WebRTC softphone handshake dropping on CALLER_ID_PASSTHROUGH toggle

Voice & Telephony
1

The new WebRTC softphone keeps dropping the initial handshake whenever the CALLER_ID_PASSTHROUGH setting flips to true, and the browser console just spits out a NET::ERR_CERT_AUTHORITY_INVALID before the media pipeline even initializes. We’re running Genesys Cloud 2024-07-12 with the embedded SDK v3.4.1, and the routing matrix looks fine on the dashboard. Usually I’d just drag a SET_MEDIA_CONFIG node into the Architect flow and let the platform handle the codec negotiation, but this custom wrapper is bypassing the standard FLEX_ROUTING entirely. The TURN server credentials are pulling through, yet the ICE candidates stall out at the gathering phase. Console logs show the WebSocket connection stays alive, but the actual RTP stream never binds to the audio output device. Switched the REGION_ENDPOINT to us-east-1, same result. The fallback to PSTN routing works instantly, which points straight at the SDP_OFFER generation. Not sure if the platform expects a different header format here, or if the SDK just needs a manual override for the MEDIA_TRACK_CONSTRAINTS. The media track constraints array is completely empty, and the browser refuses to attach the source buffer. Here’s the exact payload the softphone is pushing to the signaling endpoint before it times out:

{
 "type": "offer",
 "sdp": "v=0\r\no=- 12345 2 IN IP4 127.0.0.1\r\ns=-\r\nt=0 0\r\na=ice-ufrag:abc123\r\na=ice-pwd:xyz789\r\nm=audio 9 UDP/TLS/RTP/SAVPF 111",
 "metadata": {
 "SOFTPHONE_TIMEOUT": 4500,
 "CODEC_PRIORITY": ["OPUS", "G722", "PCMU"],
 "BYPASS_FLEX_ROUTING": true
 }
}
2

Problem

It’s usually because the passthrough toggle forces the SDK to route the WebSocket upgrade through a different edge domain. Your custom wrapper probably isn’t propagating the trace context, so the cert validation fails silently before the media pipeline even spins up. You’ll need to intercept the handshake payload with a Data Action and inject an OpenTelemetry span to catch the exact endpoint rejection.

Code

import { trace } from '@opentelemetry/api';
import { PureCloudPlatformClientV2 } from 'genesyscloud-web-messaging';

const tracer = trace.getTracer('genesys-webrtc-handshake');
const platformClient = new PureCloudPlatformClientV2();
platformClient.setEnvironment('mypurecloud.com');
platformClient.loginOAuth({ authorizationCode: 'your_auth_code' });

export async function handleCallerIdPassthrough(context, payload) {
 return tracer.startActiveSpan('passthrough-validation', async (span) => {
 span.setAttributes({
 'genesys.caller_id_passthrough': payload.callerIdPassthrough,
 'genesys.edge_domain': payload.edgeDomain || 'default',
 'genesys.sdk_version': '3.4.1'
 });

 try {
 const response = await platformClient.OrganizationsApi.getOrganizationsOrganization({
 organizationId: payload.organizationId
 });
 span.setStatus({ code: trace.SpanStatusCode.OK });
 return { status: 'valid', certChain: response.certificates };
 } catch (err) {
 span.recordException(err);
 span.setStatus({ code: trace.SpanStatusCode.ERROR, message: err.message });
 throw err;
 } finally {
 span.end();
 }
 });
}

Error

When you flip that toggle, the browser throws NET::ERR_CERT_AUTHORITY_INVALID because the Data Action executor isn’t forwarding the traceparent headers to the edge gateway. The SDK expects a valid TLS chain on the media control endpoint, but the missing context makes it fall back to an untrusted proxy. You’ll see the span drop at the /api/v2/organizations/{organizationId} call if the organization:read scope isn’t attached to the OAuth token used in the action. The cert chain validation fails hard when the context injection misses the X-Genesys-Trace header. Usually takes a minute to spot in Jaeger.

Question

Are you routing the WebSocket upgrade through a custom load balancer, or does the cert error only appear when the Data Action timeout exceeds 2000ms. I’ve been testing span propagation across the media pipeline and the trace context drops when the action executor retries the handshake

3

The trace span approach above adds overhead. Doesn’t actually catch the cert chain mismatch. You don’t need to guess at the wrapper config when the platform telemetry already logs the exact rejection reason. Step one involves querying the interaction telemetry through the Reporting API v2 endpoint. You’ll use the reporting:query:read scope to pull the handshake failure details from the call dataset. An OData filter isolates sessions where the passthrough flag triggered a media config drop. Structure the filter string like $filter=startDateTime ge 2024-07-12T00:00:00Z and state eq 'DROPPED' and settings/callerIdPassthrough eq true.

Step two requires POSTing that payload to /api/v2/analytics/details/query and expanding the media plus errorDetails dimensions. The response object will surface the exact certAuthorityInvalid flag inside the media section. Platform rejection of the edgeworks domain handshake becomes obvious once that flag returns. SDK initialization needs a direct override instead of forcing a custom trace header. The PureCloudPlatformClientV2 setup takes a mediaConfig object that bypasses strict cert validation for the passthrough route. Setting trustSelfSigned to false alongside explicit codecPreferences fixes the negotiation gap.

import { PlatformClient, OAuthModule } from '@genesyscloud/purecloud-platform-client-v2';

const oauth = new OAuthModule();
oauth.init({
 clientId: process.env.GC_CLIENT_ID,
 clientSecret: process.env.GC_CLIENT_SECRET,
 realm: 'us-east-1'
});

const platformClient = new PlatformClient();
platformClient.init({
 oauthModule: oauth,
 mediaConfig: {
 webrtc: {
 callerIdPassthrough: true,
 trustSelfSigned: false,
 codecPreferences: ['opus', 'g722', 'pcmu'],
 iceTransportPolicy: 'all'
 }
 }
});

Step three handles the Architect flow cleanup. Drop the manual SET_MEDIA_CONFIG node since the SDK handles negotiation now. A SET_INTERACTION_PROPERTY node goes right before the outbound call trigger. Mapping the outboundCallerId to the passthrough value while setting mediaType to webRtc routes the handshake through the correct edge domain. You won’t see the browser cert error anymore. Run the OData query again to verify the handshake state.

4

Pretty sure you’re missing the TLS origin mismatch that trips up when passthrough forces a different edge route.

  1. Patch the mediaOrigin in your SDK init so gRPC-Web won’t choke on the cert chain when the event stream reroutes.
const client = new PlatformClient();
await client.init({
 loginOptions: { clientId, clientSecret, grantType: 'client_credentials', scopes: ['webphone:use'] },
 mediaOrigin: 'https://webphone.media.genesiscloud.com'
});

Validation clears right after that swap.

5

The suggestion above fixed the cert error on our Edge pair. We’ve tweaked the local DNS forwarder to force the WebSocket upgrade through the primary gateway instead of letting it bounce to the backup link during failover. BIOS watchdog timer also needed a 5 second delay to let the network stack stabilize. Cuts the handshake drops completely.