Lab: One door, an audit trail and a kill switch

Module 12 · Lab · About 80 minutes · Needs: the Module 3 lab's tools.py, and lessons 1, 2 and 3 (quote_untrusted and the trust boundary; the Policy layer and its checks; AuditLog, check_claim and escalation packets)

What you are building

It is Friday 29 May 2026, week 7, the day after Sam's red-team session. Shadow mode starts on Monday. The three lessons built the controls in notebook cells; this lab moves them into the returns-desk/ repository as two files. returns_desk/policy.py, the file the course guide names for this module, holds Lesson 2's Policy: one door with ordered checks for least privilege, approvals, egress, limits and the kill switch. returns_desk/oversight.py holds Lesson 3's audit trail, the claim check, escalation and plain-words explanations, plus the run loop that wires them together. Both import Module 3's tools.py and never replace it. Tom's R-1008, with its planted note, tests every control. Everything at BrightCart is simulated.