There are some changes to consider if you override the global processWorkflowMessage() routine, which is required in many use cases.
In the older version, the global processWorkflowMessage() routine (in Utils.js), included either inline code changes, or customizations in the customBefore…() and customAfter…() callback routines. In the new API, inline code changes reside in the hwc.processDataMessage() routine (also in Utils.js). The callback routines still have similar names.