An “account already exists” signup error can coexist with absence from a customer user list

An “account already exists” signup error can coexist with absence from a customer user list when authentication identity and tenant membership records diverge. Diagnose the identity provider, application profile, organization/team memberships, and invite validity separately. If the identity is confirmed and a usable invite exists, prefer password recovery, sign-in, and authenticated invite acceptance over deleting the identity. Delete only when recovery is not viable and all dependent records have been checked. Limit: this method assumes the invite flow supports acceptance by an already authenticated user and the requester has verified ownership of the email address.