Fixing Your Cursor App: Works Locally But Not in Production

You've just spent a few evenings with Cursor, crafting what feels like a genuinely innovative application. It runs beautifully on localhost:3000, the UI is slick, and the backend hums along. You're ready to share it with the world. Then, the inevitable happens: you deploy, and your Cursor app works locally but not in production. This isn't a unique problem; it's a rite of passage for many AI-generated apps that move from local sandbox to live server. The gap between 'working on my machine' and 'accessible via a URL' is often wider than expected, leading to frustration and wasted time. At Convergex AI, we regularly see these issues with 'vibe coded' applications. The good news is that most of these deployment pitfalls are predictable and fixable. Let's dive into the common culprits and how to resolve them.## The Localhost Labyrinth: Hardcoded URLsOne of the most frequent reasons a Cursor app works locally but not in production is the insidious localhost:3000 reference. When an AI agent generates code, it often defaults to local development URLs for API endpoints, authentication redirects, or asset paths. These work perfectly fine on your machine but break instantly when deployed to a domain like your-app.com.

How to Identify and Fix Hardcoded URLs

Your first step is a thorough audit of your codebase. Search for common local development patterns:

• localhost:, 127.0.0.1:
• http:// (especially when expecting https:// in production)
• Specific local port numbers like 3000, 3001, 8000

Once identified, replace these hardcoded values with dynamic ones. The best practice is to use environment variables for full URLs or, even better, relative paths when possible.

// Bad: Hardcoded localhost URL
// const API_BASE_URL = "http://localhost:3001/api";

// Good: Using an environment variable
const API_BASE_URL = process.env.NEXT_PUBLIC_API_BASE_URL || "/api"; 
// For backend services, ensure it's a full URL via env var
// const AUTH_CALLBACK_URL = process.env.AUTH_CALLBACK_URL;

For frontend calls to your own backend, a relative path like /api is often sufficient, letting the browser handle the base URL. For external services or server-side calls, an environment variable is crucial.## The Silent Killer: Missing Environment VariablesWhen your Cursor app works locally but not in production, missing environment variables are almost certainly a factor. On your local machine, your app happily reads from .env files. Production servers, however, do not magically pick up these files. Every secret, API key, database connection string, and callback URL needs to be explicitly configured in your deployment environment.

Auditing and Configuring Your Environment Variables

1. Comprehensive Audit: Go through your entire codebase and list every instance where process.env (for Node.js/JavaScript) or its equivalent in other languages is used. This includes API keys, database URLs, authentication secrets, and any other configuration values.

2. Categorize Variables:

   • Public vs. Private: Frontend variables (e.g., NEXT_PUBLIC_... in Next.js) are exposed to the client, while server-side variables must remain secret.
   • Build-time vs. Runtime: Some variables are needed when your app is built (e.g., for static site generation), while others are only needed when the app runs.

3. Update Callbacks and Keys: Ensure all callback URLs for OAuth providers or webhooks are updated from localhost to your production domain. Verify API keys are for the production environment, not development.

4. Configure on Deployment Platform: Every major hosting provider (Vercel, Railway, Render, etc.) offers a secure way to manage environment variables. You must add each audited variable to their respective configuration panels. Never commit .env files to your Git repository.

# Example for Vercel CLI to add environment variables
vercel env add NEXT_PUBLIC_API_BASE_URL "https://api.yourdomain.com" production
vercel env add DATABASE_URL "your_production_database_string" production --sensitive

If you're still struggling with environment variables, or other aspects of deployment, Convergex AI offers specialized services to fix Cursor apps and get them production-ready.## Database Dilemma: SQLite vs. Production-Grade PostgresSQLite is a fantastic database for local development. It's file-based, easy to set up, and requires no external server. This is why AI agents often default to it. However, it is fundamentally unsuitable for most production deployments, especially in serverless or containerized environments where the filesystem is ephemeral or shared across multiple instances. When your Cursor app works locally but not in production, a database mismatch is a prime suspect.

Migrating from SQLite to PostgreSQL

For any application that needs to scale, handle concurrent users, or run reliably in a production environment, you need a robust, external database like PostgreSQL. Here's how to make the switch:

1. Choose a PostgreSQL Provider: Select a managed PostgreSQL service. Popular options include Supabase, Railway Postgres, Render's managed databases, or cloud providers like AWS RDS, Azure Database for PostgreSQL, or Google Cloud SQL.

2. Update Your Database Schema: If you're using an ORM like Prisma, you'll need to update your schema.prisma file to reflect the change in provider.

   // schema.prisma
   datasource db {
     provider = "postgresql" // Change from "sqlite"
     url      = env("DATABASE_URL")
   }
   

3. Migrate Existing Data (If Applicable): If you have valuable data in your local SQLite database, you'll need to export it and import it into your new PostgreSQL instance. This usually involves tools like pgloader or writing a custom script.

4. Update DATABASE_URL: Once your PostgreSQL database is provisioned, you'll receive a connection string. Add this as your DATABASE_URL environment variable in your production deployment settings, just like any other secret.## The Final Frontier: Verifying in a Real EnvironmentIt's one thing to fix the code; it's another to verify that it actually works in a production-like setting. Simply deploying and hoping for the best is a recipe for continued frustration.

Pre-Flight Checks and Post-Deployment Verification

1. Local Build Command: Before even touching your deployment platform, run your build command locally (e.g., npm run build or yarn build). If it fails here, it will definitely fail in production. Address any build errors, TypeScript issues, or linter warnings immediately.

2. Staging Environments: The best practice is to deploy to a staging environment first. This is a replica of your production environment but used solely for testing. It allows you to catch issues without impacting live users.

3. Robust Logging and Monitoring: Ensure your application has proper logging in place. In production, you won't have a local console to check for errors. Integrate with a logging service (e.g., Vercel's built-in logs, Logtail, Sentry) to catch exceptions and monitor performance.

4. Real-World Testing: Once deployed (to staging or production), perform a full round of manual and automated tests. Try out all critical user flows, interact with external APIs, and ensure all features behave as expected with production-like data.

If your Cursor app works locally but not in production after these steps, it often points to a deeper environmental mismatch or a subtle configuration oversight. These are the kinds of challenges we specialize in at Convergex AI.

Don't let deployment woes stop your innovative AI-generated application from reaching users. While Cursor excels at generating prototypes, getting 'vibe coded' apps production-ready often requires expert finishing touches. If you're tired of debugging deployment issues, Convergex AI is here to transform your local-only app into a reliable, live product.