Zendesk Chat to GC Messaging Sync: 409 Conflict on Thread Creation

Looking for some advice on troubleshooting this synchronization issue between Zendesk Chat and Genesys Cloud Messaging during our migration pilot. We are attempting to replicate the Zendesk conversation threading model within GC, but the integration is failing when trying to append new messages to an existing interaction.

In Zendesk, we rely on a single ticket ID to group all messages, regardless of the channel. Our current approach uses a Data Action to fetch the Zendesk ticket and then calls the Genesys Cloud API to create a new interaction. The problem arises when multiple agents reply quickly. The system throws a 409 Conflict: Interaction already exists error.

The request payload looks like this:

{
 "externalId": "zendesk_ticket_12345",
 "type": "chat",
 "from": {
 "id": "user_agent_01",
 "name": "Support Agent"
 }
}

We are using the Genesys Cloud API v2 endpoints. The error suggests that GC is treating the externalId as a unique constraint for the entire interaction lifecycle, whereas Zendesk allows multiple message events under the same ticket ID. In Zendesk, this is handled automatically. In GC, it seems we need to use the interactionId from the initial creation response for subsequent messages, but our Data Action doesn’t store this state effectively.

Is there a recommended pattern for handling this statefulness? We want to avoid creating duplicate interactions for every single message, which would break our reporting and make the customer experience disjointed. The current workaround of checking for existing interactions before creating a new one adds too much latency and complexity to the Architect flow. We are operating in the eu-west-1 region. Any insights on how to properly map Zendesk’s ticket-based threading to GC’s interaction-based model without hitting these conflicts would be greatly appreciated.