OAuth Failure Recovery: Why I Choose Safe Retries for Authorization and Callback Steps

Short answer: Retry the transport operation, never the OAuth meaning: keep one durable authorization attempt, accept its callback once, and make every downstream effect replayable from recorded state. For a B2B SaaS account-deletion flow, I would block new sessions before attempting remote cleanup, because deleting data while a surviving session can still act is the more dangerous ordering. That is the architecture decision. It treats a timeout as missing knowledge, not proof of failure. A callback may have committed even when the browser received no response; a token exchange may have reached the other side even when the connection closed; an account deletion may be retried by a worker after its first lease expires. The recovery design must therefore answer a narrow question at each boundary: do we know the operation did not happen, do we know it happened, or is the result still unknown? What must remain true during OAuth failure recovery? The first invariant is that an authorization attempt has one identity independent of any HTTP request. Store an opaque flow identifier, the expected callback state, the account or tenant context, a creation time, an expiry, and a small state machine such as pending , exchanging , succeeded , or failed . Don't let a browser refresh create a second logical attempt merely because it creates a second request. The second invariant is single consumption. An authorization code and its state belong to one attempt; the callback handler must atomically claim that attempt before triggering side effects. A duplicate callback should read the previously recorded outcome and return the same application-level destination. It must not provision the user again, issue another internal session, or append a second audit event that claims a second login. Exactly once is the goal, but HTTP cannot promise it by itself, so I use an exactly-once mindset at the business boundary: an atomic database transition establishes who owns the work, unique constrain