Feature flag migrations often stall due to three core challenges: evaluation logic parity between systems, configuration synchronization during the migration window, and confirming cutover safety. Running two systems in parallel is safe and enables incremental migration. The recommended approach starts with auditing flags into zombie, short-lived, and long-lived categories, then redirecting all new flags to the new system, letting short-lived flags expire naturally, and carefully cutting over long-lived flags. To verify parity before cutover, teams can use a wrapper function that evaluates both systems asynchronously and logs discrepancies, or use OpenFeature's ComparisonStrategy for shadow mode evaluation. Mismatch metrics should be tracked on a dashboard showing evaluation counts, mismatch rate trends, and timestamps. A brief configuration freeze of 24–48 hours before cutover ensures the validated state matches production.
