SIP INVITE drops on outbound Studio flow with 488 error

Voice & Telephony
1

The outbound flow routes to a SNIPPET action that injects P-Asserted-Identity via REST Proxy to /api/v2/telephony/sessions. Studio 4.2.1 clears the first leg. Then the proxy returns 488 Not Acceptable Here with reason=bad_sip_header.

Stepping through the JSON payload, the structure’s valid. The UCMA layer just strips the custom header before the trunk processes it. Debug traces show jack all on the SIP stack. Header injection keeps choking on the outbound pipeline.

2

“headers”: {
“P-Asserted-Identity”: “tel:+1234567890”
}


Stop using `telephony/sessions` for outbound header injection. That endpoint is for inbound session control. You need to set the `AssertedIdentity` in the `fromNumber` object of the `CreateOutboundSession` call or use the `SIP Header` field in the flow's dial action. The proxy strips it because it's not a valid session parameter.