MALFORMED_REQUEST_HEADER

The MALFORMED_REQUEST_HEADER error signifies that a request made to the server includes a header that is incorrectly formatted or contains invalid data. This could be due to syntax errors, incorrect header field names, or incompatible header values.

400

MALFORMED_REQUEST_HEADER:

Bad Request

Troubleshoot

I'm encountering an error and reviewing the docs at /flg~eyJhbGciOiJIUzI1NiJ9._f7-_v0.H1pbXxc_pwT_uVOl9HPQTOSEJsJVY_sGnFnlG1GD0mM/docs/errors/MALFORMED_REQUEST_HEADER 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 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. Inspect request headers: Review the headers in your request. Ensure that they are correctly formatted and adhere to the HTTP standard
  2. Validate UTF-8 encoding: Confirm that all request headers, especially cookie values, are valid UTF-8 strings. Non-UTF-8 characters in headers, particularly in the cookie header, often cause this error
  3. Examine Vercel Function behavior: Since this error is specific to Vercel functions, verify the functionality and responses of your Vercel functions. Ensure they are correctly handling request headers and not contributing to malformed responses

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