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MIDDLEWARE_RUNTIME_DEPRECATED

Last updated February 9, 2026

The MIDDLEWARE_RUNTIME_DEPRECATED error occurs when a middleware is using a deprecated runtime. This error can occur when a middleware is using a runtime that is no longer supported by the platform.

503

MIDDLEWARE_RUNTIME_DEPRECATED:

Middleware Runtime Deprecated

Troubleshoot

AI Assistance

I'm encountering an error and reviewing the docs at https://vercel.com/docs/errors/MIDDLEWARE_RUNTIME_DEPRECATED.md to understand what's happening. Please help me resolve this by: 1. **Suggest the fix**: Analyze my codebase context and propose what needs to be changed to resolve this error. If you do not have access to my codebase, ask me for the codebase and try to fix the error based on the information you have. 2. **Explain the root cause**: Break down why this error occurred: - What was the code actually doing vs. what it needed to do? - What conditions triggered this specific error? - What misconception or oversight led to this? 3. **Teach the concept**: Help me understand the underlying principle: - Why does this error exist and what is it protecting me from? - What's the correct mental model for this concept? - How does this fit into the broader framework/language design? 4. **Show warning signs**: Help me recognize this pattern in the future: - What should I look out for that might cause this again? - Are there similar mistakes I might make in related scenarios? - What code smells or patterns indicate this issue? 5. **Discuss alternatives**: Explain if there are different valid approaches and their trade-offs My goal is to fix the immediate issue while building lasting understanding so I can avoid and resolve similar errors independently in the future.

To troubleshoot this error, follow these steps:

  1. Identify the affected project: Use Vercel Logs to identify if your project is experiencing this error. Look for the MIDDLEWARE_RUNTIME_DEPRECATED error in your project's runtime logs.
  2. Locate the middleware: Once you've identified the project, check if it has a middleware.js or middleware.ts file in the root directory or uses Routing Middleware in any way.
  3. Redeploy the project: Redeploy the project to automatically upgrade to the latest supported runtime version. However, if the redeploy fails, you may need to:
    • Update your Node.js version: Check your project's Node.js version setting in the Vercel dashboard or package.json and update it to a supported version
    • Update dependencies: Outdated dependencies may not be compatible with newer Node.js versions. Update your package.json dependencies to their latest compatible versions before redeploying

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