The knowledge sources don't contain specific information about which Mixpanel plans include the Mirror feature (Warehouse Connectors' Mirror mode). The available documentation about Mirror describes what it does — keeping Mixpanel data in sync with your data warehouse by reflecting additions, updates, and deletions — but doesn't specify plan availability or any recent changes to plan eligibility for this feature. [Mirror intro]
For accurate and up-to-date information on which plans include Mirror, I'd recommend:
