Passing CRM ID in NICE CXone Web Messaging SDK startChat() payload

I’m trying to inject our internal CRM customer ID into the Web Messaging SDK session so it lands in the interaction data immediately.

I’m using the startChat method from the @nice-dcx/web-messaging-sdk. The docs say you can pass a customAttributes object, but nothing is showing up in the Architect flow variables or the conversation history.

Here’s the I’m using:

const config = {
 deploymentId: 'my-deployment-id',
 customAttributes: {
 crmId: 'CRM-12345-TEST'
 }
};

const session = await sdk.startChat(config);

I’ve verified the deployment ID is correct. The chat connects fine. I can see the standard browser user agent and IP in the flow data. The crmId is just… gone.

I tried adding it to the userData field as well. Still nothing.

Is customAttributes only for the initial connection handshake and not passed to the flow? Or do I need to use a separate API call after the session starts to attach this data? The SDK version is 4.2.1.

Any ideas on why this specific key-value pair is being dropped?