could not break Gmail's own UI when Google ships A/B test changes (which happens roughly every two weeks).
We wrote a tolerant DOM observer that scopes its mutations narrowly and falls back gracefully when Gmail rolls out a UI change. The extension layers a triage sidebar on the inbox, with categories you can train per-account. OAuth for the underlying API runs in an offscreen document so the popup never interrupts a user mid-action.
