Architect Data Action fails to resolve Web Messaging participant attributes

Architect & Flows
1

Trying to map interaction.participant.attributes in an Inbound Message flow to a Data Action. The flow hits the external API, but the payload shows null for all custom attributes set via the Web Messaging widget. I’ve verified the attributes exist in the Conversation API response (/api/v2/conversations/messaging/{convId}/participants). Here’s the mapping JSON:

{
 "requestBody": "{{interaction.participant.attributes.customerId}}"
}

Is there a specific delay or refresh needed for these attributes to propagate to the Architect context?