How do I migrate existing workflows with external API calls to Diagrid Catalyst without breaking exactly-once guarantees?

Audit each external API call for idempotency. If calls are already idempotent, migrate directly. If not, add idempotency keys or reconciliation steps before migration. Catalyst replays activities on failure, so non-idempotent calls risk duplicates. Test with simulated failures. Use Catalyst's workflow state to track call status. No automatic exactly-once; you must design for it.