OTel span propagation failing on POST /api/v2/conversations/calls outbound initiation

Trying to trace outbound calls initiated by an agent via POST /api/v2/conversations/calls. The parent span starts in the Data Action, but the child span in Jaeger shows trace_id: 0000.... I’m injecting the traceparent header into the request body’s traceContext field, yet the trace breaks. Is the Conversations API ignoring the header injection? Here’s the payload:

{
 "traceContext": {"traceparent": "00-8af..."}
}

What am I missing?