Debug apps that work in development but fail in production
The 'works on my machine' problem stems from differences between your local environment and production: missing env vars, different Node versions, file system case sensitivity, or build-time vs runtime behavior differences.
Error messages you might see
500 Internal Server ErrorApplication error: a server-side exception has occurred (see the server logs for more information)Why this happens in AI-generated code
Environment differences between local and production
AI-generated code relies on local-only conditions: environment variables in .env.local, specific Node.js versions, or OS-specific file path behavior that doesn't exist in production.
Development mode hides errors
AI tools test code in development mode which has hot reloading, lenient error handling, and skips build optimizations. Production builds minify, tree-shake, and pre-render — exposing hidden issues.
Hardcoded localhost URLs
AI-generated code contains hardcoded http://localhost:3000 URLs for API calls or redirects that work locally but fail when deployed to a different domain.
How to fix it
Test with a production build locally
Run `npm run build && npm start` locally before deploying. This simulates the production environment and catches most issues that development mode hides.
Use relative URLs and environment-based configuration
Replace hardcoded URLs with relative paths or environment variables. Use process.env.NEXT_PUBLIC_APP_URL for absolute URLs that change between environments.
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Frequently asked questions
How do I see production error logs?
Check your hosting platform's logs: Vercel shows function logs in the dashboard, Railway has real-time logs, and Netlify shows deploy and function logs. You can also add error tracking with Sentry or similar tools.
What's the most common cause of this issue?
Missing environment variables in the production environment. Always double-check that every variable in your .env.local is also configured in your hosting provider's settings.
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