An illustrated journey through the capstone

The Commerce Menagerie

One glossary. Two merchants. A careful buyer.
Follow the messages from known origins to a prepared checkout — and see what happens when capabilities change.

The seven participants

UCPCourse policyEvidenceLocal / simulator

Swipe the diagram to see all seven lanes. The inspector below includes every message.

Space: play / pause · ← →: step · Home: restartIllustrated source trace · no network calls

What this journey establishes

The capstone verifies merchant authorization over checkout responses and prepares an AP2-locked handoff at ready_for_complete. A merchant profile describes capabilities; it does not establish merchant identity.

User consent, Checkout and Payment Mandates, Complete Checkout, payment, order placement, fulfillment, and settlement are outside this capstone. AP2 here names the negotiated extension; no mandate is generated.

Reading the plates

The animals are original SVG illustrations. UCP is represented by messages and routes. The whale is the buyer orchestration; the owl represents the published platform profile. Negotiation is a local computation in the buyer code.

All prices and outcomes follow repository fixtures. Origin names are role aliases for ephemeral local HTTPS addresses. Message snippets show selected fields, not complete wire documents or captured traffic. Course metadata, policy, and derived records are explicitly labeled. The animation compresses time.

Catalog order remains merchant-owned. The comparison creates no global rank, performs no currency conversion, and uses no Atlas Search. Catalog prices are observations, not transactional commitments. Source references in the notebook identify the Course 5 implementation files, snapshot 60fdf41. The course repository requires access; source files are not hosted on this page.