Notebook Entry 008
The Authorized Domain Error — Infrastructure Has Gates You Don't See
April 8, 2026
Why does sign-in work on desktop but break on mobile once it's actually deployed?
What happened
Lane Command worked perfectly on desktop (opened as a local file in browser). Deployed to Vercel, signed in on desktop — worked. Tried to sign in on phone — Firebase auth error: "This domain is not authorized for OAuth operations." The Vercel URL (lane-command.vercel.app) wasn't in Firebase's authorized domains list.
Root cause
Firebase auth requires explicit domain whitelisting. localhost is auto-whitelisted, but any custom deployment domain must be manually added.
What changed
Added lane-command.vercel.app to Firebase Authentication authorized domains. Took 30 seconds once identified.
The lesson
Moving from local development to production always surfaces hidden configuration gates. "It works on my machine" is never the full test. Each layer of infrastructure (hosting, auth, database, DNS) has its own set of requirements that only surface when you actually deploy. This is why implementation specialists exist — the technology works; the configuration between technologies is where things break.
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