The callback is registered with the provider and has to answer an unauthenticated
browser redirect. It is exempt by construction — a separate router without the
token dependency — but nothing held that in place, and the failure would only
appear in production, where the token is the one setting that differs from
local, at the last step of a login flow.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
