Can anyone explain why the Agent Scripting API is returning a 400 Bad Request error when attempting to inject custom SIP headers into an active call leg managed by our APAC BYOC trunks? We are using the PATCH /api/v2/interactions/interactions endpoint to update the channel properties with a custom X-Carrier-Route header intended to trigger specific failover logic on our Singapore-based carrier side. The request payload includes the correct interaction ID and the updated channel configuration, yet the platform consistently rejects it with the error message: Invalid channel update: SIP header injection not permitted for BYOC trunk type. This is happening on Genesys Cloud version 24.2.1, and we have verified that the OAuth client possesses the interaction:write scope.
The issue appears isolated to outbound interactions routed through our 15 BYOC trunks in the Asia/Singapore region, while standard inbound calls or those routed via Genesys-provided trunks allow similar header modifications without issue. Our carrier requires this specific header to differentiate between primary and secondary path traffic for their failover mechanism, and the current behavior is causing a mismatch in our analytics reporting regarding call path utilization. We have attempted to replicate this using the Platform API explorer and our internal Python SDK wrapper, both yielding the same 400 response. The SIP registration status for these trunks is stable, and no recent changes have been made to the trunk configuration or RBAC policies that would restrict this action. Is there a known limitation or a specific configuration flag within the BYOC trunk settings that needs to be enabled to allow dynamic SIP header manipulation via the Agent Scripting API during an active session?