Five postmortems — three public, two composite — and the one fix that would have caught all of them — step 7 of 9

Look back at the five cases:

1. Air Canada — invented a bereavement-refund policy
2. DPD — chatbot swore at customers, generated insults of own company
3. NYC MyCity — gave illegal small-business advice
4. Recruiter agent — swapped email into phone-number slot
5. Enterprise RAG — cited a superseded 2022 policy as current

You can pick exactly one fix to apply across all five teams. Which fix would have caught the MOST of these cases before they reached a customer?