Digital Messaging API 400 on BYOC Trunk Context

General Discussion
1

Anyone know why the Digital Messaging API is returning a 400 Bad Request when attempting to route inbound WhatsApp messages to our primary queue? We recently migrated fifteen BYOC trunks to handle unified voice and digital traffic, and while voice routing remains stable, the digital channel is failing at the initial ingestion point.

The error occurs specifically when the platform attempts to resolve the outbound routing context for the digital session. The payload seems valid according to the schema, but the backend rejects it with a generic validation error. This is happening exclusively for trunks configured in the AP-SG region. Other regions like US-EAST-1 are processing digital messages without issue.

Here is the trunk configuration snippet from the Architect:

trunk_config:
 id: "byoc-trunk-ap-sg-01"
 region: "AP-SG"
 type: "BYOC"
 capabilities:
 - "voice"
 - "digital"
 digital_settings:
 whatsapp:
 enabled: true
 business_account_id: "wa-ba-sg-12345"
 failover_strategy: "carrier_specific"
 outbound_routing:
 default_queue: "digital-support-sg"
 fallback_queue: "digital-overflow-sg"

The SIP registration status shows as healthy, and the WhatsApp Business API webhook is receiving the delivery receipts correctly. However, when the platform tries to create the session object, it throws a 400. I have verified that the Service Account has the necessary digital:messaging:write scopes. The issue persists even after clearing the local cache and re-deploying the flow version 4.2.1. It feels like a mismatch between the BYOC trunk metadata and the digital channel provisioning logic. Has anyone encountered similar issues with carrier-specific failover strategies in the digital context?

2

This issue stems from the digital channel payload lacking the specific trunk context required for unified routing.

The API expects a routingContext object within the message body when using BYOC trunks. Without it, the platform cannot map the inbound session to the correct queue.

"routingContext": {
 "trunkId": "your-byoc-trunk-id"
}

Add this to your payload. The 400 error should resolve immediately.

3

If I recall correctly, the routingContext object needs the trunkId string, not just the ID. Also, double-check your channelId matches the digital messaging channel in the admin console.

4

This looks like a valid fix for the immediate 400 error, but be careful with BYOC digital trunks. The routingContext often requires a providerName alongside the trunkId to resolve correctly in multi-org setups. Missing this can cause silent failures later.

"routingContext": {
 "trunkId": "id",
 "providerName": "your-provider"
}