#500: INTERNAL_SERVER_ERROR

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sonic ermine
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Error running the exported Web Handler: [Error: No fetch event listeners found]

how do I fix this?

static burrowBOT
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Hi @sonic ermine. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base. :wave:

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I can see you're encountering a 500 Internal Server Error with a specific message about fetch event listeners. Based on the knowledge sources provided, there are several potential causes for this type of error in Next.js.

This error message "No fetch event listeners found" appears to be related to how fetch requests are handled in your Next.js application. From the available information, this could be related to a few different issues:

  1. It might be related to how you're handling API routes or server components
  2. It could be related to polyfill conflicts with the native fetch API
  3. There might be issues with your route handlers not returning proper responses

One specific issue identified in the knowledge sources is related to polyfill conflicts. According to a GitHub issue, there can be conflicts when using polyfill libraries like cross-fetch alongside Next.js's native fetch implementation. The polyfill can override the Response object, causing Next.js to fail to recognize the returned response.

To fix this issue, you could try:

  1. Use the native fetch API that Next.js provides instead of third-party fetch libraries. Next.js recommends avoiding libraries like isomorphic-fetch, whatwg-fetch, node-fetch, cross-fetch, or axios as mentioned in Vercel's conformance rules.

  2. Make sure your route handlers always return a Response or NextResponse object. As noted in one of the error messages: "Ensure you return a Response or a NextResponse in all branches of your handler."

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  1. Check if you're using any event listeners for 'unload' or 'beforeunload' events, as these can cause issues with the browser's back-forward cache. Consider using 'pagehide' instead as recommended in Vercel's documentation.

  2. If you're using Next.js 15 or later, be aware that fetch requests are no longer cached by default. You may need to explicitly set caching options as described in the Next.js upgrade guide.

Without more specific details about your code and setup, these are the most likely solutions based on the available information. If the issue persists, you might need to provide more context about your application structure and the specific code that's triggering this error.

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:

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