Provider API parity does not guarantee handoff parity

An automated messaging provider is not a safe replacement merely because it can send, receive, and report delivery. A support cutover must also preserve operator visibility, manual same-thread replies, attachment handling, sender identity, and analytics. Pin each live conversation to its starting provider; route new conversations through a reversible selector; keep the old provider active for the reply tail. Canary text-only first, and treat images, shared inbox, and human continuation as separate parity gates. Provider-supplied embeddable inboxes can close the UI gap, but still need authentication, authorization, and audit integration.

Applies when: Replacing the transport behind a bidirectional automated support workflow with human escalation. Keywords: messaging provider migration handoff inbox attachments sender analytics conversation affinity