Codex prompts: how to get the most from OpenAI Codex

"Add rate limiting middleware to src/middleware/. Limit each IP to 100 requests per 15 minutes, return 429 with a Retry-After header, store state in Redis. Don't modify existing middleware files."

"Implement CSV export for the reports table in src/pages/reports.tsx. Add an 'Export CSV' button next to the existing filters. Use the server-side data, not the client-side table state. Handle up to 50k rows without blocking the UI."

"Add email verification to the registration flow in src/auth/. Send a verification link via the existing SendGrid integration, store the token hash in a new verification_tokens table, and block login until verified. Update the Prisma schema."

"Implement dark mode toggle in the settings page. Use CSS variables defined in globals.css, persist the preference in localStorage, and respect the system preference on first visit. Update all components that use hardcoded colour values."

"Add pagination to the /api/users endpoint. Accept page and limit query params, default to page=1 and limit=20. Return total count and total pages in the response. Update the corresponding React component to render page controls."

"Fix the race condition in src/services/orderService.ts where concurrent requests overwrite the cart total. Use an atomic update or pessimistic lock. Don't change the public API surface."

"Fix the memory leak in src/workers/notificationWorker.ts. The event listeners are being added on each reconnect but never removed. Clean up listeners in the disconnect handler. Add a test that verifies listener count stays stable over 100 reconnect cycles."

"Fix the timezone handling in src/utils/scheduler.ts. Events created in UTC+1 are showing an hour late in UTC. Use date-fns-tz to parse and format dates consistently. Ensure all existing tests still pass after the fix."

"Fix the Safari-specific layout break in src/components/Dashboard.tsx. The CSS grid collapses on viewports between 768px and 1024px. Use a flexbox fallback for that breakpoint range. Don't change the desktop or mobile layouts."

"Fix the flaky test in tests/integration/payment.test.ts that fails intermittently on CI. The mock server timing is the likely cause — increase the timeout and add retry logic for the webhook delivery assertion."

"Refactor src/routes/api.ts into separate route modules under src/routes/api/. Split by domain: users, orders, products, auth. Each module gets its own validation schema. Keep all existing endpoints responding on the same paths."

"Convert src/store/ from Redux class-based actions to Redux Toolkit slices. Keep the same state shape and action names so consuming components don't need changes. Run all tests after conversion."

"Replace all instances of moment.js in src/ with date-fns. Update imports, rewrite formatting chains, and ensure the 40+ date displays in the app produce identical output. Remove moment from package.json when done."

"Extract the repeated pagination logic from src/handlers/ into a shared src/utils/pagination.ts helper. Accept page, limit, and total as params, return offset, hasNext, and hasPrev. Update all 8 handlers that duplicate this logic."

"Migrate the database queries in src/reports/ from raw SQL to the existing Prisma ORM. Keep query performance within 10% of the raw SQL baseline. Don't touch the report calculation logic."

"Write integration tests for src/routes/auth.ts covering: successful registration, duplicate email rejection, successful login, wrong password rejection, token refresh, and token expiry. Use the existing test database setup in tests/helpers/."

"Write unit tests for src/utils/validators.ts. Cover every exported function with valid inputs, invalid inputs, edge cases (empty strings, unicode, very long values), and the exact error messages returned. Aim for 100% branch coverage."

"Add snapshot tests for all 12 components in src/components/forms/. Render each with default props and with error states. Store snapshots in __snapshots__/ alongside each component."

"Write E2E tests for the checkout flow: add item to cart, proceed to checkout, fill shipping info, select payment, confirm order, verify success page. Use Playwright with the existing config in playwright.config.ts."

"Add load tests for the /api/search endpoint using k6. Test with 50, 200, and 1000 concurrent users. Measure p50, p95, and p99 latency. Write the test script to tests/load/search.js."