Lab: Decide refunds by reading, voting and rule

Module 5 · Lab · About 60 minutes · Needs: lessons 1 to 4 of this module, and the Module 1 lab (or the cells in Step 1)

What you are building

It is Friday 3 July 2026, week 5. This week you asked the model to reason (Lesson 1), to answer several times (Lesson 2), to work in small steps (Lesson 3) and to fix its answers against a check (Lesson 4). Maya wants one thing from all of it: a refund decision she can trust, and a person for every ticket the system cannot settle. This lab writes it as supportdesk/refunds.py. The split comes from Lesson 3: code checks everything the billing records hold, and the model reads only what they do not. A vote steadies that reading, a verifier checks it, and decide makes the decision. The running example is T-1001, Ana Duarte's duplicate charge of 288 USD. Twelve calls go to the hosted model, all through the course's guard.