Chargeback dispute handling

Design the chargeback/dispute handling system for a payment processor. Card networks send dispute events (chargeback initiated, evidence-due, representment outcome, second presentment, arbitration) via async files/webhooks with strict deadlines. When a chargeback hits, funds must be debited from the merchant immediately (or from their reserve), evidence collected, and the outcome posted back to the ledger, possibly reversing the debit if the merchant wins. ~50K disputes/day. Describe the state machine, the money movement, and how you keep ledger and dispute state consistent.