500 Internal Server Error on Vercel: FUNCTION_INVOCATION_FAILED

What it means

Vercel documents FUNCTION_INVOCATION_FAILED, and the related INTERNAL_FUNCTION_INVOCATION_FAILED, as a function invocation that fails. The possible causes it lists are a crashed runtime process (Node.js, Bun, Python and others) and an unhandled rejection or uncaught exception.

How to fix it

1. Read the application logs to find the error behind the invocation. They are under the Logs tab, or at the deployment's host URL under the /_logs path.
2. Review the function code for errors and infinite loops.
3. Wrap the work in a try/catch block so an error produces a response you can log.
4. Verify the function configuration, including its environment variables.
5. If the function calls an external service, check that the service is responding.

// Example: return a response instead of letting the invocation crash
export async function GET() {
  try {
    const data = await loadData();
    return Response.json(data);
  } catch (error) {
    console.error("loadData failed", error);
    return Response.json({ error: "Internal error" }, { status: 500 });
  }
}

What a DeployDoctor scan can check

A scan cannot see an exception that only happens at runtime. It can report two documented configuration causes ahead of time: process.env reads that are missing from .env.example, and server code Vercel cannot run, such as packages that need Node-only APIs in an Edge route.

Sources

• Vercel documentation: FUNCTION_INVOCATION_FAILED
• Vercel documentation: INTERNAL_FUNCTION_INVOCATION_FAILED

Documentation last checked 2026-10-28. Vercel can change its documentation; confirm against the linked pages.