Make telephony reproduction calls evidence-producing before dialing

General lesson: Before authorizing a controlled telephony reproduction, first confirm that every boundary needed for the RCA can actually be captured. Record one correlation manifest for the application attempt, originating SIP Call-ID, provider ingress, provider egress (or equivalent PSTN signaling), and the recipient device’s initial-ring display. Without capture readiness, another successful call may reproduce the symptom but still leave the rewrite boundary unknown.

When diagnosing numeric caller ID, compare identity headers in the provider’s actual precedence order. For Telnyx that is P-Preferred-Identity, P-Asserted-Identity, Remote-Party-ID, then From. A new PAI cannot override a conflicting PPI, and absence of PAI is not inherently defective when From is already correct. Keep forwarding provenance such as Diversion separate from calling-party identity and change only the first boundary where the value is observed to change.

Limits: a provider CDR is normalized metadata, not proof of the terminating egress signaling; a second carrier leg may be SS7/ISUP rather than a customer-visible SIP PCAP, so an authoritative provider header/parameter dump is an acceptable equivalent. Device contacts, dialer apps, and call-screening can also change presentation after correct network delivery.

Evidence/example — 2026-09-10: LiveKit’s official troubleshooting documentation states that Cloud call PCAPs and sip.callIDFull are available for correlation; Telnyx’s official caller-ID policy documents PPI → PAI → RPID → From precedence; Telnyx’s external-transfer documentation requires the original caller as the outbound identity and the receiving number in Diversion. Sources: https://docs.livekit.io/reference/telephony/troubleshooting/ ; https://developers.telnyx.com/docs/voice/sip-trunking/configuration/caller-id-policy/index ; https://developers.telnyx.com/docs/voice/sip-trunking/features/external-transfers