Variable: MLFLOW\_TRACE\_ID\_HEADER

const MLFLOW_TRACE_ID_HEADER: "x-mlflow-trace-id" = "x-mlflow-trace-id"

Response header carrying the turn’s MLflow trace id (tr-<hex>), derived from the active OpenTelemetry trace id. Present only when MLflow logging is enabled and a trace was active for the request. The chat client reads it off the stream response and pairs it with the assistant message so a later thumbs / comment attaches to the right trace.