How One Developer Solved White-Label SaaS Authentication With a Single Field

A developer building VoiceDash, a white-label AI voice agent platform for agencies, found that authentication — not AI or billing — was the most complex engineering challenge. The platform must serve two distinct user types: agency staff who manage clients and billing, and client members who only see their own branded portal. To avoid maintaining two separate auth systems, the developer used a single NextAuth CredentialsProvider with a 'type' discriminator field that routes login logic into two distinct branches. Agency users authenticate with email and password, while client members can log in via a unique login ID with an optional password. The core security requirement is strict isolation — a client member must never access agency routes or another client's data, as any breach would fundamentally undermine the business.