BalanceUnderflowException

Exception thrown when balance would go negative (double-spend or invalid event).

Why This Matters:

• Negative balance indicates double-spend attack or corrupted event stream

• MUST NOT silently set to zero (masks critical errors)

• Wallet MUST stop processing and alert user

Recovery:

• Clear event cache

• Re-sync from blockchain

• If persists, report to indexer operator (potential attack)