Paper: Nubank cuts AI agent update cycles from 3 weeks to under 5 days

The paper presents a hypothesis-driven simulation workflow using the Snowglobe simulator to screen candidate customer-experience agents before deployment, tested on Nubank's Card Delivery agent and its successor Card Management. Across 4 deployed versions, simulated and production version-level binary evaluator scores showed high correlation, and simulation-guided iteration raised transactional net promoter score by 36.69 points in a live A/B test. Screening open-weight configurations in over 16,000 simulated conversations led to a model that increased self-service rate by 8.82 percentage points in a subsequent live A/B test, with no statistically significant change in tNPS.