# Build Error (BUILD_ERROR)

There was an error building your project. The gateway returns this error when
the project fails to compile during deployment.

## Common causes

- **TypeScript errors** - Type mismatches, missing type definitions, or invalid
  TypeScript syntax prevent the project from compiling.
- **Missing imports** - A module or package referenced in the code is not
  installed or does not exist.
- **Invalid route configuration** - The `routes.oas.json` file contains syntax
  errors or references policies or handlers that do not exist.
- **Incompatible dependencies** - A package dependency has version conflicts or
  is not compatible with the Zuplo runtime.

## How to access build logs

1. Open the Zuplo portal and navigate to the project.
2. Check the deployment logs for detailed error messages and stack traces.
3. For local development, run the build locally to see the full error output.

## How to fix

1. Read the error message carefully. Build errors typically include the file
   name, line number, and a description of the issue.
2. Fix any TypeScript compilation errors by checking types and imports.
3. Verify that all referenced modules are listed in `package.json` and properly
   installed.
4. Validate the `routes.oas.json` file to ensure all handler and policy
   references are correct.

:::tip

Run builds locally before deploying to catch errors early. See
[Local Development](../articles/local-development.mdx) for setup instructions.

:::

## Related resources

- [Local Development](../articles/local-development.mdx)
- [Local Development Troubleshooting](../articles/local-development-troubleshooting.mdx)