How to Fix Next.js Middleware Error in AI-Built Apps
Next.js middleware throws errors or doesn't execute as expected. AI-generated middleware often uses Node.js APIs unavailable in the Edge runtime or is placed in the wrong directory.
Error messages you might see
Error: middleware must be placed in the root directory (src/middleware.ts)Dynamic Code Evaluation (e.g. 'eval', 'new Function') not allowed in Edge RuntimeWhy this happens in AI-generated code
Middleware in wrong location
AI places middleware.ts inside app/ or pages/ instead of the project root (or src/ root).
Using Node.js APIs in Edge Runtime
AI imports fs, path, crypto, or other Node.js modules that aren't available in the Edge runtime.
Infinite redirect loops
Middleware redirects to a path that also triggers the middleware, creating an infinite loop.
How to fix it
Place middleware in the correct location
Put `middleware.ts` in your project root or `src/` directory, at the same level as `app/` or `pages/`.
Use Edge-compatible APIs only
Replace Node.js crypto with `crypto.subtle`, avoid `fs` and `path`. Use the `matcher` config to limit which routes trigger middleware.
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Frequently asked questions
Can I use npm packages in middleware?
Only packages that don't rely on Node.js-specific APIs. Check if the package supports Edge runtime before importing.
How do I debug Next.js middleware?
Use `console.log` in middleware and check the terminal output. Middleware runs on the server, not in the browser DevTools.
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