Urgent help with python nextjs deploy get 500 status

Hello need to understand what is wrong ) I had some build issues but now it’s ok

But when I make request to api it returns me 500 status I also use on FastAPI side Groq I have added Groq API key to my environment variables and it shows 500 status what can be wrong ? Thanks for response

Also think is necessary to add what i have in vercel.json

{
  "version": 2,
  "builds": [
    {
      "src": "backend/main.py",
      "use": "@vercel/python",
      "config": {
        "maxLambdaSize": "50mb"
      }
    },
    {
      "src": "frontend/package.json",
      "use": "@vercel/next"
    }
  ],
  "routes": [
    {
      "src": "/api/(.*)",
      "dest": "backend/main.py"
    },
    {
      "src": "/(.*)",
      "dest": "frontend/$1"
    }
  ]
}

Please need help with this issue

Looking at your setup, you’ve got a Next.js frontend and a Python FastAPI backend, and those 500 errors on your API requests are most likely coming from how things are configured in vercel.json.

Right now you’re using the legacy Build API (version 2), which has been deprecated, so Vercel isn’t handling your app in the way you’d expect with the more modern setup.

The recommended approach is to split things out and deploy your FastAPI backend and Next.js frontend as two separate Vercel projects.

That gives you clearer separation of concerns and plays much more nicely with Vercel’s current architecture. If you’d rather not do that, another path is to move your Python logic into Next.js API routes (pages/api or app/api) so everything runs inside the Next.js app itself. That would remove the need for a separate Python function setup entirely.

If you want to keep your current structure, you can try updating your vercel.json to something like this:

{
  "functions": {
    "backend/main.py": {
      "runtime": "python3.9"
    }
  },
  "routes": [
    {
      "src": "/api/(.*)",
      "dest": "/backend/main.py"
    },
    {
      "src": "/(.*)",
      "dest": "/frontend/$1"
    }
  ]
}

From there, the best next step for the 500s is to look at your Vercel function logs in the dashboard under the Functions tab; those logs will show you the exact Python traceback causing the error. Also double-check that your FastAPI app is set up for serverless: you’ll want a proper handler entrypoint that Vercel’s Python runtime can call.

Hey! We're running this session next week after our recent announcement of Gel joining the team. Because you had posted about Python, I thought I'd give you a heads up in case you wanted to join us! :D

https://community.vercel.com/t/community-session-vercel-python/29118

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