A single UI change at Apple Card created a dead state that quietly swallowed valid disputes. The bill: $89 million. In 2020, Apple added a second form to its dispute flow. If a customer reported a problem but skipped the follow-up form, the dispute was marked incomplete. Nothing reached Goldman Sachs. No investigation. No acknowledgment letter. The customer still owed the charge. Under Reg Z, many of those first reports were valid billing error notices — the kind a bank must acknowledge within 30 days and resolve within two billing cycles. Instead they sat in a state the workflow could enter but never leave — FormA submitted, FormB pending, no transition to "investigation started." A TLA+ model checker finds that dead end in seconds. The CFPB found it in October 2024. This isn't an Apple problem. It's a state-machine problem. Large issuers have 10–15 systems touching one dispute — network portal, case management, ledger, credit reporting. Every API change opens a new path, and any can dead-end. Testing checks the paths you thought of. Formal verification checks all of them — it walks every reachable state and proves no dispute can stall past its legal deadline. Not monitoring after the fact. Proof before deployment. That's the layer we build — against Reg Z, Reg E, and the Visa/Mastercard clocks colliding on one dual-network card. If you run disputes: how would you prove to your board that none can be silently dropped between two of your systems? #RegTech #AICompliance