AI Failure Modes — Cursor Demo Repo

Companion sample app for the AI Failure Modes Cursor Examples exercise. Each of the five failure modes from the deck has a pre-staged target somewhere in this repo. Open it in Cursor, run the bad prompt, watch it fail, then run the fix.

Setup

npm install
npm run dev

Browse to http://localhost:5173. Three pages: Dashboard, Orders, Users.

Stack

Vite + React 18 (plain JavaScript) + react-router. Frontend only — mock data, no backend, no database. Keeps the demo fast.

What is deliberately missing

These omissions make the failure modes land. Do not add them before the workshop.

• No AGENTS.md / CLAUDE.md — Cursor has zero project context.
• No glossary or docs/ubiquitous-language.md.
• No tests, no test runner.
• No spec for any feature.
• Pricing logic is split across three files on purpose.

Demo map

Failure mode 1 — AI didn't do what I wanted

Target: src/pages/UsersPage.jsx, src/components/UserCard.jsx Bad prompt: "Add a way for users to upload a profile picture." Cursor will pick storage, image size, format, upload UI, and DB schema for you, all without asking. Then run the Grill Me prompt from the exercises doc.

Failure mode 2 — AI is too verbose

Target: src/data/orders.js, src/services/cart.js Bad prompt: "Add a way to refund a transaction." This codebase calls it a credit, not a refund, void, or reversal. Cursor will invent its own term. After it does, ask Cursor to scan for domain terms and write docs/ubiquitous-language.md, then re-run.

Failure mode 3 — Built right, but it doesn't work

Target: src/utils/dateRange.js (stub — throws "Not implemented") Bad prompt: "Implement a function that returns true if two date ranges overlap, and false otherwise." Cursor will write 30+ lines confidently and miss at least one edge case. Drive the fix with the TDD prompt from the exercises doc.

Failure mode 4 — Codebase is hard to test

Target: src/services/cart.js, src/helpers/discount.js, src/utils/calc.js Bad prompt: "Add a 10% loyalty discount that stacks with existing promotional discounts but caps the total discount at 30%." Watch Cursor edit three files. Then run the refactor prompt to consolidate into a deep src/pricing/ module with one public function.

Failure mode 5 — My brain can't keep up

Target: src/pages/DashboardPage.jsx (the disabled "Export CSV" button) Bad prompt: "Add a CSV export feature to the orders dashboard. Users can pick columns, the export runs in the background, and the result is emailed to them." Cursor will dump ~600 lines across many files. Re-run with the interface-first prompt — review only the public surface.

Pre-workshop checklist

• No AGENTS.md (mode 1 ready)
• No glossary file (mode 2 ready)
• dateRangesOverlap is an unimplemented stub, no tests (mode 3 ready)
• Pricing split across utils/, helpers/, services/ (mode 4 ready)
• Disabled CSV export button on dashboard (mode 5 ready)
• Test each demo end-to-end the night before. Don't improvise on stage.

Reset between demos

git stash    # before demo: stash any prior demo edits
git checkout .   # nuclear reset to staged state