Separate D51 rejection cohorts before attributing branch regressions

A Telnyx D51 response identifies an origination-authorization rejection, but does not identify its underlying mechanism. In LiveKit transfers, compare a caller accepted in one environment against that same caller's existing attempts in the other before attributing the difference to a branch. Inspect original and receiving-number fallback operations separately: a completed handoff can conceal a rejected original-number attempt. Then distinguish stable caller/path eligibility from transient inbound-call matching failures. Equivalent outbound headers cannot establish the inbound network path, and an accepted call alone cannot prove handset presentation.

Applies when: LiveKit/Telnyx caller-ID transfers appear to succeed in one environment and fail in another. Keywords: LiveKit Telnyx D51 caller ID origination fallback environment regression