Question
You've joined a team owning a 400k-line Ruby on Rails monolith and you need an AI agent to add a new billing-proration feature. The agent's first attempt invents a PricingService that doesn't exist, duplicates logic already in app/services/billing, and ignores the team's convention of routing all money math through a Money value object. Describe how you'd give the agent the right CONTEXT so it succeeds, and what specifically went wrong on attempt one.
Treat the AI’s output as a draft to verify, not an answer to trust. Name the specific flaw and the input that triggers it, say how you’d catch it — tests, edge cases, reading critically — and how you’d re-prompt or decompose to get it right.
Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.